1,721,094 research outputs found
High energy density all-solid-state batteries
No full textLes travaux de recherche de cette thèse s'inscrivent dans la dynamique industrielle du développement de batteries-tout-solide pour, premièrement, remplacer les électrolytes liquides des batteries Li-ion qui contiennent des solvants organiques inflammables, et deuxièmement, utiliser du lithium métallique comme anode afin d'améliorer la densité d'énergie massique et/ou volumique de la cellule. Pour cela, le composé Li6PS5Cl a été synthétisé et utilisé comme électrolyte solide dans des batteries assemblées par compression uniaxiale de poudres à température ambiante (voie sèche). Des verrous scientifiques et technologiques ont été identifiés lors de cette étude : les réactions parasites entre électrolyte et matériau actif impliquant la protection de ce dernier par un enrobage inerte, ou encore l'importance du contrôle de la pression lors de l'assemblage et du cyclage de la batterie. Une dimension plus industrielle a été donnée au projet par la suite avec des essais de mise en solution de l'électrolyte solide, dans l'optique de développer un procédé d'enduction d'électrodes par voie liquide, plus adapté aux lignes de production des batteries actuelles. La suspension des particules dans un solvant a montré ses limites, et nous avons fait le choix de la dissolution de l'électrolyte. Cette étude largement discutée dans la dernière partie du manuscrit, a eu pour objectif de bien disperser l'électrolyte dans l'électrode composite, en plus de l'enrobage de la matière active par l'électrolyte solide, pour une meilleure percolation ioniqueThis thesis work belongs to the actual industrial dynamic around all-solid-state batteries developpement. We aim, firstly, to replace the liquid electrolytes by solid one in conventional Li-ion batteries, and secondly, to use lithium metal as anode material for more volumetric and gravimetric energy density. For this purpose, the Li6PS5Cl compound was synthesised and used as solid electrolyte in dry-assembled batteries obtained by uniaxial compression of powders at room temperature. Scientific and technological issues were identified during this study : parasitic reactions between electrolyte and active material involving the protection of the latter by an inert coating, and/or the importance of pressure control during battery assembly and cycling. For a future industrial application, we tried to formulate our electrodes in wet/liquid process as the conventional Li-ion batteries. The suspension of particles in a solvent has shown its limits and we have chosen to dissolve the solid electrolyte in the mixing step. This study, widely discussed in the last part of the manuscript, aimed to properly disperse the electrolyte in the electrode composite, in addition to the coating of the active material's particles by the solid electrolyte, for better ionic percolatio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Développement du "SEM in situ/operando" et son application à l'étude des "défis interfaciaux" associés aux "batteries solides à base de métal Li"
No full textUne batterie dite "tout solide" utilise des électrodes solides et des électrolytes solides (ES) au lieu d'électrolytes liquides. L'un des principaux défis depuis plusieurs décennies est l'impossibilité d'utiliser le lithium métal comme anode pour les batteries à électrolyte liquide pour des raisons de sécurité. Cependant, c'est le métal qui possède la capacité spécifique théorique la plus élevée et le potentiel de réduction le plus faible. Ainsi, son utilisation comme anode permettrait de maximiser la densité énergétique. Avec les progrès des électrolytes solides dont certains dépassent la conductivité ionique des électrolytes liquides commerciaux, il y a un nouvel espoir de pouvoir enfin l'utiliser comme électrode tout en assurant la sécurité. Cependant, la route vers le succès des batteries tout solide est parsemée de défis notamment au niveau des "interfaces solide-solide". L'objectif de ce travail de doctorat est de contribuer à la compréhension fondamentale existante des défis interfaciaux en utilisant une cellule développée en interne pour réaliser des expériences de microscopie électronique à balayage (MEB) in situ/operando. Parmi les différentes techniques utilisées pour comprendre les défis posés par les batteries, la microscopie électronique à balayage (MEB) offre un bon compromis en termes de taille et de résolution d'observation avec la possibilité de réaliser des études avec une bonne résolution spatiale. En combinant l'imagerie avec des analyses chimiques par spectroscopie à dispersion d'énergie aux rayons X (EDX), une étude complète des modifications morphologiques et chimiques est possible. Pour compléter la compréhension des résultats obtenus par in situ/operando SEM, de la spectroscopie d'impédance électrochimique (EIS) a été réalisée pour obtenir des informations supplémentaires du point de vue électrochimiqueA Solid-state battery uses solid electrodes and Solid Electrolytes (SEs) instead of liquid electrolytes. One of the key challenges for decades has been the inability to use Li metal as an anode for liquid electrolyte-based batteries for safety reasons. Li has the highest theoretical specific capacity and lowest reduction potential. Thus using Li as an anode ensures maximizing the energy density. With advances in the SEs exceeding the ionic conductivity of commercial liquid electrolytes, there’s new emerging hope to finally use Li metal anodes. Thus the key motive for implementing SEs is to ensure safety and use the "Holy grail" Li metal anode. However, the road to the success of Li-solid state batteries is full of "solid-solid interfacial challenges". The goal of this PhD work is to contribute to the existing fundamental understanding of interfacial challenges using the in-house developed cell to perform in situ/operando scanning electron microscopy (SEM). Among different techniques being used to understand the fundamentals of battery challenges, scanning electron microscopy (SEM) offers a good compromise in terms of size and resolution of observation with the possibility to perform studies with a good spatial resolution. By combining the imaging with chemical analyses by X-ray energy dispersive spectroscopy (EDX), a complete survey of morphological and chemical modification is possible. The understanding from in situ/ SEM has been coupled with Electrochemical Impedance Spectroscopy (EIS) to gain further insights from the electrochemical point of vie
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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