Improving Flow-through Electrode Performance Using Computational Design of Architected Porosity

Abstract

Electrochemical systems such as fuel cells, flow batteries, and electrochemical reactors are prevalent in industry, but few tools for their numerical design and optimization exist. Controlling fluid flow, active species distribution, and mass transport in the electrode has a dramatic impact on power and efficiency. However, this control is often limited to changing a quasi-two-dimensional flowfield and selecting bulk properties of a monolithic porous material electrode like carbon felt or paper. This can lead to non-uniform reaction rates, underutilized regions of the flow cell, and can limit the ultimate performance of the devices. To address these limitations, we propose using electrodes composed of a micro-architected variable porosity medium. As a specific example, we enable variable porosity by leveraging advances in the additive manufacture of microscale iso-truss lattices. We employ physics-based homogenization of the governing microscopic, continuum transport equations to develop a descriptive model and enable the design of this variable porosity electrode. Our tool is used to generate optimized architectures which are predicted to outperform monolithic electrodes when used in a standard flow-through configuration. We conclude by demonstrating how the optimal porosity distribution changes to retain the performance benefits as the electrode is scaled beyond benchtop-experimentsLLNL-ABS- 810799This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.