Oxidation of propylene carbonate containing LiBF4 or LiPF6 on LiCoO2 thin film electrode for lithium batteries

An oxidation behavior of propylene carbonate with 1.0 mol dm(-3) LiBF4 or L iPF6 was investigated using in situ Fourier Transform Infrared (FTIR) spect roscopy with p- or s-polarized infrared beams to observe surface phenomena occurring on a LiCoO2 thin film electrode during anodic polarization beyond 4.0 V versus Li/Li+. The obtained FTIR spectra exhibited the formation of the same reaction products in two electrolytes during anodic polarization o f the LiCoO2 thin film electrode. This result shows that the oxidation prod uct of propylene carbonate is independent of the kind of electrolyte salt. On the other hand, the peak intensity in the FTIR spectra depended on the k ind of electrolyte salt. This means that the decomposition rate of propylen e carbonate is influenced by the kind of electrolyte salt. The oxidation of propylene carbonate with LiPF6 was more severe than that in propylene carb onate with LiBF4. (C) 2001 Elsevier Science Ltd. All rights reserved.