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

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 montmorillonite clay as filler. Structural studies confirm the intercalation 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 dependence of the conductivity was studied using broadband dielectric spectroscopy, it followed Vogel-Tamman-Fulcher trend, which suggests strong coupling between ionic conductivity and segmental relaxation in polymer electrolytes. This phenomenon is correlated with coupling index. Relaxation processes are studied using both dielectric and modulus formalisms. Additionally, conductivity spectra showed nearly constant loss and universal Jonscher's power law at low and high temperatures, respectively. Crossover from nearly constant loss to ion hopping conductivity region is also observed.