Electrophilic Effect of Polysulfide Cations Induces the Formation of Li+-Transport-Enhanced Polymer Electrolyte

Slow ion transport kinetics hinder the development of solid polymer electrolytes in lithium metal batteries. Herein, we adopt the electron-deficient Li₃S₆⁺ as an electrophilic initiator to induce the ring-opening copolymerization of 1,3-dioxolane and ethylene glycol diglycidyl ether in a precursor solution. The Li₃S₆⁺ in prepared polymer electrolyte (FITSE) improves both ionic conductivity and Li⁺ transference number while generating a gradient sulfur-containing SEI layer to promote uniform lithium deposition. The Li||FITSE||LFP cell delivers a high initial capacity of 138.8 mAh g^–1 with a capacity retention of 94.6% over 250 cycles at 1 C and maintains a capacity of 60.96 mAh g^–1 over 130 cycles even at −10 °C.