Fabrication and characterization of magnesium—ion-conducting flexible polymer electrolyte membranes based on a nanocomposite of poly(ethylene oxide) and potato starch nanocrystals

Abstract

Flexible and free-standing electrolyte membranes of nanocomposite ‘poly(ethylene oxide) (PEO)/starch-nanocrystals (SNCs)’ complexed with magnesium bromide (MgBr2) salt at various concentrations (5, 10, 15, 20, and 25 WT.%) were prepared using conventional solution casting technique. The microstructural and thermal stability properties of the pure and MgBr2 salt complexed PEO/SNC nanocomposite membranes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). Complex electrochemical impedance spectroscopy (EIS) and dielectric studies of the nanocomposite membranes were carried out over the frequency range 0.1–1 MHz and within the temperature range of 30–70 °C. Concerning pure PEO/SNCs (10 WT.%), the electrolyte membrane of the composition ‘PEO/SNCs (10 WT.%)/MgBr2 (25 WT.%)’ demonstrated more than three orders of magnitude in the room temperature ionic conductivity, as measured by EIS. A clear shift in the position of the dielectric relaxation peaks was noticed as a function of salt doping concentration in ∂logε′/∂logωversuslogω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\partial log\\left({\\varepsilon }^{{^{\\prime}}}\\right)/\\partial log\\left(\\omega \\right) versus log\\left(\\omega \\right)$$\\end{document} spectra. It was estimated by dielectric spectroscopy that the values of the diffusion coefficient (D) and the total ion concentration (n) for the studied nanocomposite electrolyte membranes were increased in proportion to the doping salt concentrations.