The energy storage and power density are decoupled for flow batteries, therefore they may be tailored to specific applications and offer promising potential for grid scale energy storage.¹ For this new technology to make an impact on our energy landscape, cost must be reduced. Some suggested design criteria for the separator to reduce capital costs requirements an area specific resistance <0.3 ohm/cm² and low parasitic crossover.²One mechanism of parasitic crossover is through diffusion within extensive water channels, a drawback to perfluorinated sulfonic acids. This research works at minimizing unwanted crossover through reduction of water channels. The approach taken is to use heteropoly acid (HPA) to crosslink a fluoroelastomer. When films are crosslinked, they are more restricted and less able to swell, thus reducing the channels for crossover to occur. The reason for using HPA it is has proven to have great conductivity with low water content.³

 We will report on transport of a verity of species in different electrolyte environments and discuss how film synthesis and processing can lead to more selective separators with better power and selectivity than Nafion.

References

[1] Perry, M. L.; Weber, A. Z., Advanced Redox-Flow Batteries: A Perspective. Journal of The Electrochemical Society 2015, 163, A5064-A5067.

[2] Darling, R.; Gallagher, K.; Xie, W.; Su, L.; Brushett, F., Transport Property Requirements for Flow Battery Separators. Journal of The Electrochemical Society 2015, 163, A5029-A5040.

[3] Horan, J. L.; Lingutla, A.; Ren, H.; Kuo, M. C.; Sachdeva, S.; Yang, Y.; Seifert, S.; Greenlee, L. F.; Yandrasits, M. A.; Hamrock, S. J.; Frey, M. H.; Herring, A. M., Fast Proton Conduction Facilitated by Minimum Water in a Series of Divinylsilyl-11-silicotungstic. Acid-co-Butyl Acrylate-co-Hexanediol Diacrylate Polymers. Journal of Physical Chemistry C 2014, 118, 135-144.