The well-known solid electrolyte interphase (SEI) film formed on the Li anodes surface gains paramount research interest because of its importance to the electrochemical performances of Li-based batteries. However, despite considerable research in the past few decades, the accurate understanding of the thin and non-uniform SEI interfaces is still a puzzle to be solved. Having extremely high sensitivity for analyzing chemical composition and structure of electrode/electrolyte interfaces (EEL), surface enhanced Raman spectroscopy (SERS) has been employed to characterize the composition and the microstructure of SEI film from time to time. However, subject to the rather limited substrates, these work were forced to conduct on the SERS-active metals. The introduction of extra active metals may have impact on the electrochemical behavior of Li anodes, and the obtained information for SEI are usually partial and oversimplified. Shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS), which yield giant Raman signals from unperturbed surfaces of general materials, provide a great opportunity to study the complex Li surfaces. Nevertheless, although a few of recent researches has adopted this new technique to investigate the interface processes on Si or other SERS-inactive electrodes, the actual Li EEL has not been involved and the evolution of SEI on Li surface during charge-discharge process is still not well performed and followed. Herein, we report an in situ SHINERS method for monitoring the formation process of SEI film on Li anode surfaces in DOL-based electrolyte. We coated SERS-active Ag nanoparticles with an inert and thin Al2O3 shell, and spread them as a Raman signal amplifier over Li surface. First, the SEI on Li anode formed by soaking in electrolyte for different periods of time was detected. Apart from the characteristic bands associated with the electrolyte, several bands arisen upon extending soaking time could be attributed to the vibration of LiOH, Li3N, Li2SO2CF3 and ROLi, respectively, which are the main components of SEI film. Also, the SEI formed during the Li plating process was studied. Obviously, the bands of LiOH, Li3N, LiCF3, Li2S2O4 and ROLi can be detected upon extend of plating time. In brief, by utilizing this method, SEI compositions on Li anodes can be easily identified. This work demonstrates that in situ SHINERS can serve as a powerful means for investigation of EEL in Li-based batteries.

In situ SHINERS investigation of lithium electrode/electrolyte interfaces

254th National Meeting (2017)

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