Improvement in the Electrochemical Performances of Spinel LiMn2O4 cathodes By MnO2 coating for Lithium Ion Battery Application

Wednesday, May 14, 2014
Grand Foyer, Lobby Level (Hilton Orlando Bonnet Creek)
W. Choi (Korea Institute of Science and Technology), B. Kang (Korea Institute of Science and Technology, Hong-Ik University), J. Joo (Hong-Ik University), J. Lee (Korea Institute of Science and Technology), and M. Park (Advanced Batteries Research Center, Korea Electronics Technology Institute, Korea.)
Lithium ion batteries (LIBs) are considered as attractive power sources for electric vehicles (EV) and aenergy storage systems (ESS) as well as portable electronic devices due to their high energy density and long cycle life. Importantly, EV and ESS applications require high power density and thermal stability as well as low cost. In this regard, spinel LiMn2O4 is a promising cathode material because of its low cost, good safety, high abundance and environmental harmlessness. However, LiMn2O4 generally exhibits poor capacity retention especially at elevated temperatures mostly owing to the Mn dissolution. Moreover, Jahn Teller effect also causes the structural instability, which can be seen on the surface of LiMn2O4 at high current application. Previous literatures verify that surface-modification by coating plays an important role in electrochemical performances of LiMn2O4. The surface treatment of LiMn2O4 is known to prohibit Mn dissolution from LiMn2O4 electrode. In this study, the MnO2 were prepared on the surface of LiMn2O4 powders. The synthesis procedure includes mixing KMnO4 solution with ethylene glycol through oxidation-reduction reaction under ambient conditions. Electrochemical evaluation as well as storage test at elevated temperatures reveal that the surface-modification with MnO2 enhance the rate capability and improve the storage characteristics at 60oC of spinel LiMn2O4 cathode materials. In-depth analyses such as X-ray Photoelectron Spectroscopy and Electrochemical Impedance Spectroscopy are also performed to elucidate the effect of surface-modification using  MnO2.