Recovery of metals from electroactive components of spent Li-ion batteries after leaching with formic acid

Abstract

In this study, the recovery of manganese, nickel, cobalt and lithium of electroactive components from spent lithium-ion batteries is described in detail. Experiments were performed in the presence of formic acid as leachant. Temperature, time, acid concentration and solid/liquid ratio were varied. Manganese, nickel and lithium were leached in high yields (> 99 wt.%) at ~ 80 °C for 3 h using 10 mol L−1 formic acid. This acid played the dual role of leachant and reductant for nickel and manganese. However, cobalt was only half leached under these conditions. The insoluble cobalt was rapidly dissolved after adding H2O2 to the leachant. Leached manganese, cobalt and nickel, in this order, were extracted from the leachates with di-2-ethylhexylphosphoric acid (D2EHPA) (25 °C, A/O = 1 v/v) after adjusting pH of the leachate using lithium carbonate. Stripping was run using 1 mol L−1 H2SO4. Lithium (99.5 wt.%) was recovered as formate, a high-value added byproduct, by careful evaporation of the aqueous final solution, thus reducing generation of final wastes.