Studies of lithium argyrodite solid electrolytes for all‐solid‐state batteries

Rechargeable all-solid-state lithium Li-ion batteries (AS-LIBs) are attractive power sources for electrochemical applications; due to their potentiality in improving safety and stability over conventional batteries with liquid electrolytes. AS-LIBs require a Li-fast ion conductor (FIC) as the solid electrolyte. Finding a solid electrolyte with high ionic conductivity and compatibility with other battery components is a key factor in building high performance AS-LIBs. There have been numerous studies, e.g., on lithium rich sulfide glasses as solid electrolytes. However, the limited current density remains a major obstacle in developing competitive batteries based on the known solid electrolytes. Here we prepare argyrodite-type Li6PS5X (X = Cl, Br, I) using mechanical milling followed by annealing. XRD characterization reveals the formation and growth of Li6PS5X crystals in samples under varying annealing conditions. For Li6PS5Cl an ionic conductivity of the order of 10−4 S/cm is reached at room temperature, which is close to the Li mobility in conventional liquid electrolytes (LiPF6 in various carbonates) and well suitable for AS-LIBs.