Large-scale synthesis of uniform NiCo2O4 nanoparticles with supercapacitive properties

• Large-scale synthesis of NiCo2O4 nanoparticles about 20 nm in size is developed.
• The NiCo2O4 nanoparticles are used as electrode material for supercapacitor.
• The as-prepared NiCo2O4 sample exhibits good supercapacitive properties.

A facile ball-milling process followed by a thermal treatment is developed for the large-scale synthesis of ultrasmall NiCo2O4 nanoparticles (<20 nm). The uniform NiCo2O4 nanoparticles exhibit high specific capacitance of 720.04 F g−1 at 1 A g−1 and 477.36 F g−1 at 20 A g−1, respectively. The specific capacitance retention rate reaches 97.3% after 2000 cycles, demonstrating its excellent cycling stability. The superior electrochemical performance is mainly attributed to the ultrasmall nanosize, which provides large electrode–electrolyte contact area and benefits electrons and ions transportation during the redox process. This method of preparing NiCo2O4 nanoparticles is very simple, yet effective, and it could be applied in the large-scale synthesis of other high-performance binary metal oxides electrode materials for electrochemical capacitors.