Structural dynamics and ionic conductivity of amorphous type plasticized solid polymer electrolytes

Abstract

Poly(ethylene oxide) and poly(methyl methacrylate) blend based solid polymer electrolytes consisting of lithium triflate as a dopant ionic salt with varying concentration of propylene carbonate as plasticizer have been prepared by classical solution cast and ultrasonic-microwave irradiated solution cast methods. The X–ray diffraction study confirms that these electrolyte films have predominantly amorphous morphology. Dielectric relaxation spectroscopy in the frequency range 20 Hz - 1 MHz reveals that the complex dielectric spectra of the electrolytes have dispersion at high frequencies corresponding to polymer chain segmental relaxation process in the solid ion-dipolar complexes, whereas the electrode polarization relaxation process dominates at low frequencies. Significant changes in the polymer chain dynamics and dielectric parameters of the electrolytes are observed with change of plasticizer concentration and the sample preparation methods. Relatively enhanced polymer chain segmental dynamics, ordered ion-dipolar cooperativity and favourable ion conductive paths increase three times the ionic conductivity of 15 wt% PC polymeric electrolyte film prepared by ultrasonic-microwave irradiated method as compared to that of the classical solution cast method. The ionic conductivity and dielectric relaxation time have the Arrhenius temperature dependence characteristics of their same values of activation energies. Results infer that the ions transportation in the solid complexes of these electrolytes is predominantly governed by polymer segmental dynamics.