1
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Shah NJ, Fang C, Osti NC, Mamontov E, Yu X, Lee J, Watanabe H, Wang R, Balsara NP. Nanosecond solvation dynamics in a polymer electrolyte for lithium batteries. NATURE MATERIALS 2024; 23:664-669. [PMID: 38413811 DOI: 10.1038/s41563-024-01834-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 02/06/2024] [Indexed: 02/29/2024]
Abstract
Solvation dynamics critically affect charge transport. Spectroscopic experiments and computer simulations show that these dynamics in aqueous systems occur on a picosecond timescale. In the case of organic electrolytes, however, conflicting values ranging from 1 to several 100 picoseconds have been reported. We resolve this conflict by studying mixtures of an organic polymer and a lithium salt. Lithium ions coordinate with multiple polymer chains, resulting in temporary crosslinks. Relaxation of these crosslinks, detected by quasielastic neutron scattering, are directly related to solvation dynamics. Simulations reveal a broad spectrum of relaxation times. The average timescale for solvation dynamics in both experiment and simulation is one nanosecond. We present the direct measurement of ultraslow dynamics of solvation shell break-up in an electrolyte.
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Affiliation(s)
- Neel J Shah
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Chao Fang
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Naresh C Osti
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Eugene Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Xiaopeng Yu
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Jaeyong Lee
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | | | - Rui Wang
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA.
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Nitash P Balsara
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA.
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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2
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Lim C, Jeon J, Park K, Liang C, Chae Y, Kwak K, Cho M. Revisiting Ultrafast Dynamics in Carbonate-Based Electrolytes for Li-Ion Batteries: Clarifying 2D-IR Cross-Peak Interpretation. J Phys Chem B 2023; 127:9566-9574. [PMID: 37905968 DOI: 10.1021/acs.jpcb.3c05480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Understanding chemical exchange in carbonate-based electrolytes employed in Li-ion batteries (LIBs) is crucial for elucidating ion transport mechanisms. Ultrafast two-dimensional (2D) IR spectroscopy has been widely used to investigate the solvation structure and dynamics of Li-ions in organic carbonate-based electrolytes. However, the interpretation of cross-peaks observed in picosecond carbonyl stretch 2D-IR spectra has remained contentious. These cross-peaks could arise from various phenomena, including vibrational couplings between neighboring carbonyl groups in the first solvation shell around Li-ions, vibrational excitation transfers between carbonyl groups in distinct solvation environments, and local heating effects. Therefore, it is imperative to resolve the interpretation of 2D-IR cross-peaks to avoid misinterpretations regarding ultrafast dynamics found in LIB carbonate-based electrolytes. In this study, we have taken a comprehensive investigation of carbonate-based electrolytes utilizing 2D-IR spectroscopy and molecular dynamics (MD) simulations. Through meticulous analyses and interpretations, we have identified that the cross-peaks observed in the picosecond 2D-IR spectra of LIB electrolytes predominantly arise from intermolecular vibrational excitation transfer processes between the carbonyl groups of Li-bound and free carbonate molecules. We further discuss the limitations of employing a picosecond 2D-IR spectroscopic technique to study chemical exchange and intermolecular vibrational excitation transfer processes, particularly when the effects of the molecular photothermal process cannot be ignored. Our findings shed light on the dynamics of LIB electrolytes and resolve the controversy related to 2D-IR cross-peaks. By discerning the origin of these features, we could provide valuable insights for the design and optimization of next-generation Li-ion batteries.
