Engineering of electrode structure for enhanced rate behavior

Two primary concerns for electrochemical energy storage and conversion applications are the obtainable power and energy of the system. The advanced batteries currently being investigated for electric automobiles and consumer electronics have very good energy density but do not perform well under high power demands. The purpose of my work has been to engineer electrode structures such that high reaction rates, and therefore high powers, are possible without sacrificing the already high energy densities of the system.;Amorphous vanadium pentoxide (V2O5) shows a high specific energy and a high capacity for Li intercalation. However, the rate of insertion is typically limited by lithium diffusion in the host and by its modest conductivity. This thesis demonstrates that high intercalation rates are possible if the host microstructure is modified to decrease the characteristic lithium diffusion distance and the characteristic conduction distance. Thin films of V2O5 aerogel were grown by preferential gelation on sintered nickel fibers via a sol-gel route. Electrochemical impedance measurements of the composite electrodes indicated that diffusion limitations in the host were successfully avoided. Impedance analysis in the redox capacity region revealed that the majority of the V2O5 aerogel was electrochemically accessible. Constant current cycling and cyclic voltammetry were also used to characterize the composites. Specific powers, based on mass of active material, of almost 6 MW/kg were observed.