FT-Raman spectroscopic and density functional theory studies on ion preferential solvation and ion association of lithium tetrafluoroborate in 4-methoxymethyl ethylene carbonate-based mixed solvents

Ion preferential solvation and association interactions of lithium tetrafluoroborate (LiBF4) in binary solvents MEC/DMC (MEC for 4-methoxymethyl ethylene carbonate and DMC for dimethyl carbonate) and MEC/AN (AN for acetonitrile), respectively, have been studied by FT-Raman spectroscopy for different solvent compositions. Intermolecular interactions are present between MEC and DMC or AN. The individual solvation numbers of lithium cation in different environment were deduced. It is found that the lithium ion was preferentially solvated by MEC in all the binary solvents. The ion pairing process is greatly promoted by the increasing molar fractions of DMC and AN in the ternary electrolytes. Some of these findings are supported by quantum chemistry calculation.