Method for preparing aqueous MnO₂ ink and capacitive energy storage devices comprising MnO₂

Abstract

In one aspect, the present disclosure relates to an improved method of preparing concentrated MnO.sub.2 ink with increased efficiency and cost effectiveness. The method involves mixing KMnO.sub.4 solution with highly crystalline carbon particles (HCCPs) with average diameters less than 800 nm at 30-60.degree. C. for at least 8 hours. The present disclosure further relates to a symmetric supercapacitor device comprising MnO.sub.2 coated electrodes and a solid state ionic liquid as electrolyte, as well as an interdigital transparent SC (IT-SC) device comprising aqueous MnO.sub.2 ink.