“…The use of ruthenium oxide, cobalt oxide, nickel oxide, and vanadium oxide as electrode materials in energy storage devices had been favored in the past. − However, their high cost and toxic nature presented significant obstacles to their commercial applications. Alternatively, manganese dioxide (MnO 2 ) had been favored for its various oxidation states and positive operational range, which offered a theoretical C sp of 1370 F g –1 .…”