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Materials for energy

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Materials for chemical and electrochemical energy storage

Materials for chemical and electrochemical energy storage are the key for a diverse range of applications including batteries, hydrogen storage, sunlight conversion into fuels and thermal energy storage. The goal is to provide efficient solutions for a future energy scenario based on renewable energy sources.

Scope:

The urgent need for energy storage materials for a sustainable and carbon-free society is the main stimulant for the new dawn in the development of functional material for energy storage and conversion. For example hydride based all-solid-state batteries or batteries based on alternative cations including Na+ and Mg2+, which are considered as safer, cheaper, and more abundant, while potentially higher energy density compared to Li-ion batteries are achievable. New reactive hydride composite systems (RHCs) for hydrogen storage application with operating conditions near room temperature are nowadays at the reach of a hand. New solutions to address the issue of intermittent supply from renewable energy sources through the synthesis of energy carriers such as H2, CH4, CH3OH etc. (e.g. through sunlight-driven processes) to provide an uninterrupted sustainable supply of energy for stationary systems and zero-emission vehicles are being developed. The proposed symposium will be chemistry neutral; it will not be limited to a certain class of materials. Materials covered in this symposium comprise  (i) active materials for energy storage that require a certain structural and chemical flexibility, for instance as intercalation compounds for hydrogen storage or as cathode materials (ii) novel catalysts that combine high (electro-)chemical stability and selectivity, and (iii) solid state ionic conductors for batteries and fuel cells. Renewable energies combined with efficient storage systems will be the key enabler of the development of the human society in the incoming decades. The proposed symposium is therefore interdisciplinary and aspires to bring together ambitious young and established scientists from around the world to not only present the latest advances of the intense worldwide research but also exchange ideas as well as identify major challenges and hot-topics for future developments towards efficient solutions. 

Hot topics to be covered by the symposium:

  • Hydrogen storage material development
  • Fundamental hydride structures, reaction mechanisms and thermodynamics
  • Conduction mechanism of solid-state ion conductors
  • Stable interfaces and structural transitions in solid-state batteries
  • Materials for solar thermal energy storage
  • Materials for sunlight conversion into chemical fuels
  • Development of material and systems for thermal energy storage
  • Computational methods for energy materials
  • Towards application: engineering challenges
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08:50 Welcome message and introduction to the Symposium    
 
Session 1: Challenges in Modern Li-Batteries : Claire Villevieille
09:00
Authors : Maximilian Fichtner(1,2), Zhenyou Li(1), Ebrahim Aouzari-Lotf(1), Zhirong Zhao-Karger(1,2)
Affiliations : 1: Helmholtz Institute Ulm (HIU); 2: Karlsruhe Institute of Technology, Institute of Nanotechnology

Resume : The talk will address the actual situation in battery development and current strategies to move forward in the field. Currently, progress is made by joint contributions from both battery chemistry and battery design and engineering. While new battery designs have reduced the amount of packaging material considerably and allow now the integration of 20-50% more active material in the battery pack, new opportunities have emerged for the integration of new - and "old" materials. Hence, a "materials dawn" can be noticed in the battery world, away from systems containing critical raw materials, and towards materials with sustainable composition, low cost, and longer lifetime.

D.1.1
09:45
Authors : Mariarosaria Tuccillo (1), Laura Silvestri (2), Sergio Brutti (3)
Affiliations : (1)Dept. Chemical Engineering Materials Environment, University of Rome La Sapienza (2) ENEA Research Center (Casaccia) (3) Dept. Chemistry, University of Rome La Sapienza

Resume : Li-rich layered oxides (LRLO) materials are a family of promising positive electrode materials with large specific capacity and high working potential. The eco-friendly Co-free LRLOs have attracted a lot of attentions, thanks to the improved sustainability, reduced costs and outstanding performance (250 mAh g-1). (1,2) The crystal structure and cation ordering of LRLO are a matter of controversy; the structure is identified as solid solution, with an R3 ̅m crystal structure (3) with partial supercell ordering of lithium ions, or as a nano-mosaic constituted of coexisting solid-solution phases with R3 ̅m and C2/m structures (4). Extensive defectivities play a key role in the breakdown of the cation ordering in the C2/m lattice that degrades in the R3 ̅m one. This ambiguity/instability is at the origin of the severe capacity and voltage fading in batteries originating from undesired lattice transformations. To evaluate structural evolutions during de-/lithiation, here we present a description of operando XRD analysis of Co-free LRLOs, during the activation and first cycle process. The experiment was conducted at the ELETTRA synchrotron at beamline MCX Proposal number: 20205276. 1)M. W., N. G., J. L., Energies, 12, (2019), 504. 2)J. A., L. S., G. C., M. L., H. L., S. Y., S. C., D. Z., J. Mater. Chem. A, 5, (2017), 19738. 3)Z. L., Z. C., J. R. D., Chem. Mater.,15, (2003), 3214. 4)K. A. J., Z. Q. D., L. F. A., A. M., P. J. F., Chem. Mater., 23, (2011), 3614.

D.1.2
10:00
Authors : Fabien Eveillard, Fabrice Leroux, Nicolas Batisse, Diane Delbègue, Katia Guérin
Affiliations : Institut de Chimie Clermont Ferrand, Centre National des Etudes Spatiales ; Institut de Chimie Clermont Ferrand ; Institut de Chimie Clermont Ferrand ; Centre National des Etudes Spatiales ; Institut de Chimie Clermont Ferrand

Resume : There is an urgent need in exploring new cathode materials for Lithium batteries in order to increase their capacities. Conversion type cathodes are relevant replacement candidates and especially metal fluorides such as FeF3 with a theoretical capacity of 712 mAh g-1 for three electrons at a voltage of 2.74 V vs. Li+/Li or CuF2 with a theoretical capacity of 528 mAh g-1 for two electrons at 3.55 V vs. Li+/Li. In this work, compatibility of fluorides with a PEO/LiTFSI (Poly Ethylene Oxide impregnated with Lithium bis(trifluoromethanesulfonyl)imide) solid electrolyte membrane is evaluated to avoid dissolution of active materials in organic liquid electrolytes often encountered with fluorides. Additionally, a general synthesis method is used to prepare ternary metal fluorides. Indeed, ternary metal fluorides were recently explored1–3 to enhance fluoride cathodes performances. These materials are usually prepared by planetary ball milling or by hydrofluoric acid HF-assisted fluorination, both methods not scalable for industrial purpose. In this work, we propose Multi-Metallic Template Fluorination MMTF as a general synthesis way to prepare ternary metal fluorides in a scalable way suitable for industrial applications. Prussian Blue Analogs are particularly relevant fluorination templates: these compounds can be easily prepared in great quantities by coprecipitation, enabling industrial applications. For electrochemical applications considered in this work, Copper based Prussian Blue Analog CuPBA of general formula Cu3[Fe(CN)6]2.xH2O is chosen to combine properties of copper and iron redox centers in a ternary metal fluoride cathode. By monitoring thermal transformations of CuPBA using ThermoGravimetric Analyses coupled to Mass Spectrometry (TGA MS) and XRD, different temperature domains are identified under air and fluorination temperatures are selected in consequence. Structures of fluorinated products are characterized by combined XAS and XRD analyses. The electrochemical behavior of fluorinated products were then evaluated and compared to binary fluorides and mechanical milling products. The first discharge capacity approaches the maximum theoretical capacity of 600 mAh g-1 and highlights the possibility to dramatically increase the capacity of Lithium batteries by potentially doubling the capacity reached with classical NMC electrodes. The Multi Metallic Template Fluorination MMTF approach detailed in this work can be adapted to a wide range of multi metallic templates such as Metal Organic Frameworks and Layered Double Hydroxides for the preparation of mixed metal fluorides with unique features such as particular structures and/or morphologies depending on the desired application and in a scalable way. (1) Villa et al. ACS Appl. Mater. Interfaces 2019, 11 (1), 647–654. (2) Wang et al. Nat Commun 2015, 6 (1), 6668. (3) Ding et al. ACS Appl. Mater. Interfaces 2019, 11 (4), 3852–3860.

D.1.3
10:15
Authors : Martin Aaskov Karlsen, Dorthe Bomholdt Ravnsbæk
Affiliations : University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

Resume : Material properties are inherently bound to the material structure. Therefore, thorough characterization and understanding of material structure are key for the development of the materials of tomorrow. Earlier, crystallinity was thought to be an essential prerequisite for intercalation-type electrodes for rechargeable batteries. Conveniently, crystalline materials are also well-suited for traditional powder diffraction, probing the long-range periodic order of the atomic structure. However, as high-brilliance x-ray and neutron sources have emerged, the keys to understand structural disorder have been handed and the significance of structural disorder on the nano and atomic length scales have been realized. [1] Through total scattering, including both the Bragg and diffuse scattering, the so-called reduced atomic pair distribution function, PDF, can be obtained through a Fourier transformation, which brings the total scattering data from reciprocal space and into real space. The reduced atomic PDF is an atomic pair correlation function, which can be thought of as a histogram of the interatomic distances, where the height of a correlation peak relates to the probability for the corresponding interatomic distance, but also the scattering lengths of the atoms constituting the atomic pair, among other factors. Through the PDF, the atomic structure can be studied from nearest-neighbor distances and all the way to the nanoscale. [1] The atomic structure of electrode materials for batteries can be studied under dynamic conditions through x-ray total scattering using the specially designed AMPIX electrochemical cell. [2] From the x-ray total scattering data, reduced atomic PDFs can be obtained. In this way, material structure can be studied together with structural phase transitions, including those involving disordered phases. However, the multiple component nature of batteries, the need for temporal resolution in the operando data, and the need for long exposure times to obtain high data quality forces the experimentalist to do a lot of decision making, both for the experimental design but also for the data processing and analysis. Herein, studies of reversible and irreversible order-disorder transitions are provided. The former through a study of sodium iron hydroxide phosphate hydrate [3] and the latter through a study of nanosized rutile titanium dioxide. [4] Nanocrystalline bronze titanium hydroxide provides an example of ab origine disorder. [5] These examples are provided together with a general discussion on practices, when doing operando PDF analysis for electrode materials for rechargeable batteries. [1] Egami & Billinge, Underneath the Bragg Peaks, Pergamon, Oxford, UK, 2nd ed., 2012, vol. 16. [2] Borkiewicz et al., Journal of Applied Crystallography, 2012, 45, 1261-1269. [3] Henriksen et al., Nanoscale, 2020, 12, 12824-12830. [4] Christensen et al., Nanoscale, 2019, 11, 12347-12357. [5] Billet et al., Chemistry of Materials, 2018, 30, 4298–4306.

D.1.4
10:30 Q&A    
10:45 Break    
 
Session 2: Solid-State Batteries – a game changer? : Maximilian Fichtner
11:00
Authors : Martin Drüe1, Alice Robba1, Oscar Defoor2, Patrice Perrenot3, Daniele Perego4, Cédric Pitteloud4, Claire Villevieille1
Affiliations : 1. Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, Grenoble INP, LEPMI, 38000 Grenoble, France 2. CEA, IRIG Institute, 17 rue des Martyrs, F-38000 Grenoble, France 3. CEA- LITEN, 17 rue des Martyrs, F-38000 Grenoble, France 4. Belenos Clean Power Holding Ltd, CH-4452 Itigen, Switzerland

Resume : All-solid-state batteries have been presented as the ideal solution to address i) the safety limitations of conventional Li-ion batteries by suppressing the flammable organic electrolytes and ii) the problem of insufficient energy densities. To date, two types of solid Li-ion electrolytes have been mainly studied, namely, sulfur-based and ceramic-based materials. As they are easy to process and they offer a high lithium ion conductivity in the range of 1-12 mS/cm [1,2], sulfide-based electrolytes such as e.g. thio-LISICONs and argyrodites are therefore regarded as suitable candidates to be used in lithium all-solid-state batteries. Despite the progress in the development of superionic conductor, many aspects regarding their chemical and mechanical issues remain unsolved especially during electrochemical activities where the electrolyte is heavily decomposed [3]. If the electrode engineering i.e. composite electrode (mixture of electroactive material, conductive agent and solid electrolyte) is under intense investigation, the role of the solid electrolyte pellet (i.e. separator) is so far poorly studied. As an example, if the sintering (even cold sintering) is not properly performed, the Li-ion conduction will not be optimal that could create kinetics problem. As well as if voids appear in the solid electrolyte pellet, it will lower the ionic conductivity and the voids could then evolve and propagate into cracks during electrochemical cycling leading to dendrites formation and eventually cell failure. In this work, we are proposing an in depth (operando and postmortem) multiscale investigation of the parameter controlling the ?shaping? of commercial based solid electrolytes and its consequence on the electrochemical activity. We gathered information from bulk to surface analysis using electrochemical (EIS, CV, etc.) X-rays (XRD, XAS, micro and nano-XRT, FIB-SEM, etc.) and neutron-based techniques (NPD, etc.) revealing the relationship between shaping and electrochemical performance. The results obtained here should serve as a preliminary basis to develop better solid-state batteries using sulfide-based electrolyte. References: [1] Q. Zhang, D. Cao, Y. Ma, A. Natan, P. Aurora, H. Zhu, Sulfide-Based Solid-State Electrolytes: Synthesis, Stability, and Potential for All-Solid-State Batteries, Adv. Mater. 31 (2019) 1?42. https://doi.org/10.1002/adma.201901131. [2] N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto, A. Mitsui, A lithium superionic conductor, Nat. Mater. 10 (2011) 682?686. https://doi.org/10.1038/nmat3066. [3] L.R. Mangani, C. Villevieille, Mechanical vs. chemical stability of sulfide-based solid-state-batteries. Which one is the biggest challenge to tackle? Overview of solid state batteries and hybrid solid state batteries., J. Mater. Chem. A. (2020). https://doi.org/10.1039/d0ta02984j.

D.2.1
11:30
Authors : Leire Meabe, Sergio Rodriguez Peña, Maria Martinez-Ibañez, Yan Zhang, Elias Lobato, Hegoi Manzano, Michel Armand, Javier Carrasco, Heng Zhang
Affiliations : Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein 48, 01510 Vitoria-Gasteiz, Spain (Leire Meabe, Sergio Rodriguez Peña, Maria Martinez-Ibañez, Yan Zhang, Elias Lobato, Michel Armand, Javier Carrasco, Heng Zhang) Departament of Condensed Matter Physics, University of the Basque Country (UPV/EHU), Barrio Sarriena, s/n, 48940 Leioa, Spain (Sergio Rodriguez Peña, Hegoi Manzano)

Resume : Solid polymer electrolytes (SPEs) have been playing a crucial role in the development of high-performance solid-state lithium metal battery.[1] The safety and the easy tailoring of the polymers designate these materials as promising candidates to be implemented as electrolytes. Poly(ethylene oxide) (PEO) has been consolidated in the community of SPEs as a good solvating matrix to a wide gallery of lithium salts.[2] However, its inferior electrochemical stability against high-voltage cathode active materials, strongly urges the search for alternative polymers. In recent years, several carbonyl containing polymers (i.e., polycarbonates and polyesters) have arisen as possible replacement to PEO,[3] being one of the most representative, poly(ε-caprolactone) (PCL). In this work, we have combined molecular dynamics simulations and a range of experimental measurements to gain in-depth insights on the ionic transport in polyester-based SPEs. Specifically, the physicochemical properties and morphological behavior of the blend SPEs comprising PEO and PCL including the two end-members are comprehensively investigated. The results reveal that the preferential coordination between Li+ cation and ethylene oxide units and partial phase separation between PEO and PCL control the ionic transport as well as the thermal properties of PEO and PCL blends. Moreover, the studies concluded that LiTFSI only coordinates via carbonyl group to the PCL polymer backbone, remaining as contact ion pairs, which changed the ionic conductivity mechanism inside the polymer matrix. Owing to these insights into coordination environment and phase separation, the ionic conductivity mechanism inside the PEO-PCL blends was elucidated. References 1. A. Manthiram, X. Yu and S. Wang, Nature Reviews Materials 2017, 2, 16103. 2. R. Agrawal and G. Pandey, Journal of Physics D: Applied Physics 2008, 41, 223001. 3. J. Mindemark, M. J. Lacey, T. Bowden and D. Brandell, Progress in Polymer Science 2018, 81, 114-143.

D.2.2
11:45
Authors : Swati Soman, Mohit Yadav, Ajit Kulkarni
Affiliations : Sensor Materials & Devices laboratory, Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076, India.

