Lithium-phase identification in an industrial lithium-ion-battery recycling slag : implications for the recovery of lithium

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.