▎ 摘　　要

A new facile approach is proposed to synthesize nitrogen-doped graphene sheets with the nitrogen-doping level as high as 7.04 at.% by thermal annealing pristine graphene sheets and low-cost industrial material melamine. The high-level nitrogen-doped graphene sheets exhibit a superhigh initial reversible capacity of 1123 mAh g(-1) at a current density of 50 mA g(-1). More significantly, even at an extremely high current density of 20 A g(-1), highly stable capacity of about 241 mAh g(-1) could still be obtained. Such an electrochemical performance is superior to those previously reported nitrogen-doped graphene sheets. The excellent electrochemical performance can be attributed to the two-dimensional structure, disordered surface morphology, high nitrogen-doping level, and the existence of pyridinic nitrogen atoms. The results indicate that the high-level nitrogen-doped graphene sheets could be a promising anode material for high-performance lithium-ion batteries. (C) 2012 Elsevier Ltd. All rights reserved.