Designing a better electrode for redox flow batteries

A key challenge in developing renewable energy sources, such as wind and solar power, is that they produce power intermittently. Hence, it is crucial to develop energy storage technologies that can be deployed at the scale of the electrical grid.

Redox flow batteries (RFBs) leverage the potential difference between a set of redox couples and are a promising candidate to solve this issue. RFBs comprise of two tanks of electrolyte that are pumped through an electrochemical cell with a solid, porous electrode. Dussi and Rycroft conducted two-dimensional direct numerical simulations to understand how the electrode geometry affects the performance of RFBs.

“Typical RFB designs use commercially available materials for the electrode, such as carbon papers, which consist of woven fibers through which the electrolyte can flow. But recent experimental evidence shows that these materials result in suboptimal usage of the electrolyte,” said author Christopher Rycroft. “To use RFBs on the scale of the electrical grid, it is important that we achieve better performance.”

The researchers developed a new simulation framework to model the fluid flow of the electrolyte through the electrode structure, as well as the complex chemical reactions that occur at the electrode surface. Although they began by simulating electrodes made of regular lattices of cylinders, Dussi and Rycroft discovered that removing some cylinders in the lattice actually improved the electrode’s performance.

“Removing cylinders improves how the electrolyte mixes, which increases performance overall,” said Rycroft. “Thus, we conclude that, in some cases for electrode design, less is more.”

The findings give several insights into how to better design RFB electrodes and use 3D printing to fabricate electrodes with optimally designed geometries.

Source: “Less can be more: Insights on the role of electrode microstructure in redox flow batteries from two-dimensional direct numerical simulations,” by Simone Dussi and Chris H. Rycroft, Physics of Fluids (2022). The article can be accessed at http://doi.org/10.1063/5.0084066 .