Elucidating the Step‐Wise Solid Electrolyte Interphase Formation in Lithium‐Ion Batteries with Operando Raman Spectroscopy

The solid electrolyte interphase (SEI) is arguably one of the most critical components Li-ion cell. Despite decades studies SEI, its intrinsic complexity and lack suitable characterization tools still prevent a real consensus on governing mechanisms to be reached. Herein, operando Raman spectroscopy supported by complimentary online electrochemical mass spectrometry employed study SEI formation Au in model based LiClO4 ethylene carbonate (EC). Both itself cell contaminants, such as O2, CO2, H2O, contribute stepwise electro-/chemical processes build-up SEI. Effects associated with electrode/electrolyte double-layer charging, electrode adsorbate polarization (stark effect), dissolution are discerned. Lithium lithium oxide identified major products formed already ≈2 V versus Li+/Li. Although provides deeper insights into underlying mechanisms, complementary techniques necessary support spectral interpretations. Classical challenges field surface science, contaminations, have systematically addressed if puzzle ever will completed.