Study on the effects of electrode fiber and flow channel arrangements on mass transfer and electrochemical performance of vanadium redox flow batteries

Mass transfer in porous electrodes is critical for the performance of redox flow batteries, affecting both the uniform distribution of reactive species and the power consumption of the pump. In this study, a three-dimensional steady-state model for vanadium redox flow batteries (VRFBs) is established, considering the in-plane anisotropic permeability of the electrode and the side reactions due to vanadium crossover. The effect of the angle between flow channels and electrode fibers on mass transfer performance is investigated, and a method for determining the optimal angle is provided. Results show that when flow channels are arranged along the length of the battery and the angle between electrode fibers and flow channels increases from 0° to 90°, the electrode permeability in the direction of electrolyte flow under the ribs is increased. With an inlet flow rate of 1 ml s−1 and a current density of 60 mA cm−2, this angle adjustment reduces the pressure drop by approximately 7.2 %, increases the volume-averaged mass transfer coefficient (VAMC) by approximately 12.3 %, and decreases the mean volume-averaged concentration overpotential (VACO) by approximately 4.5 %. The optimal angle for maximizing VAMC is determined to be 85°. This study provides valuable guidance for optimizing electrode and flow channel structures in VRFBs.