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Two phase morphology limits lithium diffusion in TiO(2)(anatase): a (7)Li MAS NMR study
M Wagemaker1, R van de Krol, A P Kentgens
1Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands.
Journal of the American Chemical Society
|November 15, 2001
Summary
Lithium ion mobility in titanium dioxide was studied using 7Li solid-state NMR. Researchers found that phase boundaries significantly impact overall lithium diffusion rates, suggesting electronic effects may facilitate mobility.
Area of Science:
- Solid-state inorganic chemistry
- Materials science
- Electrochemistry
Background:
- Titanium dioxide (TiO2) is a promising material for energy storage applications.
- Understanding lithium ion diffusion is crucial for optimizing battery performance.
- Phase separation during lithium insertion can affect material properties.
Purpose of the Study:
- To investigate the local lithium environment and ion mobility in TiO2 and Li(0.6)TiO2.
- To elucidate the factors controlling lithium diffusion rates.
- To explore the relationship between electronic structure and ion mobility.
Main Methods:
- 7Li magic angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy.
- Analysis of phase separation and crystallographic structure changes.
- Temperature-dependent NMR measurements to determine activation energies.
Main Results:
- Phase separation occurs, forming Li-rich Li(0.6)TiO2 and Li-poor TiO2 phases.
- Lithium ions exhibit hopping with low activation energies in both phases (0.2 eV in anatase, 0.09 eV in titanate).
- Macroscopic diffusion is slower, with higher activation energy (~0.5 eV), attributed to phase boundary diffusion.
Conclusions:
- Phase boundary diffusion is the rate-limiting step for overall lithium intercalation.
- Electronic changes at higher temperatures correlate with increased lithium mobility.
- Solid-state NMR provides insights into ion dynamics and structure-property relationships in TiO2-based materials.
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