DestiNa-ion_Operando: "Etude de la DynamiquE de Sodiation au sein de parTIcules individuelles
de matériaux actifs pour batteries Na-ion par mesures Operando TEM électrochimique "

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The main objective of the DESTINa-ion_Operando project is the development of instrumental methodologies based on in situ liquid / electrochemical TEM for the study of the dynamics of lithiation (and sodiation) in individual particles of positive electrode materials for Li-ion and Na-ion batteries. The inhomogeneity of the reactions of insertion of ions within crystals is strongly dependent on the solid-liquid (crystal / liquid electrolyte) and solid-solid (crystal / current collector) interfaces, and is the source of stresses, fractures mechanical and element migration (V, Mn, O) which degrade the reversibility of electrochemical reactions. These defects of uniformities present at the nanometric scale are at the origin of the difficulties of interpretation between the evolution of the electrochemical properties and the mechanisms of insertion of the ions. In addition, these structural accommodations essential to the ion insertion process are strongly dependent on the electrochemical reaction kinetics. Thus, the quantification of these structural inhomogeneities, their interfaces and their evolutions according to the state of charge and the electrochemical cycling regime is the key to provide a better understanding of the processes at the origin of the degradation of capacity retentions. Na-ion and Li-ion batteries.

 

In this project, we propose to develop 2 Operando experimental approaches based on the use of our electrochemical TEM sample holder [1] in order to follow, in real time (fast camera) and at the nanometric scale, the structural modulations induced by mechanisms of insertion into individual crystals. Developments will be carried out on the one hand, from electron diffraction in tomography mode [2] and dark field imaging, and on the other hand, from phase and crystal orientation mapping (ASTAR ). These studies in TEM Operando will be supplemented by "nanoprobe" measurements in X-ray synchrotron (ESRF) which allow measurements of X-ray diffraction and XANES absorption as well as X-fluorescence with a spatial resolution of 20 to 50 nm. depending on the technique. Our XRD electrochemical cell developed at LRCS for synchrotron lines will be used to carry out Operando electrochemical measurements. We will focus on 2 positive electrode materials, one for Li-ion batteries, the spinel oxide of LiNi1 / 2Mn3 / 2O4 said high potential which is a very interesting candidate for lithium-ion batteries of the type energy, and the other for power type Na-ion batteries, fluorinated vanadium phosphate Na3V2 (PO4) 2F3 (NVPF) of interest because it is chemically stable. DESTINa-ion_Operando aims to open a new path in the understanding of phenomena limiting the performance of electrochemical energy storage devices. This project is located in the scientific axis "transversal fields" (E.8), "sensor, instrumentation" (8.12).

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