Exploring high performance and environment-friendly electrode materials is highly desirable for the sustainable Li-ion batteries (LIBs) system. In this study, a facile approach of the modified Hummers' method combining with special thermal reduction was proposed to synthesize nanostructured reduced graphene oxide (RGO) with abundant oxygen-containing functional groups. The resultant RGO showed high specific capacity and excellent cyclability as cathode materials for LIBs. The specific capacity of about 220 mAh g(-1) at a current density of 50 mA g(-1) was achieved after 100 cycles. More importantly, it was demonstrated that the capacity increased with the increase of the amount of oxygen functional groups, highlighting the significant effects of oxygen-containing functional groups of RGO on high lithium storage performance. (C) 2015 Elsevier Ltd. All rights reserved.