Tailored Li₇P₃S₁₁Electrolyte by In₂S₃Doping Suppresses Electrochemical Decomposition for High-Performance All-Solid-State Lithium-Sulfur Batteries

The retentive functional intimate contact at the solid electrolyte/cathode interface and among the cathode components, for example, solid electrolyte, a conductive additive, and active material (S/Li₂S), is essential for high-performance solid-state lithium-sulfur batteries. Currently, thiophosphate-based electrolytes are plagued by failure at the interfaces due to the intrinsically narrow electrochemical stability window, which in principle, derive uneven irreversible redox reactions at the triple point of contact, which result in sulfur- and phosphorus-enriched interphases (e.g., Li₃P, P₂S_X, S, Li₂S_n, etc.), retard Li⁺conduction, and increase the interface resistance. Herein, structural tuning of Li₇P₃S₁₁was done using the In₂S₃dopant, and the designed Li_6.93P_2.97In_0.02S_10.92electrolyte presented better σ_Li+of 2.9 mS cm^-1and enhanced air stability @ RT. Furthermore, In₂S₃broadened the electrochemical stability window and suppressed the redox decomposition of Li₇P₃S₁₁at the interface in the Li₂S-composite cathode layer, ensuring effective (ionic/electronic) conduction. Therefore, the Li₂S/Li_6.93P_2.97In_0.02S_10.92/Li-In cell offers a high discharge capacity of 946.75 mA h g^-1with an ∼100% average Coulombic efficiency over 30 cycles. Moreover, the cell with Li_6.93P_2.97In_0.02S_10.92presented a low interfacial resistance of 127 compared to 383 ω for counterparts over 30 cycles, which could be benefitted from suppressed redox decomposition of the solid electrolyte and long-lasting intimate contact at the triple point of contact. Thus, the projected doping strategy developed a sulfide electrolyte to address the chemical/electrochemical stabilities and redox decomposition of sulfide electrolytes for the next-generation all-solid-state technologies.