Lithium ions in the van der Waals gap of Bi2Se3 single crystals

Insertion/extraction of lithium ions into/from Bi2Se3 crystals was investigated by means of cyclic voltammetry. The process of insertion is reflected in the appearance of two bands on voltammograms at similar to 1.7 and similar to 1.5 V. corresponding to the insertion of Li+ ions into octahedral and tetrahedral sites of the van der Waals gap of these layered crystals. The process of extraction of Li+ ions from the gap results in the appearance of four bands on the voltammograms. The bands 1 and 2 at similar to 2.1 and similar to 2.3 V correspond to the extraction of a part of Li+ guest ions from the octahedral and tetrahedrals sites and this extraction has a character of a reversible intercalation/deintercalation process. A part of Li+ ions is bound firmly in the crystal due to the formation of negatively charged clusters of the (LiBiSe2 center dot Bi3Se4-) type. A further extraction of Li+ ions from the van der Waals gap is associated with the presence of bands 3 and 4 placed at similar to 2.5 and similar to 2.7 V on the voltammograms as their extraction needs higher voltage due to the influence of negative charges localized on these clusters. (C) 2010 Elsevier Inc. All rights reserved.