石墨烯用作超级电容器电极材料的电化学性能研究

Research on Electrochemical Performances of Graphene Sheets as Electrode Material for Supercapacitors

用天然鳞片石墨为原料,通过改进的Hummers法氧化、离心分离、热还原和超声剥离处理制备出了高品质的石墨烯片。采用透射电镜、高分辨透射电镜、傅里叶变换红外光谱、拉曼光谱、X-射线衍射等测试方法对石墨烯的结构和形貌进行了研究。通过恒流充放电、循环伏安法和交流阻抗等手段研究了石墨烯用作超级电容器电极材料的电化学性能,在0.02 A/g电流密度下的比容量为244 F/g。在0.1 A/g的电流密度下石墨烯超级电容器经过500个循环后比容量保持在198 F/g,表明石墨烯电极材料具有优异的循环稳定性。

High quality graphene sheets are prepared from natural flake graphite by oxidation, centrifugalization, thermal reduction and ultrasonic exfoliation through improved Hummers method. Structure and morphology of graphene sheets are investigated via transmission electron microscopy（TEM）, high-resolution TEM, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and a variety of electrochemical testing techniques. Through galvanostatic charge-discharge, cyclic voltammetry and AC impedance, etc., electrochemical performances of graphene sheets as electrode material for supercapacitors are studied. The electrochemical performance testing shows that the specific capacity of the graphene sheet is as high as 244 F/g at a current density of 0.02 A/g. After 500 cycles, the specific capacity still maintains at 198 F/g at a current density of 0.1 A/g. These results indicate that the graphene-based electrode material possesses excellent cycling stability.