Lin Huiwen, Noguchi Hidenori, Uosaki Kohei
Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan.
Center for Green Research on Energy and Environmental Materials and Global Research Center for Environment and Energy Based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS), Namiki, Tsukuba 305-0044, Japan.
ACS Omega. 2020 Jan 31;5(5):2081-2087. doi: 10.1021/acsomega.9b01665. eCollection 2020 Feb 11.
As one of the major impurities in the organic electrolyte, HF can react with the alkali components in the solid electrolyte interphase (SEI), such as lithium alkoxide and lithium carbonate, to form more LiF-rich SEI. Here, the effects of HF on the lithiation behavior of the single crystal Si(111) anode were studied using scanning electron microscopy, soft X-ray emission spectroscopy, and windowless energy-dispersive X-ray spectroscopy. When the Li-Si alloy is formed in 1.0 M LiPF in the propylene carbonate solvent, it has a layered structure that contained the first layer of crystalline LiSi (c-LiSi) alloy pyramids, the second layer of amorphous LiSi (a-LiSi) alloy, and a third layer of Li-diffused Li Si alloy. When the more concentrated HF is in the electrolyte solution, less amount of the c-LiSi alloy is formed in the first layer. It suggests that the Si lithiation can form only amorphous Li Si alloy relative to the components in the electrolytes. The study also explains why only amorphous Li Si alloy formation was observed in some previous studies.
作为有机电解质中的主要杂质之一，HF可与固体电解质界面（SEI）中的碱性成分（如锂醇盐和碳酸锂）发生反应，形成富含更多LiF的SEI。在此，利用扫描电子显微镜、软X射线发射光谱和无窗口能量色散X射线光谱研究了HF对单晶Si(111)负极锂化行为的影响。当在碳酸丙烯酯溶剂中的1.0 M LiPF 6中形成Li-Si合金时，它具有层状结构，包含第一层结晶LiSi（c-LiSi）合金金字塔、第二层非晶LiSi（a-LiSi）合金和第三层Li扩散的Li x Si合金。当电解质溶液中HF浓度更高时，第一层中形成的c-LiSi合金量更少。这表明相对于电解质中的成分，Si锂化只能形成非晶Li x Si合金。该研究还解释了为什么在一些先前的研究中只观察到非晶Li x Si合金的形成。
