Orientation Site-Induced Antiferromagnetic Coupling Stabilizes Reconstructed Cathode From Spent Lithium-Ion Batteries

Direct regeneration of spent layered ternary oxide cathodes offers a sustainable pathway for resource recovery and circular battery manufacturing. However, their long-term stability is fundamentally constrained by intrinsic electronic interactions. In particular, the inherent π-type hybridization between Ni 3d orbitals and O 2p orbitals facilitates detrimental Ni migration and rock-salt phase formation, ultimately leading to rapid capacity degradation. Here, we leverage the preexisting Li vacancies in spent LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) as orientation sites to induce localized lattice stress fields during regeneration. The resulting lattice perturbation modulates the spin configuration of bridging O anions, thereby triggering antiferromagnetic coupling between adjacent Ni cations and O anions. Consequently, the Ni─O orbital hybridization transitions from weak π-dominated to robust σ-dominated interactions, as evidenced by enhanced covalent character of the Ni─O bonds. This reinforced bonding framework effectively suppresses Ni migration and defect propagation during repeated lithiation/delithiation cycles. As a result, the regenerated NCM cathode exhibits significantly improved durability, retaining ∼60% of its initial capacity after 750 cycles. These findings reveal a direct correlation between the local valence bond evolution and cycling reversibility of cathode materials, offering new design principles and mechanistic insights for stabilizing regenerated cathode materials.