阳离子有序/无序结构富锂正极材料的可控构筑及其晶格氧的氧化还原反应机制研究

Li-rich solid solution is one of the most promising cathode materials to develop high-energy-density (>300 Wh/kg) Li-ion batteries. It is the key to promote the electrochemical properties of these materials to deeply understand their structural properties and the redox mechanism of lattice oxygen. In this project, by introducing high-valent transition metal cations and optimizing crystallization and solid solution conditions, Li-rich cathode materials with cation ordered/disordered structure could be constructed controllably, and the influence mechanism of related structural characteristics on the redox behavior of lattice oxygen could be clarified. The mechanism of anion co-precipitation doping, solvent thermal or molten salt sintering activation post-treatment on the redox activity and stability of lattice oxygen could be investigated. With the help of synchrotron radiation measurements, atomic-scale imaging techniques, in-situ dynamic characterization techniques, and first-principles calculation methods, the redox reaction mechanism and regulatory mechanism of lattice oxygen could be thoroughly understood, and the intrinsic relationship between the redox behavior of lattice oxygen and electrochemical properties could be clarified. The design idea of achieving high-performance Li-rich cathode materials could be proposed based on the atomic/electronic level and electrochemical fundamental principle. The implementation of this project is expected to lay a solid foundation for the development of high-performance cathode materials and the commercial application of Li-ion batteries, and is of great significance to the development of electrochemical theory.

富锂固溶体是发展高能量密度（大于300 Wh/kg）锂离子电池的重要候选正极材料之一，具有较大潜在应用价值。深入理解该类材料的结构特性及晶格氧的氧化还原反应机理是提升其电化学性能的关键。本项目将通过引入高价态过渡金属离子，优化结晶与固溶反应条件，可控构筑具有阳离子有序/无序结构的富锂正极材料，明确其结构特性对晶格氧氧化还原行为的影响机制；探明阴离子共沉淀掺杂、溶剂热或熔融盐烧结活化后处理对晶格氧氧化还原反应活性与稳定性的作用机制。结合同步辐射技术、原子尺度成像技术、原位动态表征技术与第一性原理计算方法，深入理解晶格氧的氧化还原反应机理及调控机制，明确晶格氧氧化还原行为与电化学性能的内在联系，从原子电子层次及电化学本质意义上提出高性能富锂正极材料的设计思想。本项目的实施将会为高性能正极材料的开发及在锂离子电池的商业化应用打下坚实基础，对电化学理论发展具有重要意义。

基于晶格氧可逆变价的富锂锰基氧化物是发展低成本、高比能锂离子电池的重要候选正极材料。本项目针对富锂锰基正极材料电压滞后、容量衰减等关键问题，围绕材料结构设计合成、晶格氧氧化还原及其储锂构效关系开展研究。通过控制化学组成，实现了富锂锰基材料的锂-氧-锂结构单元及过渡金属-氧局域电子结构调制，明确了晶格氧氧化还原与过渡金属离子迁移对电压迟滞的影响；通过熔融盐辅助烧结、水热后处理方法实现了富锂锰基材料体相、表面阳离子无序结构的构筑，基于阳离子无序调制的优异热力学与动力学特性提升了晶格氧变价可逆性与电化学反应速率；采用聚阴离子表面梯度掺杂构建了兼具阳离子有序/无序结构的高稳定界面层，通过抑制高电压下晶格氧的不可逆析出与过渡金属溶解，增强了长循环容量与电压保持率；通过建立加速电池性能衰减的综合测试环境，明确了不同工况下的电极结构劣化特征及其对电池性能的影响。在本项目中，结合理论计算、动态表征技术及电极化学可视化成像技术，从原子尺度微观结构及电子结构层次揭示了在阳离子有序/无序框架下的晶格氧演变规律，探明了晶格氧变价可逆性与结构稳定性的热力学与动力学控制因素，阐明了电压滞后、容量衰减的影响规律与改善机制。本项目的实施有望为高性能富锂锰基正极的设计制备提供关键技术手段和理论支撑，促进锂离子电池在更高层次上发展。截止目前，在国家基金的资助下，共发表SCI收录论文26篇，论文目前被引400余次。申请国家发明专利7项。