Investigating Intermolecular Interactions in a DME-Based Hybrid Ionic Liquid Electrolyte by HOESY NMR.

The intermolecular interactions in a hybrid electrolyte based on various compositions of the ionic liquid -methyl--propyl pyrrolidinium bis-fluorosulfonylimide (CmpyrFSI), LiFSI salt and an ether-based additive, 1,2-dimethoxy ethane (DME), have been investigated using the HOESY (Heteronuclear Overhauser Effect SpectroscopY) NMR experiment. This NMR technique allows a quantification of the intermolecular interactions in ionic liquids (ILs) by measuring the cross-relaxation rate (σ) between different pairs of nuclei. Thereby, we compare the cross-relaxation rates between the cations, anions and DME in these hybrid electrolyte systems using H-Li and H-F HOESY experiments, and interpret the measured parameters in terms of ionic and molecular associations. The results give insights into the local coordination environment of the Li cations and their solvation by the FSI anions and DME.