University of Waterloo boosts flow battery 52%

University of Waterloo researchers have built a 3D-printed electrode for redox flow batteries that lifted lab performance by 52%, according to the university and the underlying paper. The team said the design was aimed at a bottleneck in flow batteries: getting liquid electrolyte to move efficiently through the electrode while keeping pumping losses down. The work was led by chemical engineering professor Maxime van der Heijden and published in the Journal of Energy Storage. The researchers tested the structures in laboratory flow cells and in a proof-of-concept vanadium redox flow battery. ### Why were Waterloo researchers redesigning the electrode in the first place? Redox flow batteries store energy in liquid electrolytes held in external tanks rather than in solid electrode materials, the University of Waterloo said. That setup makes them attractive for grid storage because energy capacity can be increased by using larger tanks, a feature that differs from lithium-ion systems. (uwaterloo.ca) Electrodes matter because they are the surfaces where the battery’s charge and discharge reactions happen. Waterloo said commercial flow-battery electrodes are typically fibrous carbon materials not specifically designed for liquid-phase electrochemistry, which can leave room to improve how reactive species reach the surface and how much energy is spent pushing liquid through the cell. Van der Heijden said that creates “opportunities to engineer electrode structures” that improve transport while reducing pumping losses. (uwaterloo.ca) ### What exactly did they print? The Waterloo team used digital light processing, or DLP, 3D printing to fabricate porous electrode structures and then heat-treated them to convert them into conductive carbon electrodes. The researchers focused on triply periodic minimal surface, or TPMS, geometries — repeating three-dimensional structures found in nature, including biological membranes, leaves and insect wings, according to the university. (uwaterloo.ca) Among the geometries studied, the “diamond” structure delivered the strongest transport performance, the university said. The paper’s title — “Enhancing Mass Transport in Redox Flow Batteries with 3D-Printed Triply Periodic Minimal Surface Electrode Structures” — reflects that focus on internal geometry rather than a new battery chemistry. ### Where does the 52% figure come from? (uwaterloo.ca) The 52% figure refers to improved performance in lab testing of the redesigned electrode, as reported by Waterloo and coverage citing the paper. The researchers first isolated mass-transport effects in flow-cell experiments and then evaluated a representative printed electrode in a proof-of-concept full-cell vanadium redox flow battery. Vanadium redox flow batteries are one of the better-known flow-battery chemistries for stationary storage. Waterloo said the printed electrodes functioned in an operating battery, which moves the work beyond a purely geometric simulation or materials-screening exercise. ### Why does the geometry matter so much in a flow battery? Mass transport is the central issue the paper targets. (uwaterloo.ca) In a flow battery, electrolyte has to reach active surfaces efficiently; if the internal structure is too tortuous or resistant, performance can be limited and pumping energy rises. Waterloo said 3D printing gave the team more control over the internal architecture than conventional manufacturing methods. That means the advance is as much about manufacturing method as battery component. By using DLP printing and heat treatment to create conductive carbon structures, the researchers showed a route for tuning flow, surface area and pressure drop together rather than accepting the geometry of off-the-shelf fibrous materials. That is an inference from the paper’s stated focus on mass transport and pumping losses. (uwaterloo.ca) ### What happens next? The Journal of Energy Storage paper is the next place to look for the test conditions, electrode geometries and full-cell setup used by van der Heijden’s team. Waterloo said the work was demonstrated in laboratory flow cells and a proof-of-concept vanadium system, which sets up the next step of comparing manufacturability, durability and scale-up against commercial electrode materials. (uwaterloo.ca)