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A Comparison of Separators vs. Membranes in Nonaqueous Redox Flow Battery Electrolytes Containing Small Molecule Active Materials

preprint
submitted on 04.01.2021, 04:58 and posted on 06.01.2021, 13:21 by Zhiming Liang, N. Harsha Attanayake, Katharine Greco, Bertrand Neyhouse, John L. Barton, Aman Preet Kaur, William Eubanks, Fikile Brushett, James Landon, Susan Odom

The lack of suitable membranes for nonaqueous electrolytes limits cell capacity and cycle lifetime in organic redox flow cells. Using soluble, stable materials, we sought to compare the best performance that could be achieved with commercially available microporous separators and ion-selective membranes. We use organic species with proven stability to avoid deconvoluting capacity fade due to crossover and/or cell imbalance from materials degradation. We found a trade-off between lifetime and coulombic efficiency: non-selective separators achieve more stable performance but suffer from low coulombic efficiencies, while ion-selective membranes achieve high coulombic efficiencies but experience capacity loss over time. When electrolytes are pre-mixed prior to cycling, coulombic efficiency remains high, but capacity is lost due to cell imbalance, which can be recovered by electrolyte rebalancing. The results of this study highlight the potential for gains in nonaqueous cell performance that may be enabled by suitable membranes.

Funding

National Science Foundation

History

Email Address of Submitting Author

susan.odom@uky.edu

Institution

University of Kentucky

Country

United States

ORCID For Submitting Author

0000-0001-6708-5852

Declaration of Conflict of Interest

The Odom group has various patent applications related to nonaqueous redox flow batteries under consideration with the US Patent and Trademark Office.

Version Notes

This manuscript was submitted to ACS Applied Energy Materials.

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