Effect of plasticizers on ionic conductivity and dielectric relaxation of PEO-LiClO4 polymer electrolyte

In this paper, we report the effect of different plasticizers, such as poly ethylene glycol, propylene carbonate, ethylene carbonate and dimethyl carbonate on the ionic conductivity and dielectric relaxation of PEO-LiClO4 solid polymer electrolytes. The highest ionic conductivity is obtained for polymer electrolyte plasticized with poly ethylene glycol. The temperature dependence of ionic conductivity follows the well known Vogel–Tamman–Fulcher relation which indicates a strong coupling of ionic and segmental motions for all compositions. The experimental data for the complex dielectric permittivity and electric modulus have been studied using Havriliak–Negami function for the understanding of ion dynamics. Maximum dielectric strength is obtained for polymer electrolyte plasticized with poly ethylene glycol. The modulus data have been analyzed using non-exponential Kohlrausch–Williams–Watts (KWW) function. It is observed that the non-exponential parameter β is quite lower than unity, suggesting highly a non-exponential relaxation exists in these materials. The temperature dependence of relaxation times obtained from dielectric and modulus formalisms also follow Vogel–Tamman–Fulcher relation for all plasticizers in the compositions.