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Effect of Additives on the Kinetics of Precipitation of VV from Catholytes in Vanadium Flow Batteries

The addition of H3PO4 has a strong stabilizing effect on vanadium flow battery (VFB) catholytes. For example, at 50°C the induction time for precipitation for a typical catholyte is enhanced ~12.5-fold by 0.1 mol dm−3 added H3PO4. At concentrations of H3PO4 less than ~0.3 M, the precipitation time i...

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Bibliographic Details
Published in:ECS transactions 2017, Vol.77 (11), p.107-115
Main Authors: Oboroceanu, Daniela, Quill, Nathan, Lenihan, Catherine, Ní Eidhin, Deirdre, Albu, Sergiu P., Lynch, Robert P., Buckley, D. Noel
Format: Article
Language:English
Online Access:Get full text
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Summary:The addition of H3PO4 has a strong stabilizing effect on vanadium flow battery (VFB) catholytes. For example, at 50°C the induction time for precipitation for a typical catholyte is enhanced ~12.5-fold by 0.1 mol dm−3 added H3PO4. At concentrations of H3PO4 less than ~0.3 M, the precipitation time increases with increasing concentration at all temperatures investigated (50-70°C). The increase is approximately exponential at the lower end of the concentration range but, as the concentration is increased, the increase in induction time is less than exponential. At higher concentrations (> ~0.3 mol dm−3), induction time begins to decrease with increasing concentration of H3PO4. Arrhenius plots for concentrations of additive in the range 0-0.25 mol dm−3 show reasonable fits to straight lines and the slopes are relatively constant (within ~±15%). Experiments at 70°C using other phosphate additives (sodium triphosphate, Na5P3O10, and sodium hexametaphosphate, (NaPO3)6) showed similar results to H3PO4.
ISSN:1938-5862
1938-6737
DOI:10.1149/07711.0107ecst