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Effects of dilution in ionic liquid supercapacitors

Varner, Samuel and Wang, Zhen-Gang (2022) Effects of dilution in ionic liquid supercapacitors. Physical Chemistry Chemical Physics, 24 (44). pp. 27362-27374. ISSN 1463-9076. doi:10.1039/d2cp03398d.

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Room-temperature ionic liquids (RTILs) are synthetic electrolytes that have a large electrochemical stability window, making them attractive candidates for electric double-layer capacitor (EDLC) applications. Due to their high viscosities and low ionic conductivities, RTILs are often diluted with organic solvent for practical use. We study the effects of dilution on the performance of RTIL EDLCs using a simple mean-field model. We find that dilution diminishes the unfavorable hysteresis that results from a spontaneous surface charge separation (SSCS). As a result, the RTIL concentration can be used to modulate the proximity to the SSCS transition, and maximize capacitance. The interplay between the concentration and the correlation strength gives rise to complex zero-potential phase behavior, including a tricritical point and a λ-line, very similar to the Blume–Capel dilute Ising model. Additionally, electrodes that are solvophilic aid in the prevention of SSCS by drawing solvent molecules to the electrode and displacing ions. Solvophilic electrodes give rise to a phase transition at finite potential where the surface charge rapidly increases with a small increase in potential, leading to a substantial increase in capacitance and energy storage.

Item Type:Article
Related URLs:
URLURL TypeDescription
Varner, Samuel0000-0002-1365-1027
Wang, Zhen-Gang0000-0002-3361-6114
Additional Information:S. V. is supported by the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research, Department of Energy Computational Science Graduate Fellowship under Award Number DE-SC0022158. Z.-G. W. acknowledges financial support from the Hong Kong Quantum AI Lab Ltd.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0022158
Hong Kong Quantum AI Lab Ltd.UNSPECIFIED
Issue or Number:44
Record Number:CaltechAUTHORS:20221121-712922500.32
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117965
Deposited By: Research Services Depository
Deposited On:02 Dec 2022 23:46
Last Modified:02 Dec 2022 23:46

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