A new polymer electrolyte system (PEO)n:NaPO3

A new Na+ ion conducting polymer electrolyte, based on poly(ethylene oxide) (PEO) and sodium meta phosphate (NaPO3) is investigated. (PEO),:NaPO3 polymer metal salt complexes with different [ethylene oxide]/Na ratios (n = 3, 4, 6, 8 and 10) are prepared by the solution casting method. Dissolution of the salt into the polymer host is confirmed by X-ray diffraction, differential scanning calorimetry (DSC) and scanning electron microscopy. Further, interaction of the polymer chains with the metal salt is substantiated by Fourier transform infrared spectroscopy. The electrical conductivity of the samples is measured over the temperature range 322-351 K. The temperature dependent conductivity exhibits two different activation energies, below and above the softening point of the polymer. The composition (PEO)(6):NaPO3 is found to exhibit the least crystallinity but the highest conductivity 2.8 x 10(-8) S cm(-1) at 351 K. The electronic transport number, measured by the dc polarization technique, shows that the conducting species are ionic in nature. The effect of ethylene carbonate on the best conducting composition is investigated by DSC and impedance spectroscopy. The addition of 20 wt.% ethylene carbonate, increases the amorphous phase and enhances the conductivity by two orders of magnitude. (c) 2005 Elsevier B.V. All rights reserved.