Solid transference number

Electronic conductivity of thin-film solid electrolytes. Besides having low electronic transference numbers, it is essential for thin films of the order of 1 jim that the magnitude of the electronic resistance is low in order to prevent self-discharge of the battery. For this reason, specific electronic resistances in the range of 1012-1014 Qcm are required for thin-film solid electrolytes. Often the color may be a valuable indication of the electronic conductivity. In this regard, solid electrolytes should preferably be transparent white [20]. 

To date there have been few reliable measurements of Hittorf transference numbers in solid polymer electrolytes because of experimental difficulties in applying the technique. Leveque, Le Nest, Gandini and Cheradame (1983) have, however, applied it to highly cross-linked networks where cells could be formed using a series of non-adherent thin... 

We begin our discussion by characterizing the electrical conduction in solid electrolytes. These are solids with predominantly ionic transference, at least over a certain range of their component activities. This means that the electronic transference number, defined as... 

Equations (4.94) and (4.95) provide examples of the fundamental equations which describe the electronic conduction in ionic solids. Figure 4-2 shows the electronic transference number tel as a function of the chemical potential of component X. 

Figure 15-12. Conductivities and transference numbers of solid electrolytes as a function of...

Equation (15.5) shows that for very high and very low A>2(/ o2) the transference number of the ions vanishes. From Eqn. (15.4), we read that ( E/dp oJ is zero if / (= 1 - /<.]) vanishes. This means that stabilized zirconia cannot be uied as a solid electrolyte in the ranges of oxygen potential where po>P and Pq2galvanic cells or in fuel cells. For p >Pot>P < the oxide is said to be in its electrolytic domain (Fig. 15-12). 

Although the lithium ion transference numbers in lithium salt/ IL solutions are important, especially for battery applications, few literature reports refer to the specific values. Since the component ions of the ILs themselves have high mobility, the lithium ion transference number should be low for most cases. In order to suppress the mobility of the component ions, we proposed zwitterion compounds having an imidazolium cation structure [119]. Normally, such zwitterions are solid... 

For a classical SEI electrode such as lithium, the surface films formed on it in most of the commonly used polar aprotic systems conduct Li ions, with a transference number (t+) close to unity. As stated earlier the surface films on active metals are reduction products of atmospheric and solution species by the active metal. Hence, these layers comprise ionic species that are inorganic and/or organic salts of the active metal. Conducting mechanisms in solid state ionics have been dealt with thoroughly in the past [36-44], Conductance in solid ionics is based on defects in the medium s lattice. Figure 8 illustrates the two common defects in ionic lattices interstitial (Frenkel-type) defects [37] and hole (Schottky-type) defects [38],... 

The class of ionic conductors is not unambiguously defined in literature. Depending on context, this term maybe used either for solid electrolytes where the ion transference number is higher than 0.99, or for any solid material where ions are mobile, including mixed ionic-electronic conductors where the partial ionic and electronic diffusivities are comparable. The latter term is used for materials where the ion transference numbers are lower than 0.95-0.99, and also in conditions when a minor contribution to the total conductivity (ionic or... 

The overall permeation rate of a material is determined by both ambipolar conductivity in the bulk and interfacial exchange kinetics. For -> solid electrolytes where the electron - transference numbers are low (see -> electrolytic domain), the ambipolar diffusion and permeability are often limited by electronic transport. 

Correlation 7.181 should be used with care at low Reynolds numbers. Typical values for gas-solid transfer are 1 m mi"2 s 1 for the mass transfer coefficient and 102 W m-2 K-1 for the heat transfer coefficient. 

For the very small particles and the very dilute two-phase system considered, the mass transfer number can be estimated by Sh=kgdp/D=2 (Ranz and Marshall, 1952). The diffiision coefficient, D, can be estimated by Fuller et al, (9) The solids hold-up equals G,/psU, (10), with G. as the solids flux in kg/(m, s), p, the particle density with u, approximating the gas velocity Ug. Values for these parameters are listed in Table 3. 

It can be observed from Equation (1.27) that the average ionic transference number indicates on the m/deviation of the electrochemical cell (1.20) from the thermodynamic cm/at the presence of electronic conductivity in solid electrolytes. 

In Chapter 2 we learned how to interpret the spatial temperature distribution of steady problems in terms of the Biot number (recall Fig. 2.15). Here we extend this interpretation to the spatial temperature distribution of unsteady problems. Consider a solid transferring heat unsteadily with a coefficient h to an ambient at temperature Too- Let the instantaneous surface temperature be Tw, and the temperature of the solid relative to this temperature be AT in the neighborhood of the surface (Fig. 3.1). 

A good solid electrolyte should have an ionic conductivity of at least 0.01 (fi cm)" with an electronic transference number that should not exceed 10 . At lOOOK, show that the minimum band gap for such a solid would have to be 4eV. Assume that the electronic and hole mobilities are equal and that each is 100 cm"/V s. State all other assumptions. 

The ion transference number of mobile ions (mostly hydronium) in the solid gum Arabica biopolymer is estimated by Wagner s polarization technique [16] using blocking electrodes. The ionic transference number is found [17] to... 

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