Lithium, Metallic

CH3)2N]3P0. M.p. 4°C, b.p. 232"C, dielectric constant 30 at 25 C. Can be prepared from dimethylamine and phosphorus oxychloride. Used as an aprotic solvent, similar to liquid ammonia in solvent power but easier to handle. Solvent for organolithium compounds, Grignard reagents and the metals lithium, sodium and potassium (the latter metals give blue solutions). 

Casassa S and Pisani C 1995 Atomic-hydrogen interaction with metallic lithium an ab /M/o embedded-cluster study Phys. Rev. B 51 7805... 

The table contains vertical groups of elements each member of a group having the same number of electrons in the outermost quantum level. For example, the element immediately before each noble gas, with seven electrons in the outermost quantum level, is always a halogen. The element immediately following a noble gas, with one electron in a new quantum level, is an alkali metal (lithium, sodium, potassium, rubidium, caesium, francium). 

A useful alternative to catalytic partial hydrogenation for converting alkynes to alkenes IS reduction by a Group I metal (lithium sodium or potassium) m liquid ammonia The unique feature of metal-ammonia reduction is that it converts alkynes to trans alkenes whereas catalytic hydrogenation yields cis alkenes Thus from the same alkyne one can prepare either a cis or a trans alkene by choosing the appropriate reaction conditions... 

Heating metallic lithium in a stream of gaseous ammonia gives lithium amide [7782-89-0] LiNH2, which may also be prepared from Hquid ammonia and lithium in the presence of platinum black. Amides of the alkaH metals can be prepared by double-decomposition reactions in Hquid ammonia. For example... 

In the lithium-ion approach, the metallic lithium anode is replaced by a lithium intercalation material. Then, tw O intercalation compound hosts, with high reversibility, are used as electrodes. The structures of the two electrode hosts are not significantly altered as the cell is cycled. Therefore the surface area of both elecftodes can be kept small and constant. In a practical cell, the surface area of the powders used to make up the elecftodes is nomrally in the 1 m /g range and does not increase with cycle number [4]. This means the safety problems of AA and larger size cells can be solved. 

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. 

Lithium/carbon cells are typically made as coin cells. The lithium/carbon coin cell consists of several parts, including electrodes, separator, electrolyte and cell hardware. To construct a coin cell, we first must prepare each part separately. Successful cells will lead to meaningful results. The lithium/carbon coin cells used metallic lithium foil as the anode and a carbonaceous material as the cathode. The metallic lithium foil, with a thickness of 125 pm, was provided by Moli Energy (1990) Ltd.. Idie lithium foil is stored in a glove-box under an argon atmosphere to avoid oxidation. 

A lithium cluster in the micropores of the carbon sample has a very similar environment as lithium atoms in metallic lithium. Hence, we observe long low-voltage plateaus on both discharge and charge for lithium insertion in the microporous carbon. 

Highly fluonnated alkanes are also reduced by alkali metals Lithium amalgam converts polytetrafluoroethyleneto acarbon polymer composed of monolayer nbbons of six membered rings with hthium atoms bound to the edges [i]... 

Reactivity and yields are greatly enhanced by the presence of 0.5-1% Na in the Li. The reaction is also generally available for the preparation of metal alkyls of the heavier Group 1 metals. Lithium aryls are best prepared by metal-halogen exchange using LiBu" and an aryl iodide, and transmetalation is the most convenient route to vinyl, allyl and other unsaturated derivatives ... 

Consider a crystal of metallic lithium. In its crystal lattice, each lithium atom finds around itself eight nearest neighbors. Yet this atom has only one valence electron, so it isn t possible for it to form ordinary electron pair bonds to all of these nearby atoms. However, it does have four valence orbitals available so its electron and the valence electrons of its neighbors can approach quite close to its nucleus. Thus each lithium atom has an abundance of valence orbitals but a shortage of bonding electrons. 

There are some indications that the situation described above has been realized, at least partially, in the system styrene-methyl methacrylate polymerized by metallic lithium.29 29b It is known51 that in a 50-50 mixture of styrene and methyl methacrylate radical polymerization yields a product of approximately the same composition as the feed. On the other hand, a product containing only a few per cent of styrene is formed in a polymerization proceeding by an anionic mechanism. Since the polymer obtained in the 50-50 mixture of styrene and methyl methacrylate polymerized with metallic lithium had apparently an intermediate composition, it has been suggested that this is a block polymer obtained in a reaction discussed above. Further evidence favoring this mechanism is provided by the fact that under identical conditions only pure poly-methyl methacrylate is formed if the polymerization is initiated by butyl lithium and not by lithium dispersion. This proves that incorporation of styrene is due to a different initiation and not propagation. 

The electrode potential of lithium is -3.01 V vs. NHE, which is the lowest value among all the metals. Lithium has the lowest density (0.54gcnrf3) and the lowest electrochemical equivalent (0.259 g Ah-1) of all solids. As a result of these... 

As the cycling efficiency of metallic lithium is always significantly below 100% ( 99%), the lithium anode has to be overdimensioned (200-400%) in practical cells. 

LixC/Li, xCo02 cells (3.5V), they are attractive from a safety point of view because the titanium spinel operates at a potential significantly far away from that of metallic lithium. 

There are some other matters that should be considered when comparing metallic lithium alloys with the lithium-carbons. The specific volume of some of the metallic alloys can be considerably lower than that of the carbonaceous materials. As will be seen later, it is possible by selection among the metallic materials to find good kinetics and electrode potentials that are sufficiently far from that of pure lithium for there to be a much lower possibility of the potentially dangerous forma-... 

The composition, structure, and formation process of the SEI on metallic lithium depend on the nature of the electrolyte. The variety of possible electrolyte components makes this topic very complex it is reviewed by Peled, Golodnitsky, and Penciner in Chapter III, Sec.6 of this handbook. The types and properties of liquid nonaqueous electrolytes, that are commonly used in lithium cells are reviewed by Barthel and Gores in Chapter III, Sec.7. 

Beginning in the early 1980s [20, 21] metallic lithium was replaced by lithium insertion materials having a lower standard redox potential than the positive insertion electrode this resulted in a "Li-ion" or "rocking-chair" cell with both negative and positive electrodes capable of reversible lithium insertion (see recommended papers and review papers [7, 10, 22-28]). Various insertion materials have been proposed for the anode of rechargeable lithium batteries,... 

However, the reaction rate of LiA.Cn depends on the lithium concentration at the surface of the carbon particles, which is limited by the rather slow transport kinetics of lithium from the bulk to the surface LI7-19, 39]. As the melting point of metallic lithium is low (-180 °C) there is some risk of melting of lithium under abuse conditions such as short-circuiting, followed by a sudden breakdown of the SEI and a violent reaction of liquid lithium... 

The excess charge consumed in the first cycle is generally ascribed to SEI formation and corrosion-like reactions of Li C6[19, 66, 118-120]. Like metallic lithium and Li-rich Li alloys, lithiated graphites, and more generally lithiated carbons are thermodynamically unstable in all known electrolytes, and therefore the surfaces which are exposed to the electrolyte have to be kinetically protected by SEI films (see Chapter III, Sec.6). Neverthe-... 

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