Étude du polymère élastomère à base d’acrylonitrile, HNBR, pour son application dans les batteries Li-ion

Les travaux présentés portent sur l’étude du HNBR (Hydrogenated Nitrile Butadiene Rubber), un polymère à base d’acrylonitrile, pour son application en tant que liant d’électrodes dans les batteries lithium ions. Cette thèse repose sur un partenariat avec l’entreprise Hutchinson (spécialisée dans le domaine des polymères) qui a cherché à développer un nouveau procédé pour la fabrication des électrodes. Ce procédé par voie fondue a soulevé la problématique du polymère liant utilisé dans les électrodes puisque ce dernier doit être compatible avec le procédé tout en étant utilisable dans des batteries. C’est dans l’optique de trouver et valider un tel polymère que s’inscrit cette thèse sur le polymère HNBR. En premier lieu, nous nous sommes concentrés sur les répercussions du traitement thermique, étape importante du procédé par voie fondue, sur le HNBR. Il a été conclu que le traitement thermique conduit à une réticulation du polymère aidant ainsi à la stabilité chimique du HNBR dans les électrolytes organiques des batteries. Ensuite, le HNBR a été introduit comme liant d’électrodes et a été analysé, avec le procédé de fabrication classique puis avec le nouveau procédé. Nous avons remarqué que le HNBR est un bon candidat pour être utilisé dans un système électrochimique car il y est stable sur une large gamme de potentiels et permet d’obtenir des performances en cyclage et en puissance intéressantes. Face à ce constat, la dernière partie des travaux s’est concentrée sur une analyse approfondie du système en étudiant les interactions entre les fonctions polaires du HNBR, les nitriles, et les ions lithium présents dans l’électrolyte. La combinaison polymère-sel-solvant a été étudiée pour comprendre comment chacun de ces paramètres impacte les propriétés électrochimiques du système et en particulier la conductivité. Nous avons remarqué qu’un taux d’acrylonitrile élevé est favorable à une plus haute conductivité et que le solvant, de par son affinité avec le HNBR, est également à considérer.In this thesis, we have investigated an acrylonitrile-based polymer, HNBR (Hydrogenated Nitrile Butadiene Rubber), for its application in lithium ion batteries. This work relies on a partnership with the company Hutchinson (specialized in polymers) who was interested in developing a new process for the fabrication of electrodes. This melt-based process revealed problems regarding the polymer that is used as a binder for the electrodes as it needs to be compatible with the process as well as with the application in batteries. The aim of the thesis was therefore to find and validate a polymer meeting these requirements. Hence, HNBR was investigated. At first, we focused on the thermal treatment of HNBR, a key step of the melt-process. It was concluded that the thermal treatment leads to the cross-linking of HNBR, which is an asset because it increases the chemical stability of HNBR in the presence of the organic electrolyte. The following step was to introduce HNBR into the electrode formulation and investigate the performances of electrodes, made with the classical process and then with the melt process. It was found that HNBR is a good candidate to be introduced in an electrochemical system because it is stable over wide potential ranges and it allows interesting cycling and power performance. Faced with these findings, the last part of the study was to focus on analyzing the system more deeply by investigating the interactions between the HNBR polar functions, nitriles, and the lithium ions from the electrolyte. The ternary system polymer-salt-solvent was analyzed to understand the impact of each of these parameters on electrochemical properties, especially the conductivity. We noticed a high acrylonitrile content was beneficial to have a higher conductivity and that the solvent, regarding its affinity with HNBR, needs also to be considered

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Challenges in Solvent-Free Methods for Manufacturing Electrodes and Electrolytes for Lithium-Based Batteries

With the ever-growing energy storage notably due to the electric vehicle market expansion and stationary applications, one of the challenges of lithium batteries lies in the cost and environmental impacts of their manufacture. The main process employed is the solvent-casting method, based on a slurry casted onto a current collector. The disadvantages of this technique include the use of toxic and costly solvents as well as significant quantity of energy required for solvent evaporation and recycling. A solvent-free manufacturing method would represent significant progress in the development of cost-effective and environmentally friendly lithium-ion and lithium metal batteries. This review provides an overview of solvent-free processes used to make solid polymer electrolytes and composite electrodes. Two methods can be described: heat-based (hot-pressing, melt processing, dissolution into melted polymer, the incorporation of melted polymer into particles) and spray-based (electrospray deposition or high-pressure deposition). Heat-based processes are used for solid electrolyte and electrode manufacturing, while spray-based processes are only used for electrode processing. Amongst these techniques, hot-pressing and melt processing were revealed to be the most used alternatives for both polymer-based electrolytes and electrodes. These two techniques are versatile and can be used in the processing of fillers with a wide range of morphologies and loadings

