The electrochemical performance of a multi-wall carbon nanotube/activated carbon mixture as the electrode of electric doublelayer capacitors analyzed by electrochemical impedance
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摘要: 以石油焦为原料化学活化制得活性炭（Activated carbon，AC），在此AC中加入不同量的多壁碳纳米管（Multi-walled carbon nanotubes，MWCNTs)作为超级电容器电极材料。依据交流阻抗谱中阻抗与电容关系，区分有效容量和内阻造成的能量损失，评价了超级电容器的性能。结果表明：加入质量分数3%~15%MWCNTs的AC电极，实部电容高于纯AC电极，虚部电容则随着MWCNTs添加量的增加而显著降低。且其实部电容分数随MWCNTs加入量的增加呈上升趋势，虚部电容分数则随MWCNTs加入量增加而降低。在AC电极中加入MWCNTs，在降低电极内阻的同时可有效提高超级电容器的储能效率，并降低弛豫时间，提高其频率特性，改善电容行为。Abstract: Activated carbon was prepared from petroleum coke by chemical activation. Multi-walled carbon nanotubes (MWCNTs) were mixed with the activated carbon to form the electrode material of electric double layer capacitors. According to the relative values of impedance and capacitance in electrochemical impedance, the available capacitance and energy dissipation from resistance were evaluated. Results showed that the real part of the capacitance for this mixture was higher than for activated carbon alone when activated carbon was mixed with a mass fraction 3%-15% MWCNTs. With the increase of MWCNT content, the imaginary part of the capacitance and its percentage decreases while the real part of capacitance and its percentage increases. It was revealed that the efficiency of energy storage was improved, the relaxation time constant was decreased, the characteristic of capacitance response versus frequency was improved and the electrode resistance was decreased by the addition of MWCNTs to activated carbon.
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