In situ diffraction studies of phase-structural transformations in hydrogen and energy storage materials: An overview

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Impact of Surface Chemistry of Silicon Nanoparticles on the Structural and Electrochemical Properties of Si/Ni3.4Sn4 Com-posite Anode for Li-Ion Batteries

Embedding silicon nanoparticles in an intermetallic matrix is a promising strategy to produce remarkable bulk anode materials for lithium-ion (Li-ion) batteries with low potential, high electrochemical capacity and good cycling stability. These composite materials can be synthetized at a large scale using mechanical milling. However, for Si-Ni3Sn4 composites, milling also induces a chemical reaction between the two components leading to the formation of free Sn and NiSi2, which is detrimental to the performance of the electrode. To prevent this reaction, a modification of the surface chemistry of the silicon has been undertaken. Si nanoparticles coated with a surface layer of either carbon or oxide were used instead of pure silicon. The influence of the coating on the composition, (micro)structure and electrochemical properties of Si-Ni3Sn4 composites is studied and compared with that of pure Si. Si coating strongly reduces the reaction between Si and Ni3Sn4 during milling. Moreover, contrary to pure silicon, Si-coated composites have a plate-like mor-phology in which the surface-modified silicon particles are surrounded by a nanostructured, Ni3Sn4-based matrix leading to smooth potential profiles during electrochemical cycling. The chemical homogeneity of the matrix is more uniform for carbon-coated than for oxygen-coated silicon. As a consequence, different electrochemical behaviors are obtained depending on the surface chemistry, with better lithiation properties for the carbon-covered silicon able to deliver over 500 mAh/g for at least 400 cycles

Mechanochemical synthesis of pseudobinary Ti-V hydrides and their conversion reaction with Li and Na

Lithium-ion batteries (LiBs) based on insertion electrodes reach intrinsic capacity limits. Performance improvements and cost reduction require alternative reaction mechanisms and novel battery chemistries such as conversion reactions and sodium-ion batteries (NaBs), respectively. We here study the formation of Ti1-xVxH2 hydrides (0 < x < 1) and their electrochemical properties as anodes in LiBs and NaBs half-cells. Hydrides were synthesized by mechanochemistry of the metal powders under hydrogen atmosphere (PH2~ 8 MPa). For V contents below 80 at.% (x < 0.8), single-phase pseudobinary dihydride compounds Ti1-xVxH2 are formed. They crystallize in the fluorite-type structure and are highly nanostructured (crystallite size < 10 nm). Their lattice parameter decreases linearly with the V content leading to hydride destabilization. Electrochemical studies were first carried out in Li-ion half cells with full conversion between Ti1-xVxH2 hydrides and lithium. The potential of the conversion reaction can be gradually tuned with the vanadium content due to its destabilization effect. Furthermore, different paths for the conversion reaction are observed for Ti-rich (x 0.7) alloys. Na-ion half-cell measurements prove the reactivity between (V,Ti)H2 hydrides and sodium, albeit with significant kinetic limitation

Role of silicon and carbon on the structural and electrochemical properties of Si-Ni3.4_{3.4}Sn4_4-Al-C anodes for Li-ion batteries

Varying the amounts of silicon and carbon, different composites have been prepared by ball milling of Si, Ni$_{3.4}$Sn$_4$, Al and C. Silicon and carbon contents are varied from 10 to 30 wt.% Si, and 0 to 20 wt.% C. The microstructural and electrochemical properties of the composites have been investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and electrochemical galvanostatic cycling up to 1000 cycles. Impact of silicon and carbon contents on the phase occurrence, electrochemical capacity and cycle-life are compared and discussed. For C-content comprised between 9 and 13 wt.% and Si-content >= 20 wt.%, Si nanoparticles are embedded in a Ni$_{3.4}$Sn$_4$-Al-C matrix which is chemically homogeneous at the micrometric scale. For other carbon contents and low Si-amount (10 wt.%), no homogeneous matrix is formed around Si nanoparticles. When homogenous matrix is formed, both Ni$_3$Sn$_4$ and Si participate to the reversible lithiation mechanism, whereas no reaction between Ni$_3$Sn$_4$ and Li is observed for no homogenous matrix. Moreover, best cycle-life performances are obtained when Si nanoparticles are embedded in a homogenous matrix and Si-content is moderate (<= 20 wt.%). Composites with carbon in the 9-13 wt.% range and 20 wt.% silicon lead to the best balance between capacity and life duration upon cycling. This work experimentally demonstrates that embedding Si in an intermetallic/carbon matrix allows to efficiently accommodate Si volume changes on cycling to ensure long cycle-life

