This paper presents a composite technology, which combines doping and modifying to optimize the performance of spinel Li-Mn-O. Co ion-doped Li-Mn-O was synthesized by a wet chemical process. The homogeneously distributed C layer was chemically grown on the surface of LiCo0.1Mn1.9O4 by the hydrothermal method. The products were analyzed and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Their electrochemical performances were tested with the Arbin instruments. The results showed that a different concentration of C influenced both the morphologies and the cycling performances of the cathode materials greatly. (c) 2005 Elsevier Ltd. All rights reserved.