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

• Published in: The journal of physical chemistry letters 2023-08, Vol.14 (34), p.7718-7731
• Main Authors: 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
• Format: Article
• Language: English
• Subjects: Chemistry; Materials Science; Physical Insights into Energy Science; Physics; Science & Technology - Other Topics
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.3c01453

Localized high-concentration electrolytes (LHCEs) combine a diluent with a high-concentration electrolyte, offering promising properties. The ions, solvent, and diluent interact to form complex heterogeneous liquid structures, where high salt concentration clusters are embedded in the diluent. Optimizing LHCEs for desired electrolyte properties like high ionic conductivity, low viscosity, and effective solid electrolyte interphase (SEI) formation ability within the vast chemical and compositional design space requires deeper understanding and theoretical guidance. We investigated the structures and conductivities of LHCEs based on a fluorinated solvent with two different diluents at varying concentrations. 2,2,3,3-Tetrafluoro­propyl trifluoro­acetate (TFPTFA) enters the solvation cluster due to its stronger Li-ion interactions, whereas 1,1,2,2-tetrafluoro­ethyl 2,2,2-trifluoro­ethyl 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.