Issue 12, 2019

Fluoride-ion solvation in non-aqueous electrolyte solutions

Abstract

Understanding the factors that influence ion-solvent properties for the fluoride ion in organic solvents is key to the development of useful liquid electrolytes for fluoride-ion batteries. Using both experimental and computational methods, we examined a range of chemical and electrochemical properties for a set of organic solvents in combination with dry N,N,N-trimethylneopentylammonium fluoride (Np1F) salt. Results showed that solvent electronic structure strongly influences Np1F dissolution, and the pKa of solvent protons provides a good guide to potential F reactivity. We found a number of organic solvents capable of dissolving Np1F while providing chemically-stable F in solution and characterized three of them in detail: propionitrile (PN), 2,6-difluoropyridine (2,6-DFP), and bis(2,2,2-trifluoroethyl) ether (BTFE). Arrhenius analysis for Np1F/PN, Np1F/DFP, and Np1F/BTFE electrolytes suggests that DFP facilitates the highest F ion mobility of the three neat solvents. Electrolyte mixtures of BTFE and amide co-solvents exhibit higher ionic conductivity than the neat solvents. This improved ionic conductivity is attributed to the ability of BTFE:co-solvent mixtures to partition between Np1+ and F ion-aggregates, promoting better ion dissociation.

Graphical abstract: Fluoride-ion solvation in non-aqueous electrolyte solutions

Supplementary files

Article information

Article type
Research Article
Submitted
09 août 2019
Accepted
15 oct. 2019
First published
16 oct. 2019

Mater. Chem. Front., 2019,3, 2721-2727

Author version available

Fluoride-ion solvation in non-aqueous electrolyte solutions

V. K. Davis, S. Munoz, J. Kim, C. M. Bates, N. Momčilović, K. J. Billings, T. F. Miller, R. H. Grubbs and S. C. Jones, Mater. Chem. Front., 2019, 3, 2721 DOI: 10.1039/C9QM00512A

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