Preparation of polyvinylidene fluoride-co-hexafluoropropylene-based polymer gel electrolyte and its performance evaluation for application in EDLCs

Polymer gel electrolyte (PGE) film is prepared by incorporating polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) as polymer, ethylene carbonate (EC)-propylene carbonate (PC) as plasticizers and tetraethylammonium tetrafluoroborate (TEABF4) as salt using solution cast technique. By varying weight percentages of EC-PC-TEABF4 into a host polymer, different samples of PGE were prepared, and the concentration of EC-PC-TEABF4 was optimized for maximum conductivity, and stability of the prepared film. The maximum ionic conductivity of the order of 4.9x10-3cm-1 was determined for 80 wt% of [EC-PC (1:1 v/v)-TEABF4 (1.0M)]. From the conductivity as a function of temperature, activation energy Ea was calculated and it is about 0.06 eV. Overall, the amorphous structure was confirmed by X-ray diffraction analysis. Dielectric and impedance spectroscopic analysis was also carried out to understand the electrical behaviour of electrolyte using modified Debye's function. An ionic character of prepared electrolyte was confirmed from DC polarization method. The ionic transference number of 0.91 was calculated from the data while the electrical potential stability window was found to be 3.8V. The electrical performance of prepared PGE was examined by fabricating electrical double-layer capacitor (EDLC). In a supercapacitor, commercially procured activated carbon electrodes were employed. The specific capacitance of EDLC cell is found to be approximate to 60 mF cm-2, and equivalent single-electrode capacitance is about 39F g(-1).