Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.
Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
J Chem Phys. 2017 May 7;146(17):174701. doi: 10.1063/1.4982351.
The energy density of an electric double layer capacitor, also known as supercapacitor, depends on ion distributions in the micropores of its electrodes. Herein we study ion selectivity and partitioning of symmetric, asymmetric, and mixed ionic liquids among different pores using the classical density functional theory. We find that a charged micropore in contact with mixed ions of the same valence is always selective to the smaller ions, and the ion selectivity, which is strongest when the pore size is comparable to the ion diameters, drastically falls as the pore size increases. The partitioning behavior in ionic liquids is fundamentally different from those corresponding to ion distributions in aqueous systems whereby the ion selectivity is dominated by the surface energy and entropic effects insensitive to the degree of confinement.
双电层电容器（也称为超级电容器）的能量密度取决于其电极微孔隙中的离子分布。在此，我们使用经典密度泛函理论研究了对称、不对称和混合离子液体在不同孔隙中的离子选择性和分配。我们发现，带电荷的微孔与相同价态的混合离子接触时总是对较小的离子具有选择性，而当孔径与离子直径相当时，离子选择性最强，随着孔径的增大而急剧下降。离子液体中的分配行为与相应的水溶液中离子分布根本不同，其中离子选择性主要由表面能和与约束程度无关的熵效应决定。
