Supercapacitor performance of porous nickel cobaltite nanosheets
Xin Chen, Rui Xie, Hui Li, Fadi Jaber, Farayi Musharavati, E. Zalnezhad, Sungchul Bae, Kwan San Hui, Kwun Nam Hui
Abstract
Abstract 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 .