Studies on Electrochemical Oxidation of Propylene Carbonate Electrolyte on LiMn₂O₄ Thin Film Electrode

Abstract

In situ FTIR measurements were performed to analyze the electrochemical oxidation of propylene carbonate with 1.0 mol dm-3 LiClO4 on LiMn2O4 cathode used in rechargeable lithium batteries. A thin film electrode of LiMn2O4 was prepared by rf-sputtering method. The prepared LiMn2O4 film had a high quality as an electrode for the in situ FTIR measurement. The subtractively normalized interfacial FTIR (SNIFTIR) spectra were obtained at various electrode potentials from 3.8 V to 4.8 V vs. Li/Li+. The peaks in the SNIFTIR spectra corresponding to decomposition products of propylene carbonate showed that the electrochemical oxidation of propylene carbonate started at 4.4 V. The oxidation products of propylene carbonate were assigned to compounds having carboxylic groups. Furthermore, from the comparison of in situ FTIR spectra for LiCoO2 and LiMn2O4 cathodes, it was shown that final products depend on the kind of transition metal oxides.