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Mixed Ionic Liquid Improves Electrolyte Dynamics in Supercapacitors
Journal article   Open access

Mixed Ionic Liquid Improves Electrolyte Dynamics in Supercapacitors

Naresh C Osti, Alejandro Gallegos, Boris Dyatkin, Jianzhong Wu, Yury Gogotsi and Eugene Mamontov
Journal of physical chemistry. C, v 122(19), pp 10476-10481
17 May 2018
url
https://doi.org/10.1021/acs.jpcc.8b02521View
Published, Version of Record (VoR) Open

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 (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. 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.

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Collaboration types
Domestic collaboration
Web of Science research areas
Chemistry, Physical
Materials Science, Multidisciplinary
Nanoscience & Nanotechnology
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