Sustainable Energy Technologies Department
"Title: Synthesis, Characterization and Application of High Power and High Capacity Cathode Materials of Lithium Ion Batteries"
Presented by Yujie Zhu, University of Maryland
Wednesday, January 8, 2014, 11 am
Bldg. 815 1st Floor Conference Room
Hosted by: Feng Wang
Lithium ion batteries have become the exclusive power source of choice that drives our digital and mobile daily life, while higher stakes are being offered by markets of higher strategically importance, such as vehicle electrification and grid stabilizations. However, the power and energy density provided by traditional lithium ion batteries fails to support these large-scale applications, mainly due to the limits imposed by the cathode chemistries. In this talk, we will focus on the synthesis, characterization and application of high power and high capacity cathode materials of lithium ion batteries, namely LiFePO4 and LiF+Co/Fe, respectively. First, LiFePO4 with different structures was synthesized by hydro-/solvo-thermal method. The microsized LiFePO4 was applied to study the fundamental phase transition mechanism of this material by using in situ transmission electron microscopy. For the first time, the anisotropic lithiation mechanism was directly observed and a sharp (010) phase boundary between LiFePO4 and FePO4 was observed, which migrated along the  direction during lithiation. The nanosized LiFePO4 was used as a starting material to generate the high capacity cathode electrode for sodium ion batteries. Electrochemical tests showed that NaFePO4 can maintain high capacity retention after hundreds of charge-discharge cycles in sodium-ion batteries. Also, both thermodynamics and reaction kinetics for sodium ion insertion/extraction in carbon-coated olivine NaFePO4 were systematically investigated and compared to lithiation and delithiation in olivine LiFePO4. Second, motivated by the fact that conversion-reaction type cathode materials have much higher theoretical capacities than the state-of-the-art intercalation-type cathodes due to their ability of accommodating more than one Li per transition metal core, we applied a simple and scalable process based on aerosol-spray pyrolysis to synthesize conversion-reaction type cathode materials