Lithium silicide

It is known about the existence of lithium silicide, Li6Si2, which is close to intermetallic compounds, and also that silicon is capable to form with lithium different alloys. We have calculated the theoretical specific capacity of such possible compounds, as well as pure silicon (Table 2). It is possible to explain from the Table 2 the noticeable increase of capacity for graphite electrodes (11%) even at the small content of Si (3wt%). We can suppose that some of such compounds (LixSiy) with high capacity may form... 

Lithium Silicide. Ii6Si2 mw 97.81 hygr, solid black crysts mp (vac) 600° (decompn) d about 1.12g/cc. 

Lithium silicide, LigSi2.—By heating excess of lithium with silicon, and expelling the uncombined metal at 400° to 500° C., the silicide is obtained as a very hygroscopic, dark-violet, crystalline substance 8 of density 1 12. It is a very reactive product and a powerful reducer. With concentrated hydrochloric acid it yields spontaneously inflammable silicoethane, Si2H3, of which it may be considered a derivative. 

TELLURIUM (13494-80-9) Finely divided powder or dust may be flammable and explosive. Violent reaction with strong oxidizers, bromine pentafluoride, halogens, interhalogens, iodine pentafluoride, hexalithium disilicide, lithium silicide, nitrosyl fluoride, oxygen difluoride, sodium peroxide, sulfur, zinc. Incompatible with cadmium, cesium, hafnium, strong bases, chemically active metals, iodic acid, iodine oxide, lead chlorite, lead oxide, mercury oxides, nitric acid, peroxyformic acid, platinum, silver bromate/iodate/ fluoride, nitryl fluoride, sodium nitrate. 

The phenomenon was attributed to a reaction between the metastable Lii5Si4 phase with the electrolyte through a self-charge mechanism. The reactivity of the amorphous lithium silicides and the self-discharge mechanism may lead to capacity loss or safety concerns. However, the authors noted that the use of carboxymethylcellulose (CMC) as a binder inhibited the discharge process significantly, implicating the reduction of side reactions with the electrolyte and, hence, capacity losses. 

There have been a large number of studies on the electrochemical reaction of Li with Si and subsequent cycling behavior. While at high temperatures (415"C) the equilibrium crystalline Li-Si phases are formed during lithiation of ciystalline Si, at room temperature a solid-state amorphization occurs to form amorphous lithium silicide (a-Li [Pg.2]

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