Connecting material properties and redox flow cell cycling performance through zero-dimensional models

Figure: (Top) Graphical representation of the constitutive relationships enabled by this modeling framework (top). (Bottom) Efficiency map showing the effect of area-specific ohmic resistance (ASRΩ) and current density on voltaic efficiency for difference open-circuit voltages (OCVs).

Scientific Achievement

We derived a zero-dimensional, analytical model for describing mass balances and cell voltages in redox flow batteries (RFBs), enabling direct connections between material / electrolyte properties, cell operating conditions, and resulting performance metrics (e.g., energy efficiency, capacity fade).

Significance and Impact

While a rich design space exists for emerging RFB materials, complex tradeoffs challenge the articulation of unambiguous target criteria, as the relationships between component selection and cycling performance are nuanced and multifaceted. This model begins to fill this gap by helping to elucidate key performance descriptors and to identify favorable materials combinations for specific applications.

Research Details

  • We developed a low-dimensional framework for modeling galvanostatic cycling behavior in redox flow cells. Because the mass balances are solved analytically, hundreds of cycles can be simulated in seconds, potentially facilitating detailed parametric sweeps, system optimization, and parameter estimation from experiments.
  • We explored several representative considerations for RFB design, including upper bound estimation, redoxmer decay, and membrane/separator conductivity-selectivity tradeoffs.
  • We discussed modalities for extending this framework to incorporate kinetic losses, distributed ohmic losses, and multiple spatial domains.

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DOI: 10.1149/1945-7111/ac86aa

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