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Affiliation(s)
- Chaiho Lim
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Jonggu Jeon
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
| | - Kwanghee Park
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Chungwen Liang
- Creyon Bio Inc., San Diego, California 92121, United States
| | - Yeongseok Chae
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Kyungwon Kwak
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Minhaeng Cho
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
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3
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Luo Z, Burrows SA, Smoukov SK, Fan X, Boek ES. Extension of the TraPPE Force Field for Battery Electrolyte Solvents. J Phys Chem B 2023; 127:2224-2236. [PMID: 36862420 PMCID: PMC10026065 DOI: 10.1021/acs.jpcb.2c06993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
Abstract
Optimizing electrolyte formulations is key to improving performance of Li-/Na-ion batteries, where transport properties (diffusion coefficient, viscosity) and permittivity need to be predicted as functions of temperature, salt concentration and solvent composition. More efficient and reliable simulation models are urgently needed, owing to the high cost of experimental methods and the lack of united-atom molecular dynamics force fields validated for electrolyte solvents. Here the computationally efficient TraPPE united-atom force field is extended to be compatible with carbonate solvents, optimizing the charges and dihedral potential. Computing the properties of electrolyte solvents, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and dimethoxyethane (DME), we observe that the average absolute errors in the density, self-diffusion coefficient, permittivity, viscosity, and surface tension are approximately 15% of the corresponding experimental values. Results compare favorably to all-atom CHARMM and OPLS-AA force fields, offering computational performance improvement of at least 80%. We further use TraPPE to predict the structure and properties of LiPF6 salt in these solvents and their mixtures. EC and PC form complete solvation shells around Li+ ions, while the salt in DMC forms chain-like structures. In the poorest solvent, DME, LiPF6 forms globular clusters despite DME's higher permittivity than DMC.
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Affiliation(s)
- Zhifen Luo
- State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, 127 West Youyi Road, Xi'an, Shaanxi 710072, People's Republic of China
| | - Stephen A Burrows
- Chemical Engineering and Renewable Energy, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Stoyan K Smoukov
- Chemical Engineering and Renewable Energy, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Xiaoli Fan
- State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, 127 West Youyi Road, Xi'an, Shaanxi 710072, People's Republic of China
| | - Edo S Boek
- Chemical Engineering and Renewable Energy, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
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4
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Cho M. Molecular Photothermal Effects on Time-Resolved IR Spectroscopy: Solute-Solvent Intermolecular Energy Transfer. J Phys Chem B 2023; 127:300-307. [PMID: 36576754 DOI: 10.1021/acs.jpcb.2c07043] [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
Time-resolved IR pump-probe (IR-PP) and two-dimensional IR (2D-IR) spectroscopy are valuable tools for studying ultrafast chemical and biological processes in solutions. However, the corresponding signals at long times are obscured by the molecular photothermal effects resulting from the heat dissipation of vibrationally photoexcited molecules to the surroundings. Recently, a phenomenology model was used to describe molecular photothermal effects on IR-PP signals and the diagonal and cross-peaks of 2D-IR spectra at long pump-probe delay times. Here, we consider the thermal diffusion equation with a time-dependent heat source term to describe the solute-solvent energy transfer process. An approximate solution to the nonhomogeneous differential equation shows that the molecular photothermal effect is determined by the mean intermolecular distance between IR-absorbing molecules. We show that the time profile of heat dissipation from a vibrationally excited molecule to the surroundings, which provides information about the mechanisms involved in the solute-solvent intermolecular energy transfer process in solutions, can be directly measured by analyzing the molecular photothermal IR-PP and 2D-IR signals. We anticipate that the present work can be used to interpret local heating-induced time-resolved IR spectroscopic signals and understand the rate of and the mechanisms involved in the conversion from high-frequency molecular vibrational energy to solvent kinetic energy in condensed phases.
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Affiliation(s)
- Minhaeng Cho
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea.,Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
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5
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Yan F, Mukherjee K, Maroncelli M, Kim HJ. Infrared Spectroscopy of Li + Solvation in EmimBF 4 and in Propylene Carbonate: Ab Initio Molecular Dynamics and Experiment. J Phys Chem B 2022; 126:9643-9662. [DOI: 10.1021/acs.jpcb.2c06326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Fangyong Yan
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Kallol Mukherjee
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Mark Maroncelli
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Hyung J. Kim
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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6
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Cho M. Molecular photothermal effects on time-resolved IR spectroscopy. J Chem Phys 2022; 157:124201. [DOI: 10.1063/5.0108826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Time-resolved IR pump-probe (IR-PP) and two-dimensional IR (2D-IR) spectroscopy are valuable techniques for studying various ultrafast chemical and biological processes in solutions. The time-dependent changes of nonlinear IR signals reflecting fast molecular processes such as vibrational energy transfer and chemical exchange provide invaluable information on the rates and mechanisms of solvation dynamics and structural transitions of multi-species vibrationally interacting molecular systems. However, due to the intrinsic difficulties in distinguishing the contributions of molecule-specific processes to the time-resolved IR signals from those resulting from local heating, it becomes challenging to interpret time-resolved IR-PP and 2D-IR spectra exhibiting transient growing-in spectral components and cross-peaks unambiguously. Here, theoretical considerations of various effects of vibrational coupling, energy transfer, chemical exchange, the generation of hot ground states, molecular photothermal process, and their combinations on the lineshapes and time-dependent intensities of IR-PP spectra and 2D-IR diagonal and cross-peaks are presented. We anticipate that the present work will help researchers using IR pump-probe and 2D-IR techniques to distinguish local heating-induced photothermal signals from genuine nonlinear IR signals.
