Ni-substituted Co3O4/graphite composites were synthesized by precipitation of cobalt oxalate and nickel oxalate on the surface of graphite and pyrolysis of the precipitate. The effects of nickel content and calcination temperature on the properties of the composites were investigated. The samples were characterized by thermogravimetry and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV) and charge/discharge measurements. The composites consist of graphite and a face-centered cubic (fcc) Co3O4 phase of fd3m space group, and there is no diffraction peaks associated with nickel compounds. Mild nickel substitution can improve the reversble capacity of the Co3O4/graphite composite. With increasing the calcination temperature from 300 to 500 degrees C, the reversible capacity of the composites with 10% Ni substitution increases from 641 to 874 mA h g(-1). The composite synthesized at 400 degrees C shows an initial reversible capacity of 690 mA h g(-1) and excellent cycling stability. (C) 2009 Elsevier Ltd. All rights reserved.