Energy Sciences & Technology Dept. Seminar

Lithium ion batteries have the highest performance in secondary battery chemistry. However, in order to use their advantages for aerospace, military, and automobile applications, their energy density (mass (Wh_kg-1) and volume (Wh_l-1)) need to be increased further. This can be accomplished by replacing the widely used LiCoO2 cathodes and carbonaceous anodes with high performance electrode materials. Compared to LiCoO2 cathode, LiFePO4 has a much higher performance and ideal working potential. In my presentation, I will talk of my work on LiFePO4 cathode materials. It will include electrical conductivity (ionic & electronic conductivity) toward the high performance electrode material, the crystal structure and improved performance of vanadium doped LiFePO4, and phase transformation phenomenon during lithium ions intercalation/extraction. For a more fundamental study, LiFePO4 thin films were deposited on an alumina substrate with an RF sputtering system at Oak Ridge National Lab. Its electrochemical performance was examined to reveal the fundamentals.
To achieve excellent cyclability, rate capability and safety, the electrochemistry and crystal structure of Li4Ti5O12 has been studied. Lithium titanate has low volume expansion during cycling, fast electrochemical kinetics, and is non-reactive with electrolytes. Our goal was to study the crystal evolution and relationship between electrochemistry and crystal structure. Our study facilitated in making super-high powered batteries without the lifespan limitations generally associated with batteries.