Effects of Salts in Methyl Difluoroacetate-based Electrolytes on their Thermal Stability in Lithium-ion Batteries

摘要

The effects of salts in methyl difluoroacetate (MFA)-based electrolytes on their ionic conductivity and their thermal stability were investigated. When LiPF{sub}6 was used as a salt, an MFA-based electrolyte showed a higher ionic conductivity than an ethylene carbonate (EC) and dimethyl carbonate (DMC)-based electrolyte from -30 to 25 ℃. In DSC curves, while an MFA-based electrolyte containing LiPF6 gave only negligible exothermic heat up to 400 ℃, a large exothermic peak due to the electrolyte decomposition was observed at about 270 ℃ for an EC + DMC-based electrolyte. The thermal stability of lithium metal and de-lithiated LiCoO{sub}2 coexisting with an electrolyte of 1 mol dm{sup}(-3) LiPF{sub}6/MFA is also reported.