Multiphysics Simulation of Multi-layered Fibrous Electrodes for the Vanadium Redox Flow Battery

Electrospinning can create customized flow-through electrodes for redox flow batteries with small fibers to enhance reactive surface area. A downside is higher pressure drop and parasitic pumping losses. Multilayered electrodes are a promising remedy, but it is not obvious what properties each layer should have to get the most benefit. In this work, a multiphysics simulation was used to explore the impact of varying the properties of each layer on the performance of a cell, including fiber size, fiber alignment, and porosity. The results showed that a 300% increase in limiting current can be obtained over commercial materials when the layer near the membrane has larger fibers with smaller fibers in each successive layer (1.8, 1.0 & 0.2 um, respectively). This arrangement had relatively lower overall efficiency once pumping power was taken into account. A compromise was obtained by placing a high porosity layer near the membrane with lower porosity in each successive layer (91%, 86%, and 81%, respectively). This case resulted in a 250% increase in limiting current, while expending only 0.1% of the output power on pumping.