In this article, a modified tape casting method is employed by dispersing and ball milling of Al2O3 powders in the poly (vinylidene fluoride) polymer, with the aim of developing uniform nanocomposite separators in the lithium-ion cell system. The surface morphology, pore structure, heat-resisting property, infrared property, and cell performance of the nanocomposite separators are investigated. The experimental results indicate that ball milling plays an important role in yielding homogeneous, porous nanocomposite separator membranes. The developed separator membranes exhibit high thermal stability and excellent electrochemical performance, therefore, are promising for use in the lithium-ion cell systems. (c) 2013 Wiley Periodicals, Inc.