Solid Electrolyte Interphase Instability in Operating Lithium-Ion Batteries Unraveled by Enhanced-Raman Spectroscopy

The fundamental understanding of the electrode/electrolyte interfacial processes in lithium–sodium ion batteries (LIBs) and of their dynamics upon cycling is of prime importance for the development of new-generation electrode materials. Operando analyses using the utmost sensitive techniques are required to produce an accurate depiction of the underlying processes at the origin of the battery performance decay. Although enhanced Raman spectroscopy through the use of signal nanoamplifiers shows the required sensitivity, its implementation in operando conditions and particularly on functional materials in contact with organic electrolytes remains challenging. This work using extensive optimization of shell-isolated nanoparticle-enhanced Raman spectroscopy conditions for operando diagnosis of LIB materials, including the design of near-infrared active amplifiers and the control of the photon dose, demonstrates the possibility to track the dynamics of composition of the electrode/electrolyte interface upon cycling of LIB coin-cells and uncovers the origin of the irreversible capacity of tin electrodes proposed as an alternative to graphite anodes.