A universal model for nanoporous carbon supercapacitors applicable to diverse pore regimes, carbon materials, and electrolytes
A universal model for nanoporous carbon supercapacitors applicable to diverse pore regimes, carbon materials, and electrolytes
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DOI：
10.1002/chem.200800639
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发表时间：
2008-01-01
影响因子：
4.3
通讯作者：
Meunier, Vincent
中科院分区：
文献类型：
--
作者：
Huang, Jingsong;Sumpter, Bobby G.;Meunier, Vincent
超级电容器，俗称双电层电容器(EDLC)，是一种新型的储能装置，有可能在需要高功率密度的应用中取代电池。针对纳米多孔碳超级电容器的最新实验突破，我们提出了一种考虑孔曲率的启发式理论模型，取代了基于传统平行板电容器的EDLC模型。当介孔尺寸为2-50 nm时，反离子进入介孔碳材料并接近孔壁形成双圆柱电容器(EDCC)；在微孔区域(50 Nm)，孔足够大，孔曲率不再显著时，EDCC模型可以自然地简化为EDLC模型。我们给出了不同孔区下的密度泛函理论计算和已有实验数据的详细分析，表明孔曲率对纳米多孔碳材料的超级电容器性能有显著的影响。结果表明，EDCC/EWCC模型适用于含不同炭材料(包括活性碳材料、模板碳材料和新型碳化物衍生碳材料)和多种电解液(包括有机电解液，如乙腈中的四乙基四氟硼酸铵(TEABF(4))和四乙基甲基磺酸铵(TEAS))、硫酸和KOH水溶液中的碳超级电容器，甚至包括离子液体电解液，如1-乙基-3-甲基咪唑双(三氟甲磺酸)亚胺(EMI-TFSI)。EDCC/EWCC模型允许超级电容器的性能与孔尺寸、比表面积、德拜长度、电解液浓度和介电常数以及溶质离子尺寸相关联，这可能为通过实验系统地优化碳超级电容器的性能提供支持。在新模型的基础上，我们还讨论了动力学溶剂化/去溶化过程、多峰(相对于单峰)孔径分布和面外(相对于面内)电容器对超级电容器电化学性能的影响。
Supercapacitors, commonly called electric double-layer capacitors (EDLCs), are emerging as a novel type of energy-storage device with the potential to substitute batteries in applications that require high power densities. In response to the latest experimental breakthrough in nanoporous carbon supercapacitors, we propose a heuristic theoretical model that takes pore curvature into account as a replacement for the EDLC model, which is based on a traditional parallel-plate capacitor. When the pore size is in the mesopofe regime (2-50 nm), counterions enter mesoporous carbon materials and approach the pore wall to form an electric double-cylinder capacitor (EDCC); in the micropore regime (50 nm) at which pores are large enough so that pore curvature is no longer significant, the EDCC model can be reduced naturally to the EDLC model. We present density functional theory calculations and detailed analyses of available experimental data in various pore regimes, which show the significant effects of pore curvature on the supercapacitor properties of nanoporous carbon materials. It is shown that the EDCC/EWCC model is universal for carbon supercapacitors with diverse carbon materials, including activated carbon materials, template carbon materials, and novel carbide-derived carbon materials, and with diverse electrolytes, including organic electrolytes, such as tetraethylammonium tetrafluoroborate (TEABF(4)) and tetraethylammonium methylsulfonate (TEAMS) in acetonitrile, aqueous H2SO4 and KOH electrolytes, and even an ionic liquid electrolyte, such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI). The EDCC/EWCC model allows the supercapacitor properties to be correlated with pore size, specific surface area, Debye length, electrolyte concentration and dielectric constant, and solute ion size It may lend support for the systematic optimization of the properties of carbon supercapacitors through experiments. On the basis of the insight obtained from the new model, we also discuss the effects of the kinetic solvation/desolvation process, multimodal (versus unimodal) pore size distribution, and exohedral (versus endohedral) capacitors on the electrochemical properties of supercapacitors.