Modification And Electrochemical Performance Of Activated Carbon For Supercapacitor

Supercapacitors are promising energy storage devices, the performances of which are between traditional capacitor and secondary battery. Due to their large energy density, high power density, fast charge and discharge properties, long cycle life, zero pollution and many other advantages, supercapacitors are applied in many fields, such as daily life, science and technology, and national economy. Supercapacitors have gained the focus of many countries. The electrode material is one of the key factors influencing the performance of supercapacitor. As activated carbon has the superiorities of rich sources, high specific surface area, low cost and stable electrochemical performance, it is the crucial research object all the time.In this thesis, activated carbon has been modified mainly from two aspects, including the conductive agent and AC/MnO2 composite electrode materials. X-ray diffraction, scan electron microscopy, transmission electron microscopy, nitrogen adsorption/desorption are used to characterize the morphology, structure, and composition of the electrode materials. In addition, the electrochemical performances of the electrodes are examined with cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy. The experimental results are as follows:(1) The research of exfoliated graphite when it is used as conductive agent instead of acetylene blackFlake graphite was chosen as the raw material in this dissertation. The High Shear Disperse Homogenizing Emulsification Machine for Laboratory was used to exfoliate it with different times. According to the results, its crystallinity was reduced, the specific surface area was increased and electrochemical performance was enhanced after flake graphite was exfoliated. Particularly, flake graphite exfoliated six hours(S6) owns the best performance as the specific capacitance of S6 is 99F/g, which is double of the raw material.Then S6 and acetylene black were added to the activated carbon using as conductive agent respectively. The result indicated that the electrochemical performance with S6 was better, and the best content is 20%.(2) The research of AC/MnO2 composite electrode materialsIn order to get the AC/Mn O2 composite electrode materials, the TF-B520 activated carbon was used as the raw material to restore KMnO4. Then the AC/MnO2 composite electrode materials were made as electrodes to be tested in the electrolyte of 1mol/L LiPF6/PC and Li2SO4 aqueous solution, respectively. The results revealed that the AC/MnO2 with 12% MnO2(AC/MnO2-2), showed the best electrochemical performance. Additionally, the electrochemical window was wider, the energy density was larger, and the specific capacity was less when AC/MnO2-2 was tested in 1mol/L LiPF6/PC. However, the electrochemical window was narrower, the energy density was less, and the specific capacity was bigger when it comes to Li2SO4 aqueous solution..