Lithium-Phase Identification in an Industrial Lithium-Ion-Battery Recycling Slag: Implications for the Recovery of Lithium

Abstract

The recycling of lithium-ion batteries (LIBs) through extractive pyrometallurgy is widely used, but a significant drawback is the loss of lithium to the slag. To address this, lithium-bearing slag from an industrial LIB recycling plant is analyzed using wavelength dispersive X-ray fluorescence, inductively coupled plasma optical emission spectroscopy, X-ray diffraction (XRD), and thermogravimetry coupled infrared. The slag's chemical composition is complex, best described by the ternary system CaO–SiO₂–Al₂O₃, with additional major components being Na₂O, Fe₂O₃, MgO, V₂O₅, Mn₂O₃, and Cr₂O₃. The slag cone shows little chemical zonation and a relatively constant lithium content of Ø 0.82 mass%. The recycling slag shows a mineralogical composition typical of nonferrous slags (e.g., melilite, clinopyroxene, nepheline). Lithium is either bound in β-eucryptite or, to a lesser extent, in lithium metasilicate. β-eucryptite contains up to 5.51 mass% lithium stoichiometrically, which is more than typical lithium ores contain. Moreover, β-eucryptite has potential for the engineering of artificial minerals strategy as an easily implementable lithium phase. β-eucryptite forms in slags with lower overall lithium content, allowing for the use of slag modifiers that reduce the process temperature. Hence, β-eucryptite could prove as efficient and feasible option for improving lithium recovery from smelting processes.