Novel amide-based deep eutectic solvent electrolytes for high-performance lithium-ion batteries

Abstract

The electrolytes of lithium-ion batteries (LIBs) directly affect their performance, safety, and reliability. However, existing electrolytes are still limited in terms of safety, performance, and environmental friendliness, constraining further development and application of LIBs. Herein, novel electrolytes based on a deep eutectic solvent consisting of LiTFSI [lithium bis(trifluoromethane)sulfonylimide] and DMA(N,N'-dimethylacetamide) were developed for LIBs. The results from thermogravimetry analysis, infrared spectroscopy, Raman scattering, UV-visible NIR diffuse reflectance, optical and scanning electron microscopy, and electrochemistry all showed safe, nonflammable, nontoxic, and environmentally friendly electrolytes with good thermal stability, enhanced electrochemical stability, and excellent lithium-ion conductivity. Cyclic voltammetry and electrochemical impedance spectroscopy confirmed electrolytes with rapid transport of lithium ions and stable electrochemical interface formation. The electrolytes showed good compatibility with the LiFePO4 cathode, effectively protecting the structure of the LiFePO4 electrode. The first discharge capacity of LiTFSI-DMA deep eutectic electrolyte reached as high as 156.6 mAh g−1, with a discharge capacity after 365 cycles at 1C current density reaching 142.6 mAh g−1 and a capacity retention rate of more than 91%. Overall, LiTFSI-DMA deep eutectic electrolytes with superior performance and compatibility have the potential as high-performance nonflammable electrolytes for improved LIBs.