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Affiliation(s)
- Minhaeng Cho
- Chemistry, Korea University, Korea, Republic of (South Korea)
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7
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Dereka B, Lewis NHC, Zhang Y, Hahn NT, Keim JH, Snyder SA, Maginn EJ, Tokmakoff A. Exchange-Mediated Transport in Battery Electrolytes: Ultrafast or Ultraslow? J Am Chem Soc 2022; 144:8591-8604. [PMID: 35470669 DOI: 10.1021/jacs.2c00154] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Understanding the mechanisms of charge transport in batteries is important for the rational design of new electrolyte formulations. Persistent questions about ion transport mechanisms in battery electrolytes are often framed in terms of vehicular diffusion by persistent ion-solvent complexes versus structural diffusion through the breaking and reformation of ion-solvent contacts, i.e., solvent exchange events. Ultrafast two-dimensional (2D) IR spectroscopy can probe exchange processes directly via the evolution of the cross-peaks on picosecond time scales. However, vibrational energy transfer in the absence of solvent exchange gives rise to the same spectral signatures, hiding the desired processes. We employ 2D IR on solvent resonances of a mixture of acetonitrile isotopologues to differentiate chemical exchange and energy-transfer dynamics in a comprehensive series of Li+, Mg2+, Zn2+, Ca2+, and Ba2+ bis(trifluoromethylsulfonyl)imide electrolytes from the dilute to the superconcentrated regime. No exchange phenomena occur within at least 100 ps, regardless of the ion identity, salt concentration, and presence of water. All of the observed spectral dynamics originate from the intermolecular energy transfer. These results place the lower experimental boundary on the ion-solvent residence times to several hundred picoseconds, much slower than previously suggested. With the help of MD simulations and conductivity measurements on the Li+ and Zn2+ systems, we discuss these results as a continuum of vehicular and structural modalities that vary with concentration and emphasize the importance of collective electrolyte motions to ion transport. These results hold broadly applicable to many battery-relevant ions and solvents.
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Affiliation(s)
- Bogdan Dereka
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States.,Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Nicholas H C Lewis
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States.,Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Yong Zhang
- Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Nathan T Hahn
- Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Material, Physical and Chemical Sciences Center, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Jonathan H Keim
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Scott A Snyder
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Edward J Maginn
- Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Andrei Tokmakoff
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States.,Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States
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8
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Rushing J, Stern CM, Elgrishi N, Kuroda DG. Tale of a "Non-interacting" Additive in a Lithium-Ion Electrolyte: Effect on Ionic Speciation and Electrochemical Properties. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:2141-2150. [PMID: 35145574 PMCID: PMC8820140 DOI: 10.1021/acs.jpcc.1c09193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 12/16/2021] [Indexed: 06/14/2023]
Abstract
New lithium electrolytes compatible with high energy density cells are critical for lithium metal battery applications, but dendrite formation associated with the use of dilute organic electrolytes complicates their realization. High-concentration electrolytes mitigate some of the issues of the electrolytes but introduce additional problems, such as low conductivity and high cost. Hence, pseudo-concentrated electrolytes, wherein a co-solvent is added to a dilute electrolyte, have been presented as a possible alternative to both dilute and concentrated electrolytes. However, the effect that the co-solvent has on the electrolyte properties at both macroscopic and microscopic levels is unknown. Here, a study of the structure and electrochemical properties of two electrolytes as a function of co-solvent concentration is presented using an array of spectroscopies (FTIR, ATR-FTIR, and nuclear magnetic resonance) and computational methods (density functional theory calculations). The chosen electrolytes comprised two different lithium salts (LiPF6 and LiTFSI) in a mixture of dimethyl carbonate (DMC) with 1,1,1,3,3-pentafluorobutane (PFB) as the co-solvent. Our results show that in the case of the LiPF6/DMC electrolyte, the addition of a co-solvent (PFB) with a larger dielectric constant results in the strengthening of the lithium-anion interaction and the formation of aggregate species since PFB does not interact with the anion. Conversely, in the LiTFSI/DMC electrolyte, the co-solvent appears to interact with the anion via hydrogen bonds, which leads to the dissociation of contact ion pairs. The change in ionic speciation of the electrolytes upon addition of PFB provides a reasonable framework to explain the different trends in both the bulk and interfacial macroscopic properties, such as conductivity, viscosity, and electrochemical stability. Overall, our findings demonstrate that the interactions between the anion and the co-solvent must be taken into consideration when adding a co-solvent because they play a major role in determining the final electrolyte properties.
