Toward Sustainable Redox-Flow Batteries: The Role of Aqueous Organic Polymeric Electrolytes

Aqueous organic polymeric electrolytes have garnered substantial interest in the development of redox flow batteries (RFBs) because of their significant potential to enhance energy storage capacity and scalability. These materials provide several advantages, including high water solubility, excellent ionic conductivity, robust chemical resistance, and low viscosity, making them highly effective in energy storage applications. This review explores five critical categories of polymeric redox-active materials, primarily focusing on π-conjugated compounds, fused-ring aromatics, viologens, stable radicals, and organometallic materials. This study also examines their electrochemical performance, compatibility, and behavior within aqueous environments. Notable strides have been made in enhancing the solubility of these redox-active materials, minimizing their crossover, boosting cyclic stability, and reducing associated costs. However, several challenges persist, particularly concerning the integration of novel redox centers and advancing mechanistic understanding to optimize polymer-based materials for RFBs. Furthermore, this study delves into recent advancements, ongoing challenges, and the anticipated evolution of polymeric materials for RFBs, emphasizing their pivotal role in enabling grid-scale renewable energy storage through sustainable materials.