Operando Fourier Transform Infrared Investigation of Cathode Electrolyte Interphase Dynamic Reversible Evolution on Li1.2Ni0.2Mn0.6O₂

forming a polyanion group initially, which will weaken the electrostatic force between the anionic groups and EC to reduce the concentration of EC on the cathode surface and prevent the continuous decomposition of EC at a high voltage. X-ray photoelectron spectroscopy also verifies the presence of polyanion groups and their further participation in CEI formation. This work highlights the dynamical stability of CEI modified by moderate TMSB and the formation mechanism of this dynamical change during cycling characterized by the operando ATR-FTIR technique, which paves the way for a better understanding of the complex and hard-characterized cathode interface reactions.