Resume : Fluoride phosphate based crystalline materials are reported as cathodes for Li ion battery. They offer higher operating voltage due to higher electronegativity and better kinetics due to lower affinity of Li to fluoride anion. However, their direct synthesis is difficult due to rich polymorphism exhibited by A_2MPO_4F (A = Li, Na; M = Mn, Fe, Co, Ni). Besides, being crystalline, presence of intrinsic spatial voids and channels limit their volumetric energy density. On the other hand, glasses offer advantage of open network structure without porosity, ease of synthesis over wide composition, thereby, fine tuning of properties. Mixed conducting glasses, containing alkali oxide and transition metal oxide, exhibit ionic to mixed conduction with change in composition. Ionic conducting glasses can be used as solid electrolytes, while those exhibiting mixed conduction can be used as cathodes in future version of all solid state battery. Although crystalline fluoride phosphate cathode is reported, literature on glassy cathodes is very limited. To combine the electrochemical advantage of fluoride phosphates and structural, compositional, synthesis advantages of glasses, we fabricated new vitrified compositions in narrow compositional range of LiF‒Al(PO_3)_3 system with addition of Vanadium Oxide. Homogeneous glasses are obtained by melt quenching over wide range of Vanadium oxide content, from 2 to 70 mol%. IR spectra reveal that Vanadium acts as network modifier or as second network former depending on its concentration. Changes in glass structure correlate with their measured properties. Glass transition temperature Tg varies between 250‒350⁰ C, reducing with increasing Vanadium content, due to decreasing rigidity of glass matrix as it transforms from phosphate to vanadophosphate network. Room temperature dc conductivity varies from ~10-¹⁰ S/cm to ~10-⁶ S/cm. Impedance measurements reveal ionic to mixed conduction with changing composition, rendering them as promising glassy cathode material.

D.2.3
12:00
Authors : Léa R. Mangani, James A. Isaac, Didier Devaux, Renaud Bouchet
Affiliations : Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, Grenoble INP, LEPMI, 38000 Grenoble, France

Resume : Li-ion battery holds an everlasting role in energy storage for nomad devices, electrical vehicles as well as for grid energy storage. To date, Li-ion batteries are the most advanced energy storage systems, but they are reaching their limitation in terms of energy density[1] and safety. New technologies are currently under development, and among them, all-solid-state Li-ion batteries should deliver better electrochemical performance and enhanced safety. Solid polymer electrolytes (SPEs) provides suitable mechanical properties, but suffers poor conductivity, whereas the ceramic electrolytes (CE) are providing the opposite features.[2,3] Hybrid electrolytes should achieve high conductivity coupled to high mechanical stability, and provide intimate interface with active materials. To date, this result is not yet reached due to the complexity of the Li-ion transport especially at the SPE/CE interface. Indeed, a decrease in the composite ionic conductivity[4] is generally observed and ascribed to the high Li ions charge transfer resistance at the SPE/CE interface. Yet, there are no proper charge transfer kinetic model to elucidate the parameters that could control this interfacial barrier nor a deeper understanding of this interfacial behaviour. Herein, we propose an electrochemical methodology relying on electrochemical impedance spectroscopy based on the de-coupling of the interfacial processes from the bulk ones. We probed the relationship between the interfacial resistance and some specific parameters of the system such as Li salt content, ceramic nature, polymer electrolyte bulk properties etc. using our novel methodology. The results provide valuable insight on the factors that govern SPE/CE ionic charge transfer and thus, enable the design of an optimized SPE/CE interface for all-solid-state batteries. 1. Armand, M. & Tarascon, J. M., Nature 414, 359–367 (2001). 2. 2. Zhou, D., Shanmukaraj, D., Tkacheva, A., Armand, M. & Wang, G. Chem 5, 2326–2352 (2019). 3. 3. Varzi, A., Raccichini, R. & Scrosati, J. Mater. Chem. A Mater. energy Sustain. 4, 17251–17259 (2016). 4. 4. Keller, M., Varzi, A. & Passerini, S. J. Power Sources 392, 206–225 (2018).

D.2.4
12:15
Authors : Valerio Gulino (a)(b), Matteo Brighi (c), Peter Ngene (a), Radovan Černý (c), Marcello Baricco (b), and Petra de Jongh (a)
Affiliations : (a) Materials Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, The Netherlands (b) Department of Chemistry and Inter-departmental Center Nanostructured Interfaces and Surfaces (NIS), University of Turin, Via Pietro Giuria 7, 10125 Torino, Italy (c) Laboratoire de Cristallographie, DQMP, Université de Genève, quai Ernest-Ansermet 24, CH-1211 Geneva 4, Switzerland

Resume : Solid-state electrolytes (SSEs) are promising candidates for resolving the intrinsic limitations of the organic liquid electrolyte currently employed in Li-ion batteries. Nevertheless, an SSE must fulfil several requirements to be employed in an all-solid state battery (SSB), such a high ionic conductivity. Complex hydrides (e.g. LiBH4) are suggested as solid-state electrolytes.1 Among the different polymorphs of LiBH4, only the hexagonal phase, which is stable at temperatures above 110°C, has a remarkable high ionic conductivity (~10-3 S cm-1 at 120 °C). To practically access a room temperature (RT) SSB, a promising approach to enhance the Li-ion conductivity of LiBH4 at RT is the development of new high conductive interface by mixing it with oxide nanoparticles (such as SiO2, Al2O3 and MgO).2 In this work the Li-ion conductivity of LiBH4 has been enhanced by means of MgO-mixing, optimizing the composition of LiBH4-based composites in order to obtain a RT operating SSE. The optimum composition of the mixture results 53 v/v % of MgO, showing a Li-ion conductivity of 2.86 10-4 S cm-1 at 20 °C, four order or magnitude higher than pure LiBH4 and comparable to the Li-ion conductivity of a liquid electrolyte. The improved Li-ion conductivity relies on the formation of a conductive interface that can be described by a core-shell model where the fraction of LiBH4 (the core) is in direct contact with the oxide (the shell). The formation of the composite does not affect the electrochemical stability window, which is similar to that of pure LiBH4 (about 2.2 V vs. Li+/Li). The mixture has been incorporated as solid-electrolyte in a TiS2/Li all-solid-state Lithium metal battery. A freshly prepared battery failed at RT only after 5 cycles. On the other hand, a stable solid electrolyte interphase can be obtained by a pre-conditioning cycling at 60 °C. Afterward, a capacity retention of about 80 % at the 30th cycle was obtained operating at RT. We illustrate that the addition of oxide nanoparticles to LiBH4 offers a promising strategy to obtain novel SSE candidates for Li-based SSB.3 (1) Matsuo, M.; Orimo, S. Lithium Fast-Ionic Conduction in Complex Hydrides: Review and Prospects. Adv. Energy Mater. 2011, 1 (2), 161–172. https://doi.org/10.1002/aenm.201000012. (2) Gulino, V.; Barberis, L.; Ngene, P.; Baricco, M.; de Jongh, P. E. Enhancing Li-Ion Conductivity in LiBH 4 -Based Solid Electrolytes by Adding Various Nanosized Oxides. ACS Appl. Energy Mater. 2020, 3 (5), 4941–4948. https://doi.org/10.1021/acsaem.9b02268. (3) Gulino, V.; Brighi, M.; Murgia, F.; Ngene, P.; de Jongh, P. E.; Černý, R.; Baricco, M. Room Temperature Solid-State Lithium-Ion Battery Using LiBH4-MgO Composite Electrolyte. ACS Appl. Energy Mater. 2021, accepted. https://doi.org/10.1021/acsaem.0c02525.

D.2.5
12:45 Q&A    
13:00 Break    
 
Session 3: Abundantly clear – the future of Na-Batteries : Valerio Gulino
14:00
Authors : Philipp Adelhelm
Affiliations : Humboldt-University Berlin Helmholtz-Zentrum Berlin(HZB) für Materialien und Energie

Resume : The rising demand of rechargeable batteries for electric vehicles and grid storage applications sparks a lot of interest on alternatives to “standard Li-ion battery technology”. The size of these markets is so large that great efforts are currently undertaken towards using more cost-effective materials that will not run into supply and/or resource constraints. Here, sodium-ion batteries are one important option that primarily aim at realizing high energy batteries based on sodium and other abundant elements such as carbon, iron or manganese. On the other hand, solid-state batteries (SSBs) are considered as promising option for electric vehicles. In these types of batteries, a solid electrolyte replaces the flammable organic liquid electrolyte, which improves safety. At the same time, SSBs might enable energy densities exceeding conventional lithium-ion technology. This talk gives an overview on materials aspects on sodium-ion and solid-state batteries and how they compare to lithium-ion batteries. Specific examples on inorganic materials will be discussed, including high capacity metal/carbon negative electrodes[1], layered oxides of the type Na[MnxFeyTMz]O2[2], solvent co-intercalation reactions (graphite)[3] and metal sulfides (CuS, Cu3PS4, NaTixTMyS2)[4] (TM = transition metal). [1] aT. Palaniselvam, C. Mukundan, I. Hasa, A. L. Santhosha, M. Goktas, H. Moon, M. Ruttert, R. Schmuch, K. Pollok, F. Langenhorst, M. Winter, S. Passerini, P. Adelhelm, Advanced Functional Materials 2020, 30; bT. Palaniselvam, M. Goktas, B. Anothumakkool, Y. N. Sun, R. Schmuch, L. Zhao, B. H. Han, M. Winter, P. Adelhelm, Advanced Functional Materials 2019, 29. [2] L. Yang, J. M. L. del Amo, Z. Shadike, S. M. Bak, F. Bonilla, M. Galceran, P. K. Nayak, J. R. Buchheim, X. Q. Yang, T. Rojo, P. Adelhelm, Advanced Functional Materials 2020, 30. [3] aI. Escher, Y. Kravets, G. A. Ferrero, M. Goktas, P. Adelhelm, Energy Technology 2021, 9; bM. Goktas, C. Bolli, E. J. Berg, P. Novák, K. Pollok, F. Langenhorst, M. V. Roeder, O. Lenchuk, D. Mollenhauer, P. Adelhelm, Advanced Energy Materials 2018, 8; cB. Jache, P. Adelhelm, Angew. Chem. Int. Ed. 2014, 53, 10169-10173. [4] aA. L. Santhosha, N. Nazer, R. Koerver, S. Randau, F. H. Richter, D. A. Weber, J. Kulisch, T. Adermann, J. Janek, P. Adelhelm, Advanced Energy Materials 2020, 10; bW. Brehm, A. L. Santhosha, Z. Zhang, C. Neumann, A. Turchanin, A. Martin, N. Pinna, M. Seyring, M. Rettenmayr, J. R. Buchheim, P. Adelhelm, Advanced Functional Materials 2020, 30; cF. Klein, B. Jache, A. Bhide, P. Adelhelm, Physical Chemistry Chemical Physics 2013, 38, 15876-15887.

D.3.1
14:30
Authors : Gustav Graeber, Daniel Landmann, Enea Svaluto-Ferro, Meike V. F. Heinz, and Corsin Battaglia
Affiliations : Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.

Resume : Economic, high-performance electrochemical energy storage is required for the transition from fossil fuels to renewable energy sources. High-temperature sodium-metal chloride batteries combine a variety of advantages, namely long cycle and calendar life, high specific energy, no self-discharge, and minimum maintenance requirements. Furthermore, they employ abundant raw materials without the need of lithium and cobalt. However, large-scale deployment is currently hindered by high production cost of the complex, commercial tubular cells and limited rate capability. Here we introduce sodium-metal chloride cells with a simple, planar architecture that provide high specific power while maintaining the inherent high specific energy. These high-performance cells deliver an average discharge power of 1022 W kg-1 and a discharge energy per cycle of 258 Wh kg-1 on cathode composite level, shown over 140 cycles at an areal capacity of 50 mAh cm-2 and a temperature of 300 °C. This corresponds to a 3.2C discharge over 80% of full charge. Compared to the best performing planar sodium-metal chloride cells with similar cycling stability and mass loading in the literature, the achieved performance represents an increase in specific power by more than a factor of four, while also raising the specific energy by 74%. The performance enhancement is enabled by a rational design of the rate-limiting cathode. Our cathode design is guided by insights that we obtained on critical ionic transport processes and the effect of the cathode composition on the cell resistance. Such drastically improved planar sodium-metal chloride batteries are attractive candidates to be used both in mobility and stationary storage applications.

D.3.2
14:45
Authors : Andreas Østergaard Drejer(a), Daniel Risskov Sørensen(b) and Dorthe Bomholdt Ravnsbæk(a)
Affiliations : (a) Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark (b) Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark

Resume : The Li-ion battery (LiB) is a well-performing energy storage technology and therefore widely used in portable electronics and electric vehicles. However, it struggles to meet the criteria of large-volume applications such as storage of renewable energy from wind turbines and solar cells.[1] Na-ion batteries (SiB) are interesting alternatives to LiBs, due the easy access, high abundance and low price of sodium. However, for the SiBs to be truly competitive, development of novel electrode materials with high capacity and good capacity retention is crucial. For this purpose, layered transition metal oxides NaxMO2 (M = transition metal) have received a lot of attention as Na-ion cathodes, since they offer high electrochemical potentials and high capacities.[2] In addition, there is a strong incentive to move towards cheaper and more environmentally friendly transition metals for these materials, such as use of iron and manganese and thereby limit the use of e.g. cobalt. Capacities as high as 193 mAh/g has been reached in Co-free materials, but problems with e.g. capacity retention are still significant.[3] The layered NaxMO2 can crystallize in several polymorphs. Especially two polymorphs are of interest: The so-called P2 and O3.[4] Both phases can undergo multiple phase transitions under extraction of sodium, some of which are irreversible. Both P2 and O3 polymorphs can be co-synthesized by varying the Na-content and thereby the benefits of both structures, such as better structural stability and high capacity, can be utilized.[5-6]. In this study a series of NaxFe1-y-zMnyNizO2 materials are investigated for their structural and electrochemical behavior in SiBs, where they deliver initial capacities of 120-160 mAh/g. Operando powder X-ray (PXRD) and neutron (PND) diffraction showed that the O3-phase transforms into trigonal layered phase, named P3, followed by a distortion into a monoclinic phase called O?3. The P2 phase follows a solid-solution behavior during Na-extraction. Furthermore, the operando measurements revealed that the P2 phase disorder either partially or completely at high voltage. The voltage at which the disorder occurs depends on the chemical composition of the materials and the P2/O3 ratio. To investigate the nature of the disordered P2-phase, X-ray total scattering with pair distribution function (PDF) analysis was used. The aim is to obtain a thorough understanding of the correlation between chemical composition, polymorphic composition, and structural charge-discharge behavior. References [1] J.-M. Tarascon, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2010. 368, 3227-3241. [2] P.-F. Wang, et al., Advanced Energy Materials 2018, 8, 1701912. [3] J. Zhao, et al., J. Power Sources 2014, 264, 235-239. [4] C. Delmas, et al., Physica B+C 1980, 99, 81-85. [5] E. Lee, et al., Advanced Energy Materials 2014, 4, 1400458. [6] S. Guo, et al., Angew. Chem. Int. Ed. 2015, 54, 5894-5899.

D.3.3
15:00
Authors : Christian Lund Jakobsen Bettina Pilgaard Andersen Dorthe Bomholdt Ravnsbæk
Affiliations : University of Southern Denmark, Department of Physics, Chemistry, and Pharmacy, Campusvej 55, 5230 Odense, Denmark

Resume : Na-ion batteries (SiB) are slowly emerging as alternative for the well-established Li-ion battery (LiB) technology, as demand for grid and self-sufficient power storage are rapidly increasing. Despite the great effort in elimination of Co from future Li-ion electrode materials like in LFP, NMC, and LMNO, some soon to come challenge still opposes the Li-ion battery industry, as half of Li deposits are located in South America and eventually demands will exceed deposit contents of Li. Here are SiBs superior as the price is much lower of sodium precursors and conductive salts as Na is much more abundant. Though one big problem still remains for SiBs as the energy density is not compatible to LiBs. Thus, a complete substitution of LiBs for SiBs is very unlikely. The most promising class of Na-ion electrode materials are the layered O3- and P2-type materials. Still a major bottleneck within development of electrode materials for SiBs is the mentioned lack in energy density or poor electrode performance in terms of irreversible phase transitions, slow kinetics or instability upon air exposure. A very interesting material is the O3-NaCrO2 as this material was shown to have great reversibility for 50 % desodiation and also exhibit excellent thermal stability. During charge the structural evolution have been well established going from an O3→O’3→P’3 within extraction of half of the Na from the pristine material. Upon deep charge disorder is induced accompanied by a huge capacity decay. Few studies have proposed that migration of Cr6+ into the Na-interslab to form a rock salt structure, is a possible explanation for the capacity decline. Although, a complete understanding of the structural evolution is yet to be specified. To follow the structural behavior of the material during cycling we set out to investigate O3-NaCrO2 by operando powder X-ray diffraction. During charge the material was expected to follow the well-known phase transitions; O3→O’3→P’3. We here uncover that during charge the material undergo a phase transition not described prior to this work. We have matched this to be an additional O’3 phase expanded in the c-direction (O’3-E). Showing that the material reaction as a two-phase reaction from O’3→O’3-E, which act as a solid solution until the P’3 is formed via an additional two-phase reaction. Furthermore, to understand how the material disorder upon deep charge we investigated the structural evolution with operando total scattering analyzed with pair distribution function (PDF) analysis. From ex situ PDF analysis, we have been able to confirm, that Cr-migration occurs when charged beyond 50 %. Preliminary analysis of the operando PDF shows an increase in the probability of a Cr-O bond at 1.7 Å indicating that a tetrahedral coordinated chromium is likely to be formed during charge.

