Abstract
Lithium diffusion in highly lithiated hexagonal titanium disulphide (h-Li xTiS 2, x = 0.88, 1.0) is investigated theoretically with periodic quantum-chemical methods. The calculated lithiation energies confirm that Li preferentially occupies the octahedral site rather than the tetrahedral site. Surprisingly, uncorrected density-functional theory (DFT) methods give better agreement with experiment for the structural parameters than the dispersion-corrected DFT-D approaches. Among the considered point defects, V Li, V Ti, and T ii, Li point defects are thermodynamically preferred in h-Li xTiS 2. A moderate relaxation is observed for the atoms surrounding the Li defect or Ti defect site, whereas a pronounced relaxation of the nearest neighboring atoms of a Ti Frenkel defect occurs. Competing pathways for Li diffusion in h-Li xTiS 2 are investigated using the climbing-image Nudged-Elastic-Band (cNEB) approach. Li + ions can migrate within the crystallographic ab plane either in a direct pathway through shared edges of neighboring octahedra or via vacant tetrahedral sites. The possibility of three-dimensional Li + diffusion along the c direction is investigated via inclusion of Ti point defects and Ti Frenkel defects.
Original language | English |
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Pages (from-to) | 449-459 |
Number of pages | 11 |
Journal | Zeitschrift fur Physikalische Chemie |
Volume | 226 |
Issue number | 5-6 |
DOIs | |
Publication status | Published - 1 Jun 2012 |
Funding
M. M. I. is grateful to Deutsche Forschungsgemeinschaft (DFG) for the post-doctorate funding of DFG-Forschergruppe 1277 molife “Mobilität von Li-Ionen in Festkörpern”.
Keywords
- Activation energy
- Dispersion corrected DFT
- Frenkel defect
- Li ion diffusion
- Lithium titanium disulphide
- Point defects
- Relaxation
ASJC Scopus subject areas
- Physical and Theoretical Chemistry