钾离子电池碳基负极材料的储钾机理、性能优化与应用研究

Carbon-based materials are of particular interest as anode of potassium ion batteries. Challenges associated with carbon-based anode lie in i) the unclear K+ storage mechanism, and ii) the poor first cycle Coulombic efficiency and cycling stability. Here operando studies including in-situ Raman and in-situ XRD characterizations, in combination with ex-situ characterizations (i.e., XPS, FTIR) and density-functional theory (DFT) calculations will be carried out to correlate the real-time electrochemical K+ intercalation/de-intercalation process with structure/component evolution of potassium-graphite intercalation compounds (K-GICs). Furthermore, electrochemical performance in terms of the first cycle Coulombic efficiency and cycling stability can be enhanced through three-dimensional electrode design and the optimization of the SEI layer composition/morphology. Full cell based on carbon-based anode and vanadium-based cathode (i.e., KVOPO4, KVPO4F) will be designed and evaluated. The success of this project will promote better fundamental understanding of the K+ storage mechanism in graphite and provide invaluable guidelines for the design of high-performance electrode materials as well as high-performance KIBs.

碳基材料是钾离子电池最主要的负极材料体系，但目前还存在钾离子存储机理不明、首次库伦效率低以及循环稳定性能差等问题，这些因素严重阻碍了钾离子电池及技术的发展与应用。针对这些问题，本项目提出利用原位拉曼、原位X射线衍射技术、半原位X射线光电子能谱分析和半原位傅里叶红外分析技术和理论计算相结合的方式，深入解析钾-石墨层间化合物(K-GICs)的结构、组分演变与相转变规律，阐明碳负极材料的电化学储钾机理；设计出三维自支撑碳电极材料，并基于电解质优化对SEI膜组分/结构进行调控和设计，改善电极材料的循环稳定性和库伦效率；再以磷酸钒钾、氟磷酸钒钾等为正极材料，研制出性能优异的钾离子全电池。项目的实施可促进对碳基负极材料储钾机理的深入理解，并为高性能钾离子电池及其电极材料的设计与开发提供理论依据和借鉴。

针对碳基负极材料电化学储钾机理不清晰、界面物化特性及其影响储钾特性的作用机制不明、循环稳定性能差等瓶颈问题，本项目采用多原位谱学电化学表征（原位拉曼、原位傅里叶转换红外光谱、X射线光电子能谱（XPS））和理论计算相结合的研究方法，实现了对电化学嵌/脱钾过程中钾-石墨层间化合物（K-GICs）相转变过程的精准捕获和可视化处理，阐明了K-GICs结构、组分演变与相转变规律，揭示了碳负极材料的电化学储钾机理；阐明了不同电解液环境、不同碳材料类型下，碳基负极表面SEI膜的组分、结构、形成机制和演变规律，揭示了碳基负极/电解液界面电化学反应机理及其影响储钾特性的内在作用机制；明确了影响碳基负极电化学储钾特性的关键因素，理论指导实验，采用异质元素掺杂和/或孔结构调控、并结合电解液优化，显著提升了碳基负极的循环稳定性和库伦效率，构筑出高性能钾离子混合电容器。.相关研究成果构建了碳基负极电化学储钾的理论基础，为高性能碳基负极设计和钾离子电池开发提供了重要的理论指导和实验借鉴。