Investigation of a gel polymer electrolyte based on polyacrylonitrile and magnesium chloride for a redox capacitor

Abstract

To supplement the ever increasing power demand in the present day world, supercapacitors have emerged as one of the suitable power storage devices. Redox capacitors have received a considerable attention due to factors such as high cycle ability, satisfactory specific capacitance and good stability. There are many reports on redox capacitors based on liquid electrolytes but these have several drawbacks. In this study, a magnesium chloride (MgCl 2) based gel polymer electrolyte was prepared and characterized for its suitability to be used in a redox capacitor. The composition, 0.1 polyacrylonitrile (PAN):0.4 ethylene carbonate (EC):0.4 propylene carbonate (PC):0.125 MgCl 2 (weight ratios) exhibits the highest room temperature conductivity of 4.08×10 -4 S cm -1. Conductivity variation of this sample with the temperature shows Arrhenius behavior. The ionic transference number is 0.84. This shows that the GPE is an ionic conductor. Redox capacitors were fabricated with two polypyrrole (PPy) electrodes. They were characterized using Cyclic Voltammetry technique, Impedance Spectroscopy and Galvanostatic Charge Discharge test. Cycling at the scan rate of 10 mV/s within the potential window of -1.4 V to +1.4 V showed a specific capacitance of 120.35 F/g. Impedance data showed the electrochemical behavior of the device having resistive and capacitive behavior. Galvanostatic charge discharge test results exhibit average power density and energy density of 341 W/kg and 5 Wh/kg respectively.