Modeling of vanadium redox flow battery and electrode optimization with different flow fields

The fibrous electrode is an essential component of the redox flow batteries, as the electrode structure influences the reactant/product local concentration, electrochemical reaction kinetics, and the pressure loss of the battery. A three-dimensional numerical model of vanadium redox flow battery (VRFB) was developed in this work. After model validation, simulations were conducted to understand the effects of electrode structural parameters on the battery performance. The gradient electrode design, specific surface area, porosity, and different flow fields were studied and optimized. The results show that in the large-size VRFB system, ensuring a large porosity can minimize the concentration polarization, which not only improves the battery performance, and also reduce the pressure loss. To further improve the mass transfer, fibers with larger diameter can be used, and the specific surface area of the electrode can be increased by modifying the surface of the fiber. The battery performance can be significantly improved with increasing specific surface area when the specific surface area is lower than 500,000. However, with further increase in specific surface area, the voltage of the battery remains almost constant at about 1.37 V. Its influence on interdigitated flow channel case is mainly in reducing pressure loss, and on serpentine flow channel case is directly reflected in improving battery performance.