Exchange Process in the Dielectric Loss of Molecular and Macromolecular Ionic Conductors in the Interfacial Layers Formed by Electrode Polarization Effects

Abstract

Here we report a first analytical approach to determine the spectral dependence of the complex permittivity function of molecular and macromolecular ionic conductors in the interfacial layers formed by electrode polarization effects. We show that a previous model of electrode polarization effects that was successfully applied for describing the dielectric behavior of ionic liquids (Serghei, A.; Tress, M.; Sangoro, J. R.; Kremer, F. Electrode polarization and charge transport at solid interfaces. Phys. Rev. B 2009, 80, 184301) can be now generalized and applied for polymer/ionic liquid blends as well as for poly(ionic liquid)s. The determined dielectric function of the interfacial layers reveals a dramatic change in the charge transport process manifested by a large decrease in conductivity. Our approach brings the first evidence for a relaxation peak detected in the dielectric loss of the interfaces, which is attributed to an exchange process between the interface and the bulk. This study gives new insights into the mechanism of charge transport at interfaces and could thus contribute to a better correlation between the dielectric properties of ion conducting materials and their electrochemical behavior at interfaces.

Maxwell-Wagner-Sillars interfacial polarization in dielectric spectra of composite materials: Scaling laws and applications

“…With increasing the form factor, the values of ε' net increase and the MWS peak is shifted to lower frequencies (Figure 15). Parallel dependencies are observed, implying (14) which is identical with the scaling laws that were determined before.…”

“…This is because, in both cases, the global dielectric response is given by a serial circuit of two complex capacities, where two different dielectric function must be taken into consideration: (a) the dielectric functions of the two different dielectric phases, in the case of interfacial polarization; (b) the dielectric function of the bulk and that of the interfacial layers formed in contact with the measurement electrodes in the case of electrode polarization. 6,13,14,48,50 Both situations lead to dielectric curves having a similar shape (Figure 17), both showing a dielectric peak in the global dielectric loss. However, despite the fact that both phenomena of electrical polarization can de described by using the same mathematical formalism (eq.…”

“…From an electrical point of view, an interface is an internal surface between two phases having different electrical and dielectric properties. 14 The existence of internal surfaces has a major consequence on the interpretation of the dielectric properties of heterogeneous materials 15–23 : the global dielectric response must be now described by at least two different complex dielectric functions, such as for instance, the complex dielectric permittivity function of the phase A (εA∗=ε′A−iε″A) and the complex dielectric permittivity function of the phase B (εB∗=ε′B−iε″B). If an interphase is formed between the two phases, a third complex dielectric function must be taken into account to describe the dielectric behavior of the system under study (εinterphase∗=ε′interphase−iε′′interphase).…”

Frequency-Dependent Dielectric Permittivity in Poisson–Nernst–Planck Model

“…As a matter of fact, low frequency relaxations have been attributed not only to free particles effects. The evidence of low relaxation frequency has been reported and credited to an exchange process between bulk, molecular and macromolecular materials and metal surfaces . More recently, an apparent DC conductivity has also been observed in small molecules connecting a cation and an anion by a covalent bond .…”

“…The evidence of low relaxation frequency has been reported and credited to an exchange process between bulk, molecular and macromolecular materials and metal surfaces. 20 More recently, an apparent DC conductivity has also been observed in small molecules connecting a cation and an anion by a covalent bond. 21 Such apparent DC conductivity has been hypothesized to be caused by the enormous dipoles of zwitterions rotation under the alternating AC field.…”