Insight of alkyl imidazolium tetrafluoroborate ionic gels as supercapacitors and motion sensors: Effects of alkyl chain length and intermolecular interactions

Ionic gels as novel conductive components for flexible electronics are key to developing and improving the performance of next-generation electronic devices. Herein, for the first time, the structure-activity relationship of ionic gels based on poly(vinylidene fluoride-hexafluoropropylene) embedded with different alkyl chain lengths of imidazole ionic liquids is reported in detail. Surface morphology, internal structure, mechanical properties, electrochemical properties, and simulations are used to investigate alkyl chain effects on ionic gels. The results show that ionic gels with shorter alkyl chain lengths of imidazole cation have the highest electrochemical performance and porosity, among which the ionic gels based on 1-ethyl-3-methylimidazole tetrafluoroborate ionic liquid have the highest ionic conductivity (5.27 × 10 −3  S cm −1 ), and the assembled flexible capacitors have better specific capacitance with 261 F g −1 and energy density with 36.25 Wh kg −1 . On the contrary, the longer the chain, the better the mechanical properties: the ionic gels prepared with 1-decyl-3-methylimidazole tetrafluoroborate ionic liquid have the best ductility (77.4% deformation) and potential application value in human sensing and monitoring. This work provides a viable idea for the design, development, and application of ionic gels as flexible electronics.