In situ surface-enhanced Raman spectroelectrochemistry reveals the molecular conformation of electrolyte additives in Li-ion batteries

We report the mechanism of rhodamine B (RhB) acting as an electrolyte additive in Li/graphite cells. We show that the cycle performance and rate capability of graphite are enhanced in carbonate-based electrolytes containing 0.2 wt% RhB. By using silica-encapsulated Au nanoparticles, in situ surface-enhanced Raman spectroscopy (SERS) is applied to study the graphite/electrolyte interface. We find that the adsorption orientation of RhB molecules on the surface of graphite can be modulated by the applied potential: vertical adsorption at higher potentials while horizontal adsorption takes place at lower potentials. This behavior effectively suppresses the electrolyte solvent decomposition, as well as electrode corrosion while improving the Li+ diffusion. This work shows that SERS is a powerful tool for interfacial analysis of battery systems and provides new ideas for rational design of electrolyte additives.

Automated summary

This study investigates the mechanism of Rhodamine B (RhB) as an electrolyte additive in Li/graphite cells. Through in situ surface-enhanced Raman spectroscopy (SERS), researchers found that the adsorption orientation of RhB molecules on the surface of graphite can be modulated by the applied potential, improving the cycle performance and rate capability of the battery while suppressing electrolyte solvent decomposition and electrode corrosion. The findings suggest that SERS is a powerful tool for interfacial analysis of battery systems and offer new insights for rational design of electrolyte additives.