Investigation of Hydrogen Reduction for Metal Recovery from End-of-Life Lithium-Ion Batteries

The growing demand for LIBs in electric-mobility applications mounts to the massive availability of discarded NMC-type batteries and calls for inevitable metal recycling. H 2 reduction of retrieved cathode powder is employed to selectively recover Li, Ni, Co, and Mn values. A systematic investigation combining characterization studies was conducted to analyze the underlying reduction mechanism. The thermodynamic and experimental analysis shows that the stable-layered NMC structure breaks to metal/oxides above 450 °C during hydrogen reduction. The effect of reduction temperature and time was studied, followed by water leaching and magnetic separation. The saturation magnetization of the magnetic fraction was increased to 55 emu/g at 710 °C, 60 min. Subsequently, 92% Li recovery in water leaching and 91% Ni, 90% Co, and 92% Mn dissolution in 2 M H 2 SO 4 (60 °C, 60 min, and S/L of 50 g/L) were obtained. Characterization studies reveal the newly formed fused phases, complex layered NMC structure decomposition, and changes in the metal valence states during hydrogen reduction. Li extraction increases with temperature until 750 °C and decreases at high temperature probably due to Li entrapment in the reduced sintered particles. Hydrogen reduction is better suited than solid-state carbothermal reduction for metal (Co, Mn, Ni, and Li) recovery from NMC-active cathode powder. The proposed H 2 reduction of NMC cathode-active material is promising and sustainable for metal recovery. Graphical Abstract