InSe, lithium intercalation

Julien C, Jouanne M, Burret PA, Balkanski M (1989) Effects of lithium intercalation on the optical properties of InSe. Mater Sci Eng B 3 39 14... 

The intercalation of lithium in InSe has been extensively studied. Indium monoselenide is a layered semiconductor in which each layer consists of four close-packed, covalently bounded, monoatomic sheets in the sequence Se-In-ln-Se. When material is grown by the Bridgman method, the 3R polytype (y-InSe) crystallizes in a rhombohedral system with the R3m space group (C 6v) with the primitive unit cell containing three layers but only one molecule [43, 44]. The layers are stacked in the sequence CBAuABC separated by weak interlayer interaction (often referred to as van der Waals-like). The square symbol represents the empty site available for insertion. The interaction of cleaved InSe crystals with lithium was investigated by electrochemical titration, in situ X-ray diffractometry, and by X-ray photoemission spectroscopy showing a competition between intercalation and chemical decomposition reactions expressed as [45 7] ... 

Fig. 4.17 Raman scattering spectra of pristine and Li intercalated y-InSe single crystal. The intercalated samples were prepared by galvanostatic method in lithium cell...

The striking example is the reactivity of lithium with IE-VI layered compounds such as the decomposition of Li intercalated InSe with the formation of lithium selenide, Li2Se, observed by Raman spectroscopy on specimens prepared by various intercalation methods. The insertion of Li into M0S2 appears more stable with the occurrence of a superlattice formation at x(Li) 0.25 but a structural transformation from 2H-M0S2 (P-phase) to IT-M0S2 (a-phase) occurs for x l. This process is irreversible but the intercalation-deintercalation reaction is possible with the IT-M0S2, which could act as a positive electrode in rechargeable lithium batteries after formation of the cells. 

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