Redox‐Mediated Lithium Recovery From Spent LiFePO ₄ Stabilizes Ferricyanide Catholyte for Durable Zinc‐Ferricyanide Flow Batteries

Abstract The scarcity of lithium resources and the increasing volume of spent lithium‐ion batteries (LIBs) exacerbate the imbalance between lithium supply and demand. The development of efficient recovery strategies of valuable lithium ion (Li + ) from spent LIBs and their subsequent utilization presents both significant opportunities and challenges. Here, we propose an innovative approach for Li + recovery from spent lithium iron phosphate (LiFePO 4 ) batteries (LFPs) and its subsequent utilization in alkaline zinc‐ferricyanide flow batteries (AZFFBs). Utilizing a redox‐mediated reaction, we achieve exceptional Li + recovery efficiency from spent LFPs. Furthermore, the recovered Li + in solution leads to the elevated ionic strength in the electrolyte, enhancing the concentration of [Fe(CN) 6 ] 4− to a remarkable level of 1.74 M. Utilizing the above catholyte, an AZFFB cell demonstrates the cycling life extending to 11 000 cycles with a degradation rate as low as 0.00019% per cycle and 0.09% per day at a current density of 120 mA cm −2 . This study introduces a straightforward and efficient protocol that eliminates additional intermediate processes, achieving effective Li + recovery from spent LFPs and subsequent utilization in flow batteries. The resulting AZFFB exhibits high energy density and long lifespan, positioning it as a promising candidate for large‐scale energy storage solutions.