Lithium insertion properties of Li TiNb2O7 investigated by neutron diffraction and first-principles modelling
| Autor: | Kevin S. Knight, Ilya Pinus, Michele Catti |
|---|---|
| Přispěvatelé: | Catti, M, Pinus, I, Knight, K |
| Rok vydání: | 2015 |
| Předmět: |
Materials Chemistry2506 Metals and Alloys
Materials science Lithium distribution Electronic Optical and Magnetic Material Coordination number Chemical lithiation Neutron diffraction Charge density Ceramics and Composite Condensed Matter Physic Crystal structure Anode material Conductivity Condensed Matter Physics Electrochemistry Electronic Optical and Magnetic Materials Inorganic Chemistry CHIM/02 - CHIMICA FISICA Crystallography Octahedron Materials Chemistry Ceramics and Composites Crystallographic-shear structure Physical and Theoretical Chemistry Monoclinic crystal system |
| Zdroj: | Journal of Solid State Chemistry. 229:19-25 |
| ISSN: | 0022-4596 |
| DOI: | 10.1016/j.jssc.2015.05.011 |
| Popis: | TiNb{sub 2}O{sub 7}, a good candidate as anode in lithium batteries, was treated with n-butyllithium to synthesize Li{sub x}TiNb{sub 2}O{sub 7} phases similar to those formed during electrochemical reactions. The Li{sub 2.67}TiNb{sub 2}O{sub 7} and Li{sub 3.33}TiNb{sub 2}O{sub 7} compounds, monoclinic C2/m, were studied by time-of-flight powder neutron diffraction. Their crystal structures, containing 3×3 blocks of (Ti,Nb)O{sub 6} octahedra, were Rietveld refined including Li positions. The Li atoms are distributed in similar amounts over sites with (Li–O) Coordination Numbers 5 and 4, although CN=5 should be preferred for having lower energy. Quantum-mechanical calculations were also performed, determining the average charge–discharge voltages to be 1.415 and 1.571 V for Li{sub 3.33}TiNb{sub 2}O{sub 7} and Li{sub 2.67}TiNb{sub 2}O{sub 7}, respectively, in good agreement with experimental results. An analysis of the theoretical charge distribution shows that, on lithiation, the chemical reduction of Ti and Nb atoms concentrates in the more condensed peripheral octahedra of the 3×3 block. This corresponds to electrons moving into a partly spin-polarized small band which gives rise to semi-metallic conductivity. - Graphical abstract: Structure of monoclinic Li{sub 3.33}TiNb{sub 2}O{sub 7}, and corresponding electron density of states. - Highlights: • Lithium was chemically inserted into the battery anode material TiNb{submore » 2}O{sub 7}. • Li atoms are distributed over four- and fivefold oxygen coordinated sites. • On lithiation Nb and Ti atoms are reduced according to a peculiar structural pattern. • Theoretically predicted charge–discharge voltages fit experiments very well.« less |
| Databáze: | OpenAIRE |
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