Surface Coating Mediated Swelling and Fracture of Silicon Nanowires during Lithiation
Surface Coating Mediated Swelling and Fracture of Silicon Nanowires during Lithiation
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DOI：
10.1021/nn503564r
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发表时间：
2014-09-01
期刊：
影响因子：
17.1
通讯作者：
Vlad, Alexandru
中科院分区：
文献类型：
--
作者：
Sandu, Georgiana;Brassart, Laurence;Vlad, Alexandru
硅阳极的表面钝化是开发可靠、高容量锂离子电池的一种有吸引力的设计策略。然而，涂层的结构稳定性及其对锂化过程的影响仍不清楚。在此，我们表明表面涂层介导了晶体硅纳米柱初始锂化过程中的膨胀动力学和断裂模式。我们选择保形镀镍硅架构作为模型系统。实验结果根据化学力学模型进行解释。根据涂层厚度和硅纳米柱直径，已发现明显不同的膨胀和断裂状态。具有相对较薄涂层的纳米柱表现出与原始纳米柱相似的各向异性膨胀，但具有不同的首选断裂位点。随着涂层厚度的增加，该机制变得各向同性，一条随机定向的纵向裂纹将核壳结构拉开。裂纹柱的形态类似于基板上薄膜电极的形态，更适合环锂化而不会断裂。这里提供的知识有助于阐明涂层纳米硅电极的循环结果，并进一步提出通过适当控制锂化和断裂来获得更好性能电极的设计规则。
Surface passivation of silicon anodes is an appealing design strategy for the development of reliable, high-capacity lithium-ion batteries. However, the structural stability of the coating layer and its influence on the lithiation process remain largely unclear. Herein, we show that surface coating mediates the swelling dynamics and the fracture pattern during initial lithiation of crystalline silicon nanopillars. We choose conformally nickel coated silicon architectures as a model system. Experimental findings are interpreted based on a chemomechanical model. Markedly different swelling and fracture regimes have been identified, depending on the coating thickness and silicon nanopillar diameter. Nanopillars with relatively thin coating display anisotropic swelling similar to pristine nanopillars, but with different preferred fracture sites. As the coating thickness increases, the mechanisms become isotropic, with one randomly oriented longitudinal crack that unzips the core shell structure. The morphology of cracked pillars resembles that of a thin-film electrode on a substrate, which is more amenable to cydic lithiation without fracture. The knowledge provided here helps clarify the cycling results of coated nanosilicon electrodes and further suggests design rules for better performance electrodes through proper control of the lithiation and fracture.