“…4,5 Various electrode materials have been widely used as supercapacitive electrode materials, such as carbon materials, conducting polymers, and metal oxides/hydroxides. [6][7][8] Manganese dioxide (MnO 2 ) as an electrode material is of great interest due to its alterable chemical, structural, and electronic properties. It exists in various polymorphic forms such as a (hollandite), b (pyrolusite), g (intergrowth), d (birnessite), R (Ramsedellite), and l (spinel) phases (layered and tunneled structures).…”