Analysis of the <sup>7</sup>Li NMR signals in the monoclinic Li<sub>3</sub>Fe<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> and Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> phases
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en
Article de revue
This item was published in
Journal of Physical Chemistry C. 2010, vol. 114, n° 44, p. 19141-19150
American Chemical Society
English Abstract
The monoclinic Li<sub>3</sub>Fe<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> and Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> phosphates are materials for positive electrodes in Li-ion batteries. They also have ...Read more >
The monoclinic Li<sub>3</sub>Fe<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> and Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> phosphates are materials for positive electrodes in Li-ion batteries. They also have interesting structures to test and improve the understanding of Li NMR signals in paramagnetic compounds. The position of such signals is governed by the transfer of electron spin density from the transition metal ion to the Li nucleus. These mechanisms are based on delocalization and polarization effects which induce positive and negative Fermi contact shifts, respectively. We have characterized Li<sub>3</sub>Fe<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> by Li NMR. To understand the signals observed, we have analyzed the electron spin density transfer mechanisms (i) by considering the different Li environments, (ii) by using DFT calculations. We compare our analysis to the one very recently reported by Davis et al. These analyses have been extended to Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> studied by NMR by Cahill et al.Read less <
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