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

电动汽车的发展导致锂离子电池（LIB）及其回收利用的重要性增加，以回收有价值的过渡金属，如Co和Ni以及Li。第二代LIB含有Li（Co 1-x-yNixMny）O2固溶体形式或用作阴极材料的尖晶石LiMn 2 O 4形式的Mn。火法冶金方法，如在低氧分压下发生的还原熔炼，允许分离在金属合金中完全转化的重金属（Co、Ni、Cu）和Li以及大部分富集在炉渣中的Mn。渣料以Al 2 O3为基料，加入SiO2和CaO作为助熔剂。因此，Li_2 O-Al_2 O_3-SiO_2-MnOx体系与锂的回收过程有关。该系统的热力学数据库可用于优化渣中锂浓度最大化的条件。该项目的目的是利用基于占位晶体结构信息的固溶体热力学模型和用于液相的两个亚晶格部分离子液体模型，开发Li 2 O-Al 2 O3-SiO2-MnOx系统的热力学数据库。将采用CALPHAD方法评估该系统及其子系统的热力学参数。工作计划将包括相平衡研究、热分析、热力学值的量热测量以及固体和液体溶液的高级热力学建模。将根据文献中的实验信息和自己的结果重新评估边界子系统的热力学描述。首次研究了Li_2 O-MnOx-Al_2 O_3和Li_2 O-MnOx-SiO_2体系的相平衡，并绘制了相图。相平衡研究将包括样品合成和长时间热处理。样品中存在的相将通过X射线衍射和微观结构表征来鉴定。熔融关系将使用差热分析（DTA）进行研究，然后使用电子显微镜（SEM/EDX）进行微观结构分析。将使用差示扫描量热法（DSC）测量化合物的热容。根据实验结果推导出Li_2 O-Mn_x-Al_2 O_3和Li_2 O-Mn_x-SiO_2体系的热力学描述，最后将边界体系的热力学数据库结合到Li_2 O-Al_2 O_3-SiO_2-Mn_x体系的热力学描述中。将进行与锂回收相关的成分的关键实验，以验证热力学计算并改进数据库。所得热力学数据将用于还原熔炼后炉渣成分的预测。

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.