Zheng Yijing, Yin Danni, Seifert Hans Jürgen, Pfleging Wilhelm
Institute for Applied Materials-Applied Materials Physics (IAM-AWP), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
Nanomaterials (Basel). 2021 Dec 31;12(1):140. doi: 10.3390/nano12010140.
The 3D battery concept applied on silicon-graphite electrodes (Si/C) has revealed a significant improvement of battery performances, including high-rate capability, cycle stability, and cell lifetime. 3D architectures provide free spaces for volume expansion as well as additional lithium diffusion pathways into the electrodes. Therefore, the cell degradation induced by the volume change of silicon as active material can be significantly reduced, and the high-rate capability can be achieved. In order to better understand the impact of 3D electrode architectures on rate capability and degradation process of the thick film silicon-graphite electrodes, we applied laser-induced breakdown spectroscopy (LIBS). A calibration curve was established that enables the quantitative determination of the elemental concentrations in the electrodes. The structured silicon-graphite electrode, which was lithiated by 1C, revealed a homogeneous lithium distribution within the entire electrode. In contrast, a lithium concentration gradient was observed on the unstructured electrode. The lithium concentration was reduced gradually from the top to the button of the electrode, which indicated an inhibited diffusion kinetic at high C-rates. In addition, the LIBS applied on a model electrode with micropillars revealed that the lithium-ions principally diffused along the contour of laser-generated structures into the electrodes at elevated C-rates. The rate capability and electrochemical degradation observed in lithium-ion cells can be correlated to lithium concentration profiles in the electrodes measured by LIBS.
应用于硅石墨电极（Si/C）的3D电池概念已显示出电池性能的显著提升，包括高倍率性能、循环稳定性和电池寿命。3D结构为体积膨胀提供了自由空间，并为锂离子扩散到电极中提供了额外的路径。因此，由作为活性材料的硅的体积变化引起的电池退化可显著降低，并且可实现高倍率性能。为了更好地理解3D电极结构对厚膜硅石墨电极的倍率性能和退化过程的影响，我们应用了激光诱导击穿光谱法（LIBS）。建立了一条校准曲线，能够定量测定电极中的元素浓度。以1C倍率进行锂化的结构化硅石墨电极在整个电极内显示出均匀的锂分布。相比之下，在非结构化电极上观察到了锂浓度梯度。锂浓度从电极顶部到底部逐渐降低，这表明在高C倍率下扩散动力学受到抑制。此外，应用于带有微柱的模型电极上的LIBS显示，在升高的C倍率下，锂离子主要沿着激光产生的结构轮廓扩散到电极中。在锂离子电池中观察到的倍率性能和电化学退化可与通过LIBS测量的电极中的锂浓度分布相关联。
