Oxidation under air of tavorite LiVPO4F : influence of vanadyl-type defects on its electrochemical properties

Edouard Boivin (1, 2, 3) , Jean-Noël Chotard (1, 2, 4) , Michel Ménétrier (2, 3) , Lydie Bourgeois (5) , Tahya Bamine (2, 3) , Dany Carlier (2, 3) , François Fauth (6) , Christian Masquelier (4, 1, 2) , Laurence Croguennec (2, 3, 4)

1 LRCS - Laboratoire réactivité et chimie des solides - UMR CNRS 7314
2 RS2E - Réseau sur le stockage électrochimique de l'énergie
3 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
4 ALISTORE-ERI - Advanced Lithium Energy Storage Systems - ALISTORE-ERI
5 ISM - Institut des Sciences Moléculaires
6 ALBA Synchrotron light source [Barcelone]

Tavorite-type compositions offer a very rich crystal chemistry, among which LiVIIIPO4F has the highest theoretical energy density (i.e., 655 Wh/kg). In this article, an in-depth study of vanadyl-type defects generated by temperature-controlled oxidation of LiVIIIPO4F under air is proposed, and the influence of the defects on the electrochemical properties is demonstrated. A combination of high resolution synchrotron diffraction, infrared spectroscopy, and magic angle spinning nuclear magnetic resonance was used to fully characterize the materials thus generated, from their average long-range structure to their local structure with the presence of defects. The increase of the annealing temperature tends to substitute oxygen for fluorine with the formation of a series of LiVPO4F1–xOx compositions. The miscibility domains appear to be narrow at the two ends of the solid solution (i.e., in the composition ranges LiVPO4F[1-0.9]O[0-0.1] and LiVPO4F[0-0.1]O[1-0.9]). The presence of vanadyl-type defects obtained as localized or more extended ones, depending on the annealing conditions, affects drastically the electrochemical properties of these Tavorite LiVPO4F-type materials.

Domaines: Matériaux

Edouard Boivin, Jean-Noël Chotard, Michel Ménétrier, Lydie Bourgeois, Tahya Bamine, et al.. Oxidation under air of tavorite LiVPO4F : influence of vanadyl-type defects on its electrochemical properties. Journal of Physical Chemistry C, 2016, 120 (46), pp.26187-26198. ⟨10.1021/acs.jpcc.6b07342⟩. ⟨hal-01581152⟩