A new type of COO nanoparticles encapsulated by graphitable hollow carbon sphere (GHCS) composite material was synthesized. The core-shell structure CoO/GHCS composite shows the improved cyclability as an anodic material in Li-ion battery. The core-shell composite containing 50 wt% CoO exhibits a reversible capacity of 584 mAh g(-1) at a constant current density of 100 mA g(-1) between 0 and 3.0 V (vs. Li+/Li), and remains a capacity retention of 95% after 50th cycle. The improvement could be attributed to that the GHCS with a good electronic conductivity and high surface severs as dispersing medium to prevent COO nanoparticles from aggregating, and provide the enough space to buffer the volume change during the Li-ion insertion and extraction reactions in CoO nanoparticies. (C) 2007 Elsevier B.V. All rights reserved.