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9
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Hou T, Fong KD, Wang J, Persson KA. The solvation structure, transport properties and reduction behavior of carbonate-based electrolytes of lithium-ion batteries. Chem Sci 2021; 12:14740-14751. [PMID: 34820089 PMCID: PMC8597828 DOI: 10.1039/d1sc04265c] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 09/16/2021] [Indexed: 11/21/2022] Open
Abstract
Despite the extensive employment of binary/ternary mixed-carbonate electrolytes (MCEs) for Li-ion batteries, the role of each ingredient with regards to the solvation structure, transport properties, and reduction behavior is not fully understood. Herein, we report the atomistic modeling and transport property measurements of the Gen2 (1.2 M LiPF6 in ethylene carbonate (EC) and ethyl methyl carbonate (EMC)) and EC-base (1.2 M LiPF6 in EC) electrolytes, as well as their mixtures with 10 mol% fluoroethylene carbonate (FEC). Due to the mixing of cyclic and linear carbonates, the Gen2 electrolyte is found to have a 60% lower ion dissociation rate and a 44% faster Li+ self-diffusion rate than the EC-base electrolyte, while the total ionic conductivities are similar. Moreover, we propose for the first time the anion–solvent exchange mechanism in MCEs with identified energetic and electrostatic origins. For electrolytes with additive, up to 25% FEC coordinates with Li+, which exhibits a preferential reduction that helps passivate the anode and facilitates an improved solid electrolyte interphase. The work provides a coherent computational framework for evaluating mixed electrolyte systems. The different roles of the anion, cyclic and linear carbonates, and additive in mixed-carbonate electrolytes are revealed. The anion–solvent exchange mechanism and factors influencing the solid electrolyte interphase (SEI) formation are deciphered.![]()
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Affiliation(s)
- Tingzheng Hou
- Department of Materials Science and Engineering, University of California Berkeley 210 Hearst Mining Building Berkeley California 94720 USA.,Energy Technologies Area, Lawrence Berkeley National Laboratory Berkeley California 94720 USA
| | - Kara D Fong
- Energy Technologies Area, Lawrence Berkeley National Laboratory Berkeley California 94720 USA.,Department of Chemical and Biomolecular Engineering, University of California Berkeley CA 94720 USA
| | - Jingyang Wang
- Department of Materials Science and Engineering, University of California Berkeley 210 Hearst Mining Building Berkeley California 94720 USA.,Materials Sciences Division, Lawrence Berkeley National Laboratory Berkeley California 94720 USA
| | - Kristin A Persson
- Department of Materials Science and Engineering, University of California Berkeley 210 Hearst Mining Building Berkeley California 94720 USA.,The Molecular Foundry, Lawrence Berkeley National Laboratory Berkeley California 94720 USA
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10
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Lim C, Kim JH, Chae Y, Lee KK, Kwak K, Cho M. Solvation Structure around Li + Ions in Organic Carbonate Electrolytes: Spacer-Free Thin Cell IR Spectroscopy. Anal Chem 2021; 93:12594-12601. [PMID: 34491717 DOI: 10.1021/acs.analchem.1c02127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Organic carbonate electrolytes are widely used materials for lithium-ion batteries. However, detailed solvation structures and solvent coordination numbers (CNs) of lithium cations in such solutions have not been accurately described nor determined yet. Because transmission-type IR spectroscopy is not of use for measuring the carbonyl stretch modes of electrolytes due to their absorption saturation problem, we here show that simple spacer-free thin cell IR spectroscopy can provide quantitative information on the number of solvating carbonate molecules around each lithium ion. We could estimate the solvent (carbonate) CNs of lithium ions in dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propylene carbonate, and butylene carbonate over a wide range of lithium salt concentrations accurately, and they are compared with the previous results obtained with attenuated total reflection IR spectroscopy technique. We anticipate that our spacer-free thin cell approach will potentially be used to investigate the solvation dynamics, chemical exchange process, and vibrational energy transfers between solvating carbonate molecules in lithium salt electrolytes when combined with time-resolved IR spectroscopy.
