Effect of electrolyte circulation rate in flow-through mode on the performance of vanadium redox flow battery

• Published in: Journal of power sources 2023-10, Vol.582, p.233536, Article 233536
• Main Authors: Maruthi Prasanna, M., Jayanti, Sreenivas
• Format: Article
• Language: English
• Subjects: Energy density; Energy efficiency; Flow-through mode; Pressure drop; Scale-up; Vanadium redox flow battery
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2023.233536

Large-size redox flow battery stacks require flow channels for uniform flow circulation of electrolyte over the electrode without incurring too high a pressure drop penalty. In the present work, the use of thin graphite sheets in a flow-through mode, i.e., with the electrolyte being pumped directly into the electrode is explored. In order to reduce the pressure drop when such designs are scaled to large size cells, use of relatively thick polypropylene frames to hold carbon felt electrodes is studied. Experiments have been conducted in cells of nominal electrode areas of 120 and 440 cm2 having a 0.6 mm thick graphite sheet as the bipolar plate. Pressure drop and electrochemical characterization studies show that sufficient convection velocities of electrolyte in the carbon felt, in the range of 3–5 mm s−1, are needed to obtain high round-trip energy efficiency as well as discharge energy density. This observation is supported by estimates of mass transport limited current density for the cell. Under these conditions, use of thin graphite sheets yields a weight reduction of over 75% when compared to cells with thick graphite plates while giving comparable hydrodynamic and electrochemical performance. •Novel cell architecture proposed for vanadium redox flow batteries.•New cell design features thin bipolar plates and thick electrode.•Low pressure drop and high electrochemical efficiency demonstrated in two cell sizes.•Analytical model for estimation of limiting current density proposed and validated.