Application of Generalized Transmission Line Models to Mixed Ionic-Electronic Transport Phenomena

Abstract

Application of a generalized equivalent circuit including the electrode condition for the Hebb-Wagner polarization in the frequency domain proposed by Jamnik and Maier can provide a consistent set of material parameters, such as the geometric capacitance, partial conductivities, chemical capacitance or diffusivity, as well as electrode characteristics. Generalization of the shunt capacitors for the chemical capacitance by the constant phase elements (CPEs) was applied to a model mixed conducting system, Ag 2 S, with electron-blocking AgI electrodes and ion-blocking Pt electrodes. While little difference resulted for the electron-blocking cell with almost ideal Warburg behavior, severely non-ideal behavior in the case of Pt electrodes not only necessitates a generalized transmission line model with shunt CPEs but also requires modelling of the leakage in the cell approximately proportional to the cell conductance, which then leads to partial conductivity values consistent with the electron-blocking case. Chemical capacitance was found to be closer to the true material property in the electron-blocking cell while excessively high chemical capacitance without expected silver activity dependence resulted in the electron-blocking cell. A chemical storage effect at internal boundaries is suggested to explain the anomalies in the respective blocking configurations.

Application of a General Gas Electrode Model to Ni-YSZ Symmetric Cells: Humidity and Current Collector Effects

“…Normal units of the diffusivity and rate constants may be derived from an effective C value using the relaxation time τ = (RA) 1/α as the representative value for RC responses. 21,41,42) Such approaches are not, however, rigorously supported.…”

Chemical Diffusivity for Hydrogen Storage: Pneumatochemical Intermittent Titration Technique

“…Small (d E /d c ) or λ in the plateau region formally leads to low D̃ according to eq or for FITT, as well as GITT, eq . Although the presence of two phases in the plateau region does not concur with the application of the diffusion equation eq , GITT is often applied to the electrochemical storage system with a wide range of the plateau region, resulting in apparent or effective chemical diffusivity lowered by orders of magnitude in the plateau region. − Such a low chemical diffusivity may be considered as a consequence of the large chemical capacitance, − , but a specific kinetic information seems difficult to be construed. There is an additional problem in the application of GITT or FITT in the plateau region even for any effective kinetic information.…”

A comprehensive treatment of universal dispersive frequency responses in solid electrolytes by immittance spectroscopy: low temperature AgI case

“…In view of the transmission line expression Z W = √ r/j ωc, the energetics suggest a diffusion process in the solid electrolyte system controlled by the charge carriers responsible for the conduction. The case cannot be explained by the diffusion process in fully supported liquid electrolyte [43] or solid mixed conductor system [44][45][46][47], where the minority charge carriers are responsible for the diffusion process. The observation in AgI system in addition to β -alumina [8] further suggests a universal presence of ideal Warburg electrode response closely related to the bulk conduction process in solid electrolytes.…”