Abstract:

Because of their excellent safety and long cycle life, all-vanadium redox flow batteries (VRFBs) hold promise for large-scale energy storage; however, the battery's relatively high-cost limits its commercialization. Increasing the power density of VRFBs is an efficient way to reduce the cost. Flow fields are an important factor in determining power density, and well-designed flow fields can effectively reduce the concentration polarization of VRFBs under high rate discharge, increasing the corresponding power density. Serpentine and interdigitated flow fields are the two most commonly used flow fields in VRFBs at the moment. Conclusions about their contributions to battery performance, however, are debatable. In this paper, we theoretically and experimentally investigate the effect of the specific flow rates and flow field size on the mass transfer and battery performance of VRFBs with serpentine and interdigitated flow fields. The results show that under the same specific flow rate, the electrolyte flow velocity in serpentine flow fields is much higher than in interdigitated flow fields, resulting in better battery performance at low specific flow rates for the former. Increasing the flow rates and size of the flow field can significantly improve the battery performance for both flow fields. However, because the critical flow rate of interdigitated flow fields is greater than that of serpentine flow fields, the performance improvement of the former with the increasing specific flow rates and flow field size is significantly greater than that of the latter, and the performance difference between these two flow fields will gradually decrease or even reverse. This work not only advances our understanding of the flow field structure and mass transfer process in VRFBs but also provides evidence and guidance for the engineering application of the flow fields.

Key words: all-vanadium redox flow batteries, serpentine flow field, interdigitated flow field, specific flow rates, flow field size