LiNixCoyMnzO2-SO3体系中元素相互结合的规律及其控制因素研究

From the view of the sustainable development of social economy, the spent lithium-ion-batteries (LIBs) are a kind of valuable resource. At present, there are still obvious deficiencies in understanding the physical and chemical properties of cathode materials for lithium ion batteries under different physical and chemical conditions, which are the main bottlenecks restricting the development of key technologies for clean and high efficient recycling. Based on the interdependence between element activity and its environment, this work studies the form and force of element associations in LiNixCoyMnzO2-SO3 system, reveals occurrence of elements and its evolution rule in sulphating roasting, establishes the chemical model of element migration, identifies the thermodynamics and kinetics mechanism during chemical transformatio, builds the mathematical model describing the elements association behavior of LiNixCoyMnzO2-SO3 system and the nature of elements and environmental factors, and builds a mathematical model describing the transport, speed and mechanism of material and energy during chemical processes, forms the theoretical basis of element migration controlling. The work can lay a theoretical foundation for the controlling of the pollution and the design of the key technology for clean and high efficient recovery of spent Li-ion batteries.

从社会经济可持续发展角度来看，报废锂离子电池是一种宝贵的资源。当前对锂离子电池正极材料在不同环境物理化学条件下呈现出物理性质、化学性质的认识仍存在明显的不足，这是制约报废锂离子电池清洁高效回收再利用关键技术开发的主要瓶颈。本项目从元素活动与其所处环境相互依存的角度出发，深入研究LiNixCoyMnzO2-SO3体系元素之间相互结合的结合方式和结合力。揭示元素在酸性环境中所处的赋存形式及演变规律、元素的分布分配特征，建立元素迁移的化学模型，查明化学转化过程中物质化学运动的热力学和动力学机制，构建描述LiNixCoyMnzO2-SO3体系元素的结合行为与元素的性质、环境因素，描述化学作用过程中物质和能量的输运、作用速度与机制的数学模型，形成元素迁移控制的理论基础。项目的研究能够为控制报废锂离子电池对环境的污染及其清洁高效回收关键技术的设计奠定理论基础。

为掌握具有人工合成特色的LiNixCoyMnzO2(0< x,y,z <1)材料的基础化学性质，并促进报废动力锂离子电池的资源化循环利用，本项目开展了LiNixCoyMnzO2(0< x,y,z <1)材料在含有SO3气体的气相中发生化学演变的规律与控制机理研究。研究结果如下：.计算获得LiNi1/3Co1/3Mn1/3O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.6Co0.2Mn0.2O2和LiNi0.8Co0.1Mn0.1O2三元材料的△H298θ、△G298θ、CP298分别是−705.17 kJ·mol−1、−703.90 kJ·mol−1、−705.39 kJ·mol−1和−695.67 kJ·mol−1；−642.41 kJ·mol−1、−640.04 kJ·mol−1、−647.98 kJ·mol−1和−631.10 kJ·mol−1；78.96 J·mol−1·K−1、78.69 J·mol−1·K−1、79.77 J·mol−1·K−1和75.72 J·mol−1·K−1。LiNi1/3Co1/3Mn1/3O2在酸性焙烧环境中发生了化学转化的原因是Li元素首先从α-NaFeO2型层状结构中脱出，破坏了层状结构的稳定性以及Li、Ni、Co、Mn元素氧化物在SO3气氛中较差的热力学稳定性有关。LiNi1/3Co1/3Mn1/3O2中各元素相应的双金属硫酸盐的生成顺序为Li > Ni, Co > Mn。LiNi0.8Co0.1Mn0.1O2与NaHSO4·H2O按一定比例混合经过焙烧后，Li元素以LiNaSO4的形式存在，Ni、Co、Mn元素的赋存形式为NiO、CoMn2O4。LiNi0.5Co0.2Mn0.3O2(NCM523)-NaHSO4∙H2O体系，焙烧过程晶系的转变为：Hexagonal（六方晶系）→Tetragonal（正方晶系）→Orthorhombic（正交晶系）→Cubic（立方晶系）→Monoclinic（单斜晶系）。LiNi0.6Co0.2Mn0.2O2、LiNi0.8Co0.15Al0.05O2、LiMn2O4在含有SO3气体的酸性焙烧气氛中能够自发进行化学变化，过渡族金属Ni、Co、Mn元素均倾向于以低价态形式存在，但Ni、Co、Mn元素赋存形式变化规律有自己的特征。