In Situ Atomic Force Microscopic Studies of LiFSI-[Py1,4]FSI Interfacial Nanostructure on Au(111): Solid Electrolyte Interphase and Lithium Underpotential Deposition

• Published in: Journal of physical chemistry. C Vol. 125; no. 49; pp. 27140 - 27147
• Main Authors: Liu, Shikun, Cui, Tong, Carstens, Timo, Zhao, Jiupeng, Borisenko, Natalia, Liu, Xiaoxu, Liu, Zhen, Li, Yao, Endres, Frank
• Format: Journal Article
• Language: English
• Published: American Chemical Society 16.12.2021
• Subjects: C: Energy Conversion and Storage
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.1c09340

In this paper, the structure of the LiFSI-[Py1,4]­FSI interface on Au(111) was investigated using in situ atomic force microscopy and cyclic voltammetry. Raman and IR vibrational spectroscopy was applied to evaluate the coordination of Li+ ions with the FSI– anion. It was found that [Li­(FSI)3]2– species are present in the solutions. The solvation layer number and the forces decrease at higher concentration of Li+ ions. Therefore, the driving force, which is required for the [Li­(FSI)3]2– species to pass through the solvation layer to reach the electrode surface, is lowered. This increases the onset potentials of the SEI layer formation and lithium underpotential deposition (Li-UPD) at high Li+ concentrations. It was found that the onset potentials are −0.8, −0.7, −0.6, and −0.4 V for the Li-UPD and −2.0, −1.6, −1.4, and −1.3 V for the SEI layer formation, vs the Pt-(quasi)­reference electrode, corresponding to Li+ concentrations of 0.1, 0.25, 0.5, and 1 M, respectively.