DETERMINATION OF POLYMER ELECTROLYTE STRUCTURES BY X-RAY POWDER DIFFRACTION. Philip Lightfoot, Yuri Andreev, Peter G. Bruce, School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK

Polymer electrolytes consist of inorganic salts dissolved in coordinating polymers such as poly(ethylene oxide) [(CH₂CH₂O)_n]. They can exhibit conductivities approaching that of many liquid electrolytes and their materials properties make them very attractive for use in the next generation of solid state devices. Since single crystals cannot be grown we have recently pursued ab initio powder methods to determine some of these structures. Several structures of the form MX:poly(ethylene oxide)_n (M = Li⁺, Na⁺, K⁺, Rb⁺, NH₄⁺; X = C1O₄^-, CF₃SO₃^-, or SCN^-; n = 3 or 4) will be discussed. More recently a new Monte Carlo based method¹ has been developed and applied to the determination of the structure of LiN(CF₃SO₂)₂:PEO₃, a problem which we were unable to solve by "conventional" powder methods. The use of constrained Rietveld refinement will be emphasised in tackling these structures. The effect of cation and anion size in determining the structures adopted will also be discussed.

1. Y. Andreev et al. This meeting.