Ni–Co–S nanosheets supported by CuCo2O4 nanowires for ultra-high capacitance hybrid supercapacitor electrode

Abstract

Recently, constructing core-shell arrays directly on conductive substrates is proved as a promising strategy for energy storage devices, due to the abundant active sites and fast electrons transport paths. In this work, we design core-shelled CuCo2O4@Ni–Co–S arrays directly on Ni foam substrate by the hydrothermal and electrodeposition processes. The core-shelled arrays can possess the large accessible surface area, fast charge transfer kinetics and the synergistic effect from both components, leading to better electrochemical performances. Consequently, core-shell CuCo2O4@Ni–Co–S arrays can deliver a high specific capacitance of 12.10 F cm−2 (corresponding to 2897 F g−1 mass specific capacitance), and good cycle stability with 82.5% capacitance retention after 8000 cycles of charging and discharging at 20 mA cm−2. In addition, a battery-supercapacitor hybrid device made of CuCo2O4@Ni–Co–S and activated carbon displays a high energy density of 0.65 mWh cm−2 at 32 mW cm−2 power density, and the capacitance loss less than 20% (~83.6%) after 8000 cycles.