Stress‐Mediated Lattice Reconstruction Regenerates Spent LiFePO 4 Cathodes

ABSTRACT The surging deployment of electric vehicles and energy storage systems is rapidly accelerating the accumulation of spent lithium‐ion batteries (LIBs), underscoring the urgency of efficient and sustainable regeneration technologies. Although LiFePO 4 (LFP) dominates the commercial iron‐based cathode market, its long‐term operation is plagued by lithium (Li) loss, FePO 4 formation, and the accumulation of Li‐Fe anti‐site defects, which collectively block the [010] diffusion channels and severely impair electrochemical reversibility. Here, we demonstrate that the performance decay of LFP originates fundamentally from a stress‐induced structural degradation process rather than simple compositional imbalance. Guided by this mechanistic insight, we develop a stress‐regulated electrochemical regeneration strategy in which an applied electric field simultaneously drives Fe 3+ reduction and targeted Li + reinsertion into the depleted lattice. This self‐limiting repair process eliminates Li‐Fe anti‐site defects (from 3.24% to 1.05%), releases accumulated lattice micro‐strain, and reconstructs a relaxed, fully accessible Li + transport framework. Subsequent magnesium and aluminum co‐doping introduces uniform compressive prestress, enabling controlled redistribution of internal lattice stress and imparting long‐range structural robustness. The regenerated LFP exhibits 94% capacity retention after 500 cycles at 1C rate, together with markedly improved structural reversibility. Life‐cycle assessment confirms both economic and environmental benefits.