卷曲法构筑高性能单根硅微米管锂电池器件及其SEI膜的表征研究

Solid electrolyte interphase (SEI) on the electrode surface of lithium-ion batteries plays a crucial role in determining the electrochemical performance such as specific capacity, rate capability, cycle life, as well as chemical and physical stability, which is regarded as one of most hot and challenge topics that the world is facing today. In this project, the single Si microtube battery will be fabricated by rolled-up method, and will be applied to the study of the SEI formation and its properties. The in-situ micro Raman spectroscopic and electric transportation analyses of a single Si microtube electrode will be performed at a fixed charge/discharge sate. Through a combination of various characterization methods such as Auger Electron Spectroscopy (AES), Electrochemical Impedance Spectroscopy (EIS), and Transmission Electron Microscopy (TEM), the formation voltage, interface composition and depth profile, Li-ion intercalation and de-intercalation interface reaction, and properties of SEI layers will be explored, and the effect on the performance of lithium ion battery will be discussed as well. The exploration of the formed metastable state Si/Li alloys formed at different lithiation conditions and the variation of micro Raman spectroscopy will be symmetrically performed. The systematic investigation of the properties of SEI layers and intrinsic reason of capacity decay will be performed based on quantum chemical calculation. The research in this project is expected to provide helpful reference for the future design of lithium ion batteries, which can be a guidance to improve the properties of SEI layers, reduce the irreversible capacity at the first cycle, and improve the cycling performance.

锂离子电池固体电解质界面膜（SEI）的表界面结构是影响器件性能的决定性因素之一，其对比容量、倍率性能、循环寿命、物理和化学稳定性等都有着非常显著的影响，现已成为国际上研究的热点和难点。本项目拟通过新颖的卷曲法组装单根Si微米管锂离子电池器件，并将其应用于锂电池SEI膜的表界面研究。在任一充放电状态下，实现单根Si微米管电池的微区拉曼光谱、电子输运性能的原位表征；通过联合俄歇电子能谱、电化学阻抗、透射电子显微镜等表征手段研究单根Si微米管锂电池SEI膜的形成电位、组成和厚度、嵌脱锂反应界面特性对锂电性能造成的影响，揭示在电化学反应过程中Si与Li形成不同亚稳态合金中间物嵌锂形成电位及微区拉曼谱学变化特征。结合量子化学的理论计算，深入探究SEI膜表界面反应特性和容量衰减的内部规律，提出改性SEI膜性能的方法，为减少首次不可逆容量、提高电池的循环性能提供有益的借鉴和参考。

近来的研究表明锂离子电池材料的表界面结构是影响器件性能的决定性因素之一，其对电池的充放电效率、倍率、循环性能、储存寿命都有非常显著的影响。本项目通过卷曲法和其它有效方法构造了单根硅基锂离子电池器件，对电池固态电解制膜的组成和厚度、材料储锂机制进行研究。系统研究电化学反应过程中硅与锂形成不同亚稳态合金中间物的电导率变化和谱学特征，研究了电化学反应过程中电极的结构演化、电子迁移率变化以及锂离子的扩散速率，通过实验与理论计算相结合的方法研究相关的表界面结构和特性。在三年的项目执行期间，按照原计划开展了系统性研究，并取得了预期的研究成果，顺利完成了预期的考核指标。我们合成了一系列负级材料，并研究了其电化学性能与储能机理。并且，我们有目的进行电极材料的结构设计，实现对电极材料结构基元的组装调控，并结合表面修饰、有效复合与改性等手段提高电极材料的循环稳定性和倍率性能，最终开发出一系列有前景的高容量和高能量密度的锂电池材料。通过本项目的实施共发表SCI论文18篇，包含发表在一些高水平期刊上如Chemical Society Review（通讯作者）, Advanced Materials（通讯作者），Advanced Energy Materials（通讯作者），Advanced Functional Materials（通讯作者），ACS Nano（通讯作者）等，在锂电池与材料改性方面获得授权发明专利5项