D.3.4
15:15
Authors : Fabrizio Murgia,a Matteo Brighi,a Claudia E. Avalos,b Pascal Schouwink,c Valerio Gulino,d Radovan Cerny.a
Affiliations : aLaboratory of Crystallography, Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, CH-1211 Geneva, Switzerland bLaboratory of Magnetic Resonance, Institute of Chemical Sciences and Engineering, EPFL, CH-1015 Lausanne, Switzerland cEPFL, ISIC, Rue de l?Industrie 17, CH-1950, Sion, Switzerland dInorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, 3584 CG Utrecht, The Netherlands

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 back again, since it was shown that, in particular conditions, they allow fast cationic conduction.1 However, elevated ionic motion occurs only after a structural phase change, generally beyond room temperature (rt). Many efforts have been made to decrease the phase transition temperature, which has been found also influenced by the charge, size and shape of the hydride's polyanion. Therefore, frustrating the anion sublattice by anion mixing, is an effective strategy to stabilize down to rt the conductive phase (? > 1 mS cm-1). Following this approach, we studied a group of fast Na+ conductors, obtained by mechanical mixing of different closo- and carba-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.3 Electrochemical stability has been evaluated by means of CV and resulted 4.1 V vs. Na+/Na, being compatible with high-voltage operating positive electrodes.4,5 More generally, it has been shown that the oxidative window of these solid electrolytes is limited by the electrochemical stability of the less stable anion, confirming that even at the solid-state, [CB11H12]- is the more robust anion of the pool (>4.2 V vs. Na+/Na).6 Such evidence has been driving the search for alternative strategies to frustrate the anion landscape of NaCB11H12. High-energy mechanical milling induces crystalline defects (stacking faults and dislocations) responsible of the stabilization of a new conductive phase (? = 3.4 mS cm-1 at rt), not present in the reach polymorphism of NaCB11H12. Milling time crucially affect the EIS response, showing an ?optimum? on grinding time, after that decomposition?s phenomena depletes the ionic conductivity.6 IR, XPS and online MS analysis have been carried out to study the interplay of this two aspects as function of milling time (provided energy). The anions dynamics and its role on the Na+ mobility were studied by solid-state NMR, comparing pristine and mechanically milled NaCB11H12, underlining the different relaxation time-scales. Lastly, dealing with electrochemical performance, the determination of the critical current density, (i.e. maximum current density before nucleate dendrites) will be discussed, showing both pressure-dependent EIS and galvanostatic cycling on different Na+ ionic conductors,7 underlying the crucial role of stacking pressure for targeting enhanced electrochemical performance. (1) Matsuo et al Appl Phys Lett 2007 912 5 (2) Tang, et al Energy Environ Sci 2015 8 3637 (3) Brighi et al J Pow Sources 2018 404 7 (4) Murgia et al Electrochem Comm 2019 106 106534 (5) Asakura et al Energy Env Sci 2020 (6) Brighi et al Cell Press Phys Sci 2020 1 100217 (6) Murgia et al Submitted 2021 (7) Brighi et al Submitted 2021

D.3.5
15:45 Q&A    
16:00 Break    
 
Session 4: Approaches Beyond Conventional Li-Batteries : Philipp Adelhelm
16:30
Authors : G. Paradol1, C. Millot1, 2, J.-F. Colin2, H. Mendil-Jakani1, J. Alper3, N. Herlin3, L. Porcar4, G. Gebel2, C. Villevieille5 and S. Lyonnard1,*
Affiliations : 1 Univ. Grenoble Alpes, CEA, CNRS, IRIG, SyMMES, F-38000 Grenoble; 2 Univ. Grenoble-Alpes, CEA LITEN, F-38000 Grenoble; 3 CEA IRAMIS ; 4 Institut Laue-Langevin ; 5 Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, Grenoble INP, LEPMI, F-38000 Grenoble

Resume : Owing to its impressive specific capacity (3579 mAh.g-1) and its low working potential during cycling, silicon is the most promising alternative to lithium metal as anode material for lithium-ion batteries. However, silicon anodes present several drawbacks such as poor cycling stability and capacity fading, both caused by the alloying reaction leading to up to 310% volume change of the silicon, generating particle fractures. Once fractured, the “new fresh” surface needs to be passivated again which generated a continuous growing of the Solid Electrolyte Interphase (SEI). The use of nanoparticles has been demonstrated to avoid the fractures of the particles and thus limits the degradation mechanisms associated with continuous expansion/ shrinking sequences. However, the electrochemical performance, even in nanoparticles Si, are still below the expectations and mechanistic insights into the ageing processes are needed. Understanding in details the alloying reaction mechanism between Si-Li is key to rationalize the ageing process of the anode. Generally, the literature describes the first lithiation as a core-shell mechanism, where the shell is a LixSi amorphous alloy (x being estimated in a range from 2.9 to 3.5), that further crystallizes into Li15Si4 when the potential gets below 50 mV vs. Li /Li. During the delithiation, lithium is extracted through a biphasic mechanism involving c-Li15Si4 and an amorphous LixSi alloy (x estimated to be 2). To track in real-time the evolution of silicon during cycling, and monitor the nanostructural changes of silicon particles during the first lithiation and delithiation, we performed an operando small-angle neutron scattering (SANS), using a custom-made battery cell. The cell was cycled at C/20 using conventional liquid organic electrolyte and Li metal as counter-electrode. The SANS 1D profiles were recorded and analysed using a core-shell form factor. Quantitative parameters as core dimension, shell dimension, and mean shell composition at each voltage, were extracted. We were able to determine the volume expansion of the particles as well as the composition of the LixSi shell during the cycle, providing a direct insight into the succession of phases formed and their impact on the structural evolution of the particles. These results allow us to propose a detailed mechanism of the alloying reaction.

D.4.1
16:45
Authors : Yao Adaba, Laurent Castro, Phillipe Poizot, Stéven Renault
Affiliations : Yao Adaba (Université de Nantes, Institut des Materiaux Jean Rouxel, IMN, F-44000 Nantes, France); Laurent Castro (TME-Toyota Motor Europe NV / SA, Research & Developpement 1, Hoge Wei 33 A, B-1930 Zaventem, Belgium); Philippe Poizot (Université de Nantes, Institut des Materiaux Jean Rouxel, IMN, F-44000 Nantes, France); Stéven Renault (Université de Nantes, Institut des Materiaux Jean Rouxel, IMN, F-44000 Nantes, France)

Resume : As the world moves toward electromobility and a concomitant decarbonization of its electrical supply, modern society is also entering a so-called fourth industrial revolution marked by a boom of electronic devices and digital technologies. Consequently, battery demand has exploded. Introduced on the market in 1991, lithium-ion batteries (LIBs) is becoming a flagship technology possibly able to power an increasingly diverse range of applications from microchips to the emerging large-scale application markets of electric vehicles However, their energy density is still too low for long range applications especially per unit of volume, as compared to internal combustion engines. In order to surpass the performances offered by current LIBs, the chemistries based on the Li-O2 couple in aprotic electrolyte seem promising to really provide ultrahigh-energy density values. The main targeted application is the powering of electrified vehicles with the hope of achieving a reasonable driving range (typically more than 550 km before charging, ca. 340 miles). A typical design for aprotic Li-O2 batteries is composed of a negative electrode made of metallic lithium, an electrolyte comprising a dissolved lithium salt in an aprotic solvent, a separator (e.g., glass fiber or a Celgard film), and a porous O2-breathing positive electrode composed of black carbon particles often blended with catalyst particles. Li-O2 batteries could, in principle, double the gravimetric energy density over the current Li-ion technology, but serious side-reaction issues have plagued their development for practical applications. For example, during the discharge process, some undesired insulating products are formed instead of lithium peroxide. Moreover, the blocking/clogging effect on the air electrode due to a selected deposition process leads to an overpotential during both the discharge (Oxygen Reduction Reaction: ORR) and charge processes (Oxygen Evolution Reaction: OER), which results in electrode degradation, electrolyte decomposition and precocious cell death. Another striking point is that reported capacities are often lower than those expected based on the available porosity. The aim of this work is to use commercial polycyclics aromatics hydrocarbons (PAH) such as pyrene, perylene and coronene as additives in the fabrication of the porous carbonaceous positive electrode. Their solubility in the liquid electrolyte system creates new accessible surface areas in the air electrode, which improved the performance of the Li-O2 batteries.

D.4.2
17:00
Authors : Matthieu Becuwe, Jennifer Bidal, Caroline Hadad, Albert Nguyen Van Nhien
Affiliations : Laboratoire de Réactivité et Chimie des Solides, UMR 7314 CNRS, Université de Picardie Jules Verne, Amiens 80039, France; Réseau sur le Stockage Electrochimique de l’Energie (RS2E), CNRS FR3459, Amiens 80039, France; Institut de Chimie de Picardie FR CNRS 3085, Amiens 80039, France; Laboratoire de Réactivité et Chimie des Solides, UMR 7314 CNRS, Université de Picardie Jules Verne, Amiens 80039, France; Laboratoire de Glycochimie, des Antimicrobiens et des Agroressources, UMR 7378 CNRS, Université de Picardie Jules Verne, Amiens 80039, France; Réseau sur le Stockage Electrochimique de l’Energie (RS2E), CNRS FR3459, Amiens 80039, France; Institut de Chimie de Picardie FR CNRS 3085, Amiens 80039, France; Laboratoire de Glycochimie, des Antimicrobiens et des Agroressources, UMR 7378 CNRS, Université de Picardie Jules Verne, Amiens 80039, France; Institut de Chimie de Picardie FR CNRS 3085, Amiens 80039, France; Laboratoire de Glycochimie, des Antimicrobiens et des Agroressources, UMR 7378 CNRS, Université de Picardie Jules Verne, Amiens 80039, France; Institut de Chimie de Picardie FR CNRS 3085, Amiens 80039, France

Resume : The energetic context prompts the search for efficient and low-cost energy storage technologies either as an energy reservoir for supplying electronics, engines, etc… or as a buffer for grid applications to stabilize intermittent renewable energy production. Ion-based electrochemical storage systems (secondary batteries, supercapacitors, redox-flow,…) stand as one of the best solutions to address such challenges. As a consequence, numerous efforts were focused on improving electrode performances (energy/power densities), the safety of the full devices (solid-state batteries), and also their environmental footprint. To make them safer both in use and after disposal, one option is to substitute common liquid electrolytes with solid-state electrolytes in order to build all-solid-state batteries having longer cycle life, higher energy density, and fewer requirements on the packaging. The solid-state electrolyte is the key component of such technology and attracts the attention of the scientific community for the last years. In this race of performances, many types have been investigated. However, an insufficient room-temperature ionic conductivity (10-5-10-3 S.cm-1) and lithium transport number, and poor electrode-electrolyte interface hinder the reality of these devices. One other promising option allowing to get good performance while substituting strategic materials and metallic element difficult to recycle is to use immobilized or grafted ionic liquids onto the surface of simple nanometric material to ensure ion mobility. This new type of hybrid materials, still modestly developed, offer mechanical strength and lithium-ion conductivity comparable to that of solid polymer electrolytes. In this field, silica-based materials are the most used supports in the literature, which is explained by their fast synthesis as well as surface properties tuning by functionalization using organosilane. However, multistep synthesis and stringent anhydrous conditions are required to ensure the grafting of monomers only, perfect monolayer creation, as well as a reproducible grafting rate. It is of great interest to be able to control hybrid material syntheses so as to precisely reproduce them, in an industrial application, and to better understand the relationship between structure and ion transport properties. Especially in the case of ion conduction, organization and mobility pathway are essential to maximizing conduction performance. At this point, it is important to notice that a clear tendency of the structure−property relationship is not yet established. We propose here to address this point by presenting the key parameters impacting lithium mobility in a well-defined hybrid electrolyte based on ionic-liquid immobilized, as a monolayer, on the surface of metal oxide nanoparticles. The effect of the ionic liquid structure, the type of anchoring, and the textural parameters of the inorganic materials will be discussed.

D.4.3
17:15
Authors : Min Deng*(1), Linqian Wang (1), Bahram Vaghefinazari (1), Darya Snihirova (1), Sviatlana V. Lamaka (1), Daniel Höche (1), Mikhail L. Zheludkevich (1,2)
Affiliations : (1) Institute of Surface Science, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany; (2) Institute of Materials Science, Faculty of Engineering, Kiel University, 24143 Kiel, Germany.

Resume : Mg is a promising anode material for cheap, safe and high energy batteries enabled by its abundance in earth crust, high volumetric capacity and low redox potential. Particularly, primary aqueous Mg batteries exhibit great potential in many applications like maritime equipment and transient bioelectronics. Mg anode, specifically the anode efficiency, is crucial for battery capacity and energy density. Unfortunately, Mg anodes developed by traditional alloying with large element additions rarely show high efficiency (e.g. >60% at 10 mA/cm2). One major issue is the efficiency loss due to the detachment of undissolved metallic particles (chunk effect), which is related to anode inhomogeneous dissolution due to large amounts of secondary phase and impurity precipitates. Moreover, these precipitates accelerate the anode corrosion and possibly self-corrosion. In this context, this work reveals that micro-alloying (Ca-based and beyond) paves a new way to high performance Mg anodes for advanced aqueous batteries. Mg-air battery with Mg-0.1wt%Ca anode showed enhanced voltage and energy density in comparison to commercial Mg anodes. Anode performance can be further boosted via micro-alloying of Ge and In. Noticeably, Mg-0.1wt%Ca-0.2wt%In anode exhibited efficiency higher than 80%. Battery voltage and energy density were simultaneously elevated by this Ca/In micro-alloyed anode. The achieved superior properties were attributed to the reduced self-corrosion and suppressed chunk effect.

D.4.4
17:30
Authors : Ramulu Bhimanaboina, S. Chandra Sekhar, Shaik Junied Arbaz, Manchi Nagaraju, and Jae Su Yu*
Affiliations : Department of Electronics and Information Convergence Engineering, Institute for Wearable Convergence Electronics, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Republic of Korea

Resume : It is important to develop renewable energy storage devices owing to environmental concerns such as ever-increasing energy demand and the gradual depletion of fossil fuels. Particularly, supercapacitors (SCs) have attracted prominent attention as nature-friendly energy storage devices due to their outstanding properties of rapid charging and discharging, excellent power density, and cycling stability. Usually, SCs are categorized into two types depending on the charge-storage mechanism. One is an electric double-layer capacitor, where the charge can be stored in a non-Faradaic manner. The other is pseudocapacitor (PC) in which the charge can be stored through the Faradaic redox process with active materials. Transition metal oxides like MnO2 and RuO2 are studied as PC-type electrode materials. In contrast, Co3O4, NiWO4, CuCoO4, Ni(OH)2, NiMoO4, CoNiO4, etc. have been broadly examined as battery-type materials and they can exhibit comparatively higher specific capacity/capacitance and energy density than PC-type materials, because of their higher redox properties and electrochemical activity. Nowadays, metal-organic frameworks (MOFs) as a novel family of advanced electrode materials have gained significant interest in various fields such as catalysis and energy storage systems owing to their efficient properties such as benefited structural properties, high surface area, and chemical tunability. Especially, the surface features of MOFs increase the electrolyte uptake capability and diminish the diffusion in energy storage systems. Thus, we synthesized MOF-based electrode materials using a facile solvothermal approach. The as-prepared electrode materials are investigated by various electrochemical tests to expose their applicability as electrodes in SCs.

