An Ionic Liquid/Poly(vinylidene fluoride‐co‐hexafluoropropylene) Gel‐Polymer Electrolyte with a Compatible Interface for Sodium‐Based Batteries

Abstract Ionic liquid gel‐polymer electrolytes (GPEs) have attracted increasing attention, owing to their merits of safety and reliability. However, the high viscosity of ionic liquid requires better transmission channels for the polymer. Exploration of ionic liquid GPEs with high ionic conductivity and excellent transmission channels is a possible strategy to optimize the practicability of sodium‐based technology. A flexible GPE with high ionic conductivity and excellent transmission channels is synthesized with poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF−HFP) as the base material blended with the water‐insoluble ionic liquid N‐methyl‐N‐butyl piperidine difluoromethylimide ([PP 14 ][TFSI]) by using a phase‐inversion technique. A polydopamine coating is then introduced into the GPE to improve wettability and compatibility. The thermal decomposition temperature of the prepared gel‐polymer films is greater than 450 °C. Our activated GPE achieves good safety, a wide electrochemical window, and high ionic conductivity. When testing a sodium‐ion battery with Prussian blue as the cathode, the batteries show good cycling performance. Our results suggest that the as‐prepared GPE can be efficiently and safely used in sodium‐ion batteries.