Nanoparticle-dispersed polymer electrolytes have been prepared by stirring or high-energy ball milling of polyethylene oxide (PEO), lithium salt (LiCF 3SO 3, LiClO 4 and LiPF 6), and nanometer-size ceramic powder (TiO 2, SiO 2 and Al 2O 3). The smaller the size of ceramic particles, the better they influence the crystallization kinetics of the PEO polymer chains. High-energy ball milling lowers the glass transition temperature of the composite polymers, and thus increases the ionic conductivity greater than the order of the magnitude compared with the un-milled samples. The highest ionic conductivity was reported when using LiPF 6 as added lithium salt and Al 2O 3 as dispersed particle. Cyclic voltametric measurements showed that the PEO-system is electrochemically stable in the range of 2–5 V.