Direct Evidence of Lithium-Induced Atomic Ordering in Amorphous TiO₂ Nanotubes

Journal Article · Mon Jan 27 00:00:00 EST 2014 · Chemistry of Materials

DOI:https://doi.org/10.1021/cm403951b· OSTI ID:1158463

Gao, Qi ^[1]; Gu, Meng ^[2]; Nie, Anmin ^[3]; Mashayek, Farzad ^[4]; Wang, Chong M. ^[2]; Odegard, Gregory M. ^[1]; Shahbazian-Yassar, Reza ^[3]

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1. Michigan Technological Univ., Houghton, MI (United States)
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
3. Michigan Technological Univ., Houghton, MI (United States); Univ. of Illinois, Chicago, IL (United States)
4. Univ. of Illinois, Chicago, IL (United States)

In this paper, we report the first direct chemical and imaging evidence of lithium-induced atomic ordering in amorphous TiO₂ nanomaterials and propose new reaction mechanisms that contradict the many works in the published literature on the lithiation behavior of these materials. The lithiation process was conducted in situ inside an atomic resolution transmission electron microscope. Our results indicate that the lithiation started with the valence reduction of Ti⁴⁺ to Ti³⁺ leading to a Li_xTiO₂ intercalation compound. The continued intercalation of Li ions in TiO₂ nanotubes triggered an amorphous to crystalline phase transformation. The crystals were formed as nano-islands and identified to be Li₂Ti₂O₄ with cubic structure (a = 8.375 Å). The tendency for the formation of these crystals was verified with density functional theory (DFT) simulations. The size of the crystalline islands provides a characteristic length scale (~5 nm) at which the atomic bonding configuration has been changed within a short time period. This phase transformation is associated with local inhomogeneities in Li distribution. On the basis of these observations, a new reaction mechanism is proposed to explain the first cycle lithiation behavior in amorphous TiO₂ nanotubes.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1158463
• Report Number(s): PNNL-SA-102277; 48146
• Journal Information: Chemistry of Materials, Vol. 26, Issue 4; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
Environmental Molecular Sciences Laboratory