Preparation And Properties Of The Supercapacitors Based On Metal Oxide

Super-capacitor is called electrochemical capacitor as well, which becomes a promising energy storage device because of its large charge/discharge efficiency, high power density, long cycle life and so on. It is attracting the attention of researchers with its broad application in mobile communication, electric car, electronic devices and aerospace sectors.At the present, most of the researches focus on the researching of new electrode materials. It has become the hot research topic that the investigation of metal oxides as electrode materials for their high specific capacity and energy density compared to carbon-based materials and conducting polymer materials. Although the ruthenium oxide has the best electrochemical performance among the oxide electrode materials, it is not suitable for large scale commercial application because of its high cost. It is the primary task to found new materials as electrochemical active materials for high-powered super-capacitor. In our work, we have studied the preparation and electrochemical properties of nano-cobalt oxide and tin oxide. At the same time, we have carried out the research on the application of these oxides in super capacitor. The specific research contents of this paper are as follows:（1） The preparation and application of Co₃O₄/MWCNTs composite materials are given in the second chapter. Nano Co₃O₄ is grown on multi-walled carbon nanotubes with a simple low cost thermal method. The multi-walled carbon nanotubes were activated in the concentrated nitric acid for the loading of functional groups. So the cobalt ions could be effectively absorbed on the walls. We used scanning electron microscopy（SEM） to characterize the surface morphology of the electrode samples, X ray diffraction（XRD） to characterize the crystal structure of the sample, thermal gravimetric analysis（TG） to characterize the Co₃O₄ loading. The electrochemical properties of the electrodes were tested through the cyclic voltalmmetry（CV）, charge /discharge method and AC impedance method. The results showed that the discharge specific capacitance of the composite material is up to 273 F/g in 6.0 mol/L KOH solution when the scan rate is 0.5A/g. The electrochemical performance has been significantly improved compared to pure multi walled carbon nanotubes and pure cobalt oxide.（2） Porous Sn O₂ hollow nanotubes were prepared using Mn O₂ as the template. Mn O₂ Nanorods were prepared by hydrothermal method. The SEM of the prepared Mn O₂ nanorods showed a uniform distribution which provided a fine templet for the preparation of porous hollow Sn O₂ nanotubes. Hollow Sn O₂ nanotubes were prepared through hydrothermal method. The samples were analyzed by XRD and SEM. It was found that hollow Sn O₂ nanotubes were prepared in this experiment. The sample shows tubular structure and no other impurities. Furthermore, the sample has very large specific surface area. At the current density of 0.25 Ag-1, the discharge specific capacity is up to 302 F/g indicating that the prepared hollow Sn O₂ nanotubes have excellent electrochemical performance.（3） The preparation and electrochemical properties of hollow nanosphere Sn O₂ are explored. The glucose was uses as the template for the synthesis of hollow nanosphere Sn O₂. XRD spectra confirm the formation of Sn O₂. The SEM shows that the prepared Sn O₂ are hollow spheres, the diameter of the ball is between 200 nm and 300 nm. The electrochemical performance test showed that the specific capacity is up to 175F/g when the current density is 0.1Ag-1.