Abstract: Coal-tar pitch based mesocarbon microbeads, graphitized at the maximum heat treatment temperature of 2 800 ℃, were employed as the negative electrode materials in lithium ion batteries. Electrochemical performances of the graphitized mesocarbon microbeads(MCMBs) in different electrolyte systems were examined. Chemical composition and relative content of surface electrode inhibition(SEI) film formed on the carbon electrode was determined. The influences of co-solvents on the SEI formation, composition and the film texture were discussed. The results show that, the SEI film consists mainly of the reduction products of EC molecules in EC-based electrolytes despite a certain difference exists in the onset of the SEI formation potential. The texture of SEI film is a deciding factor on the compatibilities of the electrolytes with the carbon electrode in lithium ion batteries.

Key words: Lithium ion batteries, Carbon negative electrode, Graphitized MCMB, Electrochemical lithiation