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

电迁移率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Co、Ni和Li。第二代LiB以Li(Co1-x-yNixMny)O2固溶体或作为正极材料的尖晶石LiMn2O4的形式含有Mn。在低氧分压下进行还原熔炼等火法冶炼，可以将重金属(Co、Ni、Cu)完全转化为金属合金和Li，并使大部分Mn集中在炉渣中。渣料以Al_2O_3为基础，引入SiO_2和CaO作为助熔剂。因此，Li_2O-Al_2O_3-SiO_2-MnO_x系统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Li的最大浓度条件。该项目的目的是建立Li2O-Al_2O_3-SiO_2-MnO_x系统的热力学数据库，使用基于晶格占位信息的固溶体热力学模型和液态的两亚晶格部分离子液体模型。CALPHAD方法将被应用于该系统及其子系统的热力学参数的评估。工作计划将包括相平衡研究、热分析、热力学数值的量热测量和先进的固体和液体溶液热力学模型。将根据文献中的实验信息和自己的结果重新评估束缚子系统的热力学描述。我们将研究Li2O-MnOx-Al_2O_3和Li_2O-MnO_x-SiO_2系统的相平衡，并首次绘制相图。相平衡研究将包括样品合成和延长热处理时间。样品中存在的物相将通过X射线衍射和微观结构表征进行鉴定。熔化关系将用差热分析(DTA)来研究，然后用电子显微镜(SEM/EDX)进行微观分析。化合物的热容将使用差示扫描量热仪(DSC)进行测量。根据自己的实验结果，推导出Li2O-MnOx-Al_2O_3和Li_2O-MnO_x-SiO_2体系的热力学描述。最后，结合束缚体系的热力学数据库来描述Li_2O-Al_2O_3-SiO_2-MnO_x体系。将对与锂回收有关的组份进行关键实验，以验证热力学计算和完善数据库。建立的热力学数据库将用于预测还原熔炼后的炉渣成分。

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.