Crystal structure and diffusion path in the fast lithium-ion conductor La(0.62)Li(0.16)TiO3

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Lithium-ion conductivity in perovskite materials is critical for energy storage applications.
• Understanding cation diffusion pathways is essential for optimizing ionic conductivity.
• La(0.62)Li(0.16)TiO3 is a promising perovskite material for potential electrochemical applications.

Purpose of the Study:

• To elucidate the diffusion path of lithium cations in La(0.62)Li(0.16)TiO3 perovskite at room temperature.
• To investigate the role of structural sites and vacancies in facilitating lithium ion transport.
• To re-evaluate the diffusion bottleneck and percolation model for Li-cation conductivity.

Main Methods:

• Neutron powder diffraction was employed to study the crystal structure of La(0.62)Li(0.16)TiO3 at different temperatures (77 K and room temperature).
• Analysis of cation positions and probability densities was performed to map the diffusion pathways.
• A two-dimensional bond-percolation model was utilized to discuss Li-cation conductivity.

Main Results:

• At 77 K, Li cations occupy the 2c site on the La-deficient (002) layer.
• At room temperature, Li cations exhibit broader distribution and migrate via 2c-4f-2c or 2c-2d-2c pathways on the (002) layer.
• Diffusion bottlenecks are located between 2c and 4f/2d sites, differing from previous assumptions of bottlenecks at specific sites.

Conclusions:

• The study clarifies the dynamic diffusion mechanism of lithium cations in the investigated perovskite.
• The presence of vacancies at the La site is identified as a critical factor for enabling Li-cation conduction.
• The findings provide a refined understanding for designing advanced perovskite-based ionic conductors.