Effect of Bromine Complexing Agents on Membrane Performance in Hydrogen Bromine Flow Batteries

Yohanes Antonius Hugo1,2, Natalia Mazur2, Wiebrand Kout2, Guido Dalessi2, Antoni Forner-Cuenca1, Zandrie Borneman1, 3 and Kitty Nijmeijer1,3,*

1Membrane Materials and Processes, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; yohanes.hugo@elestor.nl (Y.A.H.); a.forner.cuenca@tue.nl (A.F.-C.); z.borneman@tue.nl (Z.B.)
2 Elestor B.V., P.O. Box 882, 6800 AW Arnhem, The Netherlands; wiebrand.kout@elestor.nl (W.K.); guido.dalessi@elestor.nl (G.D.)
3 Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 6336, 5600 HH Eindhoven, The Netherlands

Introduction
The addition of bromine complexing agent (BCA) to bromine electrolyte is an accepted method to reduce bromine vapor pressure making bromine-based flow batteries inherently safer. It is well-known that the amine functional group of the BCAs interact with Nafionmembranes.The novelty of the current work is that it investigates how this interaction of BCA with the four different membrane chemistries impacts the membrane characteristics and performance of hydrogen bromine flowbatteries(HBFBs). The impact of BCA 13 on the system performance is determined by the membrane chemistry. Exposure of Nafion membranes to BCA leads to 60% higher cell resistance, and 55% lower cell power density at 0.5V at 50% state-of-charge(SOC). This decrease is caused by the strong interaction between the negatively charged sulfonic acid groups in the membrane and the positively charged BCA. Lower SOC, lower bromine concentration and a higher free BCA concentration is detrimental in the cell operation. The use of LC PFSA membranes in the presence of BCA ions should be avoided. while BCA in combination with grafted sulfonated polyvinylidene fluoride (SPVDF) or grafted sulfonated polyethylene (SPE) membranes promising HBFB results are obtained.

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