Computational Model for Predicting Particle Fracture During Electrode Calendering

In the context of calling for low carbon emissions, lithium-ion batteries (LIBs) have been widely concerned as a power source for electric vehicles, so the fundamental science behind their manufacturing has attracted much attention in recent years. Calendering is an important step of the LIB electrode manufacturing process, and the changes it brings to the electrode microstructure and mechanical properties are worth studying. In this work, we reported the observed cracking of active material (AM) particles due to calendering pressure under ex situ nano-X-ray tomography experiments. We developed a 3D-resolved discrete element method (DEM) model with bonded connections to physically mimic the calendering process using real AM particle shapes derived from the tomography experiments. The DEM model can well predict the change of the morphology of the dry electrode under pressure, and the changes of the applied pressure and porosity are consistent with the experimental values. At the same time, the model is able to simulate the secondary AM particles cracking by the fracture of the bond under force. Our model is the first of its kind being able to predict the fracture of the secondary particles along the calendering process. This work provides a tool for guidance in the manufacturing of optimized LIB electrodes

Binder-free CNT cathodes for Li-O2_2 batteries with more than one life

Li-O$_2$ batteries (LOB) performance degradation ultimately occurs through the accumulation of discharge products and irreversible clogging of the porous electrode during the cycling. Electrode binder degradation in the presence of reduced oxygen species can result in additional coating of the conductive surface, exacerbating capacity fading. Herein, we establish a facile method to fabricate free-standing, binder-free electrodes for LOBs in which multi-wall carbon nanotubes (MWCNT) form cross-linked networks exhibiting high porosity, conductivity, and flexibility. These electrodes demonstrate high reproducibility upon cycling in LOBs. After cell death, efficient and inexpensive methods to wash away the accumulated discharge products are demonstrated, as reconditioning method. The second life usage of these electrodes is validated, without noticeable loss of performance. These findings aim to assist in the development of greener high energy density batteries while reducing manufacturing and recycling costs.Comment: 24 pages, 6 figures, 10 figures in S

Adorym: A multi-platform generic x-ray image reconstruction framework based on automatic differentiation

We describe and demonstrate an optimization-based x-ray image reconstruction framework called Adorym. Our framework provides a generic forward model, allowing one code framework to be used for a wide range of imaging methods ranging from near-field holography to and fly-scan ptychographic tomography. By using automatic differentiation for optimization, Adorym has the flexibility to refine experimental parameters including probe positions, multiple hologram alignment, and object tilts. It is written with strong support for parallel processing, allowing large datasets to be processed on high-performance computing systems. We demonstrate its use on several experimental datasets to show improved image quality through parameter refinement

Reversible magnesium and aluminium ions insertion in cation-deficient anatase TiO₂

International audienc

Homogeneous coating of photonic macroporous oxides with inorganic nanocrystals

A simple method to obtain homogeneous sub-monolayer coverage of metal oxide and chalcogenide nanocrystals onto porous oxide supports is described. Quantitative nanoparticle coverage was probed using photonic macroporous oxide supports. Composites of nanocrystals of TiO2, Fe3O 4 or CdS dispersed onto macroporous SiO2 or ZrO 2 all show a predictable linear shift in the photonic stop band position

Bénéfices et risques de la poursuite du natalizumab jusqu'à la fin du premier trimestre de grossesse en cas de sclérose en plaques active : étude prospective

