Utilizing Pore Network Modeling for Performance Analysis of Multi-Layer Electrodes in Vanadium Redox Flow Batteries

Abstract

Vanadium redox flow batteries (VRFBs) are promising energy storage devices. The microstructure of the porous electrode affects the performance of VRFBs. Therefore, identifying optimized electrode structures is an active research area. However, designing optimal microstructures requires studying varieties of structural parameters and design cases using a modeling tool with low computational cost. In this study, a pore network modeling (PNM) framework was developed to study the effects of multi-layer electrodes on VRFB electrode performance. In contrast to previous experimental works that were focused on multi-layer structure of the same material, this study explored the effect of using different microstructures in each layer. Using an image generation algorithm, fibrous materials were generated from which pore networks were extracted. The developed PNM included a modification by adding throat nodes in the geometry to accommodate a velocity dependent mass transfer coefficient. The results showed that putting a highly permeable layer near the membrane provides an alternative preferential path for fluid to distribute and supply those regions with reactive species, resulting in 57% increase in limiting current density in contrast to the opposite order. However, selection of the desired structures must be based on a trade-off between the current/power density and pressure drop.