Understanding the fundamental factors that drives the ion-solvation structure and transport are key towards design of high performance stable battery electrolytes. Solvation and desolvation mechansims are critical for interfacial charge transfer process across the solid-liquid interphase and often play an important role towards determining the composition and the stability of the solid electrolyte interphase (SEI). The first part of the talk will focus on the study of Li+ salt solvation structure in the aprotic solution in immediate vicinity (&lt; 20 nm) of the solid-liquid interface using the surface-enhanced Raman spectroscopy (SERS) from a gold monolayer. The plasmonic coupling between Au nanoparticles (Au NPs) produces strong enhancement of electromagnetic field in the inter-Au NP gap, leading to a 5-fold increase in Raman intensity for electrolyte components and their mixtures, including lithium hexafluorophosphate (LiPF6), fluoroethylene carbonate (FEC), ethylene carbonate (EC) and diethyl carbonate (DEC). Detailed analysis on the solvation-related SERS bands indicates that competitive solvation exists between EC/Li+ and DEC/Li+ at the solid liquid interface. The second part of the talk will report new results on development of tip enhanced Raman spectroscopy (TERS) for studying the SEI on model silicon surface. TERS has unique capability of mapping surface SEI composition at nanoscale with an enhancement factor close to 104 compared to micro-Raman revealing the nanoscale heterogeneity of the SEI.

Investigating lithium-ion solvation structure and solid electrolyte interphase using multiscale vibrational spectroscopic and imaging techniques

255th National Meeting (2018)

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