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Based on the analysis, it was suggested that increased CBD causes a decrease in the electrochemical active surface area (NMC/pores). Additionally, the triple phase boundary density and the NMC/CBD interfacial area appear to have minor effects on the performance at high C-rates. Thus, to improve the power rate of the Li-ion battery high-energy electrodes, the engineering of the electrode design should aim for high values of interfacial area between NMC/pores. A simple increase of the CBD content is not an obvious solution to improve the overall performance; an ideal CBD morphology must be considered.

Concerning the pore network, the tortuosity anisotropy was observed for through-plane and in-plane directions. The tortuosity factor in the direction normal to the current collector was found to be significantly lower than the in- plane direction (about half). However, the cause of the anisotropy appears to be related to the calendaring process used to form high-energy density electrodes. Finally, greater heterogeneity in terms of phase-to-phase interconnectivity at the particle scale was also found for electrodes with higher CBD content, which may lead to a higher risk of performance deterioration during battery operation.

This work highlights how optimisation of the electrode design could improve the power rate of high-energy density electrodes. The results could lead to new strategies to improve the electrochemical performance of Li-ion batteries.

Fig. 68: a) Schematic representation of the hard X-ray nanoholotomography experimental setup at ID16B. b,c) Raw data filtered with Non-local Mean

and Unsharp Mask in 2D and 3D. d,e) Examples of the segmentation results in 2D and 3D using the machine

learning segmentation plugin, Trainable Weka, in ImageJ. f) Visualisation of the individual NMC particle

coloured in red in (e) along with the interfacial area with the other phases.

PRINCIPAL PUBLICATION AND AUTHORS

3D Quantification of Microstructural Properties of LiNi0.5Mn0.3Co0.2O2 High-Energy Density Electrodes by X-Ray Holographic Nano-Tomography, T.-T. Nguyen (a,b), J. Villanova (c), Z. Su (a), R. Tucoulou (c), B. Fleutot (a,d), B. Delobel (b), C. Delacourt (a,d), A. Demortière (a,d,e), Adv. Energy Mater. 11(8), 2003529 (2021); https:/doi.org/10.1002/aenm.202003529 (a) Laboratoire de Réactivité et Chimie des Solides (LRCS), CNRS UMR 7314, Hub de l Energie, Université de Picardie Jules Verne, Amiens (France) (b) Renault Technocentre, Guyancourt (France) (c) ESRF (d) Réseau sur le Stockage Electrochimique de l Energie (RS2E), CNRS FR 3459, Hub de l Energie, Amiens (France) (e) ALISTORE-European Research Institute, CNRS FR 3104, Hub de l Energie, Amiens (France)