A poly(ethylene oxide) (PEO)-based nanocomposite polymer electrolyte (NCPE) doped with nanosized Li0.1Ca0.9TiO3, a lithium fast ionic conductor, has been developed. The ionic conductivity and lithium ion transference number of PEO12-LiClO4-Li0.1Ca0.9TiO3 NCPE are both enhanced by the addition of nanosized Li0.1Ca0.9TiO3, with a maximum ionic conductivity of 1.02 X 10(-5) S cm(-1) at room temperature and a maximum lithium ion transference number of 0.533 at 70 degrees C when the Li0.1Ca0.9TiO3 content is 15 wt %. A broad electrochemical stability window suggests that the NCPE is a viable candidate for the electrolyte material in lithium polymer batteries. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3257593] All rights reserved.