Studies on ionic liquid incorporated polymer blend electrolytes for energy storage applications

Solid polymer blend electrolytes (SPBEs) were prepared using poly(ethylene oxide) (PEO), poly(vinylidene fluoride-hexafluoro propylene) (P(VdF-HFP)) as polymer hosts, zinc triflate (ZnTr) as an electrolyte, and 1-butyl-3-methylimidazolium hexafluorophosphate (1B3MIHFP) as an ionic liquid (IL) via a conventional solvent casting technique. Various techniques like AC impedance spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA) respectively were carried out for the prepared samples. From AC impedance spectroscopic studies, maximum ionic conductivity of 95.72 × 10−4 S cm−1 was observed for the system with 20 wt% of 1B3MIHFP at room temperature. Further, the temperature-dependent ionic conductivity study seems to obey Arrhenius behavior. Complexation and increase in degree of amorphicity for IL incorporated system was confirmed through XRD analysis. Ionic transference number was calculated by Wagner’s polarization technique, and it was found to be 0.991 for the sample which possessed maximum ionic conductivity. This value suggested that the charge transport in the polymer blend electrolyte matrix is mainly due to the Zn2+ ions. The dielectric properties of the SBPEs were also studied using the complex dielectric permittivity spectra, complex electric modulus spectra, and loss tangent analysis. Significant morphological changes were observed from SEM micrographs. From the TG-DTA analysis, thermal stability of the sample was found to be 245 °C.