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• NiCo 2 O 4 nanosheets rich in oxygen vacancies were synthesized by a simple solvothermal method. • NiCo 2 O 4 nanosheets rich in oxygen vacancies exhibit an excellent cycling and rate capability. • Oxygen vacancies promote the transfer of zinc ions and enhance the charge-discharge capacity. [Display omitted] Aqueous zinc-ion supercapacitors are a new type of energy storage device possessing high energy density, high safety, long service life, and abundant raw materials, which have attracted attention toward research. In this paper, NiCo 2 O 4 nanosheets rich in oxygen vacancies were used as the cathode material for a novel aqueous zinc-ion supercapacitor. The aqueous zinc-ion supercapacitor device showed excellent electrochemical performance with a high specific capacity of 122.5 mAh/g at a current density of 1 A/g. The specific capacity of discharge at a current density of 10 A/g was found to be 72.6 mAh/g, along with a capacity retention rate of 59.3%. The reduction of NaBH 4 enhanced the content of oxygen vacancies in the materials, which facilitated the enhancement of the conductivity and electrochemical properties of the materials. The high energy density and high multiplier performance of the aqueous zinc-ion supercapacitors showed potential for wide applications in portable electronic products and smart devices. [ABSTRACT FROM AUTHOR]