TiFe0.85Mn0.05 alloy produced at industrial level for a hydrogen storage plant

Moving from basic research to the implementation of hydrogen storage system based on metal hydride, the industrial production of the active material is fundamental. The alloy TiFe0.85Mn0.05 was selected as H2-carrier for a storage plant of about 50 kg of H2. In this work, a batch of 5 kg of TiFe0.85Mn0.05 alloy was synthesized at industrial level and characterized to determine the structure and phase abundance. The H2 sorption properties were investigated, performing studies on long-term cycling study and resistance to poisoning. The alloy absorbs and desorbs hydrogen between 25 bar and 1 bar at 55 °C, storing 1.0 H2 wt.%, displaying fast kinetic, good resistance to gas impurities, and storage stability over 250 cycles. The industrial production promotes the formation of a passive layer and a high amount of secondary phases, observing differences in the H2 sorption behaviour compared to samples prepared at laboratory scale. This work highlights how hydrogen sorption properties of metal hydrides are strictly related to the synthesis method

In-situ neutron diffraction during reversible deuterium loading in Ti-rich and Mn-substituted Ti(Fe,Mn)0.90 alloys

Hydrogen is an efficient energy carrier that can be produced from renewable sources, enabling the transition towards CO2-free energy. Hydrogen can be stored for a long period in the solid-state, with suitable alloys. Ti-rich TiFe0.90 compound exhibits a mild activation process for the first hydrogenation, and Ti (Fe,Mn)0.90 substituted alloys can lead to the fine tuning of equilibrium pressure as a function of the final application. In this study, the crystal structure of TiFe(0.90-x)Mnx alloys (x = 0, 0.05 and 0.10) and their deuterides has been determined by in-situ neutron diffraction, while recording Pressure-Composition Isotherms at room temperature. The investigation aims at analysing the influence of Mn for Fe substitution in Ti-rich Ti(Fe,Mn)0.90 alloys on structural properties during reversible deuterium loading, which is still unsolved and seldom explored. After activation, samples have been transferred into custom-made stainlesssteel and aluminium alloy cells used for in-situ neutron diffraction experiments during deuterium loading at ILL and ISIS neutron facilities, respectively. The study enables remarkable understanding on hydrogen storage, basic structural knowledge, and support to the industrial application of TiFe-type alloys for integrated hydrogen tank in energy storage systems by determining the volume expansion during deuteration. Furthermore, the study demonstrates that different contents of Mn do not significantly change the volumetric expansion during phase transitions, affecting only the deuterium content for the gamma phase and the cell evolution for the beta phase. The study confirms that the deuterated structures of the gamma phase upon absorption, beta and ' phase upon desorption, correspond to S.G. Cmmm, P2221 and Pm-3m, respectively.(c) 2022 Elsevier B.V. All rights reserved

Bacterial Taxa Associated with High Adherence to Mediterranean Diet in a Spanish Population

The Mediterranean diet (MD) is recognised as one of the healthiest diets worldwide and is associated with the prevention of cardiovascular and metabolic diseases, among others. Dietary habits are considered one of the strongest modulators of the gut microbiota, which seems to play a significant role in the health and disease of the host. The purpose of the present study was to evaluate interactive associations between gut microbiota composition and habitual dietary intake in 360 Spanish adults of the Obekit cohort (normal weight, overweight and obese subjects). Dietary intake and adherence to the MD tests together with faecal samples were collected from each subject. Faecal 16S rRNA sequencing was performed and checked against the dietary habits. MetagenomeSeq was the statistical tool applied to analyse at the species taxonomic level. Results from this study confirm that a strong adherence to the MD increases the population of some beneficial bacteria, improving microbiota status towards a healthier pattern. Bifidobacterium animalis is the species with the strongest association with the MD. One of the highlights is the positive association between several SCFA-producing bacteria and high adherence to the MD. In conclusion, this study shows that MD, fibre, legumes, vegetables, fruit and nuts intakes are associated with an increase in butyrate-producing taxa such as Roseburia faecis, Ruminococcus bromii and Oscillospira (Flavonifractor) plautii

Pseudo-ternary LiBH4-LiCl-P2S5 system as structurally disordered bulk electrolyte for all-solid-state lithium batteries

