Alkali metal ion-poly(ethylene oxide) complexes. II. Effect of cation on conductivity.

Complexes of alkali metal salts with various polymers have for some time recognized as fast ionic conductors. Polymer electrolyte fast ion conductors are currently under consideration for use in high energy density electrochemical cells. In order to aid our understanding of the mechanism of ionic conductivity we have examined systematically complexes of poly(ethylene oxide) (PEO) with the alkali metal salt series of Li(+), Na (+), K(+) Rb(+) and Cs(+) with both tetrafluoborate (BF sub 4 sup - and trifluoromethanesulfonate CF sub 3 SO sub 3 sup - anions. The ratio of monomer to salt was 10:1 in all cases. Complex impedance measurements were made on all samples in the temperature range 40 degrees - 125C. With CF sub 3 SO sub 3 sup - as the anion a definite trend was apparent with the smallest cation Li(+) being the worst conductor and Cs (+), the largest cation, being the best.