New type of polymer electrolyte

The breakthrough of commercial applications of the ECDs has been limited by weaknesses such as long switching time, insufficient cyclability and long-term stability. To bypass some of these problems, a significant part of the research needed to be focused on the usage of a new type of 

Ionic liquids are organic salts with a low melting point ( 100°C), which are molten fiuid salts at room and even sub-ambient temperatures. They have favourable properties of chemical stability, low flammability, negligible vapour pressure, high ionic conductivity and wide electrochemical window. Furthermore, most of them are transparent (negligible visible light absorption) and so are suitable for BCD. In order to combine the attractive performances of ionic liquids with the advantages of a solid state medium, CPEs were proposed that consisted of ionic liquids mixed with polymer or gel matrices.  

Polymer electrolyte with ionic liquids N-butyl-N-methylpyrrolidiniwn bis(trifluoromethanesulphonyl) imides (PYRuTFSI) 

1V-butyl-A -methylpyrrolidinium bis(trifluoromethanesulphonyl) imides (PYR14TFSI) have the lowest melting point temperature (under 0°C), and are the most interesting for ECD apphcations.  

Polymer electrolyte based on l-[3-(trimethoxy-)d-silyl)propyl]imidazole (TMSPIm) 

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Since the initial discovery of Armand et al. [24], there has been a growing interest in ion-solvating polymers and there has been considerable effort to develop new types of polymer electrolytes. Most of the investigations have enhanced the ionic conductivity to about 10 S/cm. Further improvements could be made, such as decreasing the thickness of the membrane without decreasing its physical strength. However, the stabihty of this material is very low due to the presence of KOH within the matrix. Moreover, the ionic conductivity decreases continuously due to the leaking out of KOH. In reahty, this leads to the same problems as found with liquid electrolyte, such... 

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. 

Finally, it was demonstrated that cycle life of ECDs is significantly enhanced (up to 70000 cycles) when this new type of polymer electrolyte was used. 

For this reason, other types of electrolytes are used in addition to aqueous solutions (i.e., nonaqueous solutions of salts (Section 8.1), salt melts (Section 8.2), and a variety of solid electrolytes (Section 8.3). More recently, a new type of solid electrolyte is being employed more often (i.e., water-impregnated ionically conducting polymer films more about them in Chapter 26). 

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. 

Ohno, H., Yoshizawa, M., Ogihara, W. (2003) A new type of polymer gel electrolyte zwitterionic liquid/polar polymer mixture. Electrochim. Acta, 48, 2079-2083. 

Many different types of fuel-cell membranes are currently in use in, e.g., solid-oxide fuel cells (SOFCs), molten-carbonate fuel cells (MCFCs), alkaline fuel eells (AFCs), phosphoric-acid fuel cells (PAFCs), and polymer-electrolyte membrane fuel cells (PEMFCs). One of the most widely used polymers in PEMFCs is Nalion, which is basically a fluorinated teflon-like hydrophobic polymer backbone with sulfonated hydrophilic side chains." Nafion and related sulfonic-add based polymers have the disadvantage that the polymer-conductivity is based on the presence of water and, thus, the operating temperature is limited to a temperature range of 80-100 °C. This constraint makes the water (and temperature) management of the fuel cell critical for its performance. Many computational studies and reviews have recently been pubhshed," and new types of polymers are proposed at any time, e.g. sulfonated aromatic polyarylenes," to meet these drawbacks. 

Figure I.6a also reveals the timeline of milestones in fuel cell design. The leftmost curve is the performance curve of the first practical H2/O2 fuel cell, built by Mond and Langer in 1889 (Mond and Langer, 1889). The electrodes consisted of thin porous leafs of Pt covered with Pt black particles with sizes of 0.1 lam. The electrol)de was a porous ceramic material, earthenware, that was soaked in sulfuric acid. The Pt loading was 2 mg cm and the current density achieved was about 0.02 A cm at a fuel cell voltage of 0.6 V. The next curve in Figure I.6a marks the birth of the PEFC, conceived by Grubb and Niedrach (Grubb and Niedrach, 1960). In this cell, a sulfonated cross-linked polystyrene membrane served as gas separator and proton conductor. However, the proton conductivity of the polystyrene PEM was too low and the membrane lifetime was too short for a wider use of this cell. It needed the invention of a new class of polymer electrolytes in the form of Nafion PFSA-type PEMs to overcome these limitations.

