Study Of The Synthesis Of Co₃O₄Nanocomposite And Its Supercapacitive Performance

In recent years, supercapacitor which is a kind of novel and green energy storage device with high power density and long cycle life, has been widely investigated in academy and industry. Because of low cost, natural abundance, environmental safety and excellent electrochemical properties, cobalt oxide is found to be one of most promising electrode materials of supercapacitor. However, the charge transfer on interface is limited due to the poor electronic conductivity of Co3O4and the difficulty in the penetration of electrolyte into the microstructure of electrode. Therefore, the incorporation with carbon materials which are high electronically conductive, or the synthesis of microstructure which facilitates the transfer of ion, are both the method which improve the electrochemical performance of Co3O4electrode. In this paper, we study the Co3O4supercapacitor electrode materials such as Co3O4nanoplates/graphene composites and Co3O4hollow nanospheres. The main contents are as follow:A series of Co3O4nanoplates/graphene composites are fabricated by a hydrothermal-thermal decomposition method. The phase and morphology of as-prepared composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectra, and the electrochemical property are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS), the effect of graphene mass ratio on specific capacitance is also studied. The results show that The Co3O4nanoplates/7.0%GNS composite shows the specific capacitance of703.4F/g at0.625A/g and385.1F/g at12.5A/g in2M KOH aqueous solution, respectively. The composite exhibits excellent cycling stability with the18.7%specific capacitance increased at1.25A/g after1000cycles. By the comparison of the specific capacitance of Co3O4nanoplates/graphene composites with the graphene content of4.1,7.0and12.3%, we conclude that the composite with the graphene content of7.0%results in the maximum improvement of specific capacitance.The Co3O4hollow nanospheres are prepared by hydrothermal-calcination method, using carbonaceous nanospheres as template. Through the research on the morphology and electrochemical performance of this material, we discuss the effect of hollow nanostructure on the property of electrode material. The results indicate that the hollow nanostructure possess large electrochemical active surface and facilitate the fast diffusion of ions in electrolyte, which come about the enhancement of capacitive property of electrode. The Co3O4hollow nanospheres show the specific capacitance of502.3F/g at0.25A/g. Moreover, The Co3O4hollow nanospheres show good cyclic performance with capacity retention of90.6%after1000cycles.