Less can be more: Insights on the role of electrode microstructure in redox flow batteries from 2D direct numerical simulations

TL;DR

This study uses 2D direct numerical simulations to explore how microstructural modifications in porous electrodes can enhance redox flow battery performance by improving transport and efficiency.

Contribution

It introduces a novel simulation framework and demonstrates that strategic vacancy placement in electrode microstructures can outperform disordered configurations.

Findings

Vacancies improve voltage efficiency despite reducing reactive surface.

Density gradient vacancy arrangements outperform disordered microstructures.

Simulation framework enables detailed exploration of transport phenomena.

Abstract

Understanding how to structure a porous electrode to facilitate fluid, mass, and charge transport is key to enhance the performance of electrochemical devices such as fuel cells, electrolyzers, and redox flow batteries (RFBs). Using a parallel computational framework, direct numerical simulations are carried out on idealized porous electrode microstructures for RFBs. Strategies to improve electrode design starting from a regular lattice are explored. We observe that by introducing vacancies in the ordered arrangement, it is possible to achieve higher voltage efficiency at a given current density, thanks to improved mixing of reactive species, despite reducing the total reactive surface. Careful engineering of the location of vacancies, resulting in a density gradient, outperforms disordered configurations. Our simulation framework is a new tool to explore transport phenomena in RFBs and our findings suggest new ways to design performant electrodes.