An analysis of ionic conductivity in polymer electrolytes

Conductivities for a wide variety of ionically conducting polymer electrolytes with a range of salt compositions have been investigated over the temperature region T_g to 370 K. When the conductivity data are analyzed as a function of temperature using the empirical Vogel-Tammann-Fulcher (VTF) equation a common trend is observed in that deviations in the fits to the data invariably occur in the temperature range 1.2 T_g to 1.4 T_g for all of the samples investigated. This deviation is interpreted as a decoupling of the ions from polymer segmental motion. Recent ²³Na NMR and ²²Na positron annihilation studies of sodium salt-based polymer electrolytes support this interpretation with evidence of a change in dynamics at about 1.2T_g. © 1994 John Wiley & Sons, Inc.