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DOE OSTI · 3024082

The Relationship between Ionic Conductivity and Solvation Structures of Localized High-Concentration Fluorinated Electrolytes for Lithium-Ion Batteries

Hossain, Md Jamil·Wu, Qisheng·Marin Bernardez, Edelmy J.·Quilty, Calvin D.·Marschilok, Amy C.·Takeuchi, Esther S.·Bock, David C.·Takeuchi, Kenneth J.·Qi, Yue
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Abstract

Localized high concentration electrolyte (LHCE) combines a diluent with high concentration electrolyte (HCE), offering promising properties. The ions, solvent, and diluent interact to form a complex heterogenous liquid structure, where high salt concentration clusters are embedded in diluent. Optimizing LHCE for desired electrolyte properties like high ionic conductivity, low viscosity, effective solid electrolyte interphase (SEI) formability, within the vast chemical and compositional design space requires deeper understanding and theoretical guidance. For this work, we investigated the structures and conductivity of LHCEs based on a fluorinated solvent with two different diluents at varying concentrations. The 2,2,3,3-tetrafluoropropyl trifluoroacetate (TFPTFA) enters the solvation cluster due to its stronger Li-ion interactions, whereas 1,1,2,2-tetrafuoroethyl 2,2,2-trifuoroethyl ether (TFETFE) enters only at extremely high diluent concentrations. The ionic conductivity increases with decreasing diluent concentrations, with a slope change during cluster percolation. Overall, TFETFE demonstrates higher effectiveness than TFPTFA, forming higher local salt concentration clusters, and resulting in higher ionic conductivity.

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Hossain, Md Jamil, Wu, Qisheng, Marin Bernardez, Edelmy J., Quilty, Calvin D., Marschilok, Amy C., Takeuchi, Esther S., Bock, David C., Takeuchi, Kenneth J., Qi, Yue. 2023-08-22. The Relationship between Ionic Conductivity and Solvation Structures of Localized High-Concentration Fluorinated Electrolytes for Lithium-Ion Batteries. https://doi.org/10.1021/acs.jpclett.3c01453

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