Nyquist plots, ionic conductivity

So far, the ionic conductivity of most ILs has been measured by the complex impedance method [116], In this method, charge transfer between carrier ions and electrode is not necessary. Therefore platinum and stainless steel are frequently used as blocking electrodes. However, it is often difficult to distinguish the resistance and dielectric properties from Nyquist plots obtained by the impedance measurement. In order to clarify this, additional measurements using non-blocking electrodes or DC polarization measurement are needed. 

Figure 6.10. Comparison of Nyquist plots of fuel cells with different Nafion loadings in the catalyst layers of both the cathode and the anode [7], (Reproduced by permission of ECS—The Electrochemical Society, from Guo Q, Cayetano M, Tsou Y, De-Castro ES, White RE. Study of ionic conductivity profiles of the air cathode of a PEMFC by AC impedance spectroscopy.)...

Figure 6.27. Nyquist plots (65000 to 0.82 Hz, 22 + 2°C, 1.00 V vs. H2) for nitrogen-bathed cathodes with various Nafion loadings. The inset shows an expansion of the high-frequency region of the plots [25], (Reproduced by permission of ECS—The Electrochemical Society, and the authors, from Li G, Pickup PG. Ionic conductivity of PEMFC electrodes.)...

When the temperature is changed, the Nyquist plot also changes, as shown in Figure 6.4 , due to the change in conductivity. Figure 6.4 shows the Nyquist plots for the ionic liquid prepared by the neutralization of l-benzyl-2-methylimidazole and HTFSI. The temperature dependence of the ionic conductivity is generally depicted by an Arrhenius plot (Figure 6Ab). 

Figure 6.4 Temperature dependence of the ionic conductivity for BzElmHTFSI. (a) Nyquist plots for various temperatures (b) the corresponding Arrhenius plot.

An overview on the topic of IS, with emphasis on its application for electrical evaluation of polymer electrolytes is presented. This chapter begins with the definition of impedance and followed by presenting the impedance data in the Bode and Nyquist plots. Impedance data is commonly analyzed by fitting it to an equivalent circuit model. An equivalent circuit model consists of elements such as resistors and capacitors. The circuit elements together with their corresponding Nyquist plots are discussed. The Nyquist plots of many real systems deviate from the ideal Debye response. The deviations are explained in terms of Warburg and CPEs. The ionic conductivity is a function of bulk resistance, sample... 

Figure 10.16(a) exhibits the Nyquist plot for the gel polymer electrolytes with different 12-crown-4 ether contents. For these systems, the plots did not exhibit a semicircle related to the electrolyte capacitance in the high frequency region, as normally observed for polymer electrolyte samples. A straight line was observed instead. The disappearance of this semicircle is due to the high ionic conductivity of the samples. The intersection of this straight line with the real axis provides the resistance value usually employed to calculate the ionic conductivity values, presented in Fig. 10.16(b). 

Analysis of electrolytes based on P(EO-EM) + 20 wt% Lil, 2 wt% I2 and 70 wt% GBL with different CE contents (a) Nyquist plots of the electrochemical impedance spectroscopy and (b) ionic conductivity values. The crown ether structure is shown in the inset. 

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