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The high-temperature transformation from 1T-to 3R-LixTiS2 (x=0.7, 0.9) as observed in situ with neutron powder diffraction

By Dennis Wiedemann, Suliman Nakhal, Anatoliy Senyshyn, Thomas Bredow and Martin Lerch

Abstract

Layered titanium disulfide is used as lithium-ion intercalating electrode material in batteries. The room-temperature stable trigonal IT polymorphs of the intercalates LixTiS2(x <= 1) are widely-investigated. However, the rombohedral 3R polymorphs, being stable at higher temperatures for large x, are less well known. In this study, we report on the synthesis of phase-pure 1T-LixTiS2(x = 0.7, 0.9) and its transformation to the 3R phase between 673 and 873 K as monitored using high-temperature neutron powder diffractometry. For the 3R polymorph, full Rietveld refinements show lithium ions to be statistically distributed over octahedral voids at the fractional coordinates 0, 0, 1/2, exclusively. The comparison of Madelung energies with results of periodic quantum-chemical calculations reveals that the evolution of lattice parameters and the room-temperature stability of the IT phase are not governed by electrostatics, but by correlation and polarization. The insights gained do not only elucidate the structure of 3R-LixTiS2, but also help to understand and control polymorphism in layered transition-metal sulfides.DFG, FOR 1277, Mobilität von Lithiumionen in Festkörpern (molife

Topics: 540 Chemie und zugeordnete Wissenschaften, lithium-ion conductors, lithium transition-metal sulfides, layered structures, phase transformation, thermal expansion
Year: 2015
DOI identifier: 10.1515/zpch-2014-0659
OAI identifier: oai:depositonce.tu-berlin.de:11303/5890
Provided by: DepositOnce
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