In situ growth of NiCo₂O₄ nanosheets arrays on Ni foam for high-performance supercapacitor

The NiCo₂O₄ nanosheets arrays with oxygen vacancies on Ni foam (NiCo₂O₄/NF) hybrid electrode is made utilizing high-pressure hydrothermal synthesis and subsequent heat treatment. Benefitting from the joint contribution of the greater specific surface area, sufficient oxygen vacancies, and unique nanosheet array structure, the NiCo₂O₄/NF electrode exhibits an enhanced electrochemical properties, such as a high specific capacitance of 1452.6 F/g at 1 A/g and prominent cycle stability with a capacitance retention of 98.67% after 4000 cycles. Moreover, the capacitance remains at 591 F/g at 50 A/g, demonstrating better rate capability. In addition, an asymmetric supercapacitor (ASC) was assembled based on NiCo₂O₄/NF//activated carbon (AC). Such an ASC delivers a high energy density of 47.95 Wh/kg at the power density of 750 W/kg and retains Wh/kg at W/kg. The ASC exhibits a preeminent cycling stability with a specific capacitance retention rate of 98.68% of initial capacitance after 25,000 cycles under 80 A/g.