The capacitances of the negative and positive electrodes of supercapacitors, using nitrogen-doped mesoporous carbons as the active materials, in different electrolytes
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摘要: 以三聚氰胺、苯酚和甲醛为前驱体，硅溶胶为模板剂，采用溶胶-凝胶与硬模板结合的方法，制备出一系列不同氮掺杂含量（0~11.9%）、相似孔结构的中孔炭材料，系统研究了氮掺杂含量对材料在H2SO4，KOH及Et4NBF4/PC电解液体系中的正负极不对称电容行为。结果表明，氮原子的掺杂明显提升了材料在不同电解液体系中的正负极电容性能，且当氮掺杂含量为8%时性能提升最为显著。在KOH电解液体系中，含氮官能团对负极电容贡献明显高于正极，容差最高可达57.9 F/g；在H2SO4电解液体系中，正负极电容容量较为对称；在Et4NBF4/PC电解液体系中，容量的提升主要作用在负极。氮掺杂中孔炭材料正负极不对称电容行为的研究，为优化正负电极活性物质的比例进而提高整个电容器的能量密度提供了研究基础。Abstract: Nitrogen-doped mesoporous carbons (NMCs) with controllable nitrogen contents and similar pore structures were prepared by a sol-gel process coupled with hard templating method, using melamine, phenol and formaldehyde as precursors, and colloidal silica as hard templating. The effects of nitrogen doping content on the asymmetric capacitance of the mesoporous carbon in H2SO4, KOH and Et4NBF4/PC electrolyte were systematically investigated. The nitrogen-doping has significantly improved the capacitance performance, and both positive and negative electrodes deliver the highest specific capacitance at a nitrogen-doping content of around 8%. In the KOH electrolyte, the negative pseudo-capacitances is significantly higher than that of the positive ones, and the capacity difference is up to 57.9 F/g. In H2SO4 electrolyte, the nearly same capacitances for each electrode are found for all samples. And in the organic Et4NBF4/PC system, the increased capacitance is mainly attributed to the negative. The study on asymmetrical capacitance response of nitrogen-doped mesoporous carbon paves the way for optimizing the ratio of positive and negative electrode active materials, leading a higher energy density.
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