Ti-based materials exhibit suitable properties for usage in secondary Li- and Na-ion batteries and were in the focus of several electrochemical and ion conductivity studies. A material of such interest is layer-structured, monoclinic Na

Abstract:In many applications it has been found that the standard generalized gradient approximation (GGA) does not accurately describe weak chemical bond and electronic properties of solids containing transition metals. In this work, we have considered the intercalation material 1T-Li x TiS 2 (0 ≤ x ≤ 1) as a model system for the evaluation of the accuracy of GGA and corrected GGA with reference to the availabile experimental data. The influence of two different dispersion corrections (D3 and D-TS) and an on-site Coulomb repulsion term (GGA + U) on the calculated structural and electronic properties is tested. All calculations are based on the Perdew-Burke-Ernzerhof (PBE) functional. An effective U value of 3.5 eV is used for titanium. The deviation of the calculated lattice parameter c for TiS 2 from experiment is reduced from 14 % with standard PBE to −2 % with PBE + U and Grimme's D3 dispersion correction. 1T-TiS 2 has a metallic ground state at PBE level whereas PBE + U predicts an indirect gap of 0.19 eV in agreement with experiment. The 7 Li chemical shift and quadrupole coupling constants are in reasonable agreement with the experimental data only for PBE + U-D3. An activation energy of 0.4 eV is calculated with PBE + U-D3 for lithium migration via a tetrahedral interstitial site. This result is closer to experimental values than the migration barriers previously obtained at LDA level. The proposed method PBE + U-D3 gives a reasonable description of structural and electronic properties of 1T-Li x TiS 2 in the whole range 0 ≤ x ≤ 1.

No abstract