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

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).

SUBMITTER: Gao S 

PROVIDER: S-EPMC7794446 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature