Spin-alignment echo NMR: probing Li+ hopping motion in the solid electrolyte Li7La3Zr2O12 with garnet-type tetragonal...

Area of Science:

• Solid-state chemistry
• Materials science
• Nuclear magnetic resonance spectroscopy

Background:

• Polycrystalline Li(7)La(3)Zr(2)O(12) is a promising solid electrolyte for lithium-ion batteries.
• Understanding lithium-ion dynamics is crucial for optimizing battery performance.
• Macroscopic measurements like impedance spectroscopy can be influenced by grain boundary effects.

Purpose of the Study:

• To measure single-spin hopping correlation functions in Li(7)La(3)Zr(2)O(12) using an atomic-scale NMR technique.
• To determine the activation energy for lithium-ion diffusion.
• To compare NMR findings with macroscopic transport measurements.

Main Methods:

• Utilized (7)Li spin-alignment echo (SAE) nuclear magnetic resonance (NMR) spectroscopy.
• Measured echo amplitude damping S(2)(t(m),t(p)) at variable mixing time t(m) and fixed preparation time t(p).
• Parametrized echo decay curves using stretched exponential functions to obtain decay rates.

Main Results:

• Echo amplitude damping is solely governed by slow lithium jump processes within the garnet structure.
• Decay rates exhibit Arrhenius behavior, yielding an activation energy of approximately 0.5 eV.
• The NMR-derived activation energy closely matches the value obtained from impedance spectroscopy.

Conclusions:

• Spin-alignment echo NMR effectively probes atomic-scale lithium dynamics.
• The consistent activation energy values suggest both NMR and impedance spectroscopy are sensitive to the same underlying lithium hopping correlation function.
• This study validates NMR as a powerful tool for investigating ion transport mechanisms in solid electrolytes.