Abstract
A high-performance supercapacitor based on Ni(OH)2 nanoflakes modified ZnO nanowires (NWs) was developed. The well-aligned ZnO NWs were synthesized by chemical bath deposition, followed by pulse electrodeposition of Ni(OH)2 nanoflakes on the surface of ZnO NWs. The effects of the pulse electrodeposition conditions were systematically investigated. Both the current-on time and current-off time were found to affect the size and interspacing of the nanoflakes, while the deposition cycle number determines the thickness of the Ni(OH)2 nanoflake shell. The ZnO/Ni(OH)2 nanocomposite electrode fabricated under the optimal pulse electrodeposition conditions has exhibited a large specific capacitance of 1830 F/g, a high energy density of 51.5 Wh/kg, a high power density of 9 kW/kg, and ~80 % specific capacitance retention after 1000 cycles. To improve the specific capacitance retention, Mn precursor was added into the deposition solution. The optimal amount of Mn precursor and the pulse electrodeposition conditions were discussed. The resultant ZnO/(Ni, Mn) oxide or hydroxide nanocomposite electrode fabricated under the optimal conditions has exhibited a specific capacitance of 1642 F/g, an energy density of 42.2 Wh/kg, a power density of 9 kW/kg, and 94.7 % specific capacitance retention after 3000 cycles. The high supercapacitor performance combined with using of the low-cost and environmentally friendly materials will make the ZnO/(Ni, Mn) oxide or hydroxide nanocomposite electrode desirable for supercapacitor applications.