In this work, Co3O4 nanoparticles were loaded on the nitrogen-doped porous carbon spheres (NPCS) by a facile hydrothermal method. The NPCS were derived from carboxymethyl chitosan as the carbon and nitrogen source. The as-prepared Co3O4/NPCS nanocomposites were used as anode materials for lithium-ion batteries. The electrochemical results showed that the materials possessed a high initial discharge capacity of 1245.5 mAh g(-1) and still maintained a high reversible capacity of 983.9 mAh g(-1) after 100 cycles at a current density of 100 mA g(-1). Even at a high current density of 5 A g(-1), it delivered a very stable reversible capacity of 659 mAh g(-1). The high electrochemical performance of the Co3O4/NPCS nanocomposites can be attributed to the synergistic effects of the nanoscale Co3O4 particles, the porous structure of the NPCS and the N functional groups on the NPCS. (C) 2015 Elsevier Ltd. All rights reserved.