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摘要
Lithium titanium oxide Li[Li1/3Ti5/3]O-4 (LTO) is regarded as an ideal electrode material for lithium-ion batteries because of its "zero-strain" characteristic, high thermal stability, and structural stability. Here, the zero-strain means that the change in cubic lattice parameter is negligibly small during charge and discharge reactions. We performed ex situ Raman spectroscopy on Li1+x[Li1/3Ti5/3]O-4 samples with 0 <= x <= 0.94 to gain information about the relationship between a zero-strain reaction scheme and structural change at the atomic scale. The x = 0 (initial) sample exhibits three major Raman bands at 671, 426, and 231 cm(-1) and six minor Raman bands at 751, 510, 400, 344, 264, and 146 cm(-1). According to Raman spectroscopy results on other lithium titanium oxides such as Li2TiO3 and TiO2, the Raman bands at 510, 400, and 146 cm(-1) are attributed to TiO2 anatase, which is used as a starting material. As x increases from 0 to 0.94, the two major Raman bands at 426 and 231 cm(-1) show a blue shift, while the major Raman band at 671 cm(-1) maintains frequency. The three major Raman bands at 671, 423, and 231 cm(-1) are assigned to the A(1g) mode of symmetric stretching vibration v(sym)(Ti-O), the E-g mode of asymmetric stretching vibration v(asym)(Li-O), and the F-2g mode of bending vibration delta(Ti-O), respectively. Thus, the change in the Raman spectrum with x indicates that the bond length between the Ti and O atoms in the TiO6 octahedron is independent of x, while that between the Li and O atoms in the LiO6 octahedron and the bond angle between the Ti and O atoms in the TiO6 octahedron change with x. Raman studies with decreasing x from 0.94 to 0.10 clarified that such local structural changes are reversible, as in the case for the electrochemical reaction. The zero-strain insertion scheme is discussed from the perspective of Raman spectroscopy.
- 出版日期2014-2-13
