期刊
SOLID STATE NUCLEAR MAGNETIC RESONANCE
卷 42, 期 -, 页码 26-32出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ssnmr.2012.01.002
关键词
Exchange spectroscopy; Ion dynamics; Lithium battery materials; Solid-state NMR
资金
- NSERC
The effectiveness of two different selective inversion methods is investigated to determine timescales of Li ion mobility in paramagnetic Li intercalation materials. The first method is 1D exchange spectroscopy, which employs a 90 degrees-tau(1)-90 degrees sequence for selective inversion of a Li resonance undergoing site exchange. The experiment is most easily applied when the first delay period, tau(1), is set to the frequency difference between two resonances undergoing ion exchange. This enables the determination of ion hopping timescales for single exchange pair systems only. To measure ion dynamics in systems having more than one exchange process, a second selective inversion method was tested on two paramagnetic Li intercalation materials. This second technique, replaces the 90 degrees-tau(1)-90 degrees portion of 1D EXSY with a long, selective shaped pulse (SP). Two paramagnetic solid-state materials, which are both cathode materials for lithion ion batteries, were chosen as model compounds to test the effectiveness of both the selective inversion methods. The first compound, Li2VPO4F, was chosen as it hosts two Li sites with 1-exchange process. The second model compound is a 3-site, 3-exchange process system, Li2VOPO4. For the 2-site material, Li2VPO4F, the timescales of the single A-B exchange process were found to be within error of one another regardless of the inversion method. For the 3 Li-site material Li2VOPO4, the three exchange processes, AB, BC, and AC, were found to be on the millisecond timescale as revealed using the SP method. These timescales were determined over a variable temperature range where activation energies extended from 0.6 +/- 0.1 eV up to 0.9 +/- 0.2 eV. (C) 2012 Elsevier Inc. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据