Redox flow battery (RFB) is an electrochemical device that employs the reactions of two different electrolyte ions couples in the positive and negative electrodes respectively, thus achieving the reversible conversion between the chemical energy and electrical energy. It has the advantages such as long lifetime, power and capacity flexible design, and deeply charging and discharging. It has been attracting more and more attention and research during the decades.
During the charging/discharging, the positive and negative electrolytes containing activate ions are pumped circularly from the external storage reservoirs to two half-cells, in which the fluid flow though or flow by the porous electrode holes, while the electrons flow out/in from the current collectors to the porous electrode matrixes, then the electrochemical reaction occurred in the solid-liquid interface. The whole multi-physical process involves mass, momentum, charge and heat transfer, in addition to electrochemical reaction. The key parameters, such as species concentrations, fluid velocity and pressure, potential and current, temperature and over-potential, are interactive and co-determine the performance of battery.
In this study, a novel flow pattern inside the electrode, which makes the parameters distribute in the electrode much more uniform was proposed. The parameters distribution of several flow patterns, including the flow in fluid distributor and inside the electrode are calculated and analyzed based on the mathematic tool of Finite Element Method (FEM). The results show that the fluid pressure drops along the lines from inlet to outlet and the velocity varies widely in the electrode, as a consequence of the species concentrations and potential distribute non-uniformity, resulting in a higher overpotential caused, and the charge-discharge efficiency of the battery is greatly reduced. The theoretical analysis provides a optimize solution, and turn out to be a powerful tool for battery design.
Keywords: Redox Flow Battery, distribution analysis, flow pattern, optimization strategy,Finite Element Method(FEM)
The work was funded by National High Technology R&D Program of China (2012AA051201), National Natural Science Foundation of China (21176140). Vijay Ramani would like to acknowledge funding from the Hyosung S. R. Cho Endowed Professorship for partially funding his participation in this study.
* Corresponding author: XIE Xiaofeng, email@example.com
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