This presentation has been moved. To view this presentation, please visit http://pubs.acs.org/iapps/liveslides/pages/index.htm?mscNo=jz300766a Morphological Dependence of Lithium Insertion in Nanocrystalline TiO2(B) Nanoparticles and Nanosheets

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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9. DFT+U site occupancy
calculations
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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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