表面改性对膨胀石墨电容性能的影响

Research on capacitance property of surface-modified expanded graphite

以膨胀石墨作为电容材料,研究了表面修饰和蚀刻对其电容行为的影响。采用恒流充放电、循环伏安等手段对其电性能进行了测试,采用红外光谱对其表面化学基团进行了表征。结果表明:膨胀石墨经H_2O_2表面修饰后,比电容由1.94 F/g提高至5.05 F/g,红外光谱分析表明处理后膨胀石墨表面产生了大量的羰基和羟基等含氧基团;经KOH蚀刻后,表面没有出现新的化学基团,但其表面被活化,更容易与H_2O_2发生化学反应,使得表面含氧官能团密度增大,故蚀刻后的膨胀石墨再经H_2O_2处理,其比电容由4.54 F/g提高至15.90 F/g,但电位窗口阈值由1.0 V下降至0.4 V。

The expanded graphite (EG) was investigated to find the influence of surface modifying and etching on its energy-storage behaviors. The electrical performance was characterized by galvanostatic charge-discharge and cyclic voltammetry measurement. The surface chemical groups were detected by IR scanning. The results show that the specific capacitance is enhanced from 1.94 F/g to 5.05 F/g after modified by 30% H2O2 for 24 h. The IR spectrum shows a large number of oxygen-containing functional groups emerge on the surface of EG. After etched by KOH, there is no appearance of new chemical groups on the surface, but the surface of EG is activated, therefore, more easily react with H2O2. As a result, the specific capacitance is greatly improved from 4.54 F/g to 15.90 F/g after the etched EG is modified by H2O2, but the maximum value of potential window is reduced from 1.0 V to 0.4 V.