Amorphous nickel oxide and crystalline manganese oxide nanocomposite electrode for transparent and flexible supercapacitor

Among numerous active electrode materials, transition metal oxides are promising electrode materials in supercapacitors. Here, we fabricated amorphous nickel oxide and crystalline manganese oxide nanocomposite positive electrode for transparent and flexible supercapacitor. The nanocomposite was prepared via a two-step method. First, the amorphous nickel oxide film was prepared using a room-temperature chemical solution deposition and photochemical method. UV light irradiation causes condensation and densification of nickel oxide film by photochemical activation at room temperature. Second, the crystalline manganese oxide was prepared by chemical bath deposition method. The synergistic effect of the two components provides high electrochemical activity. A high-performance, transparent and flexible asymmetric supercapacitor was made of the nanocomposite positive electrode and worked in a wide voltage window of 1.2 V. An area capacitance of 48.1 mF/cm2 and an energy density of 9.62 µWh/cm2 at a power density of 28.9 µW/cm2 were achieved. After a 10,000 cycles, the capacitance of the device retains about 90% of its initial value. The high integrated electrochemical performances of the device were attributed to higher storage and transport capacity of the nanocomposite for both ions and electrons. These findings make amorphous and crystalline transition metal oxide nanocomposites as advanced electrode materials for transparent and flexible supercapacitors.