A Neutral pH Aqueous Organic–Organometallic Redox Flow Battery with Extremely High Capacity Retention

We demonstrate an aqueous organic and organometallic redox flow battery utilizing reactants composed of only earth-abundant elements and operating at neutral pH. The positive electrolyte contains bis­((3-tri­methyl­ammonio)­propyl)­ferrocene dichloride, and the negative electrolyte contains bis­(3-t...

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Veröffentlicht in:ACS energy letters 2017-03, Vol.2 (3), p.639-644
Hauptverfasser: Beh, Eugene S, De Porcellinis, Diana, Gracia, Rebecca L, Xia, Kay T, Gordon, Roy G, Aziz, Michael J
Format: Artikel
Sprache:eng
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Zusammenfassung:We demonstrate an aqueous organic and organometallic redox flow battery utilizing reactants composed of only earth-abundant elements and operating at neutral pH. The positive electrolyte contains bis­((3-tri­methyl­ammonio)­propyl)­ferrocene dichloride, and the negative electrolyte contains bis­(3-tri­methyl­ammonio)­propyl viologen tetrachloride; these are separated by an anion-conducting membrane passing chloride ions. Bis­(tri­methyl­ammonio­propyl) functionalization leads to ∼2 M solubility for both reactants, suppresses higher-order chemical decomposition pathways, and reduces reactant crossover rates through the membrane. Unprecedented cycling stability was achieved with capacity retention of 99.9943%/cycle and 99.90%/day at a 1.3 M reactant concentration, increasing to 99.9989%/cycle and 99.967%/day at 0.75–1.00 M; these represent the highest capacity retention rates reported to date versus time and versus cycle number. We discuss opportunities for future performance improvement, including chemical modification of a ferrocene center and reducing the membrane resistance without unacceptable increases in reactant crossover. This approach may provide the decadal lifetimes that enable organic–organometallic redox flow batteries to be cost-effective for grid-scale electricity storage, thereby enabling massive penetration of intermittent renewable electricity.
ISSN:2380-8195
2380-8195
DOI:10.1021/acsenergylett.7b00019