Serpentine flow field with changing rib width for enhancing electrolyte penetration uniformity in redox flow batteries

It has been largely agreed that the electrolyte penetration is mainly driven by the pressure gradient between two neighboring flow passages in the serpentine flow field. The present study proposes to modify the distribution of the under-the-rib hydraulic resistance for making it in concert with the pressure gradient and thereby ameliorating the distribution uniformity of the volumetric electrolyte flow penetrating into the interface between the serpentine flow field and the porous carbon electrode. Three modified serpentine flow field designs are devised based on the conventional serpentine flow field by changing the width of the ribs in three distinct manners, including serpentine flow field with the sloping channels, serpentine flow field with the partially sloping channels, and serpentine flow field with the stepwise channels. The experimental results show that by using the modified serpentine flow fields, the limiting current density of the small-scale flow cell (active area corresponding to 5 cm × 5 cm) is improved by up to 60% of that of the flow cell with the conventional serpentine flow field. The simulative results show that the impacts of the proposed designs on the electrolyte penetration uniformity is expected to be more significant in large-scale flow cells. And the effectiveness of the modified serpentine flow fields is subject to the magnitude of the under-the-rib hydraulic resistance and the applied flow rate.