A superionic state in nano-porous double-layer capacitors: insights from Monte Carlo simulations
A superionic state in nano-porous double-layer capacitors: insights from Monte Carlo simulations
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DOI：
10.1039/c1cp20798a
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发表时间：
2011-01-01
影响因子：
3.3
通讯作者：
Kornyshev, A. A.
中科院分区：
文献类型：
--
作者：
Kondrat, S.;Georgi, N.;Kornyshev, A. A.
最近观察到的基于离子液体的纳米多孔超级电容器的异常性质[C. Largot等人，J. Am.化学会，2008，130，2730-2731]已经引起了很多关注。在这里，我们提出了一个模型离子液体在狭缝状金属纳米孔的Monte Carlo模拟。我们发现，指数屏蔽的孔内的离子的静电相互作用，以及图像电荷吸引的离子的孔表面，导致的“异常”的电容增加，减少孔的宽度。模拟结果与实验数据吻合较好。作为电压的函数的电容对于低电压几乎是恒定的，并且在某个阈值电压以上消失。对于非常窄的孔，这两个区域被峰分开。随着孔径的增加，峰变成一个凸点，并消失为宽孔。这种效应与高密度下用反离子填充纳米孔的电压诱导的特定特性有关，尚待实验验证。
Recently observed anomalous properties of ionic-liquid-based nanoporous supercapacitors [C. Largot et al., J. Am. Chem. Soc., 2008, 130, 2730-2731] have attracted much attention. Here we present Monte Carlo simulations of a model ionic liquid in slit-like metallic nanopores. We show that exponential screening of the electrostatic interactions of ions inside a pore, as well as the image-charge attraction of ions to the pore surface, lead to the 'anomalous' increase of the capacitance with decreasing the pore width. The simulation results are in good agreement with the experimental data. The capacitance as a function of voltage is almost constant for low voltages and vanishes above a certain threshold voltage. For very narrow pores, these two regions are separated by a peak. With increase of the pore size the peak turns into a bump and disappears for wide pores. This effect, related to a specific character of the voltage-induced filling of nanopores with counterions at high densities, is yet to be verified experimentally.