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Affiliation(s)
- Chaiho Lim
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea.,Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Joo Hyun Kim
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea.,Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Yeongseok Chae
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Kyung-Koo Lee
- Department of Chemistry, Kunsan National University, Gunsan 54150, Republic of Korea
| | - Kyungwon Kwak
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea.,Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Minhaeng Cho
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Republic of Korea.,Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
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11
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Fulfer KD, Galle Kankanamge SR, Chen X, Woodard KT, Kuroda DG. Elucidating the mechanism behind the infrared spectral features and dynamics observed in the carbonyl stretch region of organic carbonates interacting with lithium ions. J Chem Phys 2021; 154:234504. [PMID: 34241245 DOI: 10.1063/5.0049742] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ultrafast infrared spectroscopy has become a very important tool for studying the structure and ultrafast dynamics in solution. In particular, it has been recently applied to investigate the molecular interactions and motions of lithium salts in organic carbonates. However, there has been a discrepancy in the molecular interpretation of the spectral features and dynamics derived from these spectroscopies. Hence, the mechanism behind spectral features appearing in the carbonyl stretching region was further investigated using linear and nonlinear spectroscopic tools and the co-solvent dilution strategy. Lithium perchlorate in a binary mixture of dimethyl carbonate (DMC) and tetrahydrofuran was used as part of the dilution strategy to identify the changes of the spectral features with the number of carbonates in the first solvation shell since both solvents have similar interaction energetics with the lithium ion. Experiments showed that more than one carbonate is always participating in the lithium ion solvation structures, even at the low concentration of DMC. Moreover, temperature-dependent study revealed that the exchange of the solvent molecules coordinating the lithium ion is not thermally accessible at room temperature. Furthermore, time-resolved IR experiments confirmed the presence of vibrationally coupled carbonyl stretches among coordinated DMC molecules and demonstrated that this process is significantly altered by limiting the number of carbonate molecules in the lithium ion solvation shell. Overall, the presented experimental findings strongly support the vibrational energy transfer as the mechanism behind the off-diagonal features appearing on the 2DIR spectra of solutions of lithium salt in organic carbonates.
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Affiliation(s)
- Kristen D Fulfer
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | | | - Xiaobing Chen
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Kaylee T Woodard
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Daniel G Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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12
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Zhang X, Chen X, Kuroda DG. Computing the frequency fluctuation dynamics of highly coupled vibrational transitions using neural networks. J Chem Phys 2021; 154:164514. [PMID: 33940799 DOI: 10.1063/5.0044911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The description of frequency fluctuations for highly coupled vibrational transitions has been a challenging problem in physical chemistry. In particular, the complexity of their vibrational Hamiltonian does not allow us to directly derive the time evolution of vibrational frequencies for these systems. In this paper, we present a new approach to this problem by exploiting the artificial neural network to describe the vibrational frequencies without relying on the deconstruction of the vibrational Hamiltonian. To this end, we first explored the use of the methodology to predict the frequency fluctuations of the amide I mode of N-methylacetamide in water. The results show good performance compared with the previous experimental and theoretical results. In the second part, the neural network approach is used to investigate the frequency fluctuations of the highly coupled carbonyl stretch modes for the organic carbonates in the solvation shell of the lithium ion. In this case, the frequency fluctuation predicted by the neural networks shows a good agreement with the experimental results, which suggests that this model can be used to describe the dynamics of the frequency in highly coupled transitions.
