Dynamic Properties on NMR Spectroscopy of Non-Aqueous Electrolyte Solution Coexisting with Fumed Silica Dispersion

Abstract

In this study, the non-aqueous LiClO4 solution mixed with fumed silica as model system of LIBs was applied, and the dynamic properties and influences which solvent molecules received from solid phase or Li + ion in using the NMR spectroscopy and the relaxation time (T1, T2) measurements were evaluated. The NMR signal of 1 H in PC molecules is influenced by coexisting solid phase in LiClO4-PC solution /oxide powder. The dynamic property of the PC molecules drastically decreased in comparison with the system of the liquid only system. In IR spectra of PC/Alumina systems, the vibration in higher wavenumber range are predominantly observed due to indirect electron-donation from solid surface. The signal intensity depends on influenced liquid content from solid phase. Especially, the LiClO4-PC solution /alumina systems, the intensity is abruptly decreased due to widely spread influences of solid phases. Moreover, the influence from the solid phase to the PC molecules is much smaller than the water molecules from the 1H spin-spin relaxation time (T2). As for the electrolyte concentration dependence, PC system was more remarkable than the water solution system, namely the network structure of the whole PC solvent is greatly affected by the addition of the Li + ion, and it is thought that relaxation time largely decreased.

Relationship between Ionic Interaction and NMR Relaxation Behavior in LiClO4-PC Solution Coexisting with Fumed Metal Oxide

“…We have measured the relaxation behavior of NMR in a single solvent based nonaqueous electrolyte using fumed silica as a solid phase and found that solvent molecules are very strongly influenced by solids even in liquid phase 90 vol% (11). In addition, in real LIBs, low viscosity solvent such as 1,2-dimethoxyethane is added to a high dielectric constant solvent such as propylene carbonate to promote ionic dissociation to improve ionic conductivity (12).…”