Silane-functionalized mesoporous silica SBA-15 particles with ultra-high specific surface area and large pore size were used as fillers in PEO-based solid electrolytes. FT-IR results confirmed the silane finictionalization of SBA-15. Ionic conductivity and lithium ion transference number of the composite polymer electrolytes were found to simultaneously reach a high value of 5 wt.% silane-ftinctionalized SBA-15 introduced in the matrix. It may be due to the combination effects of the unique structure of SBA-15 (i.e., ultra-high specific surface area and large pore size), the particularly functionalized surface of SBA-15 to promote fast ion transfer, and the good dispersion and compatibility of silane-functionalized SBA-15 in the composite polymer electrolytes. The results suggest an alternative way to improve the performance of solid polymer electrolytes. (c) 2006 Elsevier B.V. All rights reserved.