Nanosize cobalt sulfides were synthesized through a one step chemical reaction method at room temperature. The cobalt sulfide nanopowders were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy and electrochemical testing. The results revealed that the cobalt sulfide is a semiconductor; the reversible capacity is increased with increasing content of electronic conductors in the active material of electrodes. The as prepared sample with 10 wt.% carbon black and 10 wt.% polypyrrole (PPy) powder as electronic conductors shows the best electrochemical properties, with a reversible capacity of over 300 mAh g(-1) based on the total mass of the electrode. Cobalt sulfide nanopowders show promise as cathode active materials for lithium-rechargeable batteries. (c) 2006 Elsevier B.V. All rights reserved.