Recovery of metals from spent lithium-ion batteries with organic acids as leaching reagents and environmental assessment

A leaching process for the recovery of cobalt and lithium from spent lithium-ion batteries (LIB) is developed in this work. Three different organic acids, namely citric acid, malic acid and aspartic acid, are used as leaching reagents in the presence of hydrogen peroxide. The cathode active materials before and after acid leaching are characterized by X-ray diffraction and scanning electron microscopy. Recovery of cobalt and lithium is optimized by varying the leachant and H₂O₂ concentrations, the solid-to-liquid ratio, and the reaction temperature and duration. Whereas leaching with citric and malic acids recovered in excess of 90% of cobalt and lithium, leaching with aspartic acid recovered significantly less of these metals. The leaching mechanism likely begins with the dissolution of the active material (LiCoO₂) in the presence of H₂O₂ followed by chelation of Co(II) and Li with citrate, malate or aspartate. An environmental analysis of the process indicates that it may be less energy and greenhouse gas intensive to recover Co from spent LIBs than to produce virgin cobalt oxide.