Cluster‐Engineering Enabling Carbonate‐Compatible Li 2 S Cathode for Long‐Life and Safe Quasi‐Solid‐State Batteries with Wide‐Temperature Adaptability

Abstract With a superior capacity of 1166 mAh g −1 and oxygen‐free composition, Li 2 S cathode holds promise in developing high‐energy, intrinsically safe lithium batteries, especially when coupling high‐capacity Si anodes. However, this cell design is challenged by the incompatible electrolyte preferences of ether‐stable Li 2 S and carbonate‐friendly Si. Herein, this obstacle is overcome by engineering a cluster‐based Li 2 S cathode compatible with carbonate‐based electrolyte, enabling effective pairing with Si anodes for advancing high‐energy yet safe lithium batteries. Cluster engineering shifts the redox pathway from a conventional solid–liquid–solid route involving soluble lithium polysulfide (LiPS) to direct solid–solid conversion, thereby eliminating LiPS formation and nucleophilic degradation in carbonate. Chemical anchoring of Li 2 S clusters onto hierarchical polymer backbones further promotes solid‐state redox kinetics in carbonate‐based gel polymer electrolytes. This cathode forms in situ during cell formation, addressing the handling and processing difficulty of moisture‐sensitive Li 2 S. The resulting quasi‐solid‐state battery delivers a high specific energy of 434 Wh kg −1 , while achieving stable cycling over 600 cycles and high capacities of 600–1300 mAh g −1 across −20 to 90 °C at high rates up to 2 C. The quasi‐solid‐state pouch cells exhibit robust safety, maintaining stable operation upon nail penetration and mechanical cutting in ambient air.