Research On The Materials For Electrochemical Supercapacitors

Electrochemical supercapacitor is a new energy storage component between batteries and electrostatic capacitors, which has higher power density than that of batteries and higher energy density than that of electrostatic capacitor. When working with batteries, they can meet the high power out-put need of electric vehicles when starting-up or accelerating. They can also be used as electric components and power sources for small electrical equipment and direct current switches. Now supercapacitors have become a hotspot in research. There isn't any report on applicable supercapacitors techniques or products in our country. For all purposes, it's very important to have study on supercapacitors for the promotion of electric vehicles in our nation. According to the principle of energy-storage there are two types of capacitors: electric double-layer capacitor and faradaic pseudocapacitor. A series of experiments were conducted to research on electrode according to the principle of energy-storage materials, electrolytes, preparation techniques with the aids of the measure methods such as cyclic voltammetric measurements(CV), constant charge/discharge measurements, impedance spectrum, X-rays diffraction(XRD), transmission electronic microscope measurements(TEM), and so on. By experiments the conclusions were got that the actived carbon electrode could provide better capacitive character in 7mol/L potassium hydroxide solution after activation in ammonia. In additon this paper studied the preparation techniques and obtained small capacitor with the specific capacitance of 54 F/g when the charge-discharge current was 2.5mA/cm2, whose cyclic life was over 1000 cycles. Successfully we made kilofarads capacitor. The paper also found that the capacitance of the positive electrode was much smaller than that of negative one, and then it urged to develop new positive materials to make up hybrid capacitor. As for materials for faradaic pseudocapacitor, we mainly studied metal oxide. The paper prepared ferric oxide by sol-gel method, decomposition product of potassium permanganate and cobalt oxide by pyrogenation way, nano-nickel oxide by sol-gel and pyrogenation method and manganese oxide by different ways. Finally the conclusion was that the best material was nanophase manganese oxide synthesized with solid-phase reaction. The best electrolyte was potassium hydroxide with the concentration of 1mol/L.The specific capacitance of singal electrode could reach 325F/g when the charge-discharge current was 2mA/cm2, and cycled over 5000 times. This kind of electrode would run well to assemble hybrid capacitor together with active carbon electrode. It could be the base of forward research.