Weakening H-bonds facilitate Li+ transport in concentrated aqueous LiTFSI solutions
5 affiliations
- 1Department of Physical Chemistry II
- 2Ruhr University Bochum
- 3Sorbonne Université
- 4Laboratoire PHENIX (Physicochimie des Électrolytes et Nanosystèmes Interfaciaux
- 5Réseau sur le Stockage Électrochimique de l’Énergie (RS2E), FR CNRS
Abstract
A comprehensive understanding of the microscopic processes governing ion transport in concentrated electrolyte solutions is essential for developing efficient, water-based batteries and energy storage devices. LiTFSI has emerged as a model system for Waterin-Salt (WiS) electrolytes because it can be investigated over a wide concentration range. Here, we combine Raman and THz spectroscopy with classical MD simulations to elucidate the reorganization of the water network across concentrations ranging from 1 to 21 mol·kg-1. Isotopic substitution of H2O by D2O allows us to disentangle the distinct spectroscopic contributions of ion rattling modes and H-bond motifs in the THz frequency range. The analysis reveals two solvent-dependent modes in the region of the translational and librational water network modes, rationalized as an overall strengthening of directional H-bonds and a decrease in orientational preference. This picture is consistent with the accompanying molecular dynamics simulations, which predict a continuous shift from solvent-separated to solvent-shared to contact ion pairs, alongside a softening of water-water H-bonds and a broadening in the angular distributions within the water-water H-bond network. A thermodynamic decomposition further reveals correlations among the number of H-bonds, the observed spectroscopic nonlinearities, and the concentration-dependent conductivity. Our findings reveal a gradual, continuous reorganization of the water network as LiTFSI concentration increases: the red-shifted librational mode indicates a lower barrier for the angular part of the intermolecular potential, consistent with the simulated broadening of the angular distributions within the H-bond network. The impact on water dynamics and charge transport is discussed.
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BibTeX
@misc{nolten2026weakening,
title = {{Weakening H-bonds facilitate Li+ transport in concentrated aqueous LiTFSI solutions}},
author = {Melinda Nolten and Marinella de Giovanetti and Matthieu Wolf and Gerhard Schwaab and Benjamin Rotenberg and Martina Havenith},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008623/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008623/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Weakening H-bonds facilitate Li+ transport in concentrated aqueous LiTFSI solutions
AU - Melinda Nolten
AU - Marinella de Giovanetti
AU - Matthieu Wolf
AU - Gerhard Schwaab
AU - Benjamin Rotenberg
AU - Martina Havenith
PY - 2026
DA - 2026/09/10
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008623/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008623/v1
AB - A comprehensive understanding of the microscopic processes governing ion transport in concentrated electrolyte solutions is essential for developing efficient, water-based batteries and energy storage devices. LiTFSI has emerged as a model system for Waterin-Salt (WiS) electrolytes because it can be investigated over a wide concentration range. Here, we combine Raman and THz spectroscopy with classical MD simulations to elucidate the reorganization of the water network across concentrations ranging from 1 to 21 mol·kg-1. Isotopic substitution of H2O by D2O allows us to disentangle the distinct spectroscopic contributions of ion rattling modes and H-bond motifs in the THz frequency range. The analysis reveals two solvent-dependent modes in the region of the translational and librational water network modes, rationalized as an overall strengthening of directional H-bonds and a decrease in orientational preference. This picture is consistent with the accompanying molecular dynamics simulations, which predict a continuous shift from solvent-separated to solvent-shared to contact ion pairs, alongside a softening of water-water H-bonds and a broadening in the angular distributions within the water-water H-bond network. A thermodynamic decomposition further reveals correlations among the number of H-bonds, the observed spectroscopic nonlinearities, and the concentration-dependent conductivity. Our findings reveal a gradual, continuous reorganization of the water network as LiTFSI concentration increases: the red-shifted librational mode indicates a lower barrier for the angular part of the intermolecular potential, consistent with the simulated broadening of the angular distributions within the H-bond network. The impact on water dynamics and charge transport is discussed.
ER -