Lithium metals

When lithia is submitted to the action of the Voltaic pile, it is decomposed with the same phenomena as potassa and soda a brilliant white and highly combustible metallic substance is separated, which may be called lithium, the term lithia being applied to its oxide. The properties of this metal have not hitherto been investigated, in consequence of the difficulty of procuring any quantity of its oxide. 

Bunsen and Mathiesen in 1854 prepared lithium in a suflidently large quantity for determination of the properties of the element. They fused lithium chloride in a porcelain crudble and conducted current from six carbon-zinc cells, connected in series, through the melt. 

In the earth crust Hthium is enriched in granitic pegmatites and occurs as an essential component in some twenty minerals. The following four minerals are common  

Large deposits of spodumene have been found in Manono in the Democratic Republic of Congo and of petalite and lepidoHte in Bikita in Zimbabwe. Investigations of pegmatite deposits in Greenbushes, Western Australia, have also revealed large reserves of spodumene. 

A pegmatite at Bernic Lake, Manitoba in Canada is mined for tantalum, niobium and lithium. A lepidolite in the pegmatite is, in addition, the only known commercial source of the element rubidium. In North Carolina, a rich Hthium source is known as the tin-spodumene belt . The ore was used for production of Hthium carbonate until 1998, when the last mine there was closed. 

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Anionic polymerization of vinyl monomers can be effected with a variety of organometaUic compounds alkyllithium compounds are the most useful class (1,33—35). A variety of simple alkyllithium compounds are available commercially. Most simple alkyllithium compounds are soluble in hydrocarbon solvents such as hexane and cyclohexane and they can be prepared by reaction of the corresponding alkyl chlorides with lithium metal. Methyllithium [917-54-4] and phenyllithium [591-51-5] are available in diethyl ether and cyclohexane—ether solutions, respectively, because they are not soluble in hydrocarbon solvents vinyllithium [917-57-7] and allyllithium [3052-45-7] are also insoluble in hydrocarbon solutions and can only be prepared in ether solutions (38,39). Hydrocarbon-soluble alkyllithium initiators are used directiy to initiate polymerization of styrene and diene monomers quantitatively one unique aspect of hthium-based initiators in hydrocarbon solution is that elastomeric polydienes with high 1,4-microstmcture are obtained (1,24,33—37). Certain alkyllithium compounds can be purified by recrystallization (ethyllithium), sublimation (ethyllithium, /-butyUithium [594-19-4] isopropyllithium [2417-93-8] or distillation (j -butyUithium) (40,41). Unfortunately, / -butyUithium is noncrystaUine and too high boiling to be purified by distiUation (38). Since methyllithium and phenyllithium are crystalline soUds which are insoluble in hydrocarbon solution, they can be precipitated into these solutions and then redissolved in appropriate polar solvents (42,43). OrganometaUic compounds of other alkaU metals are insoluble in hydrocarbon solution and possess negligible vapor pressures as expected for salt-like compounds. 

The first successhil use of lithium metal for the preparation of a i7j -l,4-polyisoprene was aimounced in 1955 (50) however, lithium metal catalysis was quickly phased out in favor of hydrocarbon soluble organ olithium compounds. These initiators provide a homogeneous system with predictable results. Organ olithium initiators are used commercially in the production of i7j -l,4-polyisoprene, isoprene block polymers, and several other polymers. 

Thin films (qv) of lithium metal are opaque to visible light but are transparent to uv radiation. Lithium is the hardest of all the alkaH metals and has a Mohs scale hardness of 0.6. Its ductiHty is about the same as that of lead. Lithium has a bcc crystalline stmcture which is stable from about —195 to — 180°C. Two allotropic transformations exist at low temperatures bcc to fee at — 133°C and bcc to hexagonal close-packed at — 199°C (36). Physical properties of lithium are Hsted ia Table 3. 

Lithium metal can also be produced by electrolysis in nonprotic solvents. Other methods based on reduction by metals, eg, aluminum or siHcon from the chloride or by magnesium from the oxide, have not had practical commercial appHcation. 

Economic Aspects. Lithium metal is available commercially in ingots, special shapes, shot, and dispersions. Ingots are sold in 0.11-, 0.23-, 0.45-, and 0.91-kg sizes. Special shapes include foil, wire, and rod. Lithium is available in hermetically sealed copper cartridges and in sealed copper tubes for use in treating molten copper and copper-base alloys. Shot is sold in 1.19—4.76 mm (16—4 mesh) sizes. Lithium dispersions (30% in mineral oil) of 10—50-p.m particle size are used primarily in organic chemical reactions. Dispersions in other solvents and of other size fractions can be suppHed. 

The price of lithium metal decreased drastically between 1925 ( 143/kg) and 1965 ( 16.50/kg), but because of increased energy and chemicals costs, and other inflationary pressures, the price has actually increased. Prices for lithium ingots ( /kg) were 72.05 in 1993. 

Uses. The largest use of lithium metal is in the production of organometaUic alkyl and aryl lithium compounds by reactions of lithium dispersions with the corresponding organohaHdes. Lithium metal is also used in organic syntheses for preparations of alkoxides and organosilanes, as weU as for reductions. Other uses for the metal include fabricated lithium battery components and manufacture of lithium alloys. It is also used for production of lithium hydride and lithium nitride. 

