Electronic softening of degraded LiCoO₂ enables direct regeneration via ligand-mediated interface modulation

The direct regeneration of degraded lithium cobalt oxide (LiCoO₂, LCO) cathodes is pivotal for sustainable battery recycling, yet remains hindered by the intricate lattice defects arising from surface electronic-structure instability. Most existing regeneration strategies rely on compositional compensation while neglecting electronic-level regulation, and lack research on spontaneously formed, electrochemically unfavorable interfaces (rigid interface) that impede ion transport. Herein, we demonstrate a ligand-mediated electronic modulation strategy using a lithium-aluminum acetylacetonate complex (LAAE), where acetylacetonate (acac) functions as an electronic mediator rather than a conventional chelator. Through π→d orbital coupling with high-valence cobalt sites, acac redistributes Co-O bonding characteristics, creating an electronically compliant surface. This adsorption-induced bond weakening preferentially destabilizes defect-associated Co-O linkages, facilitating the removal of electronically inactive cobalt species and oxygen vacancy passivation, while lowering interfacial ion transport barriers. Simultaneously, lithium replenishment from Liacac-derived species together with Al³⁺ incorporation contributes to stabilizing the layered framework. The regenerated LCO (R-LCO-Al) achieves a near-ideal stoichiometry with suppressed oxygen vacancies and restored structural ordering, delivering a high specific capacity of 179.9 mAh g^-1 at 0.5 C (3.0-4.5 V) and 87.0% capacity retention after 200 cycles, rivaling commercial LCO. These findings establish electronic-structure modulation as an effective strategy for closed-loop regeneration of degraded oxide cathodes.