| Electrochemical supercapacitors are new energy storage devices that have high specific capacitance, excellent reversibility and long cyclic performance. In recent years, supercapacitors have become a researching hotspot. As anode material of supercapacitors, manganese dioxide has high specific surface area, excellent electrochemical performance and high specific capacitance. In this regard, the prospect of manganese oxide is very extensive.The effect of technical parameters on structures and electrochemical characteristics of MnO2 was studied using orthogonal test and single factor experiment. Nitrates of La or Co were doped in electrolyte to improve the performance of MnO2 electrodes in preparing process. The components, structure and morphology of MnO2 were characterized using various techniques such as atomic absorption method, field emission scanning electron microscopy and X-ray diffraction. The electrochemical performance of MnO2 was discussed using kinds of measurements such as cyclic voltammetry, galvanostatic charge/discharge and self-discharge testing method.The optimum technical parameters in direct current deposition method were: the reaction time was 30 min, the electrolyte concentration of Mn(CH3COO)2·4H2O was 0.15 mol·L-1, reaction temperature was 40℃and current desity was 0.8 mA·cm-2 .The specific capacitance of MnO2 electrode prepared in this condition was 239.04 F·g-1. The electrode materials were modified by doping proportional compound of La and Co. The results indicated that when n(La):n(Mn+La) = 1.5:10 and n(Co):n(Mn+Co) = 2:10, the specific capacitance of complex manganese dioxide could reach to the highest. The specific capacitances were 267.84 F·g-1 and 271.02 F·g-1, respectively.Manganese dioxide prepared by pulse current deposition was studied using single factor experiment. The results indicated that the electrode had better capacitive characteristics when the pulse frequency was 250 Hz and the duty cycle was 37.5%. The specific capacitance could reach to the highest, which was 311.04 F·g-1. The XRD, FE-SEM and cyclic voltammetry tests indicated that the size of MnO2 by pulse current deposition was smaller than that by direct current deposition. Furthermore, the materials had high specific surface area and better capacitive characteristics.
|
PDF Full Text Request