COMPOSITION ANALYSIS OF THE PASSIVE FILM ON THE CARBON ELECTRODE OF ALITHIUM-ION BATTERY WITH AN EC-BASED ELECTROLYTE

This work examines the formation of a passive film on the carbon elect rode of lithium-ion batteries. With a single solvent of EC (ethylene c arbonate), the structure of the passive film is found to be (CH2OCOOLi )(2). In a DEC (diethyl carbonate) or DMC (dimethyl carbonate) system, C2H5OCOOLi and Li2CO3 are formed on the surface of the carbon electro de. According to results from mass spectra, CO2 gas is the main produc t when EC is decomposed. By contrast, DEC is decomposed into CO and C2 H6, and DMC into CO and CH4. These findings suggest that the compositi on of the passive film depends on the chosen solvent. In a binary solv ent system which contains EC, the passive film contains chiefly (CH2OC OOLi)(2), which is identical to a single EC solvent system. (C) 1998 P ublished by Elsevier Science S.A. All rights reserved.