Preparation Of Manganese Dioxide And Study On Its Properties As Electrode Material In Electrochemical Capacitors

Electrochemical capacitors (ECs) are new kind of energy storage devices with remarkable advantages. Electrode material is an important factor that affects the ECs performance, among these, MnO2 appears to be a promising material. Manganese dioxide was prepared using sol-gel method, and doped with La using chemical precipitation in this article. We planned to gain MnO2 electrode material with high specific surface area, excellent electrochemical performance, and high specific capacitance.The effect of technical parameters on structures and electrochemical characteristics of MnO2 was studied using different experimental method, such as orthogonal test, single factor experiment and contrast analysis. And the structure and appearance of MnO2 were characterized using various techniques such as chemical analysis, scanning electron microscopy(SEM) and X-ray diffraction(XRD), and the electrochemical performance of MnO2 was discussed using kinds of measurements such as cyclic voltammetry, constant charging/discharging and local action testing method.The optimum technical parameters in sol-gel method are:n(citric acid)∶n(manganese acetate)=0.5∶1, C0=0.1 mol·L-1,pH≈6,the reactive temperature is 60℃, sintered at 350℃for 3 hours and acidificated by H2SO4 at high temperature. The prepared MnO2 exhibited relatively lesser granularity, high specific surface area, eminent capacitive characteristics, excellent cycle life, and specific capacitance value was 159.5 F·g-1 at a discharging current of 5 mA. With the increase of discharging current, specific capacitance appreciably decreased, and the performance of discharging at high current needs improving. MnO1.88 was obtained by chemical precipitation under the condition of not adjusting pH value. MnO1.88 has better electrochemical performance than MnO2. Lanthanum doped manganese dioxide was prepared, and lanthanum existed inthe crystal lattice of manganese dioxide as ions. Manganese dioxide electrode existed preferable capacitive characteristics and power performance after adulteration. Adulteration with different proportion had great effect on the electrochemical performance of manganese dioxide. And when the proportion was 5∶1 of Mn∶La(molar ratio), manganese dioxide had better capacitive characteristics. With the increase of charging/discharging current, the specific capacitance of capacitor declined slowly, thus the electrode existed better discharging performance at high current. And the cycle life also improved after doped with lanthanum.