Effect of Salt Concentration on the Conductivity of PEO-Based Composite Polymeric Electrolytes

The effect of salt concentration on the molal conductivity of various composite electrolytes was studied. Conductivity enhancement is achieved for composite electrolytes over the basic poly(ethylene oxide)−LiClO 4 system in the salt concentration range where the filler concentration corresponds to that of LiClO 4 . On the basis of impedance spectroscopy, DSC, and FT-IR studies, it is concluded that changes in the conductivity result from acid−base type interactions involving polyether oxygens, filler acid or base centers, and alkali metal cations. The effect of a filler is to change the fraction of available oxygen sites which in turn results in changes in the formation of ionic aggregates. The region in which the enhancement of ionic conductivity is observed corresponds to a decrease in the fraction of contact-ion pairs and higher aggregates; this is due to the location of filler molecules in the vicinity of the coordination sphere of Li + cations.