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Research Article Open access CC BY 4.0

Systematic Investigation of the Solvation Structure in THF-Based Localized High-Concentration Electrolytes

Yoonha Hwang, Yeo Jin An, Soohyun Sim, Minjeong Shin

Organics · pp. 10–10 · Published 14 Feb 2026

10.3390/org7010010

Abstract

Understanding Li+ solvation structure is critical for the rational design of high- and localized high-concentration electrolytes. Here, we present a systematic investigation of tetrahydrofuran (THF)-based electrolytes with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) using Raman spectroscopy and 7Li nuclear magnetic resonance to investigate the local solvation structures. By varying the THF:LiTFSI molar ratio, we observed a transition of Li+ solvation from solvent-separated ion pairs to contact ion pairs and aggregates, accompanied by increased structural heterogeneity and constrained local dynamics. Raman spectroscopy captures the evolution of Li+–anion coordination with increasing salt concentration, while 7Li NMR chemical shifts, line widths, and relaxation times provide complementary insight into changes in the electronic environment and symmetry of Li+ coordination. Electrolyte structure is further examined by introducing a hydrofluoroether co-solvent into a concentrated (THF)2–LiTFSI electrolyte. Raman results show that the local Li+–TFSI− coordination structure is preserved upon 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) addition, whereas NMR reveals subtle modifications of the ion-rich solvation clusters. These results provide fundamental insight into Li+ solvation and electrolyte localization, offering general design principles for advanced electrolyte systems.

Solvation Electrolyte Raman spectroscopy Chemistry Chemical physics Solvation shell Relaxation (psychology) Lithium (medication)

References (32)

  1. 1 Ren, 2019, High-concentration ether electrolytes for stable high-voltage lithium metal batteries [DOI]
  2. 2 Efaw, 2023, Localized high-concentration electrolytes get more localized through micelle-like structures [DOI]
  3. 3 Cao, 2021, Localized high-concentration electrolytes for lithium batteries [DOI]
  4. 4 Zheng, 2019, Localized high concentration electrolyte behavior near a lithium–metal anode surface [DOI]
  5. 5 Sun, 2025, Improving Low-Temperature Tolerance of a Lithium-Ion Battery by a Localized High-Concentration Electrolyte Based on the Weak Solvation Effect [DOI]
  6. 6 Hossain, 2023, The relationship between ionic conductivity and solvation structures of localized high-concentration fluorinated electrolytes for lithium-ion batteries [DOI]
  7. 7 Hall, 2024, The solvation structure of localized high concentration electrolytes [DOI]
  8. 8 Ren, 2022, Solvent–diluent interaction-mediated solvation structure of localized high-concentration electrolytes [DOI]
  9. 9 Kim, 2024, Bespoke Dual-Layered Interface Enabled by Cyclic Ether in Localized High-Concentration Electrolytes for Lithium Metal Batteries [DOI]
  10. 10 Seo, 2014, Solvate structures and spectroscopic characterization of LiTFSI electrolytes [DOI]
  11. 11 Jiang, 2021, Perspective on high-concentration electrolytes for lithium metal batteries [DOI]
  12. 12 Chen, 2023, Tunning solvation structure in non-flammable, localized high-concentration electrolytes with enhanced stability towards all aluminum substrate-based K batteries [DOI]
  13. 13 Ren, 2018, Localized high-concentration sulfone electrolytes for high-efficiency lithium-metal batteries [DOI]
  14. 14 Wang, 2024, A nitrile solvent structure induced stable solid electrolyte interphase for wide-temperature lithium-ion batteries [DOI]
  15. 15 Lin, 2021, A multifunctional dual-salt localized high-concentration electrolyte for fast dynamic high-voltage lithium battery in wide temperature range [DOI]
  16. 16 Cai, 2023, Quasi-localized high-concentration electrolytes for high-voltage lithium metal batteries [DOI]
  17. 17 Piao, 2023, A review on regulating Li+ solvation structures in carbonate electrolytes for lithium metal batteries [DOI]
  18. 18 Cui, 2024, Molecular anchoring of free solvents for high-voltage and high-safety lithium metal batteries [DOI]
  19. 19 Amine, 2020, Regulating the hidden solvation-ion-exchange in concentrated electrolytes for stable and safe lithium metal batteries [DOI]
  20. 20 Ren, 2019, Enabling high-voltage lithium-metal batteries under practical conditions [DOI]
  21. 21 Pang, 2018, Tuning the electrolyte network structure to invoke quasi-solid state sulfur conversion and suppress lithium dendrite formation in Li–S batteries [DOI]
  22. 22 Xu, 2021, Designing and demystifying the lithium metal interface toward highly reversible batteries [DOI]
  23. 23 Wang, 2022, Design and eco-efficiency analysis of sustainable extractive distillation process combining preconcentration and solvent recovery functions for separating the tetrahydrofuran/ethanol/water ternary multi-azeotropic mixture [DOI]
  24. 24 Park, 2017, High-efficiency and high-power rechargeable lithium–sulfur dioxide batteries exploiting conventional carbonate-based electrolytes [DOI]
  25. 25 Liu, 2023, Stabilized Li-S batteries with anti-solvent-tamed quasi-solid-state reaction [DOI]
  26. 26 Fawdon, 2021, Characterising lithium-ion electrolytes via operando Raman microspectroscopy [DOI]
  27. 27 Piacentini, 2025, Aprotic Electrolytes Beyond Organic Carbonates: Transport Properties of LiTFSI Solutions in S-Based Solvents [DOI]
  28. 28 Li, 2023, A concentrated electrolyte of LiTFSI and dimethyl carbonate for high-voltage Li batteries [DOI]
  29. 29 Alves, 2012, FT-Raman spectroscopic analysis of the most probable structures in aluminum chloride and tetrahydrofuran solutions [DOI]
  30. 30 Pham, 2021, Design of a LiF-rich solid electrolyte interphase layer through highly concentrated LiFSI–THF electrolyte for stable lithium metal batteries [DOI]
  31. 31 Nanda, 2018, A review of NMR methods used in the study of the structure and dynamics of ionic liquids [DOI]
  32. 32 Sanders, 2023, Quantitative operando 7Li NMR investigations of silicon anode evolution during fast charging and extended cycling [DOI]

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