New types of solid electrolytes

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). 

This chapter reviews a new type of solid electrolyte low-temperature fuel cell, the alkaline membrane fuel cell. The principles and main components of this fuel cell technology are described, with a major focus on the electrocatalysts for both electrodes. Finally, the latest published results on operation of the first developed alkaline membrane fuel cells are reviewed. 

In this chapter a new type of solid electrolyte membrane for low-temperature fuel cell application, the anion exchange membrane (AEM), is reviewed. The properties, advantages, and challenges of the anion exchange membranes are discussed. 

Rare earth oxy-apatites are also attracting considerable interest as a new type of solid electrolytes possessing a high oxide-ion conductivity at intermediate temperatures [22-35]. In contrast to traditional fluorite- and perovskite-type oxide electrolytes conducting via oxide ion vacancies, the high ion conductivity of the apatites is provided by the transport of interstitial oxide ions [29-34], This is caused by peculiarities of the apatite structure that tolerates different structural defects such as cation vacancies and oxygen interstitial sites. 

Kudo T (1997) Survey of types of solid electrolytes. In Gellings PJ, Bouwmeester HIM (eds) Solid state chemistry CRC handbook. CRC Press, Boca Raton/ New YOTk/London/Tokyo... 

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. 

A new oxide ceramic solid electrolyte is so-called 3-aluminum oxide, a compound of AI2O3 with 5 to 10% Na20. Materials of this type are currently being evaluated in sodium-sulfur batteries. 

Irrespective of these controversies, research in this intriguing area is crucially important from both fundamental and applied points of view. For instance, solid electrolytes and mixed conductors with mobile AP + cations may find applications in new types of rechargeable battery, and also in the aluminum industry alkaline-earth cation conductors may be used, in particular, for precise humidity control in gaseous media and for CO2 sequestration. This chapter includes a brief introduction to the field, with emphasis placed primarily on the authors own studies. Although many aspects of materials electrochemical behavior require detailed investigation and further validation, the chapter provides an excellent overview of the phases where multivalent cation conduction may occur. 

Inaba. Y, Tamura, S. and Imanaka, N. (2007) New type of sulfur dioxide gas sensor based on trivalent Al ion-conducting solid electrolyte. Solid State Ionics, 179, 1625-7. 

Oda, A., Imanaka, N. and Adachi, G.-Y. (2003) New type of nitrogen oxide sensor with multivalent cation- and anionconducting solid electrolytes. Sens. Actuators B, 93, 229-32. 

FIGURE 2.14 Response/recovery time of the hydrogen sensor based on the (NH4)4Ta,oW03o solid electrolyte (Cj = 10 ppm Cj = 100,000 ppm). (From Zhuiykov, S., Hydrogen sensor based on a new type of proton conductive ceramic, Ira. J. Hydrogen Energy 21 (1996) 749-759. With permission.)... 

The electrolyte phase of electrochemical cells is an ionic conductor and can be a liquid, solid, or gas. The development of new types of electrolytes will open up attractive opportunities for new and improved electrochemical processes and devices. 

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. 

As for electrochemical NO sensor, liquid electrolyte type has been developed for a long time, but these days solid type, which solid electrolyte is adopted instead of electrolytic liquid, is widely studied. BalNOalj was used as a solid electrolyte in the beginning of investigations[3], but there were some disadvantages like EMF drifts and necessity of reference gas. A new sensor composed of p/p"-Al203 as a solid electrolyte and NaN03 as an auxiliary... 

For this reason, the search for solid oxide fuel cells operable at lower temperatures has been primarily via the development of new types of materials for the electrolyte and the electrodes that could work at these temperatures. 

In 1962, a research group in the American company Allis-Chalmers started developing a new type of hydrogen-oxygen fuel cell with an alkaline electrolyte. The distinguishing feature of this cell was to use, instead of a fi eely flowing liquid electrolyte (KOH solution or melt, as described above), a quasi-solid electrolyte in the form of potassium hydroxide solution immobilized in an asbestos matrix. Asbestos... 

Lampert and coworkers [36] have used a modified amorphous PEO-LiCFaSOs electrolyte for the realization of WO3 laminated windows using several types of counter-electrodes, such as niobium oxide, nickel oxide and a new class of solid redox polymerization electrodes [63]. These latter electrodes have an advantage over inorganic layers in that they can be tailored to the electrochromic material and ion specifically. Figure 8.18 illustrates the optical transmittance of a EW made of WOa/modified a-PEO/ion storage polymer [63]. 

Having discussed in Sections II and III concentration and mobility, which influence the conductivity of solid electrolytes, a compilation of solid ionic conductors will be given in this section. This compilation does not presume to be complete because new solid electrolytes are discovered and developed continuously. In Fig. 4, the conductivities of some of the most important ones are shown as a function of temperaure and reciprocal temperature. The conductivity of liquid sulfuric acid is included for comparison. In the following, several important solid electrolytes will be treated according to the type of mobile ions that cause the ionic conductivity. 

Gels, which take the f m of a solid but contain a large amount of solvent within, are thought to bdiave like a liquid microscopically. Therefore, it was expected that molecular gels contaiiiing an electrolyte function as a new type of ionic conduct( s and that molecular gels having a redox moiety function as a new type of potential electrochromic materials with dimensional stability. 

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. 

Since the 1980 s, a new type of humidity sensor, based on a solid electrolyte, has been under development. The sensor uses a protonic conductor as a base component and makes a galvanic cell of a water vapor gas concentration type. When the characteristics of this new type of sensor are compared with conventional humidity sensors, two representative advantages of this sensor are seen. The sensor output is an EMF change, and is suitable for continuous operation with a fast response. The sensor can operate at higher temperatures, because the solid electrolyte is stable even at elevated temperatures. These features are expected to accelerate the development of this type of sensor. The base material is a perovskite-type strontium cerate SrCeOa. The pure cerate is not a protonic conductor. 

The PECVD technique appears to be a unique method that allows for the implementation of Li-ion batteries with particularly sophisticated architecture. A new type of 3D microbatteries with anode or cathode post-arrays has been recently developed in the Tolbert Lab at University of California (Los Angeles). However, such systems require a solid electrolyte in the form of conformal coatings that will evenly cover the high aspect ratio electrodes. Plasma deposited polyethyleneoxide-hke electrolyte films, which are electronic insulating and can be intercalated with lithium ions, have been chosen to this end. Currently, these films are intensively investigated (Dudek, 2011). 

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