Study On Electrochemical Capacitor Of Manganese Dioxide

The purposes of the dissertation are to systemically research the electrochemical performances of manganese dioxide with different crystal configuration by means of the inexpensive manganese dioxide as the electrode materials of electrochemical capacitors. TG-DAT, XRD, XPS, SEM and electrochemical methods have been used to analyze material preparation, structure, capacitance characteristic, properties of electrode material and mechanism of forming pseudocapacitance. Their batter electrochemical performances were confirmed by the experiment of charge/discharge, CV analysis. α-MnO2 was synthesize by the low temperature solidstate reaction of manganese acetate and sodium hydroxide. The possibility of the reaction was analyzed by TG-DAT, the process was monitored by means of XRD, and the elements were identified by XPS. Two types of electrochemical capacitors have been assembled, which were symmetric and hybrid capacitors. When potassium hydroxide (8mol/L) was used as electrolyte, their special capacitance can reach 157F/g and 184F/g(500mA/g current density), respectively. The voltages of self-discharge after 24 hours were 0.630V and 0.476V. The residual capacities after 1000 cycles were 4.4F and 4.5F, respecially, when activated carbon electrode material was applied to negative electrode, working voltage of the capacitor can be enhanced, and high capacity and excellent characteristic of high power discharge were attained. The CV curves have showed bismuth/lead modified manganese dioxide can improve the capacitive characteristic, restrain appearance of manganomanganic oxide, and improve electrochemical performances of capacitors, for example, special capacitance, self-discharge, and cycling life were batter than manganese dioxide without modified.Under different pH value, and the mixture of and MnOOH were attained by reducing potassium permanganate with manganese acetate. The electrochemical performance of former was batter than the later.Manganese carbonate has been prepared by the low temperature solidstate reaction. Subsequently, γ-MnO2 was attained by Manganese carbonate heated at 500 Celsius temperature scale. After EMD andγ-MnO2 modified by iron oxide red, special capacitance can be reached to 256F/g and 328F/g in potassium hydroxide resolution (1mol/L ).The effect about assembly method of manganese dioxide electrochemical capacitors on their electrochemical capability has been researched systematically, and the capability of electrochemical capacitor stack in series or in parallel configuration has been discussed.