Hydride-based antiperovskites with soft anionic sublattices as fast alkali ionic conductors.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33420012.
- Also identified by DOI 10.1038/s41467-020-20370-2 and PMC identifier 7794446.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Most solid-state materials are composed of p-block anions, only in recent years the introduction of hydride anions (1s<sup>2</sup>) in oxides (e.g., SrVO<sub>2</sub>H, BaTi(O,H)<sub>3</sub>) has allowed the discovery of various interesting properties. Here we exploit the large polarizability of hydride anions (H<sup>-</sup>) together with chalcogenide (Ch<sup>2-</sup>) anions to construct a family of antiperovskites with soft anionic sublattices. The M<sub>3</sub>HCh antiperovskites (M = Li, Na) adopt the ideal cubic structure except orthorhombic Na<sub>3</sub>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<sup>-</sup> anion. Theoretical and experimental studies reveal low migration barriers for Li<sup>+</sup>/Na<sup>+</sup> transport and high ionic conductivity, possibly promoted by a soft phonon mode associated with the rotational motion of HM<sub>6</sub> octahedra in their cubic forms. Aliovalent substitution to create vacancies has further enhanced ionic conductivities of this series of antiperovskites, resulting in Na<sub>2.9</sub>H(Se<sub>0.9</sub>I<sub>0.1</sub>) achieving a high conductivity of ~1 × 10<sup>-4</sup> S/cm (100 °C).