Role of preparation methods on the structural and dielectric properties of plasticized polymer blend electrolytes: Correlation between ionic conductivity and dielectric parameters

摘要

The polymer blend based electrolyte films consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) with lithium triflate (LiCF_3SO_3) as a dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer have been prepared by solution cast melt-pressed and ultrasonic assisted followed by microwave irradiated solution cast melt-pressed methods. The X-ray diffraction study infers that the amorphous phase of (PEO-PMMA)-LiCF_3SO_3-x wt% PEG electrolytes decreases with the increase of PEG concentration. The complex dielectric function, ac electrical conductivity, electric modulus and the impedance spectra of these electrolytes have been investigated over the frequency range from 20 Hz to 1 MHz. It is found that all the dielectric/electrical functions of these electrolytes vary anomalously with the increase of PEG concentration, and also with the change of samples preparation methods. The activation energies have been determined from the temperature dependent values of dc ionic conductivity, polymer segmental relaxation time and dielectric strength. Results reveal that besides the amorphicity, the ionic conductivity of these electrolytes is also governed by the relaxation time and the dielectric strength, and the transport of ions is due to hopping mechanism which is coupled with segmental motion of polymers chain. Room temperature ionic conductivity values of the PEO-PMMA blend based electrolytes are found about one to two orders of magnitude higher than that of the PEO and PMMA based electrolytes.