Single ion polymer electrolytes

Structures of some polymers for use as single ion polymer electrolytes. 

Various single ion polymer electrolyte backbone structures are possible. The fixed anion is commonly carboxylate, sulfonate, or borate. Some structures are shown in Figure 10.34. The ionic conductivity of these structures can be as high as 7 x 10 S/cm. 

Phenolate units can also be used as fixed anions and can be introduced into the polymer structure to obtain a single ion polymer electrolyte. 

Due to the reduced number of charge carriers, Lh ions and anions have a high capability to form ion pairs. Therefore, the ionic conductivity of a single ion polymer electrolyte is lower than that of double ion polymer electrolytes. To facilitate dissociation and increase the ionic conductivity, major future improvements are expected to lie in the following directions ... 

Structures of some single ion polymer electrolytes based on aluminate. See Text for description of (a) through (c). 

Abstract The chapter begins by discussing the characters and composition of polymer electrolytes for electrochromic devices. It then describes the four types of the polymer electrolytes dry solid polymer electrolyte, gel polymer electrolyte, porous gel polymer electrolyte and composite solid polymer electrolyte, their preparation procedures and properties especially ion conductivity of the samples. Finally, new types of polymer electrolytes including proton-conducting, alkaline, single ionic polymer electrolytes and electrolytes with ionic liquids are also introduced. 

Design of organoboron polymer electrolytes will continue to have a great deal of potential based on the ability to tailor boron atoms. This is an attractive approach for single ion conductive materials. 

One of the most important parts of the fuel cell is the electrolyte. For polymer-electrolyte fuel cells this electrolyte is a single-ion-conducting membrane. Specifically, it is a proton-conducting membrane. Although various membranes have been examined experimentally, most models focus on Nafion. Furthermore. it is usually necessary only to modify property values and not governing equations if one desires to model other membranes. The models presented and the discussion below focus on Nafion. 

Ion-exchanger resins as solid polymer electrolytes, impregnated with the cations of the chosen anode metal, may prove applicable. Their use in the fuel-cell/electrolyzer single module concept is already under investigation as to complexity and operability (115). Doubtless better SPE s will be discovered. 

In addition to the modified electrodes described in the previous sections, which usually involve a conductive substrate and a single film of modifying material, more complicated structures have been described. Typical examples (Figure 14.2.4) include multiple films of different polymers (e.g., bilayer structures), metal films formed on the polymer layer (sandwich structures), multiple conductive substrates under the polymer film (electrode arrays), intermixed films of ionic and electronic conductor (biconductive layers), and polymer layers with porous metal or minigrid supports (solid polymer electrolyte or ion-gate structures) (6,7). These often show different electrochemical properties than the simpler modified electrodes and may be useful in applications such as switches, amplifiers, and sensors. 

Single lithium ion conducting polymer electrolytes have been prepared by the copolymerizahon of hthium(4-styrenesulfonyl)(trifluoromethanesulfonyl) imide and methoxy-poly(ethylene glycol) acrylate [117]. The highest ionic conduchvihes for the copolymer electrolytes are 7.6 x 10 S cm at 25 °C and then grow to reach 10 " S cm at 60 °C, at a raho of ethylene oxide to Li+ of 20.5. 

Feng S, Shi D, Liu F, Zheng L, Nie J, Feng W, et al. Single lithium-ion conducting polymer electrolytes based on poly[(4-sty-renesulfonyl)(trifluoromethanesulfonyl)imide] anions. Electrochimica Acta 2013 93 254-63. 

Alternative routes to obtain lithium-ion plastic batteries have considered the use of PAN-based gel-type polymer electrolytes as separators. These electrolyte membranes, although macroscopically solid, contain in their structure the active liquid electrolyte (Figure 7.7). Therefore, they have a configuration which in principle allows a single lamination process for the fabrication of the lithium-ion battery, i.e., a process that avoids intermediate liquid extraction-soaking activation steps. 

The bulk of EAP-based supercapacitor work to date has focused on Type I devices. Polypyrrole (PPy, Figure 9.4C) has been studied [147,151-153] for this application, with specific capacitance values ranging from 40 to 200 F/g. Garcia-Belmonte and Bisquert [151] electrochemically deposited PPy devices that exhibit specific capacitances of 100-200 F/cm with no apparent dependence on film thickness or porosity extensive modeling of impedance characteristics was used. Hashmi et aL [153] prepared PPy-based devices using proton and lithium-ion conducting polymer electrolytes. As is often observed, electrochemical performance suffered somewhat in polymeric electrolytes single electrode specific capacitances of 40-84 F/g were observed with stability of 1000 cycles over a 1 V window. 

Fig. 7.18 A comparison of the lithium diffusion coefficient in PEO-based single ion conductors (Fig. 7.14) and PEO-based binary comb-branch polymer electrolytes (Fig. 7.10) from simulations...

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