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

The electrochemical performance of pristine and AlF{sub 3}-coated Li{sub 1.1}Ni{sub 0.15}Co{sub 0.1}Mn{sub 0.55}O{sub 1.95} cathodes is reported for cells cycled at 25 and 55 C. In a half-cell configuration, a nanolayer coating of AlF{sub 3} on the Li{sub 1.1}Ni{sub 0.15}Co{sub 0.1}Mn{sub 0.55}O{sub 1.95} stabilizes the capacity on cycling. However, in cell tests with metallic lithium anodes, the initial coulombic efficiency decreased slightly at both 25 and 55 C for AlF{sub 3}-coated Li{sub 1.1}Ni{sub 0.15}Co{sub 0.1}Mn{sub 0.55}O{sub 1.95} 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 AlF{sub 3}-coated sample when stored at 55 C in electrolytes. For both the pristine and AlF{sub 3}-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.