Composite electrode materials for lithium-ion batteries obtained by metal oxide addition to petroleum vacuum residua

New composites of carbon with different metal compounds (tin, iron, nickel and vanadium oxides and sulfides) have been obtained at low temperature from petroleum residua, and their electrochemical behaviour has been evaluated in lithium test cells. X-ray diffraction evidenced a partial metal reduction and, in the case of tin, nickel and iron composites, their conversion to sulfides. Optical and SEM microscopy observations confirmed the presence of the metal compounds embedded in the carbonaceous matrix. Electrochemical techniques including impedance spectroscopy were used to evaluate the electrode performance, which was correlated to the microstructural and morphological properties. We have demonstrated the beneficial contribution of the metal sulfides formed in-situ to the electrochemical performance of the electrode material as compared to the carbon material without metal addition. V2O5 was not converted to a sulfide. Instead the reduction to V2O3 was observed, and the resulting composite material exhibited a good capacity retention, ascribable to a modification of the carbon surface properties. (c) 2004 Elsevier Ltd. All rights reserved.