Cobalt phosphides and lithiated cobalt phosphides are prepared by high-energy ball-milling at room temperature. With increasing the milling time, the phosphide structure is converted from CoP3 to CoP phase. The initial electrochemical lithiation of CoPx (CoP3+CoP) and CoP leads to a reversible capacity of 878 and 533 mAh/g. The faradic yield at the first cycle is about 74% for both the samples. Partial lithiation of the CoPx by ball-milling with Li3N reactant enhances the initial faradic yield to 95%, along with a sacrifice of part of the reversible capacity. The lithiation by thermoreaction, however, results in poor electrochemical performance. (C) 2004 Elsevier B.V. All rights reserved.