Materials and Systems for Organic Redox Flow Batteries: Status and Challenges

TLDR

Redox flow batteries are scalable, flexible energy storage systems whose performance hinges on redox‑active materials; inorganic options suffer from low solubility, poor activity, and high cost, whereas organic materials offer molecular diversity, tunability, and abundance. This review surveys recent advances in organic redox‑active materials and their battery designs, and highlights critical challenges and research opportunities for practical organic flow batteries. The authors examine ROMs and associated battery architectures across both aqueous and nonaqueous electrolytes.

Abstract

Redox flow batteries (RFBs) are propitious stationary energy storage technologies with exceptional scalability and flexibility to improve the stability, efficiency, and sustainability of our power grid. The redox-active materials are the key component for RFBs with which to achieve high energy density and good cyclability. Traditional inorganic-based materials encounter critical technical and economic limitations such as low solubility, inferior electrochemical activity, and high cost. Redox-active organic materials (ROMs) are promising alternative "green" candidates to push the boundaries of energy storage because of the significant advantages of molecular diversity, structural tailorability, and natural abundance. Here, the recent development of a variety of ROMs and associated battery designs in both aqueous and nonaqueous electrolytes are reviewed. The critical challenges and potential research opportunities for developing practically relevant organic flow batteries are discussed.