Lithium Diffusion in Lithium-Transition-Metal Oxides Detected by 渭<sup>+sup>SR

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• 作者：Jun Sugiyama<sup>asup><sup> ; sup><sup>e0589@mosk.tytlabs.co.jpsup> ; Kazuhiko Mukai<sup>asup> ; Hiroshi Nozaki<sup>asup> ; Masashi Harada<sup>asup> ; Kazuya Kamazawa<sup>asup> ; YutakaIkedo<sup>gsup> ; Martin Må ; nsson<sup>csup> ; Oren Ofer<sup>bsup> ; Eduardo J. Ansaldo<sup>bsup> ; Jess H. Brewer<sup>dsup><sup> ; sup><sup>bsup> ; Kim H. Chow<sup>esup> ; IsaoWatanabe<sup>fsup> ; Yasuhiro Miyake<sup>gsup> ; Tsutomu Ohzuku<sup>hsup>
• 关键词：Self-diffusion and ionic conduction in nonmetals ; Lithium-ion batteries ; Muon-spin relaxation
• 刊名：Physics Procedia
• 出版年：2012
• 期刊代码：P128_18753892
• 类别：ph
• 出版时间：2012
• 卷：30
• 期：Complete
• 页码：105-108
• 文件大小：212 K

摘要

Diffusion of Li+ ionsin solidsisa basic principle behindthe operationof Li-ion batteries. Suchdiffusive behavior is represented by the diffusion equation (Fick's law), m>Jm> = 鈭?em>D 脳m> 未m>蠒/m>未m>xm>, where m>Jm> is the diffusion flux, m>Dm> is the self diffusion coeffcient, 蠒 is the concentration, and m>xm> is the position. Although m>Dm> of Li<sup>+sup> ions(m>Dm>Li)in solids is usually evaluatedby <sup>7sup>Li-NMR, diffculties arise for materials that contain magnetic ions. This is because the magnetic ions contribute additional spin-lattice relaxation processes thatis considerably larger than the1/m>Tm>1 expected from only Li diffusion. This implies that 7Li-NMRprovidesa rough estimateof m>Dm>Li for the positive electrode materials of Li-ion batteries, which include transition metal ions in order to compensate charge neutrality during a Li<sup>+sup> intercala-tion/deintercalation reaction. This is an unsatisfactory situation since m>Dm>Li is one of the primary parameters that govern the charge/discharge rate of a Li-ion battery.

We have, therefore, attempted to measure m>Dm><sub>Lisub> for lithium-transition-metal-oxides with muon-spin relaxation (渭<sup>+sup>SR) since 2005 . Muons do not feel fluctuating magnetic moments at high T, but instead sense the change in nuclear dipole field due to Li diffusion. Even if magnetic moments still affect the muon-spin depolarization rate, such aneffectis, in principle, distinguishablefromthatof nucleardipole fields.In particular,aweak longitudinal field can be applied that decouples the magnetic and nuclear dipole interactions . Here, we wish to summarize our 渭<sup>+sup>SR study on the lithium-transition-metal-oxides, LixCoO2, LiNiO2, and LiCrO2.