Before delving into the impedance characteristics of the EDL, we first analyze the fundamental physico-chemical processes at the interface that govern its impedance response. Figure presents a schematic of the modified Gouy-Chapman-Stern (GCS) model, updated as the basis for this study. At the electrode surface, the electrostatic potential induces ion accumulation at the interface, forming a depleted region near the electrode known as the Helmholtz (Stern) layer. As illustrated in Figure , the thickness of this layer is potential-dependent, governed by the competition between electrostatic attraction and hydration effects . A higher applied potential enhances electrostatic forces, drawing ions closer to the surface while necessitating partial or complete dehydration of their hydration shells. Anions, which exhibit a greater propensity for surface adsorption, undergo significant dehydration under strong electric fields, whereas cations experience only partial suppression of their hydration shells . This results in a generally thinner Helmholtz layer for anions-determined by their intrinsic ionic radii-compared to cations, whose effective size is dictated by their hydrated radii. (more information is provided in SI section 1.2) On the solvent side, water molecules within the Helmholtz layer align under the influence of the intense local electric field (1-10 V/nm) , leading to permittivity saturation in this region(more information is provided in SI section 1.1). As shown in Figure , the relative permittivity is in its minimum within the Stern layer. As the distance from the electrode increases, the electric field weakens, leading to a gradual rise in permittivity toward the bulk electrolyte. .