Experimental and Theoretical Investigations of Dimethylacetamide (DMAc) as Electrolyte Stabilizing Additive for Lithium Ion Batteries

Dimethylacetamide (DMAc) is used as an electrolyte stabilizing additive for lithium ion battery. The effects of DMAc on the enhancements of electrolyte thermal stability and the solid electrolyte interphases (SEIs) on graphite anode and LiFePO4 cathode were investigated via a combination of electrochemical methods, nuclear magnetic resonance (NMR), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), as well as X-ray photoelectron spectroscopy (XPS). It was found that 1.0 M LiPF6 EC/DMC/DEC (1/1/1,weight ratio) electrolyte with 1% DMAc incorporation can be stable at 85 degrees C for over 6 months without precipitation and color change. In addition, the addition of 1% dimethylacetamide (DMAc) can significantly improve the cyclic performance of a LiFePO4/graphite cell at elevated temperature. These improved performances are ascribed to the enhancement of the thermal stability of the electrolyte and the modification of SEI components on graphite anode and LiFePO4 cathode. The explicit working mechanism of DMAc stabilizing LiPF6-based electrolyte is also discussed by the density functional theory (DFT) calculations.