Structure-driven percolation enhancement of particle-laden flow in Vanadium redox flow batteries

Vanadium redox flow batteries (VRFBs) are promising energy storage solutions with advantages such as scalability, longevity, safety, and suitability for integration with renewables. However, their performance is often limited by high cell resistance and pumping losses linked to electrolytes. The use of slurry electrodes, specifically active carbon in the carrier fluid, is often considered due to its enhanced performance, though it results in higher viscosity and pumping losses. This study introduces a unique approach to alleviate these issues using a microscale experimental model system to visualize and enhance percolation in particulate flow with patterned electrodes. Anthraquinone disulfonic acid (AQDS), an organic compound that fluoresces upon reduction, was used as an indicator to visualize redox reactions in the slurry electrode VRFB. By observing fluid flow and redox reactions, we identified key factors influencing percolation related to carbon particle concentration, flow rate, and pattern size. We found that optimizing the pattern structure of the electrodes was more effective in reducing pumping losses than merely increasing the carbon particle concentration. These findings provide insights for optimizing slurry electrodes and contribute to the development of efficient energy storage systems.