Improving the energy density of quasi-solid-state electric double-layer capacitors by introducing redox additives into gel polymer electrolytes

A redox-active gel polymer electrolyte was prepared by introducing KI/VOSO4 redox additives into a polyvinyl alcohol-H2SO4 gel electrolyte for application in a quasi-solid-state electric double-layer capacitor (EDLC) based on activated carbon. The EDLC obtained had a high electrode-specific capacitance of 1232.8 F g(-1) and a high energy density of 25.4W h kg(-1); these values are higher than that of an EDLC with a conventional gel electrolyte. The improved energy storage is attributed to Faradaic pseudocapacitance related to the redox-active ions in the gel polymer electrolyte.