Solid state ionics: advanced concepts and devices
This symposium will focus on functional properties of ionic and mixed ionic-electronic conducting materials with especial emphasis on the interplay between ions and electrons and with a view toward their application in relevant smart and energy devices.
Mass and charge transport properties occurring at the bulk, interface or surface level in ionic or mixed ionic-electronic conducting materials are often controlling the properties of relevant solid state based devices such as solid oxide fuel and electrolysis cells, solid state batteries, permeation membranes, gas sensors or memristors. This symposium will focus on fundamental and applied aspects of Solid State Ionics covering theory, advanced characterization techniques, functional materials and interfaces as well as novel methodologies for the implementation of innovative concepts into enhanced devices. Moreover, the symposium will cover recent interest in ion-assisted phenomena that give rise to new families of fascinating devices such as all oxide photovoltaic cells or electrostriction-based transducers.
This symposium will provide a forum for extensive discussion and exchange of information among researchers exploring ion-conducting functional oxides in different contexts and diverse applications. This will include state-of-the art methods for structural and chemical characterization such as high resolution transmission electron microscopy, synchrotron-based spectroscopy and diffractometry, scanning probe microscopy and atom probe tomography, just to name a few, combined in many cases with modeling and simulation methodologies such as density functional theory and molecular dynamics. In addition, new methodologies for engineering ionic transport in functional materials will also be one of the main topics under discussion, with special emphasis in heterostructuring, doping and strain. Alternatively, advanced fabrication techniques able to define enhanced materials by design at the macroscale, such as 3D printing or ex-solution decoration, will be covered. Electrolysis, switching phenomena, photocatalysis, gas sensing, and solid state devices for energy and informatics (batteries, solid oxide fuel cells, memristors) will be some of the main applications and devices to be discussed.
Hot topics to be covered by the symposium:
Papers are solicited on (but not limited to) the following topics:
- Defect chemistry in functional oxides
- Nanoionics: mass and charge transport in the nanoscale
- Ion-assisted phenomena including iontronics, ferroelectrics, etc
- Methodologies for engineering ionic transport in functional materials
- Advanced structural characterization tools
- Advanced techniques for in situ/ in operando characterization of solid state ionics materials and devices
- Mass transport in bulk materials for solid state devices
- Solid State Ionics applied to energy devices: solid oxide cells, solid state batteries, permeation membranes, all oxide photovoltaics, oxide thermoelectrics, etc
- Solid State Ionics applied to smart devices: memristors, gas sensors, transducers, etc
- Thin film based solid state devices
List of invited speakers:
- John T. S. Irvine University of St Andrews, UK
- Rotraut Merkle, Max Planck Institute, Germany
- Mauro Pasta, University of Oxford, UK
- Jeff Sakamoto, University of Michigan, USA
- Vincenzo Esposito, DTU, DK
- Regina Dittmann, Forschungszentrum Jülich GmbH, Germany
- Mark Huijben, University of Twente, The Netherlands
- Andreas Klein, Technische Universität Darmstadt, Germany
- Mónica Burriel, CNRS-INP, France
- Sandrine Ricote, Colorado School of Mines, USA
- Felix Gunkel, Forschungszentrum Jülich GmbH, Germany
- David Mebane, West Virginia University, USA
- Sam Copper, Imperial College, UK
- George Harrington, Kyushu University, Japan
List of scientific committee members:
- Stephen Skinner, Imperial College London, UK
- Joachim Maier, Max Planck Institute for Solid State Research, Germany
- Igor Lubomirsky, Weizmann Institute, Israel
- Juergen Fleig, T.U. Wien, Austria
- Werner Sitte, Graz University of Technology, Austria
- Scott Barnett, Northwestern University, USA
- Susanne Hoffmann-Eifert, FZ-Juelich, Germany
- Harry L. Tuller, Massachusetts Institute of Technology, Cambridge, USA
- Zonping Shao, Nanjing University of Technology, China
- Jennifer Rupp, ETHZ, Switzerland and MIT, USA
- Tatsumi Ishihara, Kyushu University, Fukuoka, Japan
- Jose Santiso, ICN2, Barcelona, Spain
Selected papers will be published in a special issue of the journal Solid State Ionics (Elsevier Ltd.). Accepted papers will appear online immediately (with doi and page numbers) and subsequently be compiled in an online special issue. Submission open from May 1 until July 17. Attendance to the meeting is mandatory for the papers to be published.
The journal Solid State Ionics (Elsevier Ltd.) has agreed to sponsor the poster awards.
- 1st prize: 250 euros,
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|09:00||Presentation of the symposium|
Solid State Energy Devices (I): Solid Oxide Cells : Nicola Perry
Authors : John TS Irvine
Affiliations : University of St Andrews
Resume : Understanding and controlling the processes occurring at electrode/electrolyte interface are key factors in optimising fuel cells and electrolysers. Metal particles supported on oxide surfaces promote many of the reactions and processes that underpin the global chemical industry and are key to many emergent clean energy technologies. At present, particles are generally prepared by deposition or assembly methods which, although versatile, usually offer limited control over several key particle characteristics, including size, coverage, and especially metal-surface linkage. In a new approach, metal particles are grown directly from the oxide support though in situ redox exsolution. We demonstrate that by understanding and manipulating the surface chemistry of an oxide support with adequately designed bulk (non)stoichiometry, one can control the size, distribution and surface coverage of produced particles. We also reveal that exsolved particles are generally epitaxially socketed in the parent perovskite which appears to be the underlying origin of their remarkable stability, including unique resistance of Ni particles to agglomeration and to hydrocarbon coking, whilst retaining catalytic activity. Here we highlight recent work on electrochemical generation of nanoparticles in situ in solid oxide cells, the application of exolved particles on perovskite substrates in OER alkali fuel cells and the incorporation and exsolution of PGM nanoparticles from titanate perovskites.
Authors : Ji Wu,Jonathan Skelton,Stephen C. Parker
Affiliations : Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK;Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK;Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
Resume : The creation of socketed metal nano-particle through dopant exsolution from complex perovskite oxides has attracted significant interests over the past few years in the field of solid state ionics. Compared to deposited metal nano-particles, these exsoluted nano-particles retain good catalysis performances but are more resilient towards coking and delamination/agglomeration during cycling. Thus, these durable exsoluted nano-particles have many promising applications, like in chemical looping devices and anodes of solid oxide fuel/electrolyser cells (SOCs). Despite its great application potential, the mechanism behind the nano-particle exsolution process is not yet clear. Earlier theoretical efforts have shown that the migration of the transition metal dopants towards the perovskite surface are thermodynamically favourable. However, these findings cannot explain the highly reducing condition (5% H2/Ar mixed gas) and high temperature (above 950 degree Celsius) required to activate the exsolution process in experiments. In this work, atomistic simulation methods were applied to two typical perovskite systems, (La, Sr)1-x(Ni, Ti)O3-d and (La, Ca)1-x(Ni, Ti)O3-d, to study the kinetics of the metal cation migration during exsolution. We have shown that the metal cation hopping barrier between sites is too high in perovskites without A-site deficiency, but the introduction of A-site deficiency greatly reduces this barrier and makes cation migration viable under reported experimental conditions. Our findings reveal the critical role of A-site deficiency in the nano-particle exsolution process from oxide, and provide insights for future materials optimisation to utilize this exsolution process better.
Authors : Clement Nicollet, Cigdem Toparli, George Harrington, Thomas Defferriere, Bilge Yildiz, Harry L. Tuller
Affiliations : Massachusetts Institute of Technology, 77 Massachusetts Av, 02139 Cambridge, MA, USA
Resume : In Solid Oxide Fuel Cells, oxygen electrode polarization related to electrochemical reactions at the gas/solid interface is often the dominant flux limiting mechanism. Accumulating surface impurities are well known to lead to a reduction in long term durability. On the contrary, surface modification with selected metal oxides can also have a positive effect on the oxygen surface exchange rate. As there is no clear understanding as to why some elements poison oxide surfaces while others enhance their oxygen exchange kinetics, defining a general descriptor is highly desirable, and is the goal of this work. The study uses Pr-doped ceria (PCO) as a model mixed ionic and electronic conductor with a high electrocatalytic activity toward the oxygen reduction reaction. PCO specimens were infiltrated with a variety of binary oxides and their surface exchange kinetics were evaluated by analysis of electrical conductivity relaxation measurements. By comparing the evolution of the surface exchange kinetics with different infiltrated oxides, it is possible to define a descriptor that allows one, on the one hand, to predict what will be the effect of a given oxide on the surface exchange kinetics, and on the other hand to tune the surface exchange coefficient over 7 orders of magnitude with great precision. Through this new insight, it was possible to enhance the surface exchange coefficient by 500 times the initial values, illustrating the power of this new descriptor.
Solid State Energy Devices (II): Batteries : Ainara Aguadero
Authors : Jeff Sakamoto123, Michael Wang2, Marie-Claude Bay4, Michael Wang2 and Corsin Battagia4
Affiliations : 1 Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA; 2 Department of Material Science and Engineering, University of Michigan, Ann Arbor, MI, USA; 3 Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA; 4 Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
Resume : There is tremendous interest in making the next super battery, but state-of-the-art Li-ion technology works well and has inertia in several commercial markets. Supplanting Li-ion will be difficult. Recent material breakthroughs in Li and Na metal solid-state electrolytes could enable a new class of non-combustible solid-state batteries (SSB) delivering twice the energy density (1,200 Wh/L) compared to Li-ion. However, technological and manufacturing challenges remain. The discussion will consist of recent milestones and attempts to bridge knowledge gaps to include: • The physical and mechano-electrochemical phenomena that affect the stability and kinetics of the Li and Na metal-solid electrolyte interface • Thin film processing and Li integration with LLZO • Plating and stripping dynamics of Li and Na metal Despite the challenges, SSB technology is rapidly progressing. Multi-disciplinary research in the fields of materials science, solid-state electrochemistry, and solid-state mechanics will play an important role in determining if SSB will make the lab-to-market transition.
Authors : Gutiérrez-Pardo, A.* (1), Aguesse, F. (1), Fernández-Carretero, F. (2), Siriwardana, A. (2) García-Luis, A. (2)., Llordés, A. (1)
Affiliations : 1) Centro de Investigación Cooperativa de Energías Alternativas (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Parque Tecnológico de Alava, Albert Einstein 48, 01510 Vitoria-Gasteiz, Spain; (2) TECNALIA, Parque Científico y Tecnológico de Gipuzkoa, E-20009 San Sebastián-Donostia, Spain.
Resume : Solid state batteries (SSB) are expected to outperform the current Li-ion technology as they can solve safety hazards, avoiding the use of flammable liquid organic electrolytes. Lithium metal anode has demonstrated to be the best alternative to achieve higher energy densities in SSB up to date. However, some solid electrolytes such as ceramic materials present unfavorable properties such as brittleness, leading to a possible mechanical fracture upon cycling. Moreover, a poor contact at the rigid solid-solid interfaces between the electrodes and the electrolyte leads to higher interfacial resistances. It is possible to improve this interfacial contact by adding a soft interlayer that enables homogeneous metallic electrodeposition during battery cycling. In this work, a solvent-free method has been used to obtain layers of a soft material which can be deposited on the surface of either the electrode or the electrolyte of a solid-state Li-ion battery. An organic plastic crystal, heated above its melting point, has been deposited on the surface of the electrode by spin coating technique, preventing the problems of metallic lithium with organic solvents. At room temperature, a solid and homogeneous soft layer is obtained, and a ceramic has been used as solid electrolyte for the cells. An increase in conductivity and a considerably decrease of area specific resistance have been obtained, which is critical for the development of stable and efficient devices for the industry.
Authors : Zonghao Shen(a), Chao Xu(b), Clare Grey(b), Ainara Aguadero(a)
Affiliations : (a) Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom (b) Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
Resume : Research into lithium ion batteries (LIBs) for electric vehicles has been accelerated in the last decades. To enhance the performance and safety of LIBs, it is essential to understand the degradation processes occurring both within the electrode materials, as well as at the electrodes/electrolyte interfaces. For the Ni-rich layered materials functioning as the cathode in LIBs, in this work LiNi0.8Co0.1Mn0.1O2 (NCM811), the high capacity and low cost make it a promising candidate for high-energy batteries while its poor thermal and chemical stability, unsatisfying cycling behavior, and sensitivity to ambient moisture hinder its further applications. Considerable attempts have been performed on improving the performance of the Ni-rich cathode. Meanwhile, preliminary degradation studies have also been carried out: intragranular cracks , phase transition with oxygen evolution  etc. have been reported. However, the local chemical degradation processes on the utmost surface, at interfaces and in the bulk materials are yet to be fully unfolded. In this work, in order to determine the roles of elements in the degradation processes of the cathode materials, chemical analysis techniques including isotopic labelling are performed for bulk materials and thin films. Additionally, Secondary Ion Mass Spectrometry (SIMS), combined with other surface-sensitive techniques, Low Energy Ion Scattering (LEIS), X-ray Photoelectrons Spectrum (XPS) etc., is applied for obtaining information about the cation inter-diffusion etc. chemical degradation processes, for post-mortem and in operando analysis. Acknowledgements This work was carried out with funding from the Faraday Institution (faraday.ac.uk), grant number EP/S003053/1, as part of the Degradation of Battery Materials project. Reference  Z. Xu et al., J. Mater. Chem. A, 6 (2018) 21859  R. Jung et al., J. Electrochem. Soc., 164(7) (2017) A1361
Authors : Markus Joos, Christian Schneider, Andreas Münchinger, Robert Usiskin, Bettina Lotsch, Joachim Maier
Affiliations : Markus Joos; Christian Schneider; Andreas Münchinger; Robert Usiskin; Bettina Lotsch; Joachim Maier; Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart Christian Schneider; Bettina Lotsch; Ludwig-Maximilians-Universität München (LMU), Butenandstr. 5-13 (Haus D), D-81377 München
Resume : Hydration can have profound effects on the defect chemistry and transport properties of ion conductors. Here we investigate hydration of the layered Li conductor Li2Sn2S5, which consists of covalently-bonded (Li,Sn)S2 layers and Li cations located between the layers. By varying the surrounding humidity, the water content of Li2Sn2S5 · x H2O can be readily and reversibly varied over the range x = 0 to 10.5. The water intercalates between the layers, increasing the interlayer distance from 6.2 Å for the anhydrous material up to 11.0 Å for Li2Sn2S5 ⋅ 10.5 H2O. A first-order phase transition is seen between x = 0 and about 2.5 by both thermogravimetry and x-ray diffraction, consistent with intercalation of the first monolayer of water. Impedance spectroscopy and pulsed-field gradient nuclear magnetic resonance reveal that the predominantly two-dimensional Li transport increases dramatically upon hydration. The fully hydrated compound remains solid, but reaches liquid-like values of 10-2 S/cm for the Li conductivity and 10-7 cm2/s for the Li self-diffusivity at 25 °C. These results provide an interesting example of a sulfide electrolyte system where humidity is both tolerated and highly beneficial.
Authors : Korte, C*. (1), Schleutker, M. (1), Wekking, T. (1) & Tsai, C.-L. (2)
Affiliations : (1) Forschungszentrum Jülich, Institute for Energy and Climate Research (IEK-14), Germany (2) Forschungszentrum Jülich, Institute for Energy and Climate Research (IEK-1), Germany
Resume : In a Li-S cell a Li+ solid electrolyte membrane, separating anode from cathodic compartment, could prevent the diffusion of polysulfide species to the anode. In a Li-O2 cell it allows the use of a non-aqueous, aprotic anolyte and an aqueous, protic catholyte. When using metallic lithium anodes, short circuits by dendrite grow can be avoided. There are only few studies on the ion transfer kinetic across the solid/liquid electrolyte interface. In this study the kinetics of the Li+ transfer between a solid electrolyte Li7La3Zr1.6Ta0.4O12 and a liquid electrolyte LiPF6+EC/DMC is investigated, c(Li+) = 0.001-1 mol/l. A symmetric liquid/solid/liquid DC polarisation cell with 6 potential probes and 2 current loaded Li electrodes has been used to measure the potential drops at the solid liquid interfaces. The symmetric S-shaped polarization curves can be described by a thermally activated transfer kinetics (Ea ~0.3 eV) and a constant ohmic resistance which can be attributed to a low conducting surface layer (Ea ~1.1 eV). At low c(Li+) < 0.1 mol/l the polarisation resistance RP depends on c(Li+) and obeys a power law. At higher c(Li+) > 0.1 mol/l RP reaches a constant plateau of ~600 Ω cm². The thermally activated Butler-Volmer like transfer process yields an exchange current density i0 of ~400 µA/cm2 and a symmetry factor α of ~0.4 (1 mol/l LiPF6). Only at very low Li+ concentrations <0.01 mol/l the polarization curves show a strong asymmetry, due to mass transport limitations.
Interface & Surface Phenomena (I) : Harry Tuller
Authors : F. Gunkel, C. Baeumer, M. L. Weber, M. Andrae, M. Rose
Affiliations : Peter Gruenberg Institute 7 (PGI-7), Institute of Energy and Climate Research (IEK-1), RWTH Aachen University
Resume : Epitaxial oxide thin films allow combining the properties of complex oxides on the nanoscale in atomically defined manner. This enables us to play with electronic band structure and charge transfer at interfaces and surfaces of oxides, reflecting an additional degree freedom to control and manipulate their magnetic, electronic, and ionic properties. In complex oxides, the charge transfer associated with the electronic band alignment at interfaces can have both ionic and electronic contributions, making the understanding of charge-transfer phenomena complex. At the same time, the additional complexity arising from mixed ionic-electronic space charges can be very useful to tailor properties on the nanoscale. Here, we first discuss in a general manner the origin of space charges and defect structure at interfaces of complex oxides. We then discuss different examples of solid-solid oxide interfaces,  solid oxide-gas interfaces , and solid oxide-liquid interfaces. In the second part, special focus will be set on tailored oxide heterostructures employed for electrochemical water splitting in alkaline media, where we discuss strategies to tune catalytic activity and stability of tailored model catalysts, using an atomically defined epitaxy approach and space charge engineering.   Gunkel et al., Phys. Rev. B 93, 245431 (2016)  Andrae et al., Phys. Rev. Mater., 3, 044604 (2019)  M. L. Weber, F. Gunkel, JPhys Energy 3, 031001 (2019)  M. L. Weber et al., Chem. of Mater., 31, 2337 (2019)
Authors : F. Baiutti (1), F. Chiabrera (1), M. Acosta (2), J. Sirvent (1), J. MacManus-Driscoll (2), A. Tarancon (1, 3)
Affiliations : (1) Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy, 1 Jardins de les Dones de Negre, Barcelona 08930, Spain; (2) Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom; (3) ICREA, 23 Passeig Lluís Companys, Barcelona 08010, Spain.
Resume : The search for enhanced solid-gas reaction kinetics is key in high-temperature energy materials, which find application in devices such as reversible micro solid oxide cells. In the present contribution, we show novel examples on the utilization of nanoionics effects for the development of next-generation electrodes. A series of grain boundary-dominated columnar structures, based on mixed ionic-electronic conductors, have been fabricated by Pulsed Laser Deposition and analyzed in order to assess the impact of the local structure on the functionalities. It is observed that, by an appropriate tuning of the local chemistry, one can achieve a strong improvement of the oxygen reduction reaction kinetics, together with superior thermal stability owing to the suppression of surface dopant segregation. We will give practical demonstration on how this can be obtained, for example, as a consequence of the nanoscale alternation of fluorite and perovskite phases (vertically aligned nanostructures) in Sr-doped lanthanum manganite: Here, a reduction of more than one order of magnitude in the area specific resistance is observed with respect to the single phase material, while high-temperature isotherm treatments (100 hrs at 700 C) highlight virtually no degradation. The findings are rationalized by using state-of-the-art structural and functional techniques.
Authors : K.N.S. Schuldt, H. Ding, B. Huang, J. Koruza, C. Castro-Chavarria, M. Maglione, and A. Klein
Affiliations : Department of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany; Department of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany; Department of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany; Department of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany; Institut de Chimie de la Matière Condensée de Bordeaux, Université de Bordeaux, UPR-CNRS 9048, Avenue du Docteur Schweitzer 87, F-33600 Pessac, France; Institut de Chimie de la Matière Condensée de Bordeaux, Université de Bordeaux, UPR-CNRS 9048, Avenue du Docteur Schweitzer 87, F-33600 Pessac, France; Department of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany
Resume : A major restriction of multi-layer ceramic capacitors is the increasing leakage current as a result of a decreasing insulation resistance, which is supposed to be based on the electromigration of oxygen vacancies (VO˙˙) accompanied by an O2-exchange at the electrode interfaces. The O2-exchange is affected by the space charge region, which is determined by the difference in Fermi energy at the interface and in the bulk. This can be manipulated by doping and varying the electrode material, which should enable systematic tuning of the O2-exchange and accordingly resistance degradation. Therefore, we analyzed the barrier formation of Mn/Fe doped BTO ceramics to different high and low work function electrodes as a function of doping and VO˙˙ concentration using X-ray photoelectron spectroscopy. Different VO˙˙ concentrations were established by reducing and oxidizing treatments. The chosen doping concentrations of 3.2x10^19 to 4.0x10^20 cm-3 were supposed to be sufficiently high to pin the Fermi level at the specific defect level states. However, the experiments reveal no lower Fermi energy than 1.7 eV above the valence band maximum, which strongly contrasts with defect chemistry calculations, which predict a Fermi energy of approx. 1 eV for oxidized acceptor doped BTO. Furthermore, no pinning was observed at the known defect levels (in the accessible range). These results reveal a significant discrepancy in Fermi level position between defect chemistry calculations and experiment.
Authors : Francesco Ciucci (a, b)
Affiliations : (a) The Hong Kong University of Science and Technology, Mechanical and Aerospace Engineering, Clearwater Bay, Kowloon, Hong Kong, China SAR (b) The Hong Kong University of Science and Technology, Chemical and Biological Engineering, Clearwater Bay, Kowloon, Hong Kong, China SAR
Resume : Highly efficient and environment-friendly devices for energy transformation are in urgent demand for the sustainable production of power. Solid oxide fuel cells (SOFCs) are among the most efficient systems that can convert chemical energy directly into electricity. Currently, Ni/yttria-stabilized ZrO2 (YSZ) is the state-of-the-art SOFC anode material (or the cathode material of solid oxide electrolysis cells), due to its relatively high mechanical strength, high performance, and low cost. However, the Ni/YSZ anode still has several limitations including Ni agglomeration at high temperature, sulfur poison, and carbon coking. While perovskite-type materials have been used as SOFC anodes to overcome many of these challenges, their catalytic activity is typically poor. Recently, Nonstoichiometric perovskites with active metal nanoparticles exsolved on the surface have drawn great research interest because of the potential enhancement in electrochemical activity. However, the catalytic activity delivered by A-site deficient perovskites with exsolved nanoparticles is still not comparable to that of state-of-the-art SOFC anode materials. There are still many opportunities for materials development and improvement. In this work, we report a novel Sc-based A-site deficient perovskite material La0.4Sr0.4Sc0.9Ni0.1O3-δ (LSSN) as a highly active anode for intermediate-temperature solid oxide fuel cells . The material is designed using both thermodynamical analysis and ab-initio simulations. The drop in Gibbs free energy for Ni in H2 is substantial in comparison to the other elements, and density functional theory simulations indicate that the segregation of Ni towards the surface is energetically favored. Spherical Ni nanoparticles with well-defined boundaries are exsolved on the surface of LSSN after reduction in hydrogen, and the reduced samples show a high electrochemical catalytic activity in symmetric-cell measurements with an area-specific resistance as low as 0.055 Ω cm2 at 800 °C in humid H2. Insights into the exsolution mechanism are also derived from both experiments, analytical modeling, and ab-initio simulations . The mechanistic insights gained here can be broadly applied to design more efficient materials capable of exsolution and to control the nanoparticle growth and coverage. Acknowledgments The author gratefully acknowledges the Research Grants Council of Hong Kong for support through the projects 16207615, 16227016, and 16204517. References  Y. Gao, D. Chen, M. Saccoccio, Z. Lu, F. Ciucci. From material design to mechanism study: Nanoscale Ni exsolution on a highly active A-site deficient anode material for solid oxide fuel cells. Nano Energy, 27. (2016). 499-508.  Y. Gao, Z. Lu, T.L. You, J. Wang, L. Xie, J. He, and F. Ciucci. Energetics of Nanoparticle Exsolution from Perovskite Oxides. Journal of Physical Chemistry Letters, Journal of Physical Chemistry Letters, 9, 13, 3772-3778 (2018)  Y. Gao, J. Wang, Y.Q. Lyu, K.Y. Lam, and F. Ciucci. In-situ Growth of Pt3Ni Nanoparticles on A-site Deficient Perovskite with Enhanced Activity for Oxygen Reduction Reaction. Journal of Materials Chemistry A, 5, 6399-6404 (2017)
Authors : Alexander Bonkowski, Ji Wu, Roger A. De Souza, Stephen C. Parker
Affiliations : Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany; Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK; Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany; Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
Resume : Recent experimental work has demonstrated that catalytically active nanoparticles with enhanced stability can be readily dispersed on a perovskite oxide support through a process of ex-solution. This process produces socketed nanoparticles, which show high activity and are more resistant to catalytic poisoning . One such example is exsolved nickel on lanthanum doped strontium titanate support that can be used for syngas production by methane steam reforming. However, the transport of the dopant and the formation of the metal nanoparticle are still not well understood. We have begun to address this by using a range of atomistic simulation techniques. Potential based molecular dynamics were used to investigate the dynamics of nickel diffusion in lanthanum-doped strontium titanate. While nickel favourably resides on B-sites, A-site deficiency is found to be a key factor in determining the migration barrier and the diffusion rate. We also found evidence of enhanced lanthanum and nickel diffusion, as seen in experiments. However, when larger concentrations of lanthanum dopants are present, lanthanum rich layers form and are predicted to inhibit diffusion. We also investigated the transport at surfaces and found low energy barriers and trapping sites on surface layers. One of the advantages of atomistic simulation is that compositional changes can be easily made, and we illustrate this by exploring the effect of different dopants such as Fe and Mn and the effect of different host lattices by replacing strontium titanate with calcium titanate.
Authors : Christoph Riedl, Alexander Schmid, Andreas Nenning, Stefan Smetaczek, Andreas Limbeck and Juergen Fleig
Affiliations : Institute of Chemical Technologies and Analytics, Getreidemarkt 9, 1060 Vienna, Austria
Resume : In the search for high performance intermediate temperature solid oxide fuel cells (SOFCs), improving the kinetics of oxygen reduction on mixed ionic electronic conducting (MIEC) oxide surface is of great importance. In this study, the effect of surface decoration of La0.6Sr0.4FeO3-δ (LSF64) with platinum nanoparticles was investigated. Symmetrical thin film samples were prepared by pulsed laser deposition of LSF64 on yttria stabilized zirconia single crystals and investigated before and after sputter deposition of tiny amounts of Pt (nominally a few monolayers). Surface composition and morphology was studied using electron microscopy, XPS and inductively coupled plasma mass spectrometry. Impedance spectroscopic measurements reveal that platinum nanoparticles on the surface of LSF64 strongly accelerate the oxygen surface exchange kinetics. At lower oxygen partial pressures a LSF64 polarisation decrease of almost two orders of magnitude was observed. Furthermore, platinum decorated LSF64 electrodes showed slower degradation and less scattering of polarisation resistances. Interestingly, faster oxygen incorporation was observed at lower oxygen partial pressures, which is contrary to undecorated LSF64 samples and indicates a severe mechanism change. We conclude that Pt nanoparticles lead to a job sharing of oxygen dissociation on Pt and rate limiting oxygen incorporation into the oxide, while on free LSF64 surfaces oxygen dissociation seems to be rate limiting.
Authors : Alfonso J. Carrillo, Laura Navarrete, Marwan Laqdiem, María Balaguer, Jose M. Serra
Affiliations : Instituto de Tecnología Química, UPV-CSIC. Av. de los Naranjos s/n, 46022 Valencia, Spain
Resume : Chemical looping reforming of methane coupled with CO2 splitting is a promising technology for syngas production. It consists of 2-steps that rely on the oxygen exchange capacity of metal oxides, such as CeO2. In the first step, CH4 is partially oxidized with CeO2 lattice oxygen, generating H2 and CO. Afterward, CO2 re-oxidizes the oxide, forming CO, closing the loop. Although CeO2 presents remarkable multicycle stability, its surface exchange kinetics are slow, hindering fast syngas production during the partial oxidation of methane. Surface functionalization with metal catalysts, prepared by impregnation, is normally employed to enhance reaction rates. However, the high process temperatures (~900 ºC) can cause nanoparticle sintering, decreasing the catalytic activity. To overcome this issue, the exsolution method has emerged as an alternative. In this process, metallic nanoparticles are created by the diffusion of cations contained in the oxide lattice that migrate to the surface, remaining anchored into the oxide support, minimizing particle agglomeration during prolonged operation. Here, we apply the exsolution method to create stable Ru nanoparticles of 2-5 nm. Catalytic tests show that exsolved Ru nanoparticles boost the fuel production rates, increasing the selectivity towards syngas. TEM analysis confirmed nanoparticle stability after 20 chemical loops, indicating the beneficial effects of exsolution oxide functionalization for high-temperature fuel production.
HARVESTORE sponsored session: In situ/Operando Characterization : Albert Tarancón
Authors : Klaasjan Maas1, Benjamin Meunier,1 G. R. Castro,3,4 J. Rubio-Zuazo,3,4 Laetitia Rapenne,1 Carmen Jimenez,1 Quentin Rafhay,2 Michel Boudard,1 Mónica Burriel1,*
Affiliations : 1Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France 2Univ. Grenoble Alpes, CNRS, IMEP-LAHC, F-38000 Grenoble, France 3Spanish CRG BM25-SpLine Beamline at the ESRF, 71 avenue des Martyrs 38000 Grenoble, France 4Instituto de Ciencia de Materiales de Madrid-ICMM/CSIC, Cantoblanco, E-28049 Madrid, Spain
Resume : The interest to increase the performance of transistor-based data storage technologies is leading to the development of new types of memory architectures. In particular, two-terminal memristive devices based on a valence change mechanism are now considered as potential candidates for both long-term memory storage (ReRAM) and brain-like computing (artificial synapses). The present work focuses on the study and understanding of the memristive mechanisms of Ti/La2NiO4+δ/Pt heterostructures. The electrical characteristics of the samples showed a continuous change in resistance, giving rise to multilevel programming capabilities, and revealed the key role played by the oxygen content of the films on the initial resistance and on the operation window. In order to get a better insight in the microscopic mechanisms responsible for the resistance change specific Pt/ La2NiO4+δ /Ti devices were prepared for Synchrotron experiments. By acquiring XRD patterns in selected regions of interest we could confirm the important oxygen scavenging capability of Ti, which resulted in a decrease in the c lattice parameter of the La2NiO4+δ film (decrease in O content) underneath the Ti electrode. Furthermore, by operando HAXPES and XANES spectroscopic measurements we were able to locate the observed voltage drop by the energy shift of the La 2p3/2 in different regions and to directly observe the oxidation and reduction of the Ni cation upon bias application of different polarity.
Authors : Catalina Jiménez(a), M. Arce(a,b), Mariano Santaya(b), Emilia A. Carbonio(a,c), Raul Garcia-Diez (a), H Troiani(b), R. Gotesmann (a), R.G. Wilks(a), Axel Knop-Gericke(c,d), Marcus Bär(a,e,f), Liliana Mogni(b)
Affiliations : (a) Helmholtz-Zentrum Berlin, Renewable Energy, BESSY II, Albert-Einstein-Str.15, 12489, Berlin, Germany; (b) INN-CNEA-CONICET, Centro Atómico Bariloche, Av. Bustillo 9500, S. C. de Bariloche, Rio Negro, 8400, Argentina; (c) Fritz-Haber Institute, Dept. of Inorganic Chemistry, Faradayweg 4, 14195 Berlin, Germany; (d) MPI for Chemical Energy Conversion, Stiftstrasse 34 – 36, 45470 Mülheim an der Ruhr, Germany; (e) Friedrich Alexander Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany; (f) Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (HI ERN), Albert-Einstein.Str. 15, 12489 Berlin, Germany
Resume : Among the sustainable energy sources, solid oxide fuel cells (SOFC) are key technology for decentralized power generation due to its high efficiency in converting electrical energy from chemical fuels. Massive commercialization requires fuel flexibility and lower operation temperatures (< 700°C) to reduce costs and mitigate degradation phenomena. Inherent drawbacks on electrodes are: poisoning, C deposits, and increased activation overpotentials. Tackling these issues entails engineering new intermediate temperature SOFC (IT-SOFC) materials. Sr(Ti,Fe)O3-d (STF) is a mixed ionic electronic-conductor perovskite capable to work both as cathode and anode. Ni-doped STF (STFN) exsolves Fe-Ni nanoparticles (NPs) in reducing atmosphere. NP exsolution boosts the performance of these IT-SOFC anodes by enhancing the H2 dissociative adsorption, reducing the anode polarization resistance and improving C tolerance. We combined ambient pressure X-ray photoelectron spectroscopy and electron-yield absorption spectroscopies (AP-XPS/XAS) with electrochemical impedance spectroscopy and electrode polarization to gain device-level insights at the gas/solid interface of electrolyte-supported model cells under operando conditions. We characterized the surface chemistry of the STF and STFN electrodes in reducing and oxidizing atmospheres at the device operation temperatures (~700°C) to correlate NP exsolution and electrode polarization resistance as key indicator of electrochemical cell performance.
Authors : Yunqing Tang(a)*, Francesco Chiabrera(a), Nerea Alayo(a), Alex Morata(a), Albert Tarancón(a,b)
Affiliations : (a)Department of Advanced Materials for Energy Applications, Catalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1, 08930 Sant Adrià del Besòs, Barcelona, Spain; (b)ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain
Resume : Mixed ionic and electronic conductor thin films offer an ideal platform for the study of oxygen mass transport mechanisms, which play a crucial role in many energy and information technologies, such as solid oxide fuel cells (SOFCs) and non-volatile resistive memory devices. For these applications, the knowledge of the point defect concentration is needed to tailor the oxides’ functional properties. Nevertheless, traditional methods used in bulk materials present many challenges in thin films’ form since the small masses and volumes lower the sensitivity of the measurements. The objective of present work is to investigate the defect chemistry in La1-xSrxFeO3-δ (LSF) thin films as a function of equivalent oxygen partial pressure, temperature and Sr concentration by in-situ ellipsometry measurements. LSF thin films were deposited on YSZ (001) substrate by Pulsed Laser Deposition. The oxygen chemical potential of LSF was progressively varied by applying a voltage bias between the thin film and the counter-back electrode, while recording the ellipsometry spectra. The results show that it is possible to track the evolution of the point defect concentration in the LSF thin films by measuring the variation of the low energy (∼1 eV) optical transition. Moreover, this method offers new insights into the effect of the point defect concentration on the material’s electronic structure and on the phenomena involved in the reduction and oxidation of LSF thin films.
Authors : Zijie Sha, Stephen J. Skinner
Affiliations : Department of Materials, Exhibition Road, Imperial College London, London, SW7 2AZ, UK
Resume : In the development of high temperature electrochemical devices such as solid oxide fuel cells (SOFCs) and oxygen transport membranes (OTMs), solid-state (ceramic) technologies have proven to be particularly promising, for example in mixed ionic and electronic conducting (MIEC) perovskite electrodes. Previous studies have focussed on material behaviour under pure oxygen conditions, while recently it has been suggested that components of air such as humid vapour may modify the materials’ chemistry under device operating conditions and affect long-term durability [1-2]. Study of the oxygen diffusion behaviour of MIEC perovskites and the gas-solid interface under different model atmospheres is vital as such SOFC or OTM technology approaches market viability. We have studied the surface exchange and oxygen ion diffusion behaviour of (La0.8Sr0.2)0.95Cr0.5Fe0.5O3-δ (LSCrF8255) perovskites in humid conditions from 600 to 900 °C under various oxygen partial pressures (0 and 200 mbar) with a constant water vapour pressure of 30 mbar through Isotopic Exchange Depth Profiling – Secondary Ion Mass Spectrometry (IEDP-SIMS). We have observed significantly enhanced bulk diffusion under the pure water conditions (pO2 = 0 mbar, pH2O = 30 mbar) compared to the dry oxygen (pO2 = 200 mbar, pH2O = 0 mbar) and the humidified oxygen (pO2 = 200 mbar, pH2O = 30 mbar) conditions. This is likely due to the higher concentration of oxygen vacancies generated in the materials during exchange annealing. The atomic structure of the materials, including oxygen non-stoichiometry, was characterized by neutron diffraction. Our study also demonstrates limited surface exchange between water and the LSCrF phase under humid conditions with high pO2 (pO2 = 200 mbar, pH2O = 30 mbar). This is primarily due to the dominance of the homo-exchange between the humid vapour and the gaseous oxygen molecules at high temperatures, as observed through in-situ residual gas analysis (RGA) carried out during wet oxygen isotopic exchange. In addition to the study of transport properties, we have investigated the effect of atmosphere on the stability of the surfaces of the LSCrF8255 material using angle-resolved X-ray photoelectron spectroscopy (ARXPS), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM), correlating changes in oxygen surface exchange with cation segregation processes to provide a detailed understanding of potential degradation processes in the SOFC or OTM devices under humid conditions. 1. Huang, Y.L., Pellegrinelli, C. and Wachsman, E.D., 2016. Fundamental impact of humidity on SOFC cathode ORR. Journal of The Electrochemical Society, 163(3), pp.F171-F182. 2. Staykov, A., Fukumori, S., Yoshizawa, K., Sato, K., Ishihara, T. and Kilner, J., 2018. Interaction of SrO-terminated SrTiO3 surface with oxygen, carbon dioxide, and water. Journal of Materials Chemistry A, 6(45), pp.22662-22672
Authors : Mogni, L.V. *(1), Santaya, M. (1), Toscani L. (1), Troiani, H.E. (1), Basbus, J.F. (1), Arce M.D. (1,2) Baque L. C. (1) Serquis, A.C. (1) Napolitano, F. R. (1), Ascolani-Yael J. (1), Cuello S. (1), Gamba N. (1), Bär, M. (2), Cuello G.(3), Fernández-Díaz M.T. (3), Alonso J.A. (4), Emilia A. Carbonio (5,6) y a Axel Knop-Gericke(6,7) Jimenez, C.E. (2)
Affiliations : (1)Instituto de Nanociencia y Nanotecnologia CNEA-CONICET, Bariloche, Argentina (2) Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Department Interface Design, Berlin, Germany. (3) Institute Laue Lagevin, Grenoble, France (4) Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Spain (5) Helmholtz-Zentrum Berlin, Research Group Catalysis for Energy, BESSY II, Albert-Einstein-Str.15, 12489, Berlin, Germany (6) Fritz-Haber Institute, Dept. of Inorganic Chemistry, Faradayweg 4, 14195 Berlin, Germany (7) MPI for Chemical Energy Conversion, Stiftstrasse 34 – 36, 45470 Mülheim an der RuhrMülheim an der Ruhr, Germany * lead presenter
Resume : The comprehension of the complex processes taking place at Solid Oxide Fuel Cells (SOFC) materials requires using complementary characterization techniques. In these devices, the ionic/electronic charge transport and the solid-gas electrode reactions depend on the atomic and electronic structures of the electrode surface and electrode/electrolyte's bulk. However, SOFC works at non-ambient conditions, which could induce changes in material structures affecting their performances. Therefore, simultaneous electrical or electrochemical experiments with in-situ studies using neutron or synchrotron radiation techniques are essential to understand the whole phenomena. In this work, we discuss results for both, proton conductor electrolyte and perovskite-based symmetrical electrode materials. In oxides with proton conductivity, O-ion and/or electronic conduction usually co-exist. Thus, in-situ X-ray diffraction combined with Impedance Spectroscopy (IS) and neutron-based techniques were used to elucidate the crystalline structure and validate the temperature range where BaCe0.4Zr0.4Y0.2O3-δ can operate as proton electrolyte. On the other hand, we evaluate the chance of using Ni-doped SrTi0.3Fe0.7O3-d perovskite as anode/cathode by studying the reversibility of reduction-oxidation cycles with the aim to explore electrode regeneration process. We used near ambient synchrotron spectroscopies, electron microscopy and IS aiming to understand the mechanism of surface decoration by nanoparticles exsolution and how it affects the electrode reactions.
