Structure and phase transitions in PEO(poly(ethylene oxide))-KI complexes. [Poly(ethylene oxide)]

It is generally accepted that PEO (poly(ethylene oxide)) electrolytes are not single-phase, homogeneous materials in the ranges of composition and temperature of interest for batteries and other low temperature electrochemical devices. The polymer-salt mixtures often contain multiple phases, which makes detailed analysis of structure and transport properties difficult. This paper shows that x-ray absorption experiments can be used to study the microscopic structural parameters of these materials, and that microstructural information thus obtained can be correlated with macroscopic thermodynamic and transport data. The conclusion drawn from the the studies of PEO-KI complexes is that the transition to a higher conductivity phase at elevated temperatures is associated with a decreasing oxygen coordination number of the K/sup +/ ion.