INTRODUCTION:  PEO(polyethylene oxide) has been studied for a long time as an electrolyte since introduced by Wright and Armand et al in 1979 at first. However, PEO-LiX polymer electrolytes are affected by some problems, namely i) a reactivity towards the lithium metal electrode, ii) a low conductivity at ambient temperature(<10-8S/cm) iii) poor mechanical properties Composite electrolytes are among the most promising candidates for use in rechargeable lithium batteries.[1,2] These are obtained by dispersing inorganic particles (eg,TiO2,Al2O3,MgO) in a polymer matrix.[3] In this study, we fabricated nanocomposite electrolytes with fumed silica(~11nm) and focusing their surface groups which may provide secondary pathway for Li cation migration.