原子层沉积技术改性钠离子电池正极材料的研究

The cathode dissolution upon cycling results in poor electrochemical performance of NFM for sodium ion batteries. In this project, an advanced technique of atomic layer deposition is used to coat four types of layers (Al2O3、ZrO2、Al2O3/ZrO2 and NaAlO2) onto NFM surface (both of the powder and the electrodes) to address the challenges of the cathode materials. It mainly focuses on important effects of four types of coating layers on the interaction between NFM and electrolyte using synchrotron radiation technique, and the related models are designed to explain the obtained results, and the effects of its interaction on sodium storage into NFM are established. This project significantly figures out what the improvement difference is from powder based coatings and electrode based coatings. Through comparing different coating effects, it addresses the advantages of solid state electrolyte coatings in improving NCM622 performance. It is expected that this project could provide some significant theoretical standpoints and practicable strategies in the applications of NFM based high performance sodium ion batteries.

钠离子电池正极材料NaNi1/3Fe1/3Mn1/3O2（NFM）存在循环过程中金属溶解缺点，导致其循环寿命降低。本项目采用先进的原子层沉积技术在NFM表面（粉末表面和电极表面）沉积四种包覆层（Al2O3、ZrO2、Al2O3/ZrO2和NaAlO2）。运用同步辐射技术研究不同包覆层对NFM与电解液界面间相互作用的影响，调控其相互作用并探讨其内在联系。研究粉末表面改性和电极表面改性的异同点，重点研究固体电解质包覆层改善正极材料性能的优势，为建立高性能钠离子电池提供理论依据和实践指导。

P2型层状三元金属氧化物作为一类主要的钠离子电池正极材料，具有高可逆比容量和原料广泛等优势。但此类材料在充放电过程中涉及到复杂的不可逆相变问题、体积膨胀严重以及结构稳定性较差等缺点。原子层沉积技术作为一种有效的电极材料表面改性技术，能够有效提升NCM电极材料的电化学性能。本项目重点研究了P2型NCM正极材料的可控制备方法，实现了均匀、超薄、高度可控包覆层的构筑，先后完成了纳米尺度Al2O3，AlPO4，Fe3O4，ZrO2，TiO2的可控包覆，深入研究了包覆层结构、组成、厚度等对钠离子电池电化学性能，利用同步辐射阐明ALD技术对改性NCM的关键影响因素，提出高性能ALD包覆层改性NCM钠离子电池正极材料的理论设计依据。最后在不同温度下进行退火处理，创造性的得到利用原子层沉积诱导技术实现金属离子表相掺杂的NCM正极材料。项目研究为钠离子电池正极材料的后续优化研究提供了直接的理论指导和现实依据。