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

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 (LiFePO₄) 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.