The effect of addition of nanoparticle inorganic oxides to poly(ethylene oxide) (PEO) complexed with LiClO4 on cation transport properties has been explored by electrochemical and 7 Li nuclear magnetic resonance (NMR) methods. The presence of the nanoparticles generally increases the ionic conductivity and the cation transference number, the effect being greatest for TiO2. The enhancement in cation transference number is directly correlated with increased Li diffusivity measured by NMR. The NMR results also demonstrate that the increased ionic conductivity is not attributable to a corresponding increase in polymer segmental motion, but more likely a weakening of the polyether-cation association induced by the nanoparticles.