Experimental Visualization of Interstitialcy Diffusion of Li Ion in β‑Li2TiO3

• Published in: ACS applied energy materials Vol. 2; no. 8; pp. 5481 - 5489
• Main Authors: Mukai, Keisuke, Yashima, Masatomo, Hibino, Keisuke, Terai, Takayuki
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26.08.2019
• Subjects: nuclear fusion; diffusion mechanism; neutron diffraction; lithium-ion battery; DFT calculations
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.9b00639

Monoclinic lithium metatitanate, β-Li2TiO3, is a member of the Li2MO3 (M = Ti, Mn, Sn, Ru, and/or Ir) series and an important cation conductor for various energy applications such as Li-ion batteries and nuclear fusion reactors. Comprehensive knowledge of the crystal structure is vital to understand the Li-ion diffusion mechanism, and several possibilities were proposed previously. However, the exact crystal structure and Li-ion diffusion paths of β-Li2TiO3 are still unclear. Here, the results of a neutron diffraction study of high-purity 7Li-enriched β-Li2TiO3 are reported. The occupancy factor 0.033(3) and the atomic coordinates of the interstitial Li ion in the Li–O layer are successfully refined by Rietveld analysis of the time-of-flight neutron diffraction data. The three-dimensional network of Li-ion diffusion pathways is visualized by a combined technique of high-temperature neutron-diffraction and maximum-entropy methods. An interstitialcy diffusion mechanism, in which a lithium ion migrates through both the interstitial tetrahedral and lattice octahedral sites, is proposed for the Li2MO3 series.