Solid polymer electrolyte (SPE) composites, which are composed of poly(ethylene oxide) (PEO), mesoporous silica (SBA-15), and lithium salt were prepared in order to investigate the influence of SBA-15 content oil the ionic conductivity of the composites. The ionic conductivity of the SPE composites was monitored by frequency response analyzer (FRA), and the crystallinity of the SPE composites was evaluated by using XRD. As a result, the addition of SBA-15 to the polymer mixture inhibited the growth of PEO crystalline domain, due to the mesoporous structure of the SBA-15. Also, the PEO16LiClO4/SBA-15 composite electrolytes show an increased ion conductivity as a function of SBA-15 Content LIP to 15 wt.%. These ion conductivity characteristics are dependent oil crystallinity with SBA-15 content. (C) 2007 Elsevier B.V. All rights reserved.