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.