D.4.5
17:45
Authors : Jorge Salgado-Beceiro1, Julian Walker2, Alberto García-Fernández3, Juan Manuel Bermúdez-Garcia1, Javier García-Ben1, Ignacio Delgado-Ferreiro1, Socorro Castro-Garcia1, Manuel Sánchez-Andujar1, Ute B Cappel3, Mari-Ann Einarsrud2, and María Antonia Señarís-Rodríguez1
Affiliations : 1 University of A Coruna, QuiMolMat Group, Dpt. Chemistry, Faculty of Science and Advanced Scientific Research Center (CICA), Zapateira, 15071 A Coruña, Spain. 2 Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, N-7491 Trondheim, Norway. 3 Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden

Resume : Hybrid ionic plastic crystal systems, which are composed of inorganic anions and organic cations, have attracted great interest due to their outstanding functional properties (such as caloric, dielectric, magnetic or optical properties) and their potential applications in a wide variety of fields (such as for thermal energy storage, capacitors, sensors and transducers, memory devices, photonics and optoelectronics, among other applications).1–4 From the structural point of view, the molecular nature of the hybrid ionic plastic crystal systems, with weakly associated inorganic anions and organic cations, typically show solid-to-solid phase transitions with large latent heat. These phase transitions are associated to order-disorder processes of the molecular species, which exhibit a large orientational or conformational degree of disorder in the high-temperature phase (or plastic crystal state).5 Very interestingly, different hybrid ionic plastic crystals have recently been reported to display outstanding dielectric properties at room temperature, such as ferroelectricity and piezoelectricity.6 The relatively large mechanical flexibility of these systems offers a promising family of materials for sensors and electric storage applications. The current commercial ceramic ferroelectrics have several drawbacks, such as difficult synthesis and fragility, so hybrid ionic plastic crystals suppose a promising alternative to these materials. Furthermore, the large latent heat exhibited by these hybrid ionic plastic crystals at the phase transition was reported to be suitable for thermal energy storage applications.7 Therefore, these materials are very promising for multi-energy storage of both thermal and electrical storage. In this context, we have recently reported a new halometallate [(CH3)3S]FeCl4 with a relatively large latent heat (~40 kJ kg-1) and an operational temperature for storing and releasing thermal energy between 42 oC (315 K) and 29 oC (302 K), appropriate for solar thermal energy storage. Additionally, this phase transition is associated with a large and sharp increase of the dielectric permittivity, which can be useful for electrical storage in a capacitor.8 In this work, we have synthesized new halometallates and studied their thermodynamic and dielectric properties to discover new multi-energy storage materials. We obtained several new ionic plastic crystals and characterized their crystal structure at different temperatures by single crystal and powder X-ray diffraction. Very interestingly, several of the new materials have a polar crystal structure and a phase transition with a large latent heat and dielectric transition. Therefore, we have been able to obtain and characterize novel polar ionic plastic crystals useful for thermal and electrical storage. References: 1 A. Sharma, V. V. Tyagi, C. R. Chen and D. Buddhi, Renew. Sustain. Energy Rev., 2009, 13, 318–345. 2 T. Mochida, M. Ishida, T. Tominaga, K. Takahashi, T. Sakurai and H. Ohta, Phys. Chem. Chem. Phys., 2018, 20, 3019–3028. 3 K. Y. Chan, B. Jia, H. Lin, N. Hameed, J. H. Lee and K. T. Lau, Compos. Struct., 2018, 188, 126–142. 4 X. Zhang, X. Wang and D. Wu, Energy, 2016, 111, 498–512. 5 J. Timmermans, J. Phys. Chem. Solids, 1961, 18, 1–8. 6 J. Walker, S. Scherrer, N. S. Løndal, T. Grande and M.-A. Einarsrud, Appl. Phys. Lett., 2020, 116, 242902. 7 D. Li, X. M. Zhao, H. X. Zhao, L. S. Long and L. S. Zheng, Inorg. Chem., 2019, 58, 655–662. 8 J. Salgado-Beceiro, J. M. Bermúdez-García, A. L. Llamas-Saiz, S. Castro-García, M. A. Señarís-Rodríguez, F. Rivadulla and M. Sánchez-Andújar, J. Mater. Chem. C, 2020, 8, 13686–13694.

D.4.6
18:00 Q&A    
Start atSubject View AllNum.Add
 
Session 5: Fundamental aspects of High Entropy Alloys : Erika Dematteis
09:00
Authors : C. Zlotea, J. Montero, A. Bouzidi, N. Pineda-Romero, and J-P. Couzinié
Affiliations : Univ Paris Est Créteil, CNRS, ICMPE, UMR 7182, 2 Rue Henri Dunant, 94320, Thiais, France

Resume : Among various materials for solid-state hydrogen storage, alloys and intermetallics forming hydrides are one of the most important classes due to their high-volume density, reversibility, and safety. Recently, a new paradigm of alloying in metallurgy has emerged based on the concept of high entropy alloys (HEAs), initially intended to enhance the mechanical properties. The principle is laid on the mixing of elements close to the equimolar proportion for systems up to five and more elements. This may lead to the formation of simple single-phased solid solutions (bcc, fcc and hcp) with large lattice distortion that can be favorable for hydrogen uptake. We report here the synthesis, the physicochemical and the hydrogen absorption/desorption properties of a series of HEAs (Ti0.30V0.25Zr0.10Nb0.25)X0.10 with X = Mg, Al, Cr, Mn, Fe, Co, Ni, Zn, Mo and Ta. A large pallet of experimental methods has been employed such as, laboratory/synchrotron X-ray diffraction, electron microscopy, in situ neutron diffraction, pressure-composition-isotherm, thermal desorption spectroscopy and differential scanning calorimetry. All the Ti-V-Zr-Nb-X alloys are single-phase bcc and undergo either a one-step (initial - dihydride) or a two-stage hydrogen sorption (initial - monohydride - dihydride). The role of additional element will be highlighted and compared to the quaternary Ti-V-Zr-Nb alloy as function of local lattice distortion and electronic properties. For example, adding light elements such as, Mg and Al, slightly decreases the capacity however, it improves the stability upon cycling as compared to the quaternary Ti-V-Zr-Nb alloy. The addition of Fe, Co, Ni or Zn strongly reduces the hydrogen uptake whereas, Cr, Mn, Mo and Ta improves the overall capacity. The most promising alloys have been the object of in situ neutron diffraction study to address the phase transition during desorption by heating under dynamic vacuum and the deuterium occupancy in the hydride phase. This approach is envisioned to clarify the role of additional elements on the hydrogen storage performances of refractory HEAs.

D.5.1
09:30
Authors : Anis Bouzidi , Claudia Zlotea
Affiliations : Univ Paris Est Créteil, CNRS, ICMPE, UMR 7182, 2 Rue Henri Dunant, 94320, Thiais, France

Resume : Hydrogen as a clean energy carrier is a viable future energy alternative. The lightweight and safe hydrogen storage is the key for the development of hydrogen-based clean energy carrier. There are several technologies for hydrogen storage. The solid-state storage through metal hydrides is a safe and compact option that has the potential to be used in mobile and stationary applications. Among the numerous studied metals, alloys and intermetallics, the high entropy alloys recently showed promising capacity of absorption. For example, the TiVZrNbHf alloy has a superior capacity of absorption than conventional alloys or individual components up to 2,5 H/M (hydrogen per metal atom) [1]. This work aims to study the effect of the addition of 10% of Mo into Ti0.325V0.275Zr0.125Nb0.275 on the hydrogen sorption properties. This composition was optimized to obtain single-phase BCC alloy based on our previous works [2]. The Ti0.30V0.25Zr0.10Nb0.25Mo0.10 alloy was prepared by high temperature arc melting and crystallizes into a single-phase BCC lattice. The alloy absorbs large hydrogen amount of 2.0 H/M (3 wt%) at ambient temperature forming a single-phase FCC dihydride. This value is higher as compared to 1.7 H/M (2.5 wt%) of the initial Ti0.325V0.275Zr0.125Nb0.275. Additionally, the study of the structural properties and phase transformation during Deuterium desorption were studied in situ by neutron diffraction and shows a sharp single-phase transition at 515 K from FCC dihydride phase to the pristine single-phase BCC. After 20 cycles of Abs/Desorption, the alloy experiences a small fading in the capacity by 13% after the first 6 cycles and stabilizes to around 1.73 H/M (2.5 wt%) for further cycling. [1] Sahlberg M., et al. Sci. Rep;6:36770.(2016). [2] Montero, J., et al. Molecules, 24, 2799.( 2019)

D.5.2
09:45
Authors : N. Pineda-Romero, C. Zlotea
Affiliations : Univ Paris Est Créteil, CNRS, ICMPE, UMR 7182, 2 Rue Henri Dunant, 94320, Thiais, France

Resume : Hydrogen has a strong potential to be a replacement for fossil fuels but an important research effort is needed for finding efficient storage materials to be used in practical devices. H2 can be stored in solid-state as metal hydrides which possess the advantages of high safety as compared to gas storage, and high volumetric capacity exceeding those of liquid H2. Metal hydrides are well studied for solid-state H2 storage, but most alloys have not yet fulfilled all the needs for profitable and efficient storage. On the other hand, a new class of materials, known as multi-principal element alloys (MPEA) or high-entropy alloys (HEA), have captured the attention because of their simple crystalline structures (BCC, FCC, HCP) and large lattice distortion that could accommodate important hydrogen uptake, as proven for the TiVZrNbHf in past studies. In this report, we study the hydrogen storage properties of novel HEA’s containing refractory elements (Ti, V, Nb) and Al. The Alx(TiVNb)100-x (x = 0, 5, 10, 17.5 and 25 at.%) compositions were synthesized by arc melting method. We establish the influence of Al content on the formation of the BCC phase and on the hydrogen storage properties such as the storage capacity, desorption profiles, absorption kinetics, and cycling stability. As the first results, the increase of Al content maintains a single-phase BCC lattice and decreases the unit parameter as well as the lattice distortion. Moreover, XRD after Thermo-Desorption-Spectroscopy (TDS) proven that hydrogen absorption and desorption are fully reversible. In situ neutron diffraction on the composition Al10(TiVNb)90 demonstrated that the dihydride phase is FCC and the full desorption of deuterium induces a phase transition from FCC to a BCC lattice at around 530 K. Pressure-Composition-Isotherm measurements were carried out for this composition and show a two-plateaus behavior. The as-cast alloy absorbs hydrogen at very low pressure to form a BCC monohydride (0.8 H/M) followed by the formation of a dihydride phase at higher pressures (1.6 H/M). Further analysis is in progress in order to better assess the effect of Al addition on the other storage properties such as absorption/desorption cycling.

D.5.3
10:00
Authors : Jonina Felbinger* (1), Inga Bürger (1), Marc Linder (1) *lead presenter
Affiliations : (1) German Aerospace Center (DLR e.V.), Pfaffenwaldring 38-40, 70569 Stuttgart, Germany

Resume : By deploying the gas pressure dependent thermal conductivity of porous structures vacuum insulation panels can be transformed into thermal barriers with controllable heat flux. The controllable vacuum insulation layer requires the concise adjustment of the gas pressure in the insulation panel. Reversible gas-solid reactions are a promising approach to set the gas pressure in a coupled porous insulation panel by tempering the solid reaction part along the equilibrium line. A suitable material combination is the metal hydride reaction system. Compatible metal hydrides for the application in variable conductance vacuum insulation layers are required to work reliably in vacuum regimes, show fast kinetics, and reach the vacuum pressure in technically interesting temperatures ranges between 0 °C and 200 °C. Metal hydrides that fulfil these requirements are lanthanum nickel or zirconium nickel alloys, for instance. A combination of these alloys in a cascading operation mode is considered to provide the appropriate gas pressure adjustment for the thermally controllable barrier. Thus, a dedicated understanding of the metal hydride materials ? individually and cascadingly interconnected ? in vacuum regime is prerequisite. The cascade connection of several metal hydride materials in the same reactor enables the possibility to provide a wide gas pressure range whilst applying a reduced required temperature range for the endo-/exothermal reaction. Our current work addresses characterization investigations on the manner of reaction of the alloys below atmospheric pressure. The main challenging question is the measurement of the pressure-concentration-isotherms of the metal hydrides in high vacuum. Usual experimental setups to conduct PCI-measurements dynamically are not able to cover high vacuum conditions, thus we built up a test bench ? including an appropriate reactor design - to carry out static PCI measurements. The driving parameter at this is the temperature of the metal hydride bulk while the according gas pressure is the dependent value. The hydrogen concentration is fixed and is stepwisely varied in different measurement series. The contribution will focus on the experimental investigations in terms of the characterization of zirconium nickel as well as lanthanum nickel alloys for high vacuum applications and will identify the potential of the cascade connection of different metal hydrides to adjust the gas pressure in the vacuum panel effectively. The specifically for static PCI measurements constructed test bench will be introduced as well as the results of PCI correlations will be outlined and discussed.

D.5.4
10:30 Q&A    
10:45 Break    
 
Session 6: Hydride-based materials : Claudia Zlotea
11:00
Authors : Erika Michela Dematteis,1-2* David Dreistadt,3 Giovanni Capurso,3 Julian Jepsen,3 Jussara Barale,1 Stefano Deledda,4 Fermin Cuevas,2 Michel Latroche,2 Marcello Baricco1
Affiliations : 1 University of Turin, Department of Chemistry and NIS - INSTM, Via Pietro Giuria 7, 10125 Torino, Italy; 2 Univ Paris Est Creteil, CNRS, ICMPE, 2 rue Henri Dunant, 94320 Thiais, France; 3 Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon, Max-Plank-Str. 1, 21502 Geesthacht, Germany; 4 Institute for Energy Technology, Kjeller, NO-2027, Norway

Resume : Hydrogen is a suitable carrier for renewable energy sources, enabling the transition towards CO2-free energy, and storage for long periods in solid-state materials. TiFe can store up to 1.86 wt.% hydrogen in mild conditions of temperature and pressure. Elemental substitution in TiFe enables easy activation and fine tuning of thermodynamics for hydrogen sorption, as a function of the envisaged application.[1] Ti, Mn, and Cu substitutions for Fe in TiFe have been explored, to select an optimised alloy composition for large-scale H2 storage at low pressure. The alloys were synthetized by induction melting and annealed at 1000 °C. After activation, fundamental hydrogenation properties have been determined (thermodynamics, kinetics and cycling). For more comprehensive structural studies, in-situ neutron diffraction experiments during deuterium loading have been performed in a custom-made stainless-steel sorption cell. First studies with Mn and Cu substitution for Fe demonstrate that the first hydrogenation (activation) can be achieved in mild conditions, enabling a broad use of TiFe-alloy.[2] The compositional exploration of the Ti-Fe-Mn system led to the determination of hydrogenation properties dependency over an extended Ti and Mn compositional range.[3] Ti and Mn substitutions at Fe site enlarge the TiFe cell volume, while decreasing the plateau pressures and hysteresis between absorption and desorption. Samples at the Ti-rich side have enhanced reversible storage capacities. The formation of secondary phases improves also the activation process. The crystal structures of TiFe(0.90-x)Mnx alloys (x = 0, 0.05, and 0.10) and their deuterides have been determined by in-situ neutron diffraction, while recording Pressure-Composition Isotherms at room temperature.[4,5] The investigations aimed at analysing the influence of stoichiometry and Mn for Fe substitution in TiFe-type alloys on structural properties during reversible deuterium loading. In conclusion, this study brings remarkable understanding on the hydrogen storage properties, basic structural knowledge, and support to the industrial usage of TiFe-type alloys for integrated hydrogen tank in energy storage systems. For large-scale hydrogen storage, TiFe-type alloys form room temperature hydrides under low gas pressure (below 5 MPa at RT) and are suitable for this purpose. The HyCARE project (www.hycare-project.eu) aims at developing an efficient integrated system to store approx. 50 kg of hydrogen in solid-state using such TiFe-based material. The system will be installed at the Engie Criogen Lab. in Paris in mid-2022. References: [1] E.M. Dematteis, N. Berti, F. Cuevas, M. Latroche, M. Baricco, Substitutional effects in TiFe for hydrogen storage: a comprehensive review, Mater. Adv. (2021). https://doi.org/10.1039/D1MA00101A. [2] E.M. Dematteis, F. Cuevas, M. Latroche, Hydrogen storage properties of Mn and Cu for Fe substitution in TiFe0.9 intermetallic compound, J. Alloys Compd. 851 (2021) 156075. https://doi.org/10.1016/j.jallcom.2020.156075. [3] E.M. Dematteis, D.M. Dreistadt, G. Capurso, J. Jepsen, F. Cuevas, M. Latroche, Fundamental hydrogen storage properties of TiFe-alloy with partial substitution of Fe by Ti and Mn, J. Alloys Compd. (2021) 159925. https://doi.org/10.1016/j.jallcom.2021.159925. [4] F. Cuevas, S. Deledda, E.M. Dematteis, B.C. Hauback, M. Latroche, L. Laversenne, J. Zhang, In-situ neutron diffraction during reversible deuterium loading in under-stoichiometric and Mn-substituted Ti(Fe,Mn)0.9 alloys, Inst. Laue-Langevin. (2020). https://doi.org/10.5291/ILL-DATA.5-22-771. [5] E.M. Dematteis, B.C. Hauback, I. da Silva Gonzalez, S. Deledda, F. Cuevas, M. Latroche, G. Capurso, J. Barale, In-situ neutron diffraction during reversible deuterium loading in under-stoichiometric and Mn,Cu-substituted Ti(Fe,Mn,Cu)0.9 alloys, STFC ISIS Neutron Muon Source. (2019). https://doi.org/10.5286/ISIS.E.RB1920559-1.

