Laser-perforated carbon paper electrodes for improved mass-transport in high power density vanadium redox flow batteries

In this study, we demonstrate up to 30% increase in power density of carbon paper electrodes for vanadium redox flow batteries (VRFB) by introducing perforations into the structure of electrodes. A CO sub(2) laser was used to generate holes ranging from 171 to 421 [mu]m diameter, and hole densities from 96.8 to 649.8 holes cm super(-2). Perforation of the carbon paper electrodes was observed to improve cell performance in the activation region due to thermal treatment of the area around the perforations. Results also demonstrate improved mass transport, resulting in enhanced peak power and limiting current density. However, excessive perforation of the electrode yielded a decrease in performance due to reduced available surface area. A 30% increase in peak power density (478 mW cm super(-2)) was observed for the laser perforated electrode with 234 [mu]m diameter holes and 352.8 holes cm super(-2) (1764 holes per 5 cm super(2) electrode), despite a 15% decrease in total surface area compared to the raw un-perforated electrode. Additionally, the effect of perforation on VRFB performance was studied at different flow rates (up to 120 mL min super(-1)) for the optimized electrode architecture. A maximum power density of 543 mW cm super(-2) was achieved at 120 mL min super(-1).