The High-Temperature Transformation from 1T- to 3R-LixTiS2 (x = 0.7, 0.9) as Observed in situ with Neutron Powder Diffraction

Dennis Wiedemann 1 , Suliman Nakhal 1 , Anatoliy Senyshyn 2 , Thomas Bredow 3 ,  and Martin Lerch 1
  • 1 Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
  • 2 FRM II, Technische Universität München, Lichtenbergstraße 1, 85747 Garching b. München, Germany
  • 3 Mulliken Center for Theoretical Chemistry, Universität Bonn, Beringstraße 4, 53115 Bonn, Germany

Abstract

Layered titanium disulfide is used as lithium-ion intercalating electrode material in batteries. The room-temperature stable trigonal 1T 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 1T 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.

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Founded in 1887, the Zeitschrift für Physikalische Chemie covers the main developments in physical chemistry, placing with an emphasis on experimental research. It represents a combination ofdiscusses reaction kinetics and spectroscopy, surface research and electrochemistry, thermodynamics and the structure analysis of matter in its various conditions, among other topics.

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