LiNi0.8Co0.2O2 and Sn-doped LiNi0.8Co0.2O2 cathode materials are synthesized via a rheological phase reaction method. They are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), particle size analysis and electrochemical tests. The effects of Sn doping on the structural and electrochemical properties are investigated. The Sn4+ ion occupies the Ni3+ (or CO3+) ion site to form Sn-Ni(or Sn-Co) defects, at the same time, part of the Ni ions are reduced to form Ni-Ni defects to make electric charge compensation in the crystal lattice, which is beneficial for stabilizing the structure, reducing the resistance and increasing conductivity of LiNi0.8Co0.2O2. (c) 2006 Elsevier B.V All rights reserved.