新型过渡金属磷化物钠离子电池负极材料的可控合成及同步辐射研究

Sodium-ion batteries (SIBs), which compare with traditional lithium-ion batteries (LIBs), have been considered as the most promising next generation energy storage system because of the advantage of rich in resources, similar properties with lithium and low cost. However, the formation of dendrites and the safety issues related to sodium metal currently prevent its use as a negative electrode for commercial applications, so the choice of anode materials for SIBs is still huge challenge. Transition metal phosphides have unique crystal structures and exhibit excellent electrochemical performances in the field of energy storage and conversion. This project aims to realize the transition metal phosphides (TMPs) anode materials controllable synthesis and structure optimized with functional carbon materials. In situ synchrotron radiation X-ray absorption spectroscopy (SR-XAS) is used to investigate the local geometry and electronic structure changes during the charge-discharge process. It can understand the related reaction mechanism and kinetics process. Combine with electrochemical test techniques further study the structure and properties of TMPs anode materials. Our works contribute to know the storage sodium properties of TMPs and provide theoretical and experimental basis for develop advanced anode materials of sodium-ion batteries.

与传统锂离子电池（LIBs）相比，钠离子电池（SIBs）因钠资源丰富、成本低廉和可用性强等独特优势，在大型储能体系中的应用备受关注。但活泼性高的金属钠在充放电过程中容易形成枝晶，所以SIBs负极材料的选择存在巨大的挑战。过渡金属磷化物（TMPs）具有特殊的晶体结构，在能源存储与转化领域表现出优异的电化学性能。本项目拟选取TMPs负极材料作为研究对象，通过调控化学湿法工艺可控合成不同结构的TMPs材料，并结合多种功能碳材料对其进行复合结构优化；利用同步辐射X射线吸收谱技术对TMPs电极材料动态工作机制进行原位表征，明确其在钠离子嵌入/脱嵌过程中的结构变化规律，从而揭示其相关储钠机理和相关动力学过程；结合电化学测试等技术深入理解TMPs的结构与电池性能之间的关系。本项目的研究有助于进一步认识过渡金属磷化物电极材料的工作机制，为发展下一代SIBs负极材料提供研究依据。

相比于传统石墨，过渡金属硫/磷化物具有较高的理论容量，是具有潜力的高能量密度电极新材料。然而，充放电过程中的体积膨胀效应和中间产物较差的可逆性严重制约其性能的进一步提升和实际应用。本项目针对以上问题，通过软模板法工艺可控合成不同结构的过渡金属硫/磷化物，并结合多种功能碳材料对其进行复合结构优化，解决低倍率和短循环寿命问题，实现高导电性、高稳定性的调制与可控合成；利用同步辐射X射线吸收谱和原子分辨电镜技术研究不同物相、复合功能碳材料和多级微观结构等对其电化学性能的影响规律；利用电化学和其他测试手段，阐明化合物氧化还原反应的相关动力学反应过程。本项目的预期结果将为下一代高性能储能电池的实际应用提供理论与实验依据。