In situ Raman spectroscopy of carbon-coated ZnFe₂O₄anode material in Li-ion batteries – investigation of SEI growth

Abstract

The (de)lithiation process of carbon-coated ZnFe2O4 has been investigated by in situ Raman spectroscopy. Solid electrolyte interphase (SEI) products were detected. Their detection may result from a temporary surface enhancement Raman effect from Zn nanoparticles formed in the conversion reaction at a potential that coincides with SEI formation.

In‐Situ Electrochemical SHINERS Investigation of SEI Composition on Carbon‐Coated Zn0.9Fe0.1O Anode for Lithium‐Ion Batteries

“…As seen in Figure , the D band for the carbon coating is slightly shifted to higher wavenumbers when compared to those for carbon black and it has a shoulder centred at 1180 cm −1 . There is also a difference in the values of the full‐width at half maximum (FWHM) for both carbon types as shown in Table ; therefore, it is possible to distinguish the signal from the coating and the carbon black as previously reported for carbon‐coated ZnFe 2 O 4 (ZnFe 2 O 4 −C) material …”

“…The Raman spectrum of Zn 0.9 Fe 0.1 O is in good agreement with these reports. The peaks at 920 and 1110 cm −1 in Figure (i) are overtone bands . The absence of these bands or other related to Fe‐doped material indicates that the carbon coating is homogenous in Zn 0.9 Fe 0.1 O−C …”

“…SEI growth on carbon‐coated ZnFe 2 O 4 (ZnFe 2 O 4 −C) was previously investigated by in‐situ Raman spectroscopy . Vibrational modes associated with polyethylene oxide (PEO) and lithium alkyl carbonate species were detected spectroscopically during the discharge of ZnFe 2 O 4 −C in an ethylene carbonate and dimethyl carbonate 1 : 1 w/w, 1 M LiPF 6 electrolyte.…”

“…Vibrational modes associated with polyethylene oxide (PEO) and lithium alkyl carbonate species were detected spectroscopically during the discharge of ZnFe 2 O 4 −C in an ethylene carbonate and dimethyl carbonate 1 : 1 w/w, 1 M LiPF 6 electrolyte. The detection of these species by Raman spectroscopy was associated with a temporary surface enhancement of the Raman signal from metallic zinc nanoparticles that resulted from the reduction of ZnFe 2 O 4 during the conversion reaction at a potential that coincided with SEI formation . The SEI formed on ZnFe 2 O 4 −C was also investigated by X‐ray based techniques (e. g., XAS and XPS) .…”

Applications of Conventional Vibrational Spectroscopic Methods for Batteries Beyond Li‐Ion

“…The advance of in situ subsurface and surface probes that can explore the SEI significantly helps understand and distinguish the complicated mechanisms related to the SEI formation and other redox processes. For example, the detection of SEI evolving signals from utilizing the SERS effect induced by metal particles formed during conversion reactions, Hardwick and co‐workers investigated the first discharge–charge cycle of the carbon‐coated ZnFe 2 O 4 (ZFO–C) composite by in situ Raman spectroscopy in 2016 . It was found that lithiation took place not only in ZFO nanoparticles, but also in the carbon coating.…”