Process and mechanism of extracting valuable metals from spent lithium-ion batteries with a mixed organic acid

Abstract

The valuable metals recycling of spent lithium-ion batteries (LIBs) can achieve resource utilization and reduce environmental pollution. In this study, a mixed organic acid composed of acetic acid and ascorbic acid was used to extract valuable metals from the cathode material of spent ternary LIBs, and the leaching process and mechanism were studied. Based on the leaching results, the leaching efficiencies of Ni, Co, Mn and Li were 95.9 %, 95.3 %, 96.6 % and 97.6 % under optimal leaching conditions, respectively. A kinetic study revealed that the leaching processes of Ni, Co, Mn and Li all conformed to the Avrami reaction model with the apparent activation energies of 75.0, 75.3, 72.8 and 43.6 kJ/mol, respectively, which belonged to control of chemical reactions. Valuable metal ions undergo coordination reactions with carboxyl groups in mixed organic acid to form acetate salt and ascorbate during the leaching process. In a mixed organic acid system, ascorbic acid could not only reduce high-valence nickel, cobalt and manganese to soluble divalent ions, but also synergistically dissolve with acetic acid to promote metal ions into the solution.