Preparation And EDLC Applications Of Mesoporous Carbons With High Specific Surface

The purpose of this dissertation is to prepare carbon materials which can be used as electrode materials for high power density electric-double-layer capacitor (EDLC). On the base of reviewing the development of electrochemical capacitor and its electrode materials and electrolytes in detail, preparation of mesoporous carbons with high specific surface and their electric-double-layer capacitance performance were systematically studied.A novel polymer chemical blend and carbonization method, in which thermally unstable polyethylene glycol (PEG) with organic monomers, resorcinol (R) and formaldehyde (F), were dissolved together, was brought forward to prepare mesoporous PEG-RF carbon xerogels for the first time. The mechanism of pore formation and the influence of preparation conditions on the pore structure of carbon xerogels were studied. The results indicated that micro phase separation structure of mixed PEG-RF organic xerogel and thermal unstability of PEG contributed the special mesoporous structure of PEG-RF carbon xerogels together. Pore structure of carbon xerogels can be tailored effectively by modify the preparation conditions.The electric-double-layer capacitance performance of PEG-RF carbon xerogels in 30wt% H2SO4 was investigated and their preparation conditions were optimized. Carbonization temperature of carbon xerogels used for EDLC could not be lower than 1000C and their high current charge/discharge performance was effected by their pore size distribution. In aqueous EDLCs, optimized PEG-RF carbon xerogel showed a capacitance as high as 215 F-g-1 and its capacitance still sustained 160 F-g-1 when the charge/discharge current increased 1000 times, proving that PEG-RF carbon xerogel had an excellent high rate capability and was a suitable material for the fabrication of EDLC with high power density. Its maximum specific energy and power could reach 4.9Wh-kg-1 and 38 kW-kg-1, respectively. In organic electrolyte EDLCs, the maximum specific energy and power of optimized PEG-RF carbon xerogel were MWh-kg-1 and 22kW-kg-1, respectively.A simultaneously synthetic template carbonization method (SSTCM), where tetraethoxy silane (TEOS) was used as the source of silica template and resorcinol-formaldehyde (RF) gel as the carbon precursor, was first brought forward toprepare mesoporous carbons with controllable pore structure. The results suggested that the tunable silica template synthesized simultaneously with the carbon precursor polymer resulted in the controllable mesoporous structure of the resultant SSTCM carbons. It was found that pore structure of SSTCM carbons strongly depended on the preparation conditions. BET surface and pore size distribution of SSTCM carbons were in the range of 400 ~ 1300 m2-g-1 and 5-10 nm, respectively. The relative formation rate of silica template and RF gel was influenced by the preparation conditions which resulted in the different pore structure of SSTCM carbons.Electric double layer capacitance performance of SSTCM carbons were studied in 30wt % H2SO4 and organic electrolyte, respectively. In aqueous EDLCs, the maximum specific energy and power of SSTCM carbons showed as high as 6Wh-kg-1 and 33kW-kg"1, respectively. In organic electrolyte EDLCs, the two values were 25Wrrkg"' and 21kW-kg"'. SSTCM carbons also showed excellent high rate capability that made them promising materials for the application of high power density EDLC.Outsourcing microporous carbons and mesoporous carbons prepared by us were chosen to investigate the influence of pore structure on the electric double layer capacitance performance of carbon materials. By resolving the ac impedance spectroscopy of EDLCs, it was found that different pore structure of carbons made for the difference of "time constant" of EDLCs which determined the power characteristics of capacitors to a great extent. Mesoporous carbon EDLCs have lower "time constant" than microporous carbon EDLCs. Thus, the former had more excellent power performance and that behavior characteristics of the mesoporous carbon electrodes...