Hz. As the voltage becomes more "negative", the phase shift begins to decrease, reaching 27.19° at -0.5 V where the intercalation starts to occur. Notably, the phase shift stabilizes at 27.19° under further "open" polarization, indicating continuous intercalation within the applied voltage range of -0.5 to -1 V. At very low frequencies, the phase shift increases again, likely due to the EDL. In contrast, under "blocked" polarization, the phase shift increases from 80.75° to 84.6° at -0.6 V, confirming a purely EDL mechanism. This value remains constant across the different tested voltages. These SPEIS results further validate the described mechanism and align with the current response observed in CV measurements.