Preparation and characterization of a Polyacrylonitrile based gel polymer electrolyte for redox capacitors

In this study, a gel polymer electrolyte (GPE) consisting with polyacrylonitrile (PAN), ethylene carbonate (EC), propylene carbonate (PC) and magnesium trifluromethane sulfonate (Mg(CF₃SO₃)₂) was prepared using the hot pressed method. The starting materials were heated at 130 °C for 2 hours and the resulting hot viscous mixture was pressed in between two well cleaned glass plates. The composition was fine-tuned by varying the salt and the polymer concentration in order to obtain a mechanically stable, thin and flexible film with a high ionic conductivity. It was found that the composition, 105 PAN : 150 MgTF : 400 EC : 400 PC gives the maximum conductivity of 1.06 x 10^-2 Scm^-1. DC polarization test done with blocking electrodes confirmed the ionic nature of the sample while the results obtained with non-blocking electrodes proved that the anionic contribution for the conductivity is dominant. The sample was used in redox capacitors having two identical polypyrrole electrodes doped with dodecylbenzesulfonate. Cyclic Voltammetry, Galvanostatic Charge Discharge and Electrochemical Impedance Spectroscopy techniques were used to evaluate the performance of the redox capacitors. The specific capacitance was high at low scan rates. The electrolyte was quite stable when use in the redox capacitors. Further, redox capacitor was having a good cycleability which is one of the important key issues to be considered for practical applications.