Abstract
Due to increasing electrification and therefore demand for battery raw materials, their recovery from secondary sources like spent lithium-ion batteries is highly important. One process option is a pyrometallurgical route to enrich cobalt, nickel and copper in an alloy. In current industrial smelting processes, the contained lithium and aluminum are transferred to the slag phase and are difficult to recover. But especially the recycling of the critical metal lithium will be crucial in the future, also to meet legal requirements. Processing the slag regarding lithium recovery has different drawbacks, such as energy-intensive slow cooling for targeted phase formation and milling, as well as chemical-consuming leaching operations. In literature approaches for lithium collection in the flue dust are reported as well, but require high temperatures of up to 1800 °C. Alternatively, this study investigates the influence and benefits of an early-stage lithium separation before entering the smelting process with black mass. Therefore, shredded battery material was thermally conditioned under an inert atmosphere at 630 °C. During the thermal treatment, the organic content is removed and the contained lithium transferred to water-soluble compounds. Afterwards 55 % of lithium was selectively recovered by water leaching. Suitable slag systems for smelting lithium-depleted black mass were investigated by FactSage calculations, and experimental implementation resulted in recovery of 99 % Cu, 91 % Co and 93 % Ni in the metal phase. Thus, the competitiveness of combination of early and water-based lithium recovery and pyrometallurgical smelting operation against the lithium recovery from slag or flue dust was proven.