The properties of the mixed system LiBH4 LiCl P2S5 are studied with respect to all-solid-state batteries. The studied material undergoes an amorphization upon heating above 601C, accompanied with increased Li+ conductivity beneficial for battery electrolyte applications. The measured ionic conductivity is 10-3 Scm-1 at room temperature with an activation energy of 0.40(2) eV after amorphization. Structural analysis and characterization of the material suggest that BH4 groups and PS4 may belong to the same molecular structure, where Cl ions interplay to accommodate the structural unit. Thanks to its conductivity, ductility and electrochemical stability (up to 5 V, Au vs. Li+/Li), this new electrolyte is successfully tested in battery cells operated with a cathode material (layered TiS2, theo. capacity 239 mAh g-1) and Li anode resulting in 93% capacity retention (10 cycles) and notable cycling stability under the current density 12 mA g-1 (0.05C-rate) at 501C. Further advanced characterisation by means of operando synchrotron X-ray diffraction in transmission mode contributes explicitly to a better understanding of the (de)lithiation processes of solid-state battery electrodes operated at moderate temperatures

Pseudo-ternary LiBH4_{4}–LiCl–P2_{2}S5_{5} system as structurally disordered bulk electrolyte for all-solid-state lithium batteries

The properties of the mixed system LiBH$_{4}$–LiCl–P$_{2}$S$_{5}$ are studied with respect to all-solid-state batteries. The studied material undergoes an amorphization upon heating above 60 °C, accompanied with increased Li$^{+}$ conductivity beneficial for battery electrolyte applications. The measured ionic conductivity is ∼10$^{-3}$ S cm$^{-1}$ at room temperature with an activation energy of 0.40(2) eV after amorphization. Structural analysis and characterization of the material suggest that BH$_{4}$ groups and PS4 may belong to the same molecular structure, where Cl ions interplay to accommodate the structural unit. Thanks to its conductivity, ductility and electrochemical stability (up to 5 V, Au vs. Li$^{+}$/Li), this new electrolyte is successfully tested in battery cells operated with a cathode material (layered TiS$_{2}$, theo. capacity 239 mA h g$^{-1}$) and Li anode resulting in 93% capacity retention (10 cycles) and notable cycling stability under the current density ∼12 mA g$^{-1}$ (0.05C-rate) at 50 °C. Further advanced characterisation by means of operando synchrotron X-ray diffraction in transmission mode contributes explicitly to a better understanding of the (de)lithiation processes of solid-state battery electrodes operated at moderate temperatures

Establishing ZIF-8 as a reference material for hydrogen cryoadsorption: An interlaboratory study

Hydrogen storage by cryoadsorption on porous materials has the advantages of low material cost, safety, fast kinetics, and high cyclic stability. The further development of this technology requires reliable data on the H2 uptake of the adsorbents, however, even for activated carbons the values between different laboratories show sometimes large discrepancies. So far no reference material for hydrogen cryoadsorption is available. The metal-organic framework ZIF-8 is an ideal material possessing high thermal, chemical, and mechanical stability that reduces degradation during handling and activation. Here, we distributed ZIF-8 pellets synthesized by extrusion to 9 laboratories equipped with 15 different experimental setups including gravimetric and volumetric analyzers. The gravimetric H2 uptake of the pellets was measured at 77 K and up to 100 bar showing a high reproducibility between the different laboratories, with a small relative standard deviation of 3–4 % between pressures of 10–100 bar. The effect of operating variables like the amount of sample or analysis temperature was evaluated, remarking the calibration of devices and other correction procedures as the most significant deviation sources. Overall, the reproducible hydrogen cryoadsorption measurements indicate the robustness of the ZIF-8 pellets, which we want to propose as a reference material.M. Maiwald, J. A. Villajos, R. Balderas and M. Hirscher acknowledge the EMPIR programme from the European Union's Horizon 2020 research and innovation programme for funding. F. Cuevas and F. Couturas acknowledge support from France 2030 program under project ANR-22-PEHY-0007. D. Cazorla and A. Berenguer-Murcia thank the support by PID2021-123079OB-I00 project funded by MCIN/AEI/10.13039/501100011033, and “ERDF A way of making Europe”. K. N. Heinselman, S. Shulda and P. A. Parilla acknowledge the support from the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Hydrogen and Fuel Cell Technology Office through the HyMARC Energy Materials Network