High Temperature Performance of Surface-Treated Li1.1(Ni0.15Co0.1Mn0.55)O1.95 Layered Oxide

The electrochemical performance of pristine and AlF3-coated Li1.1Ni0.15Co0.1Mn0.55O1.95 cathodes is reported for cells cycled at 25 and 55 degrees C. In a half-cell configuration, a nanolayer coating of AlF3 on the Li1.1Ni0.15Co0.1Mn0.55O1.95 stabilizes the capacity on cycling. However, in cell tests with metallic lithium anodes, the initial coulombic efficiency decreased slightly at both 25 and 55 degrees C for AlF3-coated Li1.1Ni0.15Co0.1Mn0.55O1.95 in comparison to the pristine material. For cells constructed with graphite instead of lithium anodes, the capacity stability improved with cycling for the coated cathode materials. Transition- metal dissolution was more pronounced for the AlF3-coated sample when stored at 55 degrees C in electrolytes. For both the pristine and AlF3-coated samples, there was no extra capacity loss due to the elevated temperature. Around 10% capacity gain of the cathode materials at elevated temperature is assumed to be due to improved thermodynamic activation. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3467855] All rights reserved.