The cathode−electrolyte interface (CEI) is a key factor that affects the electrochemical performance of lithium-ion batteries. However, considerable ambiguity still exists with regard to the composition and properties of the CEI at different potentials during cycling. In this study, we investigate the dynamic evolution behavior of the CEI between the LiNi0.6Co0.2Mn0.2O2 cathode and organic carbonate electrolytes by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and synchrotron soft X-ray absorption spectroscopy (soft XAS). XPS results reveal the continuous formation and decomposition of the CEI components during the initial charge and discharge process. Lithium alkyl carbonates and lithium fluoride (LiF) form during charging at low voltages, decompose at high voltages, and regenerate during discharging. In addition, soft XAS highlights the formation of electrochemically inactive species on the cathode surface, which generates extra barrier for Li+ diffusion and also decreases active sites for Li+ intercalation. The surface Ni undergoes incomplete oxidation during the charging process and exhibits partial reduction after discharging. These results are consistent with impedance variation in the first cycle and morphology changes on the cathode surface. These findings underscore the value of investigating and regulating the interfacial properties of lithium-ion batteries.