Solid Polymer Electrolyte fabrication

Ion conducting polymers may be preferable in these devices electrolytes because of their flexibility, moldability, easy fabrication and chemical stability (for the same reasons that they have been applied to lithium secondary batteries [19,48,49]). The gel electrolyte systems, which consist of a polymeric matrix, organic solvent (plasticizer) and supporting electrolyte, show high ionic conductivity about 10 5 S cnr1 at ambient temperature and have sufficient mechanical strength [5,7,50,51], Therefore, the gel electrolyte systems are superior to solid polymer electrolytes and organic solvent-based electrolytes as batteries and capacitor materials for ambient temperature operation. 

The necessary porosity for thicker layers was introduced by appropriate current densities [321-323], by co-deposition of composites with carbon black [28, 324] (cf. Fig. 27), by electrodeposition into carbon felt [28], and by fabrication of pellets from chemically synthesized PPy powders with added carbon black [325]. Practical capacities of 90-100 Ah/kg could be achieved in this way even for thicker layers. Self-discharge of PPy was low, as mentioned. However, in lithium cells with solid polymer electrolytes (PEO), high values were reported also [326]. This was attributed to reduction products at the negative electrode to yield a shuttle transport to the positive electrode. The kinetics of the doping/undoping process based on Eq. (59) is normally fast, but complications due to the combined insertion/release of both ions [327-330] or the presence of a large and a small anion [331] may arise. Techniques such as QMB/CV(Quartz Micro Balance/Cyclic Voltammetry) [331] or resistometry [332] have been employed to elucidate the various mechanisms. 

The development of solid polymer electrolyte cells is being actively conducted at General Electric Co. (13) and at Brown Boveri Research Center, Baden, Switzerland (14). As the name implies, the solid polymer electrolyte technology uses a solid polymer sheet as the sole electrolyte in the cells. It also acts as the cell separator. The majority of the present applications use Nafion with a thickness of 10-12 mils (13). Selected physical and chemical properties of Nafion 120 membranes are given in Table I. The membrane is equilibrated in water to approximately 30% water content prior to fabrication into a cell assembly. The hydrated membrane is highly conductive to hydrogen ions. It has excellent mechanical strength, and it is very stable in many corrosive cell environments. 

PANI-NTs synthesized by a template method on commercial carbon cloth have been used as the catalyst support for Pt particles for the electro-oxidation of methanol [501]. The Pt-incorporated PANl-NT electrode exhibited excellent catalytic activity and stabUity compared to 20 wt% Pt supported on VulcanXC 72R carbon and Pt supported on a conventional PANI electrode. The electrode fabrication used in this investigation is particularly attractive to adopt in solid polymer electrolyte-based fuel cells, which arc usually operated under methanol or hydrogen. The higher thermal stabUity of y-Mn02 nanoparticles-coated PANI-NFs on carbon electrodes and their activity in formic acid oxidation pomits the realization of Pt-free anodes for formic acid fuel cells [260]. The exceUent electrocatalytic activity of Pd/ PANI-NFs film has recently been confirmed in the electro-oxidation reactions of formic acid in acidic media, and ethanol/methanol in alkaline medium, making it a potential candidate for direct fuel cells in both acidic and alkaline media [502]. 

Overall, much effort has been made to develop biocompatible organic materials, which allows for the ultimate integration between the electronic device and biological system. The possibility of fabricating memory devices on biodegradable substrates, such as, rice paper and chitosan is also demonstrated. Biocompatible and flexible resistive switching memory devices are made on the basis of Ag-doped chitosan as the natural solid polymer electrolyte layer on the transparent and bendable substrate. Decomposable devices, where chitosan layer serves as the substrate while Mg as the electrode, have been also achieved (Hosseini and Lee, 2015). A comparison of the biocompatible material-based resistive switching memory devices is made in Table 3.2. 

Sung et al. [153,156] have described the fabrication and performance of prototype microcapacitors built with PPy and polythiophene electrodes. Interdigitated gold electrodes were patterned on silicon using standard photolithography, and the conducting polymers were then electropolymerized across them. The capacitor performance was evaluated with different polymer thicknesses and electrolytes. A snbseqnent development incorporated solid polymer electrolytes to prodnce a solid-state device [153], although the performance was diminished compared with devices operated in liquid electrolytes. 

In addition, the various types of polymer ionics can be easily fabricated into flexible thin films with large surface areas where the ions are free to move and can conduct electricity as in conventional liquid electrolytes. This has opened the challenging possibility of replacing the difficult to handle, often hazardous, liquid solutions by chemically inert, thin-layer membranes for the fabrication of advanced electrochemical devices. Particularly relevant in this respect has been the technological goal of replacing liquid electrolytes in lithium, non-aqueous batteries by a thin film of a solid polymer electrolyte which would act both as electrode separator and as a medium for ionic... 

