A comparison of ion transport in different polyethylene oxide-lithium salt composite electrolytes

Abstract

Polyethylene oxide (PEO) and lithium salts (LiI, LiClO₄, and LiCF₃SO₃) based composite polymer electrolytes have been prepared for different [EO]/[Li] ratio using solution casting method and characterized by X-ray diffraction (XRD), scanning electron microscope, and differential scanning calorimetry (DSC). The electrical measurements have been carried out at different temperatures. XRD patterns, field emission scanning electron micrographs, and DSC clearly depict that amorphous region in the PEO-LiClO₄ composite electrolyte with [EO]/[Li]=9 is dominant over the other electrolytes. It has been observed that the electrical conductivity of the PEO-LiClO₄ electrolyte is higher than that of the PEO-LiI and PEO-LiCF₃SO₃ composite electrolytes. It has been also observed that the hoping rate of charge carriers for the PEO-LiClO₄ electrolyte is higher than that of the other two electrolytes. The concentration of charge carriers is not thermally activated and the mobility controls the temperature dependence of electrical properties. Scaling of the conductivity spectra has been performed in order to get insight into the relaxation mechanisms.