Efficient extraction of valuable metals from spent LiNi0.5Co0.2Mn0.3O2 cathode based on an acid-free leaching process

The traditional liquid acid leaching method for recycling spent lithium-ion batteries (LIBs) has serious environmental pollution and unsafe transportation. In this study, solid sodium bisulfate was applied as a leaching agent to recover lithium, cobalt, nickel and manganese from the cathode active material of spent LIBs in the presence of a reductant, hydrogen peroxide. It was found that the leaching efficiencies were approximately 93.0, 91.5, 95.5 and 96.6%, respectively, for Ni, Co, Mn and Li under the conditions of 1 mol/L NaHSO4 and 3 vol% H2O2 as reductant within 30 min at 70 °C and a pulp density of 20 g/L. Kinetic data for the dissolution of valuable metals in the temperature range 40–70 °C showed the kinetic model governed by the Avrami equation. The apparent activation energies for leaching of Ni, Co, Mn and Li were determined as 43.8, 44.2, 42.2 and 27.5 kJ/mol, respectively, indicating that the leaching process was controlled by a surface chemical reaction. This process can be a convenient alternative method for recovering valuable metals from spent LiNi0.5Co0.2Mn0.3O2.