D.6.1
11:30
Authors : K. Asano1, Y. Lu1, H. Schreuders2, V. Charbonnier1, H. Kim1, K. Sakaki1, H. Enoki1, Y. Nakamura1, E. Akiba3, B. Dam2
Affiliations : 1 National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan; 2 Delft University of Technology, Delft, The Netherlands; 3 Kyushu University, Fukuoka, Japan

Resume : Mg is one of the most attractive hydrogen storage materials due to its high volumetric and gravimetric storage capacity and low material costs. However, the hydride phase MgH2 is too stable to desorb hydrogen at ambient pressure and temperature, and thus unsuited for practical stationary and onboard applications. One of the possible ways to destabilize MgH2 is the downsizing on a nanometer scale. We have first proposed to synthesize nanometer-sized MgH2 by combining immiscible metals with Mg. For Ti-rich Mg-Ti nonequilibrium alloy, nanometer-sized MgH2 clusters coherently embedded in a TiH2 matrix were formed upon hydrogenation1). Indeed, MgH2 is destabilized by the interface energy between the two metal hydrides2,3). The chemical segregation on a nanometer scale accompanies stress-induced strain and structural change of MgH24,5). However, stabilization of a part of MgH2 was also observed due to local dissolution of Ti into the Mg domains: since TiH2 is more stable than MgH2, hydrogen atoms occupying the interstitial sites are stabilized by the Ti coordination. Then we have focused on a nonhydride forming matrix which is again immiscible with Mg. We synthesized nonequilibrium Mg-Mn6) and Mg-Cr7) alloys, leading only to the destabilization effect of MgH2 without any interfering stabilization effect. Our results suggest that we can tune the thermodynamics of hydrogen absorption and desorption in Mg-H using the nanometer-sized effect, which contributes to the substantial development of lightweight and inexpensive hydrogen storage materials. Recently, we are expanding the target to nanometer-sized Mg2FeH6 embedded in Mg2Si8) and allotropic MgH2 formed by hydrogenation of Mg-Cu-Y alloy with a Long Period Stacking Ordered (LPSO) structure9). In this talk, those new systems developed by our group will be also introduced. This work was supported by JSPS Kakenhi Grants 17K06853 and 21H01744, the Photon and Quantum Basic Research Coordinated Development Program by MEXT, and the International Joint Research Program for Innovative Energy Technology by METI. References: 1) K. Asano, H. Kim, K. Sakaki, K. Page, S. Hayashi, Y. Nakamura, E. Akiba, J. Alloys Compd. 593, 132-136 (2014). 2) K. Asano, R. J. Westerwaal, A. Anastasopol, L. P. A. Mooij, C. Boelsma, P. Ngene, H. Schreuders, S. W. H. Eijt, B. Dam, J. Phys. Chem. C 119, 12157-12164 (2015). 3) K. Asano, R. J. Westerwaal, H. Schreuders, B. Dam, J. Phys. Chem. C 121, 12631-12635 (2017). 4) K. Asano, H. Kim, K. Sakaki, K. Jimura, S. Hayashi, Y. Nakamura, K. Ikeda, T. Otomo, A. Machida, T. Watanuki, Inorg. Chem. 57, 11831-11838 (2018). 5) H. Kim, H. Schreuders, K. Sakaki, K. Asano, Y. Nakamura, N. Maejima, A. Machida, T. Watanuki, B. Dam, Inorg. Chem. 59, 6800-6807 (2020). 6) Y. Lu, H. Kim, K. Sakaki, K. Jimura, S. Hayashi, K. Asano, Inorg. Chem. 58, 14600-14607 (2019). 7) Y. Lu, H. Kim, K. Jimura, S. Hayashi, K. Sakaki, K. Asano, J. Power Sources 494, 229742 (2021). 8) K. Asano, H. Kim, K. Sakaki, Y. Nakamura, Y. Wang, S. Isobe, M. Doi, A. Fujita, N. Maejima, A. Machida, T. Watanuki, R. J. Westerwaal, H. Schreuders, B. Dam, Inorg. Chem. 59. 2758-2764 (2020). 9) V. Charbonnier, K. Asano, H. Kim, K. Sakaki, Inorg. Chem. 59, 14263-14274 (2020).

D.6.2
11:45
Authors : Ebert Alvares, Archa Santhosh, Bo Sundman, Martin Dornheim, Paul Jerabek
Affiliations : Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon, Max-Planck Strasse 1, Geesthacht, D-21502, Germany; Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon, Max-Planck Strasse 1, Geesthacht, D-21502, Germany; OpenCalphad, 9 Allée de l’Acerma, 91190 Gif sur Yvette, France; Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon, Max-Planck Strasse 1, Geesthacht, D-21502, Germany; Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon, Max-Planck Strasse 1, Geesthacht, D-21502, Germany;

Resume : Among compounds presenting reversible hydrogen storage properties at room temperature, FeTi-hydrides have recently re-attracted interest. These hydrides show good gravimetric and volumetric capacity and present relatively low-cost alternatives to other intermetallics. Due to its fast sorption kinetics and reversibility in mild conditions, this alloy is suitable for applications in hydrogen storage tanks. Moreover, multicomponent FeTi-based systems may have their thermodynamic and kinetic properties tuned by partially substituting Fe and/or Ti by other metallic elements, i.e., adjusting their composition to improve the performance needed by different technological applications. For this reason, developing multicomponent thermodynamic models for the description of stability of metal-hydrides may support the development of novel alloys to satisfy these requirements. In this regard, the CALPHAD method has been recognized as a powerful and consistent tool to accurately calculate the thermodynamic properties of multicomponent systems based merely on assessments of its unary, binary, and ternary subsystems. Therefore, metal-hydrides seem to be good candidates to benefit from computational thermodynamics in the design and the simulation stages. In this work, as an initial step in the modeling of the more complex FeTi-based hydride family, the pseudo-binary FeTi(1-x)H(x) system was chosen and assessed employing the CALPHAD method. The thermodynamic models of the phases were selected based on a critical analysis of literature information. New thermodynamic data was acquired by measuring Pressure-Composition-Isotherm (PCI) curves and by calculating crystallographic and thermochemical properties through Density Functional Theory (DFT). Reliable descriptions of key thermodynamic properties have been demonstrated using the proposed model. The dissociation pressure, PCI curves, formation enthalpies of hydrides, and phase diagrams were calculated and are in good agreement with our newly acquired data and with those reported in the literature. The present work may serve as a ground for higher-order thermodynamic assessments as well as consistent input data for kinetic models, helping the design of novel FeTi-based hydrides and their hydrogenation process simulation.

D.6.3
12:00
Authors : Neslihan Aslan, Gökhan Gizer, Claudio Pistidda, Martin Dornheim, Martin Müller, Sebastian Busch, Wiebke Lohstroh
Affiliations : Neslihan Aslan, German Engineering Materials Science Centre (GEMS) at Heinz Maier-Leibnitz Zentrum (MLZ), Helmholtz-Zentrum Hereon; Gökhan Gizer, Institute of Hydrogen Technlology, Helmholtz-Zentrum Hereon; Claudio Pistidda, Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon; Martin Dornheim, Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon; Martin Müller, Institute of Materials Physics, Helmholtz-Zentrum Hereon, German Engineering Materials Science Centre (GEMS) and Heinz Maier-Leibnitz Zentrum (MLZ); Sebastian Busch, German Engineering Materials Science Centre (GEMS) at Heinz Maier-Leibnitz Zentrum (MLZ), Helmholtz-Zentrum Hereon; Wiebke Lohstroh, Heinz Maier-Leibnitz Zentrum (MLZ), Technical University Munich (TUM)

Resume : The hydrogen storage performance of the Reactive Hydride Composite Mg(NH2)2 + 2 LiH can be significantly improved by the addition of LiBH4 and the subsequent formation of the mixed amide-borohydride compound Li4(BH4)(NH2)3 during hydrogen release. We have investigated the structure and molecular motions of Li4(BH4)(NH2)3 by in situ synchrotron radiation powder X-ray diffraction (SR-PXD) (295-573 K) and quasielastic neutron scattering (QENS) (297-514 K). The highest temperature probed with QENS (514 K) is above the melting point of Li4(BH4)(NH2)3 and the neutron measurements confirm a long-range diffusive motion of hydrogen containing species with the diffusion coeffcient D ~ 10-6 cm2/s, which is comparable to the value of Li+ diffusion inferred from conductivity measurements. SR-PXD confirms the recrystallization of Li4(BH4)(NH2)3 into the α-phase during cooling from the melt. At temperatures below 514 K, localized rotational motions were observed which have been attributed to (BH4)- tetraheder units undergoing rotations mainly around C3 axes. The activation energy for this thermally activated process is found to be Ea = 15.5±0.9 and 17.4±0.9 kJ/mol for the two instrumental resolutions utilized in the QENS measurements, respectively, corresponding to observation times of 55 and 14 ps.

D.6.4
12:15
Authors : Thi-Thu Le, Claudio Pistidda, Thomas Klassen, Martin Dornheim
Affiliations : Institute of Hydrogen Technology, Helmholtz-Zentrum hereon GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany Helmut Schmidt University, Holstenhofweg 85, 22043 Hamburg, Germany

Resume : In this work, a systematic study of the CsNH2-CsH composite in the entire compositional range is investigated. In this context, the formation of the Cs(NH2)xH1-x solid solution underlying the CsNH2-CsH interaction is thoroughly investigated by means of in-situ synchrotron experiments. The Cs(NH2)xH1-x solid-solution in the CsNH2-CsH system is formed by the reaction mechanism of amide-hydride anion exchange, similar to the KNH2-KH and RbNH2-RbH composite systems. The interaction between the H+ ion in the amide and H- ion in the hydride helps to promote the formation of intermediate phases at the amide-hydride interface and in turn enhances the mobility of the ionic species at the interfaces, which is extremely important to achieve fast reaction kinetics of hydrogen storage systems, especially at low temperatures. Through the results of this study, a comprehensive insight into the structural properties of alkali metal amide/hydride systems and their reaction mechanism has been obtained. Therefore, this work could be the basis for further studies aimed at extending this line of research and finding similarities with other composite systems.

D.6.5
12:30 Q&A    
12:45 Break    
 
Session 7: Hydride-based [battery] materials : Zbigniew ŁODZIANA
14:00
Authors : Hujun Cao,* Jiang Wang, Jirong Cui, and Ping Chen*
Affiliations : Dalian Institute of Chemical Physics, Chinese Academy of Sciences, China.

Resume : Mechanochemical approach was employed to synthesize K-based amides such as K2[Zn(NH2)4], K2[Mn(NH2)4], and KNH2 at room temperature and at low gas pressure. Potassium-based amide-hydride storage materials were developed by mixing these amides with hydrides. K2[Zn(NH2)4]-8LiH and K2[Mn(NH2)4]-8LiH showed extremely fast hydrogen absorption kinetics. For example, the dehydrogenated K2[Zn(NH2)4]-8LiH can be fully re-hydrogenated (ca. 3.0 wt% of H2) at 230 °C within 20 s, which is one of the fastest re-hydrogenation kinetics reported in literatures for amide-hydride systems. And these excellent hydrogenation properties can be maintained upon cycling. The ultra-fast hydrogenation reactions of these K-based amide-hydride composites may indicate a fast ionic conductor. Stimulated by this phenomenon, a new type of potassium ion conductor material KNH2 was discovered. Ionic conductivity of the as synthesized KNH2 is 9.84×10-9 and 4.84×10-5 S cm-1 at 40 and 150 ?. KNH2 after mechanochemical treatment at 150 rpm for 10 hours, the ionic conductivity increases to 1.39×10-6 and 3.56×10-4 S cm-1 at 40 and 150 ?, respectively. Experimental results showed that ball milling process improves the ionic conductivity of KNH2 by creating defects in its structure. To the best of our knowledge, this is the first reported case using amide as a new type of potassium fast ion conductor and has great potentials as potassium ion solid electrolyte.

D.7.1
14:30
Authors : Junxian ZHANG, Véronique CHARBONNIER, Nicolas MADERN, Judith MONNIER, Michel LATROCHE
Affiliations : Univ. Paris-Est Créteil, CNRS, ICMPE, UMR7182, F-94320, Thiais, France

Resume : The fossil fuels consumption is not only the main cause of air polluting but also the origin of global warming with more and more alarming consequences. These leads to major consideration for alternatives: solar, wind and sea waves, which requires energy storage for final usage. Hydrogen is one candidate that can be either used as fuel or charge carrier in Ni-MH batteries. Binary compounds Gd2Ni7, Y2Ni7, Sm2Ni7 and La2Ni7 absorb large amounts of hydrogen but show several plateaus and limited reversibility, which is not suitable for applications [1-3]. This behavior is mainly due to the stacked structure and the mismatch between subunits [A2B4] and [AB5]. This mismatch is also responsible for the hydrogen induced amorphization (HIA) of these compounds [4]. Since the atomic size of rare earths plays an important role on this geometrical parameter, it is worth to study the effect of different rare earths on the hydrogenation properties. Indeed, A can be almost all light rare earths (La to Gd), yttrium and alkaline earth metals (Mg or Ca), whereas B can contain various late transition metals (Mn to Ni). To understand the effects of composition on the physicochemical properties of La2Ni7-based compound, various pseudo-binary systems have been investigated: Gd2 xLaxNi7 (x = 0, 0.6, 1, 1.5), Sm2-xLaxNi7 (x = 0, 0.5, 1, 1.5), Y2-xLaxNi7 (x = 0, 0.4, 0.5, 0.6, 0.8, 1, 1.5, 1.75) and R0.5La1.1Mg0.4Ni7 (A = Sm, Gd and Y) [5]. To determine their crystallographic properties, X-ray diffraction analysis was performed, followed by Rietveld refinement. Thermodynamic properties regarding reversible hydrogen sorption were investigated at room temperature. Quaternary compounds present drastically improved sorption properties for practical energy storage applications with reversible capacity equivalent to 400 mAh/g for La1.1Sm0.5Mg0.4Ni7. 1. V. Charbonnier, J. Monnier, J. Zhang, V. Paul-Boncour, S. Joiret, B. Puga, L. Goubault, P. Bernard, M. Latroche, J. Power Sources. 326 (2016) 146. 2. J.-C. Crivello, N. Madern, J. Zhang, J. Monnier, M. Latroche, J. Phys. Chem. C. 123 (2019) 38. 3. K. Iwase, K. Sakaki, Y. Nakamura, E. Akiba, Inorg. Chem. 52 (2013) 10105. 4. F. Fang, Z. Chen, D. Wu, H. Liu, C. Dong, Y. Song, D. Sun, J. Power Sources. 427 (2019) 145. 5. J. Zhang, V. Charbonnier, N. Madern, J. Monnier, M. Latroche, J. Alloys Compounds 852 (2021) 157008.