Poster Session (I) : Miguel A. Laguna-Bercero, Jeff Sakamoto
Authors : A. El hat, A. Hadri, C. Nassiri, B. Fares, N. Hassanain, A. Mzerd
Affiliations : University Mohammed V,Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat, Morocco
Resume : SxSn1-xO2 thin films with different S concentration from 0% to 10% deposited by spray pyrolysis technique on glass substrate at 400°C.The films were characterized by structural, surface, optical and electrical properties, respectively. X-ray diffraction analysis shows that the S-doped SnO2 films tetragonal structure and preferential orientation along (110) plane. Scanning electronic microscopy were used to study the films morphology. Optical analysis of the deposited films show an average optical transmittance of 70%–85% in the visible region; meanwhile the band gap value oscillates around 2.58-3.63 eV, with a shift towards higher values when the S concentration is decreased. The Hall effect electrical measurements showed that SnO2 thin films not doped and have an electrical conductivity doped n-type. The best value of the electrical resistivity is of the order of 6.34x10-2 (Ω.cm) obtained in the layer
Authors : Kwang Ho Park, Ji-Seop Shin, Min-Kyeong Jo, Muhammad Saqib, Jun-Young Park
Affiliations : HMC, Department of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05009, Republic of Korea
Resume : Proton ceramic fuel cells (PCFCs) are a electrochemical devices based a ceramic electrolyte that exhibits high protonic conductivity at elevated temperatures. PCFCs have received big attentions as alternatives of oxygen-ion conducting solid oxide fuel cells (SOFCs), because they have high ionic conductivity with low activation of protons, compared to that of SOFCs at intermediate temperatures [1, 2]. Recently, Lee et al. reported that the PCFC with cell size of 5×5 cm2 achieved a power density of 1.3 W‧cm-2 at 600 ℃ by using a Ni-cermet anode-supported cell design with the BaCe0.7Zr0.1Y0.1Yb0.1O3-δ(BCZYYb) electrolyte and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) cathode . However, the BSCF cathode material has limited durability in terms of Sr segregation phenomena and high thermal expansion coefficient (TEC) under PCFC condition. Thus, many researchers try to develop the highly active and stable cathode materials with low activation energy at intermediate temperatures . Usually, cobaltites have good catalytic properties for oxygen reduction reaction. However, TEC of cobaltite-materials is almost twice larger than that of state-of-art BCZYYb electrolyte for PCFCs . Exceptionally, layered cobaltites have low TEC of ~ 10×10-6 K-1 . Hence, in this study, we investigate layered cobaltites as a cathode material to improve thermal stability of PCFCs. In addition, to improve the catalytic property of cathode materials, various metal oxides are doped into layered cobaltites. In addition, doped layered cobaltites are prepared using various synthesis methods such as combustion, citrate-hydrothermal, and acetate methods. To confirm phase purity of synthesized powders, we use Rigaku X-ray diffraction spectroscopy. The symmetric cells are fabricated with the BCZYYb electrolyte and measured by electrochemical impedance spectroscopy at 450-800℃ under wet and dry condition to investigate electrochemical property of materials. References  Kim, J., S. Sengodan, S. Kim, O. Kwon, Y. Bu, and G. Kim, Renewable & Sustainable Energy Reviews 109, 606-618 (2019).  Duan, C. C., J. H. Tong, M. Shang, S. Nikodemski, M. Sanders, S. Ricote, Science 349 (6254), 1321-1326 (2015).  An, H., H. W. Lee, B. K. Kim, J. W. Son, K. J. Yoon, H. Kim, D. Shin, H. I. Ji, and J. H. Lee, Nature Energy 3 (10), 870-875 (2018)  Rioja-Monllor, L., C. Bernuy-Lopez, M. L. Fontaine, T. Grande, and M. A. Einarsrud, Journal of Materials Chemistry A 7 (14), 8609-8619 (2019)  Danilov, N. A., A. P. Tarutin, J. G. Lyagaeva, E. Y. Pikalova, A. A. Murashkina, D. A. Medvedev, M. V. Patrakeev, and A. K. Demin, Ceramics International 43 (17), 15418-15423 (2017)  Rolle, A., S. Boulfrad, K. Nagasawa, H. Nakatsugawa, O. Mentre, J. Irvine, and S. Daviero-Minaud, Journal of Power Sources 196 (17), 7328-7332 (2011). Keywords: Protonic ceramic fuel cells, Thermal expansion coefficient, Electrochemical spectroscopy, Cobaltite cathode * Corresponding author: email@example.com(J. Y. Park)
Authors : Jun-Hee Lim, Sung-Soo Kim
Affiliations : Department of Advanced Materials Engineering, Chungbuk National University, Cheongju 28644, Republic of Korea
Resume : The development of improved battery technology is critical for advancements in a variety of applications ranging from hybrid electric vehicles to consumer electronics. Lithium cobalt oxide (LiCoO2) has been attracting worldwide interest for its application as cathode material in lithium ion batteries, because this material exhibits high specific capacity, low self-discharge and excellent cycle life. The aim of this study is to elucidate the particle coarsening and reaction mechanisms involved in synthesis of LiCoO2 from Li2CO3 and Co3O4 in a large powder batch. The chemical reactants were commercial grade Li2CO3, and Co3O4 powders. The raw materials were mixed in a ball-mill and calcined at 1030 °C for up to 21 hrs. Thermo-gravimetric analysis (TGA) were used to monitor the calcination. The crystallinity and particle morphology was examined by XRD and SEM. To determine the amount of Li2CO3 remaining after calcination, the samples were analyzed for carbon content using the so-called LECO method. TGA reveals that the individual raw materials Li2CO3 and Co3O4 are stable up to the temperature of decomposition of 750 °C and 900 ℃, respectively. However, the mixture begins to react at low temperature of 400 °C to form a ternary eutectic (Li2CO3–Li2O–LiOH) resulting from the partial decomposition of Li2CO3 in the presence of Co3O4, which is consistent with the previous study . The XRD also provides the evidence of the phase transition above the temperature of 400 °C. The low-melting eutectic reacts with Co3O4 to form a LiCoO2 product with sufficient supply of O2. During this process, the aggregates of small reacted LiCoO2 particles were observed. With the prolonged calcining at 1030 °C, the primary particles coarsened to about 20 μm in average size. This particle coarsening enhances the chemical reaction of calcination, due to the exposure of unreacted Li2CO3 remained in the aggregates to flowing O2, and reduces the Li2CO3 residue below the required level of cathode materials application.  A. Lundblad and B. Bergman, “Synthesis of LiCoO2 starting from carbonate precursors I. The reaction mechanism, Solid State Ionics,” 96 (1997) 173-181.
Authors : Bhola Nath Pal, Anand Sharma, Nila Pal and Nitesh Chourasia
Affiliations : School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005, India,
Resume : Ion-conduction oxide ceramic materials are the class of materials that show high ionic conductivity even at room temperature. These materials are commonly found in 1 D olivine structure, 2D layer structure or in 3D spinal structure through which mobile Li or Na ion can move freely. Because of having its Li+/Na+ ion conductivity these materials are widely used for different technological application including solid state electrolyte. Instead of having high ion conductivity, these material are electronically very insulating. These combined high ion conductivity and low electronics conductivity properties enable these material to achieve at very high dielectric constant () with low loss factor that can serve as gate dielectric for low operating voltage TFT. Additionally, these ion-conducting oxide materials can synthesize by low cost, environment friendly solution processed technique. Using these dielectric, solution processed TFT can works even at 1.0 V operating voltage with reasonably high carrier mobility and on/off ratio. Moreover, with these wide band gap dielectric, it is also possible to fabricate low power consuming optically transparent TFT that can be utilize for different optoelectronics application. Because of its optical transparency, visible light can easily enter or exit from the device. Utilizing this properties, energy efficient light emitting transistor and phototransistor can be fabricated by using these low operating voltage TFT. References: 1. “Solution-deposited sodium beta-alumina gate dielectrics for low-voltage and transparent field-effect transistors”, B. N. Pal, B. M. Dhar, K. See, and H. E. Katz, Nature Materials, 8, 898-903, 2009. News and View: “OXIDE DIELECTRICS A change of direction” H Klauk, Nature Materials, 8, 853-854, 2009. 2. Anand Sharma, Nitesh k.Chourasia, Yogesh Kumar, Satyabrata Jit, Shun-Wei Liu, Sajal Biring and B. N. Pal*, Solution processed Li5AlO4 dielectric for low voltage transistor and its application for low power consumption quantum dot phototransistor, J. Mater. Chem. C, 2018, 6, 790-798 3. Role of Electron Donation of TiO2 Gate Interface for Developing Solution-Processed High-Performance One-Volt Metal-Oxide Thin Film Transistor Using Ion-Conducting Gate Dielectric Anand Sharma, Nitesh K. Chourasia, Nila Pal, Sajal Biring,,‡and Bhola N. Pal, J Phys Chem C 2019 123 (33), 20278-20286 4. N K Chourasia, A Sharma, V Acharya, N Pal, S Biring, B. N. Pal* Solution processed low band gap ion-conducting gate dielectric for low voltage metal oxide transistor, Journal of J Alloys Compd. 777 (2019) 1124e1132 5. Gate Interface Engineering for Subvolt Metal Oxide Transistor Fabrication by Using Ion-Conducting Dielectric with Mn2O3 Gate InterfaceNila Pal Anand Sharma, Vishwas Acharya, Nitesh K. Chourasia, Sajal Biring, Bhola N. Pal*, ACS Appl. Electron. Mater. 2019, XXXX
Authors : Gustavo Andrade Silva Alves, Renato Vitalino Gonçalves
Affiliations : Universidade de São Paulo (USP)
Resume : The widespread use of fossil fuels raises several concerns in consequence of the approaching scarcity and their close relation with global warming. In order to address this issue, hydrogen fuel (H2) has been proposed as an efficient zero-emission alternative to these resources, although it is nowadays mostly obtained from fossil fuels. In this context, photocatalytic water splitting has been regarded as one of the most promising methods for the renewable and clean production of H2 from H2O and sunlight. Among the typical photocatalysts for this reaction, sodium tantalate (NaTaO3) is remarkable for its high and stable activity under ultraviolet irradiation, although the wide band gap (4 eV) inhibits the absorption of natural sunlight. The main approach for overcoming this limitation has been tuning the electronic band structure of the compound through doping strategies. In this work, bismuth-doped NaTaO3 nanocubes are obtained with a facile molten salt process, and the material displays considerable photocatalytic activity for hydrogen production under simulated sunlight (AM 1.5G). We suggest that the improved water splitting activity was mainly promoted by the lattice substitution of Ta5+ for Bi5+/Bi3+, that leads to the creation of unoccupied midgap states, thus facilitating visible light absorption through an effective band gap narrowing.
Authors : Hamed Salimkhani, Alp Yurum, and Selmiye Alkan Gursel
Affiliations : Nanotechnology Research and Application Center (SUNUM), Sabanci University, 34956 Istanbul, Turkey
Resume : Studies on Li7La3Zr2O12 (LLZO) based solid electrolytes are dramatically increasing due to their excellent properties such as higher ionic conductivity. However, there is still room for improvement in terms of ionic conductivity. Tetragonal LLZO by itself does not satisfy the conditions for being a good solid electrolyte since its ionic conductivity is too low to be used in batteries and to supply electricity. On the other hand, the cubic version has shown to have promising properties for this application. The difference between these two structures is the presence of vacancies in the cubic one where this is very limited for that of tetragonal. A Tetragonal structure with a space group of I41/acd has a framework with two types of dodecahedral LaO8 polyhedra (8b and 16e) and ZrO6 octahedra (16c). Additionally, Li+ can occupy the tetrahedral 8a, octahedral 16f, and octahedral 32g sites. On the other hand, a cubic polymorph demonstrates a space group of centric SG Ia( 3) ̅d (No.230) and acentric SG I4 ̅3d (No.220). SG Ia( 3) ̅d (No.230) has a structure with a framework of 8-fold coordinated LaO8 dodecahedra residing at 24c Wyckoff position and 6-fold coordinated ZrO6 octahedra residing at 16a Wyckoff position. On the other hand, SG I4 ̅3d (No.220) has a structure with a framework of 8-fold coordinated LaO8 dodecahedra residing at 24d Wyckoff position and 6-fold coordinated ZrO6 octahedra residing at 16c Wyckoff position. Li+ ions can occupy different positions in both structures. İn these structures, dopants play the key role. Therefore, many studies have reported the incorporation of dopants to transform the tetragonal phase into cubic. In this investigation, we have employed Germanium (Ge4+) to study its effect on the structure and conductivity properties of that. For this aim, we prepared four electrolytes with Ge4+ content ranging from 0.1 to 0.8 per formula unit (pfu). Structural characterization was performed using Solid State Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR), Field Emission Scanning Electron Microscopy (FESEM) along with Energy-dispersive X-ray spectroscopy (EDS) and Powder X-Ray Diffraction (PXRD) to understand the site preference of Ge4+ ions. For electrochemical properties, we performed EIS measurements to understand the effect of Ge4+ site preference on the ionic properties of the pellets. From this investigation, it was found that the structure obeys SG I3 ̅ad (No.230) and Ge4+ can occupy the La3+ site. 6Li and 7Li MAS NMR results revealed two different site preferences for Ge4+ namely 24d and 48g for Li ions.
Authors : Anshuman Chaupatnaik¹*, Rodney Chua², Eldho Edison², Madhavi Srinivasan², Prabeer Barpanda¹.
Affiliations : ¹Faraday Materials Laboratory, Materials Research Centre, Indian Institute of Science, Bangalore – 560012, India; ²School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore - 639798.
Resume : SONY’s LiCoO₂/Graphite lithium-ion battery (LIB, circa 1991) made LIBs the indisputable power sources for mobile electronics. Although early research in 1967 on Na-β-Al₂O₃ based Na-S cells by Ford Motors preceded LIBs, both grew parallelly until graphite (which cannot host Na) put LIBs in the limelight. Due to the availability hence cost limits of lithium, sodium-ion batteries (NIBs) have made a comeback with promise for large scale grid storage. On the other hand, leading battery industries tend to pack more material in confined space and accumulate higher energy densities to achieve/advertise longer hours or higher miles. However, this comes at a safety cost which calls for new material exploration, more urgently for NIB anodes. This is because both the LIB anodes (high-energy graphite and high-power Li₄Ti₅O₁₂) are inactive in NIBs. Also, low voltage Na₂Ti₃O₇ may be impractical due to instability of its sodiated phase which leaves hard carbon as the only practical NIB anode. Inspired by Na₂Ti₃O₇, we found PbTi₃O₇ to store both sodium and lithium (300-400 mAh/g) ions in a mechanism like PbTiO₃. NIBs and novel hybrid sodium ion capacitors (NIC) employing monoclinic freudenbergite NaFeTi₃O₈ (200 mAh/g) and high-temperature tetragonal hollandite Na₁.₇Cr₁.₇Ti₆.₃O₁₆ (90 mAh/g) minerals will be discussed. Finally, LIBs employing tetragonal narsarsukite NaTiOSi₄O₁₀¹, monoclinic freudenbergite NaMTi₃O₈ (M = Al, Fe, Cr, Ga), Cr-hollandite minerals and LICs using orthorhombic MLi₂Ti₆O₁₄ (M = 2Na, Ba², Sr³ , Pb⁴) (MLTO) materials will be introduced. The role of atomic structure, ionic conductivity and migration pathways on final electrochemical performance will be described for these titanate anodes⁵. The underlying electrochemical redox mechanism will be explained for selected titanate insertion materials. References ¹ A. Chaupatnaik, M. Srinivasan, P. Barpanda, Appl. Energy Mater., 2019, 2, 2350-2355. ² A. Chaupatnaik, P. Barpanda, J. Mater. Res., 2018, 34, 158-168. ³ A. Dayamani, G. Shinde, A. Chaupatnaik, R. P. Rao, S. Adams, P. Barpanda, J. Power Sources, 2018, 385, 122-129. ⁴ A. Chaupatnaik, P. Barpanda, J. Electrochem. Soc., 2019, 166, A5122-A5130. ⁵ A. Chaupatnaik, A. Rambabu, P. Barpanda, ECS Meeting Abstract, 2018, MA2018-02, 286.
Authors : M. Khalid Hossain (1,2)*, H. Tamura (1), T. Yamamoto (1), K. Kawaguchi (1), Y. Hatano (3), K. Hashizume (1)
Affiliations : (1) Department of Advanced Energy Engineering Science, Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-1 Kasugakoen, Kasuga 816-8580, Japan. (2) Atomic Energy Research Establishment, Bangladesh Atomic Energy Commission, Savar, Dhaka 1349, Bangladesh. (3) Hydrogen Isotope Research Center, Organization for Promotion of Research, University of Toyama, Gofuku, Toyama 930-8555, Japan.
Resume : Proton conducting oxides have a potential application in hydrogen sensors, hydrogen pumps and other electro-chemical devices including tritium purification and recovery system of nuclear fusion reactors. Hydrogen (H) distribution in such oxide materials is very fundamental and important, but its precise measurement is not so easy. In the present study, hydrogen solubility and diffusivity behavior in Y and Co doped barium-zirconates were studied using partially-tritiated deuterium vapor DTO (T = 0.1%, ~2kPa) under two exposure conditions (673K, 2h or 873K, 1h) by tritium imaging plate (IP) technique. The oxide specimens were prepared with conventional powder metallurgy using BaZr0.9Y0.1O2.95 (BZY) and BaZr0.955Y0.03Co0.015O2.97 (BZYC) powder separately by being die-pressed, CIPed (200MPa) and sintered in air at 1913 K for 20 h. The specimens obtained were having a disc shape (~7.5 mm in diameter, ~2.3 mm in thickness) and more than 98% TD. From IP images for the surface of both tritium (T) exposed specimens, uniform T distribution was found. Cross-sectional T concentration profiles of cut specimens showed that T was diffused more deeply into BZY compared to BZYC. The diffusivities of T were obtained as ~0.000001 cm^2/s and ~0.0000005 cm^2/s for BZY and BZYC respectively. Solubilities (H mol/ 1 mol of oxides) for the BZY and BZYC were found about 0.0002 and 0.0001 respectively. BZY shows both higher solubility and diffusivity than the BZYC, suggests that only a small amount of Y doping (~10%) may play a vital role of enhancement of electrochemical activity in DTO exposed proton conducting BaZrO3. Keywords: Proton conducting oxide, barium-zirconate, hydrogen solubility, hydrogen diffusivity, tritium imaging plate method.
Authors : Menghao Chen, Hui Zhang*
Affiliations : Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China; Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology (CAST) No.104 Youyi Street, Haidian District, Beijing 100094, China.
Resume : The key issues with respect to enhancing the electrochemical stability of Li10GeP2S12 (LGPS)-type solid electrolytes (SEs) against high-capacity electrodes as well as mitigating the Li-ion mobility at the interfaces between LGPS-type SE and electrode are much challenging. In the present study, the influence of partial anion substitution on microstructural characteristics and interfacial behavior of Li10MP2S12 (M = Si and/or Ge) SEs has been investigated. The compositional and microstructural optimizations of the modified SEs have been confirmed by using Rietveld refinement against XRD, Raman spectroscopy, SEM, EDXS, etc. Detailed interfacial conduction kinetics of the modified SEs towards Li-In anode or LiNi0.80Co0.15Al0.05O2 (NCA) cathode have been also derived through temperature-dependent impedance technique. For electrochemical stability and cyclic properties, various all-solid-state cells containing a cathode (LiFePO4 or NAC active materials), a modified SE, and an anode (Li or Li-In) have been prepared. It is found that the partial anion substitution of Li10MP2S12 has a beneficial impact on electrochemical stability and interfacial conduction kinetics. Moreover, there shows clear enhancement in discharge capacity and cycling stability of all-solid-state cells using modified SEs during room-temperature galvanostatic cycling. Detailed illustrations about the anion substitution favoring solid-solid contact between modified SE and electrode will be presented. Insights towards designing LGPS-type SEs for practical applications at room temperature will be also discussed in the presentation.
Authors : Tien-Chai Lin1, Wen-Chang Huang1, 2, Bai-Jhong Jheng1
Affiliations : 1 Department of Electrical Engineering, Kun Shan University, No. 195, Kun-Da Rd., Yung-Kang Dist., Tainan, 71003, Taiwan, ROC 2 Green Energy Technology Research Center, Kun Shan University, No. 195, Kun-Da Rd., Yung-Kang Dist., Tainan, 71003, Taiwan, ROC
Resume : The thin film vanadium pentoxide (V2O5) as ion-storage layer for electrochromic device is deposited on ITO glass by an RF magnetron sputtering. The electrochromic properties of the film are discussed after various thermal annealing temperature with/without oxygen flow ambient. It is found that the crystal structure of V2O5 thin film transfer from amorphous to crystalline phases (110) and (021) as the annealed temperature is 400 C. And the grain size of the sample without oxygen flow is larger than that of with oxygen flow after annealing. A degradation of electrochromic property is observed at sample both after the treatment of oxygen flow and thermal annealing. This is due to the oxygen occupies the ion-sites of bleach in/out and results in the reduction of charge capacity. While, an improvement of electrochromic property is obtained at the sample after thermal annealing without oxygen flow. The charge capacity of 69.68 mC/cm2 with a transparent difference, △T between colored/bleached processes of 28.7 % was obtained at the sample after 300 C thermal annealing
Authors : Woohyun Kim, Chanyoung Yoo, Eui-sang Park, Manick Ha, Jeong Woo Jeon, Yoon Kyeung Lee, and Cheol Seong Hwang
Affiliations : Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 08826, Republic of Korea
Resume : Chalcogenide materials are strong candidates for phase-change memory (PCM) as the next-generation memory and the Ovonic threshold switch (OTS) as the selector device. Recent studies reported the additional potential of the chalcogenide materials utilizing different mechanisms for those applications. Resistive switching (RS) without phase change has been recently reported in Ge2Sb2Te5, which is the conventional PCM, and threshold switching (TS) behavior was observed in Te-SbO thin film. Both of them are explained by switching behavior through Te migration. However, these applications require the electroforming process to operate devices. In this work, a new electroforming-free, bipolar resistive random access memory (ReRAM) using GeSe thin films with a Ti-containing electrode will be reported. The Ti electrode has dual functions. First, the Ti layer as a Se sink with a strong tendency to form Ti-Se that helps generates the Se-deficient region in the matrix. Compared with a Ti-free cell composed of Pt/GeSe/TiN (PGT), the effective formation of Ge-rich GexSe1-x as a conducting filament (CF) in the Pt/Ti/GeSe/TiN (PTGT) structure results in electroforming-free memory operation. Second, the composition of GeSe is stabilized by preventing massive Se migration to the top electrode due to the Ti-Se interfacial layer. As a result, significant improvements in reliability, uniformity, endurance, and retention have been achieved. The demonstration of the mechanism and the feasibility of this device will be discussed in the presentation.
Authors : H. J. Lee, T. Moon, S. D. Hyun, B. S. Kim, H. H. Kim, and C. S. Hwang
Affiliations : Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University Gwanak-ro 1, Gwanak-gu Seoul, Republic of Korea
Resume : Two-dimensional electron gas (2DEG) at the interface of two insulating oxides, such as epitaxial LaAlO3/SrTiO3 (LAO/STO), amorphous LAO(α –LAO)/STO, amorphous Al2O3(α-AO)/STO has attracted many interests due to its various application for electronic devices. However, due to the intrinsic high carrier density in a pristine state of α-AO/STO, appropriate pretreatment is required for its appropriate operation as the field-effect transistor(FET). Kim et al. reported that applying a negative gate bias (Vg) to the Pt/LAO/STO device decreased the irreversible conductance of the device. In the present work, it was suggested that adjusting the carrier concentration of 2DEG by applying the Vg on the Pt/α-AO/STO FET enabled the feasible transistor operation. As shown in figure 1(a), the pristine device did not exhibit ‘turn-off’ behavior because of its high intrinsic carrier density. However, when a negative Vg(-8V) was applied to the Pt top electrode during various times, the conductance of 2DEG FET was gradually decreased and eventually lead to well-operated FET behavior. After a stress time of 1000s, the device showed an on/off current ratio~104, a threshold voltage (Vth) of -0.76V, and 500mV/dec subthreshold swing. Figure 1(b) shows the change in relative resistance after negative Vg with respect to the pristine resistance(R0) by hall measurement. Hall measured results clearly showed that the negative Vg modulated the conductance of the channel by changing the resistance of the 2DEG, not other factors such as contact resistance. From these results, it could be concluded that applying a negative Vg to the 2DEG MOSFET device decreased the channel conductance by reducing the carrier density and make the device to work as a FET device.
Authors : Yoon Ho Jang, Ji Hun Kim, Jae Hyun Kim, Jeong Woo Jeon, Cheol Seong Hwang
Affiliations : Department of Materials Science and Engineering and Inter-University Semiconductor Research Center
Resume : In this work, a reservoir computing system using W/HfO2/TiN memristor-based reservoir is demonstrated based on experimental measurement data. In the case of the previously reported researches about physical reservoir computing, memristors having short-term memory were used to compose the dynamic reservoir. There are two major problems when composing the reservoir in this way. The first is the limitation of reservoir processing speed, and the second is the loss of the reservoir controllability. By constructing reservoirs with the appropriate combination of memristors having long-term memory, capacitors, and resistors, reservoir computing systems with dynamics that are completely different from traditional methods can be designed. This reservoir has data processing speeds up to 1000 times faster than previously reported ones and the dynamics of the reservoir are controllable. Training and inference for 4x5 simple images (60 for the training, 20 for the test) with this physical reservoir computing system proceeded. The training accuracy was 100% and the test accuracy was 95%. The Reservoir computing system correctly recognized all the images in the dataset except for one "7" as "9". Using W/HfO2/TiN memristor-based reservoir computing system, neuromorphic hardware can process complicated temporal data at high speed even with a significantly reduced array size.
Authors : T.S.Björheim,1 M.F. Hoedl,2 R. Merkle,2, E. A. Kotomin,2,3, J. Maier,2
Affiliations : 1 Centre for Materials Science and Nanotechnology, University of Oslo, Norway 2 Max Planck Institute for Solid State Research, Stuttgart, Germany 3 Institute of Solid State Physics, University of Latvia, Riga, Latvia
Resume : Oxide materials can dissociatively incorporate water into oxygen vacancies, but the thermodynamic feasibility of this reaction varies greatly. The individual contributions from proton affinity of lattice oxide ions and hydroxide affinity of oxygen vacancies to the hydration enthalpy are experimentally not accessible. This impedes an in-depth understanding of the hydration trends for different materials. We calculate proton and hydroxide affinities applying a thermochemical cycle based on reaction energies from first-principles DFT calculations; band alignment with respect to vacuum ensures the comparability of the calculated affinities . This scheme is applied to a large variety of oxides ranging from binary oxides (Cs2O to SiO2) to ternary oxides, e.g. BaZrO3. Although the proton and hydroxide affinities describe purely ionic reactions, they strongly correlate with the oxide’s electronic structure, in particular with the ionization potential (position of O2p states relative to vacuum level). The slope is steeper for the proton affinity, naturally explaining the often found phenomenological correlation between basicity and more favorable hydration of the oxide. This analysis will be extended to open-shell proton and electron mixed conducting perovskites (e.g. cathode materials).  T.S. Bjorheim, M.F. Hoedl, R. Merkle, E.A. Kotomin, J. Maier, J. Phys. Chem. C (2020) doi: 10.1021/acs.jpcc.9b07570
Authors : Ming Liang Jin1, Sangsik Park2, Kilwon Cho2, Aiping Fu1, Chi Won Ahn3
Affiliations : 1.Institute for Future, Qingdao University, Shandong 266071, China 2.Department of Chemical Engineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea 3.Global Nanotechnology Development Team, National Nanofab Center (NNFC), Daejeon 34141, Republic of Korea
Resume : Skin-adaptive gas sensors provide the next generation platform for real-time protecting human health from monitoring variedly environmental and physiological chemicals. However, the creation of wearable gas sensors that simultaneously perform high sensitivity, selectivity, stability, and scalability has been a big challenge. Here we firstly show the concept of superior performed ionotronic gas sensor, endowing from high sensitivity, selectivity, stability even to scalability. The solid state ionotronic sensor is implemented by the designed hierarchically assembled ionic polymer sensing channel and homogeneous CNTs conductive ink-jet printed patterned electrodes. The commercial ink-jet printer based process eases achieving the sensors on a large area (14 in.). Our wearable device can be ppb level sensitive to the toxic gas, selective from mixed chemical compositions, stable to harsh environmental conditions (1000 cycles thermal aging from -45 degree to 125 degree or 24 hrs humidity aging at 85%) or severe mechanical conditions (1mm radius curvature bending or 50% strain stretching), and scalable from ink-jet printing process. In the true sense, this work provides an essential step for the design and use of ionotronic wearable gas sensor toward high performance and low cost in practical using.
Authors : Lukas Porz, Till Frömling, Atsutomo Nakamura, Ning Li, Maruyama Ryohei, Katsuyuki Matsunaga, Peng Gao, Hugh Simons, Christian Dietz, Marcus Rohnke, Jürgen Janek, Jürgen Rödel
Affiliations : Lukas Porz, Technische Universität Darmstadt; Till Frömling, Technische Universität Darmstadt; Atsutomo Nakamura, Nagoya University; Ning Li, Peking University; Maruyama Ryohei, Nagoya University; Katsuyuki Matsunaga, Nagoya University; Peng Gao, Peking University; Hugh Simons, Technical University of Denmark; Christian Dietz, Technische Universität Darmstadt; Marcus Rohnke, University of Giessen; Jürgen Janek, University of Giessen; Jürgen Rödel, Technische Universität Darmstadt
Resume : Dislocations are known to influence functional properties of oxides  and have recently been suggested as viable means to tune functional ceramics. Besides the difficulty to introduce dislocations into ceramics, their exact influence on functional properties is still unclear. As not all influence factors are known it is difficult to compare one study to another. We introduce dislocations into SrTiO3 single crystals by plastic deformation at different temperatures in a highly ordered manner. Using both impedance spectroscopy and TOF-SIMS it is demonstrated that the introduced dislocations – in contrast to expectations raised from other studies – do no alter the conductivity noticeably. Dark field x-ray diffraction and TEM investigation are used for detailed characterization of the dislocation substructure supplemented by atomic resolution TEM revealing a completely different structure as compared to other studies. We conclude that functional properties depend on a multitude of features. Hence, we suggest to discuss dislocations in functional ceramics in the context of three sets of features: 1) The arrangement (loops, kinks, jogs, screw, edge, etc.), the core structure, and the space charge zone. 1. Szot, K., et al., Influence of Dislocations in Transition Metal Oxides on Selected Physical and Chemical Properties. Crystals, 2018. 8(6).
Authors : Cho. J. W.‡ , Yeo. T. H.‡ , Kyeng. D. H , Choi. W.*
Affiliations : School of Mechanical Engineering, Korea University, Seoul 136-701, Korea
Resume : Exploration of harvesting low-grade waste heat has enabled the self-sustained devices. Recently, the use of thermoelectric polyelectrolytes has been attracting a lot of attention as a potential candidate of the self-powered electrochemical devices. Temperature gradient can induce the ion concentration gradient in polyelectrolyte via diffusion (Soret effect), thereby producing thermally-driven voltage. Among the thermoelectric polyelectrolytes, Poly(styrene sulfonic acid) (PSSH) has shown the outstanding Seebeck coefficient (8mV/K). Therefore, the use of the PSSH electrolyte between conventional supercapacitor electrodes can simultaneously generate voltage and store electrical energy. In this work, we propose the hybrids of hydrous Ruthenium Oxide (RuO2) and carbon as thermally-chargeable supercapcitors for enhancing the overall electrochemical performances. The C/RuO2 hybrid electrode is prepared by soaking in 0.05M KRuO4 solution for 48hours. Carbon fiber covered by hydrous RuO2 nanocomposite was obtained and verified through SEM. Pseudocapacitive reaction between hydrous RuO2 and proton is attributed to not only enhanced half-cell capacitance but also Seebeck coefficient. Thermally induced voltage is improved 200% by using the hybrid of carbon and RuO2 in comparison with the carbon-based electrode. This work is the first time to utilize metal oxide electrodes for thermally chargeable supercapacitors using Soret effect as far as we know.
Authors : Jae-hyun Kang1, Kidan Lee1, Hyun-Mi Kim2 and Ki-Bum Kim1,2
Affiliations : 1 Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea 2 Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
Resume : A solid-state nanopore platform with a low noise level and sufficient sensitivity by transferring silicon nitride (SiNx) membrane onto polydimethylsiloxane (PDMS) dielectric microchannel was fabricated for electrical and optical sensing of DNA translocation. There are several key features of the platform. A highly insulating dielectric substrate is used, which can significantly reduce ionic current root mean square (RMS) noise levels by reducing the effects of parasitic capacitance. By limiting the area of the electrolyte contacting the nanopore membrane to (6 µm)2, the leakage current through SiNx is prevented and the electrical noise is reduced to 12.6 pA RMS at 100 kHz low-pass filtered. Dielectric breakdown, an advanced technique for forming solid-state nanopores, has been used, and can be brought advantage in time and economic aspect. By fabricating a thin (150 µm) upper channel by spin-coating PDMS, fluorescence-stained DNA can be monitored translocating the nanopore through a fluorescence microscope objective lens, usually having a short (~210 µm) working distance. Overall, we demonstrate that this platform overcome some limitations of conventional nanopore devices like high capacitive noise, low production speed, high translocation speed and extend the base of single molecule detection and analysis systems.
Authors : Sarah Eisbacher, Andreas Egger, Edith Bucher, Werner Sitte
Affiliations : Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria
Resume : One of the fundamental challenges of materials research for solid oxide cells is the development of air electrodes with fast oxygen exchange kinetics, high electronic and ionic conductivities, and improved long-term stability. The present work is focused on cobalt-doped lanthanum nickelate La2Ni0.9Co0.1O4+δ with respect to its crystal structure, oxygen nonstoichiometry, defect chemistry, thermal expansion behaviour as well as mass and charge transport properties. The powder was synthesized via the citrate/EDTA method. X-ray powder diffraction confirmed that the material is single-phase and crystallizes in the K2NiF4-type structure. The oxygen exchange kinetics and electronic conductivity were studied using in-situ dc-conductivity and relaxation measurements. The chemical diffusion coefficient of oxygen Dchem and the chemical oxygen surface exchange coefficient kchem as well as the electronic conductivity were determined as a function of temperature and oxygen partial pressure. The oxygen nonstoichiometry was studied by thermogravimetry. Self-diffusion coefficients of oxygen and ionic conductivities were estimated from the experimentally determined values of Dchem and the thermodynamic factor of oxygen. Structure-property relations, especially the influence of cobalt-doping, are discussed by comparing La2Ni0.9Co0.1O4+δ and La2NiO4+δ. The results indicate that La2Ni0.9Co0.1O4+δ offers an attractive option for application as air electrode in solid oxide cells.
Authors : Damin Lee, Je Moon Yun and Kwang Ho Kim
Affiliations : Pusan National University
Resume : A unique three-dimensional hybrid NiCo(CO3)(OH)2 nanowire/NiMn(CO3)(OH)2 nanosheet composite was fabricated using a facile hydrothermal method as a binder-free electrode directly grown on Ni foam for supercapacitors. We examined the synergistic effect by fabricating Ni-Co-Mn ternary electrodes that used Ni-Co with a large specific surface area and Mn with a very high theoretical capacity. The new hybrid electrode had good electrochemical characteristics, exhibiting remarkably high specific capacitances of 1,673.3 and 453.0 F g-1 at 3 and 15 A g-1, respectively. Compared with other samples, the capacitance showed less reduction as the current density increased. This result indicates stable electrode properties with increasing voltage. The cycling stability of the hybrid NiCo(CO3)(OH)2/NiMn(CO3)(OH)2 composite was measured as 82.1% after 5,000 cycles. Additionally, we fabricated an asymmetric supercapacitor employing the NiCo(CO3)(OH)2/NiMn(CO3)(OH)2 composite as the positive electrode and graphene as the negative electrode, which exhibited a high energy density of 27.2 W h kg-1 at a power density of 702.7 W kg-1 and a remarkable cycling stability, with 89.4% capacitance retention after 5,000 cycles. Thus, for the first time, we investigated the dual nano-type structure of an NiCo(CO3)(OH)2 nanowire/NiMn(CO3)(OH)2 nanosheet electrode for supercapacitors and obtained satisfactory results.
Authors : Nan Yang
Affiliations : ShanghaiTech University
Resume : Solid oxide fuel cells (SOFCs) represent a clean, efficient, and universal chemical energy-electric energy conversion technology. Reducing its operating temperature to intermediate range (650-850℃) or even lower temperature range (400-650℃) is an important practical requirement. However, the main obstacle to lowering the operating temperature is due to the slow kinetics of the oxygen reduction reaction (ORR) on the cathode side at lower temperatures, and therefore it is important to explore new cathode materials with good ORR activity. Recently, Mixed ion and electron conductor (MIEC) cathodes are widely studied for their good ionic and electronic conductivities. Among them, Sr-doped Lanthanum Cobaltite based cathode is one of the current research hotspots as a MIEC material. The La1-xSrxCoO3-δ (from x = 0 to x = 0.8) thin films were investigated as the electron conductivity and oxygen reduction activity of a medium and low temperature solid oxide fuel cell (SOFC) cathodes. Thin film materials can avoid external interference caused by microstructure and crystal orientation to better explain the complex relationship between chemical composition, electronic conductivity and ORR activity. It was observed that the electronic conductivity and the polarization resistance varied together, and had the best electronic conductivity and polarization resistance at the Sr doping concentration of x = 0.4. The Co3+/Co4+ change explains that the electronic conductivity and oxygen reduction activity improve as the Sr doping concentration increases from x = 0 to x < 0.4. As the Sr doping content is further increased, a doping condition exceeding 0.4 favors the oxygen vacancy formation process and can be demonstrated by forming Co2+ to balance the system charge. Therefore, Co3+/Co4+ is no longer the best choice for surface oxygen reduction. The increased oxygen vacancy concentration provides more oxygen ion exchange sites for the surface oxygen reduction reaction process, and at the same time, the electron conductivity is deteriorated, thereby lowering the charge transfer efficiency of the oxygen reduction process. Although the concentration of oxygen vacancies is enhanced, the highly doped LSCO film, the non-optimal Co3+/Co4+ valence state and poor electronic conductivity synergistically cause a decrease in oxygen reduction activity. Finally, it is shown that the electronic conductivity and oxygen reduction activity are related to the Co valence state and the surface composition. Our results demonstrate that tuning the mixed valence state with the electronic band structure can be a valid root in designing cathode materials. In particular, heavily doped LSCO film electrodes could have interesting potentials for SOFCs applications at lower temperature. 1. Zhaoxin Zhu, Yanuo Shi, Carmela Aruta, and Nan Yang, ACS Appl. Energy Mater. 2018, 1, 5308−5317.
Authors : Garcia-Fayos, J.1 *, Catalán-Martinez, D., Laqdiem, M.1, Navarrete, L.1 and Serra J.M.1 *firstname.lastname@example.org
Affiliations : 1 Instituto de Tecnología Química (Universitat Politècnica de València – Consejo Superior de Investigaciones Científicas), Av. Los Naranjos, s/n, 46022 Valencia, Spain
Resume : The strategy most commonly employed for the valorization of the non-profitable by-products in the industry is the burning of these, generating heat and power. The EU project iCAREPLAST considers this approach for the valorisation of a by-product gas mixture composed by pyrolysis gases, oxygenates and other hydrocarbons resulting from the up‐cycling of non-recycled plastic waste into alkyl-aromatics. iCAREPLAST project considers the burning of these undesired gas streams by using pure O2 (oxyfuel combustion) in specially-conceived catalytic membrane reactors (Oxygen Transport Membrane modules) to produce heat and power (integrated in a combined cycle) while applying efficient CO2 capture. This work presents the advances conducted within iCAREPLAST project activities in the application of oxyfuel combustion with OTM modules. Several material compositions have been considered for burning gas hydrocarbon streams (CH4/Ar mixtures) at temperatures in the range of 1000-850 ºC. The CH4 conversion and CO2 selectivity for different membrane composition have been studied. The membranes have been surface activated by adding a porous catalytic layer by screen-printing for the promotion of permeation and combustion. The best results are obtained for BSCF membranes, nearly achieving a total combustion of the HC stream (10% CH4 in Ar), nevertheless, the limited stability of BSCF membranes under reducing and CO2-containing environments makes necessary the selection of more stable alternatives. Other tested compositions show lower results with respect to CH4 combustion towards CO2 generation, despite their high stability.
Authors : Jacqueline M. Börgers , Prof. Dr. Roger A. De Souza
Affiliations : Institute of Physical Chemistry, RWTH Aachen University, Aachen, Germany
Resume : Mixed-valence manganites are very promising candidate materials for resistive switching due to the possibility to generate multilevel resistance states as well as area-dependent switching. This enables their use in future non-volatile memories or novel neuromorphic circuits. The aim of our work is to gain a deeper understanding of the microscopic mechanisms of resistive switching in mixed valence manganites with the focus on Sr-doped LaMnO3 (LSMO). It is widely accepted that ionic transport plays an important role in the field of resistive switching. Due to the presence of grain boundaries (GBs) in technologically-relevant CMOS-compatible polycrystalline manganite devices and the knowledge that GBs significantly influence the ionic transport, the investigation of the impact of GBs on resistive switching is of special interest. Therefore, we are studying the ionic transport in LSMO as well as along grain-boundaries in bicrystals of LSMO by Molecular Dynamics simulations, employing empirical pair potentials. In particular, the effect of Sr dopants and cation vacancies on oxide-ion transport is examined.
Authors : Anshuman Chaupatnaik¹*, Eldho Edison², Madhavi Srinivasan², Prabeer Barpanda¹.
