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Published July 27, 2021 | Supplemental Material
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Effects of Confinement and Ion Adsorption in Ionic Liquid Supercapacitors with Nanoporous Electrodes


We investigate the effects of pore size and ion adsorption on the room-temperature ionic liquid capacitor with nanoporous electrodes, with a focus on optimizing the capacitance and energy storage. Using a recently developed modified BSK model accounting for both ion correlations and nonelectrostatic interactions, we find that ion crowding proximate to the electrode surface induced by the spontaneous charge separation due to strong ion correlations is responsible for the anomalous increase in the capacitance with decreasing pore sizes observed in experiments. Reducing the strength of ion correlations increases the capacitance and suppresses the anomalous size dependence. For a given pore size, the capacitance peak diverges when the ion correlation strength α reaches a critical value, α_(sc,L). The capacitance peak shifts to smaller pore size as α decreases because of rapid decrease of α_(sc,L) with decreasing pore size. Asymmetric preferential ion adsorption is shown to lead to significantly enhanced energy storage close to the transition point for any pore sizes. For a given correlation strength, the energy storage is optimal at a pore size where α = α_(sc,L).

Additional Information

© 2021 American Chemical Society. Received 24 March 2021. Accepted 22 June 2021. Published online 6 July 2021. Z.L. acknowledges financial support from the Fundamental Research Funds for the Provincial Universities of Zhejiang (No.SJLY2020006), Foundation of Zhejiang Educational Committee (No.Y20173 7177), and Natural Science Foundation of Ningbo (No.202003N4106). She also acknowledges support from the K.C.Wong Magna Fund in Ningbo University. Z.-G.W. acknowledges financial support from the Hong Kong Quantum AI Lab Ltd. The authors declare no competing financial interest.

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