AC conductivity and relaxation in CdO doped poly ethylene oxide-LiI nanocomposite electrolyte

Abstract

We have studied the ac conductivity and relaxation in PEO-LiI electrolytes in which different concentrations of CdO nanoparticles (ranging from 0.05 to 0.2 wt. %) have been introduced. The ac conductivity data have been discussed in the framework of power law and electric modulus formalisms. The hopping frequency obtained from the power law analysis obeys the Vogel-Tamman-Fulcher relation and the sample possessing the highest hopping frequency shows the highest dc conductivity. Furthermore, the frequency exponent decreases with the increase of temperature, suggesting a weaker correlation among the Li+ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. We have observed that the imaginary modulus spectra are much broader than the Debye peak-width, but are asymmetric and skewed toward the high frequency sides of the maxima. The modulus data have been fitted to the non-exponential Kohlrausch-Williams-Watts function and the value of the stretched exponent is fairly low, suggesting a wide distribution of relaxation times and cooperative motion of the ions in the nanocomposites.