Nanofiller-Induced Ionic Conductivity Enhancement and Relaxation Property Analysis of the Blend Polymer Electrolyte Using Non-Debye Electric Field Relaxation Function

Abstract

The enhancement of conductivity of a composite polymer as a dielectric material is an essential requirement for electrostatic storage devices. We have modified the microstructure of the polymer matrix by introducing an insulating nanofiller SiO2. The effect of such a filler on the ionic conductivity of the composite polymer electrolyte has been investigated using a variety of experimental techniques along with the non-Debye type of relaxation functions. We have achieved optimum conductivity enhancement at a threshold filler concentration of 0.7 wt % in the blend polymer matrix composed of poly(ethylene oxide), poly(vinylidene fluoride) (80:20), and salt NH4 I (35 wt %). Such an enhancement of conductivity is a result of formation of a highly conducting interphase region around the nanofiller surface. The mobility of the conducting species is found to increase enormously in the presence of a filler. As a consequence, the ionic conductivity of the filler-induced blend polymer electrolyte increases 3 times of its magnitude (3.02 × 10–3 S/cm) compared to that without a filler. The occurrence of two different activation energies which decrease with increasing filler concentrations, as determined from temperature-dependent conductivity, has been well explained from the dynamics of free and contact ions. A non-Debye behavior of relaxation properties has been analyzed using a newly approached one-parameter Mittag-Leffler function. The experimental decay function fits very well using the Mittag-Leffler function as compared to the conventional non-Debye Kohlrausch–Williams–Watts function used in the literature.