Affiliations : ¹Faraday Materials Laboratory, Materials Research Centre, Indian Institute of Science, Bangalore - 560012, India; ² School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore - 639798
Resume : Presence of shared edge, particularly of shared faces, decreases the stability of ionic structures (Pauling’s IIIrd rule) e.g. making hcp-rutile with the least number of [TiO₆] shared edges (two) the most stable TiO₂ polymorph.¹ Further, on (one or three) lithium insertion, Li in 8a [LiO₄] sites of ccp-spinel LiTi₂O₄ or Li substituted defect spinel Li₄Ti₅O₁₂ (LTO) migrate along with incoming Li to vacant 16c [LiO₆] sites to prevent face sharing of [TiO₆]-[TiO₆], [LiO₆]-[TiO₆] or [LiO₄]-[TiO₆] polyhedra in the intermediate transition states, a feat not preventable in case of stable hcp-rutile, hcp/ccp-brookite or unstable ccp-anatase.² This immediately triggers a unique two-phase separation which results in a favorable 1.5 V flat Ti(IV)/Ti(III) redox voltage vs Li far above 0 V lithium deposition. This makes Li₄Ti₅O₁₂ the only commercial (Altair Nano, Toshiba SCiB, Yinlong) safe dendrite free high-power anode as an alternative to graphitic carbons, which is also reported by Hydro Quebec to cycle over 30000 times vs LiFePO₄ retaining 90% capacity. Along these lines, orthorhombic 𝘊𝘮𝘤𝘢 MLi₂Ti₆O₁₄ (MLTO) (M = 2Na, Sr, Ba, Pb)³ ⁴ ⁵ prepared by quick combustion synthesis exhibit similar voltage (1.3-1.45 V) and capacity (100-160 mAh/g for reversible uptake of upto 4 Li ions). BaLi₂Ti₆O₁₄ was a serendipitous high conducting product (10e-3 S/cm, 300ᵒC) of an attempt to add Ba to stabilize a high temperature type III superionic conducting Ramsdellite phase (MnO₂) of Li₂Ti₃O₇ having a rutile type arrangement of 2X1 [TiO₆] polyhedras which was also reported to reversibly insert 2.24 Li.⁶ ⁷ Lithium diffusivity (migration pathways, their temperature dependent activation energies and diffusion coefficient) probed using a combination of methods involving bond valence site energy analysis (BVSE), AC bulk conductivity analysis and electrochemistry versus Li and versus activated carbon (hybrid ion capacitors) will be demonstrated. References ¹ L. Pauling, J. Am. Chem. Soc., 1929, 51, 1010-1026 ² D.W. Murphy et. al., Solid State Ionics, 1983, 9, 413-417 ³ A. Chaupatnaik, P. Barpanda, J. Mater. Res., 2018, 34, 158-168 ⁴ A. Dayamani, G. Shinde, A. Chaupatnaik, et.al., J. Power Sources, 2018, 385, 122-129 ⁵ A. Chaupatnaik, P. Barpanda, J. Electrochem. Soc., 2019, 166, A5122-A5130 ⁶ W.J. Zheng et. al., Solid State Ionics, 1989, 35, 235-239 ⁷ M.E. Arroyo y de Dompablo et. al., Mater. Res. Bull., 1997, 32, 993-1001
Authors : Aswathy M. Narayanan, Arun M. Umarji
Affiliations : Materials Research Centre, Indian Institute of Science, Bengaluru, India-560012
Resume : A common feature of transition metals that is being exploited for many applications is their ability to shuttle between different oxidation states. This gives rise to oxygen vacancies in their oxides. Creation and filling up of these vacancies can be directly used for oxygen production through ion transport membrane separation or temperature/pressure swing absorption. Oxide materials that respond by an oxygen intake/release at lower temperatures can utilize low-temperature waste heat for oxygen separation. This in turn brings down the cost of oxygen production. Herein, YBaCo2O6-x, Dy0.5Y0.5BaCo2O6-x and DyBaCo2O6-x are explored for low-temperature oxygen enrichment. These oxides were synthesized through solid-state reaction and the oxygen separation properties at various temperatures were studied using a home-built volumetric setup. The oxygen intake temperatures of the sample were found to vary depending upon the rare-earth cation size. The lowest absorption temperature of 523 K was observed for DyBaCo2O6-x. Interestingly, DyBaCo2O6-x had the largest saddle point radii through which oxide ion migration occurs. The effect of the synthesis method and microstructure on the oxygen holding capacity of DyBaCo2O6-x has also been analyzed. For this, DyBaCo2O6-x was synthesized through a combination of solution combustion synthesis followed by calcination and sintering at different temperatures. The particle size was found to have a profound effect on the oxygen intake of DyBaCo2O6-x.
Authors : Guoxing Chen1, Frederic Buck2, Irina Kistner3, Marc Widenmeyer1, Thomas Schiestel2, Andreas Schulz3, Matthias Walker3, Anke Weidenkaff1, 4
Affiliations : 1Department of Materials and Earth Sciences, Technische Universität Darmstadt, 64287 Darmstadt, Germany; 2Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, 70569 Stuttgart, Germany; 3Institute of Interfacial Process Engineering and Plasma Technology, Universität Stuttgart, 70569 Stuttgart, Germany; 4Fraunhofer Institute for Materials Recycling and Resource Strategies IWKS, 63457 Hanau, Germa-ny
Resume : Plasma-based technologies providing extremely flexible ‘turnkey’ applications are increasingly attracting interest in renewable energy usage and CO2 conversion into carbon neutral fuels [1-2]. Here, we report a breakthrough concept combining plasma and mixed ionic-electronic conductor, hollow fiber membranes for significantly enhancing the oxygen permeability which may stimulate the CO2 conversion by direct product separation. Several CO2-tolerant oxygen transport membrane (OTM) materials with high oxygen permeation fluxes have been developed in our previous studies [3-7]. In this work, structure and composition of La0.6Ca0.4Co0.5Fe0.5O3−δ (LCCF) hollow fiber mem-branes were characterized before and after oxygen permeation tests in a CO2 plasma excited by mi-crowaves. The oxygen permeation flux can be increased by one order of magnitude via this new plasma-assisted hollow fiber membrane concept, reaching up to 4 ml min−1 cm−2 in a CO2 contain-ing atmosphere. A constant high oxygen permeation flux was maintained during long-term opera-tion, which is of major importance for commercial application. The applied rapid switching between operation and stand-by demonstrated the additional strength of the setup to cope with a potential unstable supply when using renewable electricity. These results show that plasma-assisted CO2 con-version combined with a LCCF hollow fiber membrane allows to simultaneously enhance oxygen permeation and CO2 conversion by inhibiting the reverse reactions. Therefore, it may be considered as a future industrial procedure for the autarkic formation of C1 platform chemicals from CO2 and (excess) regenerative energy.  A. Bogaerts et al., ACS Energy Lett. 3 (2018), 1013.  G. Chen et al., Appl. Catal. B: Environ. 214 (2017), 114.  G. Chen et al., J. Membr. Sci. 590 (2019), 117082.  G. Chen et al., J. Membr. Sci. 595 (2020), 117530.  G. Chen et al., Chem. Eng. J. (2019), 123699. https://doi.org/10.1016/j.cej.2019.123699  G. Chen et al., Front. Chem. Sci. Eng. (2019), 1. https://doi.org/10.1007/s11705-019-1886-0.  M. Widenmeyer et al., J. Membr. Sci. 595 (2020), 117558. Corresponding author: email@example.com
Authors : G. Zafeiropoulos1, P. Varadhan1, L. Kamphuis1, H. Johnson2, S. Kinge2 , M.C.M. van de Sanden1, M.N. Tsampas1
Affiliations : 1Dutch Institute For Fundamental Energy Research (DIFFER); 2Toyota Motor Europe (TME)
Resume : Renewable hydrogen is a promising alternative to CO2-emitting fossil fuels in overcoming the climate crisis. A well-investigated technique for hydrogen production is sunlight-induced ‘water splitting’ - the photoelectrochemical (PEC) dissociation of water (into hydrogen and oxygen) on the surface of semiconductors under irradiation. Most of the research on photoelectrochemical reactors has focussed on using liquid water as the water feedstock. However, using water vapour, present as ambient humidity, can provide an interesting alternative since it enables the use of solid state devices which are compact, convenient and their performance is not limited by bubble formation. These reactors, so-called polymeric electrolytic membrane PEC cells (PEM-PEC) require porous photoelectrodes for gas-flow rather than the conventional planar design used in the liquid phase. Here we show that i. by functionalization with ionomer layers, these devices can operate even at 30% relative humidity ii. using porous electrodes overcome the ionic transport limitations typically observed when scaling-up planar photoelectrodes and iii. The solar-to-hydrogen performance can be significantly improved by integrating low-band gap photoelectrode materials such as BiVO4 – up to eight times higher photocurrents (i.e. 2 mA cm-2) in the PEM-PEC cell compared to TiO2 and WO3 under one sun illumination.
Authors : Roberts Eglitis
Affiliations : Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., Riga LV1063, Latvia
Resume : Current commercially available rechargeable Li-ion batteries, for example LiCoO2, are working mostly in the 4 V regime. One often suggested possibility to improve the effectivity of Li ion batteries are the creation of the 5 Volt cathode materials. We performed quantum mechanical calculations on the average battery voltage for the Li2CoxMn4-xO8 (x=0,1,2,3 and 4) cathode materials by means of the WIEN2k computer program package. The calculated average battery voltages for x = 0,1,2,3 and 4 are equal to 3.95, 5, 4.47, 4.19 and 3.99 V [1-3]. Our ab initio calculation results are compared with the available experimental data for x = 0, 1, 2 and 4 which are equal to 4, 5, 5 and 4 Volt. Thereby, for the Li2Co1Mn3O8 battery cathode material, our calculated average battery voltage around 5 Volt is in perfect agreement with the experimentally available battery voltage values of 5 Volt. Nevertheless, our calculated average battery voltage is underestimated (4.47 V) for the Li2Co2Mn2O8 cathode material, which also experimentally exhibits the 5 Volt voltage. References:  Roberts Eglitis, Int. J. Mod. Phys. B 33, 1950151 (2019)  R. I. Eglitis, Phys. Scr. 90, 094012 (2015)  R. I. Eglitis and G. Borstel, Phys. Stat. Sol. A 202, R13 (2005)
Authors : Sanghyun Park(1), Min Chul Chun(1), Minjin Kim(1), Yongjun Cho(1), Cheoljun Kim(1) & Bo Soo Kang(1)
Affiliations : (1)Department of Applied Physics, Hanyang University, Ansan 15588, Republic of Korea
Resume : Hf-based oxides have been extensively investigated as promising candidates for the switching devices due to the ferroelectricity observed in the nanoscale thin films. It enables to lower the power consumption and enhance the switching speed of the memory devices. In this study, the switching parameters were analysed based on the domain switching model in the polycrystalline Si-doped HfO2 films (HSO). We found that the field-dependent switching time is related to the activation field. We investigated the activation field as a switching parameter depending on the annealing temperature in terms of the phase transition and the migration of bulk lattice oxygen by using impedance spectroscopy. Additionally, the distribution of local leakage current by using the conductive atomic force microscopy (AFM) and the loss of oxygen vacancies in the interface by using electron energy-loss spectroscopy (EELS) proved the electrical and the structural variation of the ferroelectric. As a result, we discussed which is the dominant factor affecting the domain switching, phase formation or oxygen vacancies considering the thermal energies.
Authors : Yuanye Huang (a)*, Rotraut Merkle (a), Dan Zhou (a), Wilfried Sigle (a), Peter A. van Aken (a), Wendelin Deibert (b), Mariya E. Ivanova (b), Wilhelm A. Meulenberg (b), Joachim Maier (a)
Affiliations : (a) Max Planck Institute of Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany (b) Forschungszentrum Jülich, IEK-1, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
Resume : Ba(Zr,Ce,Y)O3-x (Ce≤20 at%) shows a combination of high bulk proton conductivity and chemical stability which makes it a suitable electrolyte for protonic ceramic fuel cells (PCFC). The problem of its poor sinterability is largely alleviated by Solid State Reactive Sintering (SSRS) with NiO addition, which forms a transient (Ba,Ni,Y)Oz liquid phase. However, too high Ni contents are detrimental, leading to decreased bulk conductivity and mechanical stability. In this work, the sintering mechanism of SSRS, Ni effect on the proton uptake and conductivity are investigated by XRD, TG, SEM, TEM, impedance spectroscopy. 0.5 wt.% NiO is found to be the best compromise between largely improved sintering/grain size and decreased bulk proton uptake caused by the extraction of Ba into the transient liquid phase. Based on these results, 5 cm × 5 cm anode-supported Ba(Zr,Ce,Y)O3-x electrolyte membranes were successfully prepared by tape-casting using SSRS. They exhibit a proton conductivity of 0.002 S/cm at 600 ˚C. These results are very promising for the fabrication of large-area PCFC beyond the usual small lab-size cells. Funding from BMBF (ProtOMem, Förderkennz. 03SF0537C) is acknowledged.  J. Tong, D. Clark, L. Bernau, M. Sanders, R. O’Hayre, J. Mater. Chem., 20 (2010) 6333  Y. Huang, R. Merkle, J. Maier, in preparation  Y. Huang, R. Merkle, J. Maier, in revision  W. Deibert, M. Ivanova, Y. Huang, R. Merkle, J. Maier, W.A. Meulenberg, O. Guillon, in preparation
Authors : Arabinda Barman, Chetan P Saini, Ujjal Das, Rahul Singhal, Rajendra Singh
Affiliations : Nanoscale Research Facility, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, Delhi-110016, India; Material Science Division, Inter-University Accelerator Centre, Aruna-Asaf Ali Marg, New Delhi, Delhi-110067, India; Department of Phyiscs, Department of Physics, National Institute of Technology Silchar, Assam 788010, India; Department of Physics, Malaviya National Institute of Technology Jaipur ,Jawahar Lal Nehru Marg, Jhalana Gram, Malviya Nagar, Jaipur, Rajasthan 302017; Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, Delhi-110016, India
Resume : The storage gap between classical memory and storage class in memory hierarchy needs to be fill up with new “storage class memory” (SCM). To achieve this, metal oxides (MO) based resistive random memory (ReRAM) has emerged as one of the best contenders among SCMs. The resistive switching (RS) mechanism of MO based ReRAM is governed by the electric field dependent generation and migration of oxygen vacancies (Vo). But, controlled formation of OVs is a challenge. Doping of metallic and gaseous elements in MOs could be effective to systematically engineer the OV configuration. However, judicious choice of dopants is important to achieve such OV configuration. Here, we demonstrate how Ti and Cr doping by ion implantation in TaOx thinfilm controls the RS property of TaOx based ReRAM. In detail RS were investigated in Pt/Ti/Ti:TaOx/Pt and Pt/Cr:TaOx/Pt devices. Significant RS was observed in Cr- implanted samples within applied bias of ±1V, while switching was not observed in case of Ti implanted sample. Furthermore, compliance current (Icc) controlled voltage sweep revealed multi-level RS in sample implanted with 100 KeV Cr- ion at a fluence of 2 × 1015 ions/cm2. The distinct doping dependent performances of RS memory is discussed in the framework of defect formation energy in TaOx with respect to Ti and Cr. The results were further supported with in-depth X-ray photoelectron spectroscopy study. The study could be helpful in designing MO based high-performance RS memory devices.
Authors : Andrew Chesnokov, Denis Gryaznov, Eugene A. Kotomin
Affiliations : Institute of Solid State Physics, University of Latvia, Riga, Latvia; Institute of Solid State Physics, University of Latvia, Riga, Latvia; Institute of Solid State Physics, University of Latvia, Riga, Latvia, Max Planck Institute for Solid State Research, Stuttgart, Germany
Resume : In the present work we address the problem of localization of electrons in an undoped and Tb-doped CeO2-δ near an oxygen vacancy (Vo). To account for strong correlation effects, we based our calculations on the Hubbard model (PBE U) and hybrid PBE0 exchange-correlation functional. The system was allowed to have different possible oxidation states (3 and 4 ) of the constituent cations with the aid of distinct simultaneously applied Hubbard-U parameters. In response to the presence of Vo, different modes of electronic localization have emerged. To identify the ground state configuration of electronic localization, we have employed group theory analysis with site symmetry approach. We demonstrate, by analyzing differences in full energies, that Tb ions embedded in CeO2 can be in either 3 or in 4 oxidation state and based on that, we predict that these states can coexist even in an absence of Vo, unlike other lanthanide cations. We discuss the dependence of Gibbs formation energy of Vo on the temperature and oxygen partial pressure and discuss formation of the small polaron. We show that the presence of Tb ions in the CeO2-δ system lowers the Gibbs formation energy of Vo almost fourfold in comparison to an undoped system. In the case of Tb3 formation, the compensating hole density is delocalized over a whole supercell leading to enhanced Fermi energy occupation by O 2p states, and, thus, enhanced hole conductivity, consistent with the electrical conductivity measurements. In addition, we describe configuration which allows for a formation of experimentally obtainable small polaron [1-2].  R.A. Evarestov, D. Gryaznov, M. Arrigoni, E.A. Kotomin, A. Chesnokov, J. Maier, Phys. Chem. Chem. Phys. 19 (2017) 8340–8348.  A. Chesnokov, D. Gryaznov, E. Kotomin, Opt. Mater. 90 (2019) 76–83.
Authors : Kudyakova, V.S. (1), Politov, B.V. (1) & Suntsov, A.Yu. (1)
Affiliations : (1) Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russia
Resume : The double perovskites PrBaMn2–xFexO6–δ were synthesized via glycerol-nitrate precursors. Thermogravimetry, differential scanning calorimetry and high-temperature X-ray powder diffraction were used to investigate phase stability at heating up to 1000 °С in air. A theoretical model of the defects formation in manganites was developed, using the results of coulometric titration. It includes antifrenkel-like pair formation, disproportionation and oxidation of manganese ions with interstitial oxygen appearance equilibriums. The oxygen intake/release and oxidation/reduction processes were studied for powder and sintered samples. The reversibility of oxygen exchange was found in cycling tests at 950 °С by switching gas flow between air and 5% H2/Ar mixture. The maximum oxygen storage capacity attained equals to 3.4 wt%, which corresponds to the non-stoichiometry variations Δδ within 0.94 - 1.03 interval. The influence of iron doping on phase stability, oxygen storage capacity, oxygen release/intake kinetics and defects formation mechanisms were determined. This work was carried out by support of the Russian Science Foundation under grant № 19-79-10147.
Authors : Grieshammer, S.*(1,2), Eisele, S.(1,2), Draber, F.(2), Martin, M.(1,2).
Affiliations : (1) Helmholtz-Institut Münster, Forschungszentrum Jülich GmbH, Germany (2) Institute of Physical Chemistry, RWTH Aachen University, Germany
Resume : Acceptor doped barium zirconate is a promising proton conductor suitable as electrolyte in protonic-ceramic fuel cells. The doping with e.g. yttria leads to the formation of oxygen vacancies and exposing to a hydrating atmosphere at elevated temperatures introduces mobile protons into the system leading to high proton conductivity. The degree of hydration is a function of the partial pressure water and the temperature. In most studies, the classical mass action law for non-interacting defects is applied to model the defect chemistry of this system and connect the proton concentration to the thermodynamic parameters. However, at typical defect concentrations the interactions of defects are no longer negligible. The present study investigates influence of defect interactions on the free energy of hydration in yttrium-doped barium zirconate. Combining a DFT derived interaction model with an MMC multistage sampling approach [1,2], we obtain the free energy of interaction, which can be separated into contributions to the internal energy and the configurational entropy. Neglecting volume changes, the interaction dependent part of the equilibrium constant is deductible from the free energy of interaction. This enables an ab-initio calculation of the relation between water partial pressure and degree of hydration for a concentrated, interacting system. First results indicate intermediate degrees of hydration as the energetically favorable state, as the attractive interactions between dopant and protons cannot compensate rising proton-proton repulsion and entropy loss indefinitely.  J. P. Valleau and D. N. Card, J. Chem. Phys., 57, 5457, 1972  S. Grieshammer and M. Martin, J. Mater. Chem. A, 5, 9241, 2017
Authors : (1)Nicolas Onofrio, (2)Benjamin Helfrecht, (3)David Guzman, (4)Alejandro Strachan
Affiliations : (1)Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR ; (2)Laboratory of Computational Science and Modeling, Institut des Matériaux, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland (3)Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA (4)School of Materials Engineering and Birck Nanotechnology Center Purdue University, West Lafayette, IN 47906 USA
Resume : To reach the downscaling limit of next-generation electronics, thin films and layered materials are inevitable, and mass transport phenomena must be therefore controlled. Interestingly, depending on the application, various quality of the ionic barriers are desired. For example, a vertical Cu/MoS2 memristor, switching via the formation of nanoscale Cu filaments has been recently demonstrated. The low switching voltage (~100 mV) was achieved thanks to the small diffusion barrier for Cu crossing few layers MoS2 at grain boundaries. By contrast, to prevent Cu (electro) migration, ultrascaled Cu interconnects were capped with few layers of 2D materials. The effect of the capping layer does not only act as a thin migration barrier but also as a liner for improved electronic and thermal transport. Although these recent results are exciting, only few 2D materials have been explored (Graphene, MoS2, TaS2) and little is known about the structural and chemical dependence of these materials on the migration barriers. In this work we systematically investigated Cu cross-layer diffusion in various perfect and defective phases of group IV, V and VI transition metal dichalcogenides, Xenes as well as phosphorene-like 2D materials, and extracted thermodynamics and kinetics characteristic quantities, based on density functional theory calculations. We found that the chemistry and phase of the materials affect the shape and height of migration barriers, and we rationalised diffusion with key structural features. When focusing on perfect elemental materials (Si, Ge, P, etc.), we found that puckered phosphorene-like structures usually lead to smaller migration barriers compared to their buckled counterpart. Overall, we found materials with Cu migration barriers ranging from nearly 0 up to 5 eV, providing potential materials to be used as a barrier/liner for ultrascaled Cu interconnects, and solid electrolytes for few layers vertical memristor devices. Finally, we identified some stable Cu sites inside the single layer of several 2D materials, demonstrating the possibility of interstitial doping in materials as thin as few angstroms.
Authors : Seohyun Park, Damin lee, Kwang Ho Kim
Affiliations : Division of Materials Science and Engineering
Resume : A dual phase bismuth oxyiodide (BiOI/Bi9I2) nanostructure battery type supercapacitor electrode is synthesized using chemical bath deposition (CBD) and the capacitance and energy/power density (ED/PD) reported. The supercapacitor electrode BiOI/Bi9I2 exhibited a specific capacitance of 515.5 F g−1 (capacity value 143 mA h g−1) at a current density of 2 A g−1, with 80% of the original capacitance retained, even at a high current density of 4 A g−1 over 5000 cycles. A pouch-type symmetric supercapacitor (PSS) device was created, based on BiOI/Bi9I2//BiOI/Bi9I2 electrodes (acting as anode and cathode electrodes) with 6 M KOH as the aqueous electrolyte and with an extended voltage up to 1.5 V. The ED value was 38.2 W hkg−1 at a current density of 2 A g−1, and the PD was 2280.4 W·kg−1. Three PSS type BiOI/Bi9I2//BiOI/Bi9I2 devices were connected in series and used to illuminate a red LED for 20 min with full brightness, confirming potential use as an energy storage device. The above summarized results indicate that BiOI/Bi9I2//BiOI/Bi9I2 could be a potential electrode for battery type supercapacitor applications.
Authors : Hyunwoo Lee, Damin lee, Kwang Ho Kim
Affiliations : Division of Materials Science and Engineering
Resume : A self-grown copper sulfide@copper oxide (CuS@Cu2O) positrode synthsis by a hydrothermal method followed by 2 h of air annealing method (at 300 °C) from copper-foam (Cu-F) is envisaged as supercapattery electrode material in 0.1 M KOH electrolyte solution where remarkable capacities of 145, 134, 125, and 112 mA h g⁻¹ at current densities of 1, 2, 3, and 4 A g⁻¹, respectively, with about 80% retention ability after 2000 redox cycles, are obtained. The electrochemical performance obtained for self-grown CuS@Cu2O positrode is better than those reported previously for self-gown CuS, Cu(OH)2, and CuO electrode materials. An asymmetric supercapattery device fabricate using CuS@Cu2O as a positrode with Bi2O3 as negatrode, i.e., CuS@Cu2O//Bi2O3, demonstrates an energy density of 52 Wh kg⁻¹ at a power density of 750 W kg⁻¹ at 0.5 A g⁻¹ which, when connected in series with another similar device, lightens a LED with its full-bright intensity, confirming a commercial potential of designed electrochemical supercapattery device.
Authors : Won Bin Kim *(1), SangMyeong Lee (1), Jae Myeong Lee (1), Dong Hoe Kim (2), Gill Sang Han (1), Hyun Suk Jung *(1)
Affiliations : (1) School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea; (2) Department of Nanotechnology & Advanced Materials Engineering, Sejong University, Seoul 05006, Republic of Korea;
Resume : Resistive switching memory has attracted attention as a next-generation memory device owing to its fast-switching speed, low power consumption, high endurance and retention performances characteristic. Usually, resistive switching memory is composed of a metal/active layer/metal structure. So far, many researchers have used oxide materials for use as active layer. However, due to the high process temperature and relatively high operating voltage, there have been many efforts to replace the oxide active materials. Recently, organic-inorganic lead halide perovskite such as, CH3NH3PbI3 materials have been successfully applied to active layer because of the low power consumption, low process temperature, and flexible characteristics. Despite of these advantages, organic-inorganic lead halide perovskite still has problems to be solved including intrinsic unstable nature of materials, poor endurance, retention properties, and toxic issue of lead. In this study, we developed the lead-free and environmentally stable Cs2AgBiX6 double perovskite materials for use as active materials. The resistive switching memory employing this material exhibited the high-temperature stability and high endurance properties with low operating voltage. These results demonstrate one of strategies for improving the stability and performance of halide perovskite-based resistive switching memory.
Authors : J. Sirvent (1), F. Baiutti (1), M. Bianchini (1), N. Alayo (1), A. Tarancon (1,2)
Affiliations : (1) Institut de Recerca en Energia de Catalunya (IREC), Jardins de les Dones de Negre 1, 08930, Sant Adrià de Besòs, Barcelona, Spain; (2) ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain
Resume : The widespread of Internet of Things technologies will be highly dependent on the development of sustainable and efficient power microdevices that can meet the energy demand of wireless electronic systems and low-power grid nodes. Reversible, full-ceramic micro solid oxide cells (micro-SOCs) represent a very promising approach which is able to store excess energy in chemical form (electrolysis mode) and to release it as electric power (fuel cell mode). Nevertheless, the full integration of micro-SOCs in real-life microelectronic devices remains a challenge. One of the key limiting areas in the development of these systems is related to the selection of the material for the fuel electrode, as it must ensure mixed conductivity and high thermal stability in reducing conditions, while being compatible with thin-film fabrication technologies. In this contribution we present a thorough investigation of several thin-film fuel electrode materials fabricated by pulsed laser deposition (Ce-, Ti-, and Cr-based), which was carried out by complementary structural and electrochemical techniques (X-ray diffraction, electron microscopy, atomic force microscopy, ellipsometry, electrochemical impedance spectroscopy). We propose a novel, highly ordered, heterostructure based on (La,Sr)(Cr,Mn)O3 and samarium-doped-ceria, which presents the highest electrochemical performance among the tested materials (area specific resistance ≈10 ohm*cm2 at T ≈700 ºC).
Authors : Tobias M. Huber a,b,c,*; Matthaeus Siebenhofer a; Alexander Schmid a; Alexander Viernstein a; Markus Kubicek a; and Jürgen Fleig a;
Affiliations : a Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, Vienna, A-1060, Austria; b Next-Generation Fuel Cell Research Center (NEXT-FC), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan; c Huber Scientific, Rottmayrgasse 17/29, Vienna, A-1120, Austria;
Resume : Oxides which change their defect concentration with the oxygen partial pressure p(O2) are important materials for solid oxide fuel and electrolysis cells (SOFCs, SOECs) and sensors. Exact characterization of these materials over a large p(O2) range is necessary to understand their defect related properties such as ionic and electronic conductivity. For such measurements two different oxygen pump systems were designed and constructed: one was integrated in the hull of the experimental chamber while the other one is insertable into an experimental chamber. The capability of these setups are exemplified with measurements on LaSrFeO3 (LSF) thin film electrodes and SrTi O3 (STO) single crystals. The first setup shows an outstanding pumping performance (from 10-5 bar to 10-17 bar oxygen partial pressure in less than 5 minutes). The second setup can be equipped with an additional oxygen sensor directly next to sample in the electrochemical measurement cell. This design has two advantage: i) the oxygen pump is kept at one temperature while the electrochemical cell operates at various measurement temperatures and ii) the setup can be operated statically with different chamber base pressures or with continuous gas stream. The oxygen partial pressure is controlled with a PID controller to automatically change the desired set point. Additionally, the setup can be connected to mass flow controllers and a furnace controller to automatically change all experimental parameters. Different cells can be implemented, for example for Van-der-Pauw, current voltage and impedance measurements on thin films, pellets and microelectrodes.
Authors : M. M. S. Lira1, S. Anelli1, R. Z. Yarbay-Şahin1, F. Baiutti1, M. Torrell1, A. Tarancón1,2
Affiliations : 1IREC, Dept. Advanced Materials for Energy, Jardins de les Dones de Negre 1, 08930 Barcelona (Spain) 2ICREA, 23 Passeig Lluís Companys, 08010 Barcelona (Spain)
Resume : Nowadays the exsolution of nanostructured active phases on stable ceramic oxides is attracting researchers’ attention. Surfaces decorated with consistently catalytically active nanoparticles assume a key role in numerous fields, such as fuel cells, electrolysers and catalytic reactors. Understanding the mechanisms and limitations of the exsolution process in terms of synthesis temperature and atmosphere is mandatory to smartly implement this strategy in practical electrodes for solid oxide cells. Herein, we present the synthesis and characterization of exsolved active dopants such as, nickel on a Ni doped Gd0.1Ce0.9O2-δ (GDC) (Ni-GDC) as fuel electrode material, and Silver on Ag doped La0.6Sr0.2MnO3 perovskite (Ag-LSM) as oxygen electrode. Both electrodes materials has shown, under determined conditions of temperature and reducing atmosphere (5%H2-Ar), exsolution of the dopant element. In this way, the active phase remains exposed on the surface increasing the catalytic activity of the former material. Insights into the exsolution mechanism are also derived from presented experiments. Microstructural and morphological characterization of both electrode materials with exsolved active phases was carried out by X-ray diffraction, thermal characterization processes (DSC, TPR), scanning electron microscopy. Eletrochemical impedance spectroscopy (EIS) was carried out at operating temperature to evaluate the performance of the exsolved materials as electrodes for SOC.
Authors : Alexander K. Opitz (1), Christopher Herzig (1), Matthias Gerstl (1), Andreas Nenning (1), Jürgen Fleig (1), Andreas Limbeck (1), Martin Bram (2)
Affiliations : (1) TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164, 1060 Vienna, Austria; (2) Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-1), 52425 Jülich, Germany
Resume : Gadolinia-doped ceria (GDC) is a very versatile material in solid state ionics. It is used as an electrolyte in solid oxide cells due to its comparatively high oxide ion conductivity, but can also be employed as a fuel electrode owing to its mixed ionic electronic conductivity under reducing conditions. Especially in case of the latter application, poisoning with H2S, which is a common impurity in fuel gases, is controversially discussed in literature. While some studies claim high resilience of GDC towards H2S poisoning, other studies with slightly different experimental conditions – such as gas composition or applied electrochemical polarisation – do show a severe sulphur poisoning effect. Here we report on the interaction of model-type GDC thin-films with H2S-containing, reducing atmospheres. The conductivity of these thin films is characterised by impedance spectroscopy and the contributions of grain and grain boundary conductivity are separated. Exposure to H2S causes a noteworthy decrease of the grain boundary conductivity, while the grain interior is not affected. Quantification of the amount of incorporated sulphur is approached by a novel analytic technique, which is optimized for compositional quantification of non-soluble samples such as GDC: laser ablation of solids in liquids with online inductively coupled plasma mass-spectrometric detection (online-LASIL-ICP-MS).
Authors : K. N. S. Schuldt, C. Lohaus, und A. Klein
Affiliations : Department of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany; Department of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany; Department of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany
Resume : One of the most relevant material systems for cathode materials in solid oxide electrochemical cells is the mixed ionic and electronic conducting (La,Sr)(Co,Fe)O3. Studies concerning the La1-xSrxCoO3-δ series show a metallic conductance upon Sr-doping, while the La1-xSrxFeO3-δ (LSFO) series remains insulating in an unusually wide doping range. In order to understand this unexpected wide insulating behavior of LSFO and its correlation to the electronic structure, LaFeO3 thin films doped with Sr (40%) were in-situ investigated using photoelectron spectroscopy. Studying these films in oxidizing and reducing conditions reveals an accessible Fermi level position from 0.15 eV to 1.15 eV above the valence band maximum, respectively. The experimental results show that the upper Fermi level position is limited by the Fe3+/Fe2+ charge transition. A stepwise re-oxidation of the films exhibits a modification of the electronic band structure. Here, unoccupied Fe3d eg-states do not remain in the valence band, but are raised above the Fermi level. Furthermore, it leads to a reduction of oxygen vacancies and by this to an altered compensation mechanism. In LSFO, this alternative compensation is obtained by the creation of holes, localized in an unoccupied Fe3d eg-related split-off state corresponding to a Fe4+. Hence, the holes are not introduced at the top of the valence band, but lead to this observed localized split-off states in the band gap, causing the unexpected insulating behavior.
Authors : Phuoc-Anh Le, Van-Truong Nguyen, Kung-Hwa Wei
Affiliations : Department of Materials Science and Engineering, National Chiao Tung University, 1001 Ta-Hsueh Rd., Hsinchu 300, Taiwan.
Resume : We reported a new and environmentally friendly phloroglucinol additive incorporated polyvinyl alcohol-LiClO4 gel polymer electrolyte for flexible symmetrical solid-state supercapacitor. The incorporation of 10 wt% phloroglucinol into PVA–LiClO4 gel polymer electrolytes show much higher specific capacitance (144 F g–1) than that without phloroglucinol (60 F g–1), because of the redox reaction of phloroglucinol in the system. We used the PVA–LiClO4 with 10 wt% phloroglucinol for gel polymer electrolytes in combination with nitrogen-doped graphene nanosheets-based electrodes as the anode and cathode to fabricate a symmetrical solid-state supercapacitor. The fabricated supercapacitor involving phloroglucinol redox additive has an energy density of 2.3 W h kg–1 at a power density of 150 W kg–1, which is higher than the one without redox additive (1.9 W h kg–1 at a power density of 150 W kg–1). Moreover, the supercapacitor involving redox additive has good stability; its capacitance remains up to ~94% after 5000 charge/discharge cycles. New gel polymer electrolyte, incorporating phloroglucinol as a redox additive, for the preparation of bendable symmetrical SSCs illustrates promising research.
Authors : Markov, A.A., Nikitin, S.S., Politov, B.V., Merkulov, O.V., Suntsov, A.Yu., Leonidov, I.A., Patrakeev, M.V.
Affiliations : Institute of Solid State Chemistry Ural Brunch of Russian Academy of Sciences, 91, Pervomaiskaya St., 620990, Yekaterinburg
Resume : The perovskite-type ferrites Sr1-xCexFeO3-δ are considered as promising materials for high-temperature electrochemical application. The aim of this work is to elucidate cerium influence on oxygen non-stoichiometry, high-temperature defect equilibrium, and charge transport. The ferrite series of Sr1-xCexFeO3-δ (x=0.05, 0.1, 0.15) was synthesized by a solid-state reaction using high purity CeO2, and Fe2O3 oxides and SrCO3 carbonate as starting materials. Oxygen content and electrical conductivity of these materials were measured in the range of oxygen partial pressure from 10–19 to 0.5 atm at 750-950°C by coulometric titration and four-probe dc method, respectively. Data on oxygen content were employed for defect equilibrium modeling taking into account reactions of iron oxidation, charge disproportionation occurring on iron ions, and electron exchange between iron and cerium. The modeling allowed good approximation of experimental data and calculating ion and electron carrier concentrations. Analyses of experimental data on electrical conductivity enabled separating partial contributions of oxygen ions, p- and n-type carriers on the base of different dependence on oxygen partial pressure. An important result of cerium substitution for strontium found to be a considerable increase of n-type charge carrier concentration. Mechanisms of cerium influence on oxide properties are discussed. This work was supported by Russian Science Foundation grant №19-79-10147.
Authors : Evgeniy Makagon, Maximilian F. Hoedl, Rotraut Merkle, Eugene A. Kotomin, Joachim Maier, Igor Lubomirsky
Affiliations : Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel; Max Plank Institute for Solid State Research, Stuttgart, Germany; University of Riga, Institute of Solid State Physics, Riga, Latvia;
Resume : Acceptor-doped BaZrO3 is a promising electrolyte for protonic ceramic fuel cells as it combines high bulk proton conductivity with good chemical stability. The protonic conductivity is achieved by dissociative water incorporation into oxygen vacancies formed by acceptors on Zr4+ sites. We have investigated the influence of dopants, oxygen vacancies, and protons on the macroscopic elastic and electromechanical properties of acceptor-doped BaZrO3 ceramics. Ceramics of BaZr(1-x)X(x)O(3-x/2+δ)H(2δ) with X = Ga, Sc, In, Y, Gd and 0.05 < x< 0.2 were prepared by solid state reactive sintering and hydration. Ultrasonic pulsed echo time of flight measurements were used to infer the Young’s and the shear moduli. Both moduli decrease by up to ~20% due to the presence of dopants and oxygen vacancies that cause local lattice distortions [1,2]. Water incorporation into the vacancies decreases the moduli even further. An unexpectedly large electrostriction coefficient (M33 ~1E-16 m^2/V^2) was detected with a capacitive proximity sensor for all type of dopants. M33 of the hydrated ceramics exhibits a Debye-type relaxation with the relaxation frequency exponentially increasing with the ionic radius. This implies that the protons are associated with the dopants, and the binding strength decreases from Ga to Y.  M. F. Hoedl, E. Makagon, I. Lubomirsky, R. Merkle, E. A. Kotomin, J. Maier, Acta Mater. (2018) 160, 247  E. Makagon, R. Merkle, J. Maier, I. Lubomirsky, Solid State Ionics (2020) 344, 115130
Authors : Antipinskaia, E.A., Politov, B.V., Suntsov, A.Yu., Kozhevnikov, V.L.
Affiliations : Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russia
Resume : Today, within the framework of materials science topics, the leading positions are consistently occupied by the studies on the perovskite-like structures with general formula ABO3. Despite saving sustained interest in these compounds over the years and a wide range of studied compositions and their properties, continued development in this direction does not lose its relevance up to this day. In particular, layered compounds with alterating rock-salt and perovskite blocks - so called Ruddlesden-Popper phases, for example manganites, till now were not studied in much detail compared to other perovskite structure modifications. However, with a more thorough research, these objects show curious features, thereby potentially representing scientific interest. In the scope of current work, layered perovskite-like oxides corresponding to the chemical formula Sr4Mn3-xFexO10-δ, where x = 1; 2, were synthesized using the glycine-nitrate method. The X-ray diffraction confirmed the obtained compounds to be single- phase. The studying of oxygen non-stoichiometry dependences on temperature and oxygen pressure revealed an interesting phenomenon associated with a significant increase in oxygen capacity for a composition with low iron content. Accordingly, these compounds appear to be promising not only for a further detailed research, but also for practical application as oxygen carrier materials.
Authors : Politov B.V., Marshenya S.N., Mychinko M.Yu., Suntsov A.Yu., Shein I.R., Zhukov V.P., Kozhevnikov V.L.
Affiliations : Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russia
Resume : Complex oxides of d-metals with perovskite-like structure are acquiring great attention in modern science. Apparently, the number of fields these compounds can be applied for is constantly growing due to the enormous amount of their functional properties discovered. For instance, the so-called “double perovskites” possess high electron/ion mobility, good catalytic and magneto-transport properties in wide range of external conditions (temperature, pressure, magnetic field etc.). In this regard, the practical aspects of their usage are undoubtedly better studied experimentally rather than theoretically. Accordingly, the lack of theoretical knowledge should be somehow filled with. This work is aimed at ab initio investigation of various typical representatives – strontium molybdates, layered cobaltites and recently discovered Co-based double perovskites with high Ta/Nb concentrations. All these are perspective candidates for practical use as solid oxide fuel cell electrodes. In this study we try to analyze using combined theoretical and experimental approaches how the electron band structure features of the initial phases are changing upon doping and what are the reasons underlying the respective alterations in functional properties of materials considered. The results of the research done provide solid fundamental for recent experimental findings and also propose some new advantageous doping strategies. This work was supported by the RFBR under grant №19-33-90173
Authors : G. E. Wilson, P. Boldrin, A. Cavallaro, A. Aguadero
Affiliations : Dept. of Materials, Imperial College London; Dept. of Earth Science & Engineering, Imperial College London; Dept. of Materials, Imperial College London; Dept. of Materials, Imperial College London
Resume : Hydrogen production by chemical looping reactors have gathered recent interest with the focus of improving overall efficiencies. The study of new materials for this process aims to lower the reaction temperature and increase the overall fuel production rates and volumes.1 Research conducted in solid oxide fuel cells has been transferred to this field for the development of oxygen storage materials that accommodate large changes in oxygen non-stoichiometries (δ) at low reaction temperatures for large hydrogen production volumes. La2CoO4+δ is a mixed ionic electronic conductor with the ability to store a large oxygen excess (δ=0.22) within the interstitial lattice sites.2 Prior research for intermediate temperature solid oxide fuel cell cathodes observed fast oxygen exchange kinetics.3 Initial thermogravimetric analyses confirm the material’s large non-stoichiometry to be activated at 600 C by H2 assisted reduction, and reoxidised under a humid gas flow to produce hydrogen at temperatures as low as 375 C. Additional investigations, using evolved gas analysis, intend to understand the material’s redox properties and kinetics to enhance the water splitting performance. Further experiments will prove the effect of experimental conditions on the structural morphology and surface condition to probe the material’s stability under operating conditions. References  A. Thursfield et al., Energy and Environmental Science, 5, 7421-7459 (2012)  A. Aguadero et al. Zeitschrift für Naturforschung B, 63, 615-622 (2008)  C.N. Munnings et al., Solid State Ionics 176, 1895 – 1901 (2005)
Authors : G.E. Wilson, A. Cavallaro, A. Aguadero
Affiliations : Dept. of Materials, Imperial College London
Resume : Solar energy has the potential to meet the world’s energy demands with surplus supply to the world’s annual energy consumption received every hour. Storing this energy by thermochemical redox reactions is a solid oxide technology of increased interest in recent years. Research into new oxygen exchange materials, such as perovskites, are of interest due to their large storage capabilities and history in other oxygen exchange technologies. Strontium cobalt oxides doped with antimony are a promising family of perovskites due to their toptactic reversible redox cycling and large oxygen storage capabilities within intermediate temperatures ranges.1,2 Thermogravimetric analyses have yielded encouraging results for fast reduction and oxidation kinetics. Further experiments will explore these observations further and aim to understand the lifetime of this material through systematic degradation studies. 1. A. Aguadero et al., Chem. Mater., 2010, 22, 789-798 2. A. Aguadero et al., Chem. Mater., 2012, 24, 2655-2663
Authors : B. Sarpi (1), R. Belkhou (2), D. Stanescu (3), C. Rountree (3), H. Magnan (3), J.-B. Moussy (3) and A. Barbier (3)
Affiliations : (1) MAXPEEM beamline, MAXIV Laboratory, Lund, Sweden. ; (2) HERMES beamline, Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, France. ; (3) Service de Physique de l'Etat Condensé, UMR 3680 CEA-CNRS, Gif-sur-Yvette, France.
