Cathode current collectors made of aluminum are corroded by LiN(SO 2CF3)2/ethylene carbonate + dimethyl carbonate (1:1 in volume ratio) electrolyte above 3.7 V. Therefore, the electrolyte cannot be used for 4 V lithium rechargeable batteries. By contrast, LiN(SO 2CF3)2/methyl difluoroacetate (CHF 2COOCH3, MFA) electrolyte showed good inhibition of aluminum corrosion, and a Li/LiCoO2 cell with an aluminum cathode current collector exhibited good cycle performance when the LiN(SO 2CF3)2/MFA electrolyte was used. X-ray photoelectron spectroscopy of the aluminum surface treated by LiN(SO 2CF3)2MFA electrolyte showed that the inhibition of corrosion derives from a passivation film made of an organic compound on the aluminum surface.
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