Direct regeneration of degraded LiCoO₂ cathodes with an O^--assisted structural repairing strategy

Hydrothermal direct regeneration of spent Li-ion battery cathode materials is recognized as a straightforward recycling solution with significant economic benefits and environmental advantages. However, most existing strategies still suffer from the low restored capacity and rapid cycling decay due to the incomplete lithium replenishment and poor structure integrity. Herein, we propose a simple O^--assisted structural repairing strategy for LiCoO₂ by updating the conventional hydrothermal direct regeneration with the addition of H₂O₂ and Ti⁴⁺ doping for the subsequent annealing. The introduction of O^- promotes removal of spinel Co₃O₄ phase by oxidation and elimination of surface impurities while Ti dopant serves as the support for structural stabilization. Strikingly, the apparently enhanced surface oxygen vacancies induced through this strategy elevate Li⁺ replenishment and facilitate doping uniformity. Neutron powder diffraction also confirms the promoted ion diffusion kinetics with optimized linear pathway. Consequently, the regenerated LiCoO₂ exhibits an impressive capacity of 141.1 mAh g⁻¹ at 1.0 C with a superior 92.9 % capacity retention over 300 cycles, far outperforming commercial materials. This work provides a sustainable avenue for the recycling of spent Li-ion batteries.