Preparation and microstructural and electrochemical characterization of (PEO)(n)LiAl(SO3Cl)(4) (n = 2-12) polymer electrolytes containing a mixture of plasticisers, i.e. propylene carbonate (PC) and 1,2-dimethoxyethane (DME), is presented. The effect of plasticizer mixture on polymer crystallinity and its electrical conductivity at various temperatures is studied using X-ray powder diffractometer analysis, differential scanning calorimetry, size exclusion chromatography, and Raman and FTIR spectroscopy in combination with impedance spectroscopy. The dependence of the glass transition temperature, crystallinity and conductivity of the (PEO/PC/DME)(n)LiAl(SO3Cl)(4) polymer electrolytes on salt concentration is measured and discussed with reference to the literature on similar systems. Finally, a quantitative analysis using the Vogel-Tamman-Fulcher equation of a typical conductivity/temperature curve for the amorphous polymer electrolytes under consideration is presented.