The influence of synthesized nano-sized TiO2 Particles on the ionic transport properties of PEO (polyethylene oxide)-based composite polymer electrolytes (CPEs) was investigated in this study. The nano-sized TiO2 particles with pure anatase phase can be synthesized by a developed process. lt was found that the ionic conductivity of the TiO2 modified CPE increases with a decrease in the grain size of TiO2. The conductivity (sigma = 1.40 x 10(-4) S cm(-1)) for the PEO-10% LiCIO4-5% TiO2 (3.7 nm) electrolyte is an order of magnitude higher than that the pure PEO-10% LiCIO4 (sigma = 1.03 x 10(-5) S cm(-1)) at 30 degrees C. Meanwhile, the transference numbers of 0.51 and 0.21 were obtained for the TiO2 modified CPE and pure PEO-LiCIO4, respectively. Both results imply that the nano-sized TiO2 particles in the PEO-LiCIO4 matrix provide a new pathway for the transport of lithium ions. (c) 2005 Elsevier B.V. All rights reserved.