Active sites-induced decoration of nickel hydroxide nanosheets on copper oxide nanocubes as electroactive material of battery supercapacitor hybrids

Battery supercapacitor hybrids (BSH) comprising battery and supercapacitor-type electrodes can attain high energy/power densities and long cycle life. Copper oxide is regarded as a promising battery-type active material, due to low-cost, high chemical stability and good electrochemical properties. However, poor electrical conductivity and insufficient active sites should be improved to attain high energy storage ability. In this work, a novel battery-type material composed of Ni(OH)2nanosheets decorated on Cu2O cages is synthesized via a facile solution process for the first time. Less deposition of Ni(OH)2leads to sparse distribution on Cu2O cages, and full coverage of Ni(OH)2is achieved via depositing four Ni(OH)2layers on Cu2O cages. The largest specific capacitance (CF) of 389.1 F/g is achieved at 20 mV/s for the optimized Ni(OH)2and Cu2O (Ni(OH)2@Cu2O) composite, while the Cu2O electrode shows a smaller CFvalue of 79.7 F/g. Coating Ni(OH)2on Cu2O can induce active site formation and enhance electrical conductivity. The Ni(OH)2@Cu2O positive electrode and the active carbon negative electrode are used to assemble a BSH, which presents a maximum energy density of 4.09 Wh/kg at 500 W/kg and excellent cycling ability with CFretention of 70% and Coulombic efficiency higher than 97% after 10,000 charge/discharge cycles.