The direct regeneration of spent layered ternary oxide cathodes provides a sustainable pathway for resource recovery and circular battery manufacturing. Although direct regeneration can repair lattice defects and restore electrochemical capacity to levels comparable to pristine Lithium Nickel Cobalt Manganese Oxide (NCM), regenerated cathode materials (much like pristine NCM) still suffer from severe capacity decay during cycling, which hinders their practical application.

The primary degradation mechanism lies in the migration of transition metals (TM) from their inherent octahedral sites in the TM layer to the lithium (Li) layer during cycling. This triggers a phase transition from a layered structure to spinel/rock salt phases, obstructing Li⁺ transport through 1-TM channels (tetrahedral sites sharing a face with octahedral TM ions) and compromising long-term cycling performance.

This is limited by intrinsic electronic interactions, specifically the inherent π-type hybridization between Ni 3d and O 2p orbitals, which promotes the harmful migration of Ni ions and the formation of the rock-salt phase, eventually leading to rapid capacity degradation.

Therefore, regulating Ni–O bonding characteristics at the electronic structure level to inhibit phase transition failure caused by Ni ion migration and to stabilize the lattice structure is the key bottleneck to achieving high-value regeneration of spent cathode materials.

To address these issues, Professor Xi Kai's team from the School of Chemistry at Xi'an Jiaotong University (XJTU) proposed "orientation site-induced antiferromagnetic coupling" to stabilize regenerated cathode materials.

By utilizing the abundant intrinsic lithium vacancies in spent NCM cathodes as orientation sites, Niobium (Nb) atoms are selectively introduced into Li sites during the regeneration process. Unlike traditional TM-site doping, Nb at the Li site effectively regulates the electronic spin orientation and orbital distribution of bridging O anions, triggering strong antiferromagnetic coupling between adjacent O anions and Ni cations.

The establishment of this antiferromagnetic coupling prompts a fundamental shift in Ni–O orbital hybridization—from unstable π-bond dominance to robust σ-bond dominance. The enhanced bonding network stabilizes the lattice framework and inhibits the in-plane/out-of-plane migration of Ni during cycling.

Experimental results show that the regenerated cathode material (AF-RSNCM) obtained through this strategy exhibits excellent electrochemical performance, maintaining 60 percent capacity retention after 750 cycles at 0.5 C.

The research findings, titled Orientation Site-Induced Antiferromagnetic Coupling Stabilizes Reconstructed Cathode From Spent Lithium-Ion Batteries, have been published in the internationally renowned journal Angewandte Chemie International Edition.