Optimizing Vanadium Redox Flow Battery Performance with Embroidered Porous Electrodes and Corrugated Bipolar Plates
Authors: Xie Jiangzhou , Tian Yuheng , Sulide Suld , Skyllas-Kazacos Maria , Menictas Chris 
Published: December 2024

Vanadium Redox Flow Batteries (VFBs) occupy a critical position in the quest for sustainable energy solutions, offering an attractive option for large-scale energy storage due to their operational simplicity, longevity, and exceptional efficiency.[1] However, the broader deployment of VFBs is hindered by significant energy losses, primarily due to pressure drops across porous electrodes and suboptimal electrolyte utilization at high current densities, which limit their discharge capacity and overall energy efficiency.[2] This research introduces a comprehensive strategy that employs embroidered porous electrodes for substantial pressure drop reduction and corrugated bipolar plates to improve mass transport and electrolyte distribution, thus addressing concentration polarization and mass transport limitations that significantly impact performance at high current densities.

Embroidered porous electrodes: Through an innovative embroidery technique, the study engineered carbon electrodes with distinct patterns—diamond, parallel, and perpendicular—to optimize flow dynamics and decrease resistance. This method, reinforced by hydraulic modeling, achieved remarkable pressure drop reductions of 36%, 39%, and 12% for diamond, parallel, and perpendicular patterns, respectively, when compared to unmodified electrodes. The diamond pattern, in particular, demonstrated a notable increase in energy efficiency of 5.5%, including pumping losses, across various current densities. The hydraulic model provides further insight into the ideal channel width and spacing for these patterns, leading to pressure drop reductions of up to 73.5%, marking a significant breakthrough in electrode design. This research not only highlights the potential of embroidered porous electrodes in addressing VFBs' pressure drop challenges but also broadens the application horizon for these technologies across different energy storage systems.

Corrugated bipolar plates: The study also investigated the role of corrugated bipolar plates, manufactured via a hot-pressing technique. These plates, in comparison to flat counterparts, offer a fresh approach to refining the VRFBs' flow field. By adjusting the thickness of these corrugated plates (1.0, 1.5, and 2.0 mm), battery performances were methodically assessed across a range of current densities. The corrugation promotes electrolyte flow turbulence and distribution, effectively minimizing ohmic losses and facilitating higher ion transport rates—essential for high-current-density operations. The results demonstrate that the synergistic application of embroidered porous electrodes and corrugated bipolar plates significantly bolsters VRFB performance. Specifically, an uplift in energy efficiency from 62.3% to 72.3% and an enhancement in voltage efficiency from 64.1% to 74.5% were observed at a current density of 200 mA cm-2. Additionally, discharge capacity increased from 1.46 Wh to 1.89 Wh under these conditions, underscoring the efficacy of the design modifications in surmounting VRFBs' intrinsic high-current-density limitations.
This holistic approach, merging innovations in both electrode and bipolar plate designs, signifies a shift in VRFB development and optimization. It addresses critical challenges of pressure drop and electrolyte utilization while laying groundwork for future enhancements in flow battery technologies. By improving pressure drop and discharge capacity, this study furthers the objective of integrating renewable energy into the grid, leading the way to more sustainable and reliable energy storage solutions.

Keywords: Vanadium Redox Flow Batteries, Embroidered Porous Electrodes, Corrugated Bipolar Plate, Pressure Drop, Discharge Capacity.
[1] H. Jiang, J. Sun, L. Wei, M. Wu, W. Shyy, T. Zhao, A high power density and long cycle life vanadium redox flow battery, Energy Stor. Mater. 24 (2020) 529-540.
[2] T. Li, F. Xing, T. Liu, J. Sun, D. Shi, H. Zhang, X. Li, Cost, performance prediction and optimization of a vanadium flow battery by machine-learning, Energ. Environ. Sci. 13(11) (2020) 4353-4361.

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