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Martins ML, Lin X, Gainaru C, Keum JK, Cummings PT, Sokolov AP, Sacci RL, Mamontov E. Structure-Dynamics Interrelation Governing Charge Transport in Cosolvated Acetonitrile/LiTFSI Solutions. J Phys Chem B 2023; 127:308-320. [PMID: 36577128 DOI: 10.1021/acs.jpcb.2c07327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Concentrated ionic solutions present a potential improvement for liquid electrolytes. However, their conductivity is limited by high viscosities, which can be attenuated via cosolvation. This study employs a series of experiments and molecular dynamics simulations to investigate how different cosolvents influence the local structure and charge transport in concentrated lithium bis(trifluoromethane-sulfonyl)imide (LiTFSI)/acetonitrile solutions. Regardless of whether the cosolvent's dielectric constant is low (for toluene and dichloromethane), moderate (acetone), or high (methanol and water), they preserve the structural and dynamical features of the cosolvent-free precursor. However, the dissimilar effects of each case must be individually interpreted. Toluene and dichloromethane reduce the conductivity by narrowing the distribution of Li+-TFSI- interactions and increasing the activation energies for ionic motions. Methanol and water broaden the distributions of Li+-TFSI- interactions, replace acetonitrile in the Li+ solvation, and favor short-range Li+-Li+ interactions. Still, these cosolvents strongly interact with TFSI-, leading to conductivities lower than that predicted by the Nernst-Einstein relation. Finally, acetone preserves the ion-ion interactions from the cosolvent-free solution but forms large solvation complexes by joining acetonitrile in the Li+ solvation. We demonstrate that cosolvation affects conductivity beyond simply changing viscosity and provide fairly unexplored molecular-scale perspectives regarding structure/transport phenomena relation in concentrated ionic solutions.
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Affiliation(s)
- Murillo L Martins
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee37996, United States
| | - Xiaobo Lin
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee37235, United States
| | - Catalin Gainaru
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Jong K Keum
- Neutron Scattering Division, Oak Ridge National Laboratory, P.O. Box 2008 MS6455, Oak Ridge, Tennessee37831, United States.,Center for Nanophase Materials Sciences, Oak Ridge, Tennessee37831, United States
| | - Peter T Cummings
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee37235, United States
| | - Alexei P Sokolov
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee37996, United States.,Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Robert L Sacci
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Eugene Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, P.O. Box 2008 MS6455, Oak Ridge, Tennessee37831, United States
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Khudozhitkov AE, Donoshita M, Stepanov AG, Philippi F, Rauber D, Hempelmann R, Kitagawa H, Kolokolov DI, Ludwig R. High‐Temperature Quantum Tunneling and Hydrogen Bonding Rearrangements Characterize the Solid‐Solid Phase Transitions in a Phosphonium‐Based Protic Ionic Liquid. Chemistry 2022; 28:e202200257. [PMID: 35187737 PMCID: PMC9311734 DOI: 10.1002/chem.202200257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Indexed: 11/11/2022]
Affiliation(s)
- Alexander E. Khudozhitkov
- Boreskov Institute of Catalysis Siberian Branch of Russian Academy of Sciences Prospekt Akademika Lavrentieva 5 Novosibirsk 630090 Russia
- Novosibirsk State University Pirogova Street 2 Novosibirsk 630090 Russia
| | - Masaki Donoshita
- Division of Chemistry Graduate School of Science Kyoto University Kitashirakawa-Oiwakecho, Sakyo-ku Kyoto 606-8502 Japan
| | - Alexander G. Stepanov
- Boreskov Institute of Catalysis Siberian Branch of Russian Academy of Sciences Prospekt Akademika Lavrentieva 5 Novosibirsk 630090 Russia
- Novosibirsk State University Pirogova Street 2 Novosibirsk 630090 Russia
| | - Frederik Philippi
- Physikalische Chemie Universität des Saarlandes Campus B2.2 66123 Saarbrücken Germany
| | - Daniel Rauber
- Physikalische Chemie Universität des Saarlandes Campus B2.2 66123 Saarbrücken Germany
| | - Rolf Hempelmann
- Physikalische Chemie Universität des Saarlandes Campus B2.2 66123 Saarbrücken Germany
| | - Hiroshi Kitagawa
- Division of Chemistry Graduate School of Science Kyoto University Kitashirakawa-Oiwakecho, Sakyo-ku Kyoto 606-8502 Japan
| | - Daniil I. Kolokolov
- Boreskov Institute of Catalysis Siberian Branch of Russian Academy of Sciences Prospekt Akademika Lavrentieva 5 Novosibirsk 630090 Russia
- Novosibirsk State University Pirogova Street 2 Novosibirsk 630090 Russia
| | - Ralf Ludwig
- Department LL&M University of Rostock Albert-Einstein-Str. 25 18059 Rostock Germany
- Institut für Chemie Abteilung für Physikalische Chemie Universität Rostock Dr.-Lorenz-Weg 2 18059 Rostock Germany
