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Surface Charge Density in Electrical Double Layer Capacitors with Nanoscale Cathode–Anode Separation

Qing, Leying and Zhao, Shuangliang and Wang, Zhen-Gang (2021) Surface Charge Density in Electrical Double Layer Capacitors with Nanoscale Cathode–Anode Separation. Journal of Physical Chemistry B, 125 (2). pp. 625-636. ISSN 1520-6106. https://resolver.caltech.edu/CaltechAUTHORS:20210112-091401503

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Abstract

Using a dynamic density functional theory, we study the charging dynamics, the final equilibrium structure, and the energy storage in an electrical double layer capacitor with nanoscale cathode–anode separation in a slit geometry. We derive a simple expression for the surface charge density that naturally separates the effects of the charge polarization due to the ions from those due to the polarization of the dielectric medium and allows a more intuitive understanding of how the ion distribution within the cell affects the surface charge density. We find that charge neutrality in the half-cell does not hold during the dynamic charging process for any cathode–anode separation, and also does not hold at the final equilibrium state for small separations. Therefore, the charge accumulation in the half-cell in general does not equal the surface charge density. The relationships between the surface charge density and the charge accumulation within the half-cell are systematically investigated by tuning the electrolyte concentration, cathode–anode separation, and applied voltage. For high electrolyte concentrations, we observe charge inversion at which the charge accumulation exceeds the surface charge at special values of the separation. In addition, we find that the energy density has a maximum at intermediate electrolyte concentrations for a high applied voltage.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/acs.jpcb.0c09332DOIArticle
ORCID:
AuthorORCID
Zhao, Shuangliang0000-0002-9547-4860
Wang, Zhen-Gang0000-0002-3361-6114
Additional Information:© 2021 American Chemical Society. Received 14 October 2020. Revised 17 December 2020. Published online 6 January 2021. Published as part of The Journal of Physical Chemistry virtual special issue “Carol K. Hall Festschrift”. L.Q. is grateful to the China Scholarship Council for supporting her visit at the California Institute of Technology. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
China Scholarship CouncilUNSPECIFIED
Subject Keywords:Equilibrium, Electrical properties, Electrodes, Ions, Surface charge
Issue or Number:2
Record Number:CaltechAUTHORS:20210112-091401503
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210112-091401503
Official Citation:Surface Charge Density in Electrical Double Layer Capacitors with Nanoscale Cathode–Anode Separation. Leying Qing, Shuangliang Zhao, and Zhen-Gang Wang. The Journal of Physical Chemistry B 2021 125 (2), 625-636; DOI: 10.1021/acs.jpcb.0c09332
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107417
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:12 Jan 2021 17:36
Last Modified:22 Jan 2021 22:00

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