Self-diffusion in polycrystalline Li₁₊ Ti_2- Al (PO₄)₃ (0.2 ≤ x ≤ 0.4) samples followed by ⁷Li PFG (pulse field...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Electrochemistry

Background:

• Lithium titanium aluminum phosphate (LTAP) NASICON compounds are promising solid electrolytes for lithium-ion batteries.
• Understanding lithium ion mobility is crucial for optimizing their electrochemical performance.
• Previous studies utilized ND diffraction and MAS-NMR to probe structural features.

Purpose of the Study:

• To investigate short and long-range lithium ion motion in LTAP NASICON compounds.
• To correlate lithium content and preparation method (ceramic vs. sol-gel) with diffusion behavior.
• To determine crystallite size, activation energy, and charge carrier concentrations.

Main Methods:

• Pulsed Field Gradient Nuclear Magnetic Resonance (PFG-NMR) spectroscopy to measure diffusion coefficients.
• Analysis of NMR spin-echo signal minima to estimate crystallite size.
• Temperature-dependent conductivity measurements.

Main Results:

• Diffusion coefficients increase with lithium content and temperature.
• Sol-gel derived samples exhibit faster decay of diffusion coefficients with time due to lithium confinement in sub-micrometric crystallites.
• Crystallite size, activation energy, and charge carrier concentrations were successfully determined.

Conclusions:

• Lithium ion diffusion in LTAP NASICON is influenced by lithium content, temperature, and preparation method.
• PFG-NMR is effective in characterizing diffusion dynamics and estimating crystallite size in these materials.
• The findings provide insights into optimizing LTAP NASICON for solid-state battery applications.