Probing Electrode-Electrolyte Interfaces Using Nano-Gap Surface-Enhanced Raman Spectroscopy and Imaging

Conference · Sun Apr 01 00:00:00 EDT 2018

DOI:https://doi.org/10.1149/MA2018-01/45/2629· OSTI ID:1474644

Yang, Guang  ^[1]; Ivanov, Ilia N.  ^[1]; Ruther, Rose  ^[1]; Sacci, Robert  ^[1]; Subjakova, Veronika ^[2]; Hallinan, Daniel T. ^[3]; Nanda, Jagjit  ^[1]

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1. ORNL
2. Comenius University, Bratislava, Slovakia
3. Florida A&M University-Florida State University (FAMU-FSU)

Performance of portable electronic devices and electric vehicles is currently limited by the energy density, lifetime and safety of lithium rechargeable batteries. Overcoming those limitations requires in-depth understanding of the electrode-electrolyte interfaces. Surface-enhanced Raman spectroscopy (SERS) can provide a critical component to this effort as an in situ technique with ultrahigh surface sensitivity that provides quantitative molecular specificity. SERS relies on local electromagnetic field amplification generated by surface plasmon resonance (SPR) at the surface of metal nanoparticles (NPs) with sub-wavelength dimensions. The most significant Raman enhancements have been observed when the local SPRs of multiple NPs interact. This occurs when the NPs are in close proximity (less than 10 nm), which could be achieved in ordered NP monolayers if they could be assembled reproducibly. Methods to assemble gold NPs into large area (cm2) monolayers will be presented. The interparticle gap can be tuned between 1 and 4 nm by using surface ligands of different sizes. The Au NP monolayers exhibit high SERS sensitivity (enhancement factor greater than 107). This allows for the measurement of electrolyte components across a broad range of concentrations. Components include lithium hexafluorophosphate (LiPF6), fluoroethylene carbonate (FEC), ethylene carbonate (EC) and diethyl carbonate (DEC). The investigation of solutions of LiPF6 in EC + DEC binary solvents using SERS allows for the determination of the solvent coordination numbers, which range from 2 to 5. This result is in sharp contrast to the bulk values calculated from infrared spectroscopy, which range from 3 to 7. Numerical simulations show that the electromagnetic field is concentrated in the nanogap, indicating the information of the aprotic electrolyte solution structures is obtained from the immediately adjacent area of the solid substrate. Our findings facilitate a better understanding of the structure of solvated ions in close proximity to the electrode surface.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1474644
• Resource Relation: Journal Volume: MA2018-01; Journal Issue: 45; Conference: 233rd ECS Meeting - Seattle, Washington, United States of America - 5/13/2018 4:00:00 AM-5/17/2018 4:00:00 AM
• Country of Publication: United States
• Language: English