High quality graphene sheets were prepared from graphite powder through oxidation followed by rapid thermal expansion in nitrogen atmosphere. The preparation process was systematically investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and Brunauer-Emmett-Teller (BET) measurements. The morphology and structure of graphene sheets were characterized by scanning electron microscope (SEM) and high-resolution transmission electron microscopy (HRTEM). The electrochemical performances were evaluated in coin-type cells versus metallic lithium. It is found that the graphene sheets possess a curled morphology consisting of a thin wrinkled paper-like structure, fewer layers (similar to 4 layers) and large specific surface area (492.5 m(2) g(-1)). The first reversible specific capacity of the prepared graphene sheets was as high as 1264 mA h g(-1) at a current density of 100 mA g(-1). Even at a high current density of 500 mA g(-1), the reversible specific capacity remained at 718 mA h g(-1). After 40 cycles, the reversible capacity was still kept at 848 mA h g(-1) at the current density of 100 mA g(-1). These results indicate that the prepared high quality graphene sheets possess excellent electrochemical performances for lithium storage. (C) 2010 Elsevier Ltd. All rights reserved.