Electrode Preparation And Nanogate Carbon Materials For Carbon-based Supercapacitors

Carbon materials are widely used as electrode materials for supercapacitors due to the stability, easy availability and low-cost of raw materials. The core part of supercapacitor is the electrode. The electrode material affects its electrochemical properties in a large scale due to its structure as well as the process of preparation. In this work, two aspects were mainly concerned: the preparation techonoly of electrodes was studied, and a novel carbon material was made for use in supercapacitors.Rolling and membrane-pressing methods were applied for electrode preparation. The EIS results told that the resistance was lower when membrane-pressing method was used with conducting layer on aluminum-current collector than that of rolling method.Two kinds of activated carbon were tested. YP-D was higher in pore volume than PW15 according to BET analysis, and its meso-pore content was higher, leading to better capacitance performance.The content of conductor in electrodes was studied. The resistance got lower with the increasing content of conductor in the range of 2.5-10(wt) %. The resistance was highest with lowest capacitance with the conductor content of 2.5%. The resistance was reduced to the lowest level when the content was 10%, but its capacitance and power density were lower than that of 5%.The electrode resistance increased with the increasing content of PTFE in the addition range of 6-10(wt) %. The supercapacitor capacitance was highest with content of 8(wt) %.Et4NBF4/AN and Et₄NBF₄/PC were employed to see the effects of electrolyte on the performance of supercapacitors. The power density was better in Et4NBF4/AN.The nanogate carbons were prepared by KOH activation using raw petroleum coke as precursor. The effect of post-dealing methods by N2 sweeping and H2O2 oxidation on the pore structure, surface properties and capacitance performance of nanogate carbons was investigated. The oxygen content on surface was reduced after the nanogate carbon was swept by N2, resulting in longer cycle life. While oxidation damaged its cycle performance. The nanogate carbons can work under the voltage of 3.5 V normaly, and its high capacitance was caused by electrochemical activation in the first charging process. The nanogate carbons with N2 sweeping at 900℃showed a high capacitance of 136.7F/g with a surface area of 61m2/g, leading to high energy density of 58.1Wh/Kg.