A series of cathode materials for lithium-ion batteries with the formula LiV3-2xNixMnxO8 (0 <= x <= 0.100) were synthesized by a sol-gel method. The effects of Ni and Mn substitution on the structural, morphology and electrochemical properties of the cathode materials were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), charge-discharge test, cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS) experiments. Results show that an effective improved cycling performance is observed for Ni and Mn co-doped cathode materials, which is interpreted to be due to a greater reversibility during cycling and decrease of charge-transfer impedance. (C) 2007 Elsevier B.V. All rights reserved.