Crystalline Halide Substituted Li-Argyrodites as Solid Electrolytes for Lithium Secondary Batteries

Abstract

Apparent lithium ionic conductivity of crystalline Li-Argyrodite materials (Li6PS5X, X = Cl, Br) was measured to be about 10 exp(-4) S/cm, which is higher than that of common solid electrolytes like LiPON. The materials are electrochemically stable at least up to 5 V vs. Li/Li+ and thus applicable as electrolyte with standard cathode active materials in lithium secondary batteries. An all-solid-state battery using Li-Argyrodite as electrolyte with lithium titanate as cathode and lithium aluminum alloy anode was fabricated, showing a specific capacity of 150 mAh/g at a current rate of C/50 at 75 degC. However, the cell shows poor rate capability and a large polarization at room temperature.