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Cycle behaviour of hydrogen bromine redox flow battery cells with bromine complexing agents

Küttinger, Michael; Brunetaud, Ruben; Włodarczyk, Jakub K.; Fischer, Peter; Tübke, Jens

Bromine complexing agents (BCA) are used to improve the safety of aqueous bromine electrolytes versus bromine outgassing in bromine electrolytes. In this work, cycling performance of hydrogen-bromine redox flow battery cells with 1-ethylpyridin-1-ium bromide ([C2Py]Br) as BCA in a bromine electrolyte with a theoretical capacity of 179.6 A h L$^{-1}$ is investigated for the first time. The BCA leads to increased ohmic overvoltages. One cause of the ohmic drop can be attributed to [C2Py]$^{+}$ cation interaction with the perfluorosulfonic acid (PFSA) membrane, which results in a drop of its conductivity. The BCA also interacts with bromine in the cell, by forming a non-aqueous fused salt second phase which exhibits a ten times lower conductivity compared to the aqueous electrolyte. A steep rise in cell voltage at the beginning of the charge curve followed by a regeneration of the cell voltage is attributed to this effect. Electrolyte crossover leads to an accumulation of [C2Py]$^{+}$ in the electrolyte solution and intensifies both adverse processes. Under this condition only 30% of the theoretical electrolyte capacity of 179.6 A h L$^{-1}$ is available under long term cycle conditions. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000131386
Veröffentlicht am 16.04.2021
DOI: 10.1016/j.jpowsour.2021.229820
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Mechanische Verfahrenstechnik und Mechanik (MVM)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2021
Sprache Englisch
Identifikator ISSN: 0378-7753, 1873-2755
KITopen-ID: 1000131386
Erschienen in Journal of Power Sources
Verlag Elsevier
Band 495
Seiten Art.-Nr.: 229820
Nachgewiesen in Scopus
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