Nature Communications | 2021
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 (1s 2 ) in oxides (e.g., SrVO 2 H, 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 M 3 HCh antiperovskites (M\u2009=\u2009Li, Na) adopt the ideal cubic structure except orthorhombic Na 3 HS, 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 HM 6 octahedra in their cubic forms. Aliovalent substitution to create vacancies has further enhanced ionic conductivities of this series of antiperovskites, resulting in Na 2.9 H(Se 0.9 I 0.1 ) achieving a high conductivity of ~1\u2009× 10 –4 S/cm (100\u2009°C). Oxide-based lithium/sodium-rich antiperovskites are regarded as promising solid electrolytes. Here, authors report a series of antiperovskites with a soft lattice containing hydride (H – ) and chalcogenide (S 2– , Se 2– , Te 2– ) anions, enabling the fast Li + /Na + transport assisted by rotational phonon modes.