3-(2,2,2-Trifluoroethoxy)propionitrile-based electrolytes for high energy density lithium metal batteries

Abstract

In this study, 3-(2,2,2-trifluoroethoxy)-propionitrile (FEON), a fluorinated nitrile compound with high oxidative stability, low volatility and non-flammability, is introduced as an electrolyte solvent for high-energy density Li|NCM batteries. After optimization of the electrolyte as (0.8 M LiTFSI + 0.2 M LiODFB)/FEC : FEON (1 : 3, by vol., abbreviated as FF13), the FEON-based electrolyte exhibits better cycling performance for both the lithium metal anode and 4.4 V high-voltage NCM cathode, compared with those of a commercial carbonate electrolyte of 1 M LiPF₆/EC : EMC : DMC (1 : 1 : 1, by vol.). As for the FF13 electrolyte, the maximum coordination number of 3 for FEON molecules in the solvation structure is disclosed through molecular dynamics simulation combined with Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy measurements. Furthermore, the solid electrolyte interphase on the lithium metal anode is enriched with organic components and LiF, which is proposed from FEON decomposition based on density functional theory calculations and X-ray photoelectron spectroscopy analysis. All the above results demonstrate that fluorinated nitrile electrolytes constitute a promising platform for high energy density Li|NCM batteries.