Supercapacitor performance of porous nickel cobaltite nanosheets

In this work, nickel cobaltite (NiCo(2)O(4)) nanosheets with a porous structure were fabricated on nickel foam as a working electrode for supercapacitor applications. The nanosheets were fabricated by electrochemical deposition of nickel–cobalt hydroxide on the nickel foam substrate at ambient temperature in a three-electrode cell followed by annealing at 300 °C to transform the coating into a porous NiCo(2)O(4) nanosheet. Field emission scanning electron microscopy and transmission electron microscopy revealed a three-dimensional mesoporous structure, which facilitates ion transport and electronic conduction for fast redox reactions. For one cycle, the NiCo(2)O(4) electrodeposited nickel foam has a high specific capacitance (1734.9 F g(−1)) at a current density (CD) of 2 A g(−1). The electrode capacitance decreased by only approximately 12.7% after 3500 cycles at a CD of 30 A g(−1). Moreover, a solid-state asymmetric supercapacitor (ASC) was built utilising the NiCo(2)O(4) nanosheets, carbon nanotubes, and a polyvinyl alcohol-potassium hydroxide gel as the anode, cathode, and solid-state electrolyte, respectively. The ASC displayed great electrochemical properties with a 42.25 W h kg(−1) energy density at a power density of 298.79 W kg(−1).