8Li β-NMR study of epitaxial LixCoO2 films

[摘要] 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 of8Li+ions implanted into epitaxial films of Li0.7CoO2 and LiCoO2 in the temperature range between 10 and 310 K. Below 100 K, the spin-lattice relaxation rate (1/T1) in the Li0.7CoO2 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/T1 starts to increase above ∼ 200 K, where both Li- NMR and μ+SR also sensed an increase in 1/T1 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 Li0.7CoO2 phase in air. Such diffusive behavior was not observed for the LiCoO2 film up to 310 K.

[发布机构] Toyota Central Research and Development Laboratories, Inc., 41-1 Yokomichi, Nagakute, Aichi; 480-1192, Japan^1;Higashifuji Technical Center, Toyota Motor Co., Susono, Shizuoka; 410-1193, Japan^2;Advanced Institute for Materials Research, Tohoku University, Sendai, Miyagi; 980-8577, Japan^3;TRIUMF, 4004 Wesbrook Mall, Vancouver; BC; V6T 2A3, Canada^4;Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, Villigen PSI; CH-5232, Switzerland^5;Department of Chemistry, University of British Columbia, Vancouver; BC; V6T 1Z1, Canada^6;Department of Physics and Astronomy, University of British Columbia, Vancouver; BC; V6T 1Z1, Canada^7;Department of Physics, University of Alberta, Edmonton; AB; T6G 2G7, Canada^8

[关键词] Chemical instability;Diffusive behavior;Diffusive motions;Implantation energies;Localized magnetic moments;Spin lattice relaxation rates;Temperature range;Thin-film electrode