Particle surface equivalent circuit

Fig. 108a-c. Proposed equivalent circuits for. a an empty and b a semiconductor-particle-coated BLM. Porous structure of the semiconductor particles allowed c the simplification of the equivalent circuit. Rm, RH, and Rsol are resistances due to the membrane, to the Helmholtz electrical double layer, and to the electrolyte solutions, while C and CH are the corresponding capacitances Rf and Cf are the resistance and capacitance due to the particulate semiconductor film R m and Cm are the resistance and capacitance of the parts of the BLM which remained unaltered by the incorporation of the semiconductor particles R and Csc are the space charge resistance and capacitance at the semiconductor particle-BLM interface and Rss and C are the resistance and capacitance due to surface-state on the semiconductor particles in the BLM [652]... 

Fig. 6.16. Equivalent circuit representing the electrode system Ti02 Ag nanoparticles electrolyte and calculated Mott-Schottky curves for different portions of the electrode surface covered by metal particles (m) 0 (curve 1) 0.02 (curve 2) 0.2 (curve 3). CH = 10 pF/cm2 CM = 20 pF/cm, Nd = 1.5xl018 cm 3.

Among the various models ° " proposed in order to explain two-arc behavior in the Nyquist plot for the insertion electrode, the simple equivalent circuit " depicted in Figure 10(b) was used to analyze the impedance spectra. Flere, / ,. is the sum of the electrolyte and conducting substrate resistances Ream is the resistance associated with the particle-to-particle contact among the oxide particles Ccom is the contact capacitance due to the accumulation of charged species at the surface of the oxide particles Rat is the resistance associated with the absorption reaction of adsorbed lithium into the oxide and Cad represents the capacitance arising from the adsorption of lithium in the near-surface region of the oxide. 

Figure 4.5.8. Equivalent circuit of particle surface impedance taking into account a passivating layer.

The anode of a Ni-Cd battery typically consists of a mix of Cd and CdO powders with the addition of a conductive additive (acetylene black). The impedance of the anode-particle surface is determined by the activated adsorption of OH anions first on the metal surface, with subsequent conversion into Cd(OH)2 and hydrated CdO layers (Duhirel et al. [1992])). Reaction products are also present in a partly dissolved Cd(OH)3" state. The activated adsorption mechanism of the anode reaction, as well as porous structure of the electrode, makes it appropriate to use for its analysis the equivalent circuit shown in Figure 4.5.14. It was shown by Xiong et al. [1996], by separate impedance measurements on the anode and cathode, that most of the impedance decrease during discharge is due to the anode, as the initial formation of a Cd(OH)Jrate limiting step of the reaction. The... 

Figure 4.5.18. Equivalent circuit of tiie particle surface of a Li-intercalation anode.

If the impedance associated with the steel surface is negligible, the impedance of the zinc paint system will correspond to that of the zinc particles in the film. This system can be described using the uniform transmission-line equivalent circuit depicted in Figure 12-6. The total impedance of the system Z for a paint film of thickness is presented by Eq. 12-4 ... 

Features of the impedance spectra of Fig. 3.15a may be modeled by a simple modified Randles-Ershler equivalent circuit shown in Fig. 3.15c. In this model, is the solution resistance, and is the charge-transfer resistance at the electrode/eIectrol e interface. A constant phase element (CPE) was used instead of a doublelayer capacitance to take into account the surface roughness of the particle. Qn is the insertion capacitance, and Zw is the Warbui impedance that corresponds to the solid-state diffusion of the Li-ion into the bulk anode. The Warburg element was used only for impedance data obtained at the tenth charge. The electrical components of the surface film which is likely formed on the electrode were disregarded, because no time constant related to this process could be seen in the electrochemical impedance spectroscopy (EIS) spectra. It was also checked that their inclusion in the model of Fig. 3.15c does not improve the fit. 

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