Molecular dynamics (MD) simulations, density functional
theory
(DFT) calculations, and 1H NMR spectroscopy were performed
to gain a complementary understanding of the concentrated Li-ion electrolyte
system, lithium bis(trifluoromethanesulfonyl)imide (Li[TFSI])
dissolved in tetraglyme. The computational methods provided the concentration
dependence of differing solvation structure motifs by reference to
changes in the corresponding NMR spectra. By combining both the computational
and experimental methodologies, we show that the various solvation
structures, dominated by the coordination between the tetraglyme (G4)
solvent and lithium cation, directly influence the chemical shift
separation of resonances in the 1H NMR spectra of the solvent.
Thus, the 1H NMR spectra can be used to predict the fraction
of tetraglyme involved in the solvation process, with quantitative
agreement with solvation fraction predictions from MD simulation snapshots.
Overall, our results demonstrate the reliability of a hybrid computational
and experimental methodology to understand the solvation structure
and hence transport mechanism of LiTFSI-G4 electrolytes in the low
concentration region.