Combining electrochemical and imaging analyses to understand the effect of electrode microstructure and electrolyte properties on redox flow batteries

This work aims to identify key performance descriptors for porous electrodes suitable for nonaqueous redox flow batteries. A set of electrodes was evaluated using a suite of experimental, modeling, and imaging techniques to articulate structure-property relationships as a function of electrode microstructure and electrolyte properties.

Scientific Achievement

Through a combined experimental and modeling approach, we show that, of the many physical properties associated with fibrous electrodes, permeability best correlates with electrochemical performance in a flow cell.

Significance and Impact

The impact of electrode choice on cell performance can be difficult to predict a priori. This work shows permeability and mass-transfer coefficients can be used to predict performance of different porous materials as redox flow battery electrodes.

Research Details

  • Four distinct carbon electrodes are tested in a redox flow cell using TEMPO, a kinetically facile redox couple, dissolved in two different electrolytes which result in solutions with different viscosities and conductivities.
  • Three-dimensional microtomographic renderings of the different electrodes are used to extract morphological data from which permeability and tortuosity tensors can be extracted via pore network modeling and direct numerical simulation.
  • A one-dimensional electrode model is used to fit the experimental flow cell data to obtain mass-transfer coefficients in the different electrolyte environments.

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