中文摘要：

用多壁碳纳米管作为起始原料,通过化学氧化、离心分离、高温膨胀和超声剥离等步骤制备了石墨烯片。采用透射电子显微镜（TEM）、X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）对石墨烯片的形貌和结构进行分析。通过恒流充放电和交流阻抗测试研究了石墨烯片作为锂离子电池负极材料的储锂性能。结果表明,石墨烯片在50mA/g的电流密度下,首次可逆比容量为859mAh/g,经过50次循环后比容量仍保持在410mAh/g,远高于碳纳米管（217mAh/g）,表明石墨烯片具有优异的储锂性能。

英文摘要：

Graphene sheets（GSs） were prepared from carbon nanotubes（CNTs） by chemical oxidation, centrifugal separation, high thermal expansion and ultrasonic treatment. The morphology and structure of the GSs were systematically investigated by transmission electron microscope（TEM）, X-ray diffraction（XRD） and Fourier transform infrared spectroscopy（FT-IR）. Lithium storage properties of the GSs were investigated by galvanostatie charge- discharge and electrochemical impedance spectroscopy. It was found that the GSs electrode exhibited a relatively high reversible capacity of 859 mAh/g at a current density of 50 mA/g. After 50 cycles, the reversible capacity of the GSs electrode was kept at 410 mAh/g, which was much higher than carbon nanotubes electrode. These results indicate that the graphene sheets possess excellent electrochemical performances for lithium storage.