LiVPO4F1–yOy tavorite-type compositions: influence of the vanadyl-type defects concentration on the structure and electrochemical performance

Edouard Boivin (1, 2, 3) , Rénald David (2, 3) , Jean-Noël Chotard (2, 3) , Tahya Bamine (1, 3) , Antonella Iadecola (3) , Lydie Bourgeois (4) , Emmanuelle Suard (5) , François Fauth (6) , Dany Carlier (1, 3) , Christian Masquelier (2, 3, 7) , Laurence Croguennec (1, 3, 7)

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

Mixed-valence LiVPO4F1–yOy materials were obtained for the first time over a large composition range (here 0.35 ≤ y ≤ 0.75) through a single-step solid-state synthesis. Interestingly, the competition between the ionic character of the V3+–F bond and the strong covalency of the V4+═O vanadyl bond originates complex crystal chemistry at the local scale, which allows stabilization of a solid solution between LiVPO4F and LiVPO4O despite a significant deviation from Vegard’s law for the cell parameters. A combined study using IR, Raman, and X-ray absorption spectroscopies highlights the effect of the vanadyl environment on the electronic structure of the vanadium orbitals and a fortiori the electrochemical behavior. Our results underline that the electrochemical performance of LiVPO4F1–yOy-type materials can be controlled by tuning the concentration of vanadyl-type defects, i.e., by playing on the competition between the ionic V3+–F bond and the covalent V4+═O bond.

Domaines: Matériaux

Edouard Boivin, Rénald David, Jean-Noël Chotard, Tahya Bamine, Antonella Iadecola, et al.. LiVPO4F1–yOy tavorite-type compositions: influence of the vanadyl-type defects concentration on the structure and electrochemical performance. Chemistry of Materials, 2018, 30 (16), pp.5682-5693. ⟨10.1021/acs.chemmater.8b02138⟩. ⟨hal-02115847⟩