Competitive salt precipitation/dissolution during free‐water reduction in water‐in‐salt electrolyte

R. Bouchal, Z. Li, C. Bongu, S. Le Vot, R. Berthelot, B. Rotenberg, F. Favier, S.A. Freunberger, M. Salanne, O. Fontaine, Angewandte Chemie International Edition (2020).

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Journal Article | Epub ahead of print | English
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Abstract
Water-in-salt electrolytes based on highly concentrated bis(trifluoromethyl)sulfonimide (TFSI) promise aqueous electrolytes with stabilities nearing 3 V. However, especially with an electrode approaching the cathodic (reductive) stability, cycling stability is insufficient. While stability critically relies on a solid electrolyte interphase (SEI), the mechanism behind the cathodic stability limit remains unclear. Here, we reveal two distinct reduction potentials for the chemical environments of 'free' and 'bound' water and that both contribute to SEI formation. Free-water is reduced ~1V above bound water in a hydrogen evolution reaction (HER) and responsible for SEI formation via reactive intermediates of the HER; concurrent LiTFSI precipitation/dissolution establishes a dynamic interface. The free-water population emerges, therefore, as the handle to extend the cathodic limit of aqueous electrolytes and the battery cycling stability.
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Date Published
2020-05-10
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Angewandte Chemie International Edition
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Bouchal R, Li Z, Bongu C, et al. Competitive salt precipitation/dissolution during free‐water reduction in water‐in‐salt electrolyte. Angewandte Chemie International Edition. 2020. doi:10.1002/anie.202005378
Bouchal, R., Li, Z., Bongu, C., Le Vot, S., Berthelot, R., Rotenberg, B., … Fontaine, O. (2020). Competitive salt precipitation/dissolution during free‐water reduction in water‐in‐salt electrolyte. Angewandte Chemie International Edition. https://doi.org/10.1002/anie.202005378
Bouchal, Roza, Zhujie Li, Chandra Bongu, Steven Le Vot, Romain Berthelot, Benjamin Rotenberg, Fréderic Favier, Stefan Alexander Freunberger, Mathieu Salanne, and Olivier Fontaine. “Competitive Salt Precipitation/Dissolution during Free‐water Reduction in Water‐in‐salt Electrolyte.” Angewandte Chemie International Edition, 2020. https://doi.org/10.1002/anie.202005378.
R. Bouchal et al., “Competitive salt precipitation/dissolution during free‐water reduction in water‐in‐salt electrolyte,” Angewandte Chemie International Edition, 2020.
Bouchal R, Li Z, Bongu C, Le Vot S, Berthelot R, Rotenberg B, Favier F, Freunberger SA, Salanne M, Fontaine O. 2020. Competitive salt precipitation/dissolution during free‐water reduction in water‐in‐salt electrolyte. Angewandte Chemie International Edition.
Bouchal, Roza, et al. “Competitive Salt Precipitation/Dissolution during Free‐water Reduction in Water‐in‐salt Electrolyte.” Angewandte Chemie International Edition, Wiley, 2020, doi:10.1002/anie.202005378.
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PMID: 32390281
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