关键词: 离子液体, LiCoO₂, 电解质, 电化学性能

Abstract:

The N-methyl-N-ethyl (propyl, butyl) piperidinium bis (trifluo romethanesulfonyl) imide (PP12(3,4)TFSI) ionic liquids were prepared, and their influences on the performances of Li/LiCoO₂ cells were investigated. The electrochemical performance and thermostability of ionic liquids based mixed electrolytes were characterized by electrochemical methods and thermogravimetric analysis. The results showed that the piperidine ionic liquids could improve the thermostability of organic electrolyte, and the size of their side chain had played an important role on the electrochemical performance of Li/LiCoO₂ cell. The Li/LiCoO₂ cell used the electrolyte mixed with PP13TFSI exhibited the best electrochemical performance among the three ionic liquids. The initial discharge capacity reached 156.9 mAh·g^-1 at the rate of 150 mA·g-1 and 3.0 ~ 4.35 V. The discharge capacity upon 200 cycles was 133.9 mAh·g^-1, and the capacity retention was 85.5%. The cycle performance was much better than that in conventional organic electrolytes.

Key words: ionic liquid, LiCoO₂, electrolyte, electrochemical performance