Green Upcycling Strategy for Spent Lithium-Ion Batteries: One-Step Coupling of Fluoridation Inhibition and Lattice Stabilization

The direct regeneration of spent lithium-ion batteries has attracted considerable attention due to its potential to maximize economic benefits while minimizing environmental impacts. However, fluorine-containing contaminants severely interfere with the regeneration process through chemical interactions, often resulting in the cathode fluorination. Moreover, constrained by the technical limitations inherent in the original synthesis processes of waste electrodes, the cycling stability of regenerated cathode materials struggles to meet the current technical standards. Herein, we elucidate the underlying mechanisms of F-induced degradation in spent cathode materials and develop a flash Joule heating (FJH) technique with a Ca(OH)₂ medium to achieve the coupling effect of fluorination inhibition and lattice stabilization in a single processing step. The addition of Ca(OH)₂ can effectively capture the secondary HF, mitigating its corrosion of the cathodes to form a metal fluoride. Furthermore, the high temperature during FJH treatment facilitates in situ Ca doping into the LiCoO₂ lattice, enhancing its electronic and ionic conductivity. Following hydrothermal relithiation and a brief sintering regeneration process, the regenerated Ca-doped LiCoO₂ demonstrates a high capacity of 150.2 mAh/g (0.1 C) and enhanced cycling stability from 64.3 to 91.2% compared to that without Ca doping. This work provides a mechanistically guided and industrially adaptable strategy for the efficient regeneration of fluorinated cathodes, advancing the practical implementation of sustainable battery recycling.