Comprehensive extraction of valuable metals from waste ternary lithium batteries via roasting and leaching: Thermodynamic and kinetic studies

Considering the existing problems in the extraction of waste ternary materials, a method of reduction roasting - sulfuric acid leaching is proposed in this paper. The waste ternary battery material is mixed with carbon powder, reduced and roasted in an argon atmosphere to destroy the original crystal lattice of the ternary material, adjust the valuable metal ions to a valence state suitable for leaching, and reduce the difficulty of leaching. Moreover, recycling waste lithium batteries were systematically studied from the thermodynamic and kinetic aspects. Thermodynamic calculations indicate that the theoretical temperature for reduction roasting is 500–650 °C, and the roasting products are composed of lithium carbonate, nickel, cobalt, nickel oxide and manganese oxide, which has been confirmed by X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy analysis. The activation energy for the reduction roasting of the cathode material was calculated as 134.7 kJ/mol by thermogravimetry–differential scanning calorimetry and Kissinger formula. The roasted electrode materials were subjected to an acid leaching process. The effects of roasting and leaching conditions on the metal extraction from waste ternary batteries were investigated based on thermodynamic calculations, and the following optimal conditions were identified: 10% carbon content, 600 °C roasting temperature, 120 min roasting time, 2 mol/L sulfuric acid concentration, 85 °C leaching temperature, 10:1 liquid-to-solid ratio and 60 min leaching time. The extraction of lithium, nickel, cobalt, and manganese reached 98.3%, 97.2%, 98.8%, 96.1%, respectively, under the optimal conditions. The kinetic analysis of the acid leaching process adopted the shrinking core model and Arrhenius formula. The activation energies of lithium, nickel, cobalt, and manganese leaching were 23.9 kJ/mol, 25.2 kJ/mol, 23.0 kJ/mol, and 27.6 kJ/mol, respectively, which indicates that acid leaching is an internal diffusion control process. This study provides an economical and efficient process route and lays a theoretical and technological foundation for the extraction of cathode materials from waste ternary batteries.