Preparation And Electrochemical Characteristic Of PbO₂/AC Super-battery

In January,2007, supercapacitors were listed as one of the seven discoveries of the world technology by "Discover", a world famous periodical on science and technology of American. Having interesting many scientific workers in recent years, supercapacitors are intermediate energy storage systems between conventional capacitors and batteries. Compared to the conventional battery, supercapacitors have such merits as high power density, long cycle life, wide working temperature, strong anti-seismic capability, low maintenance cost, and no pollution. With the world’s increasing attention to the environment, the demand for new energy resources becomes more intense, which gives rise to the pure electric vehicle and hybrid cars. As one member of the new energy resources, supercapacitors are attracting more attention from people, which, in return, ascends the development of supercapacitors to unprecedented levels. Due to the advantages of supercapacitors, they have displayed great prospects. How to improve the specific energy of supercapacitors has become a major issue all over the world.This dissertation is carried out following the international foreland research, according to many references and books. Supercapacitors were assembled with activated carbon materials as negative electrode and lead dioxide as positive electrode, by optimizing preparation methods of the materials and selecting the optimal preparation conditions, activated carbon and dioxide lead film electrode are synthetized, which are required by the supercapacitors and then assembled into the hybrid supercapacitors. Some electrochemical properties of electrode materials and supercapacitors are tested by using the advanced experimental equipment. These databases provide experimental materials and facts for the study of the performance of hybrid supercapacitors. The chief research contents are given as follows.1. Dispersed polyaniline has been used as the protecting liquid of current collectors, is plastered on copper foil to form a protection layer, and is applied to supercapacitors. Preservative effect of the protection layer in H2SO4solution is examined by applying the prepared current collectors in the supercapacitors and, according to the product of the experiment, the optimal thickness of the protection layer is chosen. These supercapacitors take activated carbon as negative electrode materials and graphite plate electroplated with dioxide lead film electrode as positive electrode materials, and5.3mol L-1H2SO4electrolyte as plating solution, which are assembled into the hybrid supercapacitors. The capacitance characteristics of the double layer supercapacitors are tested by using constant current charge-discharge methods and electrochemical impedance spectrum measurement. The results show that the specific capacitance remained70%after500cycles at current dencity of400mA g-1when current collector copper foil is plastered five times with dispersed polyaniline to form a protection layer, used for the hybrid supercapacitor.2. The multi-walled carbon nanotubes are acidized by the nitric acid, oscillated by supersonic wave for two hours, then filtered, washed and dried, by which single-walled carbon nanotubes are finally obtained. Single-walled carbon nanotubes obtained is mixed in a certain proportion with activated carbon materials and binder. The mixture is then used for making electrodes which are then assembled into supercapacitors. Afterwards, the electrochemical properties of the supercapacitors are examined in the aqueous electrolyte and the organic system respectively. The results show that when single-walled carbon nanotube occupies a proportion of20%-25%, the specific capacitance of supercapacitor doesn’t decrease after2760cycles in aqueous and slowly increases in organic based electrolytes at current dencity of100mAg-1.3. Carbon foams are used as the positive current collectors. Lead oxide is deposited on them by adopting the cyclic voltammetric deposition method, and the morphology and structure features of the PbO2electrode materials are examined by scanning electron microscope (SEM), which are electrodeposited at different current densities. The super-battery is prepared by using the lead dioxide electrode as positive electrode, AC electrode as negative electrode and5.3mol L"1H2SO4as electrolyte. Electrochemical performance of super-battery is examined by using constant current charge-discharge test, cyclic voltammetry and EIS measurements. The results show that the carbon foams are suitable for the current collectors of the super-battery, because it can resist the corrosion of the H2SO4solution, and effectively improve the specific capacity.