Degradation Mechanisms of Redox-Active Molecules toward Long-Cycle Aqueous Organic Flow Batteries

Aqueous organic flow battery (AOFB) is emerging as a promising technology for large-scale renewable energy storage due to its high safety, potential low cost, and environmental friendliness. However, the long-term stability of AOFB is severely limited by the properties of redox-active molecules (RAMs), which undergo degradation during operation, leading to capacity loss and performance decay. This review systematically summarizes the possible degradation mechanisms and underlying mechanisms of RAMs in AOFBs, including nucleophilic addition reactions, hydrolysis reactions, tautomerization reactions, disproportionation reactions, dimerization reactions, and crossover of molecules. The degradation mitigation strategies are then analyzed, guiding the design of next-generation, highly stable RAMs.