Molten Salts as Electrolytes

The last entry of table 1, tetrahexylammonium benzoate, is an example of the use of molten salts as electrolytes. In this particular case, the salt is liquid at room temperature, but it has been reported that tetrabutylammonium nitrate at 150° can be used for polarographic and preparative work 7Sa-> (oxidation of polycyclic aromatic hydrocarbons). The use of molten salts as SSE s is of great interest because of the high conductivities of such media as compared to conventional SSE s and deserves further studies. 

A battery which uses room temperature molten salts as electrolyte could... 

U.S. Air Force Academy in 1961. He was an early researcher in the development of low-temperature molten salts as battery electrolytes. At that time low temperature meant close to 100 °C, compared to many hundreds of degrees for conventional molten salts. His work led directly to the chloroaluminate ionic liquids. 

A series of experiments have been undertaken to evaluate the relevant thermodynamic properties of a number of binary lithium alloy systems. The early work was directed towards determination of their behavior at about 400 °C because of interest in their potential use as components in molten salt batteries operating in that general temperature range. Data for a number of binary lithium alloy systems at about 400 °C are presented in Table 1. These were mostly obtained by the use of an experimental arrangement employing the LiCl-KCl eutectic molten salt as a lithiumconducting electrolyte. 

The alkali metals are the most violently reactive of all the metals. They are too easily oxidized to be found in the free state in nature and cannot be extracted from their compounds by ordinary chemical reducing agents. The pure metals are obtained by electrolysis of their molten salts, as in the electrolytic Downs process (Section 12.13) or, in the case of potassium, by exposing molten potassium chloride to sodium vapor ... 

It has been pointed out that metals residing below the position held by manganese (and, therefore, much below hydrogen) in the electrochemical series (Table 6.11) cannot be electrodeposited from aqueous solutions of their salts. These metals are called base metals or reactive metals and can be electrodeposited only from nonaqueous electrolytes such as solutions in organic solvents and molten salts. As with an aqueous electrolyte, there is a minimum voltage which is required to bring about the electrolysis of a molten salt. 

Mischmetal is produced commercially by electrolysis, The usual starting ingredient is the dehydrated rare earth chloride produced from monazite or bastnasite. The mixed rare earth chloride is fused in an iron, graphite, or ceramic crucible with the aid of electrolyte mixtures made up of potassium, barium, sodium, or calcium chlorides. Carbon anodes are immersed in the molten salt. As direct current flows through the cell, molten mischmetal huilcls up in the bottom of the crucible. This method is also used to prepare lanthanum and cerium metals. 

This chapter deals with critical phenomena in simple ionic fluids. Prototypical ionic fluids, in the sense considered here, are molten salts and electrolyte solutions. Ionic states occur, however, in many other systems as well we quote, for example, metallic fluids or solutions of complex particles such as charged macromolecules, colloids, or micelles. Although for simple atomic and molecular fluids thermodynamic anomalies near critical points have been extensively studied for a century now [1], for a long time the work on ionic fluids remained scarce [2, 3]. Reviewing the rudimentary information available in 1990, Pitzer [4] noted fundamental differences in critical behavior between ionic and nonionic fluids. 

Ionic fluids such as molten salts and electrolyte solutions have always been of central interest in Chemical Physics, Physical Chemistry and many applied fields such as electrochemistry, chemical engineering or the geosciences. It is the aim of this review to connect the knowledge about structure and thermodynamic properties of ionic fluids and electrolyte solutions with that of the ILs. Liquid-liquid phase transition of ionic solutions are the main topic of this paper. 

As the molten salt is electrolytic. Hot Corrosion processes involve electrochemical reactions like oxidation of the metal and reduction of melt components and dissolved gases. Hence, many of investigations of Hot Corrosion have been done by electrochemical techniques, mostly combined with conventional corrosion... 

The electrolyte usually consists of a solution of salts, acids or bases in water or protic solvents, such as alcohols, carboxylic acids, etc. [1]. Pure solvents, too, can act as electrolytes if enough conductivity by autodissociation is produced (water, methanol, ethanol, etc.). Moreover, molten salts constitute electrolytes with sometimes extremely high conductivity. It is important to state that the electrolyte should be free from any electronic conductivity othervdse no electrochemical reaction will occur at the electrode/electrolyte interface. 

Garcia B. LavaUee S. Perron G. Michot C. Armand M., Room temperature molten salts as lithium battery electrolyte, Electrochim. Acta, 2004, 49 4583-4588. 

A molten salt battery is a primary or secondary battery that uses a molten salt as its electrolyte. Molten salt batteries are a class of primary cell and secondary cell high-temperature electric battery. These types of batteries are used where high energy density and high power density are required. Their energy density and power density give them potential for use in electric vehicles. 

Although this Chapter does not consider electrolytes in detail, reference will be made to Lumsden s book because he treats molten salts as examples of high-melting substances. 

Molten carbonate fuel cells (MCFC) are composed of a porous nickel-based anode, a porous nickel oxide-based cathode and molten carbonate salts as electrolyte within a porous lithium aluminate matrix. Molten carbonate fuel cells with internal reforming can be fed directly with light hydrocarbons rich gas such as... 

Garcia, B., Lavallee, S., Perron, G., Michot, C. Armand, M. (2004). Room tempierature molten salts as lithium battery electrolyte., Electrochim. Acta 49 4583-4588. 

When natural gas is considered as a possible fuel, an increase in the rate of the electrode reactions is needed. Since catalysts are either very expensive or unknown, temperature is raised to lower the overpotential. Since the products of oxidation of natural gas are carbon dioxide and water, these will always be present in the gas mixture over the cell. An equilibrium between the gases and the molten salt electrolyte will be established, and part of the electrolyte will be converted to carbonate, regardless of the nature of the original anion. Therefore, it seems reasonable to use molten carbonates, not other salts, as electrolytes. On the other hand, since carbonates dissociate at high temperatures to give carbon dioxide, it is necessary to keep the partial pressure of CO2 above the cell at such a value as to retard any change in the composition of the electrolyte. Both the fuel gas and the air are premixed with carbon dioxide before being fed to the fuel cell. 

While small single crystals of many compounds have been produced electrolytically from molten salts as well as aqueous solutions, scaling up to large size has generally been difficult. The subject of using molten salt electrolysis for crystal growth was reviewed by Feigelson (3). 

B. Garcia, S. LavaUee, G. Perron, C. Michot and M. Armand, Room temperature molten salts as lithimn battery electrolyte, Electrochim. Acta 49, 2004, 4583-A588. 

The principal use of AIF. is as a makeup ingredient in the molten cryoflte, Na.. AIF AI2O2, bath used in aluminum reduction cells in the HaH-Haroult process and in the electrolytic process for refining of aluminum metal in the Hoopes cell. A typical composition of the molten salt bath is 80—85%... 

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