Numerical analysis of vanadium redox flow battery design: Investigating the impact of compression and fiber structure on carbon paper electrodes

• Fiber diameter and compression optimize electrode performance. • Smaller fibers increase surface area but may limit permeability. • The compression balances porosity, permeability, & contact. • Configuration of 8-10 µm fibers enhance RFB. The performance of vanadium redox flow batteries (VRFBs) is strongly influenced by the structural properties of the electrode––particularly fiber diameter and compression. This study explores the impact of these parameters on mass transport and electrochemical performance through structural simulations and cyclic voltammetry analysis. Compression was found to increase the specific surface area, enhancing electron transfer rates ( k ), but also elevated tortuosity and reduced permeability, potentially hindering mass transport. Cyclic voltammetry results revealed that 8 µm fibers exhibited the highest electron transfer rate in the positive electrode, while 10 µm fibers performed optimally in the negative electrode. Polarization curve analysis demonstrated that a mixed configuration—8 µm fibers in the positive electrode and 10 µm fibers in the negative electrode—achieved the most effective balance between reaction kinetics and mass transport. This configuration minimized activation overpotentials and improved sulfuric acid dissociation, resulting in enhanced voltage performance. These findings underscore the critical role of electrode structure optimization in maximizing VRFB efficiency and offer valuable insights for future electrode design advancements.