Therefore, a number of new forms of polymer electrolyte have been developed. Although in practice a continuum of types exists, it is sometimes useful to group these polymer electrolytes according to electrolyte composition and morphology ... 

Another factor also contributed to the appearance of new concepts in electrochemistry in the second half of the twentieth century The development and broad apphca-tion of hthium batteries was a stimulus for numerous investigations of dilferent types of nonaqueous electrolytes (in particular, of sohd polymer electrolytes). These batteries also initiated investigations in the held of electrochemical intercalation processes. 

The concepts of modified electrodes have contributed tremendously to battery and fuel cell development. For example, a schematic of an interesting new type of fuel cell, the polymer electrolyte tuel cell, is shown in Figure 13.9. Hydrogen gas is supplied to the anode and is oxidized via... 

In this chapter, we describe three different systems with which to construct electro- and photo-functional molecular assemblies on electrode surfaces. The first is the bottom-up fabrication of redox-conducting metal complex oligomers on an electrode surface and their characteristic redox conduction behavior, distinct from conventional redox polymers.11-13 The second is a photoelectric conversion system using a porphyrin and redoxconducting metal complex.14 The third is the use of a cyanobacterial photosystem I with molecular wires for a biophotosensor and photoelectrode.15 16 These systems will be the precursors of new types of molecular devices working in electrolyte solution. 

Yi et al. reported a new type of PVDF membrane prepared by blending two very different polymers, a PVDF fluoropolymer such as Kynar with a sulfonated poly-electrolyte. The new membrane is inexpensive and displayed good performance and durability based on 1,000-h test data. 

Polymers that function as solid electrolytes are a subclass by themselves and are known as polymer electrolytes [27,29]. Besides the advantage of flexibility, polymers can also be cast into thin films and since thin films while minimizing the resistance of the electrolyte also reduces the volume and the weight, use of polymer electrolytes can increase the energy stored per unit weight and volume. In view of these attractive features, there has been considerable focus in recent years on the development of both inorganic and organic polymers as electrolytes for ion transport. This article deals with the recent developments in this area with emphasis on the new types of polymeric systems that have been used as polymer electrolytes. 

In addition to the salts shown in Table 2, a new type of lithium salt containing a spirocyclic borate anion has recently been synthesized (Scheme 2) [102]. This salt was shown to possess good electrochemical and thermal stability. However, there are no reports on its use in polymer electrolytes. 

The discovery and the characterization of ionically conducting polymeric membranes (see Chapters 1 and 2) have provided the interesting possibility of developing new types of lithium batteries having a thin-layer, laminated structure. Various academic and industrial laboratories [1-5] are presently engaged in the development of this revolutionary type of battery, i.e. the so-called Lithium Polymer Battery (LPB). The key component of the LPB is the polymeric ionic membrane which acts both as electrolyte and separator furthermore, the membrane can be easily fabricated in the form of a thin film (typically 50 jum thickness) by a number of convenient casting techniques. 

This chapter reviews the chemistries, properties, and commercial uses water-containing ionicaUy conductive polymer systems. In medical applications, these polymers serve as the conductive interface between the patient s skin and the medical equipment. These electrolyte systems are commercially produced in gel, paste, or sheet form using either natural or synthetic polymers. Regardless of the physical form, these systems are typically formulated to a conductivity range of 10 to 10 S cm to provide acceptable performance. A new plication of this type of polymer is reported recently in the prevention of steel rebar corrosion in concrete structures. 

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