Selective Lithium Recovery and Integrated Preparation of High-Purity Lithium Carbonate Product from Spent Lithium-Ion Battery Smelting Slag

Abstract

The recovery of valuable metals such as nickel, cobalt, and copper from spent lithium-ion batteries (LIBs) using pyrometallurgical processes has achieved significant industrial success. In a pyrometallurgical process, lithium is typically concentrated in the smelting slag. Given the global scarcity of lithium resources, the extraction of lithium from slag has become increasingly crucial. In this study, we developed a green integrated process to efficiently leach lithium from slag and separate it from other impurity metals, particularly aluminum in the resulting leach solution, for the production of high-purity lithium carbonate. The leaching efficiency of lithium reached 97.8% under optimal leaching conditions, which included a slag-acid ratio of 1:1 (g/mL), a leaching temperature of 90 °C, a liquid-solid ratio of 5:1 (g/mL), a stirring leaching speed of 350 r/min, and a leaching time of 2 h. The leaching residue was useful material hemihydrate gypsum (CaSO4∙0.5H2O). Most of the aluminum was precipitated from the leaching solution as potassium aluminum sulfate by the addition of potassium sulfate. The residual aluminum and other metals such as nickel, cobalt, and manganese were further removed through a stepwise pH adjustment process. Trace amounts of calcium and magnesium were removed by adding sodium carbonate to generate carbonate precipitation. Finally, a high-purity lithium carbonate was precipitated from the purified solution by adding a sodium carbonate solution. The proposed hydrometallurgical process holds promising application prospects for the extraction of lithium from refractory spent LIB smelting slag.

Keywords: Spent lithium-ion battery, Pyrometallurgical smelting slag, Acid leaching, Dealumination, Stepwise precipitation