A highly adhesive PIL/IL gel polymer electrolyte for use in flexible solid state supercapacitors

In this work we have demonstrated how to prepare a novel gel polymer electrolyte (GPE) with remarkable adhesive characteristics by combining a synthesized poly(ionic liquid) consisting of poly(1-vinyl-3-propylimidazolium bis(fluorosulfonyl)imide) (poly(VPIFSI)) and a commercial ionic liquid: 1-ethyl-3-methyl imidazolium bis(fluorosulfonyl)imide (EMIFSI). For this purpose several PIL/IL-GPEs systems (considering the amount of IL) were subjected to electrochemical characterization. The influence of the PIL/IL-GPE (50 wt% of IL) on the properties of a flexible solid state supercapacitor was evaluated using electrochemical impedance spectroscopy, cyclic voltammetry and the galvanostatic charge/discharge technique that allows synchronous measurements of the cell voltage and the potential of the positive and negative electrodes. The influence of the ions on the formation of the electric double layer in the device during cycling employing different conditions and folding angles is discussed. The properties of the adhesive PIL/IL-GPE, such as high conductivity, good interaction between the PIL matrix and the IL liquid phase that prevents any leakage (thereby contributing to greater safety) together with the good adherability and wettability of the gel electrolyte on the electrode surface have produced a device with an improved rate capability and cyclability that undergoes hardly any changes in C,, E, and P of the cell when folded.The authors would like to thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil, for the financial support received (Universal 2014, Process No. 458487/2014-7). The authors are also grateful to the Instituto Nacional de Ciência e Tecnologia em Nanomateriais de Carbono – INCT Nanocarbono and to profs. Dorila Piló Veloso and José Dias de Souza Filho (Department of Chemistry/UFMG/Brazil) for performing the NMR analysis. S.A.Alexandre also acknowledges the scholarship received from CNPq. R.L. Lavall is recipient of fellowship from CNPq (grant number 313304/2017-3). R. Santamaría would like to thank financial support from Ministerio de Economía, Industria y Competitividad (project MAT2016-77114-R)