Fluorine-doped 5 V cathode materials LiNi(0.5)Mn(1.5)O(4-x)F(x) (0.05 <= x <= 0.2) have been prepared by sol-gel and post-annealing treatment method. The results from X-ray diffraction and scanning electron microscopy (SEM) indicate that the spinel structure changes little after fluorine doping, but the particle size varies with fluorine doping and the preparation conditions. The electrochemical measurements show that stable cycling performance can be obtained when the fluorine amount x is higher than 0.1, but the specific capacity is decreased and 4 V plateau capacity resulting from a conversion of Mn(4+)/Mn(3+) remains. Moreover, influence of the particle size on the reversible capacity of the electrode, especially on the kinetic property. has been examined. (C) 2008 Elsevier Ltd. All rights reserved.