Resume : Thin films play a major role in the development of technological fields including spintronics, sensors, energy harvesting, etc. Among the variety of applications, thin oxide heterostructures coupling magnetic and ferroelectric (FE) orderings controlled by an electric field offer promising perspectives for information storage. However, we will show that electrical poling involves a plethora of effects which strongly influence the oxide properties. We explored poled oxide layers by combining Piezo Force Microscopy (PFM) with (X-rays) Spectromicroscopy. To disentangle the roles of piezoelectricity and polarization, we considered (non-FE) α-Fe2O3 and (FE) α-Fe2O3 / BaTiO3 and NiFe2O4 / BaTiO3 bilayers on Nb-doped SrTiO3 single-crystals. After DC poling with a PFM tip, the phase and amplitude signals were investigated systematically. Although non-FE, hematite displays fair PFM contrasts pointing towards an electromechanical coupling with charge injection inside the dielectric. Spectromicroscopy confirms our interpretation, revealing several underlying influences in all systems. First, the surface electron density is altered by a tip / surface charge transfer. When poled, α-Fe2O3 experiences a dramatic accumulation of Fe(2+) defects at the surface which remains limited for NiFe2O4. Our analysis suggests that electromigration is the dominant process. Remarkably, poling also influences the properties of secondary photoelectrons emission. We demonstrate that electrical poling modifies in many ways the oxide intrinsic properties beyond the initial purpose. This stresses the need for a global description when dealing with such effects involving polarity, electrical transport, electro –resistance and –migration, etc.
Authors : Maria Gombotz, H. Martin R. Wilkening
Affiliations : Graz University of Technology, Institute for Chemistry and Technology of Materials, 8010 Graz, Austria; Graz University of Technology, Institute for Chemistry and Technology of Materials, 8010 Graz, Austria and ALISTORE - European Research Institute, CNRS FR3104, Hub de l'Energie, Rue Baudelocque, 80039 Amiens, France
Resume : The Y-halides Li3YBr6 or Li3YCl6 have recently gained attention as they might be used as electrolytes in all-solid-state batteries. Asano et al. already reported their use in secondary cells delivering a voltage of 4 V . Ion dynamics, especially the influence of morphology, defect structure and grain size on ionic transport, needs, however, a thorough investigation if we want to understand the driving forces behind Li ion hopping processes in the ternary compounds. To study the impact of structural disorder on ionic transport we took advantage of mechanosynthesis combined with annealing steps to prepare Li3YBr6 in two different morphologies, viz. in a microcrystalline, i.e., a coarse-grained form, and in a nanocrystalline form. Structural details were studied by X-ray diffraction as well as by high-resolution 6Li and 79Br magic angle spinning nuclear magnetic resonance spectroscopy. Impedance measurements helped us to look at changes in ionic conductivity over a wide temperature range. Interestingly, our results point to a phase transition at approximately room temperature. Time-domain 7Li nuclear magnetic relaxation, see, e.g., , provided information on the change of local Li ion dynamics, such processes are difficult to be detected by conductivity measurements alone.  T. Asano et al., Adv. Mater. 2018, 30, 1803075.  M. Gombotz et al., Phys. Chem. Chem. Phys. 2019, 21, 1872.
Authors : Vikas Kumar1, David Smyth-Boyle2, Suchanuch Sachdev3, Dilek Ozgit Butler3, Pritesh Hiralal3, Shiladitya Paul1,2
Affiliations : 1Department of Engineering, University Road, Leicester, LE1 7RH | United Kingdom 2TWI Ltd., Granta Park, Great Abington, Cambridge CB21 6AL, United Kingdom. 3Zinergy UK Ltd., Nuffield Road, Cambridge, CB4 1TG, United Kingdom
Resume : Portable batteries are a reliable source of mobile energy to power smart wearable electronics, medical devices, communications, and others internet of thing (IoT) devices. There is a continuous increase in demand for thinner, more flexible battery with high energy density and reliability to meet the requirement. For a flexible battery, factors that affect these properties are the stability of current collectors, electrode materials and their interfaces with the corrosive electrolytes. State-of-the-art conventional and flexible batteries utilise carbon as an electrode and current collector, which cause high internal resistance (~100 ohms) and limit the peak current to ~1mA. This makes them unsuitable for a wide range of applications. Replacing the carbon parts with metallic current collector would reduce the internal resistance (and hence reduce parasitic loss), but significantly increases the risk of corrosion due to galvanic interactions within the battery. To overcome these challenges, low cost electroplated metals (such Ni, Sn, and Ag) on copper (Cu) were studied as a potential anode current collector for a zinc-manganese oxide primary battery with different concentration of acidic electrolyte (NH4Cl/ZnCl2). Open circuit potential (OCP) of electroplated metals were monitored using electrical impedance spectroscopy (EIS) for different concentration of electrolytes to optimise the thickness of the plated coatings. Our results show that the electroplated coatings suffer excessive corrosion in the acidic electrolyte. Corrosion rate of different coatings were calculated with Tafel analysis. The results demonstrate that channelling and/or open porosity provide an easy pathway for electrolyte to penetrate thorough the electroplated coatings to corrode the Cu/coating interface. We further investigated the incorporation of a printed carbon/graphene corrosion protection layer and their effects on the shelf-life, internal resistance and the overall capacity of the printed flexible battery system.
Authors : Devaraj Ramasamy, João C.C. Abrantes, Eduarda Gomes, António A.L. Ferreira, Jorge R. Frade
Affiliations : proMetheus, Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Viana do Сastelo, 4900-347 Viana do Castelo, Portugal; Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193I Aveiro, Portugal
Resume : Electrical conductivity of dense CGO (5 at% Gd) based materials sintered by hot pressing at relatively low temperature (1000°C) was characterized by impedance spectroscopy as a function of temperature in air, in order to identify each microstructural contribution to the overall behaviour. The specific grain boundary conductivity shows a significant increase of more than one order of magnitude when compared with samples sintered at higher temperatures (1400°C) without pressing. However, total conductivity is not significantly changed because gains in specific conductivity are nullified by decrease in grain size, with corresponding increase in number of grain boundaries. Thus, subsequent heat treatments, up to 1400°C, were performed to find the best compromise between the effects of the specific properties and the grain size. Y2O3 additions were also used to seek grain boundary heterogeneities, with potential effects on space charge potential, and expected increase in specific conductivity of grain boundaries. This positive effect was confirmed for samples fired at lower temperatures, but is reverted at higher temperatures, possibly due to the yttria dissolution in the CGO lattice, as confirmed by changes in lattice parameter
Authors : Eduarda Gomes, João C.C. Abrantes, António A.L. Ferreira, Devaraj Ramasamy, Jorge R. Frade
Affiliations : proMetheus, Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Viana do Сastelo, 4900-347 Viana do Castelo, Portugal; Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193I Aveiro, Portugal
Resume : Grain boundaries are frequently responsible for a poor performance of gadolinium-doped ceria-based electrolytes, due to a low ionic conductivity, orders of magnitude smaller than the bulk conductivity. Silica, the dominant impurity in many low-grade ceramics, namely, in ceria-based materials, has a detrimental effect on grain boundaries conductivity. Several previous works had explored the silica-scavenging effect. In the present work, we exploit an alternative approach using the addition of 5% (w/w) of Y2O3, as silica scavenging agent, and sintering by hot pressing at low temperature to minimize bulk dissolution of yttrium in the CGO lattice. Gadolinium-doped ceria-based powders were co-fired with additions of 1% (w/w) of silica, and silica and yttrium oxide to test the silica scavenging role of yttrium. The samples were prepared by hot press at low temperature (1000ºC) and were characterized by impedance spectroscopy as a function of temperature in air, in order to de-convolute different microstructural contributions to the overall electrical behaviour. Combined information obtained from structural, microstructural, and electrical characterization allowed one to study the impact of new phases on the resulting ceria-based solid eletrolytes.
Authors : António A.L. Ferreira, João C.C. Abrantes, Eduarda Gomes, Devaraj Ramasamy, Jorge R. Frade
Affiliations : proMetheus, Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Viana do Сastelo, 4900-347 Viana do Castelo, Portugal; Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193I Aveiro, Portugal
Resume : Zirconia-based materials are still the state of art electrolyte for high temperature electrochemical systems, and for non-electrochemical applications. Their purity is known to affect performance, thus requiring high grade expensive precursors and additional concerns about contamination during high temperature processing and/or during long term applications at intermediate temperatures, as found for contamination by silica. Thus, the purpose of this work was to demonstrate the scavenging ability of praseodymium oxide to minimize or suppress the impact of contamination by silica. In the present work, one used TZP precursor powders from Tosoh and Innovnano. Starting materials of both powders contained significant fractions of monoclinic phase, coexisting with tetragonal zirconia, and yielded highly dense samples after sintering at 1450°C/2h. Praseodymium oxide and/or silicon oxide additions did not affect significantly the sintering behavior. Additions of Pr and Si yielded co-existing tetragonal and cubic phases, as revealed by XRD and Rietveld refinements, with impact on lattice parameters of the cubic phase. The electrical characterization showed the expected decrease in conductivity after addition of silicon oxide addition, and also showed that this negative impact is at least partially reverted by additions of praseodymium oxide.
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HARVESTORE sponsored session: Interface & Surface Phenomena (II) : Nini Pryds
Authors : Mark Huijben
Affiliations : MESA+ Institute for Nanotechnology, University of Twente, Netherlands
Resume : Solid-state batteries offer great potential for large improvements in safety and lifetime, as well as higher energy and power densities. However, the interfacial composition and structure between solid electrolytes and electrode materials often present major deviations from those of the bulk materials. Elucidating the nature of the involved interfaces is required to establish a rational approach towards the successful combination of materials in a new generation of solid-state cells. Controlled interfaces between a solid-state electrolyte (Li0.33La0.5TiO3), cathode (LiMn2O4) and anode (LI4Ti5O12) have been realized in 2D-planar and 3D-vertical thin film geometries by applying pulsed laser deposition. The influence of the temperature and deposition rate on the morphology evolution of lithium-based vertically aligned nanocomposites is modelled by applying Kinetic Monte Carlo Simulations with activation energies for hopping obtained experimentally and with minimum restrictions for hopping directions. Epitaxial engineering is used to control the crystal orientation within the 2D and 3D geometries, which enables a unique insight into the relation between electrochemistry and crystal directionality of such chemically complex inorganic interfaces, not obtainable in single crystals or polycrystalline samples. D.M. Cunha et al., ‘Morphology Evolution during Lithium-Based Vertically Aligned Nanocomposite Growth’, ACS Appl. Mater. Interfaces 2019, 11, 44444−44450.
Authors : A.Morata(a), V. Siller(a), F.Chiabrera(a), M. Nuñez(a), R. Trocoli(a), M. Stchakovsky(b), A. Tarancón (a,c)
Affiliations : (a)Department of Advanced Materials for Energy Applications, Catalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1, 08930 Sant Adrià del Besòs, Barcelona, Spain (b) HORIBA Scientific, Avenue de la Vauve, Passage Jobin Yvon, 91120 Palaiseau, France (c)ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain
Resume : Thin film solid state batteries are called to play a prominent role as a power supply for future micro-devices. Despite few commercial solutions exist, many efforts are still invested in the development of such devices with improved capabilities. The challenge is to develop appropriate electrodes with high capacity, stability and fast performance, and electrolytes with a low ionic resistance at room temperature. Furthermore, it is crucial to pay attention to the electrochemical compatibility between the components and to provide good quality interfaces. Here we present the development of LiMn2O4 (LMO) and Li4Ti5O12 spinel electrodes, and Li1+xAlxTi2-x(PO4)3 electrolyte thin films. The materials have been deposited by means of Large Area Pulsed Laser Deposition (LA-PLD), using multi-layering strategies to balance lithium content of the films. Exhaustive structural and electrochemical characterization of the layers has been carried out. In particular, recently developed operando spectroscopic ellipsometry and Raman spectroscopy techniques have been used for the study of ion-transport phenomena and the track of Lithium content and volume expansion during cycling.
Authors : Jordi Sastre, Xubin Chen, Abdessalem Aribia, Ayodhya N. Tiwari, Yaroslav E. Romanyuk
Affiliations : Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
Resume : Thin film deposition techniques can be useful for the fabrication of better solid-state batteries and enable the industrial development of this technology. Reducing the thickness of the electrolyte material to a few hundred nanometers facilitates ionic conductance for faster charge-discharge and reduces the total volume of inactive material, therefore increasing energy density. Lithium garnet Li7La3Zr2O12 (LLZO) electrolyte is a promising ionic superconductor for solid-state lithium batteries. In bulk, this material has demonstrated high ionic conductivities (0.1 - 1 mS/cm), as well as a wide electrochemical stability window (against metallic lithium anode and high potential cathode materials). However, processing this ceramic material in the form of films presents still some challenges. We present a method for fabricating crystalline LLZO thin films at about 650°C (significantly below the standard processing temperatures of about 1100°C) with densities and ionic conductivities comparable to the values observed in bulk ceramic pellets. By engineering the interface between a thin film LiCoO2 cathode and the solid-state electrolyte, we demonstrate for the first time an operational thin film lithium battery with sputtered ceramic LLZO as solid-state electrolyte.
Authors : Lacey, S.D.*(1), Gilardi, E.(2), Merckling, C.(3), Saint-Girons, G.(4), Botella, C.(4), Pergolesi, D.(2) & El Kazzi, M.(1)
Affiliations : (1)Paul Scherrer Institut, Electrochemistry Laboratory, Switzerland; (2)Paul Scherrer Institut, Multiscale Materials Experiments Laboratory, Switzerland; (3)Imec, Kapeldreef 75, 3001 Leuven, Belgium; (4)Universite de Lyon, Ecole Centrale de Lyon, Institut des Nanotechnologies de Lyon, CNRS UMR5270, 36 avenue Guy de Collongue, 69134 Ecully Cedex, France
Resume : The integration of highly crystalline (lithium-based) oxide thin films on silicon substrates is essential in order to fabricate high performance solid-state devices, especially for microbattery and memristor applications. However, growing epitaxial oxide films directly on silicon requires high deposition temperatures (~600°C) and often high oxygen partial pressures, which leads to undesirable species (e.g. SiO2 and silicates) that compromise the crystal quality of the oxide. To overcome this, 3 nm of γ-Al2O3 was used as a passivation layer prior to the growth of the desired oxide on Si(111) substrates. Li4Ti5O12 (LTO) was chosen as a representative oxide for use in both batteries and memristors. XPS as well as in- and out-of-plane XRD measurements confirmed the sharp heterostructure interface and the high quality of the epitaxial LTO films. Excellent electrochemical cycling was also achieved for the stack against lithium metal in a conventional liquid electrolyte. In order to make a solid-state microbattery, a solid electrolyte (LiPON) was first sputtered on the LTO/Al2O3/Si stack followed by deposition of metallic lithium or amorphous silicon (a-Si) as the counter electrode. For the latter, LTO was successfully chemically lithiated beforehand, since as-deposited LTO and a-Si do not structurally possess mobile lithium ions. Beyond microbatteries, we will discuss the promising attributes of a stack consisting of chemically lithiated LTO with a-Si for memristive devices.
Authors : Matthäus Siebenhofer, Tobias Huber, Gernot Friedbacher, Werner Artner, Jürgen Fleig, Markus Kubicek
Affiliations : Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria & Kyushu University, Japan; Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria
Resume : The mixed conducting perovskite material La0.6Sr0.4CoO3−δ (LSC) is a very promising cathode material for application in a solid oxide fuel cell (SOFC) due to its catalytic properties for the oxygen surface exchange reaction and its high electronic conductivity. However, one of the remaining obstacles in the broader use of LSC is its susceptibility to changes of the surface structure due to various environmental factors. To further deepen the understanding of these degradation mechanisms and possible countermeasures, it is necessary to retrace the properties and the structure of LSC to a point before degradation starts. La0.6Sr0.4CoO3-δ thin films grown on YSZ single crystals were investigated directly in the stage of deposition by means of In-Situ Impedance Spectroscopy during Pulsed Laser Deposition (IPLD). This method allows the investigation of dense thin films unaltered by degradation and provides information about the oxygen exchange kinetics as well as the defect chemistry of pristine LSC thin films. Our measurements revealed remarkably low surface resistance values (1.3 Ωcm² at 600 °C and 0.04 mbar O2) compared to films measured outside the PLD chamber (20 Ωcm² at 600 °C and 0.04 mbar O2). Also the activation energy of the surface exchange resistance at 0.04 mbar p(O2) is significantly lower than at ambient conditions (1 eV vs. 1.3 eV) and degradation happens considerably slower than in air. The experiments further showed that the initial surface exchange resistance of LSC grown on YSZ is not influenced by the grain size of the columnar film. Additionally the chemical capacitance of LSC thin films was linked to the concentration of oxygen vacancies and shows that LSC thin films exhibit lower oxygen vacancy concentrations than the corresponding bulk material.
Authors : Elisa Gilardi 1, Daniele Pergolesi 1, Emiliana Fabbri 2, Vladimir Roddatis 3, George F. Harrington 4,5,6, , John A. Kilner 4,7, Enrico Traversa 8,9 and Thomas Lippert 1,7,10
Affiliations : 1 Laboratory of Multiscale Experiments, Paul Scherrer Institut, 5232 Villigen-PSI, Switzerland 2 Electrochemistry Laboratory, Paul Scherrer Institut, 5232 Villigen-PSI, Switzerland 3 Institute of Materials Physics, University of Göttingen, 37077 Göttingen, Germany 4 Department of Materials, Imperial College London, London SW7 2BP, United Kingdom 5 Next-Generation Fuel Cell Research Centre, Kyushu University, 744 Motooka, Nishi-ku Fukuoka 819-0395, Japan 6 Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139, U.S.A. 7 International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan 8 School of Materials and Energy, University of Electronic Science and Technology of China, 2006 Xiyuan Road, Chengdu 611731, Sichuan, P. R. China 9 NAST Center & Department of Chemical Science and Technology, University of Rome Tor Vergata, 00133 Rome, Italy 10 Department of Chemistry and Applied Biosciences, Laboratory of Inorganic Chemistry, Vladimir-Prelog-Weg 1-5/10, ETH Zürich, 8093 Zürich, Switzerland
Resume : The interface between 8% mol yttria stabilized zirconia (YSZ) and acceptor doped ceria has important technological applications as these two oxides are usually coupled in high temperature solid oxide fuel cells (HT-SOFC) to improve the stability of the electrolyte at the interface with the cathode. Thin films and multilayers are useful model systems to study interface effects which can affect the conductivity, such as strain, space charge effect and interdiffusion. In this work, multilayers of YSZ and samaria doped ceria (SDC) are grown by pulsed laser deposition, increasing the number of layers and consequently of interfaces and keeping the thickness constant. While no structural variation is observed between bulk and interface, electron energy loss spectroscopy highlights the reduction of cerium ions in a 2 nm thick layer at each interface with YSZ. Concurrently, the conductivity measured in plane, decreases increasing the number of interfaces, suggesting the progressive confinement of the ionic conduction to the YSZ layers. The analysis of the conductivity data indicates the formation of an insulating layer of about 2 nm at each interface. At these interlayers both ionic and electronic conduction are very small compared to YSZ and SDC bulk.
Authors : Emily Skiba, Haley B. Buckner, Nicola H. Perry
Affiliations : Department of Materials Science & Engineering, University of Illinois at Urbana-Champaign
Resume : Mixed conductors find application in sensors, fuel/electrolysis cell electrodes, reactors for chemical fuel production, and gas separation membranes. In some cases, low-to-intermediate temperature processing and operation may be advantageous for limiting initial energy expenditure and long-term degradation, respectively. In such conditions, amorphous or poorly crystalline structures may prevail, though their performance has not been widely studied. Therefore, in recent work, we have been applying X-ray absorption spectroscopy and in situ impedance and optical measurements during crystallization, in order to explore how mixed conductor structure-property relationships are impacted by the degree of crystallinity. Our initial studies on thin films of the perovskite SrTi0.65Fe0.35O3-x (STF) demonstrate that the amorphous material, prepared by pulsed laser deposition at room temperature, contains relatively under-coordinated cations with a lower average oxidation state for Fe than in the crystalline counterpart, prepared via higher temperature deposition or annealing. These results are consistent with an observed increase in sub-gap optical absorption and electrical conductivity during crystallization, which is attributed to an increase in hole concentration. These local structural and defect chemical changes can help to explain the evolution of other functional properties of STF during crystallization, such as the dramatic increase in oxygen exchange kinetics.
Solid State Energy Devices (III): Solid Oxide Cells : Werner Sitte
Authors : Sandrine Ricote 1, Steven Pirou 2, Xanthi Georgolamprou 2, Ragnar Kiebach 2, Alexis Dubois 3, Robert J. Kee 1
Affiliations : 1 Colorado School of Mines, 1500 Illinois Street, CO 80401 Golden, USA 2 Technical University of Denmark, DTU Energy: Department of Energy Conversion and Storage, Anker Engelunds Vej, 2800 Kgs. Lyngby, Denmark 3 HyET Hydrogen USA LLC, 43 Rock Lane, CA 94708, Berkeley, USA
Resume : Proton-conducting ceramics, such as yttrium doped barium zirconates/cerates referred to as BZCY, are studied for intermediate temperature applications, including protonic-ceramic fuel/electrolysis cells, electrochemical compressors, or catalytic membrane reactors. In the presence of steam, the material hydrates with the consumption of oxygen vacancies and the formation of protonic defects. Hydration-induced chemical expansion (lattice expansion upon protonic defect formation) can be critical during the sample preparation and testing. Techniques for thermal and chemical expansion measurements will be presented together with challenges associated with analysis and interpretation. A short overview of the literature data on the expansion in proton-conducting ceramics will be provided. While all these measurements are performed in a single atmosphere, it is important to predict the expansion with different gas compositions on both sides of the membrane, thus representing real device applications. To do so, we developed a computational model based on a Nernst-Planck-Poisson formulation and included a chemo-thermo-mechanical component. Examples of crack formation due to uncontrolled hydration on symmetrical cells (BZCY-NiO//BZCY//BZCY-NiO) prepared by tape-casting will be shown.
Authors : Edith Bucher (1), Christian Berger (1), Judith Lammer (2), Werner Sitte (1)
Affiliations : (1) Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria; (2) Institute of Electron Microscopy and Nanoanalysis (FELMI), Graz University of Technology & Graz Centre for Electron Microscopy (ZFE), Steyrergasse 17, A-8010 Graz, Austria
Resume : Perovskites from the La1-xSrxCo1-yFeyO3-δ series are promising materials for solid oxide cell air electrodes. However, Sr-segregation and reaction with acidic impurities lead to significant long-term degradation. Thus, research efforts are directed towards the development of alternative materials with a weak driving force for cation-segregation, low basicity, and excellent mass- and charge transport properties. Recently, promising results were obtained for La0.8Ca0.2FeO3-δ, which shows fast oxygen exchange kinetics and good long-term stability. In the present study, we explore the effects of Nd-substitution on structure-property relations in the La0.8-xNdxCa0.2FeO3-δ series in order to further optimize the mass- and charge transport properties and long-term stability. Single-phase orthorhombic perovskites (space group Pnma) were obtained in the range 0≤x≤0.6. Atomically resolved STEM-EDX maps confirm that La, Nd, and Ca are distributed homogeneously on the A-site. As expected from considerations of the ionic radii, increasing Nd-substitution leads to a decrease in unit cell volume. The orthorhombic/trigonal phase transition, which is observed for x=0 at approx. 750°C, is suppressed for x≥0.1. A maximum in the electronic conductivity was observed for x=0.1-0.2, whereas the thermal expansion coefficient and the oxygen nonstoichiometry are nearly independent of x at 0.1≤x≤0.6. First results on the oxygen exchange kinetics of LNCF (x=0.6) show high activity towards oxygen reduction.
Authors : Ho-Il Ji, Hyegsoon An, Byung-Kook Kim, Ji-Won Son, Jong-Ho Lee
Affiliations : Center for Energy Materials Research, Korea Institute of Science and Technology, Seoul, Republic of Korea
Resume : Proton conducting ceramic electrolyte possesses attractive features – higher ionic conductivity than oxygen ion conductor and lower activation dependency on the temperature – and enables SOFCs to operate at lower temperatures (400 – 600oC). In addition, higher fuel utilization and carbon coking resistance can be achieved. However, crucial technical challenges on cell fabrication, especially establishing a chemically homogeneous and physically thin electrolyte layer, have been limiting its commercial implementation. These challenges mainly stem from the refractory nature of the proton-conducting electrolytes. It makes the densification behavior of the electrolyte in PCFCs difficult to control and in most cases, negatively impacts on its ionic conductivity. As a result, protonic ceramic fuel cells has been demonstrated a frustrating performance and scalability (an anode support size of at most 3cm^2). Here, we present breakthroughs in the performance and scalability of PCFCs: a high peak power density of 1.3 W/cm^2 in a size of 5x5 cm^2 was obtained at 600°C. The advances stem from an anode-assisted facile densification of a proton-conducting electrolyte on a structurally and compositionally uniform anode support. We show that an internal supply of sintering aid from the anode to the electrolyte as well as an excess shrinkage force driven by the anode effectively promote the densification of the very thin electrolyte (less than 5 μm thick) of BaCe0.55Zr0.3Y0.15O3-δ at much lower temperature of 1350°C while retaining initial chemical composition, leading to a low area-specific ohmic resistance of 0.09 ohm·cm^2. Furthermore, since all of the utilized fabrication processes are cost-effective, consistent, and readily scalable, our results fulfill the requirements of high performance, scalability, and cost efficiency for achieving commercial feasibility of PCFCs as cooler ceramic fuel cells.
Authors : Torrell M1, Pesce A.1, Hornés A. 1, N. Kostretsova, Núñez M. 1, Morata A. 1, Tarancón A. 1,2
Affiliations : 1 IREC, Catalonia Institute for Energy Research, Jardins de les Dones de Negre 1, 2ºpl, 08930 Sant Adrià de Besòs, Barcelona, Spain 2 ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain
Resume : 3D printing of ceramic functional materials has been a breakthrough for ceramic manufacturing technologies. Additive manufacturing allow to generate complex designs while reducing the wasted material bringing clear advantages in terms of functional ceramic materials fabrication. This freedom of design allows to propose high surface area geometries for the electrolytes. Performances of energy devices such as Solid Oxide Cells (fuel cell and electrolyser) show a direct dependence with their active surface area. In this work, yttria stabilized zirconia electrolytes of solid oxide fuel cells and electrolysers have been produced by additive manufacturing technology (SLA) and electrochemically tested. Here presented approach propose new complex geometries of the electrolytes that enhance the active surface (ca. +60%) per projected area. The produced cells show improvements of the final performance (maximum power density and injected current) proportional to the promoted enhance of the area by using the advantages og the 3D printing. The study of the I-V polarizations curves, on SOFC and SOEC modes, and the electrochemical impedance spectroscopy (EIS) results are presented to discuss the described improvements.
Authors : Hyungjun Lee, Kangchun Lee, Seungcheol Myeong, Hoyeon Jung, Ganggyu Lee, Heesung Yoon, Ungyu Paik
Affiliations : Department of Energy Engineering, Hanyang University, Seoul, Republic of Korea, 133-791
Resume : Introducing cathode materials with high oxygen reduction reaction (ORR) activity is one of the best ways to lower the operating temperature of solid oxide fuel cells with sustaining high performance. La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) can be a candidate with high ORR activity, but it reacts with yttrium-stabilized zirconia (YSZ) electrolyte, forming an insulating layer. As a result, forming a gadolinium-doped ceria (GDC) barrier layer is essential. Problems still remain such as delamination due to discrepancy of thermal expansion coefficient between YSZ electrolyte and GDC barrier layer, the formation of insulating layer at the high annealing temperature. In this study, we describe a well-designed structure with a thin GDC barrier layer and a nano-web-structured LSCF thin-film layer (NW-LSCF) via introducing a facile spin-coating method. A dense GDC barrier layer with a thickness of approximately 400nm was coated on a YSZ electrolyte without delamination at a low annealing temperature. In addition, the introduction of NW-LSCF layer enhanced ORR owing to an increased triple-phase boundary length. Cells employing a GDC barrier layer and NW-LSCF interlayer showed excellent electrochemical performance and stable operating behavior. The peak power density reached 2.14 W/cm2 and the voltage degradation rate measured under galvanostatic mode was below 0.025% per hour at an operating temperature of 650oC.
Authors : Navarrete, L.* (1), Sanchis-Sebastiá, M. (2) & Serra, J.M. (1). * firstname.lastname@example.org
Affiliations : (1) Instituto de Tecnología Química (Universitat Politècnica de València – Consejo Superior de Investigaciones Científicas), Av. Los Naranjos, s/n, 46022 Valencia, Spain. (2) Department of Chemical Engineering, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
Resume : Global warming and its consequences over environment have boosted the investigation of alternative energy sources for the reduction of CO2 emissions, and consequently, the dependence on fossil fuels. In addition, the scientific community efforts have focused on the CO2 transformation into added value chemicals and fuels. H2 is a flexible energy carrier and can be produced from water, with a low CO2 footprint. Among the technologies employed for H2 production, water electrolysis, is an efficient, green and commercial technology and if combined with CO2 electrolysis comes up as promising clean route for synthetic fuel production, such as CH4. Thus, in this work we have evaluated CH4 production via co-electolysis focusing on the selection of the most suitable catalyst for a high CH4 yield. Firstly, Ce0.9Gd0.1O2-δ-Ni (GDC-Ni) composite electrode was developed to ensure a proper electronic and ionic conductivity, and to guarantee a good porosity and electrode-electrolyte adhesion. In that direction, different Ce0.9Gd0.1O2-δ:Ni ratios and sintering temperatures were assessed. In a second step, a fixed-bed reactor was employed for the methane catalyst selection. The GDC-Ni powder was impregnated with different metal (Cr, Cu, Ni, Rh, Ru, Pd and Mo) precursors and tested in the co-electrolysis conditions to select the catalyst with the highest yield and selectivity to CH4. Finally, a fully-assembled co-electrolysis cell consisting of Sc doped Yttria as electrolyte and GDC-Ni and LSM-GDC as cathode and anode, respectively, was manufactured. Different current densities and temperatures were selected to study the methane production. The exhaust gas was monitored by a mass spectrometer and gas chromatograph.
Authors : Tatsumi Ishihara, Zhe Tan, Atsushi Takagaki
Affiliations : Department of Applied Chemistry, Faculty of Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan; International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
Resume : Micro-tubular type solid oxide fuel cells are considered as the advantage of short gas sealing line and higher thermal stability. A micro-tubular type solid oxide cell was prepared by using a tubular type NiO-Y2O3 stabilized ZrO2 (NiO-YSZ) fuel electrode substrate and La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) electrolyte film which was prepared by dip-coating and co-sintering method. Since IR loss and overpotential was still larger than those expected, the effects of insertion Ni-based fuel electrode functional layer on NiO-YSZ tubular substrate and rare earth oxide infiltration into NiO-YSZ tube was further studied. The result indicated that the cell using Ni-Fe functional layer and infiltration of CeO2 into the substrate shows a higher maximum power density. The electrolysis performance of the prepared tubular cell under reversible operation was also studied. The reasonably large current density was also realized in electrolysis mode on the optimized cell. The results indicated that the cell using CeO2 infiltration and Ni-Fe layer was highly effective for increasing the power density due to much decreased IR loss and overpotential of fuel electrode, in particular at low temperature. In addition, cyclic SOFC and SOEC operation, which means SORC performance was also successfully demonstrated.
Interface & Surface Phenomena (III) : Igor Lubomirsky
Authors : David S. Mebane
Affiliations : Department of Mechanical and Aerospace Engineering, West Virginia University
Resume : This presentation will survey the continuing controversy surrounding the modeling of surfaces and interfaces in ionic conductors, and will move beyond it to a discussion of the feasibility of device-scale models incorporating microscopically accurate, nanoscale depictions of solid state electrochemical interfaces. Microscopic evidence makes it clear that dilute-solution theories cannot be trusted in concentrated ionic solutions, where 'concentrated' refers to anything greater than approximately one mole percent. The results of a quantitative analysis of a microscopic dataset and corresponding statistical comparison of dilute-case theories vs. those incorporating concentrated solution thermodynamics will be presented. Devices based on ionic materials -- such as high temperature fuel cells and electrolyzers -- require accurate models of interfaces that control ionic conductivity and where rate-limiting reactions take place. Device-scale models of ceria-based electrolyzers for carbon dioxide with nanoscale interface models are now in development at West Virginia and the latest results will be presented.
Authors : Alexander K. Opitz (1), Andreas Nenning (1), Cornelia Bischof (2), Matthias Gerstl (1), Jürgen Fleig (1), Martin Bram (2)
Affiliations : (1) TU Wien, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; (2) Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-1), 52425 Jülich, Germany
Resume : Nickel/gadolinia-doped ceria (Ni/GDC) is the currently most promising alternative fuel electrode material for solid oxide fuel and electrolysis cells. For a targeted optimisation of real porous Ni/GDC cermet electrodes, a detailed insight into the role of the material properties for the electrochemical polarisation resistance is crucial. Here, model-composite GDC thin film electrodes with embedded current collectors were used in the first step to characterize the electrochemical elementary parameters of this material. In the second step, the results from model experiments are transferred to the interpretation of the impedance of porous cermet electrodes. Analytic fits of the electrode impedance are done by using a transmission line circuit, which reflects the physically correct relationship of the relevant elementary processes on Ni/GDC cermet electrodes. With this approach, it is possible to separate and quantify the individual contributions to the electrode polarisation resistance, such as oxygen ion transport across the electrolyte/GDC interface, ionic conductivity within the porous Ni/GDC electrode, and oxygen exchange at the GDC surface. Comparison with our model studies yields very good quantitative agreement. With these detailed insights, we can quantitatively explain the excellent performance of real porous Ni/GDC fuel electrodes, which is enabled by the mixed ion/electron conduction of GDC and a microstructure with small GDC and large Ni grains.
Authors : Ozden Celikbilek (1), Andrea Cavallaro (1), Gwilherme Kerherve (1), Ainara Aguadero (1), John A. Kilner (1,2), Stephen J. Skinner (1)
Affiliations : (1) Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP, United Kingdom (2) International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
Resume : Thin-films deposited by Pulsed Laser Deposition (PLD) have enabled the fabrication of cathodes for solid oxide cells (SOC) to possess various microstructures, crystalline states and surface chemistry. These films are often subjected to various post-thermal treatments which influence the chemical activity and stability of the films. Here, we investigate how the catalytic activity is affected by the thermally induced surface restructuring in complex transition metal oxides, in particular, La0.6Sr0.4CoO3-δ (LSC) thin films grown by PLD. To this end, the influence of substrate temperature during PLD as well as post-annealing treatments on the film microstructure and surface chemistry were studied. In comparison to high-temperature grown films, the post-annealed low-temperature grown ones showed 2-times lower degradation rate in long-term electrochemical tests at 500 °C. The differences in the electrochemical activity were found to be related to the initial microstructure and morphology of the films. After long-term tests at 500 °C, the low-temperature grown film showed localised Sr-segregation into protruding particles, leaving the remaining surface with catalytically active stoichiometry. On the other hand, the high-temperature grown films showed a fully covered surface with Sr-rich particles, which continued to thicken with time. Here we emphasise the importance of thermal treatments on catalytic activity and stability of the SOC electrode films and propose that it should be considered as among the main pillars in the design of the active surface.
Authors : Vincent Thoréton(1)*, Tor Svendsen Bjørheim(1), Xin Liu(1), Zuoan Li(2), Reidar Haugsrud(1)
Affiliations : (1) Centre for Materials Science and Nanotechnology (SMN), University of Oslo, Gaustadalléen 21, NO-0349, Norway. (2) SINTEF Industry, Sustainable Energy Technology, P.O. Box 124, Blindern,0314 Oslo, Norway.
Resume : Efficient Solid Oxide Cells (SOCs) require fast kinetics of the Oxygen Reduction Reaction (ORR) or Oxygen Evolution Reaction (OER) at the air electrode. The surface kinetics is affected by both intrinsic and extrinsic factors such as doping type and level, surface composition, applied potential and composition of the surrounding atmosphere. In particular, the interaction of oxygen-bearing molecules from the feed gas with the electrode surface is relevant to understand . One step is the interaction of water vapour with the air electrode since water is omnipresent in most situations and yields to diverse reactivity. In this work, we investigated the effect of humidity on the surface exchange kinetics of CaTi0.9Fe0.1O3-δ (CTF). The transport parameters were determined, and surface reaction mechanisms were investigated by isotopic exchange-gas phase analysis. Overall, water vapour exchanges more rapidly than oxygen, but there is seemingly no direct effect of humidity on the oxygen exchange kinetics of CTF between 800 and 600˚C. However, exposure to water gradually degrades the surface microstructure lowering the oxygen exchange kinetics. The results were compared to those of other electrode materials and discussed in terms of bulk/surface defect chemistry. Acknowledgements The authors acknowledge financial support from the national funding organizations (Research Council of Norway, NWO, MINECO) in the framework of the M-ERA.NET project (grant number 258875) "Designing rules for enhancing SURface KINetics in functional OXides for clean energy technologies (SURKINOX). The authors would also like to acknowledge sup- port of the FRINATEK project 262393 ‘‘Fundamentals of Surface Kinetics in High Temperature Electrochemistry’’ (FUSKE) of the Research Council of Norway.
Authors : Christian Berger (1), Judith Lammer (3), Edith Bucher (1), Werner Grogger (3), Rotraut Merkle (2), Joachim Maier (2), Werner Sitte (1)
Affiliations : (1) Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria (2) Max Planck Institute for Solid State Research, Heisenbergstraße 1, DE-70569 Stuttgart, Germany (3) Institute of Electron Microscopy and Nanoanalysis (FELMI), Graz University of Technology & Graz Centre for Electron Microscopy (ZFE), Steyrergasse 17, A-8010 Graz, Austria
Resume : Mixed proton-, oxygen ion- and electron-conducting ceramics such as self-generated nanocomposites from the BaCeO3-δ-BaFeO3-δ system  offer attractive options for application in protonic ceramic fuel and electrolyser cells or hydrogen separation membranes. In the present work, partial substitution of Ce and Fe by Y in the BaCeO3-δ BaFeO3-δ system is investigated to further increase the proton uptake and gain a deeper understanding of the interrelation between chemical composition and oxygen-/proton-exchange processes. The precursor BaFe0.4Ce0.4Y0.2O3-δ was synthesised via a sol-gel process. After thermal treatment, a composite of a cubic (Pm-3m) Fe-rich and a trigonal (R-3c) Ce-rich perovskite was obtained. With increased annealing temperature, the fraction of the cubic phase increases (reaching 98 wt-% at 1370°C) and lattice parameters change systematically. Analytical scanning transmission electron microscopy is used to determine the distribution of both phases and their local cation stoichiometry. The water uptake measured by thermogravimetry shows characteristic differences depending on cation composition between the homogeneous BaFe0.4Ce0.4Y0.2O3-δ perovskite and 2-phase composites. These results will be related to water incorporation trends and deviations from ideally dilute defect chemistry observed for (Ba,Sr,La)FeO3-δ perovskites .  S.Cheng et al., Angew. Chem. Int. Ed. 2016, 55, 10895.  R.Zohourian et al., Adv. Funct. Mat. 2018, 28, 1801241.
Authors : Wolfgang Preis
Affiliations : Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben, Austria
Resume : The performance of mixed conducting oxides, such as cathode materials for solid oxide fuel cells, is strongly correlated with oxygen exchange processes between the gas phase and the ceramic oxide which can be described by oxygen diffusion as well as the surface exchange reaction. The long-term stability of cathode materials is highly affected by the occurrence of inert surface particles blocking the surface exchange reaction. Amongst others, conductivity relaxation experiments are a powerful tool for the investigation of the oxygen exchange properties. It is the aim of this contribution to present finite element modeling (FEM) of relaxation curves for ceramic samples as a function of surface coverage of inert particles. In particular, the effect of the particle shape as well as size distribution is studied in detail. Basically, the FEM simulations have been carried out on thick (0.05 cm) as well as thin samples (0.5 – 5 µm). A bimodal distribution of the surface particles is accomplished by a combination of large particles (100 µm) with significantly smaller particles (1 – 17 µm). In addition, large particles (100 µm) combined with particles of comparable size (20 – 40 µm) have been investigated. Moreover, the effect of surface particles with a square shaped cross-section as well as a rectangular cross section has been taken into account. Interestingly, the oxygen exchange kinetics is affected by flux constriction especially in the case of fairly large particle sizes.
Authors : Filip Podjaski (1 2), Daniel Weber (1 3), Siyuan Zhang (4), Leo Diehl (1 3), Roland Eger (1), Viola Duppel (1), Esther Alarcon-Llado (5), Gunther Richter (6), Frederik Haase (1 3) Anna Fontcuberta i Morral (2 7), Christina Scheu (4), Bettina V. Lotsch (1 3 8 9)
Affiliations : (1) Max-Planck-Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany. (2) Laboratory of Semiconductor Materials, Institute of Materials, Faculty of Engineering, Ecole Polytechnique Fédérale de Lausanne, Station 12, 1015 Lausanne, Switzerland. (3) Department of Chemistry, University of Munich (LMU), Butenandtstraße 5-13, 81377 München, Germany. (4) Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany. (5) AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands. (6) Max-Planck-Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany. (7) Institute of Physics, Faculty of Basic Sciences, EPFL, 1015 Lausanne, Switzerland. (8) Center for Nanoscience, Schellingstraße 4, 80799 München, Germany. (9) Cluster of Excellence e-conversion, Munich, Germany.
