Flower-like nickel-zinc-cobalt mixed metal oxide nanowire arrays for electrochemical capacitor applications

The flower-like nickel-zinc-cobalt (Ni-Zn-Co) mixed metal oxide nanowire arrays have been directly synthesized on nickel foam by using a simple hydrothermal method and subsequent thermal treatment. According to the electrochemical characterization, it is demonstrated that the flower-like Ni-Zn-Co oxide nanowire arrays manifest high specific capacitance (776 F g⁻¹) and areal capacitance (1.16 F cm⁻²) at a current density of 2 A g⁻¹. It should also be noted that the Ni-Zn-Co oxide nanowire arrays exhibit long cycle stability (88.9% of the maximum value after 10000 cycles) and good rate capability (retention of 73.8% at 32 A g⁻¹). The assembled aqueous asymmetric supercapacitor shows an energy density of 44.5 Wh kg⁻¹ at a power density of 880 W kg⁻¹. Furthermore, in terms of the analysis results of material characterization and electrochemical performance, the excellent pseudocapacitive performance could be ascribed to the unique flower-like nanowire architecture with high surface areas, rich redox reaction sites, good mechanical and electrical contacts, as well as high conductivities and transport rates for both electrolyte ions and electrons. This study indicates that the flower-like Ni-Zn-Co oxide nanowire arrays could find opportunities in supercapacitor applications.