LITHIUM INTERCALATION INTO PBNB2S5, PBNBS3, SNNB2SE5, BIVS3, SNVSE3, AND PBNB2SE5 MISFIT LAYER CHALCOGENIDES

The intercalation of lithium into various misfit layer chalcogenides of two different stoichiometries was performed by using n-butyl lithium on powders. The reaction was found to proceed topochemically, and a greater expansion in the c direction and higher lithium contents were observed in the lithiated phases with "MM′2X5" approximate stoichiometries compared to "MM′X3" stoichiometries. This behaviour difference is assigned to the different stacking sequence of the slices of the two sublattices formed by double layers of MX and sandwiches of M′X2. Lattice distortions are induced during lithiation, leading to changes in the relative orientation of MS-type bilayers and to complete amorphization after long reaction times. The synthesis and partial characterization of a new misfit layer selenide of nominal composition "PbNb2Se5" is also reported. The value of the c-dimension (c = 37.37 Å) suggests a stacking sequence PbSeNbSe2NbSe2PbSeNbSe2NbSe2, etc. This material becomes highly unstable on lithium intercalation and decomposes to its constituents after a few hours of lithiation. © 1992.