A solid polymer electrolyte (SPE) is synthesized by solution casting technique. The SPE uses poly(ethylene oxide) PEO as a host matrix doped with lithium triflate (LiCF3SO3), ethylene carbonate (EC) as plasticizer and nano alumina (Al2O3) as filler. The polymer electrolytes are characterized by Impedance Spectroscopy (IS) to determine the composition of the additive which gives the highest conductivity for each system. At room temperature, the highest conductivity is obtained for the composition PEO-LiCF3SO3-EC-15%Al2O3 with a value of 5.0710(-4) S/cm. The ionic conductivity of the polymer electrolytes increases with temperature and obeys the Arrhenius law. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) studies indicate that the conductivity increase is due to an increase in amorphous content which enhances the segmental flexibility of polymeric chains and the disordered structure of the electrolyte. Fourier transform infrared spectroscopy (FTIR) spectra show the occurrence of complexation and interaction among the components. Scanning electron microscopy (SEM) images show the changes morphology of solid polymer electrolyte. (C) 2011 Elsevier B.V. All rights reserved.