Abstract
Redox flow batteries are an emerging technology for long-duration grid energy storage, but further cost reductions are needed to accelerate adoption. Improving electrode performance within the electrochemical stack offers a pathway to reduced system cost through decreased resistance and increased power density. To date, most research efforts have focused on modifying the surface chemistry of carbon electrodes to enhance reaction kinetics, electrochemically active surface area, and wettability. Less attention has been given to electrode microstructure, which has a significant impact on reactant distribution and pressure drop within the flow cell. Here, drawing from commonly used carbon-based diffusion media (paper, felt, cloth), we systematically investigate the influence of electrode microstructure on electrochemical performance. We employ a range of techniques to characterize the microstructure, pressure drop, and electrochemically active surface area in combination with in-operando diagnostics performed in a single electrolyte flow cell using a kinetically facile redox couple dissolved in a non-aqueous electrolyte. Of the materials tested, the cloth electrode shows the best performance; the highest current density at a set overpotential accompanied by the lowest hydraulic resistance. We hypothesize that the bimodal pore size distribution and periodic, well-defined microstructure of the cloth are key to lowering mass transport resistance.
Highlights
The MIT Faculty has made this article openly available
Less well-represented in the literature, advances in reactor performance represent another pathway to cost reduction, as increased power density reduces the size of the electrochemical stack required to meet design specifications.[10]
Improving electrode performance within the electrochemical stack of an Redox flow batteries (RFBs) offers a means of reducing system costs through decreased resistance and increased power density
Summary
Electrochemical energy storage is anticipated to play a pivotal role in decarbonizing the electric sector by facilitating the reliable delivery of electricity generated from low-cost but intermittent renewable resources, enhancing the efficiency and flexibility of existing grid infrastructure, and bolstering system resilience to outages.[1] Redox flow batteries (RFBs) are a promising technology platform for low-cost, long-duration energy storage as, while more complex and less energy dense than enclosed batteries (e.g., Li-ion batteries), the system architecture enables improvements in scalability, service life, and safety.[2,3] While the all-vanadium RFB remains the current state-of-the-art system, the need for further cost reduction is driving research and development efforts into next-generation redox chemistries This includes the exploration of non-aqueous electrolytes, which offer wider windows of electrochemical stability, as well as inexpensive redox couples based on organics and metal-centered coordination complexes with properties tailorable by molecular functionalization.[4,5,6,7,8,9] less well-represented in the literature, advances in reactor performance represent another pathway to cost reduction, as increased power density reduces the size of the electrochemical stack required to meet design specifications.[10]. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
