Composition Screening of Lithium- and Sodium-Rich Anti-Perovskites for Fast-Conducting Solid Electrolytes

Li- and Na-rich anti-perovskites are receiving increasing attention as high-performance solid electrolytes for applications within all-solid-state batteries. The defect chemistry and ionic transport in a wide range of Li3-xNaxOCl1-yBry compositions are examined using advanced materials modeling techniques. Our calculations indicate that alkali-halide Schottky defect pairs are the dominant type of intrinsic disorder in these materials. Li-ion conductivity is shown to significantly exceed Na-ion conductivity, with the highest conductivities found for Li3OCl and Li3OBr. The effect of Cl/Br mixing on conductivity is shown to be small but could be used to fine-tune the activation energy. Both low conductivities and high activation energy barriers are found for the mixed Li/Na systems, which suggests that they would make poor solid electrolytes. The results presented here will aid the future optimization of anti-perovskite materials for solid electrolyte applications.