Engineering Lung-inspired Flow Field Geometries for Electrochemical Flow Cells with Stereolithography 3D Printing


Electrochemical flow reactors are increasingly relevant platforms in emerging sustainable energy conversion and storage technologies. As a prominent example, redox flow batteries, a well-suited technology for large energy storage if the costs can be significantly reduced, leverages electrochemical reactors as power converting units. Within the reactor, the flow field geometry determines the electrolyte pumping power required, mass transport rates, and overall cell performance. However, current designs are inspired on fuel cell technologies but have not been engineered for redox flow battery applications where liquid-phase electrochemistry is sustained. Here, we leverage stereolithography 3D printing to manufacture lung-inspired flow field geometries and compare their performance to conventional flow field designs. A versatile two-step process based on stereolithography 3D printing followed by a coating procedure to form a conductive structure is developed to manufacture lung-inspired flow field geometries. We employ a suite of fluid dynamics, electrochemical diagnostics and finite element simulations to correlate the flow field geometry with performance in symmetric flow cells. The lung-inspired structural pattern is demonstrated to homogenize the reactant distribution in the porous electrode and to improve the electrolyte accessibility to the electrode reaction area. In addition, the results reveal that these novel flow field geometries can outperform traditional interdigitated flow field designs, as these patterns exhibit a more favorable electrical and pumping power balance, achieving superior current densities at lower pressure loss. Although at its nascent stage, additive manufacturing offers a versatile design space for manufacturing engineered flow field geometries for advanced flow reactors in emerging electrochemical energy storage technologies.

Version notes

The discussion about potential and limitations of printed flow fields compared to conventional manufacturing techniques such as graphite milling has been broaden. A new figure (Figure 2) has been included in the manuscript comparing the performance of printed vs. graphite milled flow fields and performed new measurements to compare their electrical conductivity. Some additional points have been improved in the description of the numerical model such as the mesh convergence analysis and model validation (extended in the Supplementary Information).


Supplementary material

Supplementary material
Flow cell configuration, determination of the electrolyte exchange perimeter, reproducibility study of electrochemical experiments, numerical model in COMSOL Multiphysics, determination of the electrochemically active surface area, permeability and Forchheimer equation fits, comparison between graphite and 3D printed flow fields, limiting current measurement example, electrochemical impedance spectroscopy fittings.