▎ 摘　　要

A simple and cost-effective approach is proposed to synthesize the nitrogen (N) and sulfur (S) co-doped graphene sheets. X-ray photoelectron spectroscopy reveals that the content of N and S atoms is 5.42% and 0.52%, respectively, indicating that N and S have been successfully incorporated into the graphene sheets. The resulting co-doped graphene sheets exhibit excellent electrochemical performance when they are employed as anode materials for lithium-ion batteries. A superhigh initial reversible capacity of 1016 mAh g(-1) at a current density of 100 mA g(-)1 was obtained. More significantly, even at an extremely high current density of 20 A g(-1), the as-prepared co-doped graphene still delivers a high capacity of about 250.1 mAh g(-1). The improved electrochemical performance is due to the two-dimensional structure, the large quantity of edge defects, and the synergistic effect of N and S atoms. The results indicate that the co-doped graphene sheets could be promising candidate for high-performance lithiumion batteries materials. (C) 2017 Published by Elsevier B.V.