- Leibniz-Institut für Katalyse Universität Rostock e.V. Albert-Einstein-Str. 29a 18059 Rostock Germany
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Mamontov E, Osti NC, Ryder MR. Order-disorder in room-temperature ionic liquids probed via methyl quantum tunneling. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2021; 8:024303. [PMID: 33834086 PMCID: PMC8024031 DOI: 10.1063/4.0000094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 03/03/2021] [Indexed: 06/12/2023]
Abstract
Room-temperature ionic liquids are promising candidates for applications ranging from electrolytes for energy storage devices to lubricants for food and cellulose processing to compounds for pharmaceutics, biotransformation, and biopreservation. Due to the ion complexity, many room-temperature ionic liquids readily form amorphous phases upon cooling, even at modest rates. Here, we investigate two commonly studied imidazolium-based room-temperature ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, as well as their mixtures, to demonstrate how the complex interplay between the crystalline and amorphous phases is affected by the processing conditions, such as thermal history, liquid mixing, and applied pressure. We show that quantum tunneling in the cation methyl groups, measured by high-resolution inelastic neutron scattering, can be used to probe the order-disorder in room-temperature ionic liquids (crystalline vs amorphous state) that develops as a result of variable processing conditions.
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Affiliation(s)
| | - Naresh C. Osti
- Authors to whom correspondence should be addressed:; ; and
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Jafta CJ, Bridges C, Haupt L, Do C, Sippel P, Cochran MJ, Krohns S, Ohl M, Loidl A, Mamontov E, Lunkenheimer P, Dai S, Sun XG. Ion Dynamics in Ionic-Liquid-Based Li-Ion Electrolytes Investigated by Neutron Scattering and Dielectric Spectroscopy. CHEMSUSCHEM 2018; 11:3512-3523. [PMID: 30133183 DOI: 10.1002/cssc.201801321] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 07/30/2018] [Indexed: 06/08/2023]
Abstract
A detailed understanding of the diffusion mechanisms of ions in pure and doped ionic liquids remains an important aspect in the design of new ionic-liquid electrolytes for energy storage. To gain more insight into the widely used imidazolium-based ionic liquids, the relationship between viscosity, ionic conductivity, diffusion coefficients, and reorientational dynamics in the ionic liquid 3-methyl-1-methylimidazolium bis(trifluoromethanesulfonyl)imide (DMIM-TFSI) with and without lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) was examined. The diffusion coefficients for the DMIM+ cation and the role of ion aggregates were investigated by using the quasielastic neutron scattering (QENS) and neutron spin echo techniques. Two diffusion mechanisms are observed for the DMIM+ cation with and without Li-TFSI, that is, translational and local. The data additionally suggest that Li+ ion transport along with ion aggregates, known as the vehicle mechanism, may play a significant role in the ion diffusion process. These dielectric-spectroscopy investigations in a broad temperature and frequency range reveal a typical α-β-relaxation scenario. The α relaxation mirrors the glassy freezing of the dipolar ions, and the β relaxation exhibits the signatures of a Johari-Goldstein relaxation. In contrast to the translational mode detected by neutron scattering, arising from the decoupled faster motion of the DMIM+ ions, the α relaxation is well coupled to the dc charge transport, that is, the average translational motion of all three ion species in the material. The local diffusion process detected by QENS is only weakly dependent on temperature and viscosity and can be ascribed to the typical fast dynamics of glass-forming liquids.
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Affiliation(s)
- Charl J Jafta
- Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Craig Bridges
- Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Leon Haupt
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany
| | - Changwoo Do
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Pit Sippel
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany
| | - Malcolm J Cochran
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Stephan Krohns
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany
| | - Michael Ohl
- Jülich Centre for Neutron Science, Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Alois Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany
| | - Eugene Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Peter Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany
| | - Sheng Dai
- Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
- Department of Chemistry, University of Tennessee, Knoxville, TN, 37996, USA
| | - Xiao-Guang Sun
- Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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