Resume : Power-to-gas technologies are on the way to become economically viable in order to make more use of fluctuating renewable energy, but the rational design of hydrogen evolution reaction (HER) electrocatalysts that are competitive with platinum remains to be an outstanding challenge. We present the delafossites PdCrO2, PdCoO2 and PtCoO2 as a new family of highly efficient electrocatalysts for the HER in acidic media and show that the reductive operation can modify their surface and hence, the catalytic performance in different ways. For PdCoO2, the inherently strained Pd metal sublattice acts as a pseudomorphic template for the growth of a tensile strained Pd rich capping layer that ranges up to 400 nm, far beyond epitaxial methods. Its formation continuously improves the electrocatalytic activity by simultaneously increasing the exchange current density j0 and by reducing the Tafel slope down to 38 mV/decade, leading to overpotentials η_10< 15 mV for 10 mA/cm², superior to bulk platinum. We attribute these effects to the strain facilitated operando formation of a β-palladium hydride phase with drastically enhanced surface catalytic properties with respect to bulk or nanostructured palladium. These findings illustrate how operando induced electrochemical modifications can be used as a long ranging top-down design concept for rational surface and property engineering through the strain-stabilized formation of catalytically active phases. F. Podjaski et al. ”Rational strain engineering in delafossite oxides for highly efficient hydrogen evolution catalysis in acidic media.” Nat. Catal. (2019) doi:10.1038/s41929-019-0400-x
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Solid State Energy Devices (IV): Solid Oxide Cells : JTS Irvine
Authors : R. Merkle,1 M. F. Hoedl,1 G. Raimondi,1 E. A. Kotomin,1,2 J. Maier,1
Affiliations : 1 Max Planck Institute for Solid State Research, Stuttgart, Germany 2 Institute of Solid State Physics, University of Latvia, Riga, Latvia
Resume : Cathode materials for protonic ceramic fuel cells (PCFC) require sufficient proton conductivity to extend the reaction zone beyond the three phase boundary. The hydration thermodynamics of BaFeO3-d-related perovskites was studied by thermogravimetry. Despite a high oxygen vacancy concentration, the degree of hydration is lower for cathode materials compared to Ba(Zr,Y)O3-x electrolytes. A partial substitution of iron by redox-inactive, oversized Zn2+ or Y3+ drastically increases the proton uptake. Measurements of oxygen nonstoichiometry and proton uptake indicate pronounced deviations from ideally dilute defect chemistry (hole-hole and hole-proton defect interactions). Based on DFT calculations and EXAFS/XRS measurements, these interactions are related to the partial delocalization of holes from iron to adjacent oxygen ions, which in turn disfavors protonation. Proton mobilities are estimated from stoichiometry relaxation experiments. The obtained detailed defect-chemical understanding serves as the basis for PCFC cathode optimization, in particular since proton uptake, catalytic activity, electronic conductivity, and stability show conflicting trends.  R. Zohourian, R. Merkle, G. Raimondi, J. Maier, Adv. Funct. Mater. 28, 1801241 (2018)  M.F. Hoedl, D. Gryaznov, R. Merkle, E. A. Kotomin, J. Maier, submitted  G. Raimondi, A. Chiara, F. Giannici, R. Merkle, J. Maier, in preparation We thank GIF (I-1342-302.5/2016) for financial support
Authors : Giulia Raimondi (1), Alessandro Chiara (2), Francesco Giannici (2), Alessandro Longo (3), Chiara Cavallari (3), Antonino Martorana (2), Rotraut Merkle (1), Joachim Maier (1)
Affiliations : (1) Max Planck Institute for Solid State Research, Physical Chemistry of Solids, Stuttgart, Germany. (2) Universita’ degli Studi di Palermo, Dipartimento di Fisica e Chimica, Palermo, Italy. (3) European Synchrotron Radiation Facility, Grenoble, France.
Resume : BaFeO3-δ perovskites with mobile oxygen vacancies, holes, and protons, can be used as cathode material for Protonic Ceramic Fuel Cells (PCFC). Their mixed conductivity including protons is important to activate the whole cathode surface for the oxygen reduction. The proton concentration in such cathode perovskites was determined by thermogravimetry. [1,2] Crystal structure, symmetry and local lattice distortions have an important impact on the proton uptake. Partial substituion of Fe by redox-inactive and oversized Zn2+ or Y3+ is beneficial for proton uptake.  This can be assigned to local lattice distortions decreasing the covalency of Fe-O bonds, and thus enhancing the basicity of oxygen ions. The local environment and bonding of the cations and of O2- is probed using Extended X-Ray Absorption Fine Structure (Fe,Zn,Y K-edges) and X-Ray Raman Scattering (O K-edge) for oxidized ("Fe4+"), reduced ("Fe3+") and hydrated samples. The rather small Fe edge shift between reduced and oxidized samples and strong pre-edge features at the O K-edge indicate that electron holes are largely delocalized to oxygen states.  Together with the EXAFS analysis of the lattice distortions without and with Zn2+ ,Y3+ , this yields a comprehensive understanding of proton uptake in PCFC cathodes, and indicates possibilities to optimize them.  D.Poetzsch et al. Phys.Chem.Chem.Phys.16,16446(2014)  R.Zohourian et al. Adv.Funct Mater.28,1801241(2018)  G. Raimondi et al., to be submitted
Authors : Ragnar Strandbakke(1)*, Tor Bjørheim(1), Magnus H Sørby(2), Iga Szpunar(3),Sebastian Wachowski(3), Aleksandra Mielewczyk-Gryń(3), María Balaguer(4), Patricia Almeida Carvalho(5) and Truls Norby(1)
Affiliations : (1) University of Oslo, Dept. Chemistry, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway (2) Inst. for Energy Technology, Department of Physics, P.O. Box 40 Kjeller, NO-2027, Norway (3) Gdańsk University of Technology, Faculty of Applied Physics and Mathematics, Solid State Physics Department, Narutowicza 11/12, 80-233 Gdansk, Poland (4) Instituto de Tecnología Química (Universidad Politécnica de Valencia − Consejo Superior de Investigaciones Científicas), Av. Naranjos s/n, E-46022 Valencia (SPAIN) (5)SINTEF Materials and Chemistry, PB 124, Blindern, NO-0314 Oslo, Norway
Resume : Hydration of double perovskite (DP) BaLnCo2O6-δ for a large range of lanthanides is investigated by Thermogravimetry (TG), Secondary Ion Mass Spectroscopy (SIMS), Neutron Diffraction (ND), and atomistic modelling. The relationship between structure, electronic configuration, and cation composition is investigated by use of ND, Synchrotron Radiation Powder X-ray Diffraction (SR-PXD), X-ray Photoelectron Spectroscopy (XPS), and Scanning Transmission Electron Microscopy (STEM). Incorporation of protons in the hydrating DP compositions is a sluggish, multi-step process involving oxidation or reduction, depending on temperature and atmosphere / atmospheric history. Conductivity measurements in combination with TG with H2O/D2O exchange give indications of the proton incorporation mechanism and the interplay between electronic states and hydration. XPS gives information about electronic states, SIMS gives concentration profiles of 2H from surface to bulk, and STEM shows cation disorder upon hydration and gives indication of charge ordering in the Co layers, possibly affecting the stability of protons through the basicity of the adjacent oxide ions. The screening of lanthanides has given a new insight to the prerequisites for incorporation of protons in DP cobaltites suitable as electrode materials in Proton Ceramic Electrochemical Cells. Financial and scientific contributions from the Research Council of Norway (Grant nᵒ 272797 “GoPHy MiCO”) through the M-ERA.NET Joint Call 2016.
Authors : Nicholas J. Williams, Stephen J. Skinner
Affiliations : Imperial College London
Resume : Accepter doped ceria, Ce1-xRExO2-d, where RE = rare earth, has been widely investigated for its oxide-ion and electronic conduction properties, while the transport of other ionic charge carrier species is less well understood. The diffusivity and surface catalytic properties of oxide-ions and protons has been investigated by means of isothermal isotopic exchange depth profile using secondary ion mass spectrometry (IEDP-SIMS) and electrochemical impedance spectroscopy (EIS). Over an intermediate temperature range (500 – 800oC), diffusion analysis has identified that tracer exchange and transport rates of the protonic species were dependent on both the pH2O and pO2 of the exchange atmosphere. The EIS and exchange data were found to be in excellent agreement. This paper will therefore discuss the fundamental and novel mechanistic insights into the solid/gas interfacial kinetics and ion transport through rare earth doped ceria.
Authors : M. A. Morales-Zapata, M. A. Laguna-Bercero
Affiliations : Instituto de Ciencia de Materiales de Aragón, c/ María de Luna 3, 50018 Zaragoza, Spain
Resume : Pr2NiO4-δ (PNO) and Ce0.9Gd0.1O2-δ (CGO) oxide mixtures have been tested in symmetrical cells by electrochemical impedance spectra (EIS) measurements at temperatures between 700°C and 850°C. As previously reported, PNO-CGO mixtures react at the typical SOFC sintering temperatures forming CPGO (praseodymium and gadolinium doped ceria). In despite of this in situ reaction, low polarization resistances can be achieved. The lowest polarization resistance was found for samples with 80 vol%. PNO-20 vol% CGO, showing polarization resistance values of about 0.16 Ωcm2 at 850°C. In addition, chemical diffusion (Dchem) and surface exchange (kex) coefficients of oxygen on mixed PNO and CGO oxides, were investigated using the electric conductivity relaxation technique (ECR) at different intervals of partial oxygen pressures (pO2) in temperature ranges between 600°C to 850°C. Changes in rate performance are observed as a result of heat treatment, which is manifested through variations in kex and their activation energies. Single cell electrochemical performance under SOFC and SOEC will be also shown. These findings confirm that PNO-CGO mixtures, forming mainly PCGO compositions, are presented as excellent candidates for SOC applications.
Authors : Simone Anelli1, Federico Baiutti1, Aitor Hornés1, Lucile Bernadet1, Marc Torrell1, Albert Tarancón1,2
Affiliations : 1IREC, Dept. Advanced Materials for Energy, Jardins de les Dones de Negre 1, 08930 Barcelona (Spain) 2ICREA, 23 Passeig Lluís Companys, 08010 Barcelona (Spain) Corresponding Author: email@example.com
Resume : The utilization of mesoporous CGO came to the fore as scaffold material for Solid Oxide Cell (SOC) applications, because of its ability to furnish a high surface-active area (BET~100m2/g). The large pore volumes and good thermal stability are essential prerequisites to design optimal infiltration of the scaffold by mixed ion-electron conductor (MIEC) perovskites such La1-xSrxCo1-yFeyO3-δ (LSCF).  However, the mesoporous CGO scaffolds suffer of some drawbacks like SiO2 contamination, derived by the followed nanocasting hard template method by KIT 6.  In addition, the fabrication process is limited by the sintering temperature of the scaffold that can promote the collapse of the nanostructure.  A twofold strategy is proposed to overcome the presented issues: firstly, the removal of residual silica by an optimized chemical etching process leading to an improvement of the ionic conductivity of the scaffold. Secondly, the use of Co oxide nanoparticles as sintering aid allows a fine tune of the sintering temperature that ensures the attaching maintaining a nanostructured scaffold. The effectiveness of this approach was demonstrated by a series of complementary techniques such: SEM, XRD, SAXS, ICP-MS, BET, TPR and by impedance spectroscopy measurements. A complete SOC was electrochemically measured to prove such enhancements in terms of performances. 1 E. Hernández, F. Baiutti, A. Morata, M. Torrell and A. Tarancón, J. Mater. Chem. A, 2018, 6, 9699–9707. 2 P.-S. Cho, Y. H. Cho, S.-Y. Park, S. B. Lee, D.-Y. Kim, H.-M. Park, G. Auchterlonie, J. Drennan and J.-H. Lee, J. Electrochem. Soc., 2009, 156, B339. 3 L. Almar, T. Andreu, A. Morata, M. Torrell, L. Yedra, S. Estradé, F. Peiró and A. Tarancón, J. Mater. Chem. A, 2014, 2, 3134. 4 S. Anelli, F. Baiutti, A. Hornés, L. Bernadet, M. Torrell and A. Tarancón, J. Mater. Chem. A, 2019, 3, 10031–10037.
Authors : Werner Sitte (1), Christian Berger (1), Andreas Egger (1), Edith Bucher (1), Rotraut Merkle (2), Joachim Maier (2)
Affiliations : (1) Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Straße 18, A-8700 Leoben, Austria (2) Max Planck Institute for Solid State Research, Heisenbergstraße 1, DE-70569 Stuttgart, Germany
Resume : Within the Ruddlesden-Popper (RP) series Lnn+1BnO3n+1, the first order (n=1) RP-type rare earth nickelates with Ln=La, Nd, Pr and B=Ni are known for their high oxygen diffusivities as well as good electronic as well as ionic conductivities. A drawback for their application as air electrode in solid oxide fuel and electrolyser cells is the low oxygen surface exchange kinetics. In order to improve this property, partial substitution of Ni by Co on the B-site in Pr2NiO4+δ (PNO) was recently investigated . Electrochemical impedance spectroscopy (EIS) measurements were performed on microelectrodes fabricated from dense thin films to obtain oxygen surface exchange rates of Pr2NiO4+δ and Pr2Ni0.9Co0.1O4+δ between 550 and 800°C. Compared to Pr2NiO4+δ, Pr2Ni0.9Co0.1O4+δ showed increased oxygen surface exchange rates especially at lower oxygen partial pressures . In order to understand the oxygen nonstoichiometry δ of Pr2NiO4+δ and Pr2Ni0.9Co0.1O4+δ as function of pO2 and T, a defect chemical analysis was performed for both compounds. Cell tests with Pr2Ni0.9Co0.1O4+δ / GDC composites as SOEC air electrode on anode supported cells were performed for water electrolysis up to current densities of 1000 mA cm-2 at 800°C.  C. Berger et al., Solid State Ionics 2018, 316, 92.  C. Berger et al., J. Electrochem. Soc. 2019, 166 (14), F1088.
New Phenomena and devices : Susanne Hoffmann-Eifert
Authors : Vincenzo Esposito
Affiliations : Department of Energy Conversion and Storage, Technical University of Denmark (DTU), Kgs. Lyngby 2800, Denmark
Resume : Highly oxygen defective ionic metal oxides fluorites such, as ceria and bismuth oxides, are sustainable, non-classical electrostrictors with properties that are superior to lead-based piezoelectric metal oxides. Here, we report recent findings underlying the exceptional electromechanical performances of such materials, both as bulk ceramics and thin films. We especially highlight the effect of dopants, microstructure, and crystallography on low-temperature actuation. We also show how the materials perform in the nanoscale and how these impact micro/nano-electromechanical system´s design and some related technologies.
Authors : Alejandro Fernández-Rodríguez1, Jordi Alcalà1, Jordi Suñe2, Anna Palau1 and Narcis Mestres1
Affiliations : 1. Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain 2. Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
Resume : Memristive devices are attracting a great deal of attention for memory, logic and sensing applications due to their simple structure, high density integration, low-power consumption, and fast operation. In particular, multi-terminal structures controlled by active gates would certainly provide novel concepts for reconfigurable electronic systems with engineered functionality. In this work we will show the potential of reversible field-induced metal-insulator transition (MIT) in strongly-correlated metallic oxides for the design and obtention of multi-terminal memristive transistor-like devices [1, 2]. We have studied the highly correlated cuprate YBa2Cu3O7-δ as a model system, which is able to display non-volatile volume MIT, driven through local oxygen migration. In this way, vertical and lateral oxygen mobility may be modulated, at the micro- and nano-scale, by tuning the applied bias voltage and operating temperature. The key advantage of this material is the possibility to homogeneously modulate the oxygen vacancy diffusion not only in a confined filament or interface, as observed in widely explored insulating strongly correlated oxides, but also toward the whole film thickness. We will show different device configurations in which the lateral conduction of a bridge is controlled by active gate-tunable volume resistance changes. Large design flexibility can be obtained by changing the switching performance of different gates, thus offering the possibility to locally adjust the conductance response as required for non volatile memories and neuromorphic functionalities. References  A. Palau et al. ACS Applied Materials & Interfaces. 10, 30522, 2018  J.C. Gonzalez-Rosillo et al. Adv. Elect. Mater. 1800629, 2019
Authors : Evgeniy Makagon, Eran Mishuk, Ellen Wachtel, Sidney R. Cohen, Yuanyuan Li, Junying Li, Anatoly Frenkel, Igor Lubomirsky
Affiliations : Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel; Department of Chemical Research Support, Weizmann Institute of Science, Rehovot Israel; Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, USA;
Resume : The chemo-mechanical effect in solids refers to dimensional change due to change in stoichiometry. Dimensional change due to electrochemically-induced compositional change has been termed the electro-chemo-mechanical (ECM) effect. The chemical instability inherent in this effect is clearly deleterious for batteries or fuel cells, but, as recently suggested, has potential for use in actuation. The structure of the actuator device that operates on the ECM principle is a micrometer thick solid electrolyte (SE) sandwiched between two ECM-active layers (ActLs). An electrochemical reaction must occur in these layers, causing them to expand or contract. In order to facilitate the ECM response, these layers must have mixed ionic and electronic conductivity and a large chemical expansion coefficient. We have constructed a thin film, ECM actuator comprising 20mol% Gd doped CeO2 (20GDC) as the SE and [Ti oxide\20GDC] composite as the ActL. Selected area electron diffraction measurements showed the composite to be nanocrystalline, a morphology that enables interfacial oxygen ion diffusion. Synchrotron X-ray absorption measurements of the ActL identified the chemical composition to be a mixture of Ce3 /Ce4 and Ti3 /Ti4 oxidation states. The deformation of the ECM actuator was determined to be in the bending regime producing large vertical displacements (~2 μm) and more than ~8 MPa stress.  J. G. Swallow et al., Nat. Mater. (2017) 16, 749
Authors : Alexander Viernstein, Maximilian Morgenbesser, Markus Kubicek, and Jürgen Fleig
Affiliations : Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9/164-EC, 1060 Vienna, Austria
Resume : Wide band gap semi-conductors such as SrTiO3 (STO) have attracted high interest for photoelectrochemical water splitting and as part of photovoltaic cells. However, the impact of UV irradiation on the composition (e.g. the oxygen content) of STO and Fe doped STO (Fe:STO) at elevated temperatures has hardly been studied. In this contribution, we show that exposure to UV light at ca. 350 °C in air causes a filling of oxygen vacancies in STO. An chemical potential equal to a p(O2) in the range of GPa can be realized in Fe:STO. Due to this oxygen incorporation and subsequent electron hole formation, UV irradiation thus leads to an increase of the in-plane bulk conductivity by up to a factor of 10^3 in STO. These thermodynamic effects but also their kinetic counterparts (chemical diffusion coefficients) were examined in dependency of temperature and p(O2) using an electrochemical oxygen pump. Moreover, space charge effects leading to photovoltages and additional semicircles in the impedance spectra are discussed.
Authors : Sofia De Sousa Coutinho(1), Stéphane Holé(1), David Bérardan(2) , Nita Dragoe (2) and Brigitte Leridon(1)
Affiliations : (1) LPEM, ESPCI Paris, CNRS, Université PSL, Sorbonne Universités, 10 rue Vauquelin, 75005 Paris, France (2) ICMMO, Univ. Paris-Sud, Univ. Paris-Saclay, F-91405, Orsay, France
Resume : A recently discovered family of superionic conductors exhibits colossal equivalent permittivity when the material is placed between two metallic electrodes. This is remarkable because ionic conductors with comparable ionic conductivity usually do not exhibit such huge permittivity. As a matter of fact, these titanium-based lamellar perovskites of general formula M2Ti2O5 where M=Rb,K… are also found to exhibit memristive properties. Systematic measurements have allowed us to track the behavior of the permittivity as function of frequency and temperature in both the Rb and K compounds. We evidenced a maximum in the real equivalent permittivity at around 270 K for the Rb-compound and at 300K for the K-compound, together with Warburg diffusion at low frequency. The variation of the permittivity is correlated to the variation of the ionic conduction, thus pointing to a common origin for both phenomena. We will present here different investigations on the nature of the conducting ions. In particular by measuring the charge distribution inside the sample, we were able to demonstrate that the ions accumulating at the anode are of negative sign and that the material becomes locally conducting on the cathode side, creating a virtuel cathode, which accounts for all observed features. We will then present our latest results and conclusions on the nature of the migrating ions and we will discuss possible applications for this material.
Authors : Lars Heinke
Affiliations : Karlsruhe Institute of Technology (KIT)
Resume : Due to their well-defined, tunable nanoporous structure and their long-range order, crystalline metal-organic frameworks (MOFs) present an ideal model system for the investigation of the ionic mobility under nanoconfinement. Here, the dynamic properties of room-temperature ionic liquids (IL) in the nanopores of MOF thin films are investigated. The experimental data supported by molecular dynamic simulations show that the percentage of pore filling of a prototype IL ([BMIM][NTf2]) in MOFs of type HKUST-1 has a tremendous impact on the dynamic IL properties. The conductivity and ion mobility decreases by three orders of magnitude when the pores of the MOFs are filled with IL. Detailed investigation unveil that mutual pore blockage of the cation and anion results in transient pore jamming, responsible for the conductivity drop. Moreover, it will be presented that photochromic molecules can be incorporated in the MOF structure, resulting in photoswitchable nanoporous materials. There, the ionic conduction of protons[2,3] and ionic liquids in the nanopores can be photomodulated.  A.B. Kanj, R. Verma, M. Liu, J. Helfferich, W. Wenzel, L. Heinke Nano Lett. 19 (2019) 2114-2120.  K. Müller, J. Helfferich, F. Zhao, R. Verma, A.B. Kanj, V. Meded, D. Bléger, W. Wenzel, L. Heinke Advanced Materials 30 (2018) 1706551.  A.B. Kanj, A. Chandresh, A. Gerwien, S. Grosjean, S. Bräse, Y. Wang, H. Dube, L. Heinke Chem. Sci., 2020, DOI: 10.1039/c9sc04926f.
Authors : Dan Zhao1, Mina Shiran Chaharsoughi1, Anna Martinelli2, Andreas Willfahrt1, Diana Bernin2, Magnus P. Jonsson1, Simone Fabiano1, Xavier Crispin1
Affiliations : 1. Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, SE-60174, Norrköping, Sweden 2. Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-41296, Gothenburg, Sweden
Resume : Heat flux and temperature are key parameters to measure in order to regulate any physical, chemical, and biological processes. New emerging technologies, e.g. electronic-skin and interactive buildings, are in the need of accurate temperature or heat flux sensors, that are also mechanically flexible and easily projected onto large areas. Thermopiles can provide accurate and stable heat flux and temperature reading but the technology today is based on inorganic materials that have low Seebeck coefficient (100 µV K–1) and are brittle and difficult to scale up to large areas. Recently, polymer electrolytes have been proposed for thermoelectric devices because the ionic thermodiffusion in such materials can lead to giant ionic Seebeck coefficient. [1, 2] Here we introduce a solid “ambipolar” ionic liquid polymer gel showing a giant negative ionic Seebeck coefficient (-4,000 µV K–1). The Seebeck coefficient can be tuned from negative to positive (up to +14,000 µV K–1) by adjusting the polymer matrix composition. Nuclear magnetic resonance spectroscopy, Raman and infrared spectroscopy analysis shows that the interaction between the ion and the polymer is the key factor in controlling the sign and magnitude of the ionic Seebeck coefficient. The ionic thermodiffusion in the polymer gel can be combined with pyroelectric response to enhance the heat detecting performance.  The presented integrated concept provides both rapid initial response upon heating and stable synergistically enhanced signals upon prolonged exposure to heat stimuli. 1. Zhao, D., Wang, H., Khan, Z. U., Chen, J. C., Gabrielsson, R., Jonsson, M. P., Berggren, M., Crispin, X., Ionic thermoelectric supercapacitor, Energy Environ. Sci., 9, 1450-1457 (2016). 2. Zhao, D., Fabiano, S., Berggren, M., Crispin, X., Ionic thermoelectric gating organic transistors, Nat. Commun., 8, 14214 (2017). 3. Chaharsoughi, M. S., Zhao, D., Crispin, X., Fabiano, S., Jonsson, M. P., Adv. Funct. Mater. 29, 1900572 (2019).
Solid State Energy Devices (VII): Batteries : Francesco Ciucci
Authors : MAURO PASTA
Affiliations : University of Oxford
Resume : The traditional Li-ion chemistry is approaching its physicochemical limit. In order to power up the electro-mobility of the future, a paradigm shift is required at the fundamental materials level. Traditional intercalation electrode materials simply act as host for Li-ions, while in conversion and alloying chemistries they “actively” participate to the charge storage mechanism causing severe volume changes and ultimately poor cycle life. In my talk, I will discuss electro-chemo-mechanical and interfacial challenges common to conversion and alloying materials, using phosphorous, lithium and iron(II) fluoride as model material systems.
Authors : Ieuan D. Seymour* (1), Nicholas S. Grundish (2), Yutao Li (2), John B. Goodenough (2) and Graeme Henkelman (1)
Affiliations : (1) Department of Chemistry and the Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712, United States (2) Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA
Resume : Layered transition-metal (TM) oxides have played a central role as cathodes for Li-ion and Na-ion rechargeable batteries. Alleviating the deleterious structural transitions that occur in these materials during electrochemical cycling is still a critical challenge which requires a fundamental understanding of the mechanisms taking place at the atomistic level. In this work we investigated how Te6+ doping into the AxNiO2 (A=Li and Na) family of materials leads to changes in the local structure and electrochemical performance. The Li-Ni-Te-O system provides a rich phase space in which two layered polymorphs and one disordered rock salt phase can be synthesised. Significant Ni2+ migration occurs in both layered polymorphs which leads to rapid capacity fading. The disordered rock salt structure displayed the highest reversible capacity out of the three polymorphs, which could be rationalised based on the presence of fast Li-transport on the partially ordered Li/Ni sublattice. In the Na-Ni-Te-O system, the inclusion of Te6+ results in the suppression of TM layer shearing during desodiation. Using a combination of X-ray diffraction, solid-state NMR and DFT calculations it can be shown that the improvement of the electrochemical cycling is related to the inclusion of Na ions into the TM layer which suppresses Na-ordering. The conclusions from this work have wider implications for the design of new Li-ion and Na-ion cathode materials.  Grundish et al. Chem. Mater. 31 (2019).
Authors : Edouard Querel, Qianli Ma, Andrea Cavallaro, Federico Pesci, Rowena Brugge, Frank Tietz, Ainara Aguadero
Affiliations : Department of Materials, Imperial College London; IEK1, Forschungzentrum Julich
Resume : Na metal all-solid-state batteries could bring a solution to three objectives for next-generation batteries: an improved safety, a higher energy density and a reduced environmental impact. Safety wise, the absence of an organic liquid electrolyte makes solid-state batteries less flammable; the energy density increase in solid-state batteries originates from the use of high capacity Na metal anodes and high voltage cathodes; the reduced environmental impact comes from the replacement of Li (a limited and geographically poorly distributed resource) by abundant, easily accessible (and therefore cheap) Na. Early work in the field of solid-state batteries has focused on improving the ionic conductivity of solid electrolytes to match the ionic conductivity of liquid electrolytes. Among good Na conducting ceramic solid electrolytes, the family of Na SuperIonic CONductors (NaSICON) of composition Na1 xZr2SixP3-xO12 (0 ≤ x ≤ 3) has long been recognized for its remarkably high ionic conductivity. In recent work, a total ionic conductivity of 5.0 mS.cm-1 at room temperature has been reported for the composition Na3.4Zr2Si2.4P0.6O12 1. Combining this highly conductive solid electrolyte with Na metal anodes however raises some challenges. The Na metal/NaSICON interface is indeed characterized by a large Area Specific Resistance (ASR) 1,2; the stability of Na metal versus NaSICON and the formation of a resistive Solid-Electrolyte Interface (SEI) still has to be more fundamentally understood. This work addresses the challenge of minimizing the large Na metal / NaSICON interfacial resistance. Two routes to achieve low ASR have been identified: 1. Improving the contact between the anode and electrolyte by applying uniaxial pressure during cell assembly; 2. Altering the NaSICON surface chemistry to improve its wettability. The influence of applied pressure and of surface treatments (rough polishing, fine polishing, post-polishing annealing) on the ASR was analysed by Electrochemical Impedance Spectroscopy (EIS). The samples’ surface chemistry was analysed by X-ray Photoelectron Spectroscopy (XPS), Low Energy Ion Scattering (LEIS) and Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The samples’ surface roughness was measured by light interferometry to interpret the observed differences between fine and roughly polished samples.
Authors : Katharina Hogrefe*, Bernhard Gadermaier and H. Martin R. Wilkening * presenting and contact author
Affiliations : Institute of Chemistry and Technology of Materials, Graz University of Technology (NAWI Graz), Stremayrgasse 9, A-8010, Austria
Resume : Na3PS4 is a promising electrolyte for future Na+ all-solid state batteries. At ambient temperature, the ionic conductivity in its cubic form is in the order of 10−4 S cm−1 . Even though several studies focused on explaining the dynamic properties of cubic Na3PS4, the driving forces that lead to fast Na+ exchange are not yet completely clear. Here, we synthesized nanocrystalline, defect-rich cubic Na3PS4 via a solid-state synthesis with subsequent annealing at 250 °C for 12 h. Ion dynamics of the powder sample was analysed using high-precision broadband impedance spectroscopy and variable-temperature, time-domain 23Na NMR spin-lattice relaxation rate measurements. We were able to separate bulk ion dynamics from electrical relaxation associated with grain boundary regions. While macroscopic transport is characterized by an activation energy of 0.36 eV, 23Na NMR indicates a much lower value of 0.18 eV, see also . This discrepancy points to length-scale dependent dynamic parameters. Indeed, electric modulus spectroscopy, i.e., the analysis of resistivity peaks ρν (= M''/ω)(1/T), revealed a low-temperature activation energy of 0.13 eV, which is consistent with our result from NMR. We attribute this barrier to extremely fast local Na hopping processes constituting the basis for long-range ionic transport in Na3PS4.  A. Hayashi et al., Nat. Commun., vol. 3, pp. 856-860, 2012.  C. Yu et al., J. Mater. Chem. A, vol. 4, pp. 15095-15105, 2016.
Authors : Junxiong Wu, Francesco Ciucci*, Jang-Kyo Kim*
Affiliations : Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
Resume : Sodium (Na) metal is an appealing anode material for Na batteries because of its high theoretical specific capacity of 1166 mAh g-1 and low electrochemical potential of -2.71 V versus standard hydrogen electrode. However, the long-standing issue of dendrite growth during repeated Na plating and stripping hinders the practical use of Na-metal anodes for high energy density batteries. Rational assembly of Na metal with 3D hosts has been proven to be an effective way to accommodate the large volume changes arising from Na plating/stripping and reduce the local current density so as to mitigate the Na dendrite growth. Unfortunately, Na metal tends to deposit on the top part of 3D hosts near the separator, known as the “top-growth” mode, leading to poor utilization of internal voids. Here, we report the fabrication of 3D sodiophilic-sodiophobic gradient hosts, Au/CF, by sputter coating of Au on the bottom part of melamine-derived carbon foam scaffold, which can guide a “bottom-up” deposition. As a result, the Na@Au/CF composite anodes can run for 1000 h with a steady overpotential of ~20 mV at a current density of 2 mA cm-2 in symmetric cells, illustrating its great potential in stabilizing Na deposition. In addition, the Na@Au/CF anode exhibits much better electrochemical performance than the Na@CF host without Au coating when coupled with a Na3V2(PO4)2F3 and sulfurized polyacrylonitrile cathode. The sodiophilic-sodiophobic gradient structure paves a new avenue for stable Na metal, which can also be extended to other types of metal anodes.
Authors : Fabrizio Murgia, Matteo Brighi, Radovan Cerny
Affiliations : Laboratory of Crystallography, Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, CH-1211, Geneva, Switzerland
Resume : Complex hydrides are a fascinating class of materials that were deeply investigated for solid-state hydrogen storage. The interest of the scientific community on those chemicals has been recently drawn again since it was shown that, in particular conditions, they allow fast cationic conduction. However, elevate ionic motion occurs only after a structural phase change, which is generally far from room temperature (rt). Many efforts have been made in order to decrease the phase transition temperature, which has been found also influenced by the nature, size and shape of the hydride's anion. Therefore, frustrating the anion sublattice, either by anion replacing or anion mixing, is an effective strategy to stabilize towards rt the fast conductive phase, taking into account that interesting ionic conductivity for practical purpose should be above 1 mS cm-1 at 25°C. Lying on this approach, we recently develop a new group of fast Na+ conductors, obtained by mechanical mixing of different closo- and carbacloso-borates. Among them, Na4(CB11H12)2(B12H12) features a superior ionic conductivity of 2 mS cm-1 at rt, with a low activation energy of 314 meV. Temperature-dependent synchrotron powder X-rays diffraction shows neither further phase transitions nor decomposition up to 500°C. Electrochemical stability has been studied by means of CV and resulted in an operational voltage window up to 4.1 V vs. Na+/Na. Interestingly, such value matches the decomposition value that has been measured for the B12H122--containing salts in acetonitrile. This evidence leads to speculate that the oxidative stability of the solid electrolytes obtained by anion mixing is limited by the electrochemical stability of the less stable anion. To elucidate this aspect, CV of different closo and carbacloso-borates binary mixtures have been compared, revealing a decomposition trend that confirms the aforementioned hypothesis. To get further insights into the decomposition products generated at high voltage, XPS on the electrode’s surface and on-line MS analysis have been carried out. Reductive stability was also investigated. As a case study, Na4(CB11H12)2(B12H12) has been proved to be stable toward Na symmetrical Na||Na cell operating at rt: reversible Na plating/stripping has been achieved, with a steady and limited polarization, starting from ±8.5 mV that further decreases, stabilising around ±6 mV for more than 500 operating hours. Interfaces evolution has been also studied by means of in situ EIS, confirming the good compatibility between Na and the solid electrolyte. The superior electrochemical properties of this solid electrolyte even at rt have been also demonstrated with galvanostatic tests on Na batteries, towards NaCrO2 as positive electrode (120 mAh g-1 theoretical capacity). The cell delivers more than 90% of the theoretical capacity with a CE above 99% up to C/5, with an average operating voltage of 3.0 V vs. Na+/Na. Promising results have also been obtained with the 3.8 V electrode Na2Fe2(SO4)3, demonstrating the compatibility of Na4(CB11H12)2(B12H12) with different class of electrode materials.
Authors : Bounazef Tinehinane, Mohammad Kassem, EugèneBychkov
Affiliations : ULCO, LPCA(EA 4493), F-59140 Dunkerque, France
Resume : Email: firstname.lastname@example.org Abstract: Sodium glassy/glassy ceramic chalcogenide systems exhibit high ionic conductivity values making particularly promising for application as inorganic solid electrolytes in all solid state sodium ion batteries. However, in contrast to their silver counterparts, the ion transport and structural information related to sodium systems is scarce. To this end, glass sample compositions in the quasi-binary Na2S-As2S3 chalcogenide system and over a large concentration range (up to 4 orders of magnitude in the sodium content) are synthesized and characterized for the first time. The glass-forming region, determined by X-ray diffraction, for the (Na2S)x(As2S3)1-x extends up to x = 0.35. Macroscopic properties such as density, mean atomic volume, and glass characteristic temperatures (the glass transition, Tg and the crystallization Tx) were measured. Both Tg and Tx decrease with increasing sodium content x. The glasses belong to Na+ ionic conductors and their room temperature conductivity increases by 5 orders of magnitude from 2.2010-16 S.cm-1 to 4.610-11 S.cm-1 over 4 orders of magnitude in the sodium content y, between ymin = 0.004 at.% Na (x = 10-4) and ymax 16.3 at.% Na (x = 0.35). Meanwhile, the conductivity activation energy shows an overall decrease by 5 factors from 1.05 eV (x = 0.0) to 0.56 eV (x = 0.35). Two different ion transport regimes were distinguished: (a) critical percolation domain at low sodium content (≤ 1-2 at.% Na) and (b) modifiercontrolled domain at highsodium content. The structural investigations were carried out using Raman scattering and neutron diffraction measurements and ion transport changes in Na2S-As2S3 glasses in relation to structural changes are studied.
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Defects & Transport Phenomena (I): Modelling : David Mebane
Authors : Andreas Klein
Affiliations : Technische Universität Darmstadt, Materials Science, Electronic Structure of Materials, Otto-Berndt-Strasse 3, 64287 Darmstadt, Germany
Resume : Different charge compensation mechanisms are known for ionic solids. Among them are the formation of compensating defects such as electronic or ionic defects, the valence changes of atoms and the segregation of dopants. In principle, the introduction of positive charges by donor doping or reduction results either in the compensation by electrons, negatively charged intrinsic acceptors as metal vacancies, the reduction of a one of the species in the compound, or in the segregation of the dopant species. The situation is reversed for the addition of negative charges. While the different mechanisms are well-documented for different materials, predicting the prevailing compensation mechanism in a material is hardly possible. It is a common perception that the Fermi energy is determined by the defect concentrations. However, it is also possible to describe the concentration of defects as a function of the Fermi energy. This reveals Brouwer diagrams, which are identical to those obtained using standard defect chemistry calculations. In addition, it enables a direct comparison of the different compensation mechanisms.
Authors : Kia Chai PHUAH, Ruoyu DAI, Stefan ADAMS
Affiliations : Department of Materials Science and Engineering - National University of Singapore
Resume : The bond-valence method is a simple robust method originally developed to validate crystal structures. By comparing valence sums based on geometric distances between atoms in a crystal structure, apparently stable configurations can be identified and provide a dependable prediction for the stability of a structure. In our augmented energy-scaled “softBV” form the method is applied to solid-state ionic conductors to identify promising candidate structures with high ion mobility. Bond-valence site energy landscapes are generated by scanning probe ions throughout the structure. Probable ion transport pathways and their approximate migration barriers are rapidly visualized for prototype structures. The speed and simplicity of this approach enables screening of structure databases to identify next-generation solid electrolytes. We further extend the bond-valence site energy method by automatizing ion pathway analysis for high-throughput screening without human intervention in the freely available softBV-GUI software. Predictions of suitable dopants and of absolute conductivities guide the optimization of transport properties in candidate structures. Large numbers of structural modifications can be rapidly computed exploiting the speed of the approach, which in conjunction with big data techniques helps to improve the quantification and robustness of the predictions. Examples of experimental verifications of identified and optimized ion-conducting solids will be demonstrated.
Authors : Denis Gryaznov(a), Maximilian F. Hoedl(b), Guntars Zvejnieks(a), Rotraut Merkle(b), Eugene A. Kotomin(a,b), Joachim Maier(b)
Affiliations : (a) Institute of Solid State Physics, University of Latvia, 8 Kengaraga, LV-1063, Riga, Latvia (b) Max Planck Institute for Solid State Research, Heisenbergstr. 1, D-70569, Stuttgart, Germany
Resume : Protonic ceramic fuel cells (PCFC) attract growing interest, since BaZr1-xYxO3-x/2 electrolytes offer a higher ionic conductivity compared to oxide ion conductors < 600°C. Optimized cathode materials with mixed protonic and electronic conductivity (e.g. (La,Ba,Sr)(Co,Fe,Zn,Y)O3-delta ) are crucial for PCFC performance. However, they generally show lower degrees of hydration compared to BaZr1-xYxO3-x/2. We perform density functional calculations based on the Hubbard (PBE+U) model and hybrid PBE0 exchange-correlation functional (using VASP and CRYSTAL codes) for La1-xSrxFeO3-delta , Ba1-xSrxFeO3-delta , including preliminary data for BaCoO3-delta. We present a detailed analysis of the density of states, volume and local geometry changes, oxidation and hydration energies as a function of oxygen deficiency (nominal Fe oxidation state, hole concentration). The hydration energy is more negative for Ba1-xSrxFeO3-delta than for La1-xSrxFeO3-delta, which can be assigned to the larger oxide ion basicity. The hydration energy becomes less negative with increasing hole concentration, which is related to hole delocalization to the oxide ions. Thus, we achieve a comprehensive understanding of water incorporation in mixed protonic-electronic conductors.  R. Zohourian, R. Merkle, G. Raimondi, J. Maier, Adv. Funct. Mater. 28 (2018), 1801241  D. Gryaznov, R. Merkle, E. A. Kotomin, J. Maier, J. Mater. Chem. A 4 (2016), 13093  M. Hoedl, D. Gryaznov, R. Merkle, E. A. Kotomin, J. Maier, J. Mater. Chem. A submitted
Authors : BP Uberuaga, CR Kreller, MT Janish, JA Valdez, R Perriot, G Pilania, YQ Wang
Affiliations : Los Alamos National Laboratory
Resume : It is becoming ever more apparent that, in complex compounds such as pyrochlores, the detailed arrangement of the cations drives functionality. For example, both radiation tolerance and ionic conductivity have been linked to how easily cations can mix across sublattices. This is due to the fact that mass transport in these materials is a strong function of the cation distributions. However, the actual relationship between the cation, or chemical, structure of these compounds and the rates of transport are still not well established. While some reports find enhanced ionic conductivity in disordered materials, others find higher conductivity in ordered phases. Many of these studies use chemistry to influence the disorder, essentially changing multiple variables at once. However, the degree to which cations mix can be finely controlled using radiation damage without changing chemistry. Here, we use radiation damage as a tool to induce changes in the cation structure of thin-film model pyrochlores. We then characterize the extent to which those changes impact mass transport. We combine these experimental efforts with state-of-the-art simulation methodologies to understand how atomic scale mechanisms dictating mass transport change when the cation structure is modified. We have found that even small changes in cation structure can lead to large changes in the transport characteristics of the material. Our results provide new insight into mass transport in materials that exhibit chemical complexity well beyond the model systems studied where chemical disorder dictates the fundamental behavior of the material.
