Application of Rod-Like Li₆PS₅Cl Directly Synthesized by a Liquid Phase Process to Sheet-Type Electrodes for All-Solid-State Lithium Batteries

All-solid-state lithium batteries employing sulfide-based solid electrolytes have emerged as promising next-generation batteries for large-scale energy storage applications because of their safety and high energy density. Among them, Li 6 PS 5 X (X = Cl, Br, I) with an argyrodite structure synthesized by planetary milling exhibits a rather high lithium ion conductivity of 10 −2 – 10 −3 S cm −1 at room temperature. Unfortunately, the planetary milling process has the disadvantage of producing the solid electrolytes with large, round-shaped particles. Recently, the solid electrolytes have been synthesized by not the mechanical milling but the liquid-phase process, which facilitates synthesis of sub-micrometer- to nanometer-sized solid electrolyte particles. It is important to reduce the particle size of the solid electrolyte to promote intimate contact with the active material in the composite cathode. Here, rod-like Li 6 PS 5 Cl solid electrolyte with a high ionic conductivity of 1.1 × 10 −3 S cm −1 at room temperature was, for the first time, directly prepared by a liquid phase process using only a stirring method. SEM images showed the electrolyte had a rod-like morphology with a length of 20–30 μm and a width of 2–3 μm. The composite cathode was prepared from a slurry and the cell performances were investigated.