Interstitial lithium diffusion pathways in γ-LiAlO2: a computational study.

Area of Science:

• Solid-state chemistry
• Materials science
• Computational materials science

Background:

• Lithium diffusion in single crystalline γ-LiAlO2 has been previously studied using Li-7 NMR spectroscopy and conductivity measurements.
• However, the precise diffusion pathways for lithium ions remain unclear.

Purpose of the Study:

• To theoretically elucidate the lithium diffusion pathways in γ-LiAlO2 using first-principles calculations.
• To investigate competing pathways for lithium ion migration within the γ-LiAlO2 lattice.

Main Methods:

• Employed the climbing-image nudged-elastic-band approach.
• Utilized periodic quantum-chemical density functional theory (DFT) for calculations.

Main Results:

• Identified two primary lithium diffusion mechanisms: via lithium point defects (vacancies, VLi) and via lithium Frenkel defects (VLi + Lii).
• Calculated activation energies indicate that lithium conductivity is highly sensitive to the lattice distribution of vacancies and interstitials.
• For Frenkel defects, calculated activation energies for jumps to nearest-neighbor vacant sites align with experimental data.

Conclusions:

• Lithium diffusion pathways in γ-LiAlO2 are significantly influenced by the interplay of vacancies and interstitials.
• The Frenkel defect mechanism provides a good theoretical basis for understanding experimental lithium ion conductivity in γ-LiAlO2.