Membraneless-architectured redox flow batteries

This comprehensive review critically explores the latest advancements and innovative strategies in the development of membraneless architectures for redox flow batteries (RFBs), a promising avenue for addressing the burgeoning demands for safe, scalable and cost-effective energy storage solutions. With the increasing integration of renewable energy sources and the growing need for efficient power regulation in grids, the adaptability and inherent safety of RFBs position them as a formidable alternative to conventional batteries. The exploration into membraneless designs highlights a strategic move towards overcoming the complexity and costs associated with membrane-based systems. Particular aspects include microfluidic cells that leverage laminar flow to eliminate the need for membranes, addressing challenges associated with scale and power output. Biphasic batteries, utilizing immiscible electrolytes, offer novel approaches to enhance efficiency and mitigate cross-contamination, through the selection of suitable active materials and solvents. Furthermore, the review examines hybrid flow batteries with electrodeposited anodes, uncovering methods to counteract dendritic growth and electrical short-circuits, thus enhancing electrolyte compositions and extending electrode durability. Hydrogen-bromine RFBs are also discussed for their unique ability to utilize gas and liquid phase interactions, highlighting methods to improve operation at high current densities and enhance mass transport. The analysis identifies key challenges across membraneless architectures, such as efficiency enhancement, scalability and crossover mitigation, while proposing innovations in flow cell design, electrode materials and electrolyte engineering to advance the technology towards practical, large-scale applications.