Speciation of Manganese in a Synthetic Recycling Slag Relevant for Lithium Recycling from Lithium-Ion Batteries

• Published in: Metals (Basel ) Vol. 11; no. 2; p. 188
• Main Authors: Wittkowski, Alena, Schirmer, Thomas, Qiu, Hao, Goldmann, Daniel, Fittschen, Ursula E. A.
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.02.2021
• Subjects: electron probe microanalysis (EPMA); engineered artificial minerals (EnAM); lithium; melt experiments; powder X-ray diffraction (PXRD); X-ray absorption near edge structure (XANES)
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met11020188

Lithium aluminum oxide has previously been identified to be a suitable compound to recover lithium (Li) from Li-ion battery recycling slags. Its formation is hampered in the presence of high concentrations of manganese (9 wt.% MnO2). In this study, mock-up slags of the system Li2O-CaO-SiO2-Al2O3-MgO-MnOx with up to 17 mol% MnO2-content were prepared. The manganese (Mn)-bearing phases were characterized with inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and X-ray absorption near edge structure analysis (XANES). The XRD results confirm the decrease of LiAlO2 phases from Mn-poor slags (7 mol% MnO2) to Mn-rich slags (17 mol% MnO2). The Mn-rich grains are predominantly present as idiomorphic and relatively large (>50 µm) crystals. XRD, EPMA and XANES suggest that manganese is present in the form of a spinel solid solution. The absence of light elements besides Li and O allowed to estimate the Li content in the Mn-rich grain, and to determine a generic stoichiometry of the spinel solid solution, i.e., (Li(2x)Mn2+(1−x))1+x(Al(2−z),Mn3+z)O4. The coefficients x and z were determined at several locations of the grain. It is shown that the aluminum concentration decreases, while the manganese concentration increases from the start (x: 0.27; z: 0.54) to the end (x: 0.34; z: 1.55) of the crystallization.