Polarity-Matched Perfluorinated Gel Electrolytes toward Safe Sodium-Ion Batteries

Fluorinated solvents and gel electrolytes offer potential for safe sodium-ion batteries (SIBs); yet, conventional acrylate gels show polarity mismatch, poor compatibility, and sluggish Na + transport. Here, we develop an all-fluorinated gel electrolyte by introducing a low-surface-energy perfluorinated acrylate monomer (PFHEA) into an FEMC/TFPC system. The −C 8 F 17 chains enable polarity matching and uniform gelation, improving wettability, reducing interfacial resistance, and restructuring the Na + solvation environment. Molecular dynamics and spectroscopic results indicate enhanced contact-ion pair formation and fluorine-rich SEI/CEI layers, boosting transport kinetics, interfacial stability, and thermal tolerance. Consequently, 2.6 Ah NCFM||HC pouch cells retain 88.1% capacity after 2600 cycles at 25 °C─representing 2–3-fold longer lifetimes than previously reported Ah-level Na pouch cells. A 115 Ah pouch cell further exhibits a negligible temperature rise during nail penetration, confirming intrinsic flame retardancy. This PFHEA-based gel provides a feasible route toward safe SIBs.