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 Li5.4PS4.4Cl1.6 (LPSC) to improve the moisture tolerance and boost the electrochemical performance. The optimized composition of Li5.5(P0.9Sn0.1)(S4.2O0.2)Cl1.6 (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.By introducing Sn and O dual substitution in chlorine-rich argyrodite Li5.4PS4.4Cl1.6, and comparing the different substitution levels, Li5.5(P0.9Sn0.1)(S4.2O0.2)Cl1.6 is demonstrated to possess the enhanced moisture stability, exhibit the dendrite-free lithium stripping/plating at 0.5 mA cm−2, and enable high capacity retention of 97.9% at 0.5 C rate (101.4 mAh g−1 at 100th cycle) using NMC cathode.