Sn‐O Dual‐Substituted Chlorine‐Rich Argyrodite Electrolyte with Enhanced Moisture and Electrochemical Stability

Abstract Chlorine‐rich argyrodite sulfides are one of the most promising solid electrolytes for all‐solid‐state batteries owing to their remarkable ionic conductivity and decent mechanical properties. However, their application has been limited by imperfections such as moisture instability and poor electrochemical stability. Herein, a Sn and O is proposed dual‐substitution strategy in Li_5.4PS_4.4Cl_1.6 (LPSC) to improve the moisture tolerance and boost the electrochemical performance. The optimized composition of Li_5.5(P_0.9Sn_0.1)(S_4.2O_0.2)Cl_1.6 (LPSC‐10) sintered at 500 °C exhibits a room‐temperature ionic conductivity of 8.7 mS cm⁻¹, an electrochemical window up to 5 V, a critical current density of 1.2 mA cm⁻², and stable lithium plating/striping. When exposed to humid air, LPSC‐10 exhibits a small increment in total resistance, generates a mild amount of H₂S gas, and displays favorable structure stability after heat treatment. The first‐principles calculation confirms that the dual‐substituted composition less tends to be hydrolyzed than the un‐substituted one. The all‐solid‐state battery with LiIn|NMC811 electrodes presents a high initial discharge capacity of 103.6 mAh g⁻¹ at 0.5 C rates and maintains 101.4 mAh g⁻¹ at the 100th cycle, with a 97.9% capacity retention rate. The present study opens a new alternative for simultaneously promoting moisture and electrochemical stability.