Formation of critical compounds in recycling slags - a study of melt chemistry with MD simulation and solid products in a micropraeparative approach

The increasing complexity of products and the components and composites used in them from the high-tech sector means that a large number of elements with different chemical and physical properties are now being used. Conventional methods of dismantling and mechanical processing of the sometimes microscopically small components are no longer sufficient to ensure the recovery of all valuable materials, which is particularly critical for economically strategic raw materials in low concentrations. Pyrometallurgical processes are therefore used, but some of the valuable carriers are expelled into the slag and lost. The aim of the DFG priority program “Tailor-made artificial minerals (EnAM) - a geometallurgical tool for recycling critical elements from residual material streams” at Clausthal University of Technology, in which this project is embedded, is to recover the valuable carriers from the slags, which are often contained in low concentrations.

In our project “Formation of critical compounds in recycling slags - a study of the chemistry of the melt with MD simulation and the solid products in a micropraeparative approach”, together with Dr. Thomas Schirmer (Institute of Repository Research) and Professor Ursula Fittschen (Institute of Inorganic and Analytical Chemistry), the behavior of the slags formed during the recycling of e.g. electronic products and batteries is to be investigated with the help of molecular dynamics simulations (MD) on the one hand and on the other hand on the basis of micropraeparative approaches. As part of the project, the influence of manganese (Mn) on the formation of LiAlO₂ from Al₂O₃, MgO, CaO, Li₂O, MnO, SiO₂ melts will be analyzed. Manganese occurs in particular during the recycling of lithium-ion batteries, which are used as energy storage devices from smartphones to electric cars, and significantly alters the formation of lithium compounds and hinders the crystallization of LiAlO₂. The processes that occur immediately before solidification in the melt are investigated with the aid of molecular dynamics simulations. The microstructure of the solidified compounds is characterized with the aid of microsample preparation, the use of inkjet printing technology and material analysis tools. The aim of the project is to understand and predict the processes relevant to the solidification of the slags in order to enable the efficient recycling of Li-ion batteries and thus circular battery production.

• S. Chakrabarty, D. A. De Abreu, I. A. Alhafez, O. Fabrichnaya, N. Merkert, A. Schnickmann, T. Schirmer, U. E. A. Fittschen, M. Fischlschweiger, Kinetics of γ-LiAlO2 Formation out of Li2O-Al2O3 Melt—A Molecular Dynamics-Informed Non-Equilibrium Thermodynamic Study Solids 5:561, DOI: 10.3390/solids5040038, 2024.
• S. Hampel, I. A. Alhafez, A. Schnickmann, S. Wunderlich, H. Li, M. Fischlschweiger, T. Schirmer, N. Merkert, U. E. A. Fittschen. Experimental and Simulation Studies on the Mn Oxidation State Evolution of a Li2O-MnOx-CaO-SiO2 Slag Analogue. Minerals 14(9):868, 2024.
• S. Hampel, I. A. Alhafez, T. Schirmer, N. Merkert, S. Wunderlich, A. Schnickmann, H. Li, M. Fischlschweiger, U. E. A. Fittschen. Engineering Compounds for the Recovery of Critical Elements from Slags: Melt Characteristics of Li5AlO4, LiAlO2, and LiAl5O8. ACS Omega, DOI: 10.1021/acsomega. 4c00723, 2024.
• U. E. A. Fittschen, S. Hampel, T. Schirmer, N. Merkert. Multimodal spectroscopy and molecular dynamic simulations to understand redox-chemistry and compound formation in pyrometallurgical slags: example of manganese oxidation state with respect to lithium recycling. Appl. Spectrosc. Rev., DOI: 10.1080/05704928.2024.2350988, 2024.

• Prof. Dr. Nina Merkert