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Research On The Related Techniques Of Supercapacitors

Posted on:2003-01-10Degree:MasterType:Thesis
Country:ChinaCandidate:Z X LiuFull Text:PDF
GTID:2132360092466455Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
Because envinment protection is more and more concerned by the society, electric vehicles are becoming ideal new generation tranportion tools, and that give a chance for the development of supercapacitors. Supercapacitors, new energy storage components between batteries and electrostatic capacitors, could meet the high power need of electric vehicles when starting-up or accelerating for their power density could be tens of times higher than batteries. They could also be used as electric components and power sources for small apparatus or direct current switches. Supercapacitors have become a hotspot in research because of their wide application foreground. In many countries, supercapacitors have been researched thoroughly and been sucessfully used in electric vehicles, while reaesrch tide has just came to China in recent years, till now there isn't any report on applicable supercapaictor techniques or products. So it's of great importance to research on supercapacitors for the promotion of electric vehicles in our nation. In this desseration we conducted a series of experiments researching in electrode materials, electrolytes, preparation and assemble techmiques and other related techniques with the aids of the measure methods such as cyclic voltammetric measurements, electrochemical impedance measurements, constant charge/discharge measurements, X rays diffraction, electronic microscope measurements and so on. Results came as follows:1. Proposed a new measurement method ?Double Working Electrode Measurement, by which we can get the information about the potential contribution of positive electrode and negative electrode to the overall voltage of a capacitor cell. The information is very useful in performance optimization of a supercapacitor.2. We found that it is the smallness of the positive electrode capacitance that limits the performance of carbon based supercapacitors in alkaline electrolytes, and the performance could be meliorated if the active material loaded on positive electrode increased.3. Activated carbon electrode was proved to have good capacitor performance in neutral electrolyte such as ammonium nitrate solution, but a correlated problem is the corrosion of the metal current collector.4. Sucessfully assembled 6V300F and 3V1000F activated carbon based supercapacitors, whose performance are closed to that of samilar product made in Japan.5. Synthesized compound electrode material with Faraday electron tronsferation process as well as non-Faraday double layer charge/dishcarge process. Although this material is not successfully used in supercapacitors, this idea may be very useful is other respects.6. Raised the idea of constructing hybrid capacitor with a battery based positive electrode and a capacitor based negative electrode, experiment proved that a hybrid capacitor with a nickel hydroxide based positive electrode and an activated carbon based negative electrode showed very good performance, double electrode specific capacitance could be enhanced to 90.7F/g, that is 2-3 times that of the carbon based capacitors. Furthermore, the maximal voltage of a single cell could be expanded to 1.5V, as a result, the energy density could be ten times higher than that of a carbon based supercapacitors.7. For the first time we investigated the electrode characteristics of cobalt dihydroxide as an active material for supercapacitors, although the single electrode specific capacitance is only 71F/g, much smaller than that of activated carbon, somthing of significance is the very low impedance of the colbat electrode. The equvalent facial resistance is only 200mQ'cm2, which is much less than 1.6?'cm2 of the carbon electrode. This property is very suitable for supercapacitor use.8. We found that cobalt dihydroxide synthesized by deposition transformation shows higher capacitance, 92F/g, while after ten thousand cycles, most of the Co(OH)2 on the electrode changes to Co3O4, and the capacitance increases to 133F/g. We concluded that if the capacit...
Keywords/Search Tags:Supercapacitor, Ultracapacitor, Double-Layer Capacitor, Hybrid Capacitor
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