The Research Of Supercapacitor Based On Carbon Nanotube Composite Materials

Supercapacitors has attracted broad attention of global scientific research workers due to it’s advantages of high specific capacitance, high power density, green environmental protection and long cycle life. The working electrode is the key part to effect the performance of supercapacitor, and electrode performance is decided by the electrode materials and preparation technology. We concentrated on the preparation of electrode material with high specific capacitance in this thesis, several electrode materials, such as manganese oxide, carbon nanotube/manganese oxide, cobalt oxide and carbon nanotube/cobalt oxide electrode materials were developed by using different methods. After analyzing the phase of material composition and characterization of surface topography through X-ray diffraction, electron scanning electron microscopy(SEM), X-ray energy spectrometer test means, and testing properties of the prepared material as electrochemical supercapacitor through the timing potential method and cyclic voltammograms test method, we got some important conclusions as follows:Firstly, we investigated the temperature influence on the valence state, the crystal surface morphology and the electrochemical properties of system production by Mn SO4-KNO3 molten salt reaction. The specific capacitance of Mn O2 material was 57.7% higher than that of Mn3O4 material. The internal resistance of the Mn O2 materials and conductive performance has improved when CNTs were added in Mn O2 materials, and the specific capacitance of CNTs/Mn O2 composite electrode was 141.2 F/g, increased by 51.5% than the Mn O2 electrode.Secondly, we analyzed composition, morphology and electrochemical performance of Mn O2 material synthesized by hydrothermal method at different temperature, the results showed that crystallization degree of production enhanced with the rise of temperature in a range of temperature, and the specific capacitance reached 97.7 F/g when Mn O2 was acicular synthesized at the temperature of 150 ℃. The specific capacitance of CNTs/Mn O2 composite electrode synthesised by hydrothermal achieved 181.2 F/g, it increase by 85.5% than pure Mn O2 electrode synthesised by hydrothermal, and 28.3% than CNTs/Mn O2 composite electrode made by molten salt growth method as well.Thirdly, the specific capacitance of Co3O4 electrode prepared by hydrothermal method was 93.5 F/g, which was tested in the three electrode system with 6 mol/L KOH electrolyte at 10 m A/cm2 current density. The prepared CNTs/Co3O4 composites material made by hydrothermal, in which CNTs were added and CTAB was used as activator in Co3O4 precursor reaction system, presented that cobalt oxide was coated on carbon nanotubes with uniform distribution, rich space and good dispersion. The specific capacitance of CNTs/Co3O4 composites electrode achieved 179.1 F/g at 10 m A/cm2 current density, 91.5% higher than the Co3O4 electrode.Finally, cyclic voltammetry tests indicated that the obtained specific capacitance of the prepared Mn O2 electrode, Mn3O4 electrode and CNTs/Mn O2 was mainly from adsorption/desorption electron. While the prepared Co3O4 electrode and CNTs/Co3O4 electrode got the specific capacitance was mainly through redox reaction.