Abstract

In this work, solid polymer electrolytes based on poly(ɛ-caprolactone) (PCL) with lithium bis(oxalato)borate as a doping salt were prepared by solution cast technique using DMF as a solvent. The electrical DC conductivity and dielectric constant of the solid polymer electrolyte samples were investigated by electrochemical impedance spectroscopy over a frequency range from 50 Hz to 1 MHz. It was found that the DC conductivity increased with increase in the salt concentration to up to 4 wt% and thereafter decreased. Dielectric constant versus salt concentration was used to interpret the decrease in DC conductivity with increase in salt concentration. The DC conductivity as a function of temperature follows Arrhenius behavior in low temperature region, which reveals that ion conduction occurs through successful hopping. The curvature of DC conductivity at high temperatures indicates the contribution of segmental motion to ion conduction. High values for dielectric constant and dielectric loss were observed at low frequencies. The plateau of dielectric constant and dielectric loss at high frequencies can be observed as a result of rapid oscillation of the AC electric field. The HN dielectric function was utilized to study the dielectric relaxation. The experimental and theoretical data of dielectric constant are very close to each other at low temperatures. At high temperatures, the simulated data are more deviated from the experimental curve of dielectric constant due to the dominance of electrode polarization. The non-unity of relaxation parameters (α and β) reveals that the relaxation processes in PCL-based solid electrolyte is a non-Debye type of relaxation.

Highlights

  • The knowledge of polymer electrolytes is a highly specialized interdisciplinary field which encompasses the disciplines of electrochemistry, polymer science, organic chemistry, and inorganic chemistry

  • It was observed that conductivity values increased by more than five orders of magnitude from 1.79 9 10-11 S cm-1 for pure PCL film to 6.50 9 10-6 S cm-1 for PCL film containing 4 wt% of lithium bis(oxalato)borate (LiBOB) salt

  • LiClO4 at room temperature, which is comparable to that obtained in this work

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Summary

Introduction

The knowledge of polymer electrolytes is a highly specialized interdisciplinary field which encompasses the disciplines of electrochemistry, polymer science, organic chemistry, and inorganic chemistry. This field has attracted the attention of many researchers in both academia and industry, due to its potentially promising applications [1]. Polymer electrolytes which are complexes of solvent-free polar polymers and inorganic metal salts are prepared by dissolving salts in high-molecular-weight polymer hosts. Polymer electrolytes have been studied extensively by researchers because of their potential applications, namely, in high-energy density batteries and fuel cells [2]. Some polymers are successfully used as a host material to prepare polymer electrolytes for specific applications; among these

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