Studies On Carbon Materials And Ruthenium Oxide As Electrode Materials For Supercapacitors

As intermediate systems between conventional capacitors and batteries, supercapacitors have many advantages. While batteries able to store higher energy density than supercapacitors, they deliver less power; suercapacitors can store higher energy density with less delivered power compared to conventional capacitors. Supercapacitors have achieved much attention in many fields, such as mobile telecommunication, information technology, consumerelectronics, aviation& aerospace, military force, and so on. Recently the prospect of supercapacitors with high power densities extends their application to various other novel devices such as hybrid capacitor-battery systems using in the electric vehicle, have been attracting more and more attention throughout the world. Recently, studies on supercapacitors are mainly focused on the preparation of high performance electrode material and electrode.This dissertation carried out following the international foreland research, according to many literature materials. With carbon materials and Ruthenium Oxide as electrode materials for supercapacitors, by integrating various electrochemical and material methods, this dissertation has investigated the material preparation, electrolyte optimization, electrode preparation, capacitive property and mechanism of double-layer capacitance. The main results are as follows:1. Carbon nanotubes array electrodes were prepared by Chemical Vapor Decomposition (CVD) methods in aluminum oxide (AAO) membrane. Carbon nanotubes array, multi-nanotubes and activated carbon have been used as electrode materials for supercapacitor. By investigating electrode preparation and capacitor assembly technology, using cyclic voltammogram and constant current charge/discharge methods, capacitive characteristics of carbon supercapacitor are studied. These researches are the basis of novel electrode materials.2. For the first time, gelatin-based porous carbon bead has been successfully fabricated from gelatin microspheres by means of solidified, carbonized and chemical activation with KOH. The physical properties of gelatin-based porous carbon beads were studied by a t-plot method based on N2 adsorption isotherms. The gelatin-based porous carbon bead activated at 800℃exhibited the largest specific surface area and resulted in the highest capacitance. Carbon/carbon supercapacitors cells assembled with novel electrode materials in 1.0mol/L NEt4BF4/EC+AN electrolyte and aqueous eletrolyte have been studied. The electrochemical properties of gelatin-based porous carbon beads electrode were systematically investigated by using constant-current discharge tests, the results indicated the gelatin-based porous carbon beads electrode was found to have good cycling stability and specific capacitance of 119.8F/g and 202.7 F/g. At the same time, we discussed the activated mechanism of KOH and influence of pore distribution of electrode materials.3. For the first time, Ruthenium Oxide coated carbon micro-coils and RuO2/ gelatin-based carbon beads composite materials were synthesized by simple chemical coprecipitation method. We used SEM and EDX to analyze the configuration of composite materials. The RuO2/carbon micro-coils and RuO2 /gelatin-based carbon beads electrodes were prepared, and button type supercapacitors were assembled in the air. The performance of the different electrode materials was studied by cyclic voltammetry. The electrochemical capacitance of button type supercapacitor tested under constant current charging-discharging. This RuO2/carbon micro-coils composite supercapacitor exhibits a satisfactory performance; the specific capacitance 213F/g is higher than common carbon coil material. And the specific capacitance of RuO2 / gelatin-based carbon beads is 402F/g. Compared with Ruthenium oxide, the big current (140mA/cm2) performance of RuO2/carbon micro-coils and RuO2 / gelatin-based carbon beads electrodes materials obviously improved. The results show that carbon micro-coils and gelatin-based carbon beads are better base materials for RuO2.4. The research on aqueous electrolytes, especially acid and alkaline electrolytes carried out by testing conductivity. Considering the properties of aqueous electrolytes (KOH and H2SO4), we chose the optimized electrolytes system (6mol/L KOH and 2mol/L H2SO4) as supercapacitor aqueous electrolytes. The organic electrolytes were composed of 1mol Et4NBF4 in various mixed solvents ethylene carbonate (EC)/ antrile (AN). The electrochemical behavior of each of the electrolytes was examined by measurements of conductivity and voltage stability. The results exhibit optimal electrochemical behavior when the electrolyte consisted of 1mol/L Et4NBF4 in EC +AN (mass ratio 1:1).