Aluminum Impurity from Current Collectors Reactivates Degraded NCM Cathode Materials toward Superior Electrochemical Performance

The huge amount of degraded NCM (LiNi0.5Co0.2Mn0.3O2) cathode materials from spent lithium-ion batteries is arising as a serious environmental issue as well as a severe waste of metal resources, and therefore, direct recycling of them toward usable electrode materials again is environmentally and economically more attractive in contrast to present metallurgical treatments. In this work, we design a robust two-step method for direct recycling of degraded NCM materials, which uses the aluminum impurity from the attached current collector to supplement the transition metal vacancies for simultaneous elemental compensation and structural restoration. This single-element compensation strategy leads to the regeneration of high-quality NCM material with depressed cation disordering and stabilized layered structure. Moreover, the regenerated NCM material with controllable Al doping delivered an outstanding electrochemical performance; specifically, the capacity (158.6 mAh g-1), rate capability (91.6 mAh g-1 at 5 C), and cycling stability (89.6% capacity retention after 200 cycles) of the regenerated NCM material are even comparable with those of fresh materials. The as-established regeneration protocol has its chance in simplifying the industrial recycling process of degraded NCM materials.