posted on 2022-04-04, 20:14authored byZhuo 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 CO
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.