Interface Behavior of Electrolyte/Quinone Organic Active Material in Battery Operation by Operando Surface-Enhanced Raman Spectroscopy

Abstract

To elucidate the microscopic charge/discharge (delithiation/lithiation) mechanism at the interface of the electrolyte and organic cathode active material in the lithium-ion battery, we prepared a self-assembled monolayer (SAM) electrode of 1,4-benzoquinone terminated dihexyl disulfide (BQ-C6) on Au(111). An electrochemical setup with the BQ-C6 SAM as a working electrode and 1 M lithium bis­(trifluoromethanesulfonyl)­imide (Li-TFSI)/triethyleneglycol dimethylether (G3) as the electrolyte was used. We adopted the shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) method to obtain sufficient Raman signal of SAM for operando Raman spectroscopy measurements by the enhancement with ∼100 nm diameter Au particles coated with SiO2 shell (average thickness = 2 nm). By this method, we succeeded in acquiring the Raman signal of the molecular monolayer on the model electrode simulating the interface between the electrolyte and the organic active material. In the cyclic voltammogram, two peaks were observed during the reduction reaction (lithiation), whereas only one peak was detected in the course of the oxidation process (delithiation). Simultaneous operando SHINERS showed a two-step spectral shape change in lithiation and coinciding (or simultaneous) one-step recovery during delithiation to match cyclic voltammetry behavior. The results indicate an asymmetric lithiation/delithiation mechanism.

In Situ Surface-Enhanced Raman Spectroscopy on Organic Mixed Ionic-Electronic Conductors: Tracking Dynamic Doping in Light-Emitting Electrochemical Cells

“…Raman spectroscopy stands out as a widely used nondestructive spectroelectrochemical tool for tracking doping mechanisms and studying electrochemical processes in solid-state electrochemical devices. It has the capability to perform structural analyses ranging from the bulk electrolyte to the diffusion layer within the EDL, all the way to surface-adsorbed molecules and electrode materials. ,,, Surface-enhanced Raman spectroscopy (SERS) leverages electric field enhancement via surface plasmon resonance to detect subtle signals from molecules at both the electrode surface and the electrode–electrolyte interface in electrochemical systems and excels at capturing weak signals in these environments . The electric field enhancement is the strongest at “hot spots” formed between closely spaced particles or at sharp features of individual particles, and analytes located at these features account for a large part of the total signal .…”

“… 34 , 36 , 42 , 43 Surface-enhanced Raman spectroscopy (SERS) leverages electric field enhancement via surface plasmon resonance to detect subtle signals from molecules at both the electrode surface and the electrode–electrolyte interface in electrochemical systems and excels at capturing weak signals in these environments. 43 The electric field enhancement is the strongest at “hot spots” formed between closely spaced particles or at sharp features of individual particles, and analytes located at these features account for a large part of the total signal. 44 The increased sensitivity provided by SERS makes this a preferred method for time-resolved studies of OMIECs aimed at improving our understanding of dynamic changes under operation.…”

P-Doped Cotton Stalk Carbon for High-Performance Lithium-Ion Batteries and Lithium–Sulfur Batteries

“…Advanced secondary batteries can meet large-scale energy storage needs, such as lithium-ion batteries (LIBs) , and lithium–sulfur (Li–S) batteries, − which can store and utilize clean energy . LIB is one of the best-performing batteries, and it has been successfully applied to portable electronic products, such as mobile communication equipment, notebook computers, and digital cameras. , Li–S battery is one of the new secondary batteries, because S demonstrates a remarkable theoretical capacity (1675 mAh g –1 ). , …”