D.7.2
14:45
Authors : C. Milanese*, I. Frosi, A. Papetti, A. Girella, S. Puoti, G. Magnani, D. Pontiroli, M. Riccò
Affiliations : Pavia Hydrogen Lab, C.S.G.I. & Dipartimento di Chimica, Università di Pavia, Viale Taramelli 16, I-27100, Pavia, Italy; Pavia FoodLab, Dipartimento di Scienze del Farmaco, Università di Pavia, Viale Taramelli 12, I-27100, Pavia, Italy; Nanocarbon Laboratory, DSMFI, Università di Parma, Parco Area delle Scienze 7/a, I-43124, Parma, Italy

Resume : Recently biochar, the carbon side-product in the pyrolysis/gasification of residual waste biomasses, started to receive a widespread attention in the field of the electrical energy-storage, thanks to its hierarchical porous structure inherited from biomass precursors, its excellent chemical and electrochemical stability, high conductivity, high surface area and inexpensiveness. In particular, biochar converted to activated carbon (SSA > 1000m2/g) through a chemical activation with KOH appears now to be a new cost-effective and environmentally-friendly carbon material with great application prospect in the field of energy-storage applications. We report here on the preparation of novel hierarchically-porous super-activated carbon materials originating from biochar derived by the pyrolysis of poultry litter (PL) and of rice bran. The chemical activation process proved to be efficient to remove the majority of impurities other than carbon, stabilizing highly porous hierarchical structures with local graphene-like morphology. The porous compound obtained by PL demonstrated to behave as an excellent electrode material for high-performance symmetric supercapacitors (SCs), reaching high specific capacitance up to 230 F/g. On the contrary, the compound obtained by rice bran shows a very good hydrogen storage ability, adsorbing up to 3.5 wt % of hydrogen in around 20 seconds at -196°C and 6 bar and around 1.5 wt% at room temperature. Work is in progress to optimize the pyrolysis and activation conditions and to improve the performance of the materials by decoration with transition metals. The availability, the biocompatibility and the inexpensiveness of the starting materials suggest possible large-scale applications for such devices, for example in the field of transportation or in renewable energy-grids, but also in the field of bio-medicine.

D.7.3
15:00
Authors : Paul Jerabek, Sally Brooker
Affiliations : Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon, Geesthacht, Germany; Department of Chemistry, University of Otago, Dunedin, New Zealand

Resume : Motivated by a funding initiative by the Federal Ministry of Education and Research (BMBF) to develop and strengthen scientific collaborations between German institutions with partners within the Asian-Pacific Research Area (APRA) on the topic of green hydrogen, a large research consortium consisting of academic and industrial partners from New Zealand (NZ) and Germany was successfully brought together to establish and participate in the first jointly operated German-New Zealand Green Hydrogen Research Center. 80% of NZ’s electric energy already comes from renewables (i.e. hydro, wind, solar), which from a German perspective makes it a prime partner country to develop, field-test and upscale green hydrogen technologies. The center will be set up at the University of Otago in Dunedin, located in the southern part of NZ, and consists of laboratories, offices and seminar venues and will host partners from both countries to enable the study of generation, storage and utilization of green hydrogen from as many angles as possible. This presentation will introduce you to NZ’s massive potential for green hydrogen technologies, the members and the structure of the joint research center, the research activities and the future plans extending the scope of the collaborative project.

D.7.4
15:15
Authors : Javier García-Ben(a), Jorge Salgado-Beceiro(a), Ignacio Delgado-Ferreiro(a), Antonio Luis Llamas-Saiz(b), Jorge López-Beceiro(c), Ramón Artiaga(c), Alberto García-Fernández(d), UB Cappel(d), Bruno Alonso(e), Socorro Castro-García(a), Manuel Sánchez-Andújar(a), María Antonia Señarís-Rodríguez(a) and Juan Manuel Bermúdez-García(a).
Affiliations : (a) University of A Coruna, QuiMolMat Group, Dpt. Chemistry, Faculty of Science and Advanced Scientific Research Center (CICA), Zapateira, 15071 A Coruña, Spain. E-mail: j.bermudez@udc.es, m.andujar@udc.es (b) RIAIDT X-ray Unit, Universidade de Santiago de Compostela,15782 Santiago de Compostela, Spain. (c) Department of Naval and Industrial Engineering, Esteiro, University of A Coruna, 15471 Ferrol, Spain. (d) Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden. (e) ICGM, CNRS, Universitéde Montpellier, ENSCM, 34095 Montpellier Cedex 5, France.

Resume : Phase change materials (PCMs) have attracted great interest due to their capability for the storage of thermal energy, which substantially contribute to the efficient use and conservation of residual heat and solar energy. Taking into account different thermal parameters (such as phase transition temperature, latent heat, specific heat, among others) PCMs can be used to store heat and/or “cold”. Accordingly, and depending on these parameters, PCMs can be used in a wide variety of applications: from heating buildings to cooling medical containers for transportation of blood or organs.[1] Nowadays, the most commonly used PCMs (such as eutectic water-salt solutions, hydrated salts, paraffins, fatty acids and clathrates) are these with a solid-liquid phase transition (melting) with a large latent heat. However, solid-liquid PCMs have some important drawbacks, such as volume shrinkage and leakage, which pose significant technological challenges.[2] Therefore, solid-solid PCMs are emerging as a very attractive alternative to solid-liquid PCMs because solids they significantly reduce the expansion and leakage problems. In this context, plastic crystals (PC), which are crystalline compound composed of weakly interacting molecules that possess some orientational or conformational degree of freedom, are emerging as attractive materials due to their potential applications in different fields, such as electric, caloric and optic.[3][4][5] Along the last years, PC have been intensively studied for thermal energy storage applications due to their typical first-order transition with large latent heat, which is associated with order-disorder transitions in their ions or molecules. However, most of these compounds operate near room temperature, and they are not used for “cold storage” applications, which traditionally requires operating temperatures well-below 293 K. In this work, we focus on the n-dibutylammonium tetrafluoroborate plastic crystal, which displays several solid-solid phase transitions in the range of 269 - 282 K, with the thermodynamic properties suitable for “cold storage”. From the structural point of view, this compound is very complex with several polymorphs as a function of temperature. These crystal structures were determined by using variable-temperature single crystal and powder X-ray diffraction, as well as NMR spectroscopy. The thermal analysis was carried out differential scanning calorimetry (DSC) and thermal gravimetric analyzer (TGA). Finally, the obtained results are compared with those of the principal PCMs used for “cold storage”, which up-to-date are only solid-liquid PCMs. References: [1] E. Oró et al, Appl. Energy, 2012, 99, 513. [2] H. Mehling el al, Heat and cold storage with PCM, 2008. [3] S. Santos-Moreno et al, Materials, 2020, 13, 1162. [4] B. Liu et al, Nat. Commun., 2014, 5, 3092. [5] J. Harada et al, J. Am. Chem. Soc., 2019, 141(23), 9349.

D.7.5
15:30 Q&A    
15:45 Break    
 
Session 8: How computational methods improve hydride-based materials : Hujun Cao
16:30
Authors : Zbigniew Łodziana
Affiliations : INP, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31342 Kraków, Poland

Resume : Energy storage in solids in the form of hydrogen or electrochemical reactions is still considered as safe method. The ultimate materials for this purpose remain unknown. Metal hydrides and complex metal hydrides may serve both purposes and these with favorable thermodynamic and kinetic properties are researched. That are metal hydrides resistant to hydrogen contamination not constituting any environmental hazards or solid state electrolytes with electrochemical stability window appropriate for Li or Na secondary batteries. The theoretical investigations are contributing to the research over the last decades. This is especially vital for development of new materials and manipulations on the atomic level, where methods based on quantum mechanics approach have established position. We summarize theoretical developments for the equilibrium properties of hydride crystalline materials, their equilibrium surface structures with an example of LiNi5, ZrV2 and TiFe alloys. The electrochemical stability of closo and nido borates of Li and Na is confronted with experimental evidence.

D.8.1
17:00
Authors : Neves, A. M. (1, 2), Puszkiel, J. (2,3), Capurso, G. (2), Bellosta von Colbe, J. M. (2), Milanese, C. (4), Dornheim, M. (2), Klassen, T. (1, 2), Jepsen, J. (1, 2)
Affiliations : (1) Helmut Schmidt University (HSU), University of the Federal Armed Forces, Holstenhofweg 85, 22043 Hamburg, Germany; (2) Helmholtz-Zentrum Hereon, Institute of Hydrogen Technology, Max-Plank-Str. 1, 21502 Geesthacht, Germany; (3) IREC Catalonia Institute for Energy Research, 08930, Sant Adrià de Besòs, Barcelona, Spain; (4) Pavia H2 Lab, C.S.G.I. & Department of Chemistry, Physical Chemistry Section, University of Pavia, 27100 Pavia, Italy;

Resume : The so-called Lithium Reactive Hydride Composite (Li RHC) (2 LiH + MgB2 / 2 LiBH4 + MgH2) is a high-temperature material that can be considered a suitable candidate for hydrogen storage in solids. This work aims to develop a kinetic model of the Li RHC absorption reaction. For such a purpose, thermodynamic and kinetic investigations on the system were performed. Based on the thermodynamic assessment for the absorption reaction, the system’s enthalpy ∆H and entropy ∆S were determined to be 34 ± 2 kJ∙mol H2 1 and 70 ± 3 J∙K 1∙mol H2 1, respectively. The kinetic investigations performed between 325 °C and 412 °C and between 15 and 50 bar reveal that the system’s hydrogen absorption can be modeled as having a one-dimensional interface-controlled reaction with an apparent activation energy of 146 ± 3 kJ∙mol H2 1. Applying the model, the reaction rate can be calculated as a function of the reacted fraction as well as the pressure and temperature conditions. The development of such a model allows its use in the finite element method (FEM) simulations for an optimized design of hydrogen storage systems.

D.8.2
17:15
Authors : Maximilian Passing, Claudio Pistidda, Giovanni Capurso, Olliver Metz, Julian Jepsen, Thomas Klassen, Martin Dornheim
Affiliations : Institute of Hydrogen Technology, Helmholtz-Zentrum hereon GmbH, Max-Planck-Straße 1, D-21502 Geestacht, Germany

Resume : The necessity to store energy in large quantities will increase significantly in the future, due to the larger fraction that is going to be generated from renewable sources, which are only intermittently available. To store heat at high temperature levels, which is needed for concentrated solar power plants, molten salts are commonly used, owing to their low material costs. However, they are required in large quantities and this still impact the overall cost of the plant. Using thermo-chemical energy storage systems instead, can overcome this disadvantage, by having very high energy densities that makes much less material necessary. Metal hydride systems are very promising, due to the stable capability, the high reaction enthalpies and the good controllability, by simply regulating the hydrogen pressure. [1] It has already been demonstrated by Paskevicius et al. [2], that the MgH2 system can reversibly store heat at high temperatures for different operation scenarios. A more cost effective possibility is to use the hydrogenation of recycled Mg waste as thermochemical energy storage. Due to its high reaction enthalpy, the moderate pressure and appropriate temperature conditions, the broad abundance and the recyclability, the Mg/Al alloy is perfectly suitable for this purpose. Following a previous publication of Hardian et al. [3], in which the performance of recycled Mg/Al waste is presented, an extensive kinetic reaction model for hydro- and dehydrogenation is derived in the presented work. Temperature and pressure dependencies are determined, as well as the rate limiting step of the reaction using the reduced time method. First, experiments are carried out in an autoclave with a medium scale powder mass; by varying the temperatures conditions for absorption and desorption, the thermal behavior of the larger powder batch could be investigated systematically. This specific system is simulated by the finite element method, which proves the resilience of the derived reaction model. Based on this model, the behavior of large powder masses can be thoroughly predicted so that new systems can be designed for future thermochemical energy storage applications. [1] K. Manickam, P. Mistry, G. Walker, D. Grant, C. E. Buckley, T. D. Humphries, M. Paskevicius, T. Jensen, R. Albert, K. Peinecke, M. Felderhoff, International Journal of Hydrogen Energy 2019, 44 (15), 7738 – 7745. DOI: https://doi.org/10.1016/j.ijhydene.2018.12.011 [2] M. Paskevicius, D. A. Sheppard, K. Williamson, C. E. Buckley, Energy 2015, 88, 469 – 477. DOI: https://doi.org/10.1016/j.energy.2015.05.068 [3] R. Hardian, C. Pistidda, A.-L. Chaudhary, G. Capurso, G. Gizer, H. Cao, C. Milanese, A. Girella, A. Santoru, D. Yigit, H. Dieringa, K. U. Kainer, T. Klassen, M. Dornheim, International Journal of Hydrogen Energy 2018, 43 (34), 16738 – 16748. DOI: https://doi.org/10.1016/j.ijhydene.2017.12.014

D.8.3
17:30
Authors : Archa Santhosh (1), Nathan Keilbart (2), ShinYoung Kang (2), Martin Dornheim (1), Paul Jerabek (1)
Affiliations : (1) Institute of Hydrogen Technology, Helmholtz-Zentrum hereon GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany (2) Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, CA 94551, USA

Resume : TiFe intermetallic has been widely known for its preferable hydrogen storage properties near ambient conditions. As a stationary hydrogen storage material, it can store upto 1.9 wt% of hydrogen and offer a stable and safe medium for practical usage. The foremost difficulty in achieving its full potential is the surface oxidation that hinders hydrogen absorption and reversibility. Plenty of research have been carried out focusing on the activation of the material towards hydrogen storage. Even so, the mechanism of oxidation remains unclear. In this work, we attempt to elucidate the nature of the metal surface upon oxidation and how it affects the hydrogenation with a multifaceted modelling approach. The equilibrium crystal shape of TiFe is predicted and the dissociation and diffusion of hydrogen through a few layers of oxide on the lowest energy surface is discussed in detail. We were able to gain atomistic level insights into the oxidized surface and interfaces from Density Functional Theory (DFT) whilst machine learning based methods aided to further expand the study. The work also demonstrates the significance of integrating multiple modelling methods in material research.

D.8.4
18:00 Q&A    
 
Poster Session : Zbigniew ŁODZIANA
18:15
Authors : Edgar Bautista(a), Marie Guignard(a), Jérémie Auvergniot(b), Liang Zhu(b) and Claude Delmas(a)
Affiliations : (a) CNRS, Bordeaux University, Bordeaux INP, ICMCB UMR 5026, F-33600 Pessac, France (b) Umicore, Rechargeable Battery Materials, 31 rue du marais, Brussels BE-1000, Belgium

Resume : All car manufacturers for electrical vehicles consider Ni-rich based positive electrode materials. They exhibit very good electrochemical performances. Nevertheless, if the cells are cycled at high voltage, to increase their capacity, a significant decrease of the performance is observed upon cycling. Therefore, the goal of the research consists in improving the lifetime of the cells. In the literature, this behavior is attributed to: (i) the instability of Ni4+ ions that are formed at the end of charge, (ii) the formation of cracks due to the large change in the unit cell volume when a too large amount of lithium is deintercalated. Most of the researches consist in: (i) optimizing the material electrode morphology to prevent the internal constraints, (ii) improving the material stability at high voltage by cationic substitution and/or foreign cation doping. In order to try to have a better understanding of the real electrochemical mechanism occurring at high voltage a very detailed study of the behavior of the cycling of the LiNiO2 parent material was done. In fact, the real formula of this layered material is Li1-zNi1+zO2 (z > 0.01). This deviation from their ideal stoichiometry result from the instability of Ni3+ ions at the synthesis temperature, which leads to the presence of the extra-nickel ions in the Li layer. This departure from the ideal stoichiometry has a dramatic effect on the cell capacity if z > 0.02. The synthesis of the pristine phase was done in optimized conditions (oxygen flow, 700°C). The Rietveld refinement of the XRD pattern and a magnetic study confirmed that the Li0.99Ni1.01O2 composition was obtained. This material was used in Li coin cells which were cycled in various conditions. After a first charge to 4.0V (4.2V, 4.3V respectively) several cycles were done in the 4.0V-3.8V range (4.2V-3.8V, 4.3V-3.8V respectively). Then for all experiments, a final discharge was done to 3.0 V in GITT conditions to intercalate as much lithium as possible. When the cell is cycled up to 4.0V the shape of the cycling curve is normal. On the contrary, for the higher voltage values, at the very beginning of the discharge there is an unexpected lower shoot, which increases with the number of cycles and the charge voltage cutoff. This is an evidence of an increase of the cell impedance due to the formation of an insulating layer, which starts to be formed at 4.2V. This leads to lower charge capacity on the high voltage plateau. Our experiments show that this behavior disappears if the charge is limited to 4.15V. At low voltage, around 3. 6V, for all Ni-rich materials, there is also a capacity loss, even at the first cycle that corresponds to 20% of the expected capacity. GITT experiments have shown that this limitation is due a kinetic problem. During the full discharge, our experiments show that the capacity loss at low voltage increases when the cycling is performed at high voltage. This indicates that both phenomena are linked.