In Chapter 10, the authors will demonstrate the preparation techniques for ASPEM and the characterization results. The relationship between structure and properties will be discussed and compared. The double-layer carbon air cathodes were also prepared for solid-state alkaline metal fuel cell fabrication. The alkaline solid state electrochemical systems, sueh as Ni-MH, Zn-air fuel cells, Al-air fuel cells, Zn-Mn02 and Al-Mn02 cells, were assembled with anodes, cathodes and alkaline solid polymer electrolyte membranes. The electrochemical cells showed excellent cell power density and high electrode utilization. Therefore, these PVA-based solid polymer electrolyte membranes have great advantages in the applications for all-solid-state alkaline fuel cells. Some other potential applieations include small electrochemical devices, sueh as supercapacitors and 3C electronic products. 

Liquid-junction photovoltaic cells have advantages in their simplicity and ease of fabrication, as described before. Solid-state devices can also be constructed from liquid-junction cells when a solid polymer electrolyte is used. A tandem photovoltaic... 

The absence of solvents in such solid-polymer-electrolyte photovoltaic cells presents the possibility of fabricating corrosion-free systems. The thin-film solid-state cells also allow fabrication of multispectral cells composed of more than one semiconductor in optical and electrical series. A solid-state photovoltaic cell, n-Si/Pt/PP/PEO(K.I/ l2)/Pt/ITO, was studied. The surface modifications of n-Si with PP can dramatically reduce the large activation energy barrier against efficient charge transfer between semiconductor and polymer-solid electrolyte. The efficiency of this cell is limited by a high surface recombination velocity associated with surface states of the n-Si. The cell had V = 225 mV and 11 niA cm at 100 mW cm illumination with junction ideality factor of 1.5. This implies the existence of deleterious surface states acting as recombination centres. 

The next entry is for Nafion, a proton-conducting fluorosulfonic acid ionomer material which in membrane form is widely used in PEM fuel-cell technology. The conductivity value quoted is for a fully hydrated membrane at an ambient temperature. Note that the conductivity is less than that of a comparable aqueous acid solution, for example 0.5 M sulfuric acid, but by a factor of only 3-4. Heavily hydrated Nafion membranes contain a lot of water, and consequently they behave a lot like aqueous acid solutions. The next three entries are for various gel and solid-polymer electrolytes containing lithium salts. All these material are membranes some contain some potentially volatile solvents, while others do not. Conductivities for these materials are low relative to true liquid solvents but they are still well within the range of usable values for electrochemical experiments. The semi-solid character of these materials, combined with their near-zero volatility (for solid-polymer electrolytes which do not contain volatile solvents), makes them suitable for use under high-vacuum conditions which makes them potentially useful for fabrication of electrochemical devices which are targeted for use in vacuum or under conditions which could otherwise result in solvent loss by evaporation. 

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). 

Akhtar et al. [295] have investigated solid-state electrochromatic devices fabricated from polyaniline and solid polymer electrolytes, prepared by mixing protonic acids or alkali metal salts with either PEO or poly(ethyleneimine). The device switches rapidly from colourless to green between — 3 to -F 3-V and appears to be stable after several thousand switching cycles. 

To improve effectiveness of the platinum catalyst, a soluble form of the polymer is incorporated into the pores of the carbon support structure. This increases the interface between the electrocatalyst and the solid polymer electrolyte. Two methods are used to incorporate the polymer solution within the catalyst. In Type A, the polymer is introduced after fabrication of the electrode in Type B, it is introduced before fabrication. 

In contrast to studies on PMMA and PS nanocomposites, limited information has been available concerning the fabrication of PVDF nanocomposites. PVDF has been used as a solid polymer electrolyte for attaining high solar energy conversion in DSCs [132,211,212]. Moreover, PVDF has become a favorable choice as the... 

Anandan et al. reported that PVDF was used as a component in fabrication of DSCs [211]. For such a purpose, heteropolyacid was impregnated in PVDF polymer with iodine/iodide as a solid polymer electrolyte for DSCs in order to effectively decrease the back-electron transfer reaction TiOi nanoparticles were used as dye-adsorbants. The solar cell, composed of new polymer electrolyte (PVDF), Ti02 nanoparticles (photoanode) and conducting carbon cement, was cemented on conducting glass (photocathode). An overall energy conversion efficiency of up to 8% was reported [211]. 

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