Anion‐Induced Bridged Electrolyte Design Strategy Mitigates Capacity Decay in Lithium–Sulfurized Polyacrylonitrile Batteries

Abstract

Abstract Previous strategies have improved the compatibility of sulfurized polyacrylonitrile (SPAN) in ether‐based electrolytes by constructing a relatively stable interphase, but the electrode degradation caused by sluggish kinetics has limited the practical implementation of SPAN cathodes. Here, we propose an anion‐induced bridged electrolyte (AIBE) design strategy to simultaneously achieve anode/cathode compatibility, anion‐derived interphase formation, and fast Li + transfer kinetics in Li||SPAN batteries through utilizing small‐sized nitrate (NO 3 − ) anions with multidentate coordination propensity. One NO 3 − could coordinate with multiple Li + ions to promote the formation of bridged complexes ([Li + –NO 3 − –Li + ]) with reduced Li + –Li + distances. These densely packed ion pairs create an anion‐dominated solvation structure and fast Li + interfacial reaction kinetics. Simultaneously, the optimized AIBE facilitates the formation of a robust inorganic‐rich interphase to suppress electrode degradation. This electrolyte mitigates SPAN cathode decay, enabling a Li||SPAN full cell to retain 80.5% capacity after 500 cycles. An Ah‐level pouch cell (50 µm Li, 4.0 mA h cm −2 SPAN, lean 1.52 g Ah −1 electrolyte) achieves 99.7% capacity retention after 95 cycles. This work elucidates the fundamental role of NO 3 − anions in modifying the solvation structure and interphase composition/structure, offering novel perspectives for advanced electrolytes for Li||SPAN batteries.