Mechanochemically-aided leaching of cobalt from the cathode of spent Lithium-ion batteries

Effective mechanochemically-aided recycling of cobalt from the cathode of Lithium-ion batteries was achieved via a planetary ball mill with sulfuric acid and hydrogen peroxide system. By applying single factor experiments and response surface methodology (RSM), the optimal solution of the maximum leaching rate of cobalt was realized. The optimal conditions determined were H2SO4 concentration of 0.5 mol/L, H2O2 concentration of 2 mol/L, ball-to-powder mass ratio of 35:1, solid-to-liquid ratio of 20 g/L, reaction time of 120 min, revolution speed of 100 r/min, rotation speed of 468 r/min. Under these conditions, leaching efficiency of cobalt achieved 98.96%. Additionally, the importance of each factor was experimentally quantified, and the order of their influence was reaction time > rotation speed > revolution speed by RSM statical analysis. It was experimentally verified that the used mechanochemical-aided method was well suited for leaching of cobalt from spent LIBs. Mechanism analysis exhibits that the layered structure of the LiCoO2 crystals collapsed under the destructive action of mechanical forces, Co3+ in LiCoO2 crystals is reduced to Co2+ by H2O2. At the same time, the chemical bonds of Co(II)-O and Li-O are destroyed under the action of sulfuric acid to release Co2+ and Li+. In the process of cobalt recovery, CoC2O4 and CoC2O4 4H(2)O were obtained with oxalic acid as precipitation, and the precipitate were completely converted into Co3O4 after calcination. This process can present a highly efficient and feasible approach for the reuse of metals from the cathode of spent Li-ion batteries.