Nano-FTIR Spectroscopy of the Solid Electrolyte Interphase Layer on a Thin-Film Silicon Li-Ion Anode

Abstract

Si anodes for Li-ion batteries are notorious for their large volume expansion during lithiation and the corresponding detrimental effects on cycle life. However, calendar life is the primary roadblock for widespread adoption. During calendar life aging, the main origin of impedance increase and capacity fade is attributed to the instability of the solid electrolyte interphase (SEI). In this work, we use ex situ nano-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy to characterize the structure and composition of the SEI layer on amorphous Si thin films after an accelerated calendar aging protocol. The characterization of the SEI on non-washed and washed electrodes shows that brief washing in dimethyl carbonate results in large changes to the film chemistry and topography. Detailed examination of the non-washed electrodes during the first lithiation and after an accelerated calendar aging protocol reveals that PF6 – and its decomposition products tend to accumulate in the SEI due to the preferential transport of PF6 – ions through polyethylene oxide-like species in the organic part of the SEI layer. This work demonstrates the importance of evaluating the SEI layer in its intrinsic, undisturbed form and new strategies to improve the passivation of the SEI layer are proposed.

The Effect of the SEI Layer Mechanical Deformation on the Passivity of a Si Anode in Organic Carbonate Electrolytes

“…Ex situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) measurements were conducted to characterize the vibrational spectra of electrodes over microscale surface areas. Moreover, in order to characterize the electrode surface morphology, structure, and chemical composition at nanoscale resolution, ex situ atomic force microscopy (AFM) based near-field Fourier transform infrared nanospectroscopy (nano-FTIR) measurements were conducted; , a method recently used to probe electrochemical surfaces and interfaces. , Both tools were enclosed within a N 2 -filled glovebox, and further technical details, including how nano-FTIR breaks the diffraction limit, can be found in the Methods section.…”

FTIR spectrum analysis to predict the crystalline and amorphous phases of hydroxyapatite: a comparison of vibrational motion to reflection

“…34 FTIR analysis is a very popular instrument for the identication of functional groups in organic compounds but sometimes inorganic samples can be identied using this instrument. [35][36][37] For synthesized hydroxyapatite (Hap), two peaks appeared near 563 and 599 cm −1 wavenumber due to the bending vibration for all the types of Haps. But, there was a difference in the intensity of the peaks when a variation in temperature was maintained.…”

Promoting Homogeneous Zinc‐Ion Transfer Through Preferential Ion Coordination Effect in Gel Electrolyte for Stable Zinc Metal Batteries

“…Concurrently, an increase in electrolyte concentration from 2 to 5 m affects the number of S═O bonds in poly(SBMA) displaying an asymmetrical vibration mode, resulting in a reduced intensity of the sulfonate peak at 1170 cm −1 . [ 48 ] This occurs due to the intensified interaction between Zn 2+ and sulfonate with increasing electrolyte concentration, thereby supporting the distinct behavior of ZGPE under different concentrations.…”