Probing the electrode-solution interfaces in rechargeable batteries by sum-frequency generation spectroscopy.

An in-depth understanding of the electrode–electrolyte interaction and electrochemical reactions at the electrode–solution interfaces in rechargeable batteries is essential to develop novel electrolytes and electrode materials with high performance. In this perspective, we highlight the advantages of the interface-specific sum-frequency generation (SFG) spectroscopy on the studies of the electrode–solution interface for the Li-ion and Li—O2 batteries. The SFG studies in probing solvent adsorption structures and solid-electrolyte interphase formation for the Li-ion battery are briefly reviewed. Recent progress on the SFG study of the oxygen reaction mechanisms and stability of the electrolyte in the Li—O2 battery is also discussed. Finally, we present the current perspective and future directions in the SFG studies on the electrode–electrolyte interfaces toward providing deeper insight into the mechanisms of discharging/charging and parasitic reactions in novel rechargeable battery systems.