In the high-frequency regime, Figure demonstrates the real part of ionic conductivity as a function of excitation frequency, which corresponds inversely to the trend previously observed in impedance. In all spectra, σ′ shows an initial rise with increasing frequency, eventually reaching a plateau in the mid to high-frequency range. As frequency increases, the current begins to bypass the charge transfer resistance through the EDL capacitor. Moreover, the plateau observed at mid to high frequencies corresponds inversely to the series resistance. In contrast, the key feature of these σ″ spectra (Figure ) is the presence of a characteristic frequency (f0) at the local maxima, which refers to the charging of the EDL capacitance. This peak shifts towards higher frequencies with increasing LiTFSI concentration until 5 mol•kg -1 .