A Multiscale Flow Battery Modeling Approach Using Mass Transfer Coefficients

Abstract

A novel multiscale flow battery simulation approach is presented. Therefore, the mass transfer coefficient (MTC) is extracted from the 3D‐resolved microscale simulations, transferred to the homogenized cell scale and compared to empirical formulations from literature. The models are parameterized with an organic system and experimentally validated on the microscale. It resolves the real geometry of the electrode microstructure obtained by experimental image reconstruction from microtomography. It accounts for flow, mass, and coupled charge transport using Butler–Volmer kinetics. It is suitable to study power density as a function of concentration, velocity, and discharge rate. The MTC is extracted under transfer‐limiting operating conditions. Bulk and surface concentrations of active material and the reaction rate are used. The 2D homogenized cell‐scale model considers half‐cell single species transport and reduced order reaction. The extracted MTC is implemented as a function of state of charge (SOC) and velocity, distinctive for specific initial concentration and discharge rate. It is used to calculate the reaction rate for evolving species in the electrode and is investigated in a parameter study. The approach is compared to empirical formulations of the MTC based on velocity. It can be shown that the MTC is one order of magnitude higher and depends significantly on SOC.