Cobalt recovery from spent lithium-ion batteries by leaching in H2SO4-N2 and H2SO4-O2 systems followed by electrochemical deposition

This paper is focused on cobalt valorization from the cathode material of spent lithium-ion batteries (LIBs) by using leaching and electrochemical deposition methods. During the leaching experiments, the degrees of cathode material dissolution in H2SO4-N2 and H2SO4-O2 systems were compared. Maximal degrees of cobalt extraction were 40 % in the former and 47 % in the latter system under following experimental conditions: H2SO4 concentration of 2 mol dm-3, nitrogen/oxygen volumetric flow of 2 L min-1, solid phase concentration of 33 g L-1, and tempe-rature of 85 degrees C. The rate of cobalt extraction from the cathode material in both investigated systems was the most favorable in the first 15 min, after which there was a sudden decrease in the reaction rate. Cobalt from the leaching solution was deposited on a copper substrate by galvanostatic electrochemical deposition with a current efficiency of 84 %. The energy consumption was 5.8 kWh kg-1 of deposited Co. The cyclic voltammetry (CV) method was used to determine the potential of cobalt deposition, as well as side reactions taking place in the system. Scanning electron microscopy with energy dispersive spectrometry has shown that during the process of electrochemical deposition agglomeration of cobalt particles occurred (in the shape of cauliflower), while the metal was deposited in its elemental state, which was also confirmed by the results of X-ray diffraction analysis.