Performance evaluation of polyaniline-based redox capacitors with respect to polymerization current density

Abstract

Supercapacitors (SCs) are promising alternative energy storage devices due to their relatively fast rate of energy storage and delivery. Redox capacitors in the family of SCs are based on conducting polymer (CP) or transition metal oxide electrodes. In this study, symmetric redox capacitors have been fabricated utilizing the CP, polyaniline (PANI) as electrodes and a gel polymer electrolyte (GPE) based on polyvinylidenefluoride (PVdF) as the electrolyte. Investigations have been carried out to study the effect of polymerization current density of PANI electrodes on the performance of redox capacitors. Polymerization current density was varied from 4 mA cm−2 to 9 mA cm−2 and the performance of redox capacitors was evaluated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) test and galvanostatic charge discharge (GCD) test. EIS results showed that redox capacitor having electrodes prepared using the current density 7 mA cm−2 has the lowest charge transfer resistance and CV test elucidated that the same redox capacitor has maintained around 80% of maximum specific capacity from its initial value after 200 cycles. GCD results exhibited the highest specific discharge capacity of 421.4 F g−1, specific power density of 935.6 W kg−1 and specific energy density of 8.0 Wh kg−1 after 200 cycles for the same capacitor.