Anodic oxidation of nonaqueous electrolytes on cathode materials and current collectors for rechargeable lithium batteries

Oxidation of propylene carbonate on Al and LiCoO2 electrodes was observed by using cyclic voltammetry and in situ FTIR spectroscopy combined with potential step experiment. From these measurements, two points were discussed in this study. The oxidation of solvents on LiCoO2 occurred at 4.2 V vs. Li/Li+ that corresponds to the cut-off potential of rechargeable lithium ion batteries, because of high catalytic activity of transition metal oxide materials. On the other hand, the oxidation on Al as a current collector was strongly influenced by passivation phenomena in nonaqueous electrolyte. The passivation phenomena depend on a kind of electrolyte salt. Among four electrolyte salts used in this study [LiClO4, LiPF6, Li(CF3SO2)(2)N, and Li(CF3SO2)(C4F9SO2)N], Li(CF3SO2)(C4F9SO2)N exhibited several interesting features which were useful to suppress the anodic oxidation of nonaqueous electrolytes and dissolution of Al. Furthermore, a mixed solvent of ethylene carbonate and dimethoxyethane with Li(CF3SO2)(C4F9SO2)N was not oxidized at 4.8 V vs. Li/Li+ on both LiCoO2 and Al electrodes. In addition, the anodic corrosion of Al in this electrolyte was suppressed. (C) 1999 Elsevier Science S.A. All rights reserved.