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Abstract：
Lithium fluoride (LiF) is a ubiquitous component in the solid electrolyte interphase (SEI) layer in Li-ion batteries. However, its nanoscale structure, morphology, and topology, important factors for understanding LiF and SEI film functionality, including electrode passivity, are often unknown due to limitations in spatial resolution of common characterization techniques. Ultrabroadband near-field synchrotron infrared nanospectroscopy (SINS) enables such detection and mapping of LiF in SEI layers in the far-infrared region down to ca. 322 cm-1 with a nanoscale spatial resolution of ca. 20 nm. The surface sensitivity of SINS and the large infrared absorption cross section of LiF, which can support local surface phonons under certain circumstances, enabled characterization of model LiF samples of varying structure, thickness, surface roughness, and degree of crystallinity, as confirmed by atomic force microscopy, attenuated total reflectance FTIR, SINS, X-ray photoelectron spectroscopy, high-angle annular dark-field, and scanning transmission electron microscopy. Enabled by this approach, LiF within SEI films formed on Cu, Si, and metallic glass Si40Al50Fe10 electrodes was detected and characterized. The nanoscale morphologies and topologies of LiF in these SEI layers were evaluated to gain insights into LiF nucleation, growth, and the resulting nuances in the electrode surface passivity.
摘要：
氟化锂(LiF)是锂离子电池中固体电解质界面(SEI)层中普遍存在的组分。然而,它的纳米级结构，形态学,和拓扑，了解LiF和SEI薄膜功能的重要因素，包括电极钝化，由于常见表征技术的空间分辨率限制，通常是未知的。超宽带近场同步加速器红外纳米光谱（SINS）可以在远红外区域中对SEI层中的LiF进行这种检测和映射，直至322cm-1，纳米级空间分辨率约为20nm。SINS的表面灵敏度和LiF的大红外吸收截面，在某些情况下可以支持局部表面声子，能够表征不同结构的LiF模型样品，厚度,表面粗糙度,和结晶度，正如原子力显微镜所证实的，衰减全反射FTIR，罪过,X射线光电子能谱,高角度环形暗场，和扫描透射电子显微镜。通过这种方法启用，在Cu上形成的SEI膜内的LiF，Si,并对金属玻璃Si40Al50Fe10电极进行了检测和表征。评估了这些SEI层中LiF的纳米级形态和拓扑结构，以获得对LiF成核的见解，增长,以及由此产生的电极表面钝化的细微差别。
