Role of Oxide Ions in Thermally Activated Lithium Diffusion of Li[Li1/3Ti5/3]O4: X-ray Diffraction Measurements and Raman Spectroscopy

Although Li[Li1/3Ti5/3]O-4 (LTO) has been considered as an ideal electrode material for lithium-ion batteries (LIBs) because of its zero-strain Character, initial LTO exhibits high Li conductivity (sigma(Li)) at high temperatures (T). In this paper, to clarify the inter-relation between LTO's Li-diffusive nature and structural environment, we performed a systematic structural study on LTO using X-ray, diffraction (XRD) measurements and Raman spectroscopy. The average and static information obtained by XRD measurements suggested that the bottleneck radios for Li conduction is limited to similar to 0.41 even at 873 K, which is too small to explain the high sigma(Li), values in LTO. However, Raman spectrostopy demonstrated the dynamic structural changes of the LiO6 octahedron with T; the bond interaction between Li and 0 atoms decreases with T because of its anharmonic potential energy. Because the Raman-active modes in LTO correspond to changes in oxide ion position, oxide ions are determined to play a crucial role in obtaining high sigma(Li) values.