The effects of physical aging on the conductivity of a PEO:LiClO4 (8:1)-Al2O3 (20 wt.%, 24 nm) composite electrolyte were investigated and analyzed. The rate of physical aging was temperature dependent and peaked at 50 C. Aging causes the structure to density, leading to a reduction in the size of the coordinating sphere around lithium. The conductivity: of the electrolyte also exhibited a memory effect, i.e., at a given temperature the conductivity depended not only upon the temperature but also on prior thermal history. The solvent-less electrolyte displays high conductivity with low temperature coefficient in the 20-100 degreesC range. (C) 2003 Elsevier Science B.V All rights reserved.