Document Type : Research
Author
Payamme nor university
Abstract
In this study, lithium‑ion migration and the role of point defects in monoclinic Li₂TiO₃ were investigated using density functional theory (DFT). The crystal structure of Li₂TiO₃ in the C2/m space group was optimized, and electronic structure calculations showed that the pristine compound exhibits semiconducting behavior with a direct band gap of about 2.90 eV. The valence band is dominated by O 2p orbitals, while the conduction band originates from Ti 3d states.
To investigate the influence of defects on lithium diffusion, several point defects, including a single lithium vacancy (VLi), a double lithium vacancy (V₂Li), and a lithium–oxygen vacancy complex (VLi+VO), were introduced. The calculated band structures and partial density of states (PDOS) reveal that these defects produce localized states near the Fermi level, enhancing electronic conductivity. Defect formation energies were also calculated to evaluate the stability of the defective configurations.
Lithium‑ion migration was studied using the nudged elastic band (NEB) method to identify diffusion pathways. Three migration paths were obtained with activation energy barriers of approximately 0.886, 1.09, and 1.20 eV. Transition state analysis indicates that migration barriers are mainly controlled by the local Li–O coordination environment, while Li–Ti interactions play a secondary role by influencing diffusion channel width. Charge density difference analysis shows that charge redistribution around oxygen atoms affects transition state stability.
Overall, the results show that lattice geometry and defect engineering control lithium‑ion migration in Li₂TiO₃ and guide the design of lithium‑based materials with improved ionic transport
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