Advancements towards optimization of metal–organic framework-based polymer electrolyte membranes for aqueous redox flow batteries

Abstract

Aqueous redox flow batteries (ARFBs) are considered a potential technology for large-scale energy storage owing to their eco-friendliness, high current density, and tuneable capacity. Polymer electrolyte membranes (PEMs) are vital components of ARFB, but they suffer from significant capacity/efficiency deterioration due to a lack of advancement in structural framing. To enhance the effectiveness of ARFBs, various membrane types have been optimized. However, the development of an efficient PEM remains a significant problem. Metal–organic frameworks (MOFs) made up of metal sites and organic linkers have gained significant scientific interest. As a result of their large surface area, adjustable pore diameters, and customized functionality, MOF-based PEMs are regarded as effective separators for ARFB. This review covers the state of the art MOF-based PEMs as ARFB separators. In recent years, significant efforts have been made to utilize the unique characteristics of MOFs as they not only improve the conductivity (attributed to their 3D channel structure) and gradient distribution in the polymer framework but also stabilize and mitigate active species cross-over by regulating the effective pore size. The aforementioned tactics can stimulate more research on energy storage technologies and provide future insight into the development and design of size-sieving separators for ARFB.