A mixed-salt polyether electrolyte: PEOLiCF3SO3Nal

Conductivity and n.m.r. measurements are reported for three poly(ethylene oxide)-inorganic salt complexes: PEO-LiCF3SO3-NaI ([EO]/[Li]/[Na] = 8/1/1), PEO-LiCF3SO3 ([EO]/[Li] = 4), and PEO-NaI ([EO]/[Na] = 4). The mixed-salt system was shown to have a larger amorphous phase content than either of the single-salt systems and more potential charge carriers. A dramatic effect upon the lithium motion and the microviscosity of the amorphous phase was noted upon the mixing of salts. It is proposed that some lithium ions are in environments of low symmetry, possibly of the ion-pair type, and do not contribute to the n.m.r. signal. The recrystallisation behaviour of the mixed-salt material was studied by the n.m.r. technique and an initial fast recrystallisation appears to be due to the formation of the high-melting temperature phase.