Nature and dynamics of lithium ion coordination in oligo(ethylene glycol) dimethacrylate-solvent systems: NMR, Raman, and quantum mechanical study

Systems containing lithium bis(trifluoromethylsulfonyl)imide (TFSI), nona(e thylene glycol) dimetacrylate (EODM), and propylene carbonate (PC), or dime thyl sulfoxide (DMSO) in different concentrations were studied using H-1, L i-6, and Li-7 and C-13 1D and 2D single quantum and double quantum filtered spectra, the corresponding longitudinal, transverse, rotating frame and T- 1(3) or T-2(3) relaxations, Raman spectra, and quantum mechanical (MNDO up to ab initio SCF 6-31G and DFT) calculations. The mean, local, and exchange mobilities of the lithium ion as well as the apparent equilibrium constant s of coordination to EODM (two stages) and the solvent were established. Ac cording to the study, the solvent in a gel electrolyte acts not only as a p lasticizer but also as a competitive ligand loosening the coordination bond of the lithium ion to the poly(ethylene oxide) moiety. DMSO was found to b e substantially more effective in this respect than PC.