Dielectric Relaxation Spectroscopy for Evaluation of the Influence of Solvent Dynamics on Ion Transport in Succinonitrile−Salt Plastic Crystalline Electrolytes

Abstract

Influence of succinonitrile (SN) dynamics on ion transport in SN-lithium perchlorate (LiClO(4)) electrolytes is discussed here via dielectric relaxation spectroscopy. Dielectric relaxation spectroscopy (∼2×10(-3) Hz to 3 MHz) of SN and SN-LiClO(4) was studied as a function of salt content (up to 7 mol % or 1 M) and temperature (-20 to +60 °C). Analyses of real and imaginary parts of permittivity convincingly reveal the influence of trans-gauche isomerism and solvent-salt association (solvation) effects on ion transport. The relaxation processes are highly dependent on the salt concentration and temperature. While pristine SN display only intrinsic dynamics (i.e., trans-gauche isomerism) which enhances with an increase in temperature, SN-LiClO(4) electrolytes especially at high salt concentrations (∼0.04-1 M) show salt-induced relaxation processes. In the concentrated electrolytes, the intrinsic dynamics was observed to be a function of salt content, becoming faster with an increase in salt concentration. Deconvolution of the imaginary part of the permittivity spectra using Havriliak-Negami (HN) function show a relaxation process corresponding to the above phenomena. The permittivity data analyzed using HN and Kohlrausch-Williams-Watta (KWW) functions show non-Debye relaxation processes and enhancement in the trans phase (enhanced solvent dynamics) as a function of salt concentration and temperature.