Vibrational Spectroscopy Insight into the Electrode|electrolyte Interface/Interphase in Lithium Batteries

Abstract

Lithium‐ion batteries (LIBs) have transformed the use of mobile electronics and storage technologies. Alongside advances in materials, an in‐depth understanding of the interfacial phenomena and interphase formation mechanisms in LIBs is crucial. Interphases are widely recognized as the most important and the least understood components of LIBs and play a direct role in defining cell performance, cyclability, and safety. This article presents a review of recent developments in vibrational spectroscopy techniques of Raman, infrared, and sum‐frequency generation spectroscopies to probe the fundamental aspects of interphases on the anode and cathode of LIBs. First the vibrational spectroscopy techniques and their relevant technical considerations for interphase characterization are briefly introduced. In the next step, the latest studies on the fundamental properties, composition, and structure of interphases employing vibrational spectroscopy techniques are presented. This review focuses on in situ/operando investigations; however, post‐mortem studies are also discussed briefly.

Study of a High-Voltage NMC Interphase in the Presence of a Thiophene Additive Realized by Operando SHINERS

“…However, conventional Raman spectroscopy has mainly been employed in battery research to characterize the composition and nature of the electrochemical processes in the bulk electrodes, failing largely to probe interfacial chemistries. 23 − 28 This is mainly due to the very inefficient Raman scattering process and the micrometric skin depth of Raman, which result in very low sensitivities for detecting nanometric thin interphases. 23 , 24 Both insufficiencies of conventional Raman can be mitigated by near-field Raman spectroscopy.…”

“… 23 − 28 This is mainly due to the very inefficient Raman scattering process and the micrometric skin depth of Raman, which result in very low sensitivities for detecting nanometric thin interphases. 23 , 24 Both insufficiencies of conventional Raman can be mitigated by near-field Raman spectroscopy. 24 , 26 , 29 , 30 This can be achieved by introducing plasmonic active nanoparticles to the surface of the electrodes in a technique known as shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS).…”

“…Different groups already utilized SHINERS to gain insights into the mechanisms of interphase formation on various anode materials. 23 However, to our knowledge, no operando SHINERS study has been performed on the analysis of CEI on NMC electrodes.…”

“…Raman spectroscopy can potentially offer trace analysis of materials suitable for interphase investigation. However, conventional Raman spectroscopy has mainly been employed in battery research to characterize the composition and nature of the electrochemical processes in the bulk electrodes, failing largely to probe interfacial chemistries. − This is mainly due to the very inefficient Raman scattering process and the micrometric skin depth of Raman, which result in very low sensitivities for detecting nanometric thin interphases. , Both insufficiencies of conventional Raman can be mitigated by near-field Raman spectroscopy. ,,, This can be achieved by introducing plasmonic active nanoparticles to the surface of the electrodes in a technique known as shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Optimized plasmonic nanoparticles on the surface of the electrode work as electromagnetic resonators to create a strong near-field in their vicinity and increase the efficiency of Raman scattering.…”

Differentiating between Ion Transport and Plating–Stripping Phenomena in Magnesium Battery Electrolytes Using Operando Raman Spectroscopy

“…Our groups have been active in this area and recently used attenuated total reflectance (ATR)-FTIR to re-examine one of the most widely used Mg electrolytes, the “all phenyl complex” (APC), which is a solution of dimagnesium trichloride tetraphenyl aluminate in tetrahydrofuran (THF) (active species [Mg 2 Cl 3 ] + [AlPh 4 ] − , Figure a). − We demonstrated that the ATR-FTIR spectroelectrochemical response is very sensitive to interfacial transport effects and reveals crucial changes in coordination environment of the electroactive dinuclear cation and solvent during plating and stripping. Despite the potential insights available from FTIR, spectra can be difficult to interpret in isolation due to the dominance and convolution of multiple solvent bands in different local clustering and coordination states . Raman spectroscopy offers a potential solution to this challenge, since the bulk solvent modes resulting from changes in dipole moment are typically inherently weaker in Raman scattering compared to FTIR.…”