A Combined Physical-Mechanical and Hydrometallurgical Approach for Recovering Valuable Metals from Spent Lithium-ion Batteries

In this work, the chemical composition of electrode materials from two samples of lithium-ion batteries (LiB) is comprehensively investigated. The material balance of the physical and mechanical processing of the LiBs mixture is determined. The developed dry process scheme made it possible to extract the following components (wt.%): 15.6 plastic (ABS), 1.89 electronic materials (PP), 59.1 black mass (three types), 6.43 plastic (PVC), 2.97 Al, 6.31 Cu and 7.1 magnetic fraction (Fe). The thermodynamics of reductive leaching of LiCoO<sub>2</sub> in the H<sub>2</sub>SO<sub>4</sub>-HCOOH system was studied. It was calculated that the Gibbs energy of the leaching reaction at 363 K is -327.4 kJ/mol, the equilibrium constant is 2.02×10<sup>44</sup>. All these factors showed the potential of using formic acid as a reducing agent instead of the commonly used hydrogen peroxide solution. It is known to be unstable, since when the solution is heated from 20 to 50<sup>0</sup> C, the decomposition of H<sub>2</sub>O<sub>2</sub> increases 20 times, and the presence of copper sulfate, which usually accompanies the decomposition of the black mass in a sulfuric acid medium, leads to the destruction of 76% of hydrogen peroxide. Therefore, from a practical point of view, it was of interest to study the kinetics of cobalt dissolution from the cathode material in the H<sub>2</sub>SO<sub>4</sub>-HCOOH system. It was shown that the Crank-Ginstling-Braunstein equation agrees satisfactorily with the experimental data, which indicates intra-diffusion limitation of dissolution. The activation energy was determined. The optimal composition and conditions of the leaching solution for dissolving cobalt, lithium and associated transition metals from the black mass were determined. The thermodynamics and kinetics of dissolution of Ag, Au and Pd from electrode materials in a bromide-bromine solution were also studied.