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Title: Mixed Ionic Liquid Improves Electrolyte Dynamics in Supercapacitors

Abstract

Well-tailored mixtures of distinct ionic liquids can act as optimal electrolytes that extend the operating electrochemical window and improve charge storage density in supercapacitors. Here, we explore two room-temperature ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimTFSI) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF 4). We study their electric double-layer behavior in the neat state and as binary mixtures on the external surfaces of onion-like carbon electrodes using quasielastic neutron scattering (QENS) and classical density functional theory techniques. Computational results reveal that a mixture with 4:1 EmimTFSI/EmimBF 4 volume ratio displaces the larger [TFSI ] anions with smaller [BF 4 ] ions, leading to an excess adsorption of [Emim +] cations near the electrode surface. These findings are corroborated by the manifestation of nonuniform ion diffusivity change, complementing the description of structural modifications with changing composition, from QENS measurements. In conclusion, molecular-level understanding of ion packing near electrodes provides insight for design of ionic liquid formulations that enhance the performance of electrochemical energy storage devices.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [4]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of California, Riverside, CA (United States)
  3. Drexel Univ., Philadelphia, PA (United States); U.S. Naval Research Lab., Washington, D.C. (United States)
  4. Drexel Univ., Philadelphia, PA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Energy Frontier Research Centers (EFRC) (United States). Fluid Interface Reactions, Structures and Transport Center (FIRST)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1439150
Alternate Identifier(s):
OSTI ID: 1482459
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 19; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Osti, Naresh C., Gallegos, Alejandro, Dyatkin, Boris, Wu, Jianzhong, Gogotsi, Yury, and Mamontov, Eugene. Mixed Ionic Liquid Improves Electrolyte Dynamics in Supercapacitors. United States: N. p., 2018. Web. doi:10.1021/acs.jpcc.8b02521.
Osti, Naresh C., Gallegos, Alejandro, Dyatkin, Boris, Wu, Jianzhong, Gogotsi, Yury, & Mamontov, Eugene. Mixed Ionic Liquid Improves Electrolyte Dynamics in Supercapacitors. United States. doi:10.1021/acs.jpcc.8b02521.
Osti, Naresh C., Gallegos, Alejandro, Dyatkin, Boris, Wu, Jianzhong, Gogotsi, Yury, and Mamontov, Eugene. Thu . "Mixed Ionic Liquid Improves Electrolyte Dynamics in Supercapacitors". United States. doi:10.1021/acs.jpcc.8b02521. https://www.osti.gov/servlets/purl/1439150.
@article{osti_1439150,
title = {Mixed Ionic Liquid Improves Electrolyte Dynamics in Supercapacitors},
author = {Osti, Naresh C. and Gallegos, Alejandro and Dyatkin, Boris and Wu, Jianzhong and Gogotsi, Yury and Mamontov, Eugene},
abstractNote = {Well-tailored mixtures of distinct ionic liquids can act as optimal electrolytes that extend the operating electrochemical window and improve charge storage density in supercapacitors. Here, we explore two room-temperature ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimTFSI) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4). We study their electric double-layer behavior in the neat state and as binary mixtures on the external surfaces of onion-like carbon electrodes using quasielastic neutron scattering (QENS) and classical density functional theory techniques. Computational results reveal that a mixture with 4:1 EmimTFSI/EmimBF4 volume ratio displaces the larger [TFSI–] anions with smaller [BF4–] ions, leading to an excess adsorption of [Emim+] cations near the electrode surface. These findings are corroborated by the manifestation of nonuniform ion diffusivity change, complementing the description of structural modifications with changing composition, from QENS measurements. In conclusion, molecular-level understanding of ion packing near electrodes provides insight for design of ionic liquid formulations that enhance the performance of electrochemical energy storage devices.},
doi = {10.1021/acs.jpcc.8b02521},
journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 19,
volume = 122,
place = {United States},
year = {2018},
month = {4}
}

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Cited by: 5 works
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Works referencing / citing this record:

Status review on the MEMS-based flexible supercapacitors
journal, June 2019

  • Patil, Swati; Lee, Dong-Weon
  • Journal of Micromechanics and Microengineering, Vol. 29, Issue 9
  • DOI: 10.1088/1361-6439/ab1c9b

Status review on the MEMS-based flexible supercapacitors
journal, June 2019

  • Patil, Swati; Lee, Dong-Weon
  • Journal of Micromechanics and Microengineering, Vol. 29, Issue 9
  • DOI: 10.1088/1361-6439/ab1c9b