D.P2.1
18:15
Authors : Aurelia Gries, Frederieke Langer, Julian Schwenzel
Affiliations : Fraunhofer IFAM, Germany

Resume : Solid-state electrolytes offer advantages over conventional liquid electrolytes, like the possibility of constructing batteries in bipolar stacks and greater safety, e.g. because they cannot leak. One promising material group are sulfides, among which beta-Li3PS4 gathered much attention in the last years due to its good ionic conductivity and scalable synthesis route. Several studies determined the ionic conductivity, but the reported conductivity values scatter. Possible origins might be varying synthesis and measurement conditions. Therefore, a standardised measurement protocol is needed to gain comparable data. First attempts to identify influences of the measurement conditions on the obtained ionic conductivity of thiophosphate-based sulfides were made by Ohno et al. 2020 [1], in which an interlaboratory study was performed, and Doux et al. 2020 [2], who examined pressure effects. This work investigates effects of different electrode materials on the obtained data from electrochemical impedance spectroscopy (EIS) of beta-Li3PS4 under controlled measurement conditions. Beta-Li3PS4 was synthesised via wet-chemical synthesis in THF. The as-synthesized material was used to produce pellets in a standardised way in order to rule out preparation effects. A variety of common electrode materials was applied to perform impedance measurements. The choice of electrode material showed effects on the variance of the obtained data. [1] S. Ohno et al., ACS Energy Letters 2020 5 (3), 910-915; DOI: 10.1021/acsenergylett.9b02764 [2] J.-M. Doux et al., J. Mater. Chem. A, 2020,8, 5049-5055; DOI: 10.1039/C9TA12889A

D.P2.2
18:15
Authors : Ignacio Delgado-Ferreiro, Jorge Salgado-Beceiro, Javier García-Ben, Socorro Castro-García, María Antonia Señarís-Rodríguez, Manuel Sánchez-Andújar, and Juan Manuel Bermúdez-García
Affiliations : University of A Coruna, QuiMolMat Group, Dpt. Chemistry, Faculty of Science and Advanced Scientific Research Center (CICA), Zapateira, 15071 A Coruña, Spain.

Resume : In the last decades, organic plastic crystals (mainly polyalcohols) have been widely studied for thermal energy storage applications due to their extremely large thermal changes induced by modifications in the ambient temperature.[1] However, these materials exhibit some limitations and drawbacks, such as flammability, relatively low thermal stability and low density (which also reduces the density of stored energy). In the search for new plastic crystals with enhanced thermal properties, we focus on hybrid plastic crystals with general formula [A][FeCl4] (where A = organic cations). These materials have recently exhibited functional properties, of interest for different technological applications, such as magnetic or dielectric order and even thermal energy storage.[2] In the present work, we found that this emerging family can exhibit very large thermal changes that can be induced by thermal energy from sunlight, with charging and discharging temperatures suitable for domestic applications.[3] Moreover, these compounds are not flammable and they exhibit larger thermal stability than the traditional polyalcoholic plastic crystals. Interestingly, this specific combination of organic cations and inorganic anions leads towards antiferroelectric structures that can largely change their dielectric capacity when increasing the temperature. As a matter of fact, these materials can increase their electric energy capacity up to five times when the charging temperature is surpassed, and later release this energy when the discharging temperature is reached. In summary, the [A][FeCl4] plastic crystals materials here reported arise as a promising family of compounds that can simultaneously store multiple thermal and electric energy just by using the solar thermal energy, and use the store energy for domestic applications. [1] (a) J. Font et al., Sol. Energy Mater., 1987, 15, 299-310; (b) M. Barrio et al., Sol. Energy Mater., 1988, 18, 109-115. [2] (a) P. González-Izquierdo et al., J. Mater. Chem. C, 2021, 9, 4453-4465; (b) D. Li et al., Inorg. Chem., 2019, 58, 655-662. [3] J. Salgado-Beceiro et al., J. Mater. Chem. C, 2020, 8, 13686–13694.

D.P2.3
18:15
Authors : Jong Ho Won
Affiliations : Department of Chemistry, Kookmin University, 77 Jeongneung-ro, Seongbuk-gu, Seoul 02707, Republic of Korea

Resume : Nitrogen-rich carbon materials have advantageous properties to be applied to energy research compared to general carbon materials. Nitrogen-rich carbon materials are more suitable for hybridization with transition metals than pristine carbon, and help transition metal active materials to be tuned to nano size. In addition, it can show better compatibility with various substances such as electrolytes or working solutions. Therefore, many existing studies have attempted to impart nitrogen to carbon materials. In general, carbon materials used in research are made through carbonization, and nitrogen-rich carbon materials can be made by using precursors that contain both carbon and nitrogen (melamine, urea, etc.). Also, physical doping using plasma or gas doping using ammonia is also used. We have discovered, through an entirely new method, a process for imparting nitrogen to a carbon material through a polymer that is completely removed during the experiment. In addition, we have developed a method for attaching various and complex nitrogen functional groups as well as nitrogen molecules depending on the type of polymer used. This method is composed of mixing a polymer having a specific functional group with the original carbon material and then completely removing the polymer through heat treatment under a mild vacuum. At this time, the degree of polymerization of the polymer has an effect on the attachment of nitrogen and functional groups. If the degree of polymerization is too high, additional carbonization of the polymer proceeds, and an undesired amorphous carbon structure is added to the original structure. In addition, if the degree of polymerization is too low, the polymer evaporates too quickly, so that nitrogen and functional groups can't be effectively imparted to the original structure. We found through experiments and analysis the appropriate degree of polymerization that can give nitrogen and functional groups to carbon. Additionally, we used a carbon structure including nitrogen and functional groups as an electrode of an organic electrolyte-based capacitor. The carbon structure containing nitrogen showed superior capacity and lifetime performance compared to the general carbon structure, and these results were attributed to the improvement of solvent affinity and conductivity by nitrogen addition. In addition, using a carbon electrode with various nitrogen functional groups to the capacitor, unique experimental results were obtained according to the change in surface energy and physical properties. In this study, we introduce a method to easily attach nitrogen and nitrogen functional groups to carbon materials, and include excellent electrochemical test results used the materials of the developed method. The result is mainly explained by the change in surface energy due to the participation of nitrogen in the carbon structure. This new method is expected to be applied in various fields of energy research, including energy storage.

D.P2.4
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10:30 Q&A / Closing Remarks    
 
Session 9: Materials for Solar Thermal Energy Storage : Sebastiano Garroni
14:00
Authors : Kasper T. Møller, Terry D. Humphries, Mark Paskevicius, Craig Buckley
Affiliations : Department of Biological and Chemical Engineering, Aarhus University, Aabogade 40, Aarhus, DK-8200, Denmark Department of Imaging and Applied Physics, Fuels and Energy Technology Institute, Curtin University, GPO Box U1987, Perth 6845, WA, Australia

Resume : As the price of renewable energy, e.g. sun and wind power, increasingly becomes competitive with fossil fuels, the main hurdle to overcome in the green transition is the storage of renewable energy to even out the intermittent energy production from these sources [1]. Metal carbonates have great potential as thermochemical energy storage materials through the endo- and exothermic release and uptake of CO2 with low cost and high energy density [2]. However, the major challenge is the loss of CO2 storage capacity, i.e. energy storage capacity, which drastically decreases over multiple cycles [3, 4]. Our recent research has highlighted multiple ways to significantly improve the cyclic stability and reaction kinetics of metal carbonates, e.g. by the addition of a molten salt catalyst [2], changing reaction pathway/thermodynamics by adding a metal orthosilicate [5], or by the formation of ternary metal oxide compounds [6]. A range of compounds operating in different temperature intervals have been investigated, i.e. dolomite, CaMg(CO3)2 at 550 °C, BaCO3 at 850 °C, and CaCO3 at 900 °C, and have been operated in energy storage and release cycles. The most promising system so far is the CaCO3-Al2O3 (20 wt%), which was cycled 500 times with a 90% energy capacity retention and has a cost of ~ 0.7 USD/kWh (materials-basis only) [6]. This presentation will give an overview of current research and an outline of future perspectives on thermochemical energy storage. References [1] International Renewable Energy Agency (IRENA), “Renewable Power Generation Costs in 2017: Key Findings and Executive Summary.” [2] T. Humphries, K. T. Møller, et al., J. Mater. Chem. A, 2019, 7, 1206. [3] G. S. Grasa, J. C. Abanades, Ind. Eng. Chem. Res. 2006, 45, 26, 8846. [4] J. Abanades, D. Alvarez, Energy Fuels 2003, 17, 2, 308. [5] K. T. Møller, et al., J. Mater. Chem. A, 2019, 8, 10935. [6] K. T. Møller, et al., J. Mater. Chem. A, 2019, 8, 9646.

D.9.1
14:30
Authors : Adriana Pires Vieira, Kyran Williamson, Terry D. Humphries, Mark Paskevicius, Craig E. Buckley
Affiliations : Fuels and Energy Technology Institute, Curtin University, Perth, WA 6845

Resume : Stable power generation from renewable energy requires the development of new materials that can be used for energy storage. A new reactive carbonate composite (RCC) based on SrCO3 is proposed as a material with high energy density for thermochemical energy storage. SrCO3-SrSiO3 can promote the thermodynamic destabilisation of SrCO3, making its operating temperature (700 °C) more suitable for concentrated solar thermal power applications. Utilising a eutectic mixture of salts as a catalyst, the reversible carbonation reaction achieves cycle stability of approximately 80% of efficiency over multiple cycles. The high volumetric (1878 MJ m-3) and gravimetric energy density (500 kJ kg-1) of the RCC, allows a compact thermal battery to be developed. Additionally, the low cost of SrCO3 makes the RCC a highly competitive alternative energy storage material in term of cost and efficiency when compared to existing molten salt based energy storage technology. Its cost-benefit is 60% cheaper than the molten salts currently used in concentrated solar thermal power application on a materials basis. A thermochemical energy storage system based on SrCO3-SrSiO3 requires a small footprint, which is essential for remote areas. It is also compatible with the Rankine-Brayton combined cycle and with a Stirling engine for thermal to electrical energy conversion and can be adapted for another renewable energy form such as photovoltaics and wind farms.

D.9.2
14:45
Authors : Mazur, N.*(1), Huinink, H.(1), Fischer, H.(2), Adan, O.(1,2).
Affiliations : (1) Eindhoven University of Technology, The Netherlands; (2) TNO Materials Solutions, The Netherlands;

Resume : From hundreds of salts that have been considered for thermochemical heat storage, potassium carbonate (PC) has been selected as a promising candidate [1]. The main disadvantage of this compound, as well as of several other salts, is the large hysteresis between hydration and dehydration. This undesirable behaviour lowers the power output and limits the operating window of the material. Recent work showed that this hysteresis can be caused by multistep reaction processes mediated by a wetting layer on the surface of the salt [2]. Ionic mobility within that wetting layer is limited in a metastable zone around equilibrium conditions. Considering this, we have developed an approach that enhances the power output of PC by mixing it with another salt hydrate. This method makes use of deliquescence, which promotes mobility in the wetting layer. Our work shows that the power output can be tripled by mixing PC with a salt hydrate with a low deliquescence point depending on the reaction conditions. By testing a multitude of salt mixtures, we have developed an approach that helps in selecting a suitable additive for other salt hydrates that suffer from similar metastable behaviour. [1] Donkers, P.A.J., et al. "A review of salt hydrates for seasonal heat storage in domestic applications." Applied energy 199 (2017): 45-68. [2] Sögütoglu, L.C., et al. "Understanding the hydration process of salts: the impact of a nucleation barrier." Crystal Growth & Design 19.4 (2019): 2279-2288.

D.9.3
15:00
Authors : Joey Aarts, Stan de Jong, Martina Cotti, Pim Donkers, Hartmut Fischer, Olaf Adan, Henk Huinink
Affiliations : Eindhoven University of Technology, Eindhoven University of Technology, Eindhoven University of Technology, TNO, TNO, TNO, Eindhoven University of Technology

Resume : Potassium carbonate is a promising salt for thermochemical heat storage. For an application mm-sized salt hydrate particles are manufactured to be loaded inside a reactor. The step towards larger particles is necessary to prevent a large pressure drop over the reactor bed during hydration/ dehydration in a given air flow. Even though the performance of a single salt hydrate mm-sized particle is one of the key aspects in the application, its kinetics has not yet been extensively investigated. Therefore, in this work a systematic study on the hydration kinetics of mm-sized disc shaped salt hydrate (K2CO3) particles is presented for the first time. The effect of density, primary particle size and driving force on the hydration kinetics could be evaluated using a 1D diffusion model based on a shrinking core assumption. In this approach the overall reaction is limited by the diffusion of reactant towards the reaction front. The particle internal structure and powder kinetics are investigated to estimate the reaction front width. It is found that the particle density (porosity) greatly affects the hydration rate. The kinetic behavior is found to be independent of the primary powder size. Additionally, the effect of driving force is studied. The calculated transport mechanism is unaffected by changes in driving force whereas the power output is. The main conclusions are that the hydration kinetics of mm-sized salt hydrate particles is diffusion limited and that the particle density (porosity) is the main parameter controlling its performance. The results from this work can be used to predict kinetic behavior of particles with other generic shapes (2D and 3D). Since the particle hydration is expected to be similar for different salts, given the powder reaction rate constant is high enough, the model from this work can possibly be used to predict and optimize particles made from different salts as well. Therefore, this work provides input for designing future salt hydrate particles for thermochemical heat storage using various combinations of salts and particle shapes.

D.9.4
15:15
Authors : Sruthy Balakrishnan1*, Terry D. Humphries1, Mark Paskevicius1, M. Veronica Sofianos1, 2 and Craig E. Buckley1
Affiliations : 1.Physics and Astronomy, Fuels and Energy Technology Institute, Curtin University, GPO Box U1987, Perth, WA 6845, Australia 2. University College Dublin, School of Chemical and Bioprocess Engineering, Belfield, Dublin 4, Ireland

Resume : The unique advantage of concentrated solar power (CSP) plants implemented with thermal energy storage (TES) is their ability to store the solar heat generated during the daytime to produce electricity at night. Therefore, the future of this technology relies on the identification and development of cost-effective TES materials. The aim for next-generation CSP plants is to develop a TES material that can operate above 600 °C, increasing the overall energy efficiency of the plant. Metal hydrides, which can reversibly store heat via chemical reactions, have been identified as a potential next-generation TES material by the US Department of Energy as part of the SunShot research programme [1]. Calcium hydride is a promising high-temperature metal hydride due to its low operating hydrogen pressure at high temperature (1 − 5 bar at 1100 – 1400 °C) and high gravimetric (4939 kJ/kg) and volumetric energy densities (8396 MJ/m3) [2]. The melting point of both calcium hydride and calcium metal are 816 °C and 842 °C, respectively. The corrosive nature of molten calcium hydride at high temperature requires expensive containment tank materials [3]. The best solution to avoid these difficulties is to reduce the decomposition temperature of pure calcium hydride. Thermodynamic destabilization of calcium hydride, using suitable additives, is one approach for reducing the decomposition temperature of calcium hydride, transforming it into a suitable TES material for next generation CSP plants. The novelty of this study lies in the selection of relatively inexpensive and abundant materials such as aluminium oxide and zinc to be used as additives to reduce the decomposition temperature of calcium hydride. It has been demonstrated that adding aluminium oxide or zinc to calcium hydride, reduces the hydrogen equilibrium pressure (1 bar) from 1100 °C to 636 °C and 597 °C, respectively [4, 5]. This study provides an overview of the thermodynamic destabilisation of calcium hydride including thermodynamic and kinetic measurements, synthesis, characterisation and thermal analysis. The cost calculation and cycling stability of each system has been studied to check the feasibility of using the materials as a thermal battery for CSP applications. References 1. US Department of Energy, D.O.E. Sunshot Vision Study. https://www.energy.gov/eere/solar/sunshot-initiative. access date-09/06/2020. 2. Manickam, K., et al., Future perspectives of thermal energy storage with metal hydrides. International Journal of Hydrogen Energy, 2019. 44(15): p. 7738-7745. 3. Peterson, D. and V. Fattore, calcium-calcium hydride phase system1. The Journal of Physical Chemistry, 1961. 65(11): p. 2062-2064. 4. Balakrishnan, s., et al., Destabilised Calcium Hydride as a Promising High-Temperature Thermal Battery. The Journal of Physical Chemistry C, 2020, 124, 32, 17512- 17519. 5. Balakrishnan, S., et al., Thermochemical energy storage performance of zinc destabilized calcium hydride at high-temperatures. Physical Chemistry Chemical Physics, 2020. 22(44): p. 25780-25788.

