Recently, in LRCS, we have developed a new approach based on the use of X-ray nano computed tomography (nano-CT) [1,2] coupled with XANES spectroscopy for monitoring the dynamics of (de)lithiation inside NMC electrode [4]. The NMC cathode was cycled using a homemade electrochemical cell designed for tomography requirements. The variation in X-ray contrast around the Ni K-edge, which is related to the change of Ni oxidation state with Li occupation in NMC structure, allow us to estimate the (de)lithiation pathway within the electrode and secondary particles. In addition to the design of several models of electrochemical cells dedicated for nano-CT, we have developed a strong skill in image processing for the 3D tomography images associated with the 3D reconstruction, multiphase segmentation and XANES contrast. The coupling of the nano-CT technique with spatially resolved XRD turns out to be a perfect complement to the XANES contrast nano-CT due to the ability to follow the dynamic crystallographic structure of the host materials during the electrochemical reaction.

The goal of the PhD research project will focus on the 3D monitoring of (de)lithiation dynamics at the scale of both positive electrode and secondary particle. In the purpose, two approaches will be used, (1) combining X-ray computed tomography (XCT) and XANES spectroscopy to generate rich data sets allowing a direct correlation of chemical information and microstructure, (2) coupling X-ray computed tomography and XRD to follow the dynamic crystallographic structure of host materials and phase transformations. NMC will be the active cathode materials of this project.

Several synchrotrons, in which we have solid collaborations with XCT beamlines, will be used in the project: SOLEIL (nano-XCT/XANES) (Saclay, France), APS (nano-XCT/XANES, nano-XCT/XRD) (Chicago, USA), ESRF (micro-XCT/XRD) (Grenoble, France), SLS (micro-XCT/XANES) (PSI, France). The synchrotron SOLEIL will be the foreseen secondment of this PhD project. The PhD student will spend from 3 to 6 month to SOLEIL for XCT synchrotron experiments and to interact with beam scientist for data processing and optimization of experimental conditions.

[1] Zeliang Su, Vincent De Andrade, Sorina Cretu, Yinghui Yin, Michael J. Wojcik, Alejandro A. Franco, Arnaud Demortière, ACS Applied Energy Materials, 3,5, 4093-4102, 2020. [2] Tuan-Tu Nguyen, Julie Villanova, Zeliang Su, Rémi Tucoulou, Benoit Fleutot, Bruno Delobel, Charles Delacourt and Arnaud Demortière, Advanced Energy Materials, 11 (8), 2003529, 2021. [3] Zeliang Su, Tuan-Tu Nguyen, Christophe Le Bourlot, François Cadiou, Arash Jamali, Vincent De Andrade, Alejandro A. Franco, Arnaud Demortière (accpeted) Chemistry Methods 2021. [4] Tuan-Tu Nguyen, Zeliang Su, Vicent De Andrade, Bruno Delobel, Charles Delacourt, Arnaud Demortière, Operando XANES-Tomography nanoCT for studying NMC cathodeelectrode, ACS Energy letters, 2021 (in revewing)/

Supervisor(s) contact: Demortière, Arnaud, arnaud.demortiere@energie-rs2e.com