Improved performance of electric double layer capacitor using redox additive (VO2+/VO2+) aqueous electrolyte

Electric double layer capacitors (EDLCs) were fabricated using biomass derived porous activated carbon as electrode material with 1 M H2SO4 and VOSO4 added 1 M H2SO4 as electrolytes. Here, VOSO4 was used as redox additive to improve the overall performance of EDLC. As expected, the VOSO4 electrolyte showed ∼43% of improved specific capacitance of 630.6 F g−1 at 1 mA cm−2 compared to pristine 1 M H2SO4 (440.6 F g−1) due to the contribution of VO2+/VO2+ redox reaction at the electrode–electrolyte interface. Possible redox reaction mechanism of VO2+/VO2+ pair is also briefly illustrated. The good cycling performance of 97.57% capacitance retention was observed even after 4000 cycles. For comparison, the polymer gel electrolyte (PVA/VOSO4/H2SO4) was also prepared and then the performance of the fabricated EDLCs was studied. Overall, these findings could open up a simple and cost effective way to improve the performance of EDLCs significantly.