Local Structure and Li-ion Transport Mechanism in LiFSI/DME/BTFE Electrolyte Revealed by Molecular Dynamics Simulation

doi:10.26565/2220-637X-2025-45-01

Kateryna Dikarieva Education and Research Institute of Chemistry, V.N. Karazin Kharkiv National University, Kharkiv, Ukraine https://orcid.org/0009-0003-4805-4614
Volodymyr Koverga Department of Chemical Engineering, University of Illinois at Chicago, Chicago, USA https://orcid.org/0000-0002-6248-7438
Oleg Kalugin Education and Research Institute of Chemistry, V.N. Karazin Kharkiv National University, Kharkiv, Ukraine https://orcid.org/0000-0003-3273-9259

DOI: https://doi.org/10.26565/2220-637X-2025-45-01

Keywords: lithium-ion battery electrolytes, molecular dynamics simulation, hopping transport mechanism, ion clustering, fluorinated solvents, solvation shell structure

Abstract

Fluorinated ether-based electrolytes represent a promising avenue for improving lithium-ion battery performance and safety, yet the molecular mechanisms governing ion transport in these systems remain insufficiently understood. To elucidate the solvation behavior and ion dynamics in mixed solvents, molecular dynamics simulations of 1M (bisfluorosulfonyl)imide (LiFSI) / 1,2-dimethoxyethane (DME) / bis (2,2,2-trifluoroethyl)ether (BTFE) (1:1) system were performed. The results reveal a distinct solvation preference: Li⁺ form predominantly anion-rich aggregates (FSI₃DME₁BTFE₀, 28.9%) instead of traditional solvent-separated structures, with fluorinated BTFE completely excluded from the first coordination shell despite its equimolar presence. Diffusion analysis showed significant mobility differences – BTFE diffuses 17-18 times faster than ionic species−while van Hove correlation function demonstrate that Li⁺transport proceeds via hopping between confined regions rather than continuous diffusion. Cluster analysis reveals small weakly charged aggregates dominating the electrolyte structure, explaining the system’s efficient charge transport. These molecular insights provide design principles for optimizing fluorinated ether electrolytes with enhanced ionic conductivity.

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References

Wang, H., et al., Liquid electrolyte: The nexus of practical lithium metal batteries. Joule, 2022. 6(3): p. 588-616. https://doi.org/10.1016/j.joule.2021.12.018

Zhou, J., et al., Advanced Liquid Electrolyte Design for High‐Voltage and High‐Safety Lithium Metal Batteries. Advanced Energy Materials, 2025. 15(34): p. 2502654. https://doi.org/10.1002/aenm.202502654

Zhang, J.-G., et al., Lithium Metal Anodes with Nonaqueous Electrolytes. Chemical Reviews, 2020. 120(24): p. 13312-13348. https://doi.org/10.1021/acs.chemrev.0c00275

Tan, S., et al., Review on Low-Temperature Electrolytes for Lithium-Ion and Lithium Metal Batteries. Electrochemical Energy Reviews, 2023. 6(1): p. 35. https://doi.org/10.1007/s41918-023-00199-1

Liu, J., et al., Pathways for practical high-energy long-cycling lithium metal batteries. Nature Energy, 2019. 4(3): p. 180-186. https://doi.org/10.1038/s41560-019-0338-x

Deng, K., et al., Nonflammable organic electrolytes for high-safety lithium-ion batteries. Energy Storage Materials, 2020. 32: p. 425-447. https://doi.org/10.1016/j.ensm.2020.07.018

Yu, Z., et al., Rational solvent molecule tuning for high-performance lithium metal battery electrolytes. Nature Energy, 2022. 7(1): p. 94-106. https://doi.org/10.1038/s41560-021-00962-y

Holoubek, J., et al., Electrolyte Design Implications of Ion-Pairing in Low-Temperature Li Metal Batteries. Energy & Environmental Science, 2022. 15(12): p. 4969-4981.https://doi.org/10.1039/D1EE03422G

Zhao, Y., et al., Electrolyte engineering via ether solvent fluorination for developing stable non-aqueous lithium metal batteries. Nature Communications, 2023. 14(1): p. 299. https://doi.org/10.1038/s41467-023-35934-1

Cao, X., et al., Effects of fluorinated solvents on electrolyte solvation structures and electrode/electrolyte interphases for lithium metal batteries. Proceedings of the National Academy of Sciences, 2021. 118: p. e2020357118. https://doi.org/10.1073/pnas.2020357118

Tran, T.N., et al., Enhancing Cycling Stability of Lithium Metal Batteries by a Bifunctional Fluorinated Ether. Advanced Functional Materials, 2024. 34(42): p. 2407012. https://doi.org/10.1002/adfm.202407012

Chen, S., et al., High-Efficiency Lithium Metal Batteries with Fire-Retardant Electrolytes. Joule, 2018. 2(8): p. 1548-1558. https://doi.org/10.1016/j.joule.2018.05.002

Li, X., et al., Weakly Solvating Electrolytes for Lithium and Post‐Lithium Rechargeable Batteries: Progress and Outlook. Advanced Energy Materials, 2025. 15(25): p. 2501272. https://doi.org/10.1002/aenm.202501272

Xiang, J. and Y.-C. Lu, Ether-Based High-Voltage Lithium Metal Batteries: The Road to Commercialization. ACS Nano, 2024. 18(16): p. 10726-10737. https://doi.org/10.1021/acsnano.4c00110

He, S., et al., A self-assembly capsule-like solvation structure electrolyte for lithium metal batteries. Materials Today Energy, 2025. 48: p. 101759. https://doi.org/10.1016/j.mtener.2024.101759

