Study On Manganese Dioxide As Electrodes Material For Supercapacitor

The purposes of the thesis are to systemically research the inexpensive manganese dioxide as the electrode material which is prepared by liquid deposition method. The physical and electrochemical testing methods such as XRD, TEM, CV, EIS, constant current charge-discharge were employed to investigate the structure and electrochemical performance of the materials. The main results are as follows:The influence to MnO₂ physical and chemical properties was studied on factors of reaction temperature, heat treatment temperature and synthesis routes. The sample synthesized at 80℃showed a better crystalline phase and electrochemical stability but smaller specific capacitance compared to a weaker crystalline phase and electrochemical stability but a bigger specific capacitance of the materials prepared at 30℃. The heat treatment at 400℃could promote the degree of crystallizing but degrade electrochemical performance of the materials. MnO₂ synthesized by add manganese acetate solution to potassium permanganate solution manifested great performance such as smaller particle diameter, uniform grain size and long cycle life compared to the method of reversing the sequence of adding.The composite materials prepared by the liquid deposition method are doped with Tin or iron. Physical property and electrochemical property tests were carried out respectively. The results of XRD and SEM show that the structures of the doped samples don't change. Electrochemical test results show that proper adulteration ratio of Tin and Iron both make performances of the composite materials better. When the molar ratio of Mn to Fe was 50:1,the composite electrodes showed a promising specific capacitance of 288F/g, which is higher than that of the undoped material. Moreover, the composite electrodes exhibited high electrochemical stability and a long cycle life, the specific capacitance of the composite electrodes only had 12.4% loss after 1000 cycles. For the MnO₂ composite electrodes doped Tin, when the molar ratio of Mn to Sn was 20:1, the specific capacitance of the composite electrodes was up to 321F/g, which is higher than pure manganese oxide electrode (279F/g), After 1000 charge-discharge cycles,the specific capacitance stabilized at 256 F/g, exhibiting favorable capacitance retention ability.