Lithium is used in metallurgical operations for degassing and impurity removal (see Metallurgy). In copper (qv) refining, lithium metal reacts with hydrogen to form lithium hydride which subsequendy reacts, along with further lithium metal, with cuprous oxide to form copper and lithium hydroxide and lithium oxide. The lithium salts are then removed from the surface of the molten copper. 

Lithium Amide. Lithium amide [7782-89-0], LiNH2, is produced from the reaction of anhydrous ammonia and lithium hydride. The compound can also be prepared by the removal of ammonia from solutions of lithium metal in the presence of catalysts (54). Lithium amide starts to decompose at 320°C and melts at 375°C. Decomposition of the amide above 400°C results first in lithium imide, Li2NH, and eventually in lithium nitride, Li N. Lithium amide is used in the production of antioxidants (qv) and antihistamines (see HiSTAMlNE AND HISTAMINE ANTAGONISTS). 

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

Lithium Nitride. Lithium nitride [26134-62-3], Li N, is prepared from the strongly exothermic direct reaction of lithium and nitrogen. The reaction proceeds to completion even when the temperature is kept below the melting point of lithium metal. The lithium ion is extremely mobile in the hexagonal lattice resulting in one of the highest known soHd ionic conductivities. Lithium nitride in combination with other compounds is used as a catalyst for the conversion of hexagonal boron nitride to the cubic form. The properties of lithium nitride have been extensively reviewed (66). 

Lithium acetyhde also can be prepared directly in hquid ammonia from lithium metal or lithium amide and acetylene (134). In this form, the compound has been used in the preparation of -carotene and vitamin A (135), ethchlorvynol (136), and (7j--3-hexen-l-ol (leaf alcohol) (137). More recent synthetic processes involve preparing the lithium acetyhde in situ. Thus lithium diisopropylamide, prepared from //-butyUithium and the amine in THF at 0°C, is added to an acetylene-saturated solution of a ketosteroid to directly produce an ethynylated steroid (138). 

C. It can be obtained from its hahde-free solutions in cyclohexane and ethylether by vacuum distUlation to remove the ether. The usual preparative method is by reaction of chloro- or bromobenzene and lithium metal in ethyl ether or in a mixture of ethyl ether and cyclohexane. 

Lithium metal in tetrahydrofuran can also be used as the coupling reagent, and unsymmetrical ditins can be prepared when the reaction is conducted in stages (162,163). 

Cationic polymerization with Lewis acids yields resinous homopolymers containing cycHc stmctures and reduced unsaturation (58—60). Polymerization with triethyl aluminum and titanium tetrachloride gave a product thought to have a cycHc ladder stmcture (61). Anionic polymeriza tion with lithium metal initiators gave a low yield of a mbbery product. The material had good freeze resistance compared with conventional polychloroprene (62). 

Lithium. Several processes for lithium [7439-93-2], Li, metal production have been developed. The Downs cell with LiCl—KCl electrolyte produces lithium ia much the same manner as sodium is produced. Lithium metal or lithium—aluminum alloy can be produced from a mixture of fused chloride salts (108). Granular Li metal has been produced electrochemically from lithium salts ia organic solvents (109) (see LiTHlUM AND LITHIUM compounds). 

Birch reduction of indole with lithium metal in THF in the presence of trimethylsilyl chloride followed by oxidation with p-benzoquinone gave l,4-bis(trimethylsilyl)indoIe (106). This is readily converted in two steps into l-acetyl-4-trimethylsilylindole. Friedel-Crafts acylation of the latter compound in the presence of aluminum chloride yields the corresponding 4-acylindole (107) (82CC636). 

Regioselective cleavage of dibenzofuran derivatives has been achieved with lithium metal, as exemplified by the preparation of 3-methyl-2-phenylphenol (108) (80S634). 

A dry 1-L, three-necked, round-bottomed flask equipped with a large Teflon-covered magnetic stirring bar, a thermometer, and a dry ice condenser (Note 1) is flushed with argon (Note 2), then capped with a serun stopper and subsequently maintained under a positive pressure of argon (Note 3). A 30 dispersion of lithium metal (in mineral oil) containing 1% sodium (13.9 g, 2.00 g-atom of lithium) (Note 4) is rapidly weighed and transferred to the flask. 

As soon as the receiver containing the methyl 11 thiurn solution has been removed and stoppered, the residual solids in the reaction flask and the filtration apparatus should be rinsed Into another receiver with anhydrous ether under an atmosphere of argon or nitrogen. The ether slurry of solids, which may contain some unchanged lithium metal, should be treated cautiously in a hood with t-butyl alcohol to consume any residual lithium metal before the mixture is discarded. 

A possible solution to this problem is to use an electrolyte, such as a solid polymer electrolyte, which is less reactive with lithium metal [3]. Another simple solution is the lithium-ion cell. 

One criterion for the anode material is that the chemical potential of lithium in the anode host should be close to that of lithium metal. Carbonaceous materials are therefore good candidates for replacing metallic lithium because of their low cost, low potential versus lithium, and wonderful cycling performance. Practical cells with LiCoOj and carbon electrodes are now commercially available. Finding the best carbon for the anode material in the lithium-ion battery remains an active research topic. 

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