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

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.