Layered Li[Ni0.8Co0.1Mn0.1]O2-zFz (z = 0, 0.02, 0.04, and 0.06) materials having spherical morphology have been synthesized by a hydroxide coprecipitation method. The effect of fluorine content on the structure, morphology, electrochemical properties, and thermal stability of the Li[Ni0.8Co0.1Mn0.1]O2-zFz has been extensively studied. Electrochemical impedance spectroscopy and electron microscopy showed that fluorine substitution played the important role of reducing the interfacial resistance between cathode and electrolyte, resulting from stabilization of the host structure. The fluorine substitution for oxygen substantially improved the overall electrochemical properties of Li[Ni0.8Co0.1Mn0.1]O-2, such as the capacity retention, rate capability, and thermal stability. (C) 2007 The Electrochemical Society.