Identify OH groups in TiOF{sub 2} and their impact on the lithium intercalation properties

Journal Article · Wed Feb 15 04:00:00 EST 2017 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2016.11.010· OSTI ID:22658173

Li, Wei ^[1]; Body, Monique; Legein, Christophe ^[2]; Dambournet, Damien ^[1]

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1. Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 8234 PHENIX, 75005 Paris (France)
2. Université Bretagne Loire, Université du Maine, UMR CNRS 6283, Institut des Molécules et des Matériaux du Mans (IMMM), Avenue Olivier Messiaen, 72085 Le Mans Cedex 9 (France)

A detailed investigation on the chemical composition of the cubic form of titanium oxyfluoride-based compound reveals the presence of OH groups substituting the oxide/ fluoride sublattice. The substitution of oxide by hydroxyl groups induces the presence of titanium vacancies (□) which were characterized by {sup 1}H and {sup 19}F solid-state NMR. {sup 1}H NMR shows that OH groups are present as bridging Ti-OH-Ti or terminal OH groups, i.e. sitting close to a titanium vacancy Ti-OH-□. The electrochemical properties vs. Li{sup +}/Li indicates that the presence of OH groups prevents the intercalation of lithium in the upper voltage region (1.2–3 V vs. Li{sup +}/Li). Indeed, a partial dehydroxylation of the framework enables to improve the reversibility of the lithium insertion/de-insertion processes. Since the presence of OH groups in this type of compounds is usual and depends on the synthesis method employed, this work enables to rationalize the different electrochemical behaviors reported in the literature and further highlights the importance of a good knowledge of the chemical composition with regard to the physico-chemical properties. - Graphical abstract: The substitution of oxide by hydroxyl groups inducing the formation of titanium vacancies (□), i.e., Ti{sub 1−x}□{sub x}O{sub 1-4x}(OH){sub 4x+y}F{sub 2−y}, was characterized by solid-state {sup 1}H and {sup 19}F NMR. - Highlights: • Evidences of the presence of OH groups and titanium vacancies in titanium oxyfluoride. • {sup 1}H NMR showed the presence of Ti-OH-Ti and Ti-OH-□ species. • The presence of OH groups limits the insertion of lithium within the interstitial sites.

• OSTI ID: 22658173
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 246; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CHEMICAL COMPOSITION
CLATHRATES
ELECTRIC POTENTIAL
EXPERIMENTAL DATA
FLUORINE COMPOUNDS
HYDROXYL RADICALS
LITHIUM IONS
NUCLEAR MAGNETIC RESONANCE
OXIDATION
OXIDES
TITANIUM COMPOUNDS
VACANCIES