Sn-Substituted Argyrodite Li6PS5Cl Solid Electrolyte for Improving Interfacial and Atmospheric Stability

Abstract

Sulfide-based solid electrolytes exhibit good formability and superior ionic conductivity. However, these electrolytes can react with atmospheric moisture to generate H2S gas, resulting in performance degradation. In this study, we attempted to improve the stability of the interface between Li metal and an argyrodite Li6Ps5Cl solid electrolyte by partially substituting P with Sn to form an Sn–S bond. The solid electrolyte was synthesized via liquid synthesis instead of the conventional mechanical milling method. X-ray diffraction analyses confirmed that solid electrolytes have an argyrodite structure and peak shift occurs as substitution increases. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses confirmed that the particle size gradually increased, and the components were evenly distributed. Moreover, electrochemical impedance spectroscopy and DC cycling confirmed that the ionic conductivity decreased slightly but that the cycling behavior was stable for about 500 h at X = 0.05. The amount of H2S gas generated when the solid electrolyte is exposed to moisture was measured using a gas sensor. Stability against atmospheric moisture was improved. In conclusion, liquid-phase synthesis could be applied for the large-scale production of argyrodite-based Li6PS5Cl solid electrolytes. Moreover, Sn substitution improved the electrochemical stability of the solid electrolyte.