Li-rich channels as the material gene for facile lithium diffusion in halide solid electrolytes

Abstract

Halide solid electrolytes have attracted intense research interest recently for application in all-solid-state lithium-ion batteries. Herein, we present a systematic first-principles study of the Li3MX6 (M: multivalent cation; X: halogen anion) halide family that unveils the link between Li-rich channels and ionic conductivity, highlighting the former as a material gene in these compounds. By screening a total of 180 halides for those with high thermodynamic stability, wide electrochemical window, low chemical reactivity, and decent Li-ion conductivity, we identify seven unexplored candidates for solid electrolytes. From these halides and another four prototype compounds, we discover that the facile Li diffusion is rooted in the availability of diffusion pathways which can avoid direct connection with M cations—that is, where the local environment is Li-rich. These findings shed light on strategies for regulating cation and anion frameworks to establish Li-rich channels in the design of high-performance inorganic solid electrolytes.