H3PO4 activated carbons as the electrode materials of supercapacitors using an ionic liquid electrolyte
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摘要: 为了研究工业化上广泛应用的磷酸活化法所制备的活性炭在离子液体基超级电容器领域的应用潜力，本文采用磷酸作为活化剂，杉木屑作为原料，制备活性炭电极材料。采用N2吸附/脱附等温线、扫描电子显微镜、X射线光电子能谱等方法表征了活性炭的孔隙结构与形态。采用[BMIM][PF6]离子液体作为电解质，通过循环伏安法、恒电流充/放电和交流阻抗等方法研究了磷酸活性炭作为超级电容器电极材料的电化学性能。结果显示，在800~950℃温度下，通过调节浸渍比，磷酸活化法可以制备出中孔孔容比例达66%以上的中孔活性炭；在浸渍比为3：1的条件下，所制得的活性炭电极的比电容量可达162 F/g，组装成对称电容器的能量密度可达22.5 Wh/kg （在0.5 A/g下）；且具有较好的倍率特性和循环稳定性，在5 A/g的电流密度下充/放电5 000次后容量保持率为86%。因此，高温磷酸活化法是一种制备离子液体电解质超级电容器活性炭的方法。Abstract: H3PO4-activated carbons were prepared from Chinese fir sawdust, and their pore structure, surface chemistry and morphology were characterized by nitrogen adsorption, SEM and XPS. Their electrochemical performance as electrode materials for supercapacitors using[BMIM] [PF6] as the electrolyte was investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. Results indicate that H3PO4 activation at 800 to 950℃ produces highly developed mesopores with a volume percentage as high as 66% of the total porosity. The carbon prepared at a H3PO4 to sawdust mass ratio of 3:1 has a specific capacitance of 162 F/g and delivers an energy density of 22.5 Wh/kg at 0.5 A/g. The specific capacitance remains at 86% after 5 000 cycles at 5 A/g, suggesting good cycling stability and rate capability. H3PO4 activation is an effective method to prepare activated carbons for use in ionic liquid-based supercapacitors.
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Key words:
- H3PO4 activation /
- Activated carbon /
- Ionic liquid /
- Supercapacitor
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