Multiphysics Simulation of the Flow Battery Cathode: Cell Architecture and Electrode Optimization

A model of a hydrogen - bromine redox flow battery cathode with interdigitated flow channels was developed to investigate the effect of both the morphology of the fibrous electrode as well as the overall architecture of the cell. The fiber morphology was determined by the fiber diameter and porosity while the cell architecture was determined by the electrode thickness as well as the channel and rib widths. A comprehensive parametric study was performed looking at the effects these parameters had on the overall performance of the cell. A kinetic parameter was also varied to allow for different catalytic systems. This generalized the scope of the work and made it applicable for a large variety of systems. The importance of fiber morphology was found to be heavily dependent on kinetics. As expected, slow reacting systems performed better with smaller fibers and lower permeability while the opposite was true for highly kinetic systems. The width of the domain was the most important characteristic, in all cases the narrowest channel had the highest reaction rate. This was also largely true for the rib widths; in most cases the narrowest rib performed best. The effect of the electrode thickness was found to vary depending on the permeability and kinetics of the system. A non-dimensional group was proposed to represent the entire dataset and visualize the relative importance of each parameter. (C) 2016 The Electrochemical Society. All rights reserved.