Investigation of Li+ Cation Coordination and Transportation, by Molecular Modeling and NMR Studies, in a LiNTf2-Doped Ionic Liquid- Vinylene Carbonate Mixture
E Bolimowska and F Castiglione and J Devemy and H Rouault and A Mele and AAH Padua and CC Santini, JOURNAL OF PHYSICAL CHEMISTRY B, 122, 8560-8569 (2018).
To increase the safety and stability of lithium-ion batteries, the development of electrolytes based on ionic liquids (ILs) has gained a lot of attention in recent years. However, with graphite electrodes, neat ILs afford weak cycling performance in the absence of organic additives (e.g., vinylene carbonate, VC). The potential formation of a Li+-O-VC interaction/coordination could have a major influence on the observed electrochemical behavior of Li-ion batteries. On a specific electrolyte, 1-hexyl-3-methylimidazolium bis-(trifluoromethanesulfonyl)imide C(1)C(6)ImNTf2 in association with LiNTf2 (1 mol L-1) and VC, we performed NOESY, H-1-Li-7 HOESY correlations, and pulsed field gradient spin-echo NMR measurements, combined with molecular dynamics simulations to determine whether such an interaction/coordination between VC and Li+ ions is noticeable. Li-7-H-1 HOESY experiment shows the vicinity of VC with Li+ cation, and strong correlations and association between Li+ and VC are observed in intense first peaks in radial distribution functions and quantified by the coordination numbers in the first solvation shell between Li+ and the carbonyl oxygen atom of VC.
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