Analysis of the ⁷Li NMR signals in the monoclinic Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃ phases

Aurore Castets (1) , Dany Carlier-Larregaray (1) , Khiem Trad (1) , Claude Delmas (1) , Michel Ménétrier (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The monoclinic Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃ 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 Li₃Fe₂(PO₄)₃ 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 Li₃V₂(PO₄)₃ studied by NMR by Cahill et al.

Domaines: Matériaux

Aurore Castets, Dany Carlier-Larregaray, Khiem Trad, Claude Delmas, Michel Ménétrier. Analysis of the ⁷Li NMR signals in the monoclinic Li₃Fe₂(PO₄)₃ and Li₃V₂(PO₄)₃ phases. Journal of Physical Chemistry C, 2010, 114 (44), pp.19141-19150. ⟨10.1021/jp106871z⟩. ⟨hal-00547203⟩