High Power Density Vanadium Flow Batteries with Laser-Cut Flow Field Patterns on Carbon Paper Electrodes

Abstract

A major technical issue that limits the commercialization of vanadium redox flow batteries (VRFBs) is their relatively low power density which often results in higher cost [1-2]. Recently, significant research has been focused on exploring new electrode materials, which is the key component affecting the power density of these systems. Recently, Mench and co-workers utilized carbon paper as a potential electrode material for these systems due to its reduced thickness and high active surface area (as compared to conventional carbon felt electrodes), which enables reduced resistance with improved limiting current and power density. Using carbon paper electrodes, they were able to demonstrate a peak power of 557 mW cm-2, which is significantly higher than what had previously been reported in literature [3-5].Although they provide higher power density, one drawback of carbon paper electrodes is that they have a lower porosity and reduced pore size, which can potential promote mass transport limitations. In a recent study, our group investigated the effects of macro-scale circular perforations on the power density and performance of the carbon paper electrodes to explore possible mitigation strategies for minimizing mass transport losses [6]. We observed that laser-perforation of carbon paper electrodes improved the power density and performance of the VRFB cell up to 30 % when compared to raw (non-perforated) carbon paper, despite a loss in total surface area.Motivated by the results of our previous work, in this study, we go beyond simple circular perforations and utilize laser manufacturing techniques to produce more complicated geometries and flow patterns on carbon paper electrodes to identify an optimum perforation geometry that would further minimize the transport losses and yield higher power density. Specifically, we study several common flow field patterns, varying the design and geometry of the transport channels. The effect of flow field pattern on the peak power density and limiting current is investigated with the goal of providing further understanding of the coupling between the surface area, performance and mass transport losses in VRFB electrodes.