| Many researches in this area of electrochemical supercapacitors have been made focusing on the development of electrode materials that have high specific surface areas and electrochemical properties in suitable electrolytes, such as carbon, transition-metal oxide and conducting polymer. However, carbon suffers from slow deterioration by oxidation and high internal resistance; and it is uncertain to the stability and cycle property of conducting polymer as electrode materials. Many transition-metal oxides are known as excellent electrode materials for supercapacitors with charge-storage mechanisms based predominantly on pseudo-capacitance. Although the ruthenium-oxide system gives very high specific capacitance, it has the inherent disadvantage of high price and toxicity. Therefore, other cheap and environmentally benign transition-metal oxides are thought of as the most ideally substituted electrode materials for supercapacitors.This thesis consists of five chapters. The purpose of the first chapter is to survey the fundamental principles, characterizations and applications of supercapacitors, especially the recent progress of researches on supercapacitors using carbon, transition-metal oxide and conducting polymer as electrode materials in their supporting electrolytes. Based on these information I put forward my purposes and researches to solve existed questions.The second chapter shows preparation and super-capacitive properties of MnO2 and its composite materials. This chapter is divided into four parts.1.Ultrafme manganese dioxide was prepared by oxidation precipitation with potassium persulfate as oxidative reagent under the control of reaction temperature and time. By using electrochemical technique, its specific capacitance reaches over 150F/g.2.Amorphous manganese dioxides were prepared by direct thermal decomposition of KMnO4 at different temperatures. Electrochemical tests indicate that the materials prove to be excellent electrodes for supercapacitors in an unbuffered 0.5mol/L Na2SO4 aqueous electrolyte.A sample decomposed at 550 gives a specific capacitance of 243F/g.3.MnO2 chemically doped with cobalt used as electrode materials for supercapacitors were prepared by chemical co-precipitation method. Results obtained by different electrochemical measurements show that the amounts of Co in samples have great influence on their electrochemical capacities. While measured Co was doped, the electrode has better capacity property, lower impedance and higher utilization, and can be charge-discharged at high current of 40mA.4.MnO2/activated carbon composite electrode materials were prepared by chemical co-precipitation method. The results show that MnO2/activated carbon composite electrode materials have better electrochemical kinetic reversibility and ideal capacitor performance than those of -MnO2 nH2O or activated carbon electrode by CV , a.c. impedance and galvanostatic charge-discharge tests.The third chapter shows preparation and super-capacitive properties of CoAI double-layer hydroxide. It is made up of four parts.1 .Co-A! layered double hydroxides with different ratio of AI to Co have been prepared by chemical co-precipitation method. Electrochemical tests show that Co-AI LDHs as electrode material have typical capacitance . CoAl LDH(AI:Co=l:2) as electrode has a stable structure and good cyclic performance. Specific capacitance of its single electrode attains 400F/g.2.Physical properties of CoAl LDH(AI:Co=1:2) were characterized and discussed by XRD, TEM and IR measurements. The results show that it has layered structure and belongs to hexagonal system and its diameters ranges from 60nm to70nm. Electrochemical tests show that its capacitance changes few after 500 cycles.3.Co-Al LDH was treated by hydrothermal method at 130癈for 16h. Electrochemical measurements show that specific capacitance of single electrode is increased by 15% and its impedance is only tens of m . After 200 cycles its capacitance changes few.4.CoAlLDHs with different ratio...
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