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.