Recovery of lithium, cobalt and nickel from the spent NMC Li-ion battery by reduction roasting, selective leaching and precipitation

Abstract

Valuable elements from the NMC Li-ion battery black mass were recovered by reduction roasting and selective leaching/precipitation. Active materials were separated from the Al/Cu collector foils by thermal treatment and then subjected to reduction roasting by carbon anode in the temperature range of 600–900 °C for 2 h. The progress of the reactions was studied via XRD, TGA-DTA, and thermodynamic modeling. Ni/Co reduction was completed at T ≥ 800 °C and transformation of Li₂CO₃ to Li₂O occurred at 900 °C. Water leaching was employed to separate lithium from roasted products and about 93 % of Li was selectively extracted from the roasted product. Pure Li₂CO₃ was precipitated from the solution by CO₂ injection without purification or the addition of pH modifiers. Mn was then selectively leached from the Li-depleted powder by citric acid. The effect of citric acid concentration, temperature, and time on the leaching efficiency of Mn was studied. About 95 % Mn was removed from the powder at a citric acid concentration of 0.15 M, T = 75 °C, time = 200 min, and S/L = 20 g/L. The activation energy of the Mn dissolution was measured as 15.5 kJ/mol suggesting a diffusional controlled mechanism. A Ni-Co alloy powder was obtained as the final leaching residue. This study provides an effective and practical approach for recycling valuable metals from spent NMC Li-ion batteries.