Improvement of Structural Stability of LiMn2O4 Cathode Material on 55℃ Cycling by Sol-Gel Coating of LiCoO2

摘要

A significant improvement in high temperatureperformance of LiMn2O4 cathode material has been achieved bysol-gel coating its particles surface with LiCoO2. Although theLiCoO2 coating completely disappeared by reacting withLiMn2O4 at 800℃, a newly formed spinel phase, Li1+xMn2-xCoxO4, having a higher Co concentration at the particle surface,provided excellent structural stability on cycling at 55℃.Although the initial capacity at 55℃ was reduced to 109 from113 mAh/g by the coating, the stability on cycling was noticeablyimproved. The coated LiMn2O4 retains approximately 91% of itsinitial capacity after 100 cycles at 0.2 C rate at 55℃ while theuncoated LiMn2O4 suffered nearly 50% loss of the initialcapacity in the same condition. These results indicate that higherconcentration of Co ions at the surface is effective in protectingthe active material from Mn3+ dissolution into electrolytes,resulting in the performance improvement.