Electrochemical properties of passivation film on mesophase pitch-based carbon fiber electrode

We studied the irreversible capacity in negative carbon electrodes for the Li ion battery. In this work, we focused on electrolyte decomposition which is one of the main effects related to film formation. We investigated the properties of the film and the process of Li+ intercalation into the mesophase pitch-based carbon fiber (MPCF) in 1 MLIPF6-EC/DEC (1:1, v/v) electrolyte solution. The charge-discharge profile, cyclic voltammetry and impedance spectroscopy showed the electrochemical properties of the film which is formed on the MPCF at the voltage range of 2.4-0.5 V (vs. Li/Li+) during the first charge. FTIR-ATR spectra confirmed the film composition, which consist of Li2CO3, ROCO2Li, ROLi (R = CH3 or CH2CH3). We discuss a systematic change of the structure of MPCF electrode-electrolyte interface at the first intercalation potentials. (C) 2001 Elsevier Science B.V. All rights reserved.