Since lSL is the closest distance of any hydrated Li + or TFSI -ion to the electrode surface, the summed RH values of Li + and H2O, and TFSI -and H2O were considered for determining the lSL of Li + and TFSI -, respectively. The detailed methodology of obtaining RH of Li + , TFSI - , and H2O is discussed in Method S6 and the calculated values are illustrated in Figure . With increasing salt concentration, lSL was found to decrease from ~7 to 5 Å (Figure ). This range of lSL values is in line with the range ~3-10 Å reported in the literature. The presence of strong electric fields within the Stern layer, even at relatively low potential drops of 10 mV, significantly reduces the permittivity of water due to the reorientation of water molecules and the accumulation of counterions at the electrode surface. This reduction in permittivity of water can vary significantly, ranging from ~78 to 6, influenced by factors such as surface charge density, electrolyte composition, and distance from the surface. Hence, we calculate the CSL using both original (Figure ) and tenfold reduced permittivity values to cover a comprehensive range within the correct order of magnitude. . Figure demonstrates the CSL of Li + and TFSI -with (R) and without reduction (NR) of relative permittivity. Li + shows a higher CSL due to its smaller RH and lSL compared to TFSI -. The relative permittivity of 1 mol•kg⁻¹ and 20 mol•kg⁻¹ solutions is 68.17 and 17.26, respectively, resulting in a fivefold decrease in CSL from 1 mol•kg⁻¹ to 20 mol•kg⁻¹. Finally, by combining different CDL and CSL using the GCS Equation 5, the overall CEDL was obtained. Figure shows the trend of CEDL using the modified lDL matching the experimentally obtained values within the same order of magnitude. In contrast, using the classical lDL, underestimation of the CEDL was evident, deviating from the experimental trend. Utilizing the above properties of nonporous electrode, we have extended our study to the EDL structure within a multiporous carbon electrode of electrochemical capacitor cells as described in the following section.