Exploring Cell Designs for Redox Flow Batteries with Flowable Suspension-Based Electrolytes

Abstract

Integrating flowable suspension-based electrolytes (FSEs) in redox flow batteries (RFBs) may expand the materials design space and unlock new pathways to cost-competitive stationary energy storage.1 In this approach, conductive particles are suspended in electrolyte solutions, forming electronically conductive networks that shuttle charge to and from the reaction volume, potentially replacing stationary porous electrode with RFB stacks. This configuration offers several potential benefits including access to extremely high surface areas for charge-transfer reactions, plating/stripping on a mobile solid phase, and the use of insoluble (or sparingly soluble) active species.2 However, FSEs often display shear-dependent properties that impact electrochemical and fluid dynamic performance and challenge compatibility with current electrochemical flow cells which are largely designed to support low-viscosity Newtonian fluids.1,3,4 As such, there is a need to consider alternate cell designs that may be better suited for FSEs.We recently developed a continuum-based model and investigated how the performance of an RFB cell with an FSE changes as a function of material properties, cell dimensions, and operating conditions.4 In this presentation, we will use this modeling framework to explore three different cell configurations: fixed parallel plates, parallel plates with a linearly moving wall, and rotating concentric cylindrical surfaces. The distinct geometries and operational environments associated with each cell design result in different fluid flow and charge transport profiles which, in turn, alter the performance. We will compare and contrast fluid dynamic and electrochemical features of the three different configurations, with a focus on establishing operating envelopes and identifying which may best support FSEs. Ultimately, we aim to extend the design space considered for RFBs with FSEs as well as to better connect component material properties to cell engineering. Acknowledgments This work was supported by bridge funds from the Massachusetts Institute of Technology. References F. Savinell, and J. S. Wainright, The Electrochemical Society Interface 32, 61 (2023). Parant et. al., Carbon, 119, pp.10-20 (2017). C. Hoyt et. al., Chemical Engineering Science144 (2016): 288-297.M. V. Majji et. al., Journal of The Electrochemical Society, 170(5), p.050532, (2023).