Transference potentiostatic polarization method

The number of precise methods to measure transference numbers in liquid aqueous electrolytes is quite acceptable [9-14]. Various methods are already used for more than a hundred years, such as the moving boundary, Hittorf s method, or the indirect determination of transference numbers by conductivity measurements. In contrast, accurate data for nonaqueous liquid electrolytes, especially with respect to hthium salts, are very rare. In hterature, the most often used methods are the potentiostatic polarization method and determination by NMR [21, 22]. Interestingly, the first was developed for solid electrolytes the latter is only valid for ideal solutions. To measure concentrated electrolyte... 

The behavior of the anion receptor TPEPB in a 1 M LiCl04 electrolyte in EC/DMC (1/2.5 v/v) was studied by Lee et al. [425]. The transference number of the lithium cation was enhanced by increasing the TPFPB content from 0.22 (0 M TPFPB) to 0.55 (0.1 M TPFPB), measured by the potentiostatic polarization method of Bruce and Vincent (see Section 17.4.6.4). The total ionic conductivity decreased due to the decreasing anionic conductivity, but the cationic conductivity increased. The interaction between TPFPB and Cl04, resulting in formation of a complex and advanced dissociation of LiCl04, was shown by FTIR analysis. 

Bruce etui, established a potentiostatic polarization method for solid polymer electrolytes [450], which is also used for diluted solutions because of its simphcity. For infinitely dilute electrolytes it was shown that this method is suitable for hquids as well [451]. Applying a small constant potential to a solution between nonblocking electrodes leads to decrease of the initial current value until a steady-state value is reached. The steady-state current is caused by the cations [450], so the cation transference number can be easily determined by dividing the cationic current by the initial current. Because electrode surfaces or rather passivating layers vary with time, this inaccurate description can be corrected by impedance measurements shortly before and after the potentiostatic polarization [452]. For small polarization potentials (< 10 mV), the steady-state current hs and initial current Iq are described as [450]... 

---