Preparation And Capacitive Performance Of Nickel Hydroxide Composite Materials

In this paper,NiCo2O4/Ni(OH)2 and rGO/Ni(OH)2/Co(OH)2 composites were prepared by hydrothermal method and electrochemical deposition method,respectively.The structures of composites were characterized by Fourier infrared spectroscopy(FT-IR),X-ray powder diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)and the morphology of composites were observed by Scanning electron microscopy(SEM).Besides,the capacitive properties of the composites were studied by cyclicvoltammetry(CV),chronopotentiometry(CP)and electrochemical impedance spectroscopy(EIS)measurements.The composite NiCo2O4/Ni(OH)2 was synthesized by hydrothermal method using nickel foam(NF),KOH and Co(NO3)2 as raw materials.NF in the solution was not only the substrate,but also as the nickel source and reductant in the redox reaction.It was found that the specific capacitance of the composite was 2474.1 F g-1 when the current density was 1 mA cm-2 and still retained 1864.5 F g-1 when the current density was up to 100 mA cm-2,indicating that the NiCo2O4/Ni(OH)2 compound has a good rate performance.The specific capacitance maintained 86%of its initial after 2000 cycles at the current density of 1 mA cm-2,implying the excellence cycling stability.These excellent electrochemical properties were exhibited due to the special composition of the complex and the fact that the foam nickel was used as a substrate,which enhanced its conductivity.In addition,GO was successfully obtained by modified Hummers method and the rGO/Ni(OH)2/Co(OH)2 composite was prepared by electrochemical deposition which Co(NO3)2,Ni(NO3)2 and GO were used as raw materials.The optimal experimental condition was obtained by orthogonal experiments and single factor variables analysis.The specific capacitance of the composite electrode was highly up to 1894.1 F g-1 at the current density of 1 mA cm-2 and the specific capacitance maintained 88%after 2000 cycles.An asymmetric capacitor was assembled by using rGO/Ni(OH)2/Co(OH)2 as positive electrode and rGO as negative electrode.Its specific capacitance is 259.8 F g-1 at the current density of 1 mA cm-2.After 2000 times of charging and discharging,the capacitance remained 81%of its initial.