Ionic conductivity, decay

A polymer electrolyte with acceptable conductivity, mechanical properties and electrochemical stability has yet to be developed and commercialized on a large scale. The main issues which are still to be resolved for a completely successful operation of these materials are the reactivity of their interface with the lithium metal electrode and the decay of their conductivity at temperatures below 70 °C. Croce et al. found an effective approach for reaching both of these goals by dispersing low particle size ceramic powders in the polymer electrolyte bulk. They claimed that this new nanocomposite polymer electrolytes had a very stable lithium electrode interface and an enhanced ionic conductivity at low temperature. combined with good mechanical properties. Fan et al. has also developed a new type of composite electrolyte by dispersing fumed silica into low to moderate molecular weight PEO. 

In the KI/C12 reaction, an interesting effect of high defect concentration in preventing growth of nuclei of a new solid phase was disclosed [103]. Solid samples differed widely in their initial ionic conductivity and hence in their initial concentration of cation vacancies. The ones with high vacancy concentration reacted very slowly with chlorine and the colour of iodine was seen uniformly as a pale coloration of the whole solid, which had reacted to the extent of only a few percent after several days. Samples with a low vacancy concentration reacted more rapidly and a sharp boundary developed between an outer, iodine-blackened completely reacted region and a pale-coloured inner region. In the un-reactive samples, electronic (presumably positive hole) conductivity appeared transiently for a few hours and then decayed. In the reactive... 

One single property of filler - electric conductivity - affects many properties of the final products. These properties include electric insulation, conductivity, superconductivity, EMI shielding, ESD protection, dirt pickup, static decay, antistatic properties, electrocatafysis, ionic conductivity, photoconductivity, electromechanical properties, thermo-electric conductivity, electric heating, paintability, biocompati-bilify, etc. Possession of one of these properties in a polymer can make it useful in industiy and eveiyday use. Examples are given in Chapter 19. Here, the electrical... 

Once the set dissolution time had elapsed, the tip was withdrawn at a high speed to ensure that the contact between meniscus and substrate was broken abruptly, resulting in a rapid ionic conductance current decay as the meniscus shrank in size (Figure 19.15b). This variation of the ionic conductance with respect to time, together with an accurate measurement of the pipette shape and dimensions (by FE-SEM), and footprint of the meniscus on the surface (by AFM), permitted quantitative analysis of experimental data by FEM modeling. ... 

However, ionic species are undoubtedly present in irradiated polymers and persist for a considerable time after irradiation. This is demonstrated by the radiation-induced conductivity observed in most plastic insulators and by the slow decay of this conductivity, which may still be noticeable several months after irradiation (7). 

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