Ionic conducting polymers conductors

A special class of conductors are ionically and electronically conducting polymers (Sections 2.6.4 and 5.5.5). 

Polymer electrolytes (e.g., poly (ethylene oxide), poly(propylene oxide)) have attracted considerable attention for batteries in recent years. These polymers form complexes with a variety of alkali metal salts to produce ionic conductors that serve as solid electrolytes. Their use in batteries is still limited due to poor electrode/electrolyte interface and poor room temperature ionic conductivity. Because of the rigid structure, they can also serve as the separator. Polymer electrolytes are discussed briefly in section 6.2. 

Although the motion of protons does not lead to electrical conduction in the case of benzoic acid, electronic and even ionic conductivity can be found in other molecular crystals. A well-studied example of ionic conduction is a film of polyethylene oxide (PEO) which forms complex structures if one adds alkaline halides (AX). Its ionic conductivity compares with that of normal inorganic ionic conductors (log [cr (Q cm)] -2.5). Other polymers with EO-units show a similar behavior when they are doped with salts. Lithium batteries have been built with this type of... 

In contrast, in most ion-selective membranes the charge conduction is done by ions. Thus, a mismatch between the charge-transfer carriers can exist at the noble metal/membrane interface. This is particularly true for polymer-based membranes, which are invariably ionic conductors. On the other hand, solid-state membranes that exhibit mixed ionic and electronic conductivity such as chalcogenide glasses, perovskites, and silver halides and conducting polymers (Lewenstam and Hulanicky, 1990) form good contact with noble metals. 

It is known that the catalyst layer is far from uniform, especially in the case of a gradient catalyst layer. Thus, profiling properties, such as conductivity, in the catalyst layer are important. Both an electronic conductor (carbon) and an ionic conductor (Nafion ) exist in the catalyst layer, which can be considered a conductive polymer. The conductive polymer electric circuit model has been applied to the catalyst layer, and an ionic conductivity profile was obtained [8], as shown in Figure 4.33. 

The idea that ions can diffuse as rapidly in a solid as in an aqueous solution or in a molten salt may seem astonishing. However, since the 1960s, a variety of solids that include crystalline compounds, glasses, polymers, and composite materials with exceptionally high ionic conductivities have been discovered. Materials that conduct anions (e.g. and 0 ) and cations including monovalent (e.g. H+, Fi+, Na+, Cu+, Ag+), divalent, and even trivalent and tetravalent ions have been synthesized. A variety of names that have been used for these materials include solid electrolytes, superionic conductors, and fast-ionic conductors. Solid electrolytes arguably provides the least misleading and broadest description for this class of materials. 

These are presented by two subclasses of electroactive polymer (i) -conjugated polymers of both organic and inorganic nature [5-15] and (ii) conventional redox polymers [26], and by inorganic ion-insertion (intercalation) compounds [27, 28[ (see the top of Scheme 11.1b). Despite the different nature of their chemical bonds, all of these compounds are mixed, electronic-ionic conductors [29], and hence, their electronic and/or ionic conductivity is expected to change with the applied potential in a predictable, characteristic manner (see Section cl 1.4). 

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