基于原位测试系统下碳化硅复合电极不同倍率下的应力演化

Stress Evolution of Silicon Carbide Composite Electrode at Different Magnifications Based on In-Situ Test System

摘要: 锂电池的负极材料性能对电池的整体特性具有重要影响。本文选用比石墨具有更高容量的碳化硅作为负极材料，系统分析其应力和杨氏模量等性能。本文提出了一种原位实验方法，用于实时观测并记录双层悬臂梁电极在电化学循环中的弯曲变形过程，并建立相应力学模型，从实验角度获得碳化硅复合电极应力、应变和杨氏模量等力学性能参数，这些结果将有助于开发更加稳定耐用的高容量锂离子电池。基于力学模型和原位测量系统，调整充电倍率并进行电化学循环，分析并讨论不同倍率对电极力学性能参数的影响。对于0.1C充电倍率，将继续采用上述计算结果。而更高的充电倍率，考虑到快速充电会引起锂离子浓度c在厚度方向上分布不均，假设锂离子浓度在厚度方向上存在浓度梯度，进一步提出了一套考虑浓度梯度的物理模型。快速充电下锂离子在活性层分布不均，各局部应力应变有较大差异，充电过程中曲率变化的波动性较大，而慢充下锂离子的分布相对均匀，曲率变化在充放电过程中均有相对稳定的趋势。随着锂化程度越高，电极的弯曲变形越大，在同一充放电状态下，快充引起的电极变形大于慢充引起的变形，慢充可以使电极保持良好的结构。

Abstract: The anode material performance of lithium battery has an important influence on the overall char-acteristics of the battery. In this paper, silicon carbide with higher capacity than graphite is selected as the negative electrode material, and its stress and Young’s modulus are systematically analyzed. In this paper, an in-situ experimental method is proposed to observe and record the bending de-formation process of the double-layer cantilever electrode in the electrochemical cycle in real time, and the corresponding mechanical model is established to obtain the mechanical properties parameters such as stress, strain and Young’s modulus of the silicon carbide composite electrode from the experimental point of view. These results will help to develop more stable and durable high-capacity lithium-ion batteries. Based on the mechanical model and in-situ measurement sys-tem, the charging rate was adjusted and the electrochemical cycle was carried out. The effects of different rates on the mechanical properties of the electrode were analyzed and discussed. For the 0.1C charging rate, the above calculation results will continue to be used. Considering that the rapid charging will cause the uneven distribution of lithium ions concentration c in the thickness direc-tion, it is assumed that the lithium ions concentration has a concentration gradient in the thickness direction, and a physical model considering the concentration gradient is further proposed. Under fast charging, the distribution of lithium ions in the active layer is uneven, and the local stress and strain are quite different. The fluctuation of the curvature change during the charging process is large, while the distribution of lithium ions under slow charging is relatively uniform. As the degree of lithiation increases, the bending deformation of the electrode increases. Under the same charge and discharge state, the electrode deformation caused by fast charge is greater than that caused by slow charge. Slow charge can keep the electrode in good structure.