硅薄膜电极充放电形态和微裂纹演化机理的实验研究

The evolution of configurations and micro cracks of silicon thin film anode during its charge-discharge process is investigated in this project through the development of microscopic electrochemical in situ test platform. The electrochemical process of the silicon thin film anode can be measured in situ by matching the optical micro system with the electrochemical circuit. Based on the multiscale grid method utilizing the multi-frequency gratings, the appearance, the growth and the propagation of micro- damages such as micro cracks, as well as the evolution of thin film configurations such as the curvity are quantitatively characterized. The influences of external factors, such as load voltage, charge and discharge times and internal factors, such as the initial residual stress and geometric properties on the evolution of configurations and micro cracks of silicon thin film anode are also investigated. The multiscale mechanical evolution model is established to reveal the damage process and failure mechanism. The study in this project will provide a theoretical and experimental tool to design novel silicon thin film anode.

本项目拟通过研制光学显微电化学原位实验测试平台对硅薄膜电极结构在电化学环境中的充放电形态和微裂纹演化机理进行研究。通过将光学显微系统与电化学回路匹配，可实现对薄膜电极电化学过程进行原位测量。利用基于多频格栅变形载体的多尺度网格法对微区损伤，如微裂纹的形成、生长和扩展，以及薄膜电极结构的充放电形态，如三维形貌、曲率等演化过程进行在线定量表征。研究加载电压、充放电次数、薄膜初始残余应力、几何规格等多物理参量对薄膜电极结构充放电形态和微裂纹演化特征的影响规律，建立充放电形态和微裂纹演化的力学关联模型，揭示其损伤过程和失效机理。为设计新型硅薄膜电极、预测其使用寿命提供必要的研究。

硅基材料因其容量高、低脱锂电位和低成本等优点被认为是下一代锂离子电池最具有潜力的负极材料。然而硅电极在脱锂嵌锂过程中会产生巨大的体积膨胀和很高的应力，从而引起电极结构的力学损伤和电化学性能的大幅度衰减，最终致使电池寿命衰退。本项目针对硅薄膜电极在充放电过程中的损伤力学问题开展研究。研究内容如下：.（1）通过设计光学显微电化学原位实验测试平台，对硅薄膜电极结构在电化学过程中的充放电形态和微裂纹演化机理进行研究。.（2）对硅薄膜电极结构的充放电形态和微裂纹演化过程进行实时表征。.（3）分析不同物理参量对薄膜电极结构演化过程的影响规律，建立相应的损伤演化模型，揭示其演化机理。.重要研究结果包括：设计并研发了基于光学显微平台的电化学反应电解池，实现多尺度观察和测量；发展了基于激光扫描技术的三维DIC表征方法；对硅薄膜的充放电形态及变形场进行在线表征；最后，建立了多层硅碳纳米球壳复合电极材料的扩散应力模型。.本项目的开展对进一步研究硅薄膜电极的力-电化学耦合效应提供了理论依据和有效实验数据，为研发下一代高比容量锂离子电池提供技术支持。