A study of the Li/Li+ couple in DMC and PC solvents - Part 1: Characterization of LiAsF6/DMC and LiAsF6/PC solutions

The structures of LiAsF6/DMC and LiAsF6/PC solutions have been investigated at 300 K by infrared and Raman spectroscopies in the 4000-200 cm(-1) waven umber range using various salt concentrations. A dissociation of the lithiu m salt into its ionic species, Li+ and AsF6-, occurs in PC solutions. In DM C solutions, analysis of the v(3) AsF6- mode reveals the presence of contac t ion-pairs Li+...AsF6-, free AsF6- ions, solvated ion-pairs [Li(DMC)(4)]() AsF6-, and polymeric ion-pairs (Li+...AsF6-)(x) when the salt concentrati on changes from 0.1 to 4.5 mol dm(-3). Moreover, we have shown that the con formational equilibrium of DMC was modified by the solvation of lithium ion s strongly increasing the amount of the minor conformer. (C) 1999 Elsevier Science Ltd. All rights reserved.