Multiple Li Positions inside Oxygen Octahedra in Lithiated TiO<sub>2</sub> Anatase

Wagemaker, Marnix; Kearley, Gordon J.; Well, A.A. van; Mutka, H.; Mulder, Fokko M.

doi:10.1021/ja028165q

Cited by 294 publications

(331 citation statements)

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“…77 This dual-basin feature is not reproduced by our calculations, and only a single potential energy minimum exists at the center of the interstitial sites, in agreement with previous ab initio studies of this system. 55 Geometry optimization of different relative Li + -Ti 3+ positions shows that the two possible configurations, where the Ti 3+ is coordinated to two of the oxygen atoms that make up the interstitial cage, are close in energy ͑⌬E = 4 meV͒.…”

Section: Summary and Discussionsupporting

confidence: 86%

“…In the GGA+ U case the polaronic localization of charge at a single Ti site ͑indicated as Ti III ͒ bonded to two of the equatorial oxygens produces a small distortion to the coordination geometry. The Ti III ion is larger than the remaining Ti IV ions, resulting in increased Ti III -O distances Wagemaker et al 77 have reported neutron scattering data that were interpreted as showing that Li intercalated into the anatase structure does not sit at the center of the octahedral interstices but is instead displaced along the c direction, occupying one of two equivalent sites separated by 1.61 Å. This preference for an off-center Li position was given support by data from molecular dynamics using the partial charge COMPASS force field.…”

Section: Geometrymentioning

confidence: 99%

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GGA+Udescription of lithium intercalation into anataseTiO2

2010

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We have used density-functional theory ͓generalized gradient approximation ͑GGA͔͒ to study lithium intercalation at low concentration into anatase TiO 2 . To describe the defect states produced by Li doping a Hubbard "+U" correction is applied to the Ti d states ͑GGA+ U͒. Uncorrected GGA calculations predict Li x TiO 2 to be metallic with the excess charge distributed over all Ti sites, whereas GGA+ U predicts a defect state 0.96 eV below the conduction band, in agreement with experimental photoelectron spectra. This occupied defect state corresponds to charge strongly localized at a single Ti 3d site neighboring the intercalated lithium with a magnetization of 1 B. This polaronic state produces a redshifted optical absorption spectrum, which is compared to those for the native O-vacancy and Ti-interstitial defects. The strong localization of charge at a single Ti center lowers the symmetry of the interstitial geometry relative to that predicted by GGA. The intercalated lithium sits close to the center of the octahedral site, occupying a single potential energy minimum with respect to displacement along the ͓001͔ direction. This challenges the previous interpretation of neutron diffraction data that there exist two potential energy minima separated by 1.6 Å along the ͓001͔ direction within each octahedron. Nudged elastic band calculations give barriers to interoctahedral diffusion of ϳ0.6 eV, in good agreement with experimental data. These barrier heights are found to depend only weakly on the position of the donated electron. The intercalation energy is 2.14 eV with GGA and 1.88 eV with GGA+ U, compared to the experimental value of ϳ1.9 eV. Li-electron binding energies have also been calculated. The ͓Li i• -Ti Ti Ј ͔ complex has a binding energy of 56 meV, and a second electron is predicted to be bound to give ͓Li i• -2Ti Ti Ј ͔ with a stabilization energy of 30 meV, indicating that intercalated lithium will weakly trap excess electrons produced during photoillumination or introduced by additional n-type doping.

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Section: Summary and Discussionsupporting

confidence: 86%

Section: Geometrymentioning

confidence: 99%

GGA+Udescription of lithium intercalation into anataseTiO2

2010

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“…These peaks are more or less visible in CV experiments 25,35 and may originate from multiple lithium sites in TiO 2 structure. 37 The mass of anatase TiO 2 NTs was unknown at the beginning and was determined at the end of electrochemical experiments by scraping nanotubes from Ti-foil. Therefore, galvanostatic cycling was performed by using current density of 100 μA · cm −2 and the current rate is calculated later.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Performance of Anatase TiO₂Nanotube Arrays Electrode in Ionic Liquid Based Electrolyte for Lithium Ion Batteries

Zec

Cvjetićanin

Bešter‐Rogač

et al. 2017

J. Electrochem. Soc.

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Ternary electrolyte composed of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid (PYR 14 TFSI), γ-butyrolactone (GBL) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and anatase TiO 2 nanotube arrays (NTAs) electrode are investigated for the application in new generation of lithium-ion batteries (LIBs). The electrical conductivity and viscosity are measured in the whole composition range at several temperatures. Also, cyclic voltammetry experiments are performed at different temperatures and scan rates. At all scan rates, up to 100 mV · s −1 Ti 4+ /Ti 3+ redox peaks appear designating exceptionally fast intercalation/deintercalation reaction. At the end of cycling the intercalation/deintercalation capacity was 144.8/140.7 mAh · g −1 at current rate 3 C. The diffusion coefficient for Li + extraction from TiO 2 nanotubes (NTs) have been calculated for temperatures from (25 to 55) • C. Activation energy for diffusion was found to be 54.7 kJ/mol (0.57 eV The rapid development of portable electronic devices and technologies significantly increased demand for the next generation of energy storage systems.1 Because of enhanced energy and power density, efficiency and long life, LIBs are currently one of the most promising energy storage devices.2,3 Improvement of safety standards and low impact on human health and environment is essential for large-scale application of LIBs. 4 Safety concerns related to utilization of highly volatile and flammable organic solvents in commercial cells can be addressed by introducing ionic liquids (ILs) as emerging class of fluids.5 Numerous advantages of ILs such as negligible vapor pressure and high chemical and thermal stability make them ideal candidates for their application in LIBs. Potential application of ILs based on a combination of the pyrrolidinium (PYR + ) cation and bis(trifluoromethanesulfonyl)imide (TFSI -) anion as electrolytes in LIBs with long term cycling stability and very good capacity utilization, has been confirmed by several research groups. [6][7][8][9][10][11][12] Nevertheless, the utilization of IL-based electrolytes is usually limited by their high viscosity, which reduces transport capabilities and slows down the chemical processes that occur in these solvents. Mixing of ionic liquids with molecular solvents such as organic carbonates or lactones can reduce viscosity of applied electrolyte. 12-15Among other aprotic solvents, γ-butyrolactone (GBL) is usually applied in new generation of LIBs and other electrochemical devices. Besides its low cost, GBL has wide liquidus range and better thermal stability comparing to alkyl carbonate solvents. 16 In our previous papers we demonstrated that binary mixture of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, (IM 14 TFSI), and GBL has around 20% higher specific conductivity at low IL mole fractions compared to IM 14 TFSI + propylene carbonate (PC) binary mixture.15,17 Xu et al. observed similar trend in the case of 1-ethyl-3-methylimidazolium dicyanamide (IM 12 DC...

