Synthesizing Ni-based ternary metal compounds for battery-supercapacitor hybrid devices with and without using nickel precursors

Hydrothermal method is widely used for synthesizing Ni-based metal oxides on Ni foam as the battery-type materials. The Ni ions for synthesizing Ni-based metal oxides can be obtained from the Ni precursor and the Ni foam, but the effect for the Ni ion source on the physical and electrochemical properties of the Ni-based metal oxides are still not clear. This work investigates the effects of the Ni precursor in the hydrothermal solution for synthesizing Ni-based metal oxides on morphology of metal oxides and electrocapacitive performances of the battery-type electrodes. The same sort of the Ni-based ternary metal oxides synthesized with and without adding Ni precursor in hydrothermal solution present very different morphologies and electrocapacitive features, indicating the different amounts and sources of Ni ions play important roles on the growth of the Ni-based metal oxides. The battery-supercapacitor hybrid device composed of the nickel cobalt molybdenum oxide electrode prepared with Ni precursor and the nickel cobalt copper oxide electrode prepared without Ni precursor respectively show areal capacitances of 126.2 and 917.3 mF/cm ² corresponding to the area capacities of 63.1 and 382.2 mAh/cm ² , voltage windows of 1.8 and 1.5 V, as well as the maximum energy density of 21.9 Wh/kg at power density of 3.45 W/kg and the maximum energy density of 0.70 Wh/kg at power density of 13.38 W/kg. This work clarifies the function of Ni foam and Ni precursor in the hydrothermal solution for synthesizing Ni-based metal oxides and provide novel synthesizing concept to design efficient materials for energy storage devices.