Ionic relaxation in polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide polymer electrolytes

Abstract

Polymer electrolytes containing polyethyleneimine and different concentrations of lithium bis͑trifluoromethylsulfonyl͒ imide were investigated by impedance spectroscopy at different temperatures. Two equivalent circuit models were compared for the bulk impedance response. The first one includes a conductive Havriliak-Negami ͑HN͒ element which represents ionic conductivity and ion pair relaxation in a single process, and the second model includes a dielectric HN element, which represents ion pair relaxation, in parallel with ion conductivity. Comparison of the two circuit models showed that the quality of the fit was similar and in some cases better for the conductive model. The experimental data follow the Barton-Nakajima-Namikawa relation, which relates the ion conductivity and the parameters of the relaxation. This indicates that ion conductivity and ion pair relaxation are two parts of the same process and should be described by the conductive model.

Investigating the Correlation of Segmental Dynamics, Free Volume Characteristics, and Ionic Conductivity in Poly(ethylene oxide)-Based Electrolyte: A Broadband Dielectric and Positron Annihilation Spectroscopy Study

“…It is observed that ε′ of the electrolytes is higher than that of pristine PEO throughout the frequency range; however, the rate of increase at higher loading is diminished. The observed increase in ε′ with the salt loading is consistent with the effective medium theory wherein the enhancement of dielectric constant (ε′) is attributed to the addition of salt having relatively higher dielectric constant 70 compared to polymer matrix. The imaginary part (ε″) of the permittivity is also observed to increase with the salt loading as shown in Figure 3b.…”

Solid Electrolytes for Li–S Batteries: Solid Solutions of Poly(ethylene oxide) with LixPON- and LixSiPON-Based Polymers

“…The single-ion conductor can overcome these challenges faced by salt-doped counterparts. Previous studies indicate that high ionic dissociation and enhancement in the concentration of charge carriers can be achieved by introducing nitrogen atoms into the backbone of the polymer, which is known to decrease the anion–cation binding energies. , The anions of the polymer precursors (Li x PON and Li x SiPON) are proposed to be chemically bound with the PEO polymer backbone, resulting in only cation transport. The anionic units in these polymer precursors/PEO mixtures are predicted to be immobile in regard to conductivity.…”

Comparison of Impedance Spectroscopy Expressions and Responses of Alternate Anomalous Poisson−Nernst−Planck Diffusion Equations for Finite-Length Situations

“…Frequency response data sets for a polymer electrolyte containing polyethylene imine (PEI) and lithium bis(trifluoromethylsulfyl imide (LiTFSI) were kindly supplied by Professor G. A. Niklasson . They have been discussed by him and his group in ref . Here we consider the data set with a [N]:[Li] molar ratio of 400:1 at 20 °C and fit it with different models than those utilized in ref .…”