This thesis is about the study of the lamellar oxides NaxVO2. Several phases have been obtained with different stacking of the [VO2] sheets: O3-NaVO2, P’3-Na0.56VO2 and P2-Na0.73VO2. These three materials have been the subject of an electrochemical study in sodium batteries coupled with in situ X-ray diffraction in order to understand the structural transitions taking place as a function of the composition. A superstructure appears at Na1/2VO2 for the three stackings. This composition has been obtained by potentiostatic synthesis. The structural characterization shows that at this composition the three polytypes present a Na+/vacancy ordering and suggests the presence of clusters of vanadium ions. An unusual behaviour of the physical properties is observed as a result of this peculiar organization. This work demonstrates the important electronic correlations in this family of materials and paves the path to future studies in solid-state chemistry and physics.
Study of NaxVO2 layered oxides : electrochemistry, structure and physical properties