Characterization of lithium-based poly (ethylene oxide)/poly (vinylidene fluoride-co-hexafluoropropylene) solid blend polymer electrolytes for energy storage applications

In this present study, poly(ethylene oxide) (PEO):poly(vinylidene fluoride-co-hexafluoropropylene)P(VdF-HFP):lithium bromide (LiBr)-based solid blend polymer electrolytes (SPEs) are prepared by using solution casting technique with dimethyl formamide (DMF) as solvent. According to XRD analysis, the incorporation of LiBr improves the amorphous nature of the prepared electrolytes. FTIR analysis confirms the complexation between polymers and salt. Scanning electron microscopy (SEM) was used to examine the surface morphology and blending of the electrolytes. Impedance spectroscopy studies showed higher ionic conductivity of 3.75 × 10−4 S cm−1 at room temperature for the sample containing 4 wt% LiBr. The electrolytes were observed to follow Arrhenius behavior with R2 ~ 1, in which all samples were thermally activated as the temperature rises. The complex dielectric permittivity (ε∗)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(\varepsilon *)$$\end{document}, loss tangent (tanδ)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(tan \delta )$$\end{document}, conductivity (σ)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(\sigma )$$\end{document}, and also complex electric modulus (M∗)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(M*)$$\end{document} were used to understand the presence of electrode polarization. Wagner’s polarization technique was used to determine the transference number of these polymer electrolytes and it was found that the ionic conductivity was mostly due to ions. Transport characteristics like mobility (μ) and mobile ion diffusion coefficient (D) were also derived. The breakdown voltage of the polymer electrolytes was evaluated using linear sweep voltammetry (LSV). Using cyclic voltammetry (CV) analysis as well as Galvanostatic charge–discharge (GCD) measurement, maximum specific capacitance (Csp)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$({C}_{sp})$$\end{document} of 11.27 F/g was determined for the electrolytes. The energy (E) and power (P) density have been found to be 1.34 Wh/kg and 250 W/kg respectively.