Research & Teaching Faculty

8 Li $\beta$-NMR study of epitaxial Li x CoO 2 films

Title8 Li $\beta$-NMR study of epitaxial Li x CoO 2 films
Publication TypeJournal Article
Year of Publication2014
AuthorsSugiyama, J, Harada, M, Oki, H, Shiraki, S, Hitosugi, T, Ofer, O, Salman, Z, Song, Q, Wang, D, Saadaoui, H, Morris, GD, Chow, KH, MacFarlane, WA, Kiefl, RF
JournalJ. Phys.: Conf. Ser.

In order to investigate the diffusive motion of Li + in a thin film electrode material for Li-ion batteries, we have measured β -NMR spectra of 8 Li + ions implanted into epitaxial films of Li 0.7 CoO 2 and LiCoO 2 in the temperature range between 10 and 310 K. Below 100 K, the spin-lattice relaxation rate (1/ T 1 ) in the Li 0.7 CoO 2 film increased with decreasing temperature, indicating the appearance and evolution of localized magnetic moments, as observed with μ + SR. As temperature is increased from 100 K, 1/ T 1 starts to increase above   200 K, where both Li- NMR and μ + SR also sensed an increase in 1/ T 1 due to Li-diffusion. Interestingly, such diffusive behavior was found to depend on the implantation energy, possibly because the surface of the film is decomposed due to chemical instability of the Li 0.7 CoO 2 phase in air. Such diffusive behavior was not observed for the LiCoO 2 film up to 310 K.