Strong Interfacial Adhesion between the Li₂S Cathode and a Functional Li₇P_2.9Ce_0.2S_10.9Cl_0.3 Solid-State Electrolyte Endowed Long-Term Cycle Stability to All-Solid-State Lithium–Sulfur Batteries

The extrinsic cathode interface between the sulfide electrolyte and the Li2S electrode is always ignored in all-solid-state lithium–sulfur batteries. However, the aggregation of the Li2S cathode is still observed during cycling. The gradually lost extrinsic contact interface between the cathode and the electrolyte would result in considerable interface resistance and severe capacity decay in the cell due to the lack of efficient electron and ionic conduction at the interface. Herein, a facile dual-doping strategy demonstrates the synthesis of a functional inorganic electrolyte. The obtained Li7P2.9Ce0.2S10.9Cl0.3 glass–ceramic electrolyte shows a higher-lithium-ionic conductivity of 3.2 mS cm–1 at room temperature. Further, UV–vis absorption and ex situ scanning electron microscopy studies confirm robust interfacial adhesion between the functional inorganic electrolyte, Li7P2.9Ce0.2S10.9Cl0.3, and the Li2S cathode. Thus, a stable extrinsic cathode interface is unprecedently built. Finally, the all-solid-state lithium–sulfur battery based on the Li7P2.9Ce0.2S10.9Cl0.3 electrolyte delivers a higher reversible initial capacity of 617 mA h g–1, a lower interface resistance of 25 Ω cm2 and much better cycling stability (with a high capacity retention of 89% after 100 cycles) than the pristine Li7P3S11 electrolyte.