A Redox-Additive Electrolyte and Nanostructured Electrode for Enhanced Supercapacitor Energy Density

We demonstrate an ultrahigh energy density asymmetric supercapacitor (ASC) having a novel NiCo(CO3)(OH)2 nanoneedle positive electrode, Fe2O3/rGO nanocomposite negative electrode, and advanced potassium ferricyanide (K3[Fe(CN)6])/potassium hydroxide (KOH) electrolyte. The electrode materials were synthesized by a hydrothermal technique. The unique positive electrode was first shown to have a remarkable specific capacitance (Csp) of 3248.9 F g–1 at 1 A g–1 in an electrolyte containing 0.06 M K3[Fe(CN)6] and 3 M KOH. The ASC gives a superior energy density of 84.1 W h kg–1 at a power density of 825 W kg–1. The findings in this work provide a very promising approach toward the development of high-performance energy storage devices.