The CEDL obtained using the characteristic frequency method (Figure ) was compared with the differential capacitance derived from cyclic voltammetry. The appearance of cathodic and anodic humps at -0.3 V and 0 V for the 10 and 20 mol•kg⁻¹ concentrations could be due to the presence of unwanted impurities (Figure ). Giurlain et al. also reported similar peaks in CVs for stainless steel, Ti, and Cu current collectors ascribing the decomposition of LiTFSI. Hence, the capacitive current from the shaded anodic and cathodic potential regions was divided by the scan rate to estimate the average differential capacitance. Despite variations in cell setup, working electrode, electrochemical approach, and applied potential range, a similar trend in bulk capacitance was observed. The capacitance values were within the same order of magnitude, with a maximum value at 10 mol•kg⁻¹. Above this concentration, a declining trend in the capacitance was recorded due to inadequate ion dissociation at these very high concentrations. Based on the above electrochemical characteristics, it is envisioned that quicker polarization, i.e. improved charge/discharge rate performance or power performance of the capacitor cell, could be achieved at 5 mol•kg⁻¹ due to higher permittivity values. Conversely, 10 mol•kg⁻¹ may be more suitable for delivering higher EDL capacitance and greater energy density. The following section provides a broader insight into ion-pairing, using several qualitative, configurational, and quantitative approaches to narrate a proper understanding of EDL structure in water-in-salt electrolytes.