A systematic approach to the impedance of surface layers with mixed conductivity forming on electrodes

Abstract

-Electrode impedance can be evaluated on the basis of the electrode reaction kinetics in many systems, even for complicated electrode reactions. However, when a surface layer is present on the electrode surface, the theoretically well-established impedance model of the electrode reaction is often completed with phenomenological equivalent circuit elements in order to achieve the number of time constants as derived from the electrode impedance spectra measured In these cases, the meaning of the phenomenological equivalent circuit elements are often unclear, though the presence of these elements is helpful to describe the system throughout the frequency domain used for the measurement. In the present work, an attempt will be shown to separate the effect of the electronic and ionic charge transfer in a surface layer and to identify the appropriate equivalent circuits. Examples are shown from the fields of lithium-ion batteries where a solid electrolyte interface as a surface layer is present at the negative electrode and the contribution of various charge carriers may be of importance.2

A TiO2@MWCNTs nanocomposite photoanode for solar-driven water splitting

“…The EIS spectrum shows that the Voigt circuit is found to fit the TiO 2 electrode. In contrast, the EIS spectrum of the TiO 2 @MWCNTs electrode, including two semicircle parts, demonstrates different responses of the electrode at low and high frequencies [ 42 – 43 ]. Additionally, the equivalent circuit fitted to the TiO 2 @MWCNTs electrode indicates that electron and ion transfers and the electrode material contribute to the overall charge transfer [ 43 ].…”

MODERN RESEARCH METHODS OF PHYSICOCHEMICAL AND ELECTROCHEMICAL PROPERTIES OF ELECTROLYTES IN FOR Li-ION BATTERIES AND HYBRID SUPERCAPACITIES

“…Also, such interpretation partially corresponds to the Voight's model for rubber-like materials (impedance at the local contact area between flexible surface film and electrode) [17,59]. More reasonable is a model that takes into account the simultaneous transport of electrons and ions in the counterflow (Figure 4) [47]. More reasonable is a model, that takes into account the simultaneous transport of electrons and ions in the counterflow (Figure 4), [47].…”

“…As a rule, we have to consider the formation of a passivation film on the metal surface of the current collector (or often oxide corrosive film) and the formation of a solid electrolyte film on the surface of the cathode and anode material, as well as the formation of a double electric layer [47]. Models of this type are given in Fig.…”

“…More reasonable is a model that takes into account the simultaneous transport of electrons and ions in the counterflow (Figure 4) [47]. More reasonable is a model, that takes into account the simultaneous transport of electrons and ions in the counterflow (Figure 4), [47]. Among all the mentioned examples, R SOL elements and the double layer capacity of CSL / SOL could be attributed to the electrolyte component of the batteries because the electrolyte is directly involved in the formation of a solid surface film and ionic conductivity.…”

“…A very important aspect in research of lithium and sodium secondary power sources is to in-vestigate the properties, formation, and functioning conditions of a solid protective film formed on cathode and anode materials after the first cycle due to the destruction of some electrolyte part [45-48, 50-51, 54]. The only possible way to carry out the study of this film without opening the battery is to construct an electrochemical model of the system, which will allow us to interpret the data obtained by electrochemical impedance spectroscopy and calculate the values of interest [47]. Most of the equivalent schemes constructed to explain the impedance of a lithium-ion battery follow one of the three examples (Fig.…”