Temperature dependence of structural and transport properties for Na3V2(PO4)2F3 and Na3V2(PO4)2F2.5O0.5

Thibault Broux (1, 2, 3) , Benoit Fleutot (3, 2) , Rénald David (2, 3) , Annelise Brüll (3, 1) , Philippe Veber (1) , François Fauth (4) , Matthieu Courty (2, 3, 5) , Laurence Croguennec (5, 3, 1) , Christian Masquelier (5, 3, 2)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 LRCS - Laboratoire réactivité et chimie des solides - UMR CNRS 7314
3 RS2E - Réseau sur le stockage électrochimique de l'énergie
4 ESRF - European Synchrotron Radiation Facility
5 ALISTORE-ERI - Advanced Lithium Energy Storage Systems - ALISTORE-ERI

Among polyanionic-based electrode materials developed for Na-ion batteries, one of the most promising families turns out to be Na3V2(PO4)2F3–yOy (0 ≤ y ≤ 2). Here, we present the influence of the oxygen substitution for fluorine on the structural and transport properties of Na3V2(PO4)2F3–yOy, as a function of temperature, through the comparison of the two compositions y = 0 and y = 0.5. An order–disorder phase transition is observed, whatever the content in oxygen, in relation with changes in the ionic conductivity and thus with the mobility of the Na+ ions within the tunnels of the tridimensional structure. The richer the content in oxygen in Na3V2(PO4)2F3–yOy, the higher is the electronic conductivity, in relation with the mixed valence state V3+/V4+ within the bioctahedral units V2O8F3–yOy, and the better are the electrochemical performances in Na-ion batteries.

Domaines: Matériaux

Thibault Broux, Benoit Fleutot, Rénald David, Annelise Brüll, Philippe Veber, et al.. Temperature dependence of structural and transport properties for Na3V2(PO4)2F3 and Na3V2(PO4)2F2.5O0.5. Chemistry of Materials, 2018, 30 (2), pp.358-365. ⟨10.1021/acs.chemmater.7b03529⟩. ⟨hal-01693955⟩