Translational Diffusion of Components in Concentrated LiTFSI Solutions in Acetonitrile According to Multinuclear Pulse NMR Data

Abstract

The diffusion coefficients of solvent molecules, cations and anions in concentrated “LiTFSI–acetonitrile” solutions were measured in the temperature range from  – 15 to + 75°C. The activation energies (E_a) for diffusion motion of each species were calculated. The features of translational motion in this system are discussed. The data indicate the existence of some predominant structural composition with the molar ratio “salt/ACN”≈1/4.5. The acetonitrile molecules move more freely in the structural “mosaic” than solvated ions. A new approach to describing the concentration dependencies of diffusion coefficients in the case of fast both translational motion and exchange between substructures is suggested.