Hasan, R. and D. Datta, Computational Study of Li+ Solvation Structures in Fluorinated Ether, Non-Fluorinated Ether, and Organic Carbonate-Based Electrolytes at Low and High Salt Concentrations , 2025. 4: p. 1049-1066. https://doi.org/10.1039/D5YA00154D

Li, G.-X., et al., Enhancing lithium-metal battery longevity through minimized coordinating diluent. Nature Energy, 2024. 9: p. 1-11. https://doi.org/10.1038/s41560-024-01519-5

Han, H.-B., et al., Lithium bis(fluorosulfonyl)imide (LiFSI) as conducting salt for nonaqueous liquid electrolytes for lithium-ion batteries: Physicochemical and electrochemical properties. Journal of Power Sources, 2011. 196(7): p. 3623-3632. https://doi.org/10.1016/j.jpowsour.2010.12.040

Schweigart, P., et al., On the Viability of Lithium Bis(fluorosulfonyl)imide as Electrolyte Salt for Use in Lithium‐Ion Capacitors. Batteries & Supercaps, 2023. 6(9): p. e202300226.https://doi.org/10.1002/batt.202300226

Zhang, G., et al., A bifunctional fluorinated ether co-solvent for dendrite-free and long-term lithium metal batteries. Nano Energy, 2022. 95: p. 107014. https://doi.org/10.1016/j.nanoen.2022.107014

Yu, Z., et al., Simulation Guided Molecular Design of Hydrofluoroether Solvent for High Energy Batteries. Journal of Materials Chemistry A, 2024. 12(10): p. 6294-6301.https://doi.org/10.1039/D3TA07670A

Yuan, X., et al., Design principles of fluoroether solvents for lithium metal battery electrolytes unveiled by extensive molecular simulation and machine learning. Journal of Energy Chemistry, 2025. 102: p. 52-62. https://doi.org/10.1016/j.jechem.2024.10.021

Thompson, A.P., et al., LAMMPS - a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales. Computer Physics Communications, 2022. 271: p. 108171. https://doi.org/10.1016/j.cpc.2021.108171

Yeh, I.-C. and G. Hummer, System-Size Dependence of Diffusion Coefficients and Viscosities from Molecular Dynamics Simulations with Periodic Boundary Conditions. The Journal of Physical Chemistry B, 2004. 108(40): p. 15873-15879. https://doi.org/10.1021/jp0477147

Dodda, L.S., et al., LigParGen web server: an automatic OPLS-AA parameter generator for organic ligands. Nucleic Acids Research, 2017. 45(W1): p. W331-W336. https://doi.org/10.1093/nar/gkx312

Hou, T., et al., The Solvation Structure, Transport Properties and Reduction Behavior of Carbonate-Based Electrolytes of Lithium-Ion Batteries. Chemical Science, 2021. 12(44): p. 14740-14751. https://doi.org/10.1039/D1SC04265C

Asthagiri, D.N. and T.L. Beck, MD Simulation of Water Using a Rigid Body Description Requires a Small Time Step to Ensure Equipartition. Journal of Chemical Theory and Computation, 2024. 20(1): p. 368-374. https://doi.org/10.1021/acs.jctc.3c01153

Nosé, S., A unified formulation of the constant temperature molecular dynamics methods. The Journal of Chemical Physics, 1984. 81(1): p. 511-519. https://doi.org/10.1063/1.447334

Hoover, W., Canonical Dynamics: Equilibrium Phase-Space Distributions. Phys. Rev. A: At., Mol., Opt. Phys., 1985. 31: p. 1695. https://doi.org/10.1103/PhysRevA.31.1695

Martyna, G.J., D.J. Tobias, and M.L. Klein, Constant pressure molecular dynamics algorithms. The Journal of Chemical Physics, 1994. 101(5): p. 4177-4189. https://doi.org/10.1063/1.467468

Martyna, G.J., M.L. Klein, and M. Tuckerman, Nosé–Hoover chains: The canonical ensemble via continuous dynamics. The Journal of Chemical Physics, 1992. 97(4): p. 2635-2643. https://doi.org/10.1063/1.463940

Brehm, M. and B. Kirchner, TRAVIS - A Free Analyzer and Visualizer for Monte Carlo and Molecular Dynamics Trajectories. Journal of Chemical Information and Modeling, 2011. 51(8): p. 2007-2023. https://doi.org/10.1021/ci200217w

Cohen, O., et al., SolvationAnalysis: A Python toolkit for understanding liquid solvation structure in classical molecular dynamics simulations. Journal of Open Source Software, 2023. 8: p. 5183. https://doi.org/10.21105/joss.05183

Maginn, E.J., et al., Best Practices for Computing Transport Properties 1. Self-Diffusivity and Viscosity from Equilibrium Molecular Dynamics [Article v1.0]. Living Journal of Computational Molecular Science, 2018. 1(1): p. 6324. https://doi.org/10.33011/livecoms.1.1.6324

Hansen, J.-P. and I. McDonald, Theory of Simple Liquids: With Applications to Soft Matter: Fourth Edition. Theory of Simple Liquids: With Applications to Soft Matter: Fourth Edition, 2013 , Oxford: Academic Press. 636.

Jiang, L.-L., et al., Inhibiting Solvent Co‐Intercalation in a Graphite Anode by a Localized High‐Concentration Electrolyte in Fast‐Charging Batteries. Angewandte Chemie International Edition, 2020. 60: p.1-6 https://doi.org/10.1002/anie.202009738

Li, G.X., et al., Fine‐Tuning Li‐Ion Solvation Structure by Enhanced Solvent‐Diluent Interactions for Long‐Cycling Lithium Metal Batteries. Advanced Energy Materials, 2025. 15: p. 2405680. https://doi.org/10.1002/aenm.202405680