Development of a routine method for the chemical and mineralogical characterization of Li- and Mn-containing slags from the recycling of NMC-type lithium-ion batteries (LIBs)

In the BMBF-funded project PyroLith, a methodical approach for the recovery of Li from NMC type LIB via a combined pyro- and hydrometallurgical process route is being developed. For this purpose, the cooling conditions and the chemical composition of the battery slags are optimized in the pyrometallurgical process step so that the whole Li content of the melt is enriched in the artificial, Li-rich compound lithium aluminate (γ-LiAlO₂). After comminution of the slags, the γ-LiAlO₂ is separated from the largely silicate slag matrix by flotation. The lithium is then leached out by hydrometallurgical processes and recovered as Li₂CO₃.

In order to achieve the project goal, extensive chemical and mineralogical analyses of the process samples are required, which are carried out as part of a method development at BGR. Because Li cannot be directly measured by conventional wavelength- and energy-dispersive X-ray spectroscopic investigation procedures, and amorphous components are only given as a sum in X-ray diffraction analysis, the use of several complementary analytical methods for sample characterization is necessary.

In the work presented here, it is briefly outlined how a Li- and Mn-rich slag from the simplified battery slag system Al₂O₃-SiO₂-CaO-MnO-Li₂O can be fully characterized chemically and mineralogically using QXRD, SEM-MLA, EPMA, XRF and ICP-MS. Furthermore, a rapid analytical tool based on UVC radiation or alternatively on µEDXRF is presented to determine distribution, crystal size, crystal morphology and relative content of the target phase γ-LiAlO₂ in the slags within a few seconds (UVC radiation) or within 3 hours (µEDXRF).