Study of Sulfur-Based Electrodes By in Situ Characterization Techniques
Notice bibliographique
Résumé
The lithium-sulfur (Li/S) battery system is one of the most promising candidates to become the successor of the current Li-ion battery. However, the insufficient cycle life of the Li/S batteries needs to be resolved before envisioning their commercial use. Several phenomena are reported to be involved in the capacity fading of the Li/S cells upon cycling, among which important structural changes in the sulfur electrode. Hence the constant need for understanding of those mechanisms drives the use of innovative in situ characterization techniques. In the present study, operando acoustic emission (AE) technique and in-situ synchrotron X-ray tomography and diffraction are used to study the degradation mechanism of sulphur-based electrodes depending of their formulation. To date, AE technique has been used to characterize the degradation mechanisms (crack growth, friction, delamination, matrix cracking, corrosion, etc) of various materials subjected to a stress by mechanical, pressure or thermal means. In the present work, AE technique is used for the first time to monitor the mechanical degradation of sulfur electrodes depending on the nature of the binder (polyvinylidene difluoride ( PVdF) compared to carboxymethylcellulose (CMC)) and the geometry of the current collector (flat Al foil compared to 3D porous carbon paper (CP)). In all cases, AE signals are mainly detected during the 1st plateau of the 1st discharge, related to the initial dissolution of elemental sulfur into the electrolyte, causing a collapse of the electrode network. At the end of charge, the formation of micrometric sulfur on the surface of the electrode can be acoustically detected, in particular in the case of the CMC/Al formulation, where signals are also detected during subsequent cycles. This is believed to be a result of the good adhesion of CMC-based electrode to the current collector, which allows acoustic waves to propagate through the electrode to the AE sensor more easily. However, with CP current collector, no AE activity is detected upon charge, reflecting a lower mechanical stress attributed to a more homogeneous growth of the S particles in the electrode. It is also noted that inefficient electrode formulation/elaboration can be detected via AE, as AE signals are emitted at the end of the discharge when the cell polarizes more than usually observed. The use of CP as a current collector greatly improves the electrochemical performance of the cells, especially when combined with the better adhesion/cohesion strengths of CMC binder, reaching an initial capacity of 1180 mAh g-1 (~4.5 mAh cm-2) stabilizing around 860 mAh g-1 after 50 cycles. X-Ray computed tomography (XRCT) is certainly one of the most powerful analytical tools enabling non-destructive 3D imaging of objects with complex and porous morphologies such as S-based electrodes. Using appropriate image processing, segmentation and analysis procedures, quantitative parameters can be extracted such as the volume fraction, the size distribution, the connectivity and the geometrical tortuosity of the constitutive phases of the sulfur electrodes. A spatial resolution of a few tens of nm can be reached with a synchrotron X-ray source. This technique, coupled with in situ synchrotron X-ray diffraction, enables to follow in great details the evolution of the different species inside the tested Li/S batteries and get invaluable information on their degradation mechanisms. In the present study, in-situ synchrotron X-ray tomography and diffraction is used to investigate the structural changes upon cycling of sulfur electrodes integrating a poly-electrolyte binder (PEB) likely to confine the polysulfide chains and prevent sulfur loss over cycling. Its behaviour is compared to a classic CMC-binder based electrode.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».