Converting intercalation-type cathode in spent lithium-ion batteries into conversion-type cathode

The widespread applications of lithium-ion batteries (LIBs) generate tons of spent LIBs. Therefore, recycling LIBs is of paramount importance in protecting the environment and saving the resources. Current commercialized LIBs mostly adopt layered oxides such as LiCoO₂ (LCO) or LiNi_xCo_yMn_1−x−yO₂ (NMC) as the cathode materials. Converting the intercalation-type spent oxides into conversion-type cathodes (such as metal fluorides (MFs)) offers a valid recycling strategy and provides substantially improved energy densities for LIBs. Herein, two typical Co-based cathodes, LCO and LiNi_0.6Co_0.2Mn_0.2O₂ (NMC622), in spent LIBs were successfully converted to CoF₂ and (Ni_xCo_yMn_z)F₂ cathodes by a reduction and fluorination technique. The as converted CoF₂ and (Ni_xCo_yMn_z)F₂ delivered cell energy densities of 650 and 700 Wh/kg, respectively. Advanced atomic-level electron microscopy revealed that the used LCO and NMC622 were converted to highly phase pure Co metal and Ni_0.6Co_0.2Mn_0.2 alloys in the used graphite-assisted reduction roasting, simultaneously producing the important product of Li₂CO₃ using only environment friendly solvent. Our study provided a versatile strategy to convert the intercalation-type Co-based cathode in the spent LIBs into conversion-type MFs cathodes, which offers a new avenue to recycle the spent LIBs and substantially increase the energy densities of next generation LIBs.