The application of lithium-ion batteries (LIBs) in electric vehicles has attracted wide attention in recent years, especially LiFePO₄ batteries that have been extensively used in large electric buses and cars. The increased demand for LIBs has greatly stimulated lithium-ion battery production, which subsequently has led to greatly increased quantities of spent LIBs. From the perspective of environmental protection and resource recovery, the recycling of spent LIBs is of great significance. In this study, the roasting flotation technology was applied to enrich valuable metals from the mixed electrode powder of spent LiFePO₄ batteries. Roasting could thoroughly remove the organic outer layer coated on the surface of electrode-active materials, which improved the flotation enrichment efficiency of valuable metals in the mixed electrode powder of spent LiFePO₄ batteries. Under the optimum conditions of roasting at 500 °C for 1 h, the enrichment efficiency of Li and Fe reached the best. The recovery and the enrichment ratio of Li were 95.87% and 1.37, respectively, while the recovery and the enrichment ratio of Fe were 95.25% and 1.36, respectively. Roasting flotation was an efficient process to enrich valuable metals from spent LiFePO₄ batteries without wasting graphite resources.

The separation of graphites and cathode materials from spent lithium-ion batteries (LIBs) is essential to close the loop of material used in LIBs. In this study, the roasting characteristics of the spent LIB materials are carefully analyzed, and the effects of roasting on the surface morphology and elemental chemical states of electrode materials are fully investigated by thermogravimetric analysis, SEM-EDS, and XPS to explore the roasting–flotation enhancement mechanism. Then, froth flotation is utilized to separate the graphites and cathode materials from the spent LIB materials. The optimal roasting temperature is determined by thermogravimetric analysis and the SEM-EDS analysis of the spent LIB materials. The results suggest that the organic binder can be effectively removed from the spent LIB materials at the roasting temperature of 500 °C, and there is almost no loss of graphite. The XPS results indicate that, in the process of roasting, the decomposition products of the organic binder can easily react with valuable metals (Ni, Co, and Mn) to produce corresponding metal fluoride. The flotation results of the spent LIB materials after roasting at the optimal conditions indicate that graphites and cathode materials can be efficiently recovered through roasting–froth flotation. When the dosage of kerosene is 200 g/t and the dosage of methyl isobutyl carbinol (MIBC) is 150 g/t, the cathode materials grade is 91.6% with a recovery of 92.6%, while the graphite grade is 84.6% with a recovery of 82.7%. The roasting–froth flotation method lays the foundation for the subsequent metallurgical process.