D.9.5
15:30
Authors : K. Williamson(1), A.P. Vieira(1), K.T. Møller(1)(2), M. Paskevicius(1), C.E. Buckley(1)
Affiliations : (1)Department of Physics and Astronomy, Fuels and Technology Institute, Curtin University, Australia ; (2) Department of Biological and Chemical Engineering, Aarhus University, Aabogade 40, Aarhus, DK-8200, Denmark

Resume : The intermittent nature of renewable energy is a major challenge that can be overcome via cheap, effective energy storage[1]. Thermochemical energy storage is an upcoming technology that can improve efficiency and lower cost in applications such as concentrated solar power[1]. Metal carbonates have great potential as thermochemical energy storage materials through the reversible endo/exothermic desorb/absorption of carbon dioxide (CO₂)[2]. However, the major challenges include the loss of cyclic capacity and slow kinetics[3]. Previously, it has been established that barium carbonate (BaCO₃) can be thermodynamically destabilised by the addition of barium silicate (BaSiO₃)[4]. This lowers the operating temperature from ~1400 °C to 850 °C to allow operation with second-generation concentrated solar power plants. Moreover, the addition of a calcium carbonate (CaCO₃) catalyst improves kinetics by an order of magnitude [4]. This research explores the reactions of barium carbonate combined with various metal oxides, for example, iron (III) oxide (Fe₂O₃) or titanium (IV) oxide (TiO₂). This reduces the operating temperature from 1400 °C to 875 °C and 1050 °C respectively and improves reaction kinetics of carbon dioxide release and uptake. The performance of barium carbonate with titanium oxide is especially promising, as it shows minimal (~5 %) capacity loss over 75 cycles. This presentation will summarise current research and explore future directions. [1] Paskevicius, M.; Sheppard, D. A.; Williamson, K.; Buckley, C. E. Metal Hydride Thermal Heat Storage Prototype for Concentrating Solar Thermal Power. Energy 2015, 88, 469–477. https://doi.org/10.1016/j.energy.2015.05.068. [2] André, L.; Abanades, S. Evaluation and Performances Comparison of Calcium, Strontium and Barium Carbonates during Calcination/Carbonation Reactions for Solar Thermochemical Energy Storage. J. Energy Storage 2017, 13, 193–205. https://doi.org/10.1016/j.est.2017.07.014. [3] Humphries, T. D.; Møller, K. T.; Rickard, W. D. A.; Sofianos, M. V.; Liu, S.; Buckley, C. E.; Paskevicius, M. Dolomite: A Low Cost Thermochemical Energy Storage Material. J. Mater. Chem. A 2019, 7 (3), 1206–1215. https://doi.org/10.1039/C8TA07254J. [4] Møller, K. T.; Williamson, K.; Buckley, C. E.; Paskevicius, M. Thermochemical Energy Storage Properties of a Barium Based Reactive Carbonate Composite. J. Mater. Chem. A 2020, 8 (21), 10935–10942. https://doi.org/10.1039/D0TA03671D.

D.9.6
15:45 Q&A    
16:00 Break    
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Session 10: Design and Application of synthetic fuel systems : Kasper Møller
08:30
Authors : Alessandro Taras, Maria Domenica Simula, Luca Cappai, Valeria Farina, Claudio Pistidda, IakovosYakoumis, Fabiana C. Gennari, Santiago Aparicio, Stefano Enzo, Gabriele Mulas, Sebastiano Garroni
Affiliations : Alessandro Taras, Maria Domenica Simula, Luca Cappai, Valeria Farina, Stefano Enzo, Gabriele Mulas, Sebastiano Garroni. Department of Chemistry and Pharmacy, University of Sassari and INSTM, Via Vienna 2, I-07100 Sassari, Italy. Claudio Piistidda. Nanotechnology Department, Institute of Materials Research, Helmholtz-Zentrum Geesthacht Max-Planck Straße 1, Geesthacht, Germany. IakovosYakoumis. Monolithos Catalysts and Recycling Ltd, 11476 Polygono, Athens, Greece FabianaC. Gennari. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), R8402AGP, S. C. de, Bariloche, Río Negro, Argentina Santiago Aparicio. ICCRAM - Department of Chemistry, University of Burgos, 09001 Burgos, Spain

Resume : Producing green fuels from renewable electricity sources while capturing CO2 represents one of the main and fascinating challenges proposed to the scientific community for drastically reducing the even increasing level of the global warming gas CO2 and convert it into efficient and environmental friendly energy vectors. However, the direct transformation of CO2 into chemical green fuels is quite challenging due to the high stability of CO2 molecule and the relative expensive catalysts commonly used to activate most of the many processes reported in the current literature. For this reason, fervent research is still addressed to explore new and feasible ways to convert efficiently carbon dioxide by using abundant and cheap raw materials. Recently, we demonstrated how carbon dioxide can be efficiently converted to light hydrocarbons and carbonates, by mechanochemical activations of olivine, a natural and abundant mineral consisting of a solid solution of fayalite and forsterite, in presence of water. The olivine powders, once subjected to mechanical input through ball milling, react faster with water and carbon dioxide, producing hydrogen and light hydrocarbons with high degree of conversion: three order of magnitude superior than the hydrothermal approach reported in the literature. Within this context, this presentation aims to provide new insights and perspective into the study of the mechanically activated reaction between weathering olivine and carbon dioxide to form hydrogen, light hydrocarbons, and carbonates. The kinetics of gaseous products related to the in situ ball milling of olivine under carbon dioxide atmosphere will be reported, and the process efficiency compared with that of thermally activated. A detailed structural and microstructural characterization of the pre- and post-activated powders will be also presented, as well as the as-defined mechanism behind the mechanochemical process. The inferences of the here presented investigation are multiple: on the one hand, the production of light hydrocarbons (mainly methane) is significantly improved through ball milling with respect to thermal activation. On the other hand, the competitive carbonation process can represent an alternative way to fix carbon dioxide, of particular interest because able to simultaneously generate added values products for building materials.

D.10.1
09:00
Authors : V. Charbonnier, H. Enoki, K. Asano, K. Sakaki
Affiliations : National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan

Resume : In order to establish a sustainable society, hydrogen is seen as a promising energy carrier. Indeed, it is extremely light, highly energetic and does not emit greenhouse effect gases during use. But, because it is a gas, it suffers from poor volumetric energy density at ambient conditions of pressure and temperature. To overcome this problem, hydrogen can be stored in different ways: as a liquid at -253 °C, as a hydride or as a compressed gas. Among them, compressed gas is, today, the most mature technology and was chosen to store hydrogen in most Fuel Cell Vehicles (FCV). For cars, which are relatively small when compared to other FCV (such as trucks, buses or trains), get a high volumetric energy density is compulsory. Thus, hydrogen is often stored at the ultra-high pressure of 70 MPa. FCV can be filled up with 70 MPa-hydrogen in Hydrogen Refueling Stations (HRS). In these places, hydrogen is pressurized by mechanical compressors. The main drawbacks of these compressors are their cost (installation and maintenance), as well as their energy consumption. Here, we are looking for a solution that could advantageously replace mechanical compressors. Metal hydride (MH) compressors are silent, deliver high purity hydrogen and do not require frequent maintenance. In addition, they simply need heat energy to work. Thus, if this heat is provided by the waste heat of a nearby device, it might lead to a decrease in the pressurization energy consumption. A MH compressor is basically a tank containing a hydrogen storage alloy. This compound is able to absorb hydrogen at low pressure PL and low temperature TL, and, when heated at TH, it desorbs hydrogen and delivers it at higher pressure PH. In our concept, the MH compressor will be heated to TH thanks to the waste heat of nearby devices providing hydrogen (e.g. high pressure electrolyzer or electrochemical hydrogen compressor). This latter compressor delivers H2 at about 35 MPa, then the MH compressor takes over, compressing the hydrogen to 80 MPa. We are targeting a MH compressor with inlet hydrogen pressure PL = 20-30 MPa at TL = 30 °C, that would deliver hydrogen at outlet pressure PH = 80 MPa when heated at TH = 80 °C. Not only these operation pressure-temperature conditions, but also the slope of the plateau and hysteresis in the isotherms as well as the compression ratio, are important properties to consider when realizing a MH compressor. For that purpose, we are investigating various types of Ti-based hydrogen storage compounds with C14 structure. In this presentation, we would like to explain the effect of substitution on their hydrogenation properties. This work was supported by the Development of high efficiency hydrogen storage-compression-supply system by NEDO.

D.10.2
09:15
Authors : Pengyu Zhao, Tian Xie, Xinmei Xu, Hong Zhu, Fuyong Cao, Tao Ying, Xiaoqin Zeng
Affiliations : Pengyu Zhao, Tian Xie, Xinmei Xu, Hong Zhu, Tao Ying, Xiaoqin Zeng are with the Shanghai Jiao Tong University, Shanghai 200240, P.R. China. Fuyong Cao is with the Xiamen University, Xiamen 361005, P.R. China.

Resume : Magnesium (Mg) alloy are considered one of the candidates for engineering applications in the automobile and aeronautical industry, owing to their good castability and high strength-to-weight ratio (specific strength). However, the poor corrosion resistance of these alloys has significantly restricted their application in aerospace, rail transit, electronic communications and other fields. Mg is quite susceptible to corrosion due mainly to its negative potential (~2.37 VSHE) and low Pilling–Bedworth (P–B) ratio (<1). These factors are conducive for the occurrence of galvanic corrosion and hinder the formation of a protective passive film on the alloys surface. Therefore, Mg alloys are readily to corrode in humid environments. In this work, we designed a high corrosion resistant Mg-Sc-Y ternary peritectic alloys based on the first-principles calculations of density functional theory. The Mg-Sc-Y alloy is composed of the typical peritectic microstructure with cellular grains. Elemental Sc segregates (in general) into the intergranular cells and pushes Y to the surrounding areas. With the addition of Sc and Y, the difference of Volta potential and work function between intergranular cells and boundaries reduced, indicating a decrease in the driving force for corrosion. In addition, a more protective film (MgO/Mg(OH)2+Sc2O3+Y2O3) would form on the surface, which further improves the corrosion resistance of the alloy. Nevertheless, with the further increase of Y content, more micro-galvanic couples emerge, enhancing the cathodic hydrogen evolution. Therefore, the Mg-4Sc-1Y (wt.%) alloy exhibits the best corrosion resistance. The hydrogen evolution rate in 3.5wt.% NaCl solution is only 0.13ml/cm2/day, performing the same level as high-purity Mg.

D.10.3
09:30
Authors : Cappai Luca, Taras Alessandro, Simula Maria Domenica, Garroni Sebastiano, Enzo Stefano, Mulas Gabriele
Affiliations : Università degli Studi di Sassari

Resume : In order to mitigate the ever-increasing CO2 concentration in the atmosphere, new materials and sustainable approaches, part of the carbon capture utilization strategies (CCU), are required. In this context, the present work focuses on the conversion of CO2 into light hydrocarbons through photochemical activated processes on Olivine-doped system. Olivine mineral group has been selected for the high content of magnesium, high abundance in nature and low suppling cost that makes it an ideal feedstock candidate for the strategies of CO2 storage and conversion. Different materials have been investigated as dopants to obtain the optimal energy band gap for the photochemical induced conversion process. The doped materials (Olivine with TiO2, NiO, Fe3O4, Fe2O3 with a weight fraction of the dopant in the range from 1 wt % to 15 wt %) have been prepared through mechanical ball milling and characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). The energy band gaps of the prepared materials have been calculated by UV-vis absorbance measurements with the Tauc Plot method. The photocatalytic tests have been performed in a laboratory stainless steel gas reactor with quartz windows and a known amount of distilled water, under 1 bar of CO2 (99%) at room temperature. Pellet of the prepared materials have been tested for 12 h under solar light irradiation using a solar simulator with a Xenon lamp emission regulated with Air Mass filter 1.5 (A.M. 1.5). Gas chromatographic analysis performed on gasses upon solar irradiation tests, reveal methane, ethane and ethene evolution, especially on Olivine systems doped with 1 wt % of TiO2 anatase (methane evolution of 2.7(2) ∙ 104 μmol ∙ L-1). The XRD, SEM, EDX and FTIR characterization of pellet prepared through mechanical ball milling, post irradiation tests, show the absence of iron carbonates and traces of magnesium carbonates. This investigation show, for the first time by our knowledge, the effectiveness of CO2 conversion processes triggered by visible irradiation on Olivine-doped systems.

D.10.4
09:45
Authors : Lindenthal, L.*(1), Schrenk, F.(1), Popovic, J.(1), Rameshan, R.(1), Drexler, H.(1), Navratil, T.(1), Berger, T.(1) & Rameshan, C.(1).
Affiliations : (1)TU Wien, Institute of Materials Chemistry, Vienna, Austria

Resume : A very versatile class of catalyst materials that can be used for applications in (electro)chemical energy conversion are perovskite oxides. They have the general formula ABO3 and the high flexibility is due to the fact that the properties can be tuned by the choice of the cations A and B. These represent different sites in the crystal structure and either site can be occupied even by a combination of elements. This allows adapting a material to the specific catalytic problem, e.g. by doping with a catalytically highly active element. Furthermore, the stability can be tuned and highly thermally stable materials are achievable, suitable for high temperature applications. One of the reasons why perovskites excel in catalytic applications is their ability to exsolve metal nanoparticles consisting of the catalytically active doping elements, which consequently decorate the material surface. These nanoparticles are very stable towards sintering and coking due to being well socketed within the perovskite support. The catalytic ability of perovskite oxides has been demonstrated for the reverse water-gas shift reaction (rWGS), transforming CO2 and H2 to CO and H2O. This is an important reaction for energy conversion related processes. For example, CO could subsequently be used to produce fuels, effectively storing chemical energy. A very promising perovskite catalyst for this reaction was Nd0.6Ca0.4Fe0.9Co0.1O3-δ. During reaction, the Co-doped material showed exsolution of Co-nanoparticles, greatly enhancing catalytic activity. The material has been characterized with several methods, including in situ x-ray diffraction (XRD), in situ x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The composition of the material can be further tuned to the desired application, e.g. for optimized performance or lower costs (using less expensive elements). Also, the concept can be easily extended to other reaction systems such as methanol synthesis, thus directly producing a fuel. Acknowledgement: This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n° 755744 / ERC - Starting Grant TUCAS).

D.10.5
10:00
Authors : Emanuel Billeter, Zbigniew Lodziana, Andreas Borgschulte
Affiliations : Laboratory for Advanced Analytical Technologies, Empa - Swiss Federal Laboratories for Materials Science and Technology, Department of Chemistry, University of Zurich; Institute of Nuclear Physics, Polish Academy of Sciences; Laboratory for Advanced Analytical Technologies, Empa - Swiss Federal Laboratories for Materials Science and Technology, Department of Chemistry, University of Zurich

Resume : Because of its relevance in catalysis, the interaction of hydrogen with metallic surfaces is generally well studied. However, knowledge on surface properties is limited when it comes to the class of metals, which form bulk hydrides, such as titanium. Hydride surfaces have peculiar properties for their application as heterogeneous hydrogenation catalysts, e.g., they may have even less hydro-gen on the surface than their metallic counterparts resulting in lower catalytic yields. Titanium dihydride TiH2 has been recently shown to catalyze the ammonia synthesis under Haber-Bosch conditions while titanium metal shows no activity. The key to understanding the catalytic properties of hydrides is their electronic structure. The standard electron spectroscopy methods are incompatible with hydrogen pressures needed to form hydrides, therefore these kind of experiments are usually restricted to post-mortem analysis. We have developed a method to hydrogenate thin films in-situ under UHV conditions compatible with electron spectroscopy measurements. We can measure pressure-composition isotherms (pcT) of the Ti-H system by electron energy loss spectroscopy (EELS) and investigate different titanium hydrides by electron spectroscopy methods. Furthermore the UHV system allows for introduction of nitrogen gas and the study of the resulting surfaces. The findings are supported by DFT calculations of the titanium hydrogen interactions.

D.10.6
10:30 Q&A live session / Closing remarks    

Symposium organizers
Arndt REMHOFEMPA

Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland

Arndt.Remhof@empa.ch
Claudio PISTIDDAHelmholtz Zentrum Hereon

Institute of Hydrogen Technology, Max Planck Strasse 1, Geesthacht 21502, Germany

claudio.pistidda@hzg.de
Dorthe BOMHOLDT RAVNSBÆKUniversity of Southern Denmark

Department of Physics, Chemistry and Pharmacy, Campucvej 55, 5230 Odense M, Denmark

dbra@sdu.dk
Michael HEEREKarlsruhe Institute of Technology

Institute for Applied Materials - Energy Storage Systems (IAM-ESS),Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

michael.heere@kit.edu