InterPore2026

Rethinking Electrode Choice: Matching Porous Microstructures to Electrolyte Properties in Redox Flow Batteries

21 May 2026, 14:05

15m

Oral Presentation (MS17) Electrochemical Processes in Porous Media MS17

Speaker

Maxime van der Heijden

Description

Porous electrodes are performance- and cost-defining components of redox flow batteries (RFBs), governing electrolyte transport, accessible surface area for electrochemical reactions, and mass, charge, and heat transport within the cell [1]. Yet, the carbon fiber electrodes most commonly used today were originally developed for fuel cells and are not tailored to the diverse kinetic and transport requirements of liquid-phase redox chemistries. As a result, electrode-electrolyte mismatches, arising from trade-offs among conductivity, reaction kinetics, surface area, thickness, and pore size distribution, can significantly limit RFB performance.
Our prior computational work underscored this challenge by demonstrating that optimal electrode architectures are highly electrolyte-specific. Using an in-house genetic algorithm coupled to a pore network model, we showed that different redox chemistries (VO²⁺/VO₂⁺ and TEMPO/TEMPO⁺) converge toward distinct microstructural optima [2]. For example, sluggish kinetic systems such as all-vanadium chemistries benefit from high surface area, whereas electrolytes with low ionic conductivity require high through-plane permeability. These insights motivated a systematic experimental investigation into how commercial electrodes perform across different chemistries.
In this study, which will be the main topic of this presentation, we evaluated three widely used porous electrodes, carbon cloth, paper, and felt, across three electrolyte systems: all-vanadium, all-iron, and an aqueous organic chemistry. Through combined half-cell and full-cell testing, we found that each electrolyte exhibits a unique optimal electrode configuration, and that, in several cases, asymmetric electrode selection between the two half-cells yields superior performance. These results highlight the strong coupling between reaction kinetics, ionic and electronic transport, and electrode architecture, demonstrating how pore-scale structure governs electrolyte-dependent transport regimes. Importantly, they show that even within the constraints of commercially available materials, substantial performance gains can be achieved by matching electrode microstructure to the electrolyte’s physicochemical properties.
Building on these insights, we explore additive manufacturing as a route to move beyond traditional fibrous electrodes [3]. Triply periodic minimal surface (TPMS) architectures offer deterministic, multiscale control over porosity, tortuosity, and surface area, enabling the design of electrode structures tailored to specific electrolyte chemistries and operating conditions. This work demonstrates the potential of additive manufacturing to fabricate customized porous electrodes with enhanced electrochemical performance and reduced hydraulic resistance, paving the way for purpose-built RFB materials.

Acknowledgments
The authors gratefully acknowledge funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Discovery grant program (RGPIN-2025-04132).