In this study, a series of nanocomposite polymer electrolytes (NCPEs) with high conductivity and lithium ion transference number, PEO/LiClO4/SAP, were prepared from high molecular weight polyethylene oxide (PEO), LiClO4 and low content of homemade silica aerogel powder (SAP), which had higher surface area and pore volume than the conventional silica particle. From the SEM images it was found that the SAP nanoparticles were well dispersed in the PEO polymer electrolyte matrix. The characterization and interactions in the CPEs were studied by DSC, XRD, Fr-IR and Li-7 NMR analysis. The ac impedance results showed that the ionic conductivity of the CPE was significantly improved by the addition of the as-prepared SAP. The maximum ambient ionic conductivity obtained from the CPE with EO/Li = 6 and 2 wt.% of SAP (O6A2) was about threefold higher than that of the corresponding polymer electrolyte without SAP (O6). In addition, the lithium ion transference number (t(+)) of O6A2 at 70 degrees C was as high as 0.67, which was also three times higher than that of O6 and has not been previously reported for the PEO-LiX-based polymer electrolytes. (C) 2008 Elsevier B.V. All rights reserved.