Preparation And Performance Of Transition Metal Oxide Electrode Materials For Supercapacitor

Supercapacitor is a new kind of energy storage device whose performance is between dielectric capacitors and batteries. The electrode material is one of the key factors which affects the energy density. With the advantages of high specific capacitance and energy density, low cost and easy preparation, and their micro/nano structures such as grain size and crystal morphology for transition metal oxides such as Co, Ni, it has become the research focus of supercapacitor electrode materials in practical application.In this paper, CO3O4and Co3O4-NiO composites were successfully synthesized by facile chemical precipitation method. The crystal structures and morphologies of materials are characterized by related methods of analysis and testing. The electrode materials of Co, Ni and other transition metal oxides were investigated by cyclic voltammetry, chronopotentiometry, and electrochemical impedance measurements. In addition, the corrosion resistance of the PANI film doped with Co2+was simply researched. The main research contents are as following:(1) The formless CO3O4nanoplate with loose nanostructure has been successfully synthesized in large scale via two steps:preparing precursor and calcinating process. The effect of the structure-directing agent, reaction time and the reaction temperature on the electrochemical properities of Co3O4electrode materials was investigated. It indicates that the capacity of Co3O4nanomaterial prepared with sodium hexametaphosphate as structure-directing agent is851.67F·g-1at the current indensity of5mA·cm-2. Besides, the specific capacitance degradation is only10.05%after250continuous charge-discharge cycles, indicating the excellent electrochemical stability.(2) The Co3O4-NiO composite oxides were synthesized by liquid phase precipitation method of one step using the cobalt salt and nickel salt as raw materials and the mixture of water and alcohol as solvent after calcinations process. The influences of the molar of cobalt and nickel, solvent volume ratio, the precursor heat treatment temperature and a surfactant on the composite oxide electrode materials and specific capacitance were studied. The results show that the Co3O4-NiO composites electrode exhibit a maximum specific capacitance of1832F·g-1at2mA·cm-2under the condition of nco:nNi=(1:1) and Vwater:Valcohol=(1:2). In addition, the electrochemical stability was measured after1000continuous charge-discharge cycles at room temperature and only1.863%was degradated, which shows the excellent electrochemical performance, indicating a kind of promising candidates for supercapacitor.(3) The PANI/Co2+composite film was synthesized by electrochemical method using Co2+as a dopant, and which was characterized by Fourier transform infrared and X-ray diffraction. The influence of Co2+on cyclic voltammetry electrochemical preparation of PANI film and the corrosion resistance of composite PANI/Co2+composite film were investigated. The results suggest the concentrations of Co2+affect the corrosion resistance of the PANI film. The corrosion potential of PANI/Co2+composite film shifts toward the positive direction obviously comparing with the pure and the corrosion current density reduces significantly, which exhibit good corrosion resistance.