Authors : Jana P. Parras, Roger A. De Souza
Affiliations : Institut of Physical Chemistry - RWTH Aachen University
Resume : Cation diffusion in fluorite-type AO2 polycrystals has been observed experimentally in diverse studies to occur much faster along grain boundaries than in the bulk phase (Dgb >> Db). In many cases, the corresponding activation enthalpy (?Hgb) is seemingly unphysical: ?Hgb approaches ?Hb or even exceeds it. In this study we examined the possibility of cation-defect accumulation, in space-charge layers adjacent to a grain boundary, giving rise to accelerated grain-boundary diffusion. Using continuum-level simulations, we predicted defect distributions in space-charge layers from thermodynamic driving energies, allowed cation diffusion to occur parallel to the interface, and analysed the resultant diffusion profiles to obtain the product of wgb, the effective boundary width, and Dgb. Our results show that the presence of space-charge layers at a boundary can give rise to ?Hgb as high as ?Hb but not exceeding it. Furthermore, we demonstrate, through derivation of an empirical relationship, that wgb·Dgb can be predicted from knowledge of boundary space-charge potential and Db.
Authors : Marcel Sadowski, Karsten Albe
Affiliations : Technical University Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt
Resume : Sulfide solid electrolytes (SE) comprise promising materials for the usage in Li all-solid-state batteries due to high Li ion conductivities and easy processing. Especially the argyrodite materials within Li6PS5X (X = Cl, Br, I) stand out with ionic conductivities in the range of 1 mS/cm competing with those of conventional liquid electrolytes. For the Li6PS5Br it was found that a S/Br site-disorder in the range of 10-40% can be induced depending on the synthesis protocol. Furthermore, it was found that the ionic conductivity increases with increasing site-disorder. In order to understand the underlying dependence between structure and ionic transport we performed density functional theory (DFT) and ab-initio molecular dynamics (AIMD) simulations on a variety of Li6PS5Br structures with different degrees of site-disorder. In line with the experiment, we will present results from AIMD simulations proving the necessity of S/Br site-disorder to enable sufficient Li transport at low temperatures . A detailed analysis of the influence of the local structure on the Li transport is carried out and relations between the S/Br site-disorder and other properties such as the thermodynamical stability or lattice constants are presented. The results can be used to develop improved materials and synthesis protocols.  A. Gautam, M. Sadowski et al., Chem. Mater. 31 (24) 10178-10185 (2019), https://doi.org/10.1021/acs.chemmater.9b03852
Authors : E. A. Kotomin, R. A. Evarestov, A. Senocrate , J.Maier
Affiliations : Max Planck Institute for Solid State Research, Stuttgart, Germany; Institute of Solid State Physics, University of Latvia, Riga, Latvia; Institute of Chemistry, St. Petersburg State University, Petrodvorets, Russia
Resume : Halide perovskites have attracted great interest as light absorbers for photovoltaic applications. Among these materials, hybrid organic-inorganic systems based on methylammonium (MA) and/or formamidinium (FA) lead iodide have shown the highest performances in solar cell devices. Such hybrid compositions, however, suffer from high instability under operation. One currently explored alternative is to move to the fully inorganic CsPbX3 (with X=I, Br), as these compounds could potentially fulfill both performance and stability criteria. However, many aspects regarding the stability of these inorganic materials, as well as the influence of ionic defects on their properties have yet to be thoroughly investigated experimentally and theoretically: We discuss here  the first principles DFT hybrid functional calculation of the atomic and electronic structure of perfect CsPbI3 and CsPbBr3 crystals and defects therein. The decomposition energies into binary compounds (CsX and PbX2) are calculated and compared with experimental data. Calculated temperature dependences of the heat capacities are also in good agreement with experimental data. It is shown that interstitial halide atoms in CsPbBr3 do not tend to form di-halide dumbbells Br_2(-) while such dimers are energetically favorable in CsPbI3, similar to the H-centers in alkali halides. Instead, in the case of CsPbBr3, a loose trimer configuration (Br_3(2-) is energetically favorable. The effects of crystalline symmetry and bond covalency are discussed as well as the role of defects in recombination process. . R. A. Evarestov, E. A. Kotomin, A. Senocrate, R. K. Kremer, J.Maier, PCCP, 2020, in press
Solid State Energy Devices (V): Batteries : Mauro Pasta
Authors : Francesco Ciucci (a,b)
Affiliations : (a) The Hong Kong University of Science and Technology, Mechanical and Aerospace Engineering, Clearwater Bay, Kowloon, Hong Kong, China SAR (b) The Hong Kong University of Science and Technology, Chemical and Biological Engineering, Clearwater Bay, Kowloon, Hong Kong, China SAR
Resume : Despite the widespread commercialization of conventional Li-ion batteries (LIBs), their safety I still a significant challenge. Conventional electrolytes are highly flammable and pose a significant safety hazard in case of an accident, overheating, and overcharging. Through experiments  and computations [2, 3], we developed and studied several alternative electrolytes, including ceramics, non-flammable composite polymers, and non-flammable liquids for high-energy-density Li- and Na-metal batteries. Improving the interfacial resistances and allowing a stable operation is key to these technologies. For these reasons, our works deployed several strategies including the development of conformal interlayers using plastic crystals and gels as well as fluorinated additives for the formation of stable solid electrolyte interlayers . We also designed a non-flammable trimethyl-phosphate-based electrolyte for sodium-sulfur batteries operating at room temperature . Acknowledgments The author gratefully acknowledges support from the Hong Kong Innovation and Technology Fund (No. ITS/292/18FP). References:  Z. Lu, J. Yu, J. Wu, M.B. Effat, S.C. Kwok, Y. Lyu, M.M. Yuen, F. Ciucci, Enabling room-temperature solid-state lithium-metal batteries with fluoroethylene carbonate-modified plastic crystal interlayers, Energy Storage Materials, 18 (2019) 311-319.  Z. Lu, F. Ciucci, Metal Borohydrides as Electrolytes for Solid-State Li, Na, Mg, and Ca Batteries: A First-Principles Study, Chemistry of Materials, 29 (2017) 9308-9319.  Z. Lu, J. Liu, F. Ciucci, Superionic Conduction in Low-Dimensional-Networked Anti-Perovskites (2019) - submitted  J. Yu, Y.-Q. Lyu, J. Liu, M.B. Effat, S.C. Kwok, J. Wu, F. Ciucci, Enabling non-flammable Li-metal batteries via electrolyte functionalization and interface engineering, Journal of Materials Chemistry A, 7 (2019) 17995-18002.  J. Wu, J. Liu, Z. Lu, K. Lin, Y.-Q. Lyu, B. Li, F. Ciucci, J.-K. Kim, Non-flammable electrolyte for dendrite-free sodium-sulfur battery, Energy Storage Materials, (2019)-In Press.
Authors : Jacinthe Gamon*, Benjamin B. Duff*", Rhun Morris*, Matthew S. Dyer*, Christopher Collins*, Luke M. Daniels*, T. Wesley Surta*, Paul M. Sharp*, Michael W. Gaultois*, Frédéric Blanc*", John B. Claridge* and Matthew J. Rosseinsky*
Affiliations : * Department of Chemistry, University of Liverpool, Crown Street, L69 7ZD Liverpool, UK. " Stephenson Institute for Renewable Energy, University of Liverpool, Peach Street L69 7ZF Liverpool, UK.
Resume : All solid-state batteries are of considerable current interest because they are a potential route to the use of lithium metal anodes while avoiding dendrite formation. Among the variety of lithium solid-state electrolytes studied, sulphides show among the highest Li ion conductivity. For instance, members of the thio-LISICON family and the Li-argyrodites Li6PS5X (X = Cl, Br, I) have superior ionic conductivities, σ ~ 1-20 mS cm-1 at RT and low activation energies, Ea, ~ 0.20 eV. With the goal of finding new lithium solid electrolytes by a combined computational-experimental method, the exploration of the Li-Al-O-S phase field resulted in the discovery of a new sulphide Li3AlS3. This compound was made via the solid state reaction of Li2S and Al2S3 in sealed ampoules. The structure of the new phase was determined through an approach combining synchrotron X-ray and neutron diffraction with 6Li and 27Al magic angle spinning nuclear magnetic resonance spectroscopy, and revealed a highly ordered cationic polyhedral network within a sulphide anion hcp-type sublattice. The originality of the structure relies on the presence of Al2S6 repeating dimer units consisting of two edge-shared Al tetrahedra. We find that, in this structure type consisting of alternating tetrahedral layers with Li-only polyhedra layers, the formation of these dimers is constrained by the Al/S ratio of 1/3. Moreover, by comparing this structure to similar phases such as Li5AlS4 and Li4.4Al0.2Ge0.3S4 ((Al+Ge)/S = 1/4),[4,5] we discovered that the Al2S6 dimers not only influence atomic displacements and Li polyhedral distortions, but also determine the overall Li polyhedral arrangement within the hcp lattice, leading to the presence of highly ordered vacancies in both the tetrahedral and Li-only layer. AC-impedance measurements revealed a low lithium mobility (σbulk =1.3(1)·10-8 S·cm-1 at room temperature), which is strongly impacted by the presence of ordered vacancies. A potential diffusion pathway was proposed through the use of the bond valence sum mapping method which showed the dimensionality of the conduction and confirmed that ordered vacancies act as road block for diffusion. Finally, a composition-structure-property relationship understanding was developed to explain the extent of lithium mobility in this structure type.  Xu, W.; Wang, J.; Ding, F.; Chen, X.; Nasybulin, E.; Zhang, Y.; Zhang, J.-G. Lithium Metal Anodes for Rechargeable Batteries. Energy Environ. Sci. 2014, 7 (2), 513–537.  Kamaya, N.; Homma, K.; Yamakawa, Y.; Hirayama, M.; Kanno, R.; Yonemura, M.; Kamiyama, T.; Kato, Y.; Hama, S.; Kawamoto, K.; et al. A Lithium Superionic Conductor. Nat. Mater. 2011, 10 (9), 682–686.  Rao, R. P.; Adams, S. Studies of Lithium Argyrodite Solid Electrolytes for All-Solid-State Batteries. Phys. Status Solidi A 2011, 208 (8), 1804–1807.  Lim, H.; Kim, S.-C.; Kim, J.; Kim, Y.-I.; Kim, S.-J. Structure of Li5AlS4 and Comparison with Other Lithium-Containing Metal Sulfides. J. Solid State Chem. 2018, 257, 19–25.  Leube, B. T.; Inglis, K. K.; Carrington, E. J.; Sharp, P. M.; Shin, J. F.; Neale, A. R.; Manning, T. D.; Pitcher, M. J.; Hardwick, L. J.; Dyer, M. S.; et al. Lithium Transport in Li4.4M0.4M′0.6S4 (M = Al3+, Ga3+, and M′ = Ge4+, Sn4+): Combined Crystallographic, Conductivity, Solid State NMR, and Computational Studies. Chem. Mater. 2018, 30 (20), 7183–7200.
Authors : Juan Carlos Verduzco, Ernesto Marinero, Alejandro Strachan
Affiliations : School of Materials Engineering, Purdue University
Resume : Substitution doped lithium lanthanum zirconium oxide (LLZO) garnets are promising Li ion conductors to replace current liquid electrolytes in Li ion batteries. Experimental results show that the introduction of aliovalent elements generally improves ionic conductivity. This improvement is attributed to an increased lattice parameter and changes in the lithium stoichiometry. However, quantitative predictive models of these effects are lacking and their development could contribute to the rational development of solid electrolytes. We will present ab initio molecular dynamics simulations of Li transport in LLZO-based materials to characterize the role of the dopant on transport. An analysis of residence time of the Li ions on the tetrahedral and octahedral sites of the crystal provides new insight into the mechanisms behind the improvement in conductivity. Furthermore, models based on these calculations explain the optimal level of doping. In addition, to guide the design of new garnets with improved properties, we used machine learning to develop predictive models from all published conductivities for over a hundred different compositions. Using existing data and these models, we will show that sequential learning can cut down on the number of experimental trials to achieve an optimal solution by approximately 60%.
Authors : G. Mallia, F. M. Pesci, A. Aguadero, N. M. Harrison
Affiliations : Imperial College London (UK)
Resume : Garnet-type materials such as Li7La3Zr2O12 (LLZO) are promising candidates as solid-state electrolytes in Li-ion batteries, the dominant power supplies for portable electronics, energy storage and electric vehicles. LLZO is characterised by high ionic conductivity, negligible electronic transport and good chemical stability with respect to metallic Li. In the cubic phase (Ia-3d) the ionic conductivity of LLZO is two orders of magnitudes higher than in the tetragonal phase (I41/acd), 10-3 S/cm vs 10-6 S/cm The cubic structure is formed of ZrO6 octahedra linked by LaO8 dodecahedra; Li atoms occupy interstitial sites, which can be classified as the tetrahedral 24d sites (Li1) and distorted octahedral 96h sites (Li2). The fractional occupation of the Li sites and the consequent occupational disorder play an important role in the Li ion migration. Periodic quantum mechanical simulations within the density functional theory will be performed by using the range separated hybrid functional HSE06, as implemented in the CRYSTAL17 program. The aim of this study is to investigate the possible influence of both intrinsic and extrinsic defects (in particular Li vacancies, O vacancies and substitutional dopants on Li sites) on the structural and electronic properties of this material and to explore what role these play in the observed nucleation and propagation of Li-dendrites within the electrolyte in operando.
Authors : R. Xia, Y. Wang, M. Huijben, J.E. ten Elshof
Affiliations : R. Xia, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands; Y. Wang, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands; M. Huijben, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands; J.E. ten Elshof, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands.
Resume : Energy storage is essential for many applications such as portable electronic devices and electric vehicles. Lithium ion batteries (LIBs) are the most commonly used energy storage devices because of their high energy density and stability over repeated charge-discharge cycling. High rate performance of LIBs is nowadays one of the most important requirements for electric vehicles. However, due to the limitations of conventional graphite anodes, the charge-discharge process of the battery is limited to 1 C (or even lower). Titanium-based oxides are promising candidates to fulfill those requirements. However, in order to reach high power density, researchers usually use strategies like incorporation of carbon within the composites and/or a mesoporous structure design, which reduce the volumetric capacity. Niobium tungsten oxides have recently been shown to exhibit very fast (dis)charging capacity owing to their stable host structure suitable for lithium diffusion. It was originally suggested that dimensional reduction of the material would have a negligible effect on its electrochemical performance, and recent studies on 300 nm thick nanofibers seemingly confirmed that hypothesis by failing to demonstrate enhanced energy storage property in comparison to bulk materials. However, in this contribution we will provide conclusive evidence for the dependence of the lithiation process of Nb18W16O93 anodes on the grain size. We will show that the lithiation dynamics of niobium tungsten oxide are significantly enhanced when the secondary grain size is below 100 nm. This study provides a new perspective on the importance of nanoscaling this material to further improving the electrochemical performance of Nb18W16O93 anodes for realizing fast (dis)charging for future energy storage devices.
Authors : Anh Ha Dao, John Low
Affiliations : WMG, Warwick Electrochemical Engineering Group, Energy Innovation Centre, University of Warwick, Coventry, CV5 7AL, United Kingdom
Resume : The lithium ionic conductor argyrodite Li6PS5Cl with high conductivity is a promising candidate as an electrolyte in all-solid-state lithium-ion batteries (LIBs) at room temperature. However, it owns several drawbacks such as poor mechanical property, unstable interface with important electrode active materials, e.g. Li metal, is limiting practical energy storage applications. The novel hybrid solid electrolyte PVdF-HFP/Li6PS5Cl is prepared to overcome such drawbacks. It is fabricated with different percentages of PVdF-HFP from 5 to 50 %, and ionic conductivity is improved by adding Li salt, LiCF3SO3. The hybrid solid electrolyte PVdF-HFP/Li6PS5Cl obtains excellent ionic conductivity closed to 10-3 Scm-1 at 30 oC with improved mechanical property. An all-solid-state cell LTO| PVdF-HFP/Li6PS5Cl|NMC was successfully operated at 30 oC with high reversibility. The performance of the half cells with Li metal also exhibits compatibility of the electrolyte with Li.
Authors : Jiapeng Liu, Ziheng Lu, Mohammed B. Effat, Francesco Ciucci
Affiliations : Jiapeng Liu, Ziheng Lu, Mohammed B. Effat, Francesco Ciucci: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China Francesco Ciucci:Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
Resume : The search for next-generation solid-state superionic conductors has attracted significant attention. Among Na superionic conductors, Na11Sn2PS12 has been reported to have a room temperature ionic conductivity of 1.4 mS/cm. In this study, we employ density functional theory to study the stability of Na11Sn2PS12 and further explore the substitution of Sn with Ge. Our results indicate that Na11Ge2PS12 is more stable than Na11Sn2PS12. Furthermore, substituting Sn with Ge increases the band gap, improves the room temperature ionic conductivity by a factor of 2, and lowers the activation energy of Na hopping. Statistical analysis suggests that Na11Ge2PS12 has a faster diffusion along the ab-plane compared to the c-axis. The Na diffusion in Na11Ge2PS12 appears to occur with two different mechanisms depending on temperature: 1) an ion hopping process at lower temperatures (<800 K); 2) a fluid-like distribution of Na ions at higher temperatures (>1000 K). The computations suggest that Na11Ge2PS12 is a promising candidate as a solid Na electrolyte due to its high room temperature ionic conductivity and phase stability. In light of these simulation results, we expect to stimulate further experimental studies on Na11Ge2PS12.
Solid State Electronic Devices: Resistive Switching : Mónica Burriel
Authors : Venkata R. Nallagatla, Thomas Heisig, Christoph Baeumer, Vitaliy Feyer, Matteo Jugovac, Giovanni Zamborlini, Claus M. Schneider, Rainer Waser, Miyoung Kim, Chang Uk Jung, Regina Dittmann
Affiliations : Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany, Department of Physics and Oxide Research Centre, Hankuk University of Foreign Studies, Yong-in 449-791, South Korea, Department of Material Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 151-747, South Korea,
Resume : Redox-based based memristive devices are one of the most attractive candidates for future non-volatile memory applications and neuromorphic circuits. For the most common memristive band insulators, resistive switching is induced by the formation of oxygen vacancies and the resulting valence change on the cation sublattice. However, manganites, cobaltites and ferrates undergo a topotatic phase transition between the perovskite and the brownmillerite structure upon reduction that might also be induced during resistive switching. Due to the spatially confined redox-process, experimental proofs of topotactic phase transitions in memristive devices are very rare. By employing X-ray absorption spectromicroscopy, we demonstrate that the reversible topotactic phase transition between the insulating brownmillerite phase, SrFeO2.5, and the conductive perovskite phase, SrFeO3, gives rise to resistive switching of SrFeOx memristive devices. Interestingly, we found that the electric field induced phase transition spreads over a large area in (001) oriented SrFeO2.5 devices, where oxygen vacancy channels are ordered along the in-plane direction of the device. In contrast, (111) grown SrFeO2.5 devices with out-of-plane oriented oxygen vacancy channels, reaching from bottom to the top electrode, show a localized phase transition. We attribute this difference in the extension of the topotactic phase transition to the anisotropic oxygen ionic conduction in the brownmillerite structure.
Authors : Jack Strand, Alexander L. Shluger
Affiliations : Department of Physics and Astronomy, UCL, UK
Resume : We use atomistic modelling and Density Functional Theory calculations to investigate how electron injection from metal electrodes into thin HfO2 films under voltage bias causes changes of their resistance. The results suggest that electron and hole injection can facilitate the formation of Frenkel defects in monoclinic as well as amorphous HfO2 films and stimulate diffusion of O ions. In both crystalline and amorphous HfO2, electrons and holes localize and form bi-polarons [1,2], which facilitate the formation of pairs of Frenkel defects [3,4]. The electron trapping causes strong Hf–O bond weakening and facilitates thermally activated formation of Frenkel defects: neutral O vacancies and interstitial O2- ions. The barriers for these processes in a-HfO2 are about 1.5 eV and reduced by bias application. We show that more O vacancies can be produced near pre-existing vacancies if they become negatively charged after electron trapping. It is found that the third vacancy formation energy is, on average, 0.2 eV lower than the second and the barrier for vacancy formation is also reduced significantly. Holes also form bi-polaron states in a-HfO2 which reduce barriers for formation of V2+ oxygen vacancies and interstitial O atoms. These results provide insights into the interplay between electronic and ionic processes in crystalline and amorphous HfO2 films in memristive devices.  D. Munoz Ramo, et al., Phys. Rev. Lett. 99, 155504 (2007).  M. Kaviani, J. Strand, V. V. Afanas’ev, A. L. Shluger, Phys Rev B. 94, 020103 (2016)  S. R. Bradley, A. L. Shluger and G. Bersuker, Phys. Rev. Appl. 4, 064008 (2015)
Authors : Mahmoud N. Almadhoun *(1), Maximilian Speckbacher (2), Brian C. Olsen (1), Erik J. Luber (1), Sayed Youssef Sayed (1), Marc Tornow (2), Jillian M. Buriak (1)
Affiliations : (1) Department of Chemistry, University of Alberta (2) Molecular Electronics, Technische Universität München (TUM)
Resume : In its crystalline and stoichiometric form, Ga2O3 is an electrically insulating oxide with an ultra-wide band gap of ~4.8 eV. However, lattice defects in form of oxygen vacancies can modify the band gap of the oxide and significantly change its resistivity. We utilize this structure-property relationship to create memristive devices with large current-voltage hysteresis, a core property required for data storage applications. Under typical ambient laboratory conditions, gallium undergoes rapid and spontaneous oxidation to form a quasi 2D oxide layer on its surface (~1-3 nm thick). Sandwiching this layer between bulk gallium and degenerately doped p-type silicon results in a layered device architecture, Ga/GaOx/p -Si. These junctions exhibit an abrupt insulator-metal transition that is reversible when cycled between -2.5 V to 2.5 V. Switching remains stable even after subjecting the junction to multiple voltage sweeps, reaching an endurance of over 600 cycles. The current ratio between the high and low resistive states can reach an impressive 108. From these device characteristics, it is hypothesized that oxygen ion migration under high electric fields could drive a disproportionation reaction, forming a non-stoichiometric and highly conducting GaOx suboxide across the terminals. Experiments to elucidate the mechanism will be shown. These results offer an exciting opportunity to relate device performance to fundamental ion-related redox mechanisms, at the nanoscale.
Authors : K. Zhu,1,2 G. Vescio,2 S. González-Torres,2 J. López-Vidrier,2 M. Lanza,1 A. Cirera,2 B. Garrido2
Affiliations : 1 Institute of Functional Nano & Soft Materials, Collaborative Innovation Center for Suzhou Nanoscience and Technology, Soochow University, 215123 Suzhou, China 2 MIND, Department of Electronic and Biomedical Engineering, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona, Spain
Resume : Two-dimensional (2D) materials have been introduced to the field of memristors to achieve novel properties that are not shown in the traditional ones, such as high transparency and flexibility, controllable volatile and non-volatile switching. However, most 2D materials based memristors are fabricated by mechanical exfoliation which is not a scalable method, or via chemical vapor deposition although this method requires a complex transfer. Instead, inkjet printing exhibits large-scalability, mask and residue free, versatility and cost-effectiveness properties which make it a promising technique for the future electronic industry demands. In this work, we introduce inkjet printing technology to fabricate 2D materials based memristors. We have first formulated proper printable inks and afterwards produced fully inkjet printed Ag/hexagonal boron nitride (h-BN)/Ag structure (device size 300 μm × 300 μm). The devices show stable bipolar resistive switching behavior with acceptable endurance and retention and an operation voltage around ±1 V, characterized by applying both ramped voltage stresses and pulsed voltage stresses. The devices can also show the potentiation for multilevel storage, which may be attributed to the multilayer of 2D material flake caused by inkjet printing. The results from this study will bring insight to the use of inkjet printing to construct 2D materials based memristors on papers, plastic or clothes, as well as the potential for commercialization.
Authors : Stephan Außen, Uwe Breuer*, Alexander Meledin†, Ivonne Bente, Alexander Hardtdegen, Regina Dittmann, and Susanne Hoffmann-Eifert
Affiliations : Peter Gruenberg Institute (PGI-7 & 10) and *ZEA-3, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany; † GFE, RWTH Aachen University, 52074 Aachen, Germany
Resume : Memristive devices based on the valence change mechanism (VCM) are intensively studied for non-volatile redox-based resistive random access memory (ReRAM) as well as for artificial synapses in beyond-von Neumann computing architectures. The relatively simple cell structure consists of a resistive switching metal oxide layer sandwiched between an inert, high-work function metal forming a Schottky-type contact and a chemically reactive metal forming an ohmic-type contact and enabling oxygen exchange across this interface. Starting from insulating transition metal oxides, the devices require an electroforming step comparable to a controlled breakdown that enables the formation of a conductive filament consisting of a chain-type percolation of oxygen deficient metal oxide material. The extension of the filament towards the two electrodes can be switched by application of voltages of opposite polarity resulting in the high and low resistive states. Beside the oxygen vacancy drift and diffusion process in the filament the effect of oxygen exchange across the metal oxide /metal electrode interface becomes more pronounced, especially for small devices of reduced dimensions. The importance of oxygen exchange reactions at the interface of the metal oxide and the chemically reactive electrode has been demonstrated recently. Here, we will focus on the effect of the structure of the materials, TMO and metal, being either amorphous or crystalline, close to the interface. Further, effects of charge compensation by means of impurity-ion segregation will be addressed. The results contribute to a deeper understanding of the competition between oxygen ion drift/diffusion vs. oxygen exchange reactions and of the role of material structure and impurity segregation on the device performance.
Poster Session (II) : Sandrine Ricote, Sam Cooper
Authors : Nicole Bein 1, P. Machado 2, M. Coll 2, M. Makarovic 3, T. Rojac 3, A. Brunier 4, M. Alexe 4, F. Chen 5, H. Schmidt 6, A. Klein 1
Affiliations : 1 Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, Darmstadt, Germany 2 Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, 08193 Barcelona, Spain 3 Electronic Ceramics, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia 4 Department of Physics, The University of Warwick, Coventry, CV4 7AL UK 5 Hefei National Laboratory for Physical Sciences at Microscale, USTC, Hefei 230026, China 6 Solid State Physics, Friedrich-Schiller Universität, Helmholtzweg 3, 07743 Jena, Germany
Resume : The Fermi energy determines the charge state of impurities, the concentration of electrons and holes and interfacial charge transfer processes. In a semiconductor, the Fermi energy can often be freely controlled across the whole energy gap by doping. This is not the case in oxides, where different mechanisms exist, which limit the range of the Fermi energy. In order to understand the limits of the Fermi energy in BiFeO3, photoelectron spectroscopy has been used to quantitatively determine the Fermi energy position in differently treated BiFeO3 thin films and ceramics. This is also related to the discussion whether the material is more a p- or more a n-type conductor. Different reducing and oxidizing treatments and interface formation with low and high work function oxides have been applied to raise or lower the Fermi energy. All treatments and interface formation were performed in-situ without breaking vacuum. The experiments reveal a lower and an upper limit of the Fermi energy of 0.5 eV and 1.75 eV above the valence band maximum, respectively. As also observed previously for Fe2O3 , the upper limit of the Fermi energy is related to a change of the valence of Fe from 3+ to 2+. The energies at which the valence change of Fe occurs is the same in Fe2O3 and BiFeO3. In contrast to the upper limit, there is no clear spectroscopic signature at low Fermi energies, which can be used to identify whether the lower limit is also fundamental. In addition to the limits of the Fermi energy, the energy level of the Co2+/3+ transition in Co-doped thin films could be identified to be at 0.8 eV above the valence band maximum using our approach. References  C. Lohaus, A. Klein und W. Jaegermann, Nature Commun. 9, 4309 (2018).
Authors : Matthäus Siebenhofer, Tobias Huber, Jürgen Fleig, Markus Kubicek
Affiliations : Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria & Kyushu University, Japan; Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria
Resume : Pulsed Laser Deposition (PLD) is a widely used technique to grow complex oxide films of a given stoichiometry. Due to the complex nature of the process itself, many parameters are known to influence thin film properties, structure or defect concentrations of the deposited thin films. However, the effect of ultraviolet radiation emitted by the plasma plume on thin film and substrate was so far a widely uncharted territory. Recent advances in the understanding of the photoconductivity and the effect of UV radiation on SrTiO3 now raise the question, if and how the UV radiation of the PLD plasma plume affects the electrical properties of an STO substrate during pulsed laser deposition. For this purpose STO single crystals with Pt current collectors were investigated by the means of in situ impedance spectroscopy during pulsed laser deposition (IPLD). By shielding the sample with a quartz disc the effect of the UV light could be isolated from potential effects of impinging species and real film growth. Our measurements revealed an increase of the STO conductivity as a response to the UV light, which recedes again after the illumination. When a thin STO layer is deposited on top, the conductivity decreases and the aforementioned effect disappears or is cloaked by another effect. This indicates that on the one hand the oxygen exchange on the STO surface is strongly affected by the UV light and that, on the other hand, thin layers of material deposited on the surface dramatically change the behavior of the whole system. In- and across-plane electrochemical measurements as well as characterization of the plasma plume and the voltage response of the single crystal to a laser pulse are presented in this contribution.
Authors : SangMyeong Lee, Hyojung Kim, Won Bin Kim, Gill Sang Han, Ho Won Jang, Hyun Suk Jung
Affiliations : School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea; Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea;School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea;School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea;Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea;School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea;
Resume : Resistive switching memory has been conceived as next-generation memory by fast information storage, large information storage and low energy consumption. Recently, organometal halide perovskite materials for use as resistive switching memory has received a great deal of attention owing to low operation voltage and high ON/OFF ratio. However, resistive switching memory based on the organometal halide perovskite materials have shown the poor endurance property such as endurance of 350 cycles. In this presentation, we exploited 2D/3D perovskite heterointeface structure by forming 2D phenylethylamine lead iodide ((PEA)2PbI4) endurance property of about 3000 cycles compared to the bare 3D perovskite layer whose endurance property was about 350. The excellent endurance property was explained in terms of presence of many reversible. This study provides another strategy for improving endurance property of perovskite based resistive switching memory devices.
Authors : D. Kemp, Prof. Dr. Roger A. De Souza
Affiliations : RWTH Aachen University; RWTH Aachen University, JARA-FIT
Resume : The material class of perovskites is well known for over a century and one of their most prominent and most researched representatives is strontium titanate (SrTiO3, short STO). STO is used as a model system in many applications such as solid oxide fuel cells or resistive switching. [1,2] In contrast, the material class of hybrid perovskites is a rather young research field. It has attracted huge attention in the last decade as absorber material in photovoltaic applications.  The main difference between those two material classes is that one component of the usually inorganic perovskite is replaced by an organic molecule, hence the name hybrid perovskite, and one promising candidate of this group is methylammonium lead iodide (CH3NH3PbI3, short MAPI). Both materials – STO and MAPI – have in common that their applications require external electric fields which can influence the material properties in general and particularly the ion transport. In this study we conducted molecular dynamics simulations using the LAMMPS code  and empirical pair potentials derived by Pedone et al.  for STO and Mattoni et al.  for MAPI. These potential sets have already shown by our group to be capable of describing oxygen and iodine diffusion in the respective system. We are able to describe the field-dependent oxide-ion mobility in STO very well with an analytical model from Genreith-Schriever and De Souza ; in contrast the field-dependent mobility of iodide ions in the hybrid perovskite MAPI showed some unusual features. This behavior will be discussed. Literature:  R. Merkle, Angew. Chem. Int. Ed. 2011, 47, 3874.  R. Waser, Adv. Mater. 2009, 21, 2632.  P. Gao, Energy Environ. Sci. 2014, 7, 2448.  S. Plimpton, J. Comp. Phys. 1995, 117, 1.  A. Pedone, J. Phys. Chem. B 2006, 110, 11780.  A. Mattoni, J. Phys. Condens. Mat. 2017, 29, 043001.  A. R. Genreith-Schriever, Phys. Rev. B 2016, 94.
Authors : Jiapeng Liu, Jian Wang, Alessio Belotti, Francesco Ciucci
Affiliations : Jiapeng Liu, Jian Wang, Alessio Belotti, Francesco Ciucci: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China Francesco Ciucci: Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
Resume : The need for clean and efficient energy conversion systems has stimulated tremendous research activities in the area of energy systems. Solid oxide fuel cells stand out because of their high efficiency and low emissions. In spite of the promise, to commercialize solid oxide fuel cells the operating temperature needs to be reduced below 800 °C. Unfortunately, at such low temperatures the oxygen reduction reactions taking place at the cathode side of the solid oxide fuel cells are typically sluggish. Ferrites have recently shown that they can overcome this challenge. However, the conductivity of these materials is typically low. Here, we introduce P in the Fe site of Ba0.95La0.05FeO3-δ to make a novel cathode material, Ba0.95La0.05Fe0.95P0.05O3-δ. We observe that Ba0.95La0.05Fe0.95P0.05O3-δ has higher electronic conductivity and better electrocatalytic activity compared to Ba0.95La0.05FeO3-δ. We also show by density functional theory calculations that introducing P in the Fe site lowers both the O vacancy formation and vacancy migration energies and promotes the creation of PO4 groups. These factors contribute to improving the diffusional properties and oxygen reduction reaction performance. In light of these results, we suggest that non-metal element doping is an effective strategy for the design of new ferrites.
Authors : Martin Krammer *(1), Alexander Schmid (1), Jürgen Fleig (1)
Affiliations : (1) Institute of Chemical Technologies and Analytics, Technische Universität Wien, Austria * lead presenter
Resume : Solid oxide electrolysis cells (SOECs) have received growing attention in the last few years as they offer a way to highly efficient production of hydrogen. However, this technology still faces various problems concerning components stability and durability. Since the air electrode is the limiting component in many cases, efforts are being made to characterise and optimise its performance. The perovskite-type oxide La0.6Sr0.4CoO3-d (LSC) is a promising material for the air electrode due to its mixed ionic-electronic conductivity and high catalytic activity. Although LSC has been extensively tested in solid oxide fuel cells (SOFCs), comparatively few studies have been made on LSC in the SOEC mode. In this work, the defect chemistry of LSC thin film microelectrodes at varying anodic DC voltages was investigated by analysing the chemical capacitance. After heating the samples for several hours at around 600 °C or after applying high bias up to 1 V an unexpected peak of the chemical capacitance was obtained at overpotentials higher than 100 mV. Correlations of these capacitive effects with variations of the oxygen exchange kinetics were also investigated. Supposedly, strontium segregation to the surface and a consequential formation of A-site vacancies in the bulk of the electrodes is responsible for this peak. Hence, a novel defect chemical mechanism that connects the oxygen exchange reaction and A site vacancies is suggested to contribute to the chemical capacitance of oxides.
Authors : Dickson O. Ojwang, William R. Brant
Affiliations : Department of Chemistry – Ångström Laboratory, Ångström Advanced Battery Centre, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden University
Resume : Li-ion batteries (LIBs) are widely used in the development of renewable energy technologies. However, most easily accessible lithium reserves are in either geographically remote or politically sensitive areas. This has raised concerns whether or not the global lithium resources can match the demand of upcoming electric and hybrid electric cars. Developing Na-ion batteries (NIBs) for large-scale electric energy (ESS) systems has become a growing interest in recent years due to the low-cost, environmentally benign and natural abundance of sodium resources. In this regard, Prussian white (PW), Na2-xFe[Fe(CN)6]1-y·nH2O (x = y = n = 0) has received great attention due to its potential high capacity for 2 Na+ storage (~170 mAh/g), facile synthesis, and inexpensive Earth abundant elements. However, in the literature the compound has been reported with a range of different compositions such as Fe(CN)6 vacancies, sodium and water content, leading to inconsistent electrochemical performance. In addition to these parameters, it is also extremely important to understand the conditions under which the electrodes should be processed, handled and stored prior to inclusion in an electrochemical cell to ensure their long-term cycling stability. In this work, we demonstrate for the first time the critical effect of exposing hydrous monoclinic Prussian white (M-PW) and anhydrous rhombohedral Prussian white (R-PW) electrodes to 55% relative humidity (RH). Both the M-PW and R-PW electrodes exhibit reversible capacity at C/10, but there are significant differences in their electrochemical behavior. Humidity has considerable influence on the initial capacity of M-PW electrodes such that ~21% is lost from 61 mAh/g to 48 mAh/g for pristine and 55% RH exposed, respectively. While in the case of R-PW electrodes the loss in the initial capacity is ~16%, from 148 mAh/g to 141 mAh/g for pristine and 55% RH exposed, respectively. This study is considered a potential roadmap to proper processing and storage of moisture sensitive electrode materials before building batteries for practical applications. Reference  Tarascon, J.-M. Is lithium the new gold? Nat. Chem. 2, 510 (2010).  Wang, L. et al. Rhombohedral Prussian White as Cathode for Rechargeable Sodium-Ion Batteries. J. Am. Chem. Soc. 137, 2548–2554 (2015).  Brant, W. R. et al. Selective Control of Composition in Prussian White for Enhanced Material Properties. Chem. Mater. 31, 7203–7211 (2019).
Authors : Qaisar Khushi Muhammad 1, Lukas Porz 1, Atsutomo Nakamura 2, Till Frömling 1, Jürgen Rödel1
Affiliations : 1Institute of Materials Science, Technische Universität Darmstadt, Darmstadt, 64287, Germany 2Department of Materials Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
Resume : Rutile (TiO2), a semiconductor with a wide bandgap, is prevalent due to its essential applications; for example, as gas sensor and as a photocatalyst in solar cells. In order to tailor electrical properties, engineering of zero dimensional point defects plays an important role. However, the solubility limit of the dopant constrains this tool for tailoring material properties significantly. In the present work, we demonstrate how one dimensional defects alter the electrical properties of rutile by inducing dislocations via controlled mechanical deformation. This is based on an approach reported by Adepalli et al. . However, we improved the high temperature deformation in order to arrange the dislocations so that their influence on electrical properties could be studied utilizing knowledge about alignment and dislocation type. Results from electrical measurements across and along the induced dislocation network are discussed. Furthermore, the change in defect chemistry at several temperatures and the effect of changing the oxygen partial pressure (pO2) on high temperature conductivity are shared. This way, the topic of dislocation induced change in functional properties is presented based upon an experimental approach combining micromechanics and solid state ionics concepts.  Adepalli, Kiran Kumar, et al. "Influence of line defects on the electrical properties of single crystal TiO2."Advanced Functional Materials" 23.14 (2013): 1798-1806.
Authors : Sien Ng*(1), Rohit John(1), Nripan Mathews(1,2).
Affiliations : (1)School of Materials Science and Engineering, Nanyang Technological University, Singapore (2)Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Singapore * lead presenter
Resume : The realization of artificial synapses for neural networks require analog weights to be programmable as the device conductance via blind update and access operations. However, most electrostatic memory devices are bi-stable in nature which are only useful for digital single bit storage. Memristors and memdiodes belong to the class of iontronics which utilizes ion-assisted switching mechanisms to achieve programmable device conductance. Non-stoichiometric tin oxide thin films are utilized in a rich repertoire of iontronics due to the low oxygen vacancy defect energy. In this study, atomic layer deposition was utilized to deposit ultrathin conformal SnOx thin films for synaptic applications. First, we design and evaluate a resistive switching anodic metal/oxide (Al/SnOx) interface under high electric field. The reversible formation of interfacial aluminium oxide is believed to enable the stability of intermediate resistance states. To utilize the interface as an artificial synapse, we optimize the analog programmability and propose a proof-of-concept ternary switching memristor. A spectroscopic study conducted on the chemical states of Sn after set and reset bias suggests that the resistive switching was oxide ion-assisted in nature. Subsequently, the defective oxide/oxide Schottky barrier interface (ITO/SnOx) is explored as a photoactive memdiode synapse. The photo-activity of the memdiode in the visible spectrum can be attributed to the photon-assisted discharging of the intermediate defect states, lowering the energy barrier and device resistance. Harnessing the electric field-assisted exchange of oxide ions between the two oxide films, we demonstrate that the persistence of photoconductivity can be modulated with bias voltage known as priming pulses. Such priming activities are important device functionalities to implement bio-realistic synaptic weight updates. In this study, the oxygen deficient tin oxide thin films demonstrated promising ion-assisted switching and photomemory characteristics. An interface with an anodic metal generates a memristive device capable of achieving non-volatile analog weight changes crucial for artificial synapses. Interchanging the metal with an oxide electrode, the memdiode exhibits photoconductivity with high persistence and modulability with field-assisted defect priming.
Authors : Monica Susana Campos Covarrubias* (1), Mantas Sriubas(1), Kristina Bockute(1), Piotr Winiarz(2), Maria Gazda(2), Giedrius Laukaitis(1)
Affiliations : (1) Kaunas University of Technology, Physics Department, Studentu str. 50, LT-51368, Kaunas, Lithuania (2)Gdansk University of Technology, Faculty of Applied Physics and Mathematics, Narutowicza 11/12, 80-233 Gdansk, Poland e-mail: email@example.com
Resume : Yttrium doped BaCeO3 (BCY) enhances the proton conductivity of BaCeO3 (BCO) at intermediate-high temperatures. The addition of Yttrium increases the concentration of proton defect and the proton concentration. It is also known that the strain engineering can also be used to modify and improve the properties of proton conducting materials as the proton mobility may be enhanced by introducing strain and, therefore, changing the molecular structure (unit cell and lattice symmetry) and its properties. In this work BCO and BCY (1µm thickness) are prepared by e-beam vapor deposition at 12Å/s deposition rate at 700oC and 800oC. At those technological parameters crystallization of BCO is observed, the surface morphology is homogenous, and high density is achieved. Different substrates (alloy 600, stainless steel, Invar, and glass sealing alloy) with different thermal expansion coefficients are used to induce strain to the films and investigate the influence of strains on protonic conductivity. The research was financially supported by project no. 2017/27/L/ST5/03185 founded by the National Science Centre, Poland and Research Council of Lithuania (LMTLT), agreement No S-LL-18-3.
