Flash Joule Heating Upgraded Li Leaching of Residues from Spent LiFePO₄ Cathodes for Superior Catalytic Degradation of Pollutants

The rapid development of new energy sources has produced large quantities of battery-derived spent LiFePO4 cathodes (SLICs), whose recycling has attracted growing attention in recent years. Previous SLICs recycling approaches have focused on the recovery of Li resources, neglecting the Fe-enriched residues obtained after Li recovery. Generally, Fe-enriched residues cannot be effectively converted to active Fe species using traditional methods, thereby limiting their upgrading. This study uses the emerging flash Joule heating (FJH) technology to upgrade Fe-enriched residues, and its performance was independent of Li leaching pathways. Common Li leaching protocols were initially applied to extract Li and produce residues enriched with FeC2O4, FeO(OH), FePO4, and Fe3O4. Subsequently, ultrahigh temperature and electrical stripping were performed by FJH treatment, promoting Fe–O bond breakage within the various Fe phases and generating low-coordinated Fe0 nanoparticles, as confirmed by extended X-ray absorption fine structure analysis. The unique low-coordinated Fe0 nanoparticles present in the FJH-derived composites promoted the enhanced catalytic degradation of chloramphenicol following peroxydisulfate activation, in relation to that achieved through traditional pyrolysis-derived composites. Furthermore, the developed continuous FJH process demonstrated the potential for the large-scale recycling of Fe-enriched residues and promoted the conversion of Fe-enriched residues after Li recovery.