Lithium chalcogenides

Me3Si)2M (M = Se, Te) can be readily made by silylation of the lithium chalcogenide. The telluride can be converted to the selenide using first Agl then Ag2Se, providing an extension to the Conversion Series established by Eaborn for silver salts (equation 68)21a,65,6 . 

Lavela P, Comad M, Mrotzek A, Harbrecht B, Tirado JL (1999) Electrochemical lithium and sodium intercalation into the tantalum-rich layered chalcogenides Ta2Se and Ta2Te3. J AUoy Compd 282 93-100... 

Lavela P, Morales J, Sanchez L, Tirado JL (1997) Novel layered chalcogenides as electrode materials for lithium-ion batteries. J Power Sources 68 704-707... 

Lithium insertion negative electrodes — (i) Some transition-metal oxides or chalcogenides insert Li ion reversibly at low redox potentials, for example, TiC>2, LL I iOy, M0S2, M0O2. (ii) Lithium alloys - in this case lithium ions, react with other elements polarized to low potentials to reversibly form Li alloys. The reaction usually proceeds reversibly according to the... 

Research has also focused on the study of highly reversible negative lithium insertion materials. Transition metal oxides and chalcogenides, such as M0O2, WO2, and TiS2, if combined with a metal oxide positive electrode material yield cells with low OCV values (ca. 1.5-2 V) [111]. 

Selenides.—The chemistry, and particularly the preparative aspects, of the chalcogenides has been reviewed.321 The heat of the reaction between F2 and Li2Se has been used322 to determine the heat of formation of lithium selenide. Some difficulty was experienced in this study in the preparation of the pure selenide, the method used being the direct reaction of liquid lithium with selenium vapour. It was concluded that the product contained some hydrated lithium hydroxide which had been formed whilst handling the selenide in a dry-box with a water and oxygen content of less than 5 p.p.m. by volume. 

Solid solutions Nb, V Se2 (0 < x < 1) have been prepared by direct synthesis. Single crystals of VSe2 were produced by chemical transport with iodine as transporting agent. ° Lithium has been intercalated into vanadium chalcogenides using n-butyl-lithium in hexane (see also p. 4). ... 

The use of organometallic reagents is well represented by the butyllithium technique. A solution of n-butyllithium in hexane is a mild and efficient reagent to form the lithium derivatives of transition-metal chalcogenides". The host structure is simply brought into contact with a diluted solution of n-BuLi in hexane (0.2-1.5 mol L ) under an inert atmosphere for several days at RT, Octane is formed as a byproduct of the reaction ... 

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