关键词: 固态电解质界面相, 原位SERS, 负极界面, 锂电池

Abstract:

The solid-electrolyte interphase (SEI) plays a key role in anodes for rechargeable lithium-based battery technologies. However, a thorough understanding in the mechanisms of SEI formation and evolution remains a major challenge, hindering the rapid development and wide applications of Li-based batteries. Here, we devise a borrowing surface-enhanced Raman scattering (SERS) activity strategy by utilizing a size optimized Ag nanosubstrate to in-situ monitor the formation and evolution of SEI, as well as its structure and chemistry in an ethylene carbonate-based electrolyte. To ensure a reliable in-situ SERS investigation, we designed a strict air-tight Raman cell with a three-electrode configuration. Based on the potential-dependent spectroscopic information, we revealed that the SEI formed in an EC-based electrolyte presents a double-layer structure, comprising a thin inorganic inner layer and an organic-rich outer layer. We also identified that LEMC, rather than LEDC, is the major component of EC reduction, and the critical role of metallic Li in the formation of stable SEI is preliminary explored. Nevertheless, identifying the SEI compositions is only feasible before Li deposition on the Ag surface. After the formation of Li-Ag alloys, the subsequent evolution of SEI could not be detected due to the change in the dielectric constant of Ag after the lithiation. Our work provides a real-time spectroscopic method for investigating interfacial processes of anodes, which is beneficial to the understanding of SEI formation and evolution and thus provides guidance for the development of rationally designed SEI in Li-based batteries.

Key words: solid-electrolyte interphase, in-situ SERS, anodes, lithium-based batteries