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The electronic structure and ionic diffusion of nanoscale LiTiO2 anatase
W J H Borghols1, D Lützenkirchen-Hecht, U Haake
1Interfacultair Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands. w.j.h.borghols@tudelft.nl
Physical Chemistry Chemical Physics : PCCP
|October 22, 2009
Summary
Lithium insertion in nano-TiO2 reaches theoretical capacity, unlike bulk. Poor ionic conductivity in LiTiO2 limits high-rate performance in nano-materials.
Area of Science:
- Materials Science
- Electrochemistry
- Solid-State Chemistry
Background:
- The theoretical lithium storage capacity of TiO2 anatase is limited in bulk compositions.
- Understanding the electronic and ionic conductivity of lithiated TiO2 is crucial for battery applications.
Purpose of the Study:
- To investigate the electronic structure and ionic conductivity of LiTiO2.
- To explain the capacity limitations of TiO2 at different scales.
Main Methods:
- Ab initio calculations
- X-ray absorption spectroscopy (XAS)
- Nuclear magnetic resonance (NMR) relaxation experiments
Main Results:
- Nano-TiO2 (<10 nm) can reach the theoretical LiTiO2 phase, while bulk is limited to Li(x) approx 0.6TiO2.
- Li-2s electrons in LiTiO2 are primarily at Ti-3d(t2g)/4s hybridized sites, with ~10% in non-localized states, indicating good electronic conductivity.
- NMR experiments show low Li-ion hopping rates in LiTiO2, suggesting poor ionic conductivity.
Conclusions:
- Poor ionic conductivity of LiTiO2 at particle surfaces limits the achievable capacity in micro-anatase TiO2 at room temperature.
- The formation of poorly ionically conducting LiTiO2 hinders high-rate charge/discharge performance in nano-sized TiO2 materials.
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