Novel Electrochemical Capacitors Using Coal-Derived Carbons

Project Summary Electrochemical capacitors are charge storage devices that are intermediate systems between dielectric capacitors and batteries. While batteries are able to store higher energy density than electrochemical capacitors, they deliver less power. Compared to dielectric capacitors, electrochemical capacitors can store higher energy density with less delivered power. Asymmetric or "hybrid" power sources are currently under development in an effort to push the energy density "envelope" of electrochemical capacitors towards that of commercial battery systems while maintaining power density. In an asymmetric design, a faradaic or battery-type electrode is coupled to a double-layer carbon electrode. The superior performance of hybrid systems. such as nickel oxyhydroxide/potassium hydroxide/carbon and lead dioxide/sulfuric acid/carbon have already been demonstrated and validates the concept proposed in this research activity, to investigate the performance of a novel LiMn204 - activated carbon capacitor using suitable aqueous electrolyte/salt combinations. A lithium intercalated spinel structure serving as the positive electrode will be coupled to a coal-derived, activated carbon negative electrode using a Li2S04 or LiOH aqueous electrolyte. The proposed electrochemical couple is expected to have cell voltage ca. 1.8 V, excellent cycling performance and power density and a specific energy greater than 30 Wh/kg based on active electrode materials. 3