Enhanced Air and Electrochemical Stability of Li7P3S11–Based Solid Electrolytes Enabled by Aliovalent Substitution of SnO2

Sulfide solid electrolytes are excessively investigated on account of the high ionic conductivity. However, their applications are hindered by the air‐sensitivity and poor interfacial compatibility against lithium metal. Herein, Sn and O co‐doping strategy is designed to enhance the stability of the sulfide‐based solid state electrolyte towards air moisture and lithium metal. The ionic conductivity of Li7Sn0.1P2.8S10.5O0.2 is twice of that of the pristine Li7P3S11 due to the synergistic effect of Sn and O prepared by the solvent‐assisted ball milling method. Impressively, with partial substitution of S by O and P by Sn in Li7P3S11, the newly‐designed electrolyte largely suppresses the hydrolysis in the air. Furthermore, galvanostatic cycling of symmetric cells demonstrate that Li7Sn0.1P2.8S10.5O0.2 enables improved interfacial compatibility towards lithium metal. Hence, the all‐solid‐state batteries with Li7Sn0.5xP3−xS11−2.5xOx significantly elevate the cyclability and the reversible capacity. The co‐doping strategy provides a promising approach to achieve excellent chemical and electrochemical stability for the large‐scale application of sulfide‐based solid state electrolytes. Sn and O co‐doped Li7P3S11 is synthesized using the solvent‐assisted ball milling method. The combination of O and Sn‐aliovalent doping not only enables an improved ionic conductivity but more importantly realizes an intensively enhanced interfacial compatibility and air stability. This kind of doping method provides a universal approach for modified sulfide electrolytes.