单晶硅片负极界面形貌的原位AFM探测

In situ AFM Investigation of Interfacial Morphology of Single Crystal Silicon Wafer Anode

利用原子力显微镜原位研究单晶硅片负极在首次充放电循环中的界面形貌变化。硅负极表面固体电解质界面(SEI)膜的形成过程为:初始SEI膜从1.5 V开始形成,在1.25–1.0 V之间生长快速,0.6 V左右生长缓慢。初始SEI膜具有层状结构的特征,表层薄膜较软,下层呈颗粒状,机械稳定性较好。在锂化电位下,硅负极表面的单晶结构逐渐变得颗粒化,发生不可逆的结构变化。经过首个充放电循环后,硅负极表面被厚度不均一的SEI膜所覆盖,SEI膜的厚度大约为10–40 nm。

The interfacial morphology of a single crystal Si wafer anode during the first discharging-charging cycle was investigated using in situ atomic force microscopy （AFM）. The solid-electrolyte interphase （SEI） began to grow from 1.5 V, developing rapidly between 1.25 and 1.0 V, and slowed down after 0.6 V. The morphology suggested that the SEI had a layered structure. The outer layer of SEI was soft and easy to be scraped off during the AFM tip scanning. The underlayer of SEI had granular features. During the lithiation process, the Si surface became grainy because of the insertion of Li ions. After the first cycle, the Si surface was completely covered by inhomogeneous SEI. The thickness of the SEI was approximately 10-40 nm.