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arXiv 2107.14337cond-mat.mtrl-sci
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碳-碳超级电容器:超越平均孔径——电解质限域与不可接触孔隙如何影响电容

Carbon-carbon supercapacitors: Beyond the average pore size or how electrolyte confinement and inaccessible pores affect the capacitance

El Hassane Lahrar, Patrice Simon, Céline Merlet

AI总结:

本研究通过分子模拟发现,平均孔径相同的多孔碳电极因形貌差异,规整结构碳的电容远高于无序碳,揭示了电解质限域和不可接触孔隙对电容的影响,为储能材料的计算筛选提供了新思路。

摘要:

碳-碳超级电容器是高功率电化学储能系统,通过电极-电解质界面的可逆离子吸附存储能量。由于用作电极的多孔碳结构复杂,厘清这些系统中的结构-性能关系仍是一项挑战。本研究对两种基于纳米多孔电极的模型超级电容器开展分子模拟,两种电极的平均孔径(常用于多孔材料比较的参数)相同,但形貌存在差异。研究发现,结构更规整、孔径分布明确的碳材料,其电容远高于结构更无序、孔径分布更宽的碳材料。通过分析限域电解质的结构发现,与无序碳相比,规整碳中吸附的离子数量更多,限域程度也更强,这两方面都有利于实现更好的电荷分离,从而提升电容。此外,无序电极中含有大量从未与电解质接触的碳原子,这些碳原子的电荷接近零,因此不参与电荷存储过程。吸附离子的总量和限域程度随外加电势的变化很小,因此本研究为计算上可实现的筛选策略开辟了道路。

英文摘要:

Carbon-carbon supercapacitors are high power electrochemical energy storage systems which store energy through reversible ion adsorption at the electrode-electrolyte interface. Due to the complex structure of the porous carbons used as electrodes, extracting structure-property relationships in these systems remains a challenge. In this work, we conduct molecular simulations of two model supercapacitors based on nanoporous electrodes with the same average pore size, a property often used when comparing porous materials, but different morphologies. We show that the carbon with the more ordered structure, and a well defined pore size, has a much higher capacitance than the carbon with the more disordered structure, and a broader pore size distribution. We analyze the structure of the confined electrolyte and show that the ions adsorbed in the ordered carbon are present in larger quantities and are also more confined than for the disordered carbon. Both aspects favor a better charge separation and thus a larger capacitance. In addition, the disordered electrodes contain a significant amount of carbon atoms which are never in contact with the electrolyte, carry a close to zero charge and are thus not involved in the charge storage. The total quantities of adsorbed ions and degrees of confinement do not change much with the applied potential and as such, this work opens the door to computationally tractable screening strategies.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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