Effects of inhomogeneity on ionic conductivity and relaxations in PEO and PEO–salt complexes

Electrical properties of purified poly(ethylene oxide)-PEO and PEO with dissolved lithium salts, PEO10:LiCF3SO3 and PEO10:LiN(CF3SO2)2, were investigated by impedance spectroscopy. Changes of the impedance spectra during crystallization and melting were recorded. Semicrystalline polymer films exhibited frequency dependence of conductivity with two limiting values of conductivity at low and at high frequency. It was concomitant with dispersion of the electric permittivity exhibiting the low-frequency values of the order of 200. In the case of PEO with dissolved salt, when the film was quasi-amorphous, the electric permittivity also exhibited pronounced dispersion, which was probably due to the presence of crystalline PEO–salt complexes. The dielectric relaxation caused by rearrangement of dipoles in PEO chain was observed at low temperatures and high frequencies.