High Substitution Rate in TiO ₂ Anatase Nanoparticles with Cationic Vacancies for Fast Lithium Storage

Journal Article · Wed Jun 24 00:00:00 EDT 2015 · Chemistry of Materials

DOI:https://doi.org/10.1021/acs.chemmater.5b01407· OSTI ID:1325245

Li, Wei; Corradini, Dario; Body, Monique; Legein, Christophe; Salanne, Mathieu; Ma, Jiwei; Chapman, Karena W.; Chupas, Peter J.; Rollet, Anne-Laure; Julien, Christian; Zhagib, Karim; Duttine, Mathieu; Demourgues, Alain; Groult, Henri; Dambournet, Damien

Doping is generally used to tune and enhance the properties of metal oxides. However, their chemical composition cannot be readily modified beyond low dopant amounts without disrupting the crystalline atomic structure. In the case of anatase TiO₂, we introduce a new solution-based chemical route allowing the composition to be significantly modified, substituting the divalent O^2- anions by monovalent F- and OH- anions resulting in the formation of cationic Ti⁴⁺ vacancies (square) whose concentration can be controlled by the reaction temperature. The resulting polyanionic anatase has the general composition Ti_1-x-y square _x+yO_2-4(x+y)F_4x(OH)_4y, reaching vacancy concentrations of up to 22%, i.e., Ti_0.78 square _0.22O_1.12F_0.4(OH)_0.48. Solid-state F-19 NMR spectroscopy reveals that fluoride ions can accommodate up to three different environments, depending on Ti and vacancies (i.e. Ti₃-F, Ti-_{2 square 1}-F, and Ti-_{1 square 2}-F), with a preferential location close to vacancies. DFT calculations further confirm the fluoride/vacancy ordering. When its characteristics were evaluated as an electrode for reversible Li-ion storage, the material shows a modified lithium reaction mechanism, which has been rationalized by the occurrence of cationic vacancies acting as additional lithium hosting sites within the anatase framework. Finally, the material shows a fast discharging/charging behavior, compared to TiO₂, highlighting the benefits of the structural modifications and paving the way for the design of advanced electrode materials, based on a defect mediated mechanism.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: European Commission - Community Research and Development Information Service (CORDIS) - Seventh Framework Programme (FP7); USDOE Office of Science - Office of Basic Energy Sciences - Scientific User Facilities Division
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1325245
• Journal Information: Chemistry of Materials, Vol. 27, Issue 14; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

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