Lithium solvation in bis(trifluoromethanesulfonyl)imide-based ionic liquids

Abstract
The lithium solvation in (1 − x)(EMI-TFSI), xLiTFSI ionic liquids where EMI+ is the 1-ethyl-3-methylimidazolium cation and TFSI the bis(trifluoromethanesulfonyl)imide anion, is shown by Raman spectroscopy to involve essentially [Li(TFSI)2] anionic clusters for 0 < x < 0.4, but addition of stoichiometric amounts of solvents S such as oligoethers changes the lithium solvation into [Li(S)m]+ cationic clusters; the lithium transference number in TFSI-based ionic liquid electrolytes for lithium batteries should thus be strongly improved.