Jpcl jz300766a_Stevenson_Presentation

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Morphological Dependence of Lithium Insertion in Nanocrystalline TiO2(B) Nanoparticles and Nanosheets

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Jpcl jz300766a_Stevenson_Presentation

  1. 1. Morphological Dependence of Lithium Insertion in Nanocrystalline TiO2(B) Nanoparticles and Nanosheets Anthony G. Dylla, Penghao Xiao, Graeme Henkelman and Keith J. StevensonDepartment of Chemistry & Biochemistry, University of Texas at Austin, Austin, TX J. Phys. Chem. Lett. 2012, Vol. 3, 2015 - 2019 1
  2. 2. TiO2 as a Li+ battery anodeHow 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. Proprietary and Confidential 2 American Chemical Society
  3. 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? Proprietary and Confidential 3 American Chemical Society
  4. 4. Synthesis of TiO2(B) 1000 °C HNO3TiO2 (anatase) + KNO3 solid state K2Ti3O7 H2Ti3O7 TiO2(B) bulk H2O2, NH4OH, glycolic acid H2SO4Ti powder Ti-glycolate complex H2Ti3O7 TiO2(B) NPs - H2OTiCl3 + 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. Proprietary and Confidential 4 American Chemical Society
  5. 5. Nanosheet morphology • Nanosheet sizes range 100-300 nm. • Ultrathin morphology shows buckling and stacking. • Nano-crystalline domains observed. • Spacing consistent with (020) index. Proprietary and Confidential 5 American Chemical Society
  6. 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 Proprietary and Confidential 6 American Chemical Society
  7. 7. TiO2(B) nanosheets Top-down view of (020) surface z y x Side view of nanosheety x Proprietary and Confidential 7 American Chemical Society
  8. 8. Lithium insertion by galvanostatic charge/discharge 2.8 TiO2(B)-NS (a) TiO2(B)-NP 2.6 TiO2(B)-NP 2.4Potential (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. Proprietary and Confidential 8 American Chemical Society
  9. 9. DFT+U site occupancycalculations Proprietary and Confidential 9 American Chemical Society
  10. 10. Comparison of DFT+U andexperiment Proprietary and Confidential 10 American Chemical Society
  11. 11. Calculated effect of Coulombinteraction on delithiation Low Li% - Ti + Li High Li% - - + + Proprietary and Confidential 11 American Chemical Society
  12. 12. Conclusions andacknowledgments(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 underAward Number DE-SC0001091. Proprietary and Confidential 12 American Chemical Society

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