High-energy-density batteries

High energy density batteries with long shelf life, developed originally for military use, are based on lithium and thionyl chloride. These batteries are used ia backup or standby power sources for computer, missile, and telephone systems (191,192). 

Graphite acid salts have been considered in terms of possible practical applications. Their potential as useful electrodes in high-energy-density batteries has been reviewed (AS), as well as their potential usefulness as chemical reagents (B14). 

Phase behavior 1n concentrated aqueous electrolyte systems is of interest for a variety of applications such as separation processes for complex salts, hydrometal 1urgical extraction of metals, interpretation of geological data and development of high energy density batteries. Our interest in developing simple thermodynamic correlations for concentrated salt systems was motivated by the need to interpret the complex solid-liquid equilibria which occur in the extraction of sodium nitrate from complex salt mixtures which occur in Northern Chile (Chilean saltpeter). However, we believe the thermodynamic approach can also be applied to other areas of technological interest. 

A solvent with an ideal electrochemical stability for a high-energy-density battery purpose should possess high oxidation and low reduction potentials at the same time. Table 5 lists selected electrochemical... 

Robert West was bom in New Jersey and educated at Cornell University (B.A.) and Harvard University (A.M., Ph.D.). For the past 45 years he has been a faculty member in the chemistry department at the University of Wisconsin, where he is now E. G. Rochow Professor and Director of the Organosilicon Research Center. His many awards include the Frederick Stanley Kipping Award, the Wacker silicone prize, the Alexander von Humboldt Award, and the main group chemistry medal. He has published more than 600 scientific papers, mostly in the area of silicon chemistry. Major discoveries in his laboratories include the first soluble polysilanes (1978), the silicon-silicon double bond (1981), the first stable silylenes (1994), and electrically conducting organosilanes for high energy density batteries (2000). He is an airplane pilot and a mountaineer, with numerous first ascents in Canada and Alaska. 

High energy density batteries are a crucial need as modern electronics progresses and moves more and more toward miniaturization. Many novel battery systems require the use of nonaqueous electrolyte systems because important new developments in this field are based on active metal electrodes (eg, Li and Li-C intercalation compounds). 

In the literature of recent years, we indeed see more and more publications on the study and development of novel nonaqueous high energy density battery systems, nonaqueous electro-organic synthesis, and mechanistic studies. This parallels worldwide efforts to commercialize nonaqueous lithium and lithium-carbon batteries. Hence, it is important to gather from time to time the knowledge accumulated in these areas, to update the literature and provide the increasing number of people working in this field with a comprehensive compendium on the practical and theoretical aspects of nonaqueous electrochemistry. 

The first comprehensive review of electrochemical windows of nonaqueous systems, by Mann, appeared 20 years ago in the series Electroanalytical Chemistry [13], edited by A. J. Bard. In general, the picture provided by Mann is quite reliable. However, over the years, a vast amount of work has been done with nonaqueous systems, particularly within the framework of basic studies related to high energy density batteries and the application of novel spectroelectrochemi-cal tools. The accumulated data provide a more precise picture of the various reactions that limit the electrochemical window of commonly used systems. 

Although these nonaqueous solvents are highly polar and thus may be attractive as media for nonaqueous electrochemistry, their electrochemical window is very narrow, since their cathodic potential limit is high (2.5-4 V versus Li/ Li+). Hence, their major importance remains as cathodic active materials in primary, high energy density batteries based on active metal (Li, Mg, Ca) anodes. 

A major part of the work with nonaqueous electrolyte solutions in modern electrochemistry relates to the field of batteries. Many important kinds of novel, high energy density batteries are based on highly reactive anodes, especially lithium, Li alloys, and lithiated carbons, in polar aprotic electrolyte systems. In fact, a great part of the literature related to nonaqueous electrolyte solutions which has appeared during the past two decades is connected to lithium batteries. These facts justify the dedication of a separate chapter in this book to the electrochemical behavior of active metal electrodes. 

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