Preliminary study on the performance of a redox capacitor with the use of ionic liquid-based gel polymer electrolyte and polypyrrole electrodes

Redox capacitor, which is one type of supercapacitor, has been attracted tremendously as it shows 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 (tau(0)) of the redox capacitor is about 31.57 s implying somewhat fast redox reactions. Initial single electrode specific capacitance (C-SC) was 150.2 Fg(-1), and at the 500th cycle, it was 40.03 Fg(-1). The decrease of the C-SC may be due to the formation of the passivation layer at the GPE/electrode interface, resulting in degradation upon cycling. The GCD test resulted 48.4 Fg(-1) of initial single-electrode specific discharge capacitance (C-sd) value. Upon 1000 cycles, it was reached 22.3 Fg(-1). The decrease of C-sd may be due to the degradation of the electrode and the IL-based GPE upon prolonged cycling.

Automated summary

The study fabricated a redox capacitor with an ionic liquid-based gel polymer electrolyte, showing high specific capacitance and good stability, but exhibiting degradation during cycling.