Preparation Of Core-shell Structure Composite Materials Of C@MnO₂ And Their Electrochemical Performance

environmental friendly and sustainable energy storage systems are heavy demanded owing to the springing up of portable electronic products. supercapacitor in combination with the advantages of conventional capacitor to batteries has attract a significant mount of attention due to its rapid charge and discharge, excellent cycle life, high power density, energy conservation and environmental protection etc. supercapacitor can be categorized as electrochemical double layer capacitors(EDLCs) and pseudo-capacitors(PCs). in this thesis with method of chemical deposition and reflux, AC/MnO2, C/MnO2, PGC/MnO2 composites with characteristics of both these two kinds of supercapacitor are made. the materials’ s morpHology, nanostructures and properties, have been characterized by Fourier transforminfrared spectroscopy(FT-IR), X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and nitrogen sorption isotherm measurement, cyclic voltammetry(CV), constant galvanostatic charge-discharge(GCD), impedance spectroscopy(EIS) techniques, the research contents of this paper are as follows:1. At first, using the hydrothermal method, with β-cyclodextrin as carbon sources prepared hydrothermal carbon nanospHeres, the activated carbon can be obtained with further carbonization and activation in air. Afterwards, using the chemical deposition method, because of the reaction between H2O2 and MnSO4, a layer film of MnO2 deposited on the activated carbon surface evenly. in 6 M KOH electrolyte, At a current density of 0.2 A g-1, the specific capacitance of AC/MnO2 composites is as high as 193 F g-1, higher than the carbon and manganese dioxide, its comprehensive performance is better than the separate materials.2. With β-cyclodextrin as carbon source, carbon precursor are prepared by hydrothermal method, afterwards, C/MnO2 composites are obtained due to the redox reaction between KMnO4 and the carbon precursor. Through orthogonal experiment, the thesis discusses the influence of the raw material ratio, pH, and the temperature on this chemical reaction. the results show that: under what conditions is the best performance, and in 6 M KOH electrolyte, under the current density of 0.2 A g-1, however, the specific capacitance of the specific capacitance of the composites with up to 217 F g-1, how much energy density and power density are respectively, obviously, C/MnO2 results in better performance.3. Carbon precursor are prepared with hydrothermal method, then with ZnCl2 and Ni(CH3COO)2·4H2O respectively as chemical activator and graphitization catalysts, chemical activation and partial graphitization process are at the same time. the best condition of preparation of partial graphitized carbon is discussed, the preparation of PGC/MnO2 is under certain conditions when the partial graphitized carbon react with KMnO4, partial graphitized carbon improves the conductivity of manganese dioxide, and because the PGC surface is covered by a layer of manganese dioxide thin films, the performance of PGC/MnO2 composites is significantly increased, and calculate the specific capacitance of the composites is as high as 131 F g-1, energy density is up to 59.1 Wh kg-1 respectively, preparation process of this material is simple and novel method, is of high quality material of super capacitor is optional.