Here, we use a single-electrolyte flow cell configuration3, coupled with a model iron-based electrolyte, to probe the impact of electrolyte viscosity on RFB losses. Through the use of glucose as a chemically and electrochemically inert solution thickener, we investigate polarization as a function of electrolyte viscosity, electrolyte flowrate, and flow field geometry. Experimental data is combined with an one dimensional porous electrode polarization model to extract ohmic, kinetic, and mass transfer contributions to cell resistance. Of particular interest are mass transfer rates in RFBs, which are rarely quantified, thus the observed trends in mass transfer coefficient are correlated in terms of dimensionless numbers (e.g., Reynolds, Schmidt) in a traditional power-law format. This study aims to link electrolyte properties and cell performance and to provide a scalable descriptions of mass transfer in RFBs.
The authors acknowledge the financial support of the Joint Center for Energy Storage Research, which was formed under the Office of Basic Energy Sciences within the Department of Energy. We thank A. Helal and G. H. McKinley for rheological guidance and aid in viscosity measurements. We also thank M. Z. Bazant for use of milling equipment to fabricate flow fields used in this work.
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2. Dmello, R., Milshtein, J. D., Brushett, F. R. & Smith, K. C. Cost-driven materials selection criteria for redox flow battery electrolytes. J. Power Sources 330, 261–272 (2016).