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

Abstract 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 Li 7 Sn 0.1 P 2.8 S 10.5 O 0.2 is twice of that of the pristine Li 7 P 3 S 11 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 Li 7 P 3 S 11 , the newly‐designed electrolyte largely suppresses the hydrolysis in the air. Furthermore, galvanostatic cycling of symmetric cells demonstrate that Li 7 Sn 0.1 P 2.8 S 10.5 O 0.2 enables improved interfacial compatibility towards lithium metal. Hence, the all‐solid‐state batteries with Li 7 Sn 0.5 x P 3− x S 11−2.5 x O x 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.