American Chemical Society
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Observing Two-Dimensional Spontaneous Reaction between a Silicon Electrode and a LiPF6‑Based Electrolyte In Situ and in Real Time

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journal contribution
posted on 2022-04-04, 20:14 authored by Zhuo Wang, Junjun Tan, Zhe Yang, Yi Luo, Shuji Ye
Two-dimensional spontaneous reactions between an electrode and an electrolyte are very important for the formation of a solid electrolyte interphase (SEI) but difficult to study because studying such reactions requires surface/interface sensitive techniques with sufficiently structural and temporal resolutions. In this study, we have applied femtosecond broadband sum-frequency generation vibrational spectroscopy (SFG-VS) to investigate the interaction between a silicon electrode and a LiPF6-based diethyl carbonate electrolyte solution in situ and in real time. We found that two kinds of diethyl carbonate species are present on the silicon surface and their CO stretching aligns in opposite directions. Intrinsically spontaneous chemical reactions between silicon electrodes and a LiPF6 electrolyte solution are observed. The reactions generate silicon hydride and cause corrosion of the silicon electrodes. Coating of the silicon surface with a poly­(vinyl alcohol) layer can effectively retard and attenuate these reactions. This work demonstrates that SFG-VS can provide a unique and powerful state-of-the-art tool for elucidating the molecular mechanisms of SEI formation.