Microwave reduction enhanced leaching of valuable metals from spent lithium-ion batteries

Abstract The growing demand for high-energy lithium-ion batteries (LIBs) has promoted the production of LiNixCoyMnZO2 cathode, which results in many spent LIBs to resolve. A novel method that employs microwave carbothermic reduction was used to enhance the leaching of metals from layered LiNi1/3Co1/3Mn1/3O2 of spent LIBs. The thermodynamic analysis showed that LiNi1/3Co1/3Mn1/3O2 could be theoretically reduced to single metals in the presence of graphite. Then experimental results demonstrated that the transition metals can be effectively reduced under the parameters of 500 W microwave energy and 30min time. Afterward, multiscale characterizations revealed that microwave irradiation leads to the disorderly crystal structure and lattice cracks of LiNi1/3Co1/3Mn1/3O2 materials, which is more efficient to facilitate their interparticle liberation and destruction of crystal structure compared with the conventional heating process. Based on the characterization of the reduction products and their leaching performance, the mechanism for microwave carbothermic reduction was accordingly raised. Finally, the leaching experimental results show the optimal efficiencies of 97% transition metals (Co Ni, and Mn) and 99% Li were obtained under microwave carbothermic reduction, which is found more efficient in comparison to the samples without microwave treated. The whole process is found to be effective and sustainable for recovery of valuable metals from the industrial electrode of spent LIBs.