Thermodynamic database development for the Li2O-Al2O3-SiO2-MnOx system: application for Li recycling

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Development of electromobility resulted in increasing of importance of lithium ion battery (LIB) and their recycling to recover valuable transition metals such as Co and Ni as well as Li. Second generation of LIB contains Mn either in form of Li(Co1-x-yNixMny)O2 solid solution or in spinel LiMn2O4 used as cathode material. Pyrometallurgical methods such as reduction smelting occurring at low oxygen partial pressure allow separation of heavy metals (Co, Ni, Cu) which completely converted in metal alloy and Li together with most of Mn concentrating in slag. The slag material is based on Al2O3 with SiO2 and CaO introduced as flux. Therefore, the Li2O-Al2O3-SiO2-MnOx system is relevant to process of Li recycling. Thermodynamic database of this system can be used to optimize conditions for maximal concentration of Li in the slag. The aim of the proposed project is to develop thermodynamic database for the Li2O-Al2O3-SiO2-MnOx system using thermodynamic models of solid solutions based on crystal structure information about site occupancies and two-sublattice partially ionic liquid model for liquid phase. The CALPHAD approach will be applied for assessment of thermodynamic parameters of this system and its sub-systems. The work program will include phase equilibrium investigations, thermal analysis, calorimetric measurements of thermodynamic values and advanced thermodynamic modelling of solid and liquid solutions.Thermodynamic descriptions of bounding sub-systems will be re-assessed based on experimental information from literature and on own results. Phase equilibria in the Li2O-MnOx-Al2O3 and Li2O-MnOx-SiO2 systems will be investigated and phase diagrams will be constructed for the first time. Phase equilibrium study will include sample synthesis and prolonged heat treatment. Phases present in sample will be identified by X-ray diffraction and microstructure characterization. Melting relations will be investigated using differential thermal analysis (DTA) followed by microstructure analysis using electron microscopy (SEM/EDX). Heat capacity of compounds will be measured using differential scanning calorimetry (DSC). Thermodynamic descriptions of the Li2O-MnOx-Al2O3 and Li2O-MnOx-SiO2 systems will be derived based on own experimental results.Finally, the thermodynamic databases for bounding systems will be combined into description of the Li2O-Al2O3-SiO2-MnOx system. Key experiments for compositions relevant to Li-recycling will be performed to verify thermodynamic calculations and improve database. The derived thermodynamic database will be used to predict slag composition after reduction smelting.