1,720,964 research outputs found
Valorisation of argan seeds: Production of cathode material for high-performance lithium-sulphur batteries
Full text linkPorous carbon is considered a key factor in mitigating the shuttle effect, which remains one of the biggest challenges to developing lithium-sulphur (Li-S) batteries. Reusing agricultural waste as a raw material is a sustainable and eco-friendly source for producing carbon. Here we propose fabricating carbonaceous material from argan shells by simple pyrolysis. The synthesis of argan shell carbon (ASC) involved a straightforward approach with non-activating pyrolysis. Carbonisation at three different temperatures was employed to obtain ASC. A high sulphur loading of 70 % was incorporated into the ASC using the melt diffusion method, resulting in the formation of three different sulphur‑carbon composites (ASC@S). All of the prepared materials were characterised and evaluated as cathodes for Li-S batteries. The electrochemical performance of composites was compared, and ASC-800@S was identified as the best-performing composite. Thanks to its excellent properties this material combines (surface area, pore volume, conductivity), it delivers a capacity of 674 mAh g−1 and 513 mAh g−1 after 500 cycles at C/10 and 1C rate, respectively. This work provides a simple, economical, and effective strategy for preparing advanced carbonaceous sulphur host materials and significant improvement of Li-S cell performance.Fil: Marri, Imane. Universidad de Córdoba; EspañaFil: Edfouf, Zineb. No especifíca;Fil: Caballero, Alvaro. Universidad de Córdoba; EspañaFil: Tesio, Alvaro Yamil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Desarrollo en Materiales Avanzados y Almacenamiento de Energía de Jujuy - Universidad Nacional de Jujuy. Centro de Investigación y Desarrollo en Materiales Avanzados y Almacenamiento de Energía de Jujuy - Gobierno de la Provincia de Jujuy. Centro de Investigación y Desarrollo en Materiales Avanzados y Almacenamiento de Energía de Jujuy; Argentin
Study of a new Si/Sn Ni/Al/C composite material used as negative electrode for lithium ion batteries
No full textCe mémoire est consacré à l'étude de nouveaux matériaux composites de type Si/Sn-Ni/Al/C pour former des électrodes négatives de batteries lithium ion. La microstructure de ces matériaux se présente sous la forme de nanoparticules de Si enrobées dans une matrice conductrice constituée de carbone et d'un composé intermétallique Ni3,4Sn4. La nanostructure et la composition du matériau composite lui confèrent de très bonnes performances en termes de capacité réversible, de stabilité électrochimique, et de cinétique de réaction. La mécanosynthèse a été choisie comme méthode d'élaboration. Les propriétés structurales et chimiques du composite ont été déterminées par analyses DRX, par microscopies électroniques MET et MEB, par analyses EDX et EFTEM et par spectroscopie Mössbauer de 119Sn. La caractérisation électrochimique a été réalisée par cyclage galvanostatique et par voltamétrie cyclique. La réactivité de ces matériaux envers le lithium a été étudiée par analyses DRX et spectroscopie Mössbauer de 119Sn in-situ. Ce mémoire détaille les résultats structuraux et électrochimiques obtenus pour différents matériaux composites basés sur Ni3,4Sn4 en ajoutant les éléments C, Al et Si. Une étude des mécanismes réactionnels lors du broyage mécanique ainsi que pendant le cyclage électrochimique a été effectuée et le rôle des différents éléments a été mis en évidence. Enfin, une discussion sur l'influence de la microstructure sur les performances électrochimiques des matériaux composites est donnée. Les meilleures performances électrochimiques sont obtenues pour le composite de composition nominale Ni0,14Sn0,17Si0,32Al0,04C0,35. Il présente une capacité réversible de 920 mAh/g avec une très bonne stabilité sur 280 cycles. Le matériau possède une excellente cinétique de délithiation : 90% de la capacité peut être délivrée en moins de 5 minutes. La capacité irréversible (20%) reste toutefois élevée et doit être encore améliorée en stabilisant l'interface solide/électrolyte (SEI)This study is devoted to a new Si/Sn-Ni/Al/C composite material usable as negative electrode for lithium-ion batteries. The composite microstructure is made from Si nanoparticles embedded in a matrix, consisting of conductive carbon and Ni3.4Sn4 intermetallic compound. The nanostructure and composition of the composite material give excellent properties regarding reversible capacity, electrochemical stability, and reaction kinetics. Mechanical alloying has been chosen as synthesis method. The material structural and chemical properties have been determined by XRD analysis, by electron microscopy TEM and SEM, by EDX and EFTEM analysis and 119Sn Mössbauer spectroscopy. The electrochemical characterization was carried out by galvanostatic cycling and cyclic voltammetry. Lithium reactivity of these materials was studied by in-situ XRD analysis and 119Sn Mössbauer spectroscopy. This manuscript details the structural and electrochemical results obtained from various