Lithium polysulfide

Sulfur is known to be easily reducible in nonaqueous solvents and its reduction products exist at various levels of reduction of polysulfide radical anions (S . ) and dianions (Sm2 ) 173], Recently Be-senhard and co-workers [74] have examined the effect of the addition of polysulfide to LiC104-PC. Lithium is cycled on an Ni substrate with Qc=2.7 C cm 2 and cycling currents of 1 mA cm. The cycling efficiency in PC with polysulfide is higher than that without an additive. The lithium deposition morphology is compact and smooth in PC with added polysulfide, whereas it is dendritic in PC alone. 

More recently, 84 may have been identified by ESR spectroscopy of solutions of Li2S ( >6) in DMF at 303 K. The lithium polysulfide was prepared from the elements in liquid ammonia. These polysulfide solutions also contain the trisulfide radical anion ( 2.0290) but at high sulfur contents a second radical at g=2.031 (Lorentzian lineshape) was formed which was assumed to be 84 generated by dissociation of octasulfide dianions see Eq. (32) [137],... 

Liquid ammonia solutions of lithium polysulfides have been characterized by Dubois et al. [18]. The least reduced polysulfide was shown to be 8 (not found previously in aquo) lying in a strongly temperature-dependent equilibrium with the radical 83 . 

Dubois P, Lelieur JP, Lepoutre G (1988) Identification and characterization of lithium polysulfides in solution in liquid ammonia. Inorg Chem 27 73-80... 

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Potassium also differs from sodium, and especially from lithium, in the greater stability of its salts of polarizable polyatomic anions, such as peroxide, superoxide, azide, polysulfide,polyhalides,etc. The rubidium and cesium salts, on the other hand, are even more stable. 

Lithium aluminum hydride is a convenient reagent for reduction of nitro compounds, nitriles, amides, azides, and oximes to primary amines. Catalytic hydrogenation works also. Aromatic nitro compounds are reduced best by reaction of a metal and aqueous acid or with ammonium or sodium polysulfides (see Section 23-12B). Reduction of /V-substituted amides leads to secondary amines. 

Diethyl mercaptoacetal has been prepared by treating diethyl bromoacetal with potassium hydrosulfide 3 by the reduction of 1,1,11 -tetraethoxyethyl disulfide 3 with lithium aluminum hydride by reduction of 1,1-diethoxyethyl benzyl sulfide,3 41,1,1/,1/-tetraethoxyethyl disulfide,3 and 1,1,1, 1 -tetracthoxyethyl polysulfide 3 with sodium and liquid ammonia. The method described is adapted from the last-named preparation. Dimethyl mercaptoacetal has been prepared by the same methods.3... 

Concerning the composition of alkali polysulfide, the yield of thiolane 7 suffered none in utilizing alkali polysulfide prepared from hydrated sodium sulfide or lithium or potassium sulfide rather than anhydrous sodium sulfide. When the ratio of sulfur to hydrated sodium sulfide was 8 1 or greater, the thiolane 7 resulted whereas at a ratio of 4 1, or using commercial Na, several components containing both sulfur and carbon were detected in me solid proauct. 

Caution. All reactions involving solutions of lithium polysulfides or polyselenides generate compounds that are malodorous and toxic to varying degrees and consequently must be performed in a well-ventilated fume hood. Li[BEt H] can ignite on contact with water, alcohols, or air. This reagent should be handled only under an inert atmosphere. 

What makes the sodium-sulfur cell possible is a remarkable property of a compound called beta-alumina, which has the composition NaAlnOiy. Beta-alumina allows sodium ions to migrate through its structure very easily, but it blocks the passage of polysulfide ions. Therefore, it can function as a semipermeable medium like the membranes used in osmosis (see Section 11.5). Such an ion-conducting solid electrolyte is essential to prevent direct chemical reaction between sulfur and sodium. The lithium-sulfur battery operates on similar principles, and other solid electrolytes such as calcium fluoride, which permits ionic transport of fluoride ion, may find use in cells based on those elements. 

Studebaker identified the use of lithium aluminium hydride as a chemical probe.Under the right conditions it cleaves poly- and disulfide bonds, leaving the monosulfide intact. Lithium aluminum hydride reacts with polysulfides in an etheral solvent at moderate temperatures and then with a weak acid, the terminal groups are liberated as thiols and interior sulfur atoms are converted to hydrogen sulfide.Lithium... 

Similarly Gregg and Katrenick found that phenyl lithium will cleave polysulfides and disulfides but not monosulfide linkages. 

In the presence of metallic lithium the reaction of 8 with 1,4-dichlorobenzene yields a linear poly(l,4-phenylene polysulfide) in which the sulfur content could be 3 sulfur atoms per phenylene unit (M as high as 12,000) [Ilia]. 

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