Hydride-based antiperovskites with soft anionic sublattices as fast alkali ionic conductors

Shenghan Gao; Thibault Broux; Susumu Fujii; Cédric Tassel; Kentaro Yamamoto; Yao Xiao; Itaru Oikawa; Hitoshi Takamura; Hiroki Ubukata; Yuki Watanabe; Kotaro Fujii; Masatomo Yashima; Akihide Kuwabara; Yoshiharu Uchimoto; Hiroshi Kageyama

doi:10.1038/s41467-020-20370-2

Hydride-based antiperovskites with soft anionic sublattices as fast alkali ionic conductors

Nat Commun. 2021 Jan 8;12(1):201. doi: 10.1038/s41467-020-20370-2.

Authors

Affiliations

¹ Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan.
² Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, 456-8587, Japan.
³ Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan. cedric@scl.kyoto-u.ac.jp.
⁴ Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan.
⁵ Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan.
⁶ Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1-W4-17 O-okayama, Meguro-ku, Tokyo, 152-8551, Japan.
⁷ Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan. kage@scl.kyoto-u.ac.jp.

Abstract

Most solid-state materials are composed of p-block anions, only in recent years the introduction of hydride anions (1s²) in oxides (e.g., SrVO₂H, BaTi(O,H)₃) has allowed the discovery of various interesting properties. Here we exploit the large polarizability of hydride anions (H^-) together with chalcogenide (Ch^2-) anions to construct a family of antiperovskites with soft anionic sublattices. The M₃HCh antiperovskites (M = Li, Na) adopt the ideal cubic structure except orthorhombic Na₃HS, despite the large variation in sizes of M and Ch. This unconventional robustness of cubic phase mainly originates from the large size-flexibility of the H^- anion. Theoretical and experimental studies reveal low migration barriers for Li⁺/Na⁺ transport and high ionic conductivity, possibly promoted by a soft phonon mode associated with the rotational motion of HM₆ octahedra in their cubic forms. Aliovalent substitution to create vacancies has further enhanced ionic conductivities of this series of antiperovskites, resulting in Na_2.9H(Se_0.9I_0.1) achieving a high conductivity of ~1 × 10^-4 S/cm (100 °C).

Grants and funding

JPMJCR1421/MEXT | JST | Core Research for Evolutional Science and Technology (CREST)