280733 Electrochemical Characterization of LiCoO2 and LiMn2O4 Rechargeable Cathode Materials Produced by Ccso

Monday, October 29, 2012
Hall B (Convention Center )
M. A. Hobosyan and Karen S. Martirosyan, Physics and Astronomy, University of Texas at Brownsville, Brownsville, TX

Rechargeable batteries have found their important role in modern renewable energy industry from laptop batteries to space engineering. Continually growing attention is focused on Li-ion batteries as exceptional high energy density devices. However, cost, safety, stored energy density, charge/discharge rates, and service life are issues that continue to plague the development of the Li battery for the potential mass market of electric vehicles to alleviate distributed CO2 emissions and noise pollution. Automation of manufacturing, material selection, and service life are the keys to lower costs. Lithium Cobaltate LiCoO2 and Lithium Manganese LiMn2O4 are widely used in Li-ion rechargeable batteries as a cathode. Due to the high voltage and the low density of lithium, the amount of energy incorporated in this cell, scaled to its mass or volume, exceeds all other rechargeable battery types.

There are many producing methods for these materials. However, the greater importance in recent years is focused on environmental impact of hazardous lithium oxides that can evaporate at higher temperatures. In this work the thermodynamic calculations for Li-Co-O and Li-Mn-O systems is provided. The new producing method in safe temperature range is presented. Having thermodynamic calculations as a guide, a new fabrication method for LiCoO2 and LiMn2O4 is investigated, using Carbon Combustion Synthesis of Oxides (CCSO). Thermodynamic calculations showed that in system Li-Mn-O during increasing of temperature several oxides of manganese are present, however all they are in solid form. Lithium oxides decomposition and sublimation starts after 2500 K, while synthesis temperature was about 1600 K which avoids undesired sublimation of Lithium oxide. The XRD shows pure crystalline LiMn2O4 with submicron grain size. For the Li-Co-O system 2 oxides are present for Co and Lithium oxide sublimation starts again after 2500 K which allows safe fabrication of LiCoO2 at reaction temperature of 1300 K. The product microstructure by SEM shows 5-25 µm grain size. Electrochemical characterization was made using 8-channel battery analyzer with multiple charge-discharge cycles under constant voltage-constant current modes. The results are well comparable to best commercial cathode powders available, showing capacity range over 200 mAh/g.

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