Observation of ionic transport and ion-coordinated segmental motions in composite (polymer-salt-clay) solid polymer electrolyte

Abstract

A solution casting method was successfully used to realize polymer nanocomposite electrolytes consisting of polyethylene oxide as polymer host, lithium hexafluoroarsenate as salt, and dodecylamine modified mont- morillonite clay as filler. Structural studies confirm the inter- calation of polymer-salt complex into the silicate layers of the clay and lithium hexafluoroarsenate salt solvate very well in polyethylene oxide matrix. The electrical conductivity of the polymer-salt-clay composite was higher by more than one order of magnitude than that of the corresponding polymer- salt complex at ambient temperature. Temperature depen- dence of the conductivity was studied using broadband di- electric spectroscopy, it followed Vogel-Tamman-Fulcher trend, which suggests strong coupling between ionic conduc- tivity and segmental relaxation in polymer electrolytes. This phenomenon is correlated with coupling index. Relaxation processes are studied using both dielectric and modulus for- malisms. Additionally, conductivity spectra showed nearly constant loss and universal Jonscher's power law at low and high temperatures, respectively. Crossover from nearly con- stant loss to ion hopping conductivity region is also observed.