Tailoring the Cation Lattice for Chloride Lithium‐Ion Conductors

Abstract All‐solid‐state Li‐ion batteries require Li‐ion conductors as solid electrolytes (SEs). Li‐containing halides are emerging as a promising class of lithium‐ion conductors with good electrochemical stability and other properties needed for SEs in all‐solid‐state batteries. Compared to oxides and sulfides, Li‐ion diffusion mechanisms in Li‐containing halides are less well understood, in particular regarding the effects of Li content and cation sublattices, which can be tailored for improving Li‐ion conduction. Using first‐principles computation, a systematic study is performed on the Li‐ion conduction of known Li‐containing chlorides with close‐packed anion frameworks and a wide range of their doped compounds. A dozen potential chloride Li‐ion conductors are predicted with increased Li‐ion conductivities, and it is revealed that the Li‐ion migration is greatly impacted by the cation configuration and concentrations. By analyzing a large set of materials data, it is proposed that low Li content, low cation concentration, and sparse cation distribution increase Li‐ion conduction in chlorides, and these principles are demonstrated in designing new chloride Li‐ion conductors. This study provides insights into the effects of the cation sublattice on Li‐ion diffusion, highlights potential chloride Li superionic conductors, and proposes design principles to further develop halide Li‐ion conductors.