Authors : Bingruo Zhang (1), Nobuhisa Kamata (1), Shuichi Ogawa (1), Akitaka Yoshigoe (2), Yuji Takakuwa (1)
Affiliations : (1)IMRAM, Tohoku University, Japan; (2) Japan Atomic Energy Agency, Japan
Resume : Transition metal oxides attract a growing interest due to their exceptionally broad range of functionalities. For example, NiO has a function of steam reforming to generate H2. Furthermore, by reducing NiO passivation layers on Ni substrates, an alternative catalyst of Pt for exhaust gases of motor vehicles is expected for the clean Ni surface. In this study, therefore, the oxidation and reduction reaction kinetics on Ni(111) surface was investigated by X-ray photoelectron spectroscopy using synchrotron radiation (hv = 1100 eV) at BL23SU, SPring-8, to explore in real time the oxygen uptake and oxidation states. By analyzing the time evolution of NiO thickness, dNiO, the reduction reaction mechanism of rapid-temperature-rising annealing as well as the NiO growth reaction model based on Ni vacancies and holes is considered. When the reduction was conducted in vacuum with no H2 supply, a significant decrease of dNiO from 2 nm to ~1 nm was caused by the rapid temperature rising from 350 to 700℃, whereas dNiO remained at ~ 1nm for a long period of 3×104 s during the subsequent isothermal annealing even at 700℃, while the rapid-temperature-raising-induced decrease of dNiO under H2 atmosphere was almost the same as that in vacuum, indicating that reduction of NiO during the rapid temperature rising is governed by the diffusion of O2- enhanced by the tensile stress due to the difference in thermal expansion coefficient between Ni and NiO. In contrast, the NiO films were completely removed by the isothermal annealing at 700℃ under H2 atmosphere. This is because H2 dissociative adsorption is caused at Ni metal clusters on NiO surface, leading to H2O desorption.
Authors : Heetae Park, Seong-Uk Oh, Dokyum Kim, Taeyoung Jeong, Young-Woo Heo, Jeong-Joo Kim, Joon-Hyung Lee
Affiliations : School of Materials Science and Engineering, Kyungpook National University, South Korea 41566
Resume : As the operating temperature of solid oxide fuel cells (SOFCs) continues to decrease, they are now low enough to use stainless steel (SS) as an interconnector material. However, when the stainless is used for a long time at around 700~800 oC, Cr2O3 can be formed on the surface which significantly degrades the performance of SOFCs. In order to prevent the oxidation of SS, various kinds of coatings of spinel or perovskite structured oxides have been adopted as the anti-oxidants on the surface of SS. In this study, Mn1.5Co1.5O4 (MCO) spinel is employed for coating. The MCO powder was synthesized by the solid-phase synthesis method and pulverized into fine powders by attrition milling. The specific surface area and Zeta potential of the MCO powders were analyzed and the thermal expansion coefficient of the MCO sintered body was measured and compared with that of the SS. An appropriate amount of iodine (I2) was added to the MCO slurry for EPD coating and the microstructures of the coated films were observed. A dense film was obtained through a sintering process in which the coated film was reduced at high temperature in a reducing atmosphere and then re-oxidized in an oxidizing atmosphere. The electrical conductivity, microstructure, compositional stability of the MCO layer were analyzed after a long-term (1000 h) operation.
Authors : Jun-Woo Park*, Min-Ju Kim, Byung Gon Kim, Yoon-Cheol Ha and Sang-Min Lee
Affiliations : Korea Electrotechnology Research Institute (KERI), Changwon 51543, Republic of Korea
Resume : Recently, lithium-ion batteries (LIBs) have been applied to large-scale devices such as electric vehicles and energy storage systems (ESSs), requiring high energy density and long cycle life. The use of organic electrolytes in lithium ion batteries in such large-scale devices has some safety issues. Organic electrolytes have a high ionic conductivity, but there are many risks of leakage, explosion and ignition due to the decomposition reaction of the electrolyte. As a promising solution to this issues, the use of a solid electrolyte have been proposed. In contrast to organic-based liquid electrolytes, all-solid-state lithium batteries (ASLBs) with a solid electrolyte are considered safe because of their non-flammability. These solid electrolytes have the advantages of high stability and high energy density, but they have a disadvantage of very low ionic conductivity at room temperature. In this work, we prepared sheet-type Li6PS5Cl-infiltrated electrode that has high capacity, even though it has high loading value. We propose two solutions to ensure that SE materials are evenly distributed and sufficiently infiltrated into the porous structures of LIB electrode. First, we aimed to reveal the effects of solid electrolyte solution vaporization on the solid electrolyte content in the thick electrode for ASSBs. The performance of the cells at different temperatures were compared. The electrochemical performance of ASSBs employing the LPSCl-infiltratred SEs is dependent on the LPSCl content, and it is noticeably high at higher temperatures that cause molecular motion. Therefore, it should contain more LPSCl in cathode. The NCM622 electrode infiltrated LPSCl at 90oC show reversible capacity of 177mAhg-1(5.5mg/cm2) and 136mAhg–1(17mg/cm2) at 0.05C, 55oC. We also prepared three different active materials having different particle size. The porous electrode which is made by mixing different sized active materials(DS-AM) absorbs SE solution. This absorb effects explain the capillary phenomena. The mixed DS-AM electrode demonstrated higher capacity than non-mixed DS-AM electrodes due to the improved ion transport path.
Authors : M. Schaube, R. Merkle, J. Maier
Affiliations : MPI for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
Resume : Surface point defects represent centers of enhanced energy and thus enhanced reactivity. For example, the oxygen exchange rate of Gd- and Pr-doped ceria was found to increase strongly with dopant concentration, which increases the concentration of oxygen vacancies (VO..) in case of Gd, and VO.. as well as Pr3+/4+ redox active centers for Pr doping. Here, oxidation kinetics of CO and CH4 as test reaction is studied on systematically Pr, Gd, Nb–doped ceria, and Y- and Pr–doped zirconia. CO and CH4 oxidation proceed via the Mars–Van–Krevelen mechanism; the rate–determining step involves the reaction of adsorbed CO+ with surface layer oxygen, followed by fast CO2 desorption and VO.. formation. Under certain conditions, the competition of oxygen consumption by CO and catalyst re-oxidation by O2 leads to a kinetically determined decreased effective oxygen partial pressure (pO2,eff) inside the catalyst particles, as evidenced by the increased steady state oxygen deficiency. This accelerates the oxygen incorporation until CO oxidation and O incorporation rates are balanced. Samples with lower Pr content exhibit lower pO2,eff values. The presence of pO2,eff affects also the apparent reaction orders. No decreased pO2,eff appears during methane oxidation, because the CH4 oxidation branch is slower than the oxygen incorporation.  J. Maier, Chem. Eur. J. 2001, 7, 4762  M. Schaube et al., J. Mat. Chem. A 2019, 7, 21854  M. Schaube et al., submitted
Authors : R.Pascu, A. Matei, B.Sava, Fleaca C., A. Lazea Stoianova, A. Trefilov, R.Patru
Affiliations : 1.National Institute for Laser Plasma and Radiation, Atomistilor Str.409, 077125 Bucharest- Magurele, Romania 2. National Institute of Materials Physics, Atomistilor Str.409 A, Bucharest- Magurele, Romania
Resume : Cubic fluorite structures of lanthanum strontium manganite (La0,7Sr0,3)0,95MnO3-/8YSZ (LSM) thin films are deposited on Pulsed laser Deposition (PLD) at 500C and 600C, at different number of pulses (90.000 pulses for 8YSZ and 100.000 pulses for (La0,7Sr0,3)0,95MnO3-) like cathode for µSofc and sensing electrode for potentiometric oxygen sensor on different substrates (Si(100) and Ti). The microstructure, the composition and the crystalline/ phase of the films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS); optical properties, electrical and electrochemical measurements are used to optimize the performance of such subansamblies. It was obtained uniform cubic crack free structures with good adhesion on cathode /electrolyte. Keywords: Lanthanum Strontium Manganite (LSM), Thin film cathode, Pulsed laser Deposition (PLD), Cubic Fluorite Structure, Electrochemical devices.
Authors : Arbi FATTOUM, Amira SENDI, Rolando PEDICINI, Alessandra CARBONE
Affiliations : Material Environment and Energy Laboratory, Science Faculty of Gafsa University 2112 Tunisia; Material Environment and Energy Laboratory, Science Faculty of Gafsa University 2112 Tunisia; Istituto di Tecnologie Avanzate per l’Energia “Nicola Giordano” Polymer Electrolyte Fuel Cells and Hydrogen Storage S. Lucia sopra Contesse, 5 - 98126 Messina - ITALY; 3 Istituto di Tecnologie Avanzate per l’Energia “Nicola Giordano” Polymer Electrolyte Fuel Cells and Hydrogen Storage S. Lucia sopra Contesse, 5 - 98126 Messina - ITALY
Resume : For fuel cell application, we investigated Proton conducting composite membranes of sulfonated polyether ether ketone (s-PEEK) reinforced by two various clays (a commercial montmorillonite and a home purified one) which we introduced at various clay Wt%; varying from 0 to 20Wt% of clay. We conducted various physic-chemical characterizations such as X-Ray diffraction (XRD), Scanning electron microscopy (SEM), ion exchange capacity (IEC), water uptake (WU), ionic conductivity measurements at various relative humidity conditions. The XRD patterns showed typical peaks of the clay confirming the effective introduction and the stability of the clay even after the thermal and the acid treatment of the membranes. The IEC measurements showed increased values by introducing the clay at around 5 wt% and a progressive reduction occurs with the increase of the clay amount. The WU reported at different temperatures showed different behaviours depending on the clay used. The ionic conductivity showed better values for the 15 Wt% sample for both types of clay. Fuel cell tests have been conducted with the 15 Wt% clay s-PEEK membranes. For this we used home-made electrodes by spraying the catalytic ink onto a commercial gas diffusion layer (GDL) and we made the Membrane-Electrodes Assemblies at 10Nm. Fuel cell tests, were carried out in a commercial 25cm2 single cell at 80°C, and with humidified H2/air (75-100% RH). The performance of the fuel cell are in agreement with the proton conductivity results, in fact the recast membrane reaches the best performance followed by the composite membranes which present comparable performance. The reduced performance of composite membranes is attributed to the increase of the cell resistance, in accordance with the proton conductivity measurements. It is to notice that reducing the relative humidity from 100% to 75% maintains the trend of the cell resistance and the open circuit voltage (OCV); the composite membranes have higher cell resistance and lower OCV than the pure s-PEEK membrane. The 15% home purified Clay based membrane maintains the performance quite the same, meaning a less sensitivity to the reduction of relative humidity.
Authors : Wolfgang Stein
Affiliations : SURFACE System technologya GmbH Co KG
Resume : New materials or advanced functional films are always dedicated for specific aplications. Very often either the substrate material or the film material are strongly sensitive against normal environmetal conditions. Even if the components of such deposition are not sensitiv against such attac, the interfacing between substrate and film is effected from such influence. The solution in material research for such problems is an isolation of such substrate under strongly controlled atmosphere, which can be achieved with the use of glove boxes with integrated gas cleaning systems. The user interacts via isolation gloves to handle sensitive materials in the glove box wich are introduced to it via integrated load lock ports. The combination of such controlled work bench to any kind of deposition system is a problem, because normally no easy way exist to transfer such materials from a glove box into separate deposition systems. Only a fully protected connection from such glove box to the deposition system allows an undisturbed transfer. But standard deposition systems are not prepared for such transfer. SURFACE offers now fully integrated process systems which have a complete glovebox built in. In addition the complete design of such system recognizes the reduction of handling performance of the user caused by the thick gloves and its limited taktile sensitivities. Any services on such deposition system is generated from the atmosphere side, without disturbing the conditions of the contolled atmoshere in the glove box. The fully integrated style of the glove box reduces also the necessary floor space of such comlete set-up in the lab. As an excample : the total foot print of a complet PLD Glove Box system including big Excimer laser, its gas cabinet, the process automation system with user interface, the vacuum chamber, cooling chiller and the gas control cabinet fits to a floor space of 2,5m x 0,8m and includes already the glove box workstation with a working width of 1 to 1,5 m. Exambles for such integrated systems are presented.
Authors : Songyuan Geng, Federico Raffone, Clotilde Cucinotta, Nicholas Harrison
Affiliations : Imperial College London
Resume : Revealing the detailed atomistic and electronic structures at the solid-liquid electrified interface has been a major focus in electrochemistry and theoretical investigations through computational simulation. However, previous simulations are largely limited in investigating single aspects of electrochemical transformation at the interface and cannot provide a comprehensive and realistic modelling of the interface nanostructure. My project focuses on improving the depiction of the electronic structure of the electrified interface and overcoming the difficulty for applying higher level DFT hybrid functionals for simulations in complex system due to high computational cost. The first stage of the project focuses on improving the accuracy of density description of an already-generated PBE-level ab initio molecular dynamic simulation on a realistic and large system of the interface. Sample snapshots are taken from the AIMD simulation and a survey of various hybrid functionals, such as B3LYP and PBE0, are applied to the sample snapshots. With the higher accuracy density profile, a DFT+U correction is applied to the system to gain more insights of the electronic structure. The resulting new description of the electronic structure is then compared with experimental spectroscopic data, including FTIR. The future prospect of the work will include performing constrained DFT AIMD for the complex system with the newly generated high accuracy density profile.
Authors : More, Pawan P., Puguan, John Marc C., Kim, Hern *
Affiliations : Myongji University, South Korea
Resume : Electrochromic material devices (ECDs) development aims to decrease power consumption while increasing the variety of desired colors. Electrochromic smart windows can be used in cars or buildings to adjust brightness or in spacecraft to moderate the intense thermal fluctuations by switching between light/infrared transmission and reflection. Electrochromic materials and devices change their optical properties in a reversible and persistent way under an applied voltage. Organic polymers show high color efficiency and a huge range of colors but suffer from limited stability, particularly when exposed to the ambient environment. Using metal-organic frameworks (MOFs) as an electrochromic material, MOFs offer enormous structural and chemical diversity being constructed from metal/metal cluster centers and organic linkers in countless combinations. The deliberate insertion of redox-active naphthalene diimide (NDI) ligands into the versatile family of metal-organic frameworks, MOF can be switched reversibly from transparent to dark. Zinc (Zn) metal center is integrated with the NDI and viologen moiety. MOFs, known to be porous coordination polymers, are crystalline coordination networks consisting of metal ions/clusters and organic linkers. Due to its porosity ions can easily mobilize, this motion increases the scope of multicolor functionality, quick response and reversibility. While typical MOF has one reduction state, our viologen-functionalized NDI may give rise to multi reduction states, which means multiple colors can be observed. These MOF films were deposited on ITO substrate which exhibit cycling stability unrivaled by organic linkers to significant optical contrast in a lithium-based electrolyte.
Authors : Stefan Reuter, Andreas Nenning, Alexander Opitz, Jürgen Fleig
Affiliations : TU Wien, Insititute of Chemical Technololologies and Analytics
Resume : The characterization of three electrode cells with a properly placed reference electrode (RE) offers the possibility of measuring I-V-curves and impedance spectra of a single electrode. This technique is widely used in aqueous electrochemistry, but is rather difficult to apply in solid state electrochemical cells. There, most designs presented in literature suffer from artefacts due to inevitable small imperfections in fabrication, or frequency-dependent current distributions. In this contribution, we present a newly developed cell design, with the RE placed onto a protrusion of the electrolyte. This approach minimizes artefacts, and sample fabrication is comparatively simple. Here, we use this design to characterize model cells with porous La0.6Sr0.4FeO3-δ (LSF) electrodes. Half-cell spectra were acquired in different oxidizing and reducing atmospheres, and under electrochemical bias. Data quality allows fitting the spectra analytically with a transmission-line type equivalent circuit, that delivers information on the surface catalytic properties, chemical capacitance, and ionic conductivity of the material. The obtained results are consistent with literature data of LSF, thus demonstrating the strength of the chosen cell geometry. In conclusion, we can provide guidelines for fabrication and material selection for three-electrode cells with solid electrolytes to obtain artefact-free I-V-curves and impedance spectra under electrochemical polarization of single electrodes.
Authors : Zonghao Shen* (a), Ji Wu(b), Guillame Cazaux (a), Matthew W. Shorvon(a), Stephen J. Skinner(a)
Affiliations : (a) Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ, UK (b) Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
Resume : Recently partially substituting oxygen with nitrogen in ternary transition metal oxides is of growing interest because introducing a nitride anion (N3-) within the oxide anionic (O2-) sublattice can result in interesting modification of properties , e.g. optical properties, magnetic properties, electronic, dielectric and thermoelectric behavior etc. Among the oxynitrides, the perovskite-type system has received the most attention due to its structural flexibility and many investigations have been conducted on this structure type AB(O,N)3, where A = Rare Earth, B = Transition Metal. CeNbO4+δ (δ = 0, 0.08, 0.25 and 0.33), because of the wide range of oxygen non-stoichiometries, has attracted considerable interest as a fast oxide ion conductor in solid oxide fuel cells (SOFCs) . Oxynitride formation of the CeNbO4+δ precursor, which has not been reported in literature, may modify the optical properties as well as the electronic and ionic transport properties of the materials. Thus, this Ce-Nb-(O,N) system could be of particular interest for compositional, optical and electrical studies. In this work single phase cerium niobium oxynitride has been successfully synthesised via the thermal ammonolysis method and a variety of characterisation techniques have been performed to study its crysatallographic structure, physical and chemical properties. Complex multi-stage redox processes of this material was observed at elevated temperature and the band gap found to decrease significantly due to the incorporation of nitrogen into the oxygen sublattice, theoretically and experimentally confirmed, which indicated it could be a promising candidate for photocatalytic applications. References  A. Fuertes, J. Mater. Chem., 22 (2012) 3293  R. J. Packer and S. J. Skinner, Adv. Mater., 22 (2010) 1475
Authors : Andreas Varellas
Affiliations : Prof. Alexei Kornyshev; Prof. Fernando Bresme; Dr. Tom Reddyhoff
Resume : In recent years, there have been important applications envisioned that would require small-scale devices to be implemented. An example of such are microelectromechanical systems (MEMS) used as energy harvesters. A significant challenge in the realisation of such devices is finding novel ways of lubrication, due to the high friction and wear present. In this work, Room Temperature Ionic Liquids (RTILs) are proposed as a solution to this problem, due to their numerous tuneable properties. The vapour pressure of ionic liquids is also very low, thus almost no liquid is lost due to evaporation. Additionally, their ionic behaviour is a topic with major scope for enhancing or controlling the compound’s properties through applied electric fields. Finally, these liquids are also able to be characterised through molecular simulations. In order to explore the friction properties at the nanoscale of RTILs, a MEMS tribometer has been developed. This consists of a miniature thrust pad bearing interface, manufactured using semiconductor fabrication techniques. Furthermore, this experimental rig is to be modified to apply charge on the system. In this way, the charged behaviour of RTILs can be studied. Thanks to previous molecular simulation work done at Imperial, the experimental results can be compared and validated. Following the conclusions of this work, applications will be explored in the nanoscale lubrication properties for MEMS devices and energy harvesters.
Authors : Kudyakova V.S., Politov B.V., Markov A.A., Suntsov A.Yu., Kozhevnikov V.L.
Affiliations : Institute of Solid State Chemistry UB RAS, Yekaterinburg, Russia
Resume : Complex non-stoichiometric oxides with doubled perovskite-like structure attract much attention due to a combination of such functional properties as electrical and ionic conductivity, magnetic properties, and oxygen exchange. Coexistence of oxygen vacancies with transition metals promotes these compounds to be sensitive even to slight changes in temperature and gas-phase composition. Thus oxygen content affecting to defect equilibrium and crystal structure becomes a crucial factor to form the required characteristics of oxides. Therefore a comprehensive study of defect formation processes by number of theoretical and experimental methods is essential to govern the desired properties. In the present work solid solutions based on PrBaM2O6–δ, with M=Co or Mn, were obtained through the glycerol-nitrate precursors. Coulometric titration data were utilized in order to simulate the isothermal dependences of oxygen content in oxides vs. partial pressure. Equilibrium concentrations of the corresponding defects were calculated from the model proposed. Experimental data on high-temperature magnetic susceptibility combined with the defect structure were applied to explain some features of electric transport properties. In particular, the phenomenon of the so-called “spin blockade” was established at high temperatures. This work was supported by the Russian Science Foundation under grant №19-79-10147
Authors : Md Raziun BIN MAMTAZ, Alessio BELOTTI, Jiapeng LIU, Jing WU, Francesco CIUCCI
Affiliations : Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, SAR, China; Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, SAR, China; Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, SAR, China; Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, SAR, China; Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, SAR, China
Resume : In situ exsolution of nanocatalysts to enhance the catalysis of fuel in solid oxide fuel/electrochemical cells (SOFCs and SOCs) is an increasingly favored strategy. Here we report nonmetal cations (Silicon and Phosphorus) as a secondary dopant in the B-site of the strontium titanate perovskite, improving the electrochemical performance and exsolution of transition metal. Using ab initio computations, the energetics and the diffusional properties of the materials were studied. The improved exsolution predicted in theoretical studies agrees with the excellent area-specific resistance of 0.050 Ωcm2 (5% Si-doped) and 0.047 Ωcm2 (5% P-doped), measured for the optimum compositions (Sr0.8Ti0.85Ni0.1(Si/P)0.05O3-δ. Additionally, these materials showed excellent electrochemical and thermal stability, performing steadily at the low polarization resistance for over 100 hours in the imitated fuel environment (3% humidified H2). XPS studies reveal simultaneous oxidation of the nonmetal dopants during exsolution (or reduction) of Ni, which aids the exsolution process. The exsolved nanoparticles were characterized using SEM and EDS. This work proposes a cost-efficient improvement which was previously done through expensive rare earth metal dopants, which hindered exsolution as a trade-off to electrical conductivity improvements. This is the first time, to our knowledge, nonmetal dopants in perovskite were utilized as an ‘exsolution-helper’.
Authors : Sohee Kim(1,2)*, Tae-Ho Kim(1), Kyu Tae Lee(2)
Affiliations : (1) Membranes Research Center, Korea Research Institute of Chemical Technology, Republic of Korea (2) School of Chemical and Biological Engineering, Seoul National University, Republic of Korea
Resume : Ultraviolet (UV)-crosslinked solid-state polymer electrolyte system (SSPE) based on poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block co-polymer was developed for applications in all solid state batteries. Cross-linkable polymeric precursors with four functionality were synthesized by reacting terminal end groups of PEO-PPO block co-polymer (Tetronic 90R4) and 4-vinylbenzyl chloride. The crosslinked SSPEs were obtained by solvent free UV initiated polymerization of the mixtures containing cross-linkable polymeric precursors, divinyl benzene (DVB), and photo-initiator. In order to achieve a good balance between electrochemical and mechanical properties, the number of PEO-PPO units and the feed ratios of DVB and liquid electrolyte in the SSPEs were precisely controlled. The resulting SSPE showed high ion conductivity of 1.62 mS/cm at room temperature. Thermal stability of the crosslinked SSPEs were evaluated by thermogravimetric analysis (TGA) and different scanning calorimetry (DSC). An Na-Na symmetric cell assembled with SSPE exhibited good electrochemical performance.
Authors : Chanho Kim, Keemin Park, Seungwoo Lee, Myungwoo Ryu, Joonhyeok Park, Jiwoon Kim, Heesung Yoon, Ungyu Paik, Taeseup Song
Affiliations : Department of Energy Engineering, Hanyang University
Resume : Forming the La0.6Sr0.4CoO3-δ (LSC) nanoparticles on the cathode surface has been intensively explored since this enables the high performance of solid oxide fuel cells by enhancing the charge conductivity. However, the 0D structure still has limitations such as inefficient charge conducting path or fading the reaction site due to the excessive loading level for ensuring the continuity of La0.6Sr0.4CoO3-δ (LSC) nanoparticles. In this study, we report the uniformly grown ultrathin 2D La0.6Sr0.4CoO3-δ nanosheet for effectively enhancing the cathode performance. Continuous 2D figure more efficiently enlarges the reaction site with low loading level compared to the conventional 0D figure. 2D nanosheet structure is ideal figure for enlarging the charge conducting path because it has more contact with cathode scaffold compared with any other structures. Solid oxide fuel cell with 2D La0.6Sr0.4CoO3-δ nanosheet exhibit quite enhanced power density of 1.2 W cm-2 at 600 oC by facilitating the conductivity of charge within the cathode. Our strategy provides the instructions for the high-performance solid oxide fuel cells through the cathode structure design.
Authors : Sungmin Kim1, Seunggun Choi1, Woobin Joo2, Jaeik Kim1, Heeju Seo1, Yeongjin Koh1, HyukSu Han3, Heesung Yoon1, Ungyu Paik1,2,*
Affiliations : 1. Department of Energy Engineering, Hanyang University, Seoul, 133-791, South Korea; 2. Department of Nano Semiconductor Engineering, Hanyang University, Seoul, 133-791, South Korea; 3. Department of Materials Science and Engineering, Hongik University, Sejong-ro 2639, Sejong, South Korea
Resume : Formation of the gadolinium-doped ceria electrolyte layer on the yttria-stabilized zirconia electrolyte layer as a protection layer has been researched for its use at low operation temperature. The dense gadolinium-doped ceria barrier layer could reduce the diffusion of Sr from the cathode material such as La0.6Sr0.4Co0.2Fe0.8 and enables stable and high performance. However, the limited sintering temperature to avoid side reactions between the two electrolytes incurs the low density of the electrolytes. In this study, we report a facile method for the fabrication of dense gadolinium-doped ceria/yttria-stabilized zirconia bilayer electrolyte at low sintering temperatures. Even at 1250 °C, a thin and highly dense bilayer electrolyte structure could be achieved by employing an isostatic pressure process on the dip-coated electrolyte layers and anode support substrate. This dense bilayer electrolyte system exhibits high power density of 1.251Wcm−2 at 650 °C and high stability for 100 h. These improvements in performances are attributed to the greatly reduced porosity (< 2.5%) of the bilayer electrolyte.
Authors : D.A. Agarkov2,5, M.A. Borik1, G.M. Eliseeva2, V.A. Kolotygin2, A.V. Kulebyakin1, I.E. Kuritzyna2, E.E. Lomonova1, V.A. Myzina1, P.A. Ryabochkina3, N.Yu. Tabachkova1,4, T.V. Volkova3
Affiliations : 1Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia 2Institute of Solid State Physics of the Russian Academy of Sciences, Chernogolovka, Russia 3Ogarev Mordovia State University, Saransk, Russia 4National University of Science and Technology «MISIS», Moscow, Russia 5Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, Russia
Resume : Zirconia based materials are known for having high values of ionic conductivity at high temperatures, therefore, they are used as a solid electrolyte in the construction of solid oxide fuel cells (SOFCs). In this work, we studied the effect of the chemical composition of zirconia based crystals on their phase composition, local structure and transport characteristics. A comparative analysis of two systems was carried out: zirconia stabilized only with ytterbium oxide and zirconia stabilized together with ytterbium and scandium oxides. Crystals of (ZrO2)1-x(Yb2O3)x and (ZrO2)1-x(Sc2O3)x(Yb2O3)y were grown by directional crystallization of a melt in a cold container using direct high-frequency heating. Investigations of the phase composition were carried out by Raman scattering and x-ray phase analysis. The conductivity of the crystals was measured by impedance spectroscopy. The local structure of the grown crystals was studied by optical spectroscopy using Eu3 ions as a spectroscopic probe. This work was performed with the financial support of the Russian Science Foundation. The synthesis and the study of the structure and transport properties of the (ZrO2)1-x(Yb2O3)x crystals were supported with Grant 16-13-00056. The synthesis and the study of the structure and transport properties of the (ZrO2)1-x(Sc2O3)x(Yb2O3)y crystals were supported with Grant 19-72-10113.
Authors : Gyeogn Duk Nam, Jinsil Lee, Ga Hyeon Lee, Soomin Choi, Sung Kyun Kim, Hohan Bae, Sun-Ju Song, Jong Hoon Joo
Affiliations : Department of Advanced Material Engineering, Chungbuk National University, 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Department of Advanced Material Engineering, Chungbuk National University, 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Department of Advanced Material Engineering, Chungbuk National University, 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Department of Advanced Material Engineering, Chungbuk National University, 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Department of Advanced Material Engineering, Chungbuk National University, 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Ionics Lab, School of Materials Science and Engineering Chonnam National University, Buk-gu, Gwang-Ju 500-757, Korea; Ionics Lab, School of Materials Science and Engineering Chonnam National University, Buk-gu, Gwang-Ju 500-757, Korea; Department of Advanced Material Engineering, Chungbuk National University, 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea;
Resume : In recent years, the ceramic oxygen transport membranes have attracted substantial attention due to their high selectivity and permeability for oxygen separation from air. A lot of efforts have been dedicated to the development of the single-phase membrane with ABO3 structure due to their outstanding oxygen permeability. Despite these great efforts, perovskite materials cannot be applied commercially due to their thermo-mechanical and chemical instabilities and gradual deterioration of performance when CO2 is used as sweep gas. To overcome these obstacles, many researches have shown increased attention in dual-phase membranes based on fluorite structure material since the fluorite oxides used as an electrolyte of solid oxide fuel cell are mechanically and chemically stable under the real operating atmosphere. However, in terms of the oxygen permeability, oxygen permeation flux produced by dual-phase membrane is noticeably lower than 5- 10 mL∙cm-2∙min-1 that is required to ensure the industrail target of oxygen transport membrane. In this study, the membrane comprises a mixture of gadolinium doped ceria (Ce0.9Gd0.1O2-δ, GDC) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) with a volume ratio of 70:30. The perovskite structure is applied as the active materials of ceria-based membrane to enhance the surface exchange reaction on the membrane surface. The highest oxygen permeation flux of up to 10 mL∙cm-2∙min-1 was achieved with the dual-phase membrane at 1000 oC at the air/He condition. The excellent stability was also observed in time dependence of oxygen permeation test where pure CO2 was used as the sweep gas.
Authors : Hye Ri Kim, Ga Hyeon Lee, Gyeong Duk Nam, MinSik Jeong, Min Hyung Lee, SeKwon Oh, Dongju Lee, Jong Hoon Joo
Affiliations : Department of Advanced Material Engineering Chungbuk National University 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Department of Advanced Material Engineering Chungbuk National University 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Department of Advanced Material Engineering Chungbuk National University 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Department of Advanced Material Engineering Chungbuk National University 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Surface R&D Group, Korea Institute of Industrial Technology, Incheon-si, 406-840, Republic of Korea; Surface R&D Group, Korea Institute of Industrial Technology, Incheon-si, 406-840, Republic of Korea; Department of Advanced Material Engineering Chungbuk National University 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea; Department of Advanced Material Engineering Chungbuk National University 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea
Resume : The production of hydrogen has been extensively studied since hydrogen is an ideal energy, high quality and clean energy carrier. Currently, the hydrogen is mainly produced by the fossil fuels or other carbon-based fuels. However, the production technology of hydrogen via the fossil fuels causes global warming by emitting environmental pollutions such as CO, CO2, and CH4. Thus, a lot of efforts have been dedicated to the production of hydrogen through the clean renewable energy sources such as water, biomass. Among these technologies, an alkaline water electrolysis has been considered as the promising candidate for the green hydrogen technology. The high catalytic activity and durability of the electrodes should be guaranteed for commercialization of alkaline water electrolysis. Platinum group metals have the best catalytic activity for alkaline water electrolysis, but it is a limitation to commercialization due to high cost and their dissolution during the oxygen evolution reaction (OER). To overcome the problems, nickel-based metals that are stable during OER have been investigated as electrodes for alkaline water electrolysis. The perovskite oxides are also attractive candidates as catalysts to overcome the low current density and durability. In this study, metal/oxides composite electrode with high activity and durability was fabricated by high-temperature processing. The effects of metal/oxides composite electrode on OER and HER has been systematically studied via the electrochemical measurement analysis.
Authors : Se-Hun Kim
Affiliations : Jeju National University
Resume : In this study, we obtained experimental results similar to the isotope substitution effect by using the proton irradiation of K(H0.47D0.53)2PO4 (DKDP) ferroelectric single crystals. Temperature dependence of dielectric constants showed that the ferroelectric phase to paraelectric phase transition temperature increased from 175 K to 195 K of approximately 20 K after the proton beam irradiation. It was observed that the vibration mode P(OD)2 was changed from 893 to 884 cm-1 in Raman spectroscopy. In 1H Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) experiments, the isotropic chemical shift after proton irradiation decreased from 14.46 to 14.32 ppm, which is indicative of the change of the O-H…O the equilibrium distance of hydrogen bonds estimated as 1.60066 Å and 1.62228 Å before and after the proton irradiation, respectively. It was observed that the Full width at half maximum (FWHM) line width also decreased from 563 to 244 Hz in 1H MAS spectral line shape, which is indicative of obeying the displacive phase transition model.
Authors : Christian Rodenbücher1, Dominik Wrana2, Benedykt R. Jany2, Franciszek Krok2, Carsten Korte1
Affiliations : 1 Institute of Energy and Climate Research (IEK-14), Forschungszentrum Jülich, 52425 Jülich, Germany; 2 Marian Smoluchowski Institute of Physics, Jagiellonian University, 30-348 Krakow, Poland
Resume : Solid oxide cells (SOCs) are key elements for hydrogen-based energy storage in a future sustainable energy system. In order to design reliable devices, a detailed understanding of their potential failure mechanisms is needed. In particular, when SOCs are operated in electrolysis mode, the presence of gradients in the electrical and chemical potential can lead to local reduction or segregation which would limit the lifetime of the cells. Using single crystals of the mixed electronic-ionic conductor SrTiO3 and the ionic conductor Y-stabilized ZrO2 (YSZ) as model materials for SOC electrodes and electrolyte, we analyze electroreduction effects under vacuum conditions. We demonstrate that in SrTiO3 single crystals, dislocations act as easy reduction sites thus establishing filamentary conductance paths during electroreduction, while in YSZ an inhomogeneous reduction front evolves following the electric field lines. When prolonged electroreduction is applied in Hebb-Wagner type geometry, a stoichiometry polarization of the oxygen activity is established in both investigated materials. In SrTiO3, this leads to the sublimation of Sr from the surface close to the cathode leaving behind nanoporous TiOx thus revealing a significant degradation mechanism which has not been considered in detail before. Also in YSZ, the ongoing electroreduction results in segregation phenomena related to the evolution of new oxygen-depleted ZrOx phases on the nanoscale eventually altering the oxide’s properties irreversibly.
Authors : Nikolay Ovsyannikov, I. Krasnikova, M. Pogosova, A. Sanin, N. Akhmetov, K. Stevenson
Affiliations : Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld. 1, Moscow, Russia 121205
Resume : Ion-conducting electrolyte accounts for safety and energy density of hybrid-flow and all-solid state batteries. Since liquid electrolytes are highly flammable, ceramic electrolytes attract research attention due to relatively high ionic conductivity and stability. However, ceramics lack mechanical integrity and flexibility during cycling. Therefore, we propose using composite membranes based on conductive ceramics and polymer binder. We selected polyvinylidene fluorine (high electrochemical stability window) and Li1.3Al0.3Ti1.7(PO4)3 (LATP) ceramics (facile synthesis; ionic conductivity up to 7·10-4 S cm-1) as a components of composite electrolyte. We optimized the synthesis procedure of the material and studied in detail electrochemical characteristics varying membranes’ composition and outer factors (temperature, working environment). The composite membranes possess the ionic conductivity up to 10-5 S cm-1 at 23 °C in dry from which may be further improved up to 10-4 S cm-1 at 23 °C during soaking in appropriate solvent, the electronic conductivity is 10-10 S cm-1 and the electrochemical stability window is 1.9 – 4.7 V vs. Li/Li+. The samples are applicable as an electrolyte in all-solid-state batteries and lithium hybrid-flow batteries due to sufficient ionic conductivity and high mechanical integrity and flexibility.
Authors : Jong Heon Kim, Cheng-Fan Xiao and Hyun-Suk Kim∗
Affiliations : Advanced Nanomaterials and Devices Laboratory, Chungnam National University (Materials Science and Engineering, 99, Daehak-ro(St), Yuseong-gu, Daejeon, 34134, Korea)
Resume : The development of miniaturized and flexible energy storage devices have been intensively studied for future electronics such as portable and wearable devices. However, since the conventional secondary batteries adopt a liquid or gel electrolyte, so that fabrication of the micro-sized batteries is limited. In this regard, all-solid-state Li-ion thin-film batteries (ASSB) with a solid electrolyte are liquid-free battery architecture to solve this problem. However, the process temperature of ASSBs is relatively high compared to conventional liquid electrolyte based batteries. Generally, flexible devices require low-temperature processes due to the low glass transition temperature of the plastic substrate. Moreover, interfacial characteristics between electrode and solid electrolyte need to be improved. In this study, the electrochemical properties of Li-ion batteries (Li4Ti5O12/electrolyte/Li) were investigated by changing the electrolyte type, as well as the presence and absence of polymer-based separator. Also, the effects of the Al2O3 interlayer between the electrode and solid electrolyte (LiPON) were studied. As a result, the improved electrochemical characteristics were obtained for the ASSB without a polymer-based separator. Despite the fabricated ASSBs showed low electrochemical performance due to large interfacial resistance compared to batteries with liquid electrolytes, but it was improved when the Al2O3 was adopted as an interlayer.
Authors : Pravin N. Didwal, Chan-Jin Park
Affiliations : Chonnam National University
Resume : Although lithium ion batteries (LIBs) are the most fascinating systems for large scale energy storage, the conventional flammable organic liquid electrolyte limits the safety of the LIBs. In this regard, while solid state electrolyte provides the high energy density with high safety, the poor interfacial contact between electrode and electrolyte is the major issue for commercialization of the all-solid-state (ASS) LIBs. Solid polymer electrolyte (SPE) is a promising electrolyte for next generation ASSLIBs owing to their safety advantages. However, the insufficient ionic conductivity, mechanical strength, and electrochemical stability raise several queries for the practical application of SPEs. Thus, it is of immense importance to find novel SPE with superior electrochemical property and stability. The composite solid polymer electrolyte (CSPE) with poly(propylene carbonate) as host matrix with mesoporous silica nanoparticles as passive ceramic filler are capable to attain noteworthy properties. The prepared CSPE with 4wt.% of MSN filler exhibited high ionic conductivity of ~7.5×10-4 S cm-1, wide electrochemical potential window >4.8 V vs. Li/Li , high lithium transference number ~0.87, and good enough mechanical strength. Moreover, CSPE shows excellent stability with lithium metal for longer than 1000 h lithium stripping/plating cycles at 60 °C. Li/CSPE/LiFePO4 (LFP) cell delivered specific discharge capacity of 103 mAh g-1 even at high current of 1C and impressive stability over 200 cycles with small over potential. Moreover, Li/CSPE/LFP cell exhibited excellent rate capability up to 5C. Such notable electrochemical performance of CSPE is attributed to the uniform distributed highly mesoporous silica which allows large surface area for interaction with PPC matrix by forming intense polymer-ceramic phase for lithium transportation. The highly mesoporous silica reinforced CSPE offers opportunities for highly stable, lithium dendrite free-, and high energy density ASSLIBs.
Authors : S. G. Ebbinghaus, M. Breitenbach, R. Köferstein, and T. Buttlar
Affiliations : Martin Luther University Halle-Wittenberg Institute of Chemistry Kurt-Mothes-Str. 2 06120 Halle(Saale)
Resume : The direct and converse magnetoelectric effect, i.e. switching of the polarization by a magnetic field and switching of the magnetization an electrical field, are highly interesting for a large variety of applications, e.g. as sensors or in data storage devices. Here, we report on multiferroic heterostructures consisting of BaTiO3 or Ba0.5Sr0.5Nb2O6 as ferroelectric component in combination with ferrimagnetic ferrite spinels MFe2O4 (e.g. M = Co, Ni) or ferromagnetic metals/alloys (Co, Ni, Co1/3Fe2/3). Different classical and soft-chemistry synthesis approaches have been applied leading to 0–3- (particles embedded in a matrix) and 3–3-heterostructures (interpenetrating networks). The samples have been investigated using a broad variety of characterization techniques including XRD, SEM/EDX, impedance spectroscopy and temperature- and field-dependent magnetic measurements. The magnetoelectric effect has been studied in detail with respect to different compositions, temperature, external magnetic field and frequency.
Authors : Abdessalem Aribia, Jordi Sastre, Xubin Chen, Ayodhya N. Tiwari, Yaroslav E. Romanyuk
Affiliations : Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland.
Resume : LiCoO2 is the most commonly used transition metal oxide cathode in lithium-ion batteries because of its high operating voltage (~ 4V), ease of synthesis, and good cycle life. However during fabrication and device operation Co and oxygen diffusion into the electrolyte occurs. This results in decreased energy and power density, and increased impedance. The issue is exacerbated in the case of thin-film solid-state electrolytes, which requires a heating step during fabrication (e.g. Li7La3Zr2O12). The interdiffusion of the electrolyte and the LiCoO2 forms a strongly ionically resistant interlayer. One way to suppress the chemical instability and reactivity with the electrolyte is to coat the surface of the cathode with inert oxides. An ALD process for Nb2O5 is presented, which acts as a coating for the thin-film LiCoO2 cathode fabricated by magnetron sputtering. To investigate the electrochemical performance, liquid electrolyte half-cells were assembled with Li foil as anode. In this first step, the focus lies on the power density of the modified cathodes. By investigating cathode and coating thickness, increased rate performance could be demonstrated. Such Nb2O5-coated LiCoO2 cathodes showed at 20 C charge rate, 80% capacity retention relative to 1 C, which for uncoated cathodes, no capacity remained at that rate.