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“…42 Its unit cell, Ti 4 O 8 , comprises four formula units. The structure can be described as composed of distorted TiO 6 octahedra with two different Ti-O distances, a long one (1.98 Å) involving the two apical oxygens and a short one (1.93 Å) involving the four equatorial oxygens.…”

Section: Methodsmentioning

confidence: 99%

Theoretical Study of the Effect of (001) TiO₂Anatase Support on V₂O₅

et al. 2010

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The effect of (001) TiO 2 anatase support on the electronic and catalytic properties of a V 2 O 5 monolayer is analyzed using density functional theory (DFT). The catalyst is represented by both clusters and periodic slabs. Using two experimentally relevant models of monolayer V 2 O 5 /TiO 2 (anatase) catalyst, both weak and strong interactions between a V 2 O 5 monolayer and the TiO 2 support have been investigated. In the first model, where a crystallographic (001) V 2 O 5 layer is placed on top of the (001) TiO 2 support, the weak interaction between vanadia and titania does not result in a major reconstruction of the active phase. Nevertheless, the changes in the electronic properties of the system are evident. The deposition of the vanadia monolayer on the titania substrate results in charge redistribution, enhancing the Lewis acidity of vanadium and the chemical hardness above the vanadyl oxygen, and in a shift of the Fermi level to lower binding energies accompanied by a reduction in the band gap. In the second model, where the (001) titania anatase structure is extended with a VO 2 film terminated by half a monolayer of vanadyl oxygen, apart from a similar electronic effect, the strong interaction of the vanadia phase with the titania support resulting from a high order of epitaxy has an important effect on the structure of the active phase. Atomic hydrogen adsorption is most favorable on the vanadyl oxygen of all the investigated surfaces, while the adsorption energy on this site increases by ∼10 kJ/mol due to the weak interaction between vanadia and titania and is further increased by ∼50 kJ/mol as a stronger interaction between the two phases is achieved, all in agreement with the increase in the negative electrostatic potential above the vanadyl site. The observed trends in the reactivity of the oxygen sites in H adsorption for the different catalyst models are successfully explained in terms of a frontier orbital analysis. IntroductionTransition metal oxides are widely used as catalysts for the oxidation of hydrocarbons. Especially vanadium oxide based catalysts are among the most active for the oxidation of both aliphatic and aromatic hydrocarbons. An important example of such a catalyst is V 2 O 5 /TiO 2 (anatase), which is used in industry as an effective catalyst for the production of phthalic anhydride from o-xylene.1,2 For the anatase support, although the (101) surface is thermodynamically more stable, the (100) and (001) faces are found in the industrial TiO 2 powders.3 Earlier experimental studies indicate that this catalytic system is of high performance when it consists of a monolayer of V 2 O 5 upon a TiO 2 (anatase) substrate, showing activity and selectivity not observed in the unsupported V 2 O 5 or TiO 2 anatase.2,4 The enhanced catalytic performance can be attributed to a synergetic effect between the active phase and the support. In order to unravel the role of the TiO 2 support on a V 2 O 5 monolayer catalyst, ab initio methods can help to provide a better understanding of the rel...

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Multiple Li Positions inside Oxygen Octahedra in Lithiated TiO₂ Anatase

Cited by 294 publications

References 21 publications

GGA+Udescription of lithium intercalation into anataseTiO2

GGA+Udescription of lithium intercalation into anataseTiO2

Electrochemical Performance of Anatase TiO₂Nanotube Arrays Electrode in Ionic Liquid Based Electrolyte for Lithium Ion Batteries

Theoretical Study of the Effect of (001) TiO₂Anatase Support on V₂O₅

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Multiple Li Positions inside Oxygen Octahedra in Lithiated TiO2 Anatase

Cited by 294 publications

References 21 publications

GGA+Udescription of lithium intercalation into anataseTiO2

GGA+Udescription of lithium intercalation into anataseTiO2

Electrochemical Performance of Anatase TiO2Nanotube Arrays Electrode in Ionic Liquid Based Electrolyte for Lithium Ion Batteries

Theoretical Study of the Effect of (001) TiO2Anatase Support on V2O5

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Multiple Li Positions inside Oxygen Octahedra in Lithiated TiO₂ Anatase

Electrochemical Performance of Anatase TiO₂Nanotube Arrays Electrode in Ionic Liquid Based Electrolyte for Lithium Ion Batteries

Theoretical Study of the Effect of (001) TiO₂Anatase Support on V₂O₅