Integrating lithium recovery with the production of high-purity lithium carbonate from spent lithium-ion battery smelting slag

Abstract

The pyrometallurgical extraction of valuable metals including nickel, cobalt, and copper from spent lithium-ion batteries (LIBs) has been applied in the industrial recycling of spent LIBs for many years. In conventional pyrometallurgical methods, lithium (Li) is concentrated in smelting slag, which is often discarded as waste without recycling. Given the global scarcity of Li resources, the extraction of Li from slag has become increasingly crucial. This paper describes the development of a green integrated process to efficiently leach Li from slag and separate it from other impurity metals, particularly aluminum in the resultant leachate, for the production of high-purity lithium carbonate. A leaching efficiency of Li could reach 97.8 %, under the following conditions: slag‑sulfuric acid ratio of 1:1 (g/mL), a temperature of 90 °C, a liquid-solid ratio of 5:1 (mL/g), a stirring rate of 350 rpm, and a contact time of 2 h. The resulting leach residue was found to be marketable hemihydrate gypsum (CaSO₄∙0.5H₂O). The majority of aluminum could be removed through precipitation as potassium aluminum sulfate (KAl(SO₄)₂·12H₂O) by the addition of potassium sulfate to the leachate. Subsequently, residual aluminum along with other metals including nickel, cobalt, and manganese were removed through a series of pH adjustments. Trace elements of calcium and magnesium were also eliminated by the addition of sodium carbonate to induce carbonate precipitation. Finally, high-purity lithium carbonate was obtained through the addition of sodium carbonate solution. This hydrometallurgical process promises a significant utility in the extraction of Li from challenging spent LIBs smelting slag, offering a sustainable solution to resource recovery.