Probing Ion-transport mechansim in lithium based antiperovskite solid-electrolytes*

Solid electrolytes are enablers for all-solid-state batteries that incorporate Li metal anodes, promising cell-level energy densities up to 500 Wh/kg and providing a paradigm change to the next-generation battery technology. The significant metrics for a successful solid electrolyte candidate include high ionic conductivity (> 10^-4 S cm^-1), electronic insulation (< 10^-10 S cm^-1), electrochemical stability, and ease in synthesis and processing. Within the last decade, Li-based antiperovskites (LiAP, Li_3-xOH_xX, X = Cl, Br) have emerged as an important emerging class of ion conductors for all-solid-state batteries. Here, Li resides in the traditional O occupancy site, X (typically a halide) is the A site, and O is the B site in classic perovskites, e.g. SrMnO₃). Despite the growing interest, there are two critical unresolved questions about LiAPs, what is the mechanistic effect of protons on Li transport? How does halide substitution affect the structure property correlation to enhance ion transport? Here, we seek to disentangle the coupled effect of structural stability induced by hydroxide-oxide substitution and halide mixing from Li-ion transport, by following proton and halide correlation dynamics with Li hopping.