Translational and reorientational dynamics of ionic liquid-based fluorine-free lithium-ion battery electrolytes

The translational as well as reorientational mobilities of fluorine-free electrolytes prepared by mixing lithium furan-2-carboxylate Li(FuA) salt with tetra(n-butyl)phosphonium furan-2-carboxylate (P-4444) (FuA) ionic liquid are thoroughly investigated. The diffusivity of ions and T-1 relaxation of protons belonging to various chemical groups of (P-4444)(+) and (FuA) ions and the Li+ ion present in these electrolytes are measured as a function of lithium salt concentration and temperature. The temperature dependence of correlation time for reorientational mobility of various chemical groups of (P-4444)(+) and (FuA) ions and the Li+ ion are estimated and used in calculations temperature dependence of the corresponding reorientational rates. It is shown that an increase in the concentration of lithium salt leads to a decrease in both the diffusion coefficients and the reorientation rates for all the chemical groups in concerted way. Activation energy of the reorientational rates for different chemical groups of the organic ions and the Li+ are discussed in details. (C) 2021 The Author(s). Published by Elsevier B.V.