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Affiliation(s)
- Xiaoliu Zhang
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Xiaobing Chen
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Daniel G Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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13
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Wróbel P, Kubisiak P, Eilmes A. MeTFSI (Me = Li, Na) Solvation in Ethylene Carbonate and Fluorinated Ethylene Carbonate: A Molecular Dynamics Study. J Phys Chem B 2021; 125:1248-1258. [PMID: 33482689 DOI: 10.1021/acs.jpcb.0c10622] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Classical and ab initio molecular dynamics (MD) simulations have been performed for electrolytes based on LiTFSI and NaTFSI solutions in ethylene carbonate and its mono- and difluoro derivatives. Differences between electrolytes with Li+ or Na+ ions and the effect of fluorination on the structure and transport properties have been analyzed. The observed differences are related to the strength of Me+-carbonate binding, which is weaker for the Na+ cation and/or fluorinated solvents. Infrared spectra have been computed from ab initio MD and density functional tight binding (DFTB) MD trajectories. The changes of vibrational frequencies have been related to the local structure of the electrolyte and to interactions between salt cations and solvent molecules. The frequency shifts obtained from the AIMD simulations agree with experimental data, whereas DFTB underestimates Na+-carbonate interactions.
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Affiliation(s)
- Piotr Wróbel
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, Kraków 30-387, Poland
| | - Piotr Kubisiak
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, Kraków 30-387, Poland
| | - Andrzej Eilmes
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, Kraków 30-387, Poland
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14
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Chen X, Kuroda DG. Molecular motions of acetonitrile molecules in the solvation shell of lithium ions. J Chem Phys 2020; 153:164502. [DOI: 10.1063/5.0024486] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Xiaobing Chen
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Daniel G. Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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15
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Galle Kankanamge SR, Kuroda DG. Molecular Structure, Chemical Exchange, and Conductivity Mechanism of High Concentration LiTFSI Electrolytes. J Phys Chem B 2020; 124:1965-1977. [PMID: 32069048 PMCID: PMC7307920 DOI: 10.1021/acs.jpcb.9b10795] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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High
concentration lithium electrolytes have been found to be good
candidates for high energy density and high voltage lithium batteries.
Recent studies have shown that limiting the free solvent molecules
in the electrolytes prevents the degradation of the battery electrodes.
However, the molecular level knowledge of the structure and dynamics
of such an electrolyte system is limited, especially for electrolytes
based on typical organic carbonates. In this article, the interactions
and motions involved in lithium bis(trifluoromethanesulfonyl)imide
in carbonyl-containing solvents are investigated using linear and
time-resolved vibrational spectroscopies and computational methods.
Our results suggest that the overall structure and the speciation
of the three high concentration electrolytes are similar. However,
the cyclic carbonate-based electrolyte presents an additional interaction
as a result of dimer formation. Time-resolved studies reveal similar
and fast dynamics for the structural motions of solvent molecules
in electrolytes composed of linear molecules, while the electrolyte
made of cyclic solvent molecules shows slower structural changes as
a result of the dimer formation. Additionally, a picosecond time scale
process is observed and assigned to the coordination and decoordination
of solvent molecules from a lithium-ion solvation shell. This process
of solvent exchange is found to be directly correlated to the making
and breaking of structures between the lithium-ion and the anion and,
consequently, to the conduction mechanism. Overall, our data show
that the molecular structure of the solvent does not significantly
affect the speciation and distribution of the lithium-ion solvation
shells. However, the presence of dimerization between solvent molecules
of two neighboring lithium-ions appears to produce a microscopic ordering
that it is manifested macroscopically in properties of the electrolyte,
such as its viscosity.
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Affiliation(s)
| | - Daniel G Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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16
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Chen X, Fulfer KD, Woodard KT, Kuroda DG. Structure and Dynamics of the Lithium-Ion Solvation Shell in Ureas. J Phys Chem B 2019; 123:9889-9898. [DOI: 10.1021/acs.jpcb.9b07623] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Xiaobing Chen
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Kristen D. Fulfer
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Chemistry Program, Centre College, Danville, Kentucky 40422, United States
| | - Kaylee T. Woodard
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Daniel G. Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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