Novel high salt content polymer electrolytes based on high T-g polymers

Conductivities greater than or equal to 10(-8) S cm(-1) at T-g are reported in polymer electrolytes based on lithium triflate salt and a series of pol ymers whose T-g is greater than 90 degrees C. The highest conductivities we re observed for poly(acrylonitrile) based systems with salt concentrations greater than 60 wt.%. The conductivity in all cases investigated increases with increasing salt concentration. H-1-NMR T-2 relaxation measurements sug gest that T-g decreases with increasing salt content and confirms that thes e materials are glassy at room temperature and hence that the conductivity is significantly decoupled from the structural relaxations. It appears that the nature of the polymer is important in determining the level of ionic c onductivity, possibly due to differences in polymer coordinating ability or differences in T-g. Polymer-in-salt mixtures based on a tetra-alkyl ammoni um imide molten salt and several high T-g polymers are also reported. The c onductivities of these mixtures appear to be independent of the polymer typ e. (C) 2000 Elsevier Science Ltd. All rights reserved.