Search

The solid-electrolyte interphase (SEI) plays crucial roles for the reversible operation of lithium metal batteries. However, fundamental understanding of the mechanisms of SEI formation and evolution is still limited. Herein, we develop a depth-sensitive plasmon-enhanced Raman spectroscopy (DS-PERS) method to enable in-situ and nondestructive characterization of the nanostructure and chemistry of SEI, based on synergistic enhancements of localized surface plasmons from nanostructured Cu, shell-isolated Au nanoparticles and Li deposits at different depths. We monitor the sequential formation of SEI in both ether-based and carbonate-based dual-salt electrolytes on a Cu current collector and then on freshly deposited Li, with dramatic chemical reconstruction. The molecular-level insights from the DS-PERS study unravel the profound influences of Li in modifying SEI formation and in turn the roles of SEI in regulating the Li-ion desolvation and the subsequent Li deposition at SEI-coupled interfaces. Last, we develop a cycling protocol that promotes a favorable direct SEI formation route, which significantly enhances the performance of anode-free Li metal batteries. The solid-electrolyte interphase is crucial for most batteries, but its characterization is challenging. Here, authors develop a depth-sensitive plasmon-enhanced Raman spectroscopy method to enable in-situ and nondestructive resolving of its structure and chemistry as well as formation mechanisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au@RuO x core–shell nanostructures are fabricated to amplify the Raman signals. • Electroreduction of RuO x is in-situ studied using the borrowing SERS strategy. • Direct evidences of OH intermediate are obtained during RuO x electroreduction. • A two-step molecular pathway is proposed for RuO 2 electroreduction. RuO 2 is one of the most promising catalysts for oxygen evolution reaction (OER), a key reaction in water electrolysis. However, the fundamental insights about the structural evolution of RuO 2 under different electrochemical environments remain unclear. Herein, the molecular reaction pathways of the electroreduction of RuO x in alkaline and neutral conditions are identified using in-situ electrochemical surface-enhanced Raman spectroscopy. Au@RuO 2 core–shell nanostructures are fabricated to amplify the Raman signals of species adsorbed on RuO x surfaces. Using such core–shell nanostructures, direct spectroscopic evidences of OH intermediate during the RuO 2 electroreduction process are obtained, which is further confirmed by D 2 O isotopic substitution experiments. A molecular pathway that RuO 2 is reduced to Ru through a two-step reduction process has been proposed. This work provides insightful information on the structural evolution of RuO x with electrochemical environments. [ABSTRACT FROM AUTHOR]