3D modeling and simulation of an alkaline flow battery considering the tertiary current distribution on the electrodes: Anthraquinone-ferro/ferricyanide as organic electroactive species

Abstract

A 3D-mathematical model in steady-state for an alkaline organic redox flow battery with an interdigitated channel is proposed based on the Nernst-Planck and Butler-Volmer theories, as well as the tertiary current distribution model. One of the main objectives of this study is considers the role of the inlet and outlet manifolds on the AORFB performance. The simulation results show a good prediction of the experimental polarization curves at different SOCs (10%, 50% and ∼100%) using the 2,6-dihydroanthraquinone/ferrocyanide redox couple at laboratory scale cell. Specifically, at a state of charge of 10% and cell voltage of 1.2 V, the model described adequately the relationship between ion concentration and cell overpotential due to considers the resistances to mass transfer at the electrode-electrolyte interface by means of the mass transfer coefficient model. In present work, it is show that the inlet manifold (dividing type) causes an electrolyte flow maldistribution along the channels and from channel to channel, provoking local zones whit greater shear stress and pressure drop, as well as zones with high concentration, and as consequence zones with high current densities and potential drops, which could lead to a more rapid deterioration of the cell components decreasing the useful life of the AORFB or that the charge-discharge efficiency cycles decrease over time of operation. These results cannot be observed in 2D simulations using a small repeating unit or unit cell.