| 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 techniques and other related techniques with the aids of the measure methods such as cyclic voltammetric measurements, constant charge/discharge measurements, X-rays diffraction, transmission electronic microscope measurements and so on. Results came as follows:In this dissertation,we found that it was 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. Activated carbon electrode was proved to have good capacitor performances in neutral electrolyte such as ammonium sulfate solution and ammonium nitrate solution, but a correlated problem is the corrosion of the metal current collector. Nano-MnO2 whiskers were sucessfully synthesized by low heating solid redox reaction using potassium permanganate and manganese chloride, and offered one usful referenced method for synthesize whiskers. For the first time we investigated the electrode characteristics of manganese dioxide as an active material for Supercapacitors in neutral electrolyte, and founded that the manganese dioxide electrode has a good capacitor performance in the 2mol/L ammonium sulfate solution and 0.0~0.90V (vs SEC) potential range, and the electrode can provide a specific capacitance of 304.5F/g, it would be apromising material for the future supercapacitors. Raised the idea of constructing hybrid capacitor with a battery based positive electrode and a capacitor based negative electrode, experiment proved that a hybrid supercapacitor with a manganese dioxide based positive electrode and an activated carbon based negative electrode showed very good performance, double electrode specific capacitance could be enhanced to 95.7F/g, that is 2~3 times that of the carbon based supercapacitors. 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. By using manganese dioxide and activated carbon as actived materials of electrode, we sucessfully assembled an 1.5V 3000F manganese /carbo hybrid supercapacitor, whose performance was closed to that of samilar product made in other country. It will be a promising applied future.In this dissertation, our creative and innovational research in low heating solide-phase synthesis, Nano-MnO2 whiskers, neutral electrolyte, manganese /carbon hybrid supercapacitors and so on gives some significative results, we hope that will give some elicitation for the further investigation of supercapacitors, although there are still something needed given more research.
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