Use of Solid-State NMR Spectroscopy for the Characterization of Molecular Structure and Dynamics in Solid Polymer and Hybrid Electrolytes

Solid-state NMR spectroscopy is an established experimental technique which is used for the characterization of structural and dynamic properties of materials in their native state. Many types of solid-state NMR experiments have been used to characterize both lithium-based and sodium-based solid polymer and polymer–ceramic hybrid electrolyte materials. This review describes several solid-state NMR experiments that are commonly employed in the analysis of these systems: pulse field gradient NMR, electrophoretic NMR, variable temperature T1 relaxation, T2 relaxation and linewidth analysis, exchange spectroscopy, cross polarization, Rotational Echo Double Resonance, and isotope enrichment. In this review, each technique is introduced with a short description of the pulse sequence, and examples of experiments that have been performed in real solid-state polymer and/or hybrid electrolyte systems are provided. The results and conclusions of these experiments are discussed to inform readers of the strengths and weaknesses of each technique when applied to polymer and hybrid electrolyte systems. It is anticipated that this review may be used to aid in the selection of solid-state NMR experiments for the analysis of these systems

Thermal and Electrochemical Properties of Solid Polymer Electrolytes Prepared via Lithium Salt-Catalyzed Epoxide Ring Opening Polymerization

Solid polymer electrolytes have been widely proposed for use in all solid-state lithium batteries. Advantages of polymer electrolytes over liquid and ceramic electrolytes include their flexibility, tunability and easy processability. An additional benefit of using some types of polymers for electrolytes is that they can be processed without the use of solvents. An example of polymers that are compatible with solvent-free processing is epoxide-containing precursors that can form films via the lithium salt-catalyzed epoxide ring opening polymerization reaction. Many polymers with epoxide functional groups are liquid under ambient conditions and can be used to directly dissolve lithium salts, allowing the reaction to be performed in a single reaction vessel under mild conditions. The existence of a variety of epoxide-containing polymers opens the possibility for significant customization of the resultant films. This review discusses several varieties of epoxide-based polymer electrolytes (polyethylene, silicone-based, amine and plasticizer-containing) and to compare them based on their thermal and electrochemical properties

DsRed-mediated oligomerization stabilizes HMGB1 on chromatin in vivo and on DNA in vitro

International audienceHigh-mobility group box-1 (HMGB1) is remarkably mobile in living cells, which reflects its ability to interact only transiently with both DNA and protein. This property is likely essential for HMGB1 nuclear activities. Nonetheless the weak interaction of HMGB1 with DNA and/or protein partners has also been a major limitation for investigating HMGB1 subnuclear localisation and for the identification of HMGB1 containing complexes by conventional biochemical approaches. In the present study, FRAP experiments demonstrated that DsRed-mediated oligomerization strongly reduces HMGB1 mobility due to an increased affinity for cellular chromatin. Moreover, oligomerized DsRed HMGB1 exhibited a higher affinity for supercoiled DNA in vitro compared to its monomeric counterpart. These results indicate that DsRed-meditated oligomerization is prone to stabilize labile interactions involving HMGB1 both in vivo and in vitro

La constitution des autorités numériques dans la production et la circulation de l’information

Ce dossier ouvre la complexité de la notion d’autorité aux sciences de l’information et de la communication. Ce concept est utilisépar notre discipline, essentiellementpour étudierl'accès et le partage de l'information, l’organisation des connaissances, la communication organisationnelle et les travaux sur l’e-réputation. Les travaux sélectionnés et publiés dans ce numéro remettent en perspective les liens entre légitimité et autorité, reconnaissance et signatures énonciatives, visibilité et réputation à l’heure des plateformes du web. Les terrains d’investigation représentés se situent dans la communication culturelle, politique et médiatique ainsi que dans celui du document numérique