Effective Upcycling of Degraded NCM Cathode Materials Assisted by Surface Engineering for High-Performance Lithium-Ion Batteries

Lithium-ion batteries (LIBs) with ternary oxide cathode materials are the prevalent energy storage devices for electric vehicles, and the huge amounts of spent LIBs pose severe challenges in terms of environmental impact and resource management. Particularly, the proper handling of degraded cathode materials is of central importance for the sustainable and closed-loop development of LIBs industry. In this context, direct regeneration of degraded ternary oxides toward reusable high-performance cathode materials is environmentally and economically favorable in contrast to present metallurgical recycling methods. In this work, a simple and effective two-step method is demonstrated to regenerate the degraded NCM 622 (LiNi_0.6Co_0.2Mn_0.2O₂) materials by elemental compensation and structural restoration. Moreover, a multi-functional LTO (Li₄Ti₅O₁₂) surface coating is simultaneously designed to guarantee rapid Li⁺ diffusion and stable surface of the regenerated product. Therefore, the regenerated LTO-coated NCM materials show excellent electrochemical performance; specifically, the initial discharge capacity (183.0 mAh g⁻¹ at 0.1 C), rate capability (90.0 mAh g⁻¹ at 10 C), and cycling stability (79.3% capacity retention after 200 cycles) are even comparable with those of fresh materials. The as-established upcycling strategy may shed light on the value-added recycling of degraded cathode materials and thereby a virtuous cycle of LIBs.