Ion Transference Number

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 

---

A lithium ion transference number significantly less than 1 is certainly an undesired property, because the resultant overwhelming anion movement and enrichment near electrode surfaces would cause concentration polarization during battery operation, especially when the local viscosity is high (such as in polymer electrolytes), and extra impedance to the ion transport would occur as a consequence at the interfaces. Fortunately, in liquid electrolytes, this polarization factor is not seriously pronounced. 

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... 

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... 

On the other hand, we have reported the preparation of gel-type polymer electrolytes using polyether/salt hybrid oligomers [12]. A network-type PPO film was swollen with the PPO/triiluoromethylsulfonamide Uthium salt hybrid. The obtained gel containing 50 wt% of PPO/salt hybrid showed a low Tg of —62°C. The PPO/salt hybrid behaved as not only an added salt but also a plasticizer. The ionic conductivity was over 10 S cm at room temperature. Furthermore this gel electrolyte showed a favorable lithium-ion transference number of 0.7-0.8. 

Transport parameters, which appear in the various forms of the infinite dilute transport equations, are the electrolyte conductivity, the ion mobility, the ion diffusion coefficient, and the ion transference number. All of these parameters can be determined from ionic equivalent conductances with units of (5-cm )/equiv) of cations and anions in solution. The ion mobility M , which appears in Equation (26.54), is related to by... 

The results of ion transference number measurement summarized in Table 12.3, shows the variation of ionic and electronic conductance of the NC s with increasing CNP concentration. The results show an increase in electronic conductivity with CNP concentration. 

Another approach extensively apphed in recerrt years to improve the ion conductivity ((, lithiirm ion transference number (C), mechanical properties, and the electrode-electrolyte interfacial stability of a polymer electrolyte is the addition of inorganic or ceramic fillers into the polymer-salt complexes (Capiglia et al., 1999 Kim et al., 2003 Chen-Yang et al., 2008 Croce et al., 2001 Rahman et al., 2009 Shen et al., 2009 Zhang et al., 2011 Munichandratah et al., 1995 Wiec-zorek, 1992). Micro and nano-sized inorganic filler such as silicone oxide (SiO ), alumina (AI2O3), ceria (CeO ), and so on are incorporated into PEO-salt complex in an effort to improve the mechanical, thermal stabihty, and ion conductivity of PEO-based polymer electrolytes. The effect of nano-fillers on the thermal properties of the PEO-based polymer complex varies with the type of nano-particles as well as the polymer-salt complex host matrix. 

Transport Number the proportion of the current carried by a particular ion (transfer number). 

Zhao J, Wang L, He X, Wan C, Jiang C (2008) Determination of lithium-ion transference numbers in L1PF6-PC solutions based on electrochemical polarization and NMR measurements. J Electrochem Soc 155 A292-A296... 

Recent studies also reveal that nanosized fillers are more effective in enhancing the ionic conductivity, lithium ion transference number and electrochemical stability (Kumar et al., 1994). Wang et al. (2010) introduced a fast ionic conductor with Lij jAlSO jTij 7(PO )j as filler in the PEO matrix. The authors achieved a high ionic conductivity of 4.53 x 10 S/cm at room temperature. 

Effect of nano particles of Al Oj on conventional SPE films have been examined by FTIR, DSC and B-G spectroscopy. The dispersal of Al O nano particles to the SPEs shows dechnation in the glass transition and melting temperature as established from DSC analysis. The FUR spectra show possible interactions between Al O nano particles and host SPE films. The optimum room temperature ionic conductivity of the order of 7 x 10 S/cm having minimum activation energy (E 0.22eV) is observed for NCPE films. This shows one order increment in the conductivity over the conventional SPE films. The temperature dependent conductivity shows Arrhenius type thermally activated behavior before as well as after glass transition temperature. Maximum value of ion transference number is found to be 0.96 which is indicative of predominant ionic (protonic) transport in the SPE and NCPE thin films. It has been observed that dielectric constant for SPE and NCPEs increases with temperature while it decreases with frequency. 

Finally, a simple measurement of a diffusion potential allows us to determine the potassium ion transference number as shown in the cell of Figure 20.7. 

For simplicity, we postulate the ion transference number (tj) to be a constant equal to that in the bulk. 

Lithium ion transference number approaching unity (to Umit concentration polarization)... 

Ion receptors are developed to bind to the cations or anions of the lithium salt in the electrolyte to promote ion dissociation and, therefore, increase ionic conductivity of the electrolyte. Although both cation and anion receptors have been shown to improve the ionic conductivity of electrolytes, cationic receptors slow down the mobility of Li" and, hence, reduce the Li ion transference number. In contrast, anion... 

As mentioned above, the primary purpose of anion receptors is to increase the ionic conductivity and Li ion transference number, although in some battery systems, the conductivity cannot be improved [73]. However, even in the early days of anion receptor research, researchers found other uses of these interesting molecules. To begin with, anion receptors can greatly increase the solubility of salts that are otherwise almost insoluble in organic electrolytes, such as LiF [70, 119, 138], Li20, and Li202 (Fig. 10) [150]. Electrolytes based on these salts that are traditionally... 

---