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.

Carbon‐coated Zn0.9Fe0.1O is a promising anode material for lithium‐ion batteries with good cycling performance and a theoretical specific capacity of 966 mAh g−1, as a result of the combined conversion‐alloying reaction during lithiation. The solid electrolyte interphase (SEI) formed on this electrode was investigated by in‐situ Raman spectroscopy and in‐situ shell‐isolated nanoparticles for enhanced Raman spectroscopy (SHINERS) during the first discharge/charge cycle. The spectra collected via in‐situ Raman spectroscopy showed that the carbon coating is also (de)lithiated and it remains mechanically intact after the first complete cycle. There was no evidence of peaks related to the SEI due to the absence of surface enhancement of the Raman effect in this material, as was previously observed for carbon‐coated ZnFe2O4. However, bands assigned to polyethylene oxide species (PEO) and different lithium alkyl carbonate compounds (i. e., ROCO2Li, ROLi and RCOOLi) from the SEI were observed via SHINERS. The enhancement of the Raman effect by Au−SiO2 core‐shell nanoparticles allows the detection of surface films at potentials at which the SEI is formed and their chemical composition, which is not possible otherwise due to the intrinsically weak scattering process. Therefore, these results show that the SHINERS technique is a powerful method to investigate the structural evolution of the electrode material with potential and interfacial reactions on lithium‐ion batteries.

A critical and detailed assessment of using Shell Isolated Nanoparticles for Enhanced Raman Spectroscopy (SHINERS) on different electrode substrates was carried out, providing relative enhancement factors, as well as an evaluation of the distribution of shell-isolated nanoparticles upon the electrode surfaces. The chemical makeup of surface layers formed upon lithium metal electrodes and the mechanism of the oxygen reduction reaction on carbon substrates relevant to lithium-oxygen cells are studied with the employment of the SHINERS technique. SHINERS enhanced the Raman signal at these surfaces showing a predominant LiO based layer on lithium metal in a variety of electrolytes. The formation of LiO and LiO, as well as degradation reactions forming LiCO, upon planar carbon electrode interfaces and upon composite carbon black electrodes were followed under potential control during the reduction of oxygen in a non-aqueous electrolyte based on dimethyl sulfoxide.

Kerr gated Raman spectroscopy is demonstrated as an effective technique for the measurement of highly fluorescing Li-ion battery electrolyte materials.