Core-shell structured Co3O4@NiCo2O4 nanowires on nickel foam for supercapacitors

As newly developed energy storage devices, high-performance supercapacitors are expected to have large energy densities and it is urgent to design and fabricate novel electrode materials with high capacity and good stability. Core-shell structured hybrid films of Co3O4@NiCo2O4 nanowires were deposited on nickel foam as current collector in this work, different from previously reported assembly manner. The pre-formed NiCo2O4 nanowires on nickel foam as core can serves as conducive paths for the shell material of Co3O4 nanosheets. Since two metal oxides are derived from metal hydroxides by annealing, both components show porous characteristics, benefiting for the diffusion and transportation of electrolyte. Electrochemical measurements demonstrate that the hybrid film has a higher specific capacitance about 995F g(-1) at 1 A g(-1) than both Co3O4 and NiCo2O4 due to the synergistic effect between two materials, leading to a smaller resistance. An asymmetric cell using activated carbon as negative electrode and the hybrid film as positive electrode delivers an energy density of 36.8 Wh kg(-1) at 425 W kg(-1) in 1.65 V, showing large potential for energy storage.