Electrosynthesis of a corn flake-like NiO nanostructure on nickel foam for polymer gel electrolyte-based high performance asymmetric supercapacitors

Supercapacitors are attracting attention as energy storage devices but the energy density and cycle life of electrode materials require further improvement for commercial applications. To achieve this goal, a corn flake-like NiO nanostructure on nickel foam was synthesized using a facile electrodeposition method. X-ray diffraction, high resolution transmission electron microscopy, and field emission scanning electron microscopy confirmed the formation of a corn flake-like NiO nanostructure on nickel foam. The electrochemical properties of the as-prepared NiO nanostructure were analyzed by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The direct formation of a highly porous corn flake-like NiO nanostructure on nickel foam provided an excellent electronic charge transfer rate with a low equivalent series resistance and good ionic accessibility for strong supercapacitive behavior. The as-prepared NiO nanostructure on nickel foam exhibited a specific capacitance of 1717 F g(-1) and a capacitance retention of 87% after 5000 cycles. The NiO//activated carbon asymmetric supercapacitor fabricated using a polyvinyl alcohol-KOH gel electrolyte showed high energy and power densities of 44 W h kg(-1) and 14 kW kg(-1), respectively. Overall, the corn flake-like NiO nanostructure on nickel foam is an excellent candidate for supercapacitor applications.