Laser Perforated Dual-Scale Porous Electrodes Considering the Interdigitated Flow Field for Vanadium Redox Flow Battery

Abstract

The conflict between the specific surface area and hydraulic permeability of carbon-based porous electrodes limits the further improvement of redox flow battery (RFB) system performance. Dual-scale electrode design is a feasible approach to overcome this contradiction. In this study, we prepared dual-scale electrodes by perforating graphite felts using an infrared laser. Based on the symmetry of the interdigitated flow field structure, we proposed three dual-scale structure designs with different combinations of large and small pores and tested their performance on a vanadium redox flow battery (VRFB) single cell. The results showed that the design with perforations under the center of the rib could increase the maximum power density by approximately 2.4 times compared to the original electrode. Furthermore, to investigate the effect of the large pores formed by laser perforation on the local electrolyte velocity, active species concentration, and reaction rate distribution, we proposed a pore-network model and investigated the influence of different combinations of large and small pores and different operating conditions on overall performance through numerical simulation. The results showed that the optimal combination of large and small pores is related to the flow rate and other operating conditions, and that setting large pores under the rib near the outlet channel is expected to provide more performance gains in VRFBs equipped with interdigitated flow fields under typical operating flow rates.