Dry solid polymer electrolyte

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. 

Generally, polymer electrolytes used for ECDs can be classified into the following four types according to their physical configuration and chemical composition dry solid polymer electrolyte (DSPE), gel polymer electrolyte (GPE), porous gel polymer electrolyte (PGPE) and composite solid polymer electrolyte (CSPE). 

The first example of dry solid polymer electrolyte invented by Wright is the PEO-based system. Since this system does not contain any organic liquid and the polymer host is thus used as solid solvent, the safety performance is excellent and the mechanical strength and flexible geometry are good. However, the ion conductivity is too poor to be used. The second category of polymer electrolyte is called the GPE which is neither liquid nor solid or conversely both liquid and solid (Gray, 1991), and the gel... 

Trivedi et al [260] have fabricated a dry cell using polyaniline. The system is very simple and replaced manganese dioxide from a dry cell (Leclanche) by chemically synthesized polyaniline. The configuration of the battery is Zn/solid polymer electrolyte/polyani-line. This battery uses a solid polymer electrolyte composed of methoxy cellulose and polyvinyl sulphate with a cellulose sheet as a separator (Figure 12.23). 

Samad et al. developed a novel solid polymer electrolyte (SPE) based on polyfethylene oxide) (PEO) and CNCs by solvent-casting method for moderate temperature applications within the range 50-100°C. The effect of different amormts of CNCs was observed on strength, thermal, and electrochemical stability. On addition of 15% CNCs in SPE, about a five-times increase in tensile and storage modulus was measured. The effect of temperature on PEO and CNCs interaction while drying is demonstrated in Figure 15.13. 

It must be noted fliat an actuator with a linear displacement output can be used in more apphcations. To meet this demand, there have been some attempts to establish actuator configurations with a linear displacement output, in fact rectilinear, along a single direction (Lu et al. 2004 Kara et al. 2004d). One of the earliest attempts was realized by Mazzoldi et al. (1998). They placed a polyaniline (PANI) fiber doped in HCIO4 onto a solid polymer electrolyte and rolled them into a cylindrical stracture, where the PANI is in the middle. A copper wire was then helically wrapped around the cylinder to make the linear dry actuator. 

Polymer-based ion conducting materials have been of great interest to researchers in the field of lithium batteries since Armand et al proposed the use of poly(ethylene oxide) (PEO)-Li salts as a solid polymer electrolyte (SPE). In this application, the polymer electrolyte functions as a mechanical separator between the two electrodes and also as the ionic conductor. Polymer electrolytes are used in the form of thin films and may be either dry (organic solvent-free) or plasticised. A high specific energy density can be reached at medium temperature using a dry polymer electrolyte and lithium metal as the negative electrode. 

One of the typical preparation procedures of the solid polymer electrolytes is as follows. The polymer and lithium salts are first dissolved in a selective solvent under dry atmosphere to form a homogeneous solution. Then, the mixture is coated onto a PTFE plate and dried in vacuo for several days to give a polymer electrolyte membrane. 

The final product of an emulsion polymerization is referred to as latex. Emulsion polymerization products can in some instances be employed directly without further separations but with appropriate blending operations. Such applications involve coatings, finishes, floor polishes, and paints. Solid polymer can be recovered from the latex by various techniques such as spray drying, coagulation by adding an acid, usually sulfuric acid, or by adding electrolyte salts. 

Solid polymer acid electrolytes were first developed for fuel cell applications in the late 1950 s by the General Electric Company (GE), which initiated a program to develop membrane cells and electrolyzers. The first membranes developed by GE for fuel cell applications were made by the condensation of phenolsulfonic acid and formaldehyde. These membranes were found to be brittle, prone to cracking when dried, and rapidly hydrolyzed... 

FIGURE 2.81 Schematic diagrams of (a) dry solid-state polymer electrolyte (e.g., PEO/Li+), (b) gel polymer electrolyte, and (c) polyelectrolyte. (Zhong, C. et al. 2015. A review of electrolyte materials and compositions for electrochemical supercapacitors. Chemical Society Reviews 44 7484-7539. Reproduced by permission of The Royal Society of Chemistry.)... 

The cations are linked to the polymer chain matrix as shown schematically in Figure 1.5. As a consequence, for a solvent- and moisture-free polymer electrolyte, solvated cations are not mobile. By contrast, in an aqueous electrolyte it is comparatively usual for a cation to be surrounded by a solvation sheath, often containing four or six water molecules, and for this entire entity to be mobile. Solvation does not arise in dry solid electrolytes such as alpha silver iodide. 

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