The Study Of Supercapacitor Electrodes Using Nano-Carbon Materials

This dissertation studies nano-carbon materials preparation processes, structural performances and applications in super-capacitors as the electrodes. Ttransmission electron microscope(TEM), scan electron microscope(SEM), X-ray diffraction (XRD), light microscope and N₂ adsorber have been used to characterize the materials, and their electrochemical performances have been studied by the cyclic voltammogram curves, galvanostatic charge-discharge curves and impedance spectrum.Two catalyst precursors LaNiO₃ and La₂NiO₄ were prepared by citric acid complexometry. Two kinds of carbon nanotubes were prepared by chemical vapor deposition method. The TEM results indicated that the inner diameters of carbon nanotubes were 25-30nm and 10-15nm respectively. The specific surface areas of two kinds of carbon nanotubes were detected by N₂ adsorber, the result showed that the specific surface area, total capacitance, mesopore capacitance and average pore diameter of carbon nanotubes prepared by catalyst precursors La₂NiO₄ was bigger than that of carbon nanotubes prepared by catalyst precursors LaNiO₃. They were used as electrode materials and electrochemical super-capacitors were assembled. In organic electrolyte, the capacitances were 25.0F/g and 35.0F/g respectively. Equivalent series resistance of carbon nanotubes prepared by catalyst precursors La₂NiO₄ was small.Carbon nanotubes doping zinc oxides were applied as electrode materials. The capacitance changed from 11.6F/g to 23.9F/g. The reversibilities of super-capacitors were fine, and circulation performance was steady as the electrode materials without zinc oxides.The preparation process of carbon nanotubes film electrode was simple via electrospinning technology. The thickness of electrode could be controlled. There was not agglutinant in electrode. The TEM and light microscope results indicated this kind of electrode had smooth surface and no cracks. Compared to the film electrode via common daubing technology, the capacitance increased from 25.0F/g to 32.0F/g, and electrochemical performances had been improved.Activated carbonfibres were activated by steam in 800℃. The specific surface area of activated carbonfibre changed from 316.34m²/g to 1809.32m²/g.The total mesopore capacitance increased from 0.169m³/g to 0.811cm³/g. The mesopore capacitance of activated carbonfibre was twice more than that of original carbonfibre. The electrochemical capacitances of activated carbonfibres were investigated by means of cyclic voltammetry and galvanostatic charge-discharge technique. The capacitance increased from 47.3 F/g to 91.05F/g, and the capacitance increased with activation time prolonging.