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The Preparation And Modification Of Calcium Carbide-derived Carbon For The Application Of Supercapacitors

Posted on:2011-02-23Degree:MasterType:Thesis
Country:ChinaCandidate:L P ZhengFull Text:PDF
GTID:2132330332464264Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
Supercapacitor is a new device for electric energy storage, because they combine the advantages of the high specific power of dielectric capacitors and the high specicfic energy of rechargeable batteries. Besides, they can work in wide temperature range of -20℃-60℃, and the materials are friendly to environment. So, supercapacitors have played an increasingly important role in power source applications such as hybrid electric vehicles and short-term power sources for mobile electronic devices. Electrode material is a key component of the supercapacitor and it determines the performance of supercapacitor. The research and development of electrode materials has been a hot topic in the field in recent years. In this study, we synthesized calcium carbide-derived-carbon (CCDC) by one-step technique at lower temperature. Then we modified the CCDC with HNO3,PANI,urea and melamine, in order to improve its structure and electrochemical performance.In this study, CCDC was synthesized from cheap CaC2 in a freshly prepared chlorine environment at 400℃. In order to improve the surface structure and electrochemical performance of CCDC, we modified it wih 6 M HNO3 and studied by SEM,TEM,FTIR and cyclic voltammetry, galvanostatic charge-discharge respectively. the results showed that the modification caused a slight enhancement in specific surface area and the increase of oxygeneous functions on the surface. The increase of oxygeneous functions on the surface could improve the hydrophilicity of CCDC, adsorption capacity of solute ion and the capability to form electric double-layer, resulting that the specific capacitance increases from 154.7 F·g-1 to 191.5 F·g-1 and the capacitance retention is above 97%.In order to introduce the high pseudocapacitance of polymer, we prepared CCDC/PANI composite materials by in situ chemical oxidation polymerization. Studed by structural characterization and electrochemical measurements, it conclude that a flake of flocculent PANI was uniformly deposited on the surface and the inner pores of CCDC and the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than PANI. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F·g-1 measured by cyclic voltammery at 1 mV·s-1, and the capacitance retention of coin supercapacitor remained 81.3% after 1000 cycles. Besides, the specicfic power and specicfic energy CCDC/PANI composite are 2.5 kW·kg-1 and 67.5 Wh·kg-1 respectively, which indicated CCDC/PANI composite are a high power density electrode material for supercapacitors.In order to introduce the nitrogen or oxygen functional groups, we prepared functional CCDC with urea and melamine followed by carbonization at 950℃, named U-CCDC and M-CCDC. The samples were characterized by FTIR, elemental analysis. Tests indicated that both surface chemistry and texture of CCDC are improved by the containing nitrogen or oxygen functional groups preexisting on the surface. Electrochemical measurement showed that the U-CCDC and M-CCDCrevealed enhanced capacitances of 210.8 F·g-1 and 225.4 F·g-1 in 1M H2SO4, which increase to 36.3% and 45.7% compared with the initial carbon, respectively. Furthermore, the capacitances of two supercapacitors have nearly no decrease after 5,000 cycles, which exhibited excellent cycle performance.
Keywords/Search Tags:supercapacitor, calcium carbide-derived-carbon, activation, composite, surface functional groups
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