Authors : Aneta Wardak(1)*, Witold Chromiński(2), Dominika Kochanowska(1), Marta Witkowska-Baran(1), Bartłomiej S. Witkowski(1), Gabriela Janusz(1), Małgorzata Lewandowska(2), Andrzej Mycielski(1).
Affiliations : (1)Institute of Physics of the Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland; (2)Warsaw University of Technology, Faculty of Materials Science and Engineering, ul. Wołoska 141, 02-507 Warsaw, Poland. * lead presenter
Resume : CdTe-based compounds are recently studied with the intention to be used in the detection at room temperature of high energy radiation – X-rays and gamma-rays. For this application the uniformity of a crystal structure and an electric field within the bulk crystal is required. Tellurium inclusions are typical for CdTe obtained by the Bridgman method. In some of the crystals, grown under cadmium-excess, Cd inclusions were found. Pockels electro-optic effect studies present that in the vicinity of Te inclusions the internal electric field is disturbed, whereas Cd inclusions have no impact on this issue. Transmission infrared microscopy demonstrates that Te inclusion does not cause micro fractures in CdTe lattice. However, a Cd inclusion with a similar size as Te, generates micro cracks in the area which is few times bigger than the inclusion itself. Thus, Cd defect consists of the core (inclusion) and the six branches (cracks). We link the six directions of the cracks with the three easy-cleavage planes (110) in the zinc blende structure. SEM observations and the electron backscatter diffraction (EBSD) techniques allow for the detailed investigation of regions around the inclusions and other types of defects, like grain boundaries, as well as to determine changes in internal stresses in the vicinity of inclusions.
Authors : Dr. Zachary Brown, Prof. Mauro Pasta
Affiliations : University of Oxford, Department of Materials
Resume : Improving the energy density of lithium-ion batteries by replacing a graphite anode with lithium metal anode is heavily desired.1 The garnet (LLZO) solid electrolytes are promising candidates to protect lithium metal due to their high lithium-ion conductivity and high elastic modulus, however, the interfacial chemistry between LLZO/Li is poorly understood.2-4 In this work, LLZO electrolytes of >98% theoretical density were prepared with Field Assisted Sintering Technology. The solid state electrochemistry of LLZO with lithium and blocking electrodes is characterized using electrochemical impedance spectroscopy. Further, investigation of interfacial phenomena between LLZO and Li metal using a suite of surface characterization techniques will be discussed in detail. References 1. Liu J., Bao Z., Cui Y., Dufek E. J., Goodenough J. B., Khalifah P., Li Q., Liaw B. Y., Liu P., Manthiram A., Meng Y. S., Subramanian V. R., Toney M. F., Viswanathan V. V., Whittingham M. S., Xiao J., Xu W., Yang J., Yang X. Q., and Zhang J. G., Nat. Energy, 4, 180 (2019). 2. Krauskopf T., Hartmann H., Zeier W. G., and Janek J. ACS Appl. Mater. Interfaces, 11, 14463 (2019). 3. Fu K., Gong Y., Liu B., Zhu Y., Xu S., Yao Y., Luo W., Wang C., Lacey S. D., Dai J., Chen Y., Mo Y., Wachsman E., and Hu L. Sci. Advances, 3, e1601659 (2017). 4. Sharafi A., Kazyak E., Davis A. L., Yu S., Thompson T., Siegel D. J., Dasgupta N. P., and Sakamoto J. Chem. Mater. 29, 7961 (2017).
Authors : B.E.Umirzakov, S.B.Donaev
Affiliations : Tashkent State Technical University
Resume : This work is devoted to the preparation of three-component Ga1-xAlxAs and Ga1-xAlxP nanofilms by varying x on the surface of GaP and GaAs by ion implantation, and their composition, structure, and properties are studied. Single crystal GaP(111) and GaAs(111) samples were chosen as objects of study. Before ion implantation, GaP(111) was irradiated under ultrahigh vacuum (P = 10-7 Pa) at T = 900 K for ~4 hours. By implanting Al+ ions with E0 = 1 keV at different doses on the surface of a GaP(111) single crystal, nanocrystalline phases and Ga0.6Al0.4P grains were obtained and their composition, crystal structures, and properties were studied. It is shown that the type and lattice parameters of a three-component nanostructure are in good agreement with those for the substrate. An analysis of the change in the parameters of the bands shows that, at d≤35–40 nm, the quantum-size effects disappear in the nanocrystalline Ga0.6Al0.4P phases. The implantation of Al+ ions with Е0 = 1 keV at a dose of D = 1017 cm–2, as in the case of GaAs, led to the uniform incorporation of Al atoms in the middle part of the irradiated GaP surface. Moreover, the Al concentration on the surface was ~30-35 at.% And the entire irradiated surface was strongly disordered. After heating at T = 900 K, a three-component compound with an approximate composition of Ga0.6Al0.4P was formed on the surface.
Authors : Nyun Jong Lee1*, Jae-Hyeon Cho2, Ju-Hyeon Lee2, Wook Jo2, and Sanghoon Kim1
Affiliations : 1. Department of Physics and EHSRC, University of Ulsan, Ulsan 44610, Korea 2. School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
Resume : Multiferroicity has great potential for the next generation electronic applications such as ferroelectric photovoltaics and next-generation memory devices. An epitaxially-grown antiferromagnetic BiFeO3 is representative material which shows the multiferroicity with single phase, while a ferromagnetic-electrically coupled material at room temperature has not been reported yet. In this presentation, we show a Pb-based perovskite which is magnetoelectrically coupled above even room temperature. Detailed x-ray absorption spectroscopy studies at both near (XAS and XMCD) and extended edges (EXAFS) have confirmed that the ferrimagnetic property of perovskite has been induced by the A-site substitution with Ni.
Authors : Lucile Bernadet (1), Carlos Moncasi (1), Marc Torrell (1), Albert Tarancón (1, 2)
Affiliations : Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy, Jardins de les Dones de Negre 1, 2nd Floor, 08930 Sant Adria de Besos, Barcelona, Spain (2) ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain
Resume : State of the art SOEC are complex structures requiring many fabrication steps and are still presenting durability issues. On one side, fuel electrodes, usually made with Ni YSZ (yttria stabilized zirconia Y2O3-ZrO2) cermets, suffer re-oxidation, Ni volatility and agglomeration and coking issues during pure CO2 electrolysis and co-electrolysis. On the other side, oxygen electrodes, usually made with La1 xSrxMO3 δ (LSM) YSZ composites or by mixed ionic-electronic conducting (MIEC) perovskite like La1 xSrxCo1 yFeyO3 δ (LSCF), are subject to delamination problem or inter-diffusion of ions. This work presents the study of symmetrical solid oxide cells made with Sr2Fe1.5Mo0.5O6−δ (SFM) electrodes. The symmetrical configuration allow a reduction of sintering steps and an improvement of the electrodes-electrolyte thermomechanical compatibility meanwhile the use of MIEC perovskite electrodes enables operations under steam electrolysis (SOEC) or co-electrolysis (co-SOEC) without the use of safe gas at the fuel electrode. YbScSZ tapes previously coated with a Ce1 xGdxO1.9 (GDC) barrier layer grown by pulsed laser deposition (PLD) were used as electrolyte supports. The sintering temperature of electrodes was optimized by means of electrochemical impedance spectroscopy (EIS) measurements in both air and H2 symmetrical atmosphere. The cell was then electrochemically characterized under SOEC and co-SOEC modes without the use of H2 as a safe gas reaching a maximum injected current density of 1.4 and 1.1 A·cm-2 respectively, at the thermoneutral voltage. The cells reversibility was proved by switching electrodes chambers composition between the cathode and anode.
Authors : Meena Ghosh, Dr. Sreekumar Kurungot
Affiliations : Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune- 411008, India
Resume : Aqueous rechargeable zinc-metal batteries (ZMBs) are emerging as safe and promising electrochemical energy storage technology. However, cycle life of ZMBs are often hampered due to the formation of undesired dendrite-like structure on the metallic zinc anode. In the current work, we have addressed this issue by employing Zn2+-integrated Nafion ionomer membrane as the separator. The membrane created by coordinating Zn2+-ions with the sulfonated tetrafluroethylene polymer chain present in Nafion, furnishes the single ion conducting electrolyte feature. As a result, the ionomer membrane facilitates the mobility of Zn2+-ions during the charge/discharge cycles and directs the uniform electrodeposition of zinc on the anode. We have demonstrated the utility of Nafion membrane in ZMBs with two different transition metal oxide cathodes; V2O5 and MnO2. Compared to the traditionally used porous separators (glass fibre paper or Celgard separator), the Nafion-based cells could endure more than 1000 charge/discharge cycles with better capacity retention. The further characterization of the post-stability anodes reveals the smooth surface of the zinc anode coupled with Nafion membrane. On the other hand, the porous separators lead to nonuniform dendrite-like surface morphology of the cycled-anodes. This indeed highlights the critical role of ionomer membrane in stabilizing the metallic anode resulting improved cycling performance of ZMBs.
Authors : Sudipta Biswas, Ananya Chowdhury, Amreesh Chandra
Affiliations : Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
Resume : As we move towards next generation applications for supercapacitors, it is imperative to characterize their performance under non-ambient and/or inconvenient environments. These include: changing magnetic field, temperature, external shocks or vibrations, etc. I will discuss the effects of all these external parameters on the device performance, which can open a new direction in the field of supercapacitor research. The strategy of exposing the supercaps to magnetic field before their real application can enhance the deliverable specific capacitance. In supercapacitors, fabricated using ferromagnetic metal oxides such as Fe2O3, MnO2, etc., nearly 170% increase in energy density, at 1 A g−1, was observed by varying the magnetic field from 0 to 5 mT. In addition, a ten-fold increase in the power density can be obtained. The observations are attributed to the changing Lorentz force and/ or magneto-hydrodynamic effects. Therefore, one may argue that size of the electrolyte ion should also be considered. It is clearly shown that this hypothesis, which predicts ‘change in specific capacitance’ by varying electrolyte, is correct. Till date, a Nernstian relation across the electrode is used to explain the super capacitive behaviour of a cell. The theoretical formulations proposed in the Gouy Chapman or the Stern models have no parameters that consider the consequences of a varying magnetic field. It is shown that the net charge flux is essentially dominated by the diffusive transport of the ions. The modified theory leads to consistent results, which are corroborated with the experimental data. In B=0 limit, the model reduces to the earlier mentioned established theoretical postulates
Authors : Aswathy M. Narayanan, Sourabh Wajhal, A. B. Shinde, P. S. R. Krishna, Arun M. Umarji
Affiliations : Materials Research Centre, Indian Institute of Science, Bengaluru, India - 560012; Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, India - 400085; Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, India - 400085; Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, India - 400085; Materials Research Centre, Indian Institute of Science, Bengaluru, India - 560012
Resume : Several non-stoichiometric transition metal complex oxides have been proposed for oxygen separation from air. Apart from the high concentration of oxygen vacancies, a favorable crystal structure with low energy migration pathways is required for high ionic conductivity at lower temperatures. Neutron diffraction having better sensitivity towards oxygen atoms can be exploited to probe the fractional coordinates and Debye-Waller factors of oxygen, even in the presence of relatively higher atomic number metals. This gives insight into the crystallographically distinct oxygen which is responsible for the high oxide ion mobility in the material under question. Herein, the structural analysis of the three different phases of strontium cobalt oxide has been performed to investigate the oxide ion mobility at room temperature in them. The three phases, namely Sr6Co5O15, SrCoO2.5 and SrCoO3-d were analyzed by means of neutron diffraction at room temperature. A combined Rietveld refinement of X-ray and neutron diffraction patterns was carried out to achieve a single structural solution. The crystallographically different oxygens which are responsible for oxide ion movement inside the lattice were identified and found to have lower fractional occupancy in addition to higher thermal parameters. Apart from diffraction studies, electrical conductivity measurements in different atmospheres were also used to characterize the oxide ion mobility in these oxides. The electrical conductivity of SrCoO2.5 was measured in air, nitrogen and oxygen atmospheres showing a difference in conductivity due to possible oxygen intake/release.
Authors : R. Rodriguez-Lamas, C. Pirovano, D. Pla, R. Jónsson, L. Rapenne, H. Roussel, O. Chaix-Pluchery, M. Boudard, C. Jiménez, Rose-Noelle Vannier, M. Burriel
Affiliations : Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, 38000 Grenoble, France; Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
Resume : Manganites in the form of thin films can present functional properties that vary largely in comparison to their intrinsic bulk properties. There is thus a large interest in understanding and controlling the influence of different parameters, such as epitaxy, substrate-induced strain and grain boundary effects, for the use of manganites in applied miniaturized functional devices for resistive switching (RS) memories, spintronic sensors, micro solar cells and micro solid oxide fuel cells. In this study we have selected LaMnO3±δ (LMO) due to its large oxygen reduction catalytic activity as a suitable material for applications such as solid oxide fuel cells cathode or catalyst for oxidation reactions. With these applications in mind, epitaxial LMO films were grown by Pulsed-Injection Metalorganic Chemical Vapor Deposition on two different substrates (SrTiO3 and LaAlO3) with different degree of strain, thickness and morphology. Their oxygen exchange and diffusion properties were measured at the temperature range of interest (500°C- 600°C) by the Isotope Exchange Depth Profile methodology combined with Time-of-Flight Secondary Ion Mass Spectrometry and the influence of strain and vertical dislocations on the oxygen ion transport across the films has been evaluated. Here we will show how the incorporation of oxygen into the LMO film and the ion transport down to the bottom interface can be maximized by a combination of strain engineering and film nanoarchitecturing.
Authors : Carlos Moncasi (1), Odette Chaix-Pluchery (1), Hervé Roussel (1), Laetitia Rapenne (1), Vicente Torres-Costa (2), Carmen Jiménez (1), Mónica Burriel (1)
Affiliations : (1) Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France (2) Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, 28049 Madrid, Spain
Resume : Manganite thin films exhibit interesting properties for applications such as resistive switching (RS) memories or cathodes for Solid Oxide Fuel Cells. In thin films, the functional properties depend on the microstructure and composition. In particular, for valence change memories the resistance change relies on the oxygen vacancies drift, so the RS phenomena are expected to be tunable by varying the film nanostructure. With the two above-mentioned applications in mind strontium substituted LaMnO3 (La1-xSrxMnO3, LSM) was selected to study the structure-properties relation and their impact on the oxygen exchange kinetics and RS response. LSM thin films were grown by Pulsed Injection Metal-Organic CVD optimizing the deposition conditions to obtain dense films with different Sr substitution, i.e. x=0.20 and 0.50. LSM films were grown polycrystalline (on a Si3N4 substrate) and epitaxial (on LaAlO3 single crystals) and their electrical conductivity was studied as a function of film microstructure and Sr content. To understand the oxygen content structural changes and oxygen exchange in-situ Raman characterization was combined with simultaneous conductivity measurements at different temperatures and oxygen partial pressures. These experiments will set the grounds to understand the role of composition (strontium and oxygen content) and microstructure (role of the grain boundaries) in the oxygen exchange kinetics and resistive switching properties.
Authors : Angelica Baldini, Alessandro Senocrate, Umberto Anselmi-Tamburini
Affiliations : Dipartimento di Chimica, Università degli studi di Pavia, Italy
Resume : Bulk nanostructured simple oxides, such as TiO2, ZrO2 and CeO2, obtained through fast sintering approaches, have been shown to present a significant proton conductivity in presence of humidity. This conductivity is associated to a conduction process confined to surface of residual nanoporosity present in these materials. These ceramic materials might represent an interesting alternative to polymeric protonic conductors for low temperature applications, due to their low-toxicity, high chemical stability, high melting point and low cost. Optimization of the nanostructure and of the surface chemistry is required in order to enhance their conductivity. Doping with sulfur resulted to be particularly effective, but not on all the oxides. In this work the protonic conductivity of three undoped and sulfur-doped oxides was investigated. Nanopowders of the oxides, presenting a grain size around 10-20 nm were obtained. The nanopowders were densified by HP-FAST under 500-700 °C and a pressure of 400-600 MPa for 5 minutes. The conductivity measurements were performed at 80°C at different values of relative humidity. In all cases the conductivity is enhanced by the increase sulfur content. In the case of CeO2 the increase is very limited. On the contrary S-doped ZrO2 and S-doped TiO2 show a substantial enhancement in the protonic conductivity. Samples of TiO2 with the higher content of sulfur reach conductivity values of 0.1 S·cm-1, close to the ones reported for perfluorinated polymer-based protonic exchange membranes.
Authors : Tom Underwood, Adam Symington, Alex Bonkowski, Steve Parker
Affiliations : Department of Chemistry, University of Bath, Bath, UK
Resume : Many state-of-the-art energy materials can be regarded as solid oxides with a certain amount of dopant atoms which act to enhance their properties. It is well known that the dopant species can exhibit segregation at interfaces in the material (e.g. surfaces, grain boundaries), and that this can have a significant effect on key properties of the material such as its conductivity. However, a detailed understanding of this phenomenon is lacking. There is considerable interest in being able to determine: 1) for a given dopant element and concentration, to what extent segregation will occur at different types of interface in the material; 2) what effect the segregation will have on key properties of the material. Computer simulation is in principle able to answer these questions. However, due to the large activation energies associated with dopant diffusion, often equilibrium cannot be reached in reasonable timescales using standard simulation methods. We have explored alternative simulation methods for studying segregation. We have found that Monte-Carlo-based methods allow the equilibrium segregation profiles at grain boundaries and surfaces to be determined efficiently, even when used in conjunction with realistic models of the materials. Our simulations have provided fundamental insights into segregation in a variety of interfaces and materials, including surfaces and grain boundaries in gadolinium-doped ceria and strontium titanate. We present our key findings here.
Authors : Vincent Thoréton(1), Reidar Haugsrud(1)
Affiliations : (1) Centre for Materials Science and Nanotechnology (SMN), University of Oslo, Gaustadalléen 21, NO-0349, Norway.
Resume : In the field of Solid-State Ionics, it is often necessary to determine the absolute oxygen stoichiometry of materials. It is commonly measured in a given temperature range and at a given oxygen partial pressure by coupling iodometric titration to thermogravimetric measurement. Iodometry titration provides the absolute oxygen stoichiometry at room temperature and thermogravimetric measurement provides the relative change of oxygen stoichiometry. It is possible as well to determine an absolute oxygen stoichiometry at high temperature by reducing the material to a definite mixture of components, commonly metal oxides (rock-salt structure) or metal. In certain conditions, these approaches may fail to provide valid results. We report here an alternative approach by isotopic titration. The method consists in equilibrating a sample with a definite amount of labelled diatomic oxygen. The isotopic fraction of labelled oxygen is measured in the gas phase before and after annealing the system at high temperature until complete homogenisation of the isotope fraction in the sample and in the atmosphere is achieved. Benefits and limitations of the approach are discussed.
Authors : A. Baldini, L.R. Magnaghi, A. Gastaldi., R. Biesuz, U. Anselmi-Tamburini
Affiliations : Dipartimento di Chimica, Università di Pavia, Italy
Resume : High entropy oxides (HEO) represent a new class of materials where a large number of cations are randomly and homogeneously distributed on few crystallographic sites, producing a significant entropic contribution and a reversible solid-state transformation between multiphase and single-phase states. In this study we investigated the compositional stability range of the high entropy oxide (CoxCuyMgzNiwZnk)O with (x+y+z+w+k=1), presenting a rock-salt structure, using the experimental design of mixtures. The first objective was to investigate the field of existence of the single-phase HEO and then determine how the electrical properties are affected by the composition. Since the number of possible compositions is high also for mixture design we decided to simplify the system grouping together the component oxides which present similar solid structure. The choice of the compositions to investigate, the so call candidate points, was done through the D-optimal design. The oxides were synthesized by solid-state reaction from the component simple oxides (CoO, CuO, MgO, NiO and ZnO) using an HP-FAST apparatus. The electrical properties were characterized by EIS until 500°C. It has been evidenced that this HEO phase presents a fairly wide compositional range. Within this range the electrical properties present significant modifications. The influence of compositional parameters on the overall electrical properties has been identified by principal component analysis (PCA) investigation.
Authors : Vidyanand Vijayakumar, Sreekumar Kurungot, Jijeesh Ravi Nair, Martin Winter
Affiliations : 1) Vidyanand Vijayakumar Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune-411008, Maharashtra 2) Sreekumar Kurungot Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune-411008, Maharashtra 3) Jijeesh Ravi Nair Helmholtz Institute Münster, IEK-12, Forschungszentrum Jülich GmbH, Corrensstraße 46, 48149 Münster, Germany. 4) Martin Winter Helmholtz Institute Münster, IEK-12, Forschungszentrum Jülich GmbH, Corrensstraße 46, 48149 Münster, Germany
Resume : Free-radical copolymerization of a reactive solution consisting of a difunctional poly(ethylene glycol) diallyl ether oligomer (PEGDAE), a monofunctional reactive diluent 4-vinyl-1,3-dioxolan-2-one (VEC), and a stock solution containing lithium salt (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI) in a carbonate-free non-volatile plasticizer, poly(ethylene glycol) dimethyl ether (PEGDME) is achieved by means of ultraviolet (UV)-light irradiation. Hence obtained cross-linked polymer electrolytes (XPEs) possessed a unique structure with cycling carbonate moieties attached to linear polyethylene chains which are cross-linked by ethylene oxide (EO) units. By changing [O]/[Li+] ratio from 24 to 3, a series of XPEs were prepared and physicochemical properties are characterized by thermogravimetric analysis–mass spectrometry, differential scanning calorimetry, NMR, etc., and electrochemical techniques. Quantum chemical calculations provided insights into the coordination of Li+-ions and EO units. The XPEs exhibited RT ionic conductivity in the order of 10-4 and 10-5 S/cm. The addition of lithium bis(fluorosulfonyl)imide (LiFSI) salt along with LiTFSI resulted in dual-salt XPEs exhibiting improved physical and electrochemical properties. All the single- and dual-salt XPEs exhibited electrochemical stability between 4.2 and 5V vs. Li|Li+ facilitating them to be employed against high-voltage cathodes in lithium metal batteries (LMBs). Remarkably, NCA-based lithium metal cells displayed excellent cycling stability (capacity retention >50%) even after 1000 cycles when operated at 20oC.
Authors : Yu. Zhou(a)*, Masahiro Shiraiwa(b), Stephen J. Skinner(a), Masanori Nagao(c), Kotaro Fujii(b), Isao Tanaka(c), Kenichi Kawamura(d), Masatomo Yashima(b), Laura Baque(e), Juan F. Basbus(e) and Liliana Mogni(e)
Affiliations : (a)Imperial College London, Department of Materials, SW7 2AZ, London, UK (b)Tokyo Institute of Technology, Department of Chemistry, 2-12-1-W4-17, O-okayama, Meguro-ku, Tokyo 152-8551, Japan (c)Yamanashi University, Center for Crystal Science and Technology, 7-32 Miyamae, Kofu, Yamanashi 400-8511, Japan (d)Tokyo Institute of Technology, Department of Materials Science and Engineering, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8552, Japan (e)Centro Atomico Bariloche (CAB), Department of Materials Characterization, Av. Exequiel Bustillo 9500 8402 Bariloche Rio Negro, Argentina
Resume : In the novel layered perovskite-related material, BaNdInO4, the solubility of calcium ions on the Nd3+ site and the electrochemical properties of these doped material were investigated. All BaNd1-xCaxInO4-x/2 (x=0.0, 0.05, 0.10, 0.15, 0.20, 0.25) samples were synthesized through a solid-state reaction method. The structure analysis of those materials confirmed a monoclinic crystal structure with P21/c symmetry as reported in the previous literature. A shrinkage in the unit cell volume and the lattice parameters was observed as the calcium content in the system increased. According to the electrochemical impedance spectroscopy(EIS), an increase in total conductivity of 1-2 orders of magnitude was achieved in the 10 mol% and 20 mol% calcium doped samples compared with the parent material. Among all calcium doped samples, BaNd0.8Ca0.2InO3.90 yielded the highest total conductivity σ(total) of 1.143×10-3 S˖cm-1 under lab air at 973K which was 20 times higher than that of parent material, BaNdInO4 (σ(total)=5.07×10-5 S˖cm-1 at 973K). These results agree with the previous reference. The potential of these materials being used as protonic conductors was also investigated by measuring the electrochemical properties of these materials under wet conditions using the EIS technique. An increase in total conductivity was observed in both 10 mol% and 20 mol% calcium doped samples, which implied the presence of proton conductivity in these materials. The 20% calcium doped sample exhibits a total conductivity of 2.45×10-4 S˖cm-1 at 500℃, which is higher than most of the state-of-the-art proton conducting electrolytes except for the BaZrO3 or BaCeO3 based perovskite conductors. Besides, a unique controlled-atmosphere system was used to measure the resistivity of these Calcium doped samples under different atmosphere. Clear evidence of these materials being a protonic conductor was observed, such as mass increase and resistivity decrease as the atmosphere changed from dry to humid air. The transport of oxygen ions within both the parent material and the calcium doped sample was investigated by the isotope exchange depth profiling (IEDP) technique. The kinetic parameters gained by these measurements were then compared with the ionic conductivity of these materials obtained in the EIS experiments under controlled atmosphere.
Authors : Vijay Khopkar, Balaram Sahoo
Affiliations : Vijay Khopkar, Balaram Sahoo
Resume : Lead-based perovskite structure materials with high dielectric constant value have wide applications in electronic devices, but due to the toxic nature of lead, a search of lead-free materials begins. Barium iron niobate (BaFe0.5Nb0.5O3, BFN), lead-free double perovskite structured ferroelectric material, shows high dielectric constant value. Here we studied the dielectric properties (impedance and modulus) of polycrystalline BFN sample between 20 to 300 K temperatures. The high value of the dielectric constant is due to the Maxwell –Wagner (space charge) type polarization at the grain boundary region. The origin of the dipolar polarization is due to the displacement of the cation (Fe3+ and Nb5+) with respect to the oxygen octahedra. It follows the non Debye type relaxation with relaxation straight of 3560. Activation energy calculated from the dielectric and modulus formalism is 17.26 meV and 2.74 meV corresponds to the motion of Fe3+ and Nb5+ ions in the oxygen octahedra. Temperature dependent impedance study shows the BFN is a potential candidate for direct application as low-temperature NTC thermistors.
Authors : Jonas Deuermeier, Maria Pereira, Ricardo Nogueira, Gonçalo Narciso, Rodrigo Martins, Elvira Fortunato, Asal Kiazadeh
Affiliations : i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa and CEMOP/UNINOVA, Campus de Caparica, 2829-516 Caparica, Portugal
Resume : Amorphous oxide semiconductors (AOS) are industrially applied in pixel driver thin film transistors of flat panel displays. The realization of AOS based memdiodes allows straight-forward integration towards hardware artificial intelligence systems on panel. Here, a comparative study of charge transport in various AOS based memdiodes with different Schottky contacts is presented. The studied resistive switching layers are either based on indium-gallium-zinc-oxide (IGZO) or indium-free zinc-tin-oxide (ZTO). Besides platinum and gold, a novel non-noble Schottky contact is reported, based on an intentionally oxidized molybdenum bottom contact interface. All memdiodes have area-dependent characteristics and the rectification is preserved during switching events. Resistance state dependent changes to the barrier height and other parameters characterizing the diode forward current are presented, as well as evidence for ion migration during electroforming. Reference: 1: N. Casa Branca, J. Deuermeier, J. Martins, E. Carlos, M. Pereira, R. Martins, E. Fortunato, A. Kiazadeh, Advanced Electronic Materials 2019, DOI: 10.1002/aelm.201900958
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Solid State Energy Devices (VII): Batteries : Zongping Shao
Authors : A. Gayon Lombardo, S. J. Cooper*
Affiliations : Imperial College London, UK
Resume : Nano-scale 3D imaging techniques have enabled the multiphase microstructures of fuel cell and battery electrodes to be captured in detail. However, the resulting voxelised datasets are often very large and difficult to manipulate. This geometrical data is typically used to calculate a few key homogenised metrics (such as volume fractions, surface areas and tortuosity factors), which can then be inserted into low dimensional models. However, previous work by the authors have shown that microstructures with identical homogenised parameters, may still lead to a variety of electrochemical responses [REF]. Furthermore, improving electrode performance may depend strongly on the arrangement of the phases, which may not be captured by the standard microstructural metrics. Multiphysics modelling at the nano-scale can offer some insight into which configurations are optimal based on simulations performed within synthetic microstructural data. However, for this to be a useful tool, it is necessary to constrain the search space to include only those electrodes that are manufacturable. A variety of techniques have been employed over the years attempting to generate relevant structures, but often they bear little resemblance to real data. Deep convolutional generative adversarial networks (DC-GANs) are a powerful new approach to encoding imaging data. By training a DC-GAN on real image data from a variety of processing routes, it enables the user to then generate microstructures that have targeted properties intermediate to those in the training set, but still closely resembling real electrodes. This talk will introduce the approach and explore some of the more exciting implications for electrode characterisation and design.
Authors : Can P. Koçer, Kent J. Griffith, Clare P. Grey, Andrew J. Morris
Affiliations : Department of Physics, University of Cambridge; Department of Materials Science and Engineering, Northwestern University; Department of Chemistry, University of Cambridge; School of Metallurgy and Materials, University of Birmingham
Resume : Niobium, titanium-niobium, and niobium-tungsten oxides with crystallographic shear structures have shown excellent high-rate performance as electrodes for lithium-ion batteries . The electronic structure, lithium insertion mechanism, and lithium dynamics of these compounds is largely unexplored due to their novelty and complexity. In this contribution, I will present recent first-principles density-functional theory (DFT) calculations by our group on the lithium intercalation and lithium diffusion mechanisms of crystallographic shear phases in the Wadsley-Roth family, specifically mixed-metal niobium-tungsten oxides. Our work has explored the electronic structure [2,3] with implications for electronic transport within lithiated shear structures and provided a unified mechanistic picture for the local and long-range structural changes in the family of crystallographic shear phases , focussing on the link between local distortion relaxation and buffered volume expansion. Simulations of lithium diffusion using transition state search techniques and ab initio molecular dynamics show effectively one dimensional diffusion with a clear hierarchy of activation barriers. Structure-property relationships that follow from these simulations will be discussed.  K. J. Griffith et al., Nature 559, 556-563 (2018)  Can P. Koçer, Kent J. Griffith, Clare P. Grey, Andrew J. Morris, Phys. Rev. B, 99, 075151 (2019)  Can P. Koçer, Kent J. Griffith, Clare P. Grey, Andrew J. Morris, J. Am. Chem. Soc, 141, 15121-34 (2019)
Authors : Lisette Haarmann, Karsten Albe
Affiliations : Technische Universität Darmstadt Otto-Berndt-Str. 3 64287 Darmstadt
Resume : In order to achieve maximal energy densities in all solid state Li ion batteries (ASSB), the introduction of a metallic Li anode is crucial. However, the interface kinetics between Li metal and the solid electrolytes is mostly unexplored and an atomistic picture is still missing. Therefore ab-initio calculations based on density functional theory (DFT) are carried out in order to investigate the lithium transfer over this interface. Aluminium doped Li7La3Zr2O12 (LLZO) is considered as a model system due to its stability against lithium metal and its minimal intrinsic interface resistance. Jump processes of lithium between the metal (atomic state) and the electrolyte (ionic state) and the accompanying charge transfers are investigated both with Nudged Elastic Band (NEB) calculations and ab-initio Molecular Dynamics (AIMD) simulations. While the former provides activation energies for the jump processes, the latter allows the investigation of structural rearrangements at the interface above 0 K, as well as the calculation of lithium diffusion coefficients and preferred transport directions. Combining the information of both approaches and taking into account the stability window of LLZO in contact with lithium metal, the energy landscape of the LLZO / Li metal interface is constructed.
Authors : Rowena Brugge, Federico Pesci, Andrea Cavallaro, Ainara Aguadero
Affiliations : Imperial College London
Resume : Garnet-type electrolytes have received great attention in the development of the next generation of solid state batteries based on Li-metal anodes because of their Li conductivity (greater than 1 mS/cm at room temperature) and stability against Li metal. However, their applicability has been hindered due to major issues related to stability and degradation phenomena that need understanding and addressing. The wide-ranging literature and lack of consensus with respect to the performance of garnets, in particular the Li conductivity, interfacial resistance with Li metal and critical current density for dendrite formation can be correlated to a lack of consistency in controlling the processing conditions for the material. This has a knock-on effect on the microstructure, local chemical composition of bulk, surfaces and grain boundaries and can also induce degradation phenomena such as segregation of secondary phases and moisture reactivity. All these parameters have a direct impact on the Li-ion dynamics in these systems, leading to significant implications on the cell performance in terms of power density and cycle life. In this work, we use a combination of Li-6 isotopic labelling, surface analysis techniques and electrochemistry to understand factors limiting the performance of garnet electrolytes when using Li metal as an anode. The effect of local chemical inhomogeneities will be explored and an introduction to the use of isotopic labelling for analysing Li-ion mobilities within grain, grain boundaries and interfaces will be given.
Authors : Maria Gombotz, Caroline Hiebl, Steffen Ganschow, Martin Meven, Günther Redhammer, Daniel Rettenwander, H. Martin R. Wilkening
Affiliations : Graz University of Technology, Institute for Chemistry and Technology of Materials, Austria; Graz University of Technology, Institute for Chemistry and Technology of Materials, Austria; Leibniz Institute for Crystal Growth (IKZ), Berlin, Germany; Institute of Crystallography, RWTH Aachen University, and Juelich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany; Department Chemistry and Physics of Materials, Division Materials Science and Mineralogy, University of Salzburg, Salzburg, Austria; Graz University of Technology, Institute for Chemistry and Technology of Materials, Austria; Graz University of Technology, Institute for Chemistry and Technology of Materials, Austria and ALISTORE - European Research Institute, CNRS FR3104, Hub de l’Energie, Rue Baudelocque, Amiens, France.
Resume : The degradation of LLZO-type garnets and, as a consequence thereof, the formation of resistive layers, such as Li2CO3, limits the application of garnets as solid-state electrolytes. Although, some studies on the underlying H+/Li+ exchange already exist, a complete fundamental understanding is still missing. This lack of knowledge mainly originates from the usage of polycrystalline materials having different grain sizes and, therefore, a varying bulk-to-surface ratio. Here, we used Li6La3ZrTaO12 single crystals to investigate their degradation behaviour in humid atmosphere. Ion exchange was carried out in distilled H2O for various time spans ranging from 1 to 31 days. The amount of Li+ exchange and the site preferences of the two cations, Li+ and H+, was studied via single-crystal neutron diffraction. Additionally, we investigated the influence on overall (ionic) conductivity by broadband impedance spectroscopy. Via 7Li and 1H Nuclear Magnetic Resonance (NMR) spectroscopy we separated the contribution of both ions to the overall conductivity and, furthermore, shed light on the diffusion pathway of H+ through the crystal.
Defects & Transport Phenomena (II) : Felix Gunkel
Authors : George F. Harrington
Affiliations : Kyushu University; Massachusetts Institute of Technology
Resume : Perturbing the crystal lattice away from the equilibrium structure via an applied lattice strain has been investigated from some time as a method to realise considerable improvements in oxygen-ion conductivity. Interest in this approach has, however, waned over recent years for two primary reasons: (i) a lack of consistency and reproducibility in the reported experimental findings and (ii) typically only modest changes in ionic transport are observed. In this presentation, we will address both reasons and make the case for lattice strain still being a promising route to enhanced oxygen transport. By using an unconventional method of thermally annealing out strain which occurs during deposition of epitaxial rare earth-substituted films grown by PLD, we were able to tailor the strain with no influence from grain boundaries or interfaces. Through careful analysis of the literature, we managed, for the first time, to develop a quantitative consensus on the variation of the transport properties of ceria as a function of lattice strain. We also experimentally demonstrate the effects of migration direction with respect to the biaxially strained plane. Surprisingly, we find that the change in activation energy with strain is dependent on the size of the dopant cation. Combined with computational calculations of the same system, we show that the strain-modified conductivity is dependent both on the migration edge barrier and the defect-association. These findings give unique insights into the atomistic interaction of strain on the ionic transport of oxygen in substituted CeO2, and suggest that substantially improved conductivity in strained oxides may yet still be achieved if migration direction and defect association are optimised.
Authors : Andreas Nenning, Matthias Gerstl, Jürgen Fleig, Alexander Opitz
Affiliations : TU Wien, Institute of Chemical Technologies and Analytics
Resume : In comparison to bulk Gd-doped ceria (GDC), little is known about the electrical grain boundary properties in thin films. This lack of knowledge arises from the small cross-sectional area of thin films, which makes separation of impedance features rather challenging. Here, we use embedded interdigitating Pt electrodes with spacing of few micrometers to separate grain and grain boundary conductivity of GDC thin films and characterise the effect doping and atmosphere. Since the used embedded Pt thin film electrodes are blocking for oxygen ions and reversible for electrons, they allow determination of partial electronic and ionic conductivities, with interesting results: Although the bulk vacancy concentration remains dominated by the extrinsic acceptor doping, the ionic conductivity of the films increases by up to one order of magnitude when going from oxidising to reducing atmosphere. By comparing conductivities of GDC thin films with 5 and 10 mol % Gd content, we find that the much lower ion conductivity of 5 % doped GDC is almost exclusively caused by a significantly higher grain boundary resistance. This finding is in line with the widely accepted grain boundary space charge model. The results are of high relevance for optimising the properties of GDC in anodes and electrolytes for solid oxide fuel cells, as well as for understanding electrostrictive and memristive devices, for which oxygen partial pressure dependent ionic conductivity is an important new aspect.
Authors : A. R. Genreith-Schriever and Roger A. De Souza
Affiliations : Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany JARA-FIT, 52056 Aachen, Germany
Resume : Grain boundaries are routinely advocated as a means of accelerating ion transport in energy conversion and storage materials. The effects of grain boundaries on transport rates, however, give rise to controversial discussions, as many studies report decreasing transport rates with increasing grain boundary ratios. Efforts to understand the cause of this are largely directed at analysing the redistribution of point defects at grain boundaries and the resulting space-charge potentials. Another possible reason for slower transport lies in the structural modifications of the grain boundary compared to the bulk material. The changed ion configurations are expected to alter the activation barriers of migration which can cause an intrinsic structural resistance of the grain boundary, the excess grain-boundary resistance. To date no method has been reported to selectively probe excess grain-boundary resistivities isolated from the influence of space charge effects. Here, excess resistivities of symmetric tilt grain boundaries are determined for the model oxide material ceria (CeO2) with classical Molecular Dynamics simulations, offering a novel method to selectively quantify the excess grain-boundary resistivities of high-performance energy materials.
Authors : Grieshammer, S.*(1,2), Murch, G.(3).
Affiliations : (1) Helmholtz-Institut Münster, Forschungszentrum Jülich GmbH, Germany (2) Institute of Physical Chemistry, RWTH Aachen University, Germany (3) School of Engineering, University of Newcastle, Australia
Resume : Cerium oxide is a versatilely applicable ceramic, e.g. as high temperature coating material. Doped with trivalent oxides, such as gadolinium oxide, the material shows high oxygen ion conductivity exceeding that of commonly applied yttria-stabilized zirconia. In this study, we estimate thermal conductivity of pure and doped cerium oxide by equilibrium molecular dynamics simulations based on widely applied empirical pair potentials and making use of the Green–Kubo formalism. The simulations show the limitations of most of the present potentials to correctly describe the thermal expansion and thermal conductivity. Based on our results we apply the Green–Kubo formalism for Gd-doped ceria to obtain thermal and ionic conductivity. The simulations do not only yield the diagonal Onsager phenomenological coefficients but also the off-diagonal coefficients. In this way it is possible to describe the coupling between mass and heat transport, which also known as thermodiffusion or the Soret-effect.
Authors : Sebastian Steiner, Leonie Koch, An-Phuc Hoang, Max Gehringer, Karsten Albe, Till Frömling
Affiliations : Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Strasse 2, Darmstadt, Germany, 64287
Resume : Sodium bismuth titanate (NBT) based ceramics are excellent lead-free ferroelectrics and relaxor materials. The defect chemistry of these materials is, however, very complex. NBT can actually be modified from highly ionically conductive to highly resistive. For example, acceptor doping does not lead to the hardening of ferroelectric properties as it was initially expected. Instead, mobile oxygen vacancies are induced making the material an excellent oxygen ion conductor . This behavior is very interesting from a research perspective but it may be very detrimental for the transfer of NBT-ferroelectrics into application. Aging and fatigue models from other well-known ferroelectrics might not be applicable. Thus, a detailed understanding of the defect chemistry of NBT and its solid solutions is of high importance. We developed a model to elucidate the defect chemistry of NBT-ceramics . Furthermore, methods to control the ionic conductivity, ferroelectric properties and the microstructure will be discussed in this work . This will illustrate the extraordinary opportunities to alter properties of NBT-based material for multiple applications. 1. Li, M., et al., A family of oxide ion conductors based on the ferroelectric perovskite NBT. Nature Materials, 2014. 13(1): p. 31-35. 2. Koch, L., et al., Ionic conductivity of acceptor doped sodium bismuth titanate: influence of dopants, phase transitions and defect associates. Journal of Materials Chemistry C, 2017. 5(35): p. 8958-8965. 3. Steiner, S., et al., The effect of Fe-acceptor doping on the electrical properties of NBT and 0.94 NBT–0.06 BT. Journal of the American Ceramic Society, 2019. 102(9): p. 5295-5304.
|12:00||Poster Prizes and Closing|
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