Project Details
Projekt
Investigation of phase formation and phase constitution in the systems Li-Mg-Al-O and Li-Al-Mn-O with special focus on spinel solid solutions
Applicants
Professor Dr.-Ing. Alfred Ludwig; Dr. Thomas Schirmer
Subject Area
Mechanical Process Engineering
Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 470309740
Our previous work identified that additional to LiAlO2, Li-manganates (e.g. LiMnO2 or Li2MnO3) are promising EnAM phases, that crystallize in synthetic slags with high purity. The formation of Li-manganates is expected to be adjustable by controlling the Mn oxidation state, namely by preventing the formation of Mn-containing spinels by stabilizing Mn4+ rather than Mn2+/3+ states with processing conditions. In addition, Li-manganates are interesting for direct reuse as cathode material in Li-ion batteries. The continuation of our joint project will therefore focus on exploring the possibilities of Li-manganates as new EnAM phases, and how their formation correlates with LiAlO2 formation. Combinatorial thin film materials libraries of the ternary and quaternary subsystems Li-M1-M2-O, with M1, 2 = Mn, Al, Mg, Fe, will be prepared by sputter deposition and investigated with high-throughput methods to study the phase formation of the systems, in particular to evaluate all possible Li-manganates in dependence of the Mn speciation. The formation of the compounds identified as potentially suitable EnAM phases (presumably Li-manganates) will then be studied in synthetic slags comprising additional elements like Si and Ca. Synthetic slag samples will be prepared at various O2 partial pressures and investigated by X-ray diffraction, electron probe microanalysis, nanoscale mass spectrometry and thermoanalysis. In conjunction with thermodynamic modeling, these experimental results will provide insight into the solidification behavior of Li-manganates in Ca-silicate slag and in presence of limited amounts of common minor elements (contaminants) like Mg and Al. Additionally this results will help to optimize cooling curves for maximum scavenging efficiency and favorable grain morphology and size. In addition to Ca-silicate slags, fayalitic slags (Fe2SiO4-dominated) are investigated, as they maximize the available oxygen in the melt due to their potential to significantly increase oxygen transport into the melt, which should lead to better oxidation of the Mn in the melt (e.g. stabilization of Mn4+). To assess the suitability of the Li-manganates formed in the synthetic slag and thin film samples for direct reuse as cathode materials in Li-ion batteries, the nanostructure of selected samples will be additionally investigated using aberration-corrected transmission electron microscopy and atom probe tomography. All results combined will provide a better insight into the stability of Li-manganates, their properties and their recoverability from lithium-containing slags.
DFG Programme
Priority Programmes
