(378z) A Low-Dimensional Electrochemical Model for Scaling and System Analysis of Redox Flow Batteries

Redox flow batteries (RFBs) are promising electrochemical devices for grid-scale energy storage due to independent scaling of power and energy, capacity retention, and simplified manufacturing, but further cost reductions are needed for widespread deployment [1]. While many research efforts have focused on identifying new redox couples or increasing power output of single flow cells, less effort has been directed toward translating data obtained in laboratory-scale cells to at-scale electrochemical stacks as this is typically reserved for those commercializing the technology [2]. However, developing these rigorous scaling relationships is a critical step to predicting stack performance based on single cell data, which, in turn, enables early-stage decision-making before significant time or capital investment. Since commercial deployment has been limited, experimental data on stack performance is typically unavailable, motivating the development of modeling frameworks to bridge the gap from single cell to stack. Unfortunately, current multi-cell models are often overly simplified to the point where critical processes are not accurately described; whereas, single cell models are typically multidimensional which challenges scalability and do not capture several stack-specific issues (e.g., non-uniform flow distributions, shunt currents, and manifold design) [3,4]. Indeed, robust low-dimensional models, which account for relevant material properties and processes, may enable the accurate prediction of system-level performance, from laboratory inputs, hence accelerating RFB development.

This presentation will describe the development and validation of a scalable, low-dimensional, physics-based model that enables the translation of single cell experiments to low-error estimates of stack performance and suitable guidelines for RFB design and operation. Experimental measurements of the physical and electrochemical properties of redox electrolytes and small-volume cell performance are combined with a one-dimensional electrochemical model to quantify relevant dimensionless relationships and scaling factors [4]. These results are then applied to a scaled stack geometry to evaluate system-level performance metrics as functions of material properties and operating parameters. Integration of additional system losses, such as shunt currents and crossover rates, yields accurate descriptions of system behavior at low levels of complexity. Finally, examination of the resulting stack performance enables generalized scaling relationships and heuristics to guide electrochemical reactor design and operation.

References

[1] A.Z. Weber, M.M. Mench, J.P. Meyers, P.N. Ross, J.T. Gostick, Q. Liu, Redox flow batteries : a review, J. Appl. Electrochem. 41 (2011) 1137–1164. doi:10.1007/s10800-011-0348-2.

[2] J. Winsberg, T. Hagemann, T. Janoschka, M.D. Hager, U.S. Schubert, Redox-Flow Batteries: From Metals to Organic Redox-Active Materials, Angew. Chemie - Int. Ed. 56 (2017) 686–711. doi:10.1002/anie.201604925.

[3] R.M. Darling, H.-S. Shiau, A.Z. Weber, M.L. Perry, The Relationship between Shunt Currents and Edge Corrosion in Flow Batteries, J. Electrochem. Soc. 164 (2017) E3081–E3091. doi:10.1149/2.0081711jes.

[4] J.D. Milshtein, K.M. Tenny, J.L. Barton, J. Drake, R.M. Darling, F.R. Brushett, Quantifying Mass Transfer Rates in Redox Flow Batteries, J. Electrochem. Soc. 164 (2017) 3265–3275. doi:10.1149/2.0201711jes.