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All-solid-state batteries are typically manufactured under high pressure to decrease the resistance of the solid interface. However, until now, there has been a lack of research concerning changes in the structure of solid electrolytes owing to pressurization. Our study addresses this gap by exploring the structural modifications of the sulfide solid electrolyte Li3PS4 under high-pressure conditions. We observed a tendency for PS4 molecules to converge upon each other in both β-Li3PS4 and g-Li3PS4 crystals when subjected to a pressure of 100 MPa. In g-Li3PS4, X-ray scattering and pair distribution function analyses following pressure application and subsequent return to ambient conditions remained consistent with pre-compression measurements. Conversely, in β-Li3PS4 crystals, post-pressure X-ray scattering differed from pre-compression measurements, suggesting pressure-induced atomic rearrangement within the crystal lattice. This underscores the importance of accounting for pressure-induced structural changes, especially in computational simulation studies where crystal structures are often assumed to remain static pre- and post-pressurization. Our findings demonstrate that under high pressure, the crystal structure of Li3PS4 slightly changes by approximately 1~2%, rendering it a viable candidate for utilization as a solid electrolyte in all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Li2S–P2S5–LiI-type solid electrolytes, such as Li4PS4I, Li7P2S8I, and Li10P3S12I, are promising candidates for anode layers in all-solid-state batteries because of their high ionic conductivity and stability toward Li anodes. However, few studies have been conducted on their detailed local structure and particle surface state. In this study, Li7P2S8I (Li2S: P2S5:LiI = 3:1:1) solid electrolytes as the chemical composition were synthesized by mechanical milling and liquid-phase shaking, and their local structures were analyzed by transmission electron microscopy. The particle surface states were analyzed by X-ray photoelectron spectroscopy, high-energy X-ray scattering measurements, and neutron total scattering experiments. The results showed that Li7P2S8I solid electrolytes are composed of nanocrystals, such as Li4PS4I, LiI, Li10P3S12I and an amorphous area as the main region, indicating that the crystalline components alone do not form ionic conductive pathways, with both the amorphous and crystalline regions contributing to the high ionic conductivity. Moreover, the ionic conductivity of the crystalline/amorphous interface of the glass-ceramic was higher than that of the Li2S–P2S5–LiI glass. Finally, an organic-solvent-derived stable surface layer, which was detected in the liquid-phase shaking sample, served as one of the factors that contributed to its high stability (which surpassed that of the mechanically milled sample) toward lithium anodes. We expect these findings to enable the effective harnessing of particle surface states to develop enhanced sulfide solid electrolytes. [ABSTRACT FROM AUTHOR]

Controlling Li ion transport in glasses at atomic and molecular levels is key to realizing all‐solid‐state batteries, a promising technology for electric vehicles. In this context, Li3PS4 glass, a promising solid electrolyte candidate, exhibits dynamic coupling between the Li+ cation mobility and the PS43− anion libration, which is commonly referred to as the paddlewheel effect. In addition, it exhibits a concerted cation diffusion effect (i.e., a cation–cation interaction), which is regarded as the essence of high Li ion transport. However, the correlation between the Li+ ions within the glass structure can only be vaguely determined, due to the limited experimental information that can be obtained. Here, this study reports that the Li ions present in glasses can be classified by evaluating their valence oscillations via Bader analysis to topologically analyze the chemical bonds. It is found that three types of Li ions are present in Li3PS4 glass, and that the more mobile Li ions (i.e., the Li3‐type ions) exhibit a characteristic correlation at relatively long distances of 4.0–5.0 Å. Furthermore, reverse Monte Carlo simulations combined with deep learning potentials that reproduce X‐ray, neutron, and electron diffraction pair distribution functions showed an increase in the number of Li3‐type ions for partially crystallized glass structures with improved Li ion transport properties. Our results show order within the disorder of the Li ion distribution in the glass by a topological analysis of their valences. Thus, considering the molecular vibrations in the glass during the evaluation of the Li ion valences is expected to lead to the development of new solid electrolytes. [ABSTRACT FROM AUTHOR]

We investigated the cross-plane thermal conductivity and boundary thermal resistance of epitaxially grown superlattice samples. These included iron vanadium aluminum alloy (Fe2VAl) and tungsten (W) or molybdenum (Mo) prepared by radio frequency magnetron sputtering. We used out-of-plane X-ray diffraction measurements to confirm the epitaxial growth of the superlattices. The superlattice with the shortest period of 1.9 nm showed satellite reflections indicating a highly ordered structure. Misfit dislocations in the 2-nm-thick Mo layer were also identified by high-resolution transmission electron microscopy. We attribute these features to the large lattice mismatch between the Fe2VAl and Mo lattices. The cross-plane thermal conductivity of the superlattice decreased as the number of interfaces increased because of thermal resistance at interlayer boundaries. A simulation of the thermal conductivity by the constant boundary resistance model reproduced the experimental data but with some deviations for samples with a smaller period (less than 20 nm). This deviation from the simulation results indicates that the phonon modes contributing to the thermal transport changed and/or the phonon scattering probability at the interfaces decreased. The superlattice of Fe2VAl/W with a period thickness greater than 20 nm had a boundary thermal resistance approximately twice as large as that of the Fe2VAl/Mo superlattice. This result provides clear evidence for the effects of the mass difference of layers on phonon scattering at an interface. [ABSTRACT FROM AUTHOR]