Fundamental Studies on Novel Double Layer Capacitors

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Electrochemical capacitor (EC) energy technologies, including double layer capacitor (DLC) and electrochemical double layer capacitor (EDLC) have promising potential in electric vehicles (EV) or hybrid vehicles. The most important advantages of EC are their high power and energy densities. Other EC advantages include long cycle life (100,000 - 1,000,000 cycles) and maintenance-free property.The energy density of EC mainly depends on specific capacitance and applied voltage. The maximum capacitance of EC is limited by the concentration of ions in the electrolyte. The key to increase the energy density of the electrochemical capacitors seems to rest in the increases in the electrochemical windows and ionic concentrations of the electrolytes, and improvement of mass transfer in metal oxide film. The project objectives include: Development of novel electrodes: Composite electrodes composed of carbon and nano-film of metal oxide will be investigated. Development of novel electrolytes: Organic liquids as electrolytes will be investigated. Modeling and investigation of charge-discharge mechanisms. Current metal oxide film used in EC has micrometer thickness and the fabrication is complicated. In this research, a novel oxide film processing method is proposed. By adsorbing metal to activated carbon and then modifying it to metal oxide, the new method will produce nano-meter-thick metal oxide film, having high energy density and low internal resistance.The theoretical analysis and preliminary experiments were conducted and specific energy was calculated. Theoretical energy density of 1600-2000 Wh/kg was obtained for electrochemical capacitor unit using ionic liquids.It is anticipated that the goals outlined in this proposal will lead to the development of a new capacitor with high power and energy densities.