Thèse présentée sous la forme d'une "Thèse Article"Objective: To compare two therapeutic strategies for women with highly active multiple sclerosis (HAMS) planning pregnancy. The first consisted in maintaining natalizumab until conception and the second until the end of first trimester. Methods: Standardized therapeutic strategy for women with HAMS planning pregnancy was initiated in 2014 in our department. Natalizumab was recommended until the end of first trimester (“secured first trimester”). When patients refused to continue natalizumab during pregnancy, they were advised to continue until conception (“secured conception”). This strategy wast proposed only in patients with anti-JC virus antibody index lower than 1.5. Predictors of disease activity during pregnancy were assessed through multivariable logistic regression models. Results: 46 pregnancies were prospectively followed (30 with “secured first trimester” and 16 with “secured conception”). Two spontaneous abortions occurred in the group “secured first trimester” and 3 in the group “secured conception”. One birth deficiency occurred in the group “secured conception”. Proportions of patients with relapse and disability progression during pregnancy were lower in the group “secured first trimester” (3.6% vs 38.5%, p<0.005 for relapse and 3.6% vs 30.8%, p<0.05 for disability). In multivariate analysis, time when natalizumab was stopped (conception vs end of first trimester) (p<0.05) and relapse rate before natalizumab (p<0.05) were associated with relapse and disability progression during pregnancy. Conclusion: Maintaining natalizumab until the end of first trimester dramatically reduces the risk of disease reactivation during pregnancy in HAMS. This strategy must be carefully discussed with patients due to lack of comprehensive data on fetal safety.Objectif : comparer deux stratégies thérapeutiques pour les femmes atteintes de Sclérose en plaques (SEP) hautement active présentant un désir de grossesse. La première stratégie consistait à maintenir le natalizumab jusqu'à la conception et la seconde jusqu'à la fin du premier trimestre.Matériel et méthode : une stratégie thérapeutique standardisée pour les femmes atteintes de forme hautement active de SEP prévoyant une grossesse a été initiée en 2014 dans notre unité de neurologie. Le maintien du natalizumab leur a été recommandé jusqu'à la fin du premier trimestre (« premier trimestre sécurisé »). Lorsque les patientes ont refusé de continuer à prendre le natalizumab pendant la grossesse, il leur a été conseillé de continuer jusqu'à la conception (« conception sécurisée »). Cette stratégie n'a été proposée que chez les patients présentant un indice d'anticorps anti-virus JC inférieur à 1,5. Les facteurs prédicteurs de l'activité de la maladie pendant la grossesse ont été évalués à l'aide de modèles multivariés de régression logistique.Résultats : 46 grossesses ont été suivies de manière prospective (30 dans le groupe « premier trimestre sécurisé » et 16 dans « conception sécurisée »). Deux avortements spontanés sont survenus dans le groupe « premier trimestre sécurisé » et 3 dans le groupe « conception sécurisée ». Une malformation congénitale est survenue dans le groupe « conception sécurisée ». Les proportions de patientes présentant des poussées et une progression du handicap au cours de la grossesse étaient plus faibles dans le groupe « premier trimestre sécurisé » (3,6% contre 38,5%, p <0,005 pour une poussée et 3,6% contre 30,8%, p <0,05 pour l’aggravation du handicap). En analyse multivariée, la période d’arrêt du natalizumab (conception par rapport au premier trimestre) (p <0,05) et le taux de poussées avant le natalizumab (p <0,05) étaient associés aux risques de poussées et de progression du handicap pendant la grossesse.Conclusion : le maintien du natalizumab jusqu'à la fin du premier trimestre semble réduire considérablement le risque de réactivation de la maladie pendant la grossesse de patientes présentant une SEP très active. Cette stratégie doit être soigneusement discutée avec les patientes en raison du manque de données exhaustives sur la sécurité fœtale

Synthèse, caractérisations structurales et auto-organisations de nanocristaux (alliages COxPt100-x et nanocubes de Pt)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Thick Binder-Free Electrodes for Li-Ion Battery Fabricated Using Templating Approach and Spark Plasma Sintering Reveals High Areal Capacity

International audienceThe templating approach is a powerful method for preparing porous electrodes with interconnected well-controlled pore sizes and morphologies. The optimization of the pore architecture design facilitates electrolyte penetration and provides a rapid diffusion path for lithium ions, which becomes even more crucial for thick porous electrodes. Here, NaCl microsize particles are used as a templating agent for the fabrication of 1 mm thick porous LiFePO4 and Li4Ti5O12 composite electrodes using spark plasma sintering technique. These sintered binder-free electrodes are self-supported and present a large porosity (40%) with relatively uniform pores. The electrochemical performances of half and full batteries reveal a remarkable specific areal capacity (20 mA h cm(-2)), which is 4 times higher than those of 100 mu m thick electrodes present in conventional tape-casted Li-ion batteries (5 mA h cm(-2)). The 3D morphological study is carried out using full field transmission X-ray microscopy in microcomputed tomography mode to obtain tortuosity values and pore size distributions leading to a strong correlation with their electrochemical properties. These results also demonstrate that the coupling between the salt templating method and the spark plasma sintering technique turns out to be a promising way to fabricate thick electrodes with high energy density

Maintenance of natalizumab during the first trimester of pregnancy in active multiple sclerosis

International audienceBackground: Planning pregnancy in patients with active multiple sclerosis (MS) is highly challenging because treatment withdrawn may be associated with dramatic disease reactivation. Objective: To compare two strategies for women with active MS who were planning pregnancy: stopping natalizumab (1) at the end of the first trimester and (2) at conception. Methods: Standardized strategy for women with active MS was initiated in our department. Maintenance of natalizumab until the end of first trimester was recommended (“secured first trimester” (SFT)). When patients refused, they were advised to continue until conception (“secured conception” (SC)). Predictors of disease activity during pregnancy were assessed. Results: Forty-six pregnancies were prospectively followed (30 with SFT and 16 with SC). One congenital anomaly occurred in the SC group. The proportions of patients with relapse and disability progression during pregnancy were lower in the SFT than in the SC group (3.6% vs 38.5%, p < 0.005 and 3.6% vs 30.8%, p < 0.05, respectively). Predictors of relapse and disability progression during pregnancy were the time when natalizumab was stopped (conception vs end of first trimester) and the number of relapses during the year before natalizumab. Conclusion: Maintaining natalizumab during the first trimester may reduce the risk of disease reactivation during pregnancy in patients with active MS

Real-Time TEM Imaging of Moisture-Induced Degradation of Triple Cation Mixed Halide Perovskite

International audienc