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 (K-3[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 (C-sp) of 3248.9 F g(-1) at 1 A g(-1) in an electrolyte containing 0.06 M K-3[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.