Crystal Structure of 3R‐LiTiS₂ and its Stability Compared to Other Polymorphs

Abstract

The crystal structure of 3R-LiTiS 2 was studied with combined experimental and theoretical approaches. The 3R polymorph of lithium titanium disulfide crystallizes rhombohedrally in the wellknown NaCrS 2 type with lattice parameters a = 352.98(1) pm, c = 1807.51(3) pm. The relative stability of 3R-LiTiS 2 with respect to

The High-Temperature Transformation from 1T- to 3R-Li x TiS2 (x = 0.7, 0.9) as Observed in situ with Neutron Powder Diffraction

“…Ab-initio calculations have shown before that, for = 1 at 0 K, the 1T phase is by ca. 4 kJ ⋅ mol −1 more stable than the 3R phase [9]. Obviously, this must be caused by covalency or other electronic effects.…”

“…We analyzed the contributions to the thermodynamic properties of the two polymorphs by periodic quantum-chemical calculations. Similar to our previ- ous theoretical work [9], we used density-functional theory (DFT). In addition to the full-DFT total energy, the electrostatic energy computed from the Kohn-Sham wavefunction, i.e., the sum of electron-nuclear attraction eN , electron-electron repulsion ee , and nuclear repulsion NN , was computed (see Table 3).…”

“…Although Colbow et al have described 3R-Li x TiS 2 for > 0.4 as early as in 1989 [5], it was not until 2013 that we have been able to report on the crystal structure of 3R-LiTiS 2 and compare its stabilities to those of other (partly hypothetical) polymorphs. However, as X-ray diffractometry was employed, experimental verification of the assumed lithium-ion positions is still lacking [9]. Very recently, a comprehensive study comprising a phase diagram ( vs. ) for the system 1T-/3R-Li x TiS 2 has been published [10].…”

Diffusion Pathways and Activation Energies in Crystalline Lithium-Ion Conductors

“…We succeeded in the reliable synthesis and structural characterization of fully lithiated (albeit not pure) 3R-LiTiS 2 (trigonal, R3̅ m), which computation showed to be metastable with respect to the 1T polytype by 4 kJ mol −1 at 0 K [57]. Pure phases with lower lithium content (x = 0.7, 0.9) were shown to reversibly transform between 1T and 3R in the range of 400-600 °C [58].…”

Density Functional Theory Evaluated for Structural and Electronic Properties of 1T-Li x TiS2 and Lithium Ion Migration in 1T-Li0.94TiS2

“…Since then the suitability of various phases of TiS 2 as cathode materials have been studied many times both experimentally and theoretically. The most frequently studied phase is 1T-TiS 2 [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] which crystallizes in the CdI 2 structure (space group P3 ̅ m1) and consists of titanium disulfide layers parallel to the ab plane. The layers have an AB stacking sequence and are connected mainly by van der Waals forces.…”