Redox capacitor, which is one type of supercapacitor, has been attracted tremendously as they show a satisfactory specific capacitance, good cycle ability, and good stability. The present study reveals a redox capacitor fabricated with an ionic liquid (IL) based gel polymer electrolyte (GPE). Electrodes of the redox capacitor were fabricated with the conducting polymer, polypyrrole (PPy). The composition of the GPE was polyvinylidenefluoride-co-hexafluoropropylene (PVdF-co-HFP) : 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1E3MITF) : ZnTF. Characterization of redox capacitor was done by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD) tests. The relaxation time constant (τ0) of the redox capacitor is about 31.57 s implying somewhat fast redox reactions. Initial single electrode specific capacitance (CSC) was 150.16 Fg-1 and at the 500th cycle, it was 40.03 Fg-1. The decrease of the CSC may be due to the formation of the passivation layer at the GPE / electrode interface resulting in degradation upon cycling. The GCD test resulted 48.40 Fg-1 of initial single electrode specific discharge capacitance (Csd) value. Upon 1000 cycles, it was reached 22.25 Fg-1. The decrease of Csd may be due to the degradation of the electrode and the IL-based GPE upon prolonged cycling.

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With the concepts of green environment and the priority given on economical aspects, a great deal of research activities has been diverted towards clean and low-cost device fabrication. Central focus was on eliminating the use of toxic and expensive materials like Li and different solvents. Application of ionic liquid-based gel polymer electrolytes (GPEs) and non-Li electrodes can address many shortcomings associated with liquid, solid and GPEs. In the present study, characteristics of a rechargeable cell with 1-ethyl-3-methylimidazolium trifluoromethanesulphonate-based GPE having Zn and Sri Lankan natural graphite electrodes have been investigated. For characterization, electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge discharge test have been performed at room temperature. The open circuit voltage of the cell was about 1V. Specific charge and discharge capacities of the cell were 4.66 and 2.99 mA h g −1 , respectively. Moreover, efficiency of the specific charge was 80.2% over 500 cycles, while efficiency of specific discharge was 92% over 1000 cycles. These results proved the suitability of the electrolyte and electrodes investigated in the present study to be used well in rechargeable cells.

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