固态电池中高比能正极材料结构演化规律及界面问题研究

Compared with Li-ion batteries with liquid electrolytes, solid-state batteries are topics of much research interest owing to their higher safety and higher energy density. Currently, the research of solid-state battery mainly focuses on the R&D of suitable solid electrolytes with high ionic conductivity at room temperature, low interfacial resistance and wide electrochemical window. Solid-state batteries are a complex system, developing of cathode materials that reducing the interfacial reaction, increasing the physical contact of the solid electrolytes with the cathode materials, and improving the interface impedance, are indispensable as well as solid electrolytes. This project intends to use high-energy single-crystal high-nickel NCM cathode material as a model system to solve the interface problems between solid electrolytes and cathode materials by interfacial modification of mixed ionic conductor. Studying the physical and chemical changes, such as the interface reactions, ion and electron transport and charge transfer between cathode materials and solid electrolytes, the surface reconstruction and crystal structure evolution of cathode materials in solid-state batteries during the long cycling, by using In-situ XRD, ex-situ STEM, synchrotron radiation X-ray absorption spectroscopies and X-ray three-dimensional imaging technologies. This project can serve as valuable design guidelines for the the R&D of solid-state batteries.

与传统锂离子电池相比固态电池具有高比能和高安全等优点而成为研究热点。目前固态电池的研究主要集中在研发高室温离子电导率、低界面电阻、宽电化学窗口的固体电解质材料。固态电池是一个复杂体系，开发适用于固态电池的正极材料，降低界面反应、提高固体电解质与正极材料的物理接触、改善界面相容性同样重要。本项目拟以高比能单晶高镍三元正极材料为模型，通过柔性混合离子导体材料界面修饰来解决固态电池界面问题。通过原位XRD、半原位STEM、同步辐射X射线吸收谱、X射线三维成像等先进分析表征测试技术，研究固态电池中正极材料与固体电解质的界面化学与电化学反应、离子与电子输运、电荷转移等过程，研究固态电池中正极材料的表面组成、晶体结构、内应力等在长循环过程中的物理化学变化，为固态电池的研发提供理论基础。

与传统锂离子电池相比固态金属锂电池由于兼具高能量密度与高安全性而受到了广泛的关注，经过不懈的努力，高离子电导率的固态电解质、无枝晶的金属锂负极、适用于固态电池高容量正极材料及固态电池界面问题研究等方面均已取得了长足的进步。在本项目的支持下开发了更适用于固态电池的高容量单晶高镍正极材料，系统研究了单晶高镍三元正极材料锂离子扩散机制，提出高价态过渡金属离子镍位梯度掺杂以提高锂离子扩散动力方法；建立了以化学反应促浸润的界面均匀包覆改性方法，开发了多种高镍正极材料界面稳定化技术。多尺度、多物理场下研究了正极界面演化与载流子输运机制，提出了从离子导体包覆到原位化学/电化学协同构筑非晶CEI等一系列固态电池正极侧界面问题解决策略，研制出能量密度大于400Wh/kg固态锂电池。本项目取得了突出的研究进展与原创成果，为适用于固态电池高容量正极材料的研发与高比能先进固态电池界面问题研究提供了参考。