Electrochemically Stable Li3-XIn1-XHfXCl6 Halide Solid Electrolytes for All-Solid-State Batteries

Halide solid electrolytes (SEs) stand out among the many different types of SEs owing to their high ionic conductivity and excellent oxidative stability. Aliovalent substitution is a common strategy to enhance the ionic conductivity of halide electrolytes, but this strategy significantly decreases their electrochemical stability. Herein, we report Hf-substituted Li3InCl6 (Li3-xIn1-xHfxCl6, 0 < x < 0.7) SEs, in which a low concentration (0.1 < x < 0.5) of Hf enhances the ionic conductivity without affecting the electrochemical stability. Among them, Li2.7In0.7Hf0.3Cl6 exhibits a high ionic conductivity of 1.28 mS cm-1 and a wide electrochemical stability window of 2.68-4.22 V. All-solid-state batteries fabricated using Li2.7In0.7Hf0.3Cl6 SE present high discharge capacity and good cycling stability at 25 degrees C. Furthermore, we summarize the methods of crystal structure regulation by which aliovalent substitution of halide SEs is achieved and discuss potential research directions in the design of novel halide SEs with high ionic conductivity and electrochemical stability.

Automated summary

Hf-substituted Li3InCl6 solid electrolytes with low concentration of Hf (0.1<x<0.5) exhibited enhanced ionic conductivity without affecting electrochemical stability. Li2.7In0.7Hf0.3Cl6 showed high ionic conductivity and a wide electrochemical stability window. Solid-state batteries using Li2.7In0.7Hf0.3Cl6 exhibited high discharge capacity and good cycling stability at 25 degrees C.