Coupled polymer-cation coordination and anion-derived inorganic-rich interphases in ionic liquid-regulated gel electrolytes for stable lithium metal batteries

The practical application of lithium metal batteries is constrained by low coulombic efficiency and safety risks arising from Li dendrite growth. Developing functional gel polymer electrolytes (GPEs) systems is recognized as promising approach to address these challenges. In this work, a novel GPE (HFP/PEO-EMIM) was obtained by functionalizing the PVDF-HFP/PEO composite with EMIMTFSI ionic liquid. The resulting HFP/PEO-EMIM exhibits strong chemical stability and excellent heat resistance. The introduction of EMIMTFSI improves the interfacial compatibility between HFP/PEO-EMIM and the Li anode. More importantly, experiments and theoretical calculations show that EMIM + cations preferentially interact with polymer molecules, ensuring high Li flux and accelerating its transport. Therefore, HFP/PEO-EMIM exhibits a high ionic conductivity of 1.82 mS cm −1 . Additionally, the enriched TFSI − promotes the formation of a stable inorganic-rich SEI, enabling uniform Li deposition. As expected, the Li||HFP/PEO-EMIM||Li symmetric cell maintains low voltage hysteresis after stable cycling for 3600 h, and the optimized LiFePO 4 ||Li full cell retains 95% of its initial capacity after 650 cycles at 1 C, remaining stable for over 500 cycles at 3 C. Furthermore, extended cycle life was also observed in LiCoO 2 cells and LiFePO 4 pouch cells, underscoring the broad practical potential of the proposed electrolyte system.