Leaching process for recovering valuable metals from the LiNi_1/3Co_1/3Mn_1/3O₂ cathode of lithium-ion batteries

In view of the importance of environmental protection and resource recovery, recycling of spent lithium-ion batteries (LIBs) and electrode scraps generated during manufacturing processes is quite necessary. An environmentally sound leaching process for the recovery of Li, Ni, Co, and Mn from spent LiNi_1/3Co_1/3Mn_1/3O₂-based LIBs and cathode scraps was investigated in this study. Eh-pH diagrams were used to determine suitable leaching conditions. Operating variables affecting the leaching efficiencies for Li, Ni, Co, and Mn from LiNi_1/3Co_1/3Mn_1/3O₂, such as the H₂SO₄ concentration, temperature, H₂O₂ concentration, stirring speed, and pulp density, were investigated to determine the most efficient conditions for leaching. The leaching efficiencies for Li, Ni, Co, and Mn reached 99.7% under the optimized conditions of 1M H₂SO₄, 1vol% H₂O₂, 400rpm stirring speed, 40g/L pulp density, and 60min leaching time at 40°C. The leaching kinetics of LiNi_1/3Co_1/3Mn_1/3O₂ were found to be significantly faster than those of LiCoO₂. Based on the variation in the weight fraction of the metal in the residue, the "cubic rate law" was revised as follows: θ(1-f)^1/3=(1-kt/r₀ρ), which could characterize the leaching kinetics optimally. The activation energies were determined to be 64.98, 65.16, 66.12, and 66.04kJ/mol for Li, Ni, Co, and Mn, respectively, indicating that the leaching process was controlled by the rate of surface chemical reactions. Finally, a simple process was proposed for the recovery of valuable metals from spent LiNi_1/3Co_1/3Mn_1/3O₂-based LIBs and cathode scraps.