Dielectric relaxation and lithium ion transport study of ultrasonic and microwave irradiated polymer nanocomposite electrolytes

Abstract

The polymer nanocomposite electrolytes (PNCEs) consisted of poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO₄) (stoichiometric ratio EO:Li⁺ = 8:1) with montmorillonite (MMT) clay as inorganic nanofiller are prepared through ultrasonicated and microwave irradiated electrolyte solutions by a solution casting method following the melt-press technique. The electrical characterizations of these PNCE films are carried out using dielectric relaxation spectroscopy in the frequency range from 20 Hz - 1 MHz at ambient temperature. The real part of complex permittivity of these electrolytes has dispersion over the frequency range 1-100 kHz where the polymer segmental dynamics relaxation peak is appeared in the dielectric loss spectra. The values of dielectric strength and relaxation times for these electrolytes are determined, and a correlation of these parameters with the dc ionic conductivity is explored. The results reveal that the lithium cations are coordinated with exfoliated MMT nanosheets and functional group of PEO, which make a transient cross-linked structure in these materials. The presence of MMT in the polymer electrolyte matrix offers hindrance to the cations mobility which is reflected from decrease in ionic conductivity of PNCE films. The X-ray diffraction patterns confirm an amorphous nature of the electrolytes with the exfoliated MMT structures.