Abstract
Currently adding a suitable additive in the electrolyte is one of the most effective strategies to improve the electrochemical performance for a lithium-ion battery, especially under high temperature. In this work, N,N-dimethylformamide (DMF) as an electrolyte additive was introduced to improve the battery performance of LiFePO4 at 60 °C. The addition of DMF can effectively increase the specific capacity, cycling performance, and rate performance of batteries using LiFePO4 as cathode material. X-ray diffraction results reveal that for the electrode cycled in the electrolyte without additive, Fe2O3, FePO4, and other impurity peaks appear under high temperature. scanning electron microscopy/transmission electron microscopy results indicate that some deposits are generated on the electrode surface without additive under high temperature due to the decomposition of electrolyte in the reaction between electrolyte and electrode materials. The Fourier transform infrared spectroscopy/NMR/X-ray photoelectron spectroscopy results demonstrate that DMF as a lewis base can capture lewis acidic PF5 from the decomposition of LiPF6 as well as block the chain reaction of LiFePO4 with hydrogen fluoride, which alleviates the electrolyte decomposition and electrode dissolution at high temperature.