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

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 (NO₃ ^-) anions with multidentate coordination propensity. One NO₃ ^- could coordinate with multiple Li⁺ ions to promote the formation of bridged complexes ([Li⁺-NO₃ ^--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 NO₃ ^- anions in modifying the solvation structure and interphase composition/structure, offering novel perspectives for advanced electrolytes for Li||SPAN batteries.