H ⁺ /OH ⁻ Switchable Coordination Chemistry Enables Sustainable and Selective Critical Metal Recovery from Spent Li‐Ion Batteries

Abstract Sustainable end‐of‐life management of lithium‐ion batteries (LIBs) is essential for minimizing environmental impact and enhancing supply chain resilience. Here, we present a novel H + /OH − switchable reversible coordination chemistry mechanism that utilizes a cost‐effective, recyclable K 4 Fe(CN) 6 aqueous solution for highly efficient and selective recovery of critical metals from various spent LIB cathodes. Under H + ‐rich acidic conditions, the LiCoO 2 (LCO) cathode demonstrates a high Li leaching efficiency of 96.57%, while cobalt selectively reacts with K 4 Fe(CN) 6 to precipitate as K 0.5 H 1.5 CoFe(CN) 6 ·H 2 O. Subsequent OH − ‐rich base treatment facilitates the stepwise recovery of cobalt from K 0.5 H 1.5 CoFe(CN) 6 ·H 2 O to form CoOOH, achieving a 95.18% recovery efficiency and K 4 Fe(CN) 6 regeneration. In situ powder X‐ray diffraction and time‐dependent Raman spectroscopy reveal the dynamic crystal structural evolution and reversible coordination chemistry between Co─O bonding in LiCoO 2 /CoOOH and Co─N bonding in K 0.5 H 1.5 CoFe(CN) 6 ·H 2 O, driven by the H + /OH − pair in the K 4 Fe(CN) 6 solution. This strategy is applicable for recovering critical metals from a wide range of LIBs cathodes (e.g., NCMs, LFP), offering significant techno‐economic and environmental benefits, and lays the foundation for sustainable critical metals recycling from urban minerals beyond spent LIBs.