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 achiev ed for composite electrolytes over the basic poly(ethylene oxide)-LiCl O4 system in the salt concentration range where the filler concentrati on corresponds to that of LiClO4. On the basis of impedance spectrosco py, DSC, and FT-IR studies, it is concluded that changes in the conduc tivity result from acid-base type interactions involving polyether oxy gens, filler acid or base centers, and alkali metal cations. The effec t of a filler is to change the fraction of available oxygen sites whic h in turn results in changes in the formation of ionic aggregates. The region in which the enhancement of ionic conductivity is observed cor responds to a decrease in the fraction of contact-ion pairs and higher aggregates; this is due to the location of filler molecules in the vi cinity of the coordination sphere of Li+ cations.