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Morphological Dependence of Lithium Insertion in Nanocrystalline TiO2(B) Nanoparticles and Nanosheets
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1. Morphological Dependence of
Lithium Insertion in Nanocrystalline
TiO2(B) Nanoparticles and Nanosheets
Anthony G. Dylla, Penghao Xiao,
Graeme Henkelman and Keith J. Stevenson
Department of Chemistry & Biochemistry, University of Texas at Austin, Austin, TX
J. Phys. Chem. Lett. 2012, Vol. 3, 2015 - 2019 1
2. TiO2 as a Li+ battery anode
How Fast you can go
How Far you can go on one charge
Simon & Gogotsi Nat. Mater. 2008, 7, 845. Kim & Goodenough Chem. Mater. 2010, 22, 587.
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3. Titania polymorphism
& nanostructuring Titania
Anatase TiO2(B) Rutile
Nano Bulk
2-D architecture 3-D architecture
- Titania as a Li+ battery anode
- Safer lithiation potential (~1.6 V)
- Cycling durability
- Nanostructuring
- Improved specific capacity
- Improved lithiation kinetics
How does nanostructuring of TiO2(B) influence the lithiation mechanism?
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4. Synthesis of TiO2(B)
1000 °C HNO3
TiO2 (anatase) + KNO3 solid state
K2Ti3O7 H2Ti3O7 TiO2(B) bulk
H2O2, NH4OH, glycolic acid H2SO4
Ti powder Ti-glycolate complex H2Ti3O7 TiO2(B) NPs
- H2O
TiCl3 + H2O + HO(CH2)2OH TiO2(B) nanosheets
TiO2 – anatase TiO2 – rutile
TiO2(B)
(stable kinetic) (thermodynamic)
(kinetic)
Control of time/temperature in final dehydration step is key to limiting anatase contamination.
Kobayashi, M. Chem. Mater. 2007, 19, 5373.
Xiang, G. Chem. Comm. 2010, 46, 6801.
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5. Nanosheet morphology
• Nanosheet sizes range 100-300 nm.
• Ultrathin morphology shows buckling and stacking.
• Nano-crystalline domains observed.
• Spacing consistent with (020) index.
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6. TiO2(B) structure & lithiation sites
•Monoclinic C2/m structure
•Theoretical 1.25 Li+/Ti (418 mAh/g)
A1 site: in plane of equatorial O with 3-fold O coordination
A2 site: in plane of axial O with with 5-fold O coordination
C site: open channel parallel to b axis with 2-fold O coordination
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7. TiO2(B) nanosheets
Top-down view of (020) surface
z
y
x
Side view of nanosheet
y
x
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8. Lithium insertion by
galvanostatic charge/discharge
2.8
TiO2(B)-NS (a) TiO2(B)-NP
2.6 TiO2(B)-NP
2.4
Potential (V vs Li/Li )
+
2.2
2.0
dC/dV
1.8
1.6
TiO2(B)-NS
1.4
1.2
1.0
0 50 100 150 200 250 300
1.0 1.2 1.4 1.6 1.8 2.0 2.2
Specific Capacity (mAh/g) +
Potential (V vs Li/Li )
- Coin cell with Li anode and TiO2(B) + 5% carbon cathode.
- 25 mA/g charge rate.
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10. Comparison of DFT+U and
experiment
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11. Calculated effect of Coulomb
interaction on delithiation
Low Li%
- Ti
+ Li
High Li%
- -
+ +
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12. Conclusions and
acknowledgments
(1) Galvanostatic experiments combined with DFT+U calculations show two
distinct lithiation mechanisms based on dimensional confinement of TiO2(B).
(2) Though lithiation mechanisms are different for 2-D versus 3-D TiO2(B), their
slow charge/discharge capacities are similar.
This material is based upon work supported as part of the program
“Understanding Charge Separation and Transfer at Interfaces in Energy Materials
(EFRC:CST)”, an Energy Frontier Research Center funded by the U.S.
Department of Energy, Office of Science, Office of Basic Energy Sciences under
Award Number DE-SC0001091.
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