Enhancing Moisture and Electrochemical Stability of the Li_5.5PS_4.5Cl_1.5 Electrolyte by Oxygen Doping

Chlorine-rich argyrodite-type solid electrolyte Li_5.5PS_4.5Cl_1.5 has been a promising choice for solid-state batteries (SSBs) because of its ultrafast Li-ion conduction. However, the poor air/moisture stability and low electrochemical stability with pristine high-voltage cathodes hinder their applications. Herein, O-substituted Li_5.5PS_4.5-OCl_1.5 (x = 0, 0.075, 0.175, and 0.25) solid electrolytes are successfully synthesized. Among them, Li_5.5PS_4.425O_0.075Cl_1.5 delivers high ionic conductivity, improved moisture resistance, and enhanced electrochemical stability in higher voltage windows. SSBs using Li_5.5PS_4.425O_0.075Cl_1.5 show higher capacities and superior cyclability than those using Li_5.5PS_4.5Cl_1.5 combined with a pristine LiNi_0.8Mn_0.1Co_0.1O₂ cathode when operated at a high end-of-charge voltage of 4.5 V (vs Li⁺/Li⁰). Moreover, the batteries exhibit outstanding performance in a wide temperature range. This work provides a strategy to modify the inherent drawbacks of sulfide electrolytes, promoting their practical applications.