Hydrothermal process fabrication of NiO–NiCoO2–Co3O4 composites used as supercapacitor materials

Abstract

A composite consisting of Co3O4, NiCoO2 and NiO is prepared by a simple and easy hydrothermal method followed by calcining at 300 °C. The composition, morphology and microstructure of NiO–NiCoO2–Co3O4 composites are examined by X-ray diffraction, field emission scanning electron microscope and transmission electron microscopic. The electrochemical performances of NiO–NiCoO2–Co3O4 composites are characterized by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy in 3 M KOH electrolyte. The results of electrochemical measurements show that the NiO–NiCoO2–Co3O4 composites exhibit a high specific capacitance of 990 and 580 F/g at the current densities of 1.0 and 10 A/g, respectively. About 50% of the maximum specific capacitance can still be retained after 1000 continuous CD cycles at 10 A/g. It reveals a great potential of NiO–NiCoO2–Co3O4 composites used in high-performance energy-storage systems.