Status and Prospects of Organic Redox Flow Batteries toward Sustainable Energy Storage

Redox flow batteries (RFBs) are regarded a promising technology for large-scale electricity energy storage to realize efficient utilization of intermittent renewable energy. Redox -active materials are the most important components in the RFB system because their physicochemical and electrochemical properties directly determine their battery performance and energy storage cost. Designable, tunable, and potentially low-cost redox-active organic compounds are promising alternatives to traditional redox-active inorganic compounds for RFB applications. Herein, the representative designs of redox-active molecules, recent development of organic RFBs (ORFBs), and advantages/disadvantages of different ORFB are reviewed. Especially the relationship between redox-active molecules’ physicochemical properties and their battery performance is discussed with an emphasis on the side reactions that cause fading of battery capacity. Finally, we provide an outlook on the development of high-performance ORFBs for practical energy storage applications.