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Investigation Of Surface Modification Of Activated Carbon And Electrode Performance For Supercapacitor

Posted on:2013-08-18Degree:MasterType:Thesis
Country:ChinaCandidate:W F MuFull Text:PDF
GTID:2232330374955028Subject:Applied Chemistry
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The supercapacitor is a new energy storage device with high charge-discharge rate, longcycle life, good temperature characteristicse and nvironment-friendly. The supercapacitor hasbeen recently studied. The electrode is the key component of the supercapacitor. The activatedcarbon electrode materials with surface oxygen groups and preparation techniques of electrodehave important influence for the specific capacitance, internal resistance and charge-dischargeefficiency of supercapacitor. In this paper, the surface modification method using surfactant andsilane coupling agent was investigated. The surface treatment of activated carbon and collectorcan supply an alternative way to decrease in the conten of the bonderwhile essentially keepingthe performance. We investigated the influence of electrode moulding pressure, temperature,and time on supercapacitor performance. It is realistic and crucial to improve the performanceof supercapacitor when conducting research on manufacturing and moulding techniques. Thesurface modification of the activated carbon material are characterized by Fourier transforminfrared spectroscopy and surface area and pore-size distribution. Mechanical properties such ascrook degree, adhesion strength and scanning electron microscopy (SEM) of formed electrodeswere tested. The electrochemical performance of supercapacitor was examined using an ACimpedance, cyclic voltammetry, and constant current charging/discharging tests.1. To improve specific capacity of carbon materials in organic electrolyte solutions, surfacemodification method using surfactant of sodium oleate, sodium dodecylbenzene sulfonate,tetrabutylammonium bromide and benzyl triethy lammonium bromide were investigated in thisstudy. By attachment of hydrophobic functional groups to carbon surface, an improvement inwettability of the carbon materials to organic electrolyte solution wettability of carbon materialsto organic electrolyte with non-polar organic solvent can be improved by surface modificationwith sodium oleate surfactant. After sodium dodecylbenzenesulfonate surface modification,internal resistance of the capacitors decreases, specific capacitance and energy density increase.Effects from surface modification become more marked at higher discharge rates, suggesting thatthe modified carbon materials are more suitable for high-rate supercapacitor applications. itsspecific capacitance increased from316.6F·g-1to396.8F·g-1, internal resistance decreased from1.74to0.69, and its maximum power density increased2.3time.2. A simple strategy by introducing a silane coupling agent into the electrode to improvethe supercapacitor performance has been developed in this study. The surface modification of the activated carbon material and the Al current collector are conducted under two differentneutral and acidic conditions. The improved electrodes are characterized by Fourier transforminfrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical tests andelectrochemical measurements. The obtained results reveal that the treated activated carbonelectrode retains good mechanical properties with decreased bonder content. The electrodeprepared using activated carbon treated with the silane coupling agent in acetic acid conditions(pH=5.0) and a bonder mass content of7.0%shows the best electrochemical performance.Moreover, its specific capacitance increased from261.6F·g-1to352.5F·g-1,internal resistancedecreased from2.96to0.82, and its charge–discharge efficiency increased from88.7%to98.2%.3. We investigated the influence of electrode moulding pressure, temperature, and time onsupercapacitor performance. Mechanical properties such as crook degree and adhesion strengthof formed electrodes were tested. The electrochemical performance of supercapacitor wasexamined using an AC impedance, cyclic voltammetry, and constant currentcharging/discharging tests. According to the results, at20MPa electrode deposition pressure,80℃, and for60s, the supercapacitor showed the best performances with its electrochemicalwindow reaching4.4V, a charge-discharge efficiency of97.6%, and a specific capacitance of428.6F·g-1.
Keywords/Search Tags:Supercapacitor, Activated carbon electrode, Surfactant, Coupling agent, Preparation Process
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