PEOx : LiN(SO2CF2CF3)(2) polymer electrolytes and PEOx : LiN(SO2CF2CF3)(2)-Al2O3 composite electrolytes were prepared by the energy milling process and characterized by means of AC impedance and differential scanning calorimetry (DSC) techniques. An optimized, free-standing electrolyte composition in the PEOx : LiN(SO2CF2CF3)(2) system yields a conductivity value of 1.5 x 10(-4) S cm(-1) at ambient temperature. The ionic conductivity first increases with salt concentration, reaches a maximum value at x = 8.5, and subsequently decreases. The conductivity of the polymer electrolyte decreased after adding 5 and 10 wt.% Al2O3. DSC results revealed that the energy milling process of specimen preparation leads to the formation of complexes between the polymer and the lithium salt. Annealing of the energy milled specimens in the 100 to 200 degrees C temperature range provided a nearly complete amorphous phase. The high conductivities of the polymer electrolytes are attributed to the existence of the complete amorphous phase. (c) 2005 Elsevier B.V. All rights reserved.