Complete study of a millifluidic flow battery using iodide and ferricyanide ions: modeling, effect of the flow and kinetics

Abstract

In this work, we present a comprehensive study dealing with the modeling of the conversion process occurring in a redox flow cell. Experiments are carried out on an original millifluidic flow battery with ferrocyanide and iodide as electrolytes. A simulation model supports the experimental data. In flow, intensity recovery is limited by the mass transfer. Thanks to diffusion, at low Peclet, the conversion is complete. On the contrary, at high Peclet, the convection prevents the diffusion of species and induces a conversion drop. A quantitative agreement is found between theoretic model and experiment both on current and on power curves. The originality of our work is to take into account the kinetics of the redox reaction at the electrodes. We evidence a new regime where the current intensity is constant as a function of the Peclet number. The maximal recovered power is obtained at a given flow rate and not at very high flow rate. This work paves the road for the optimization of the conversion process and for the measurements of the thermodynamic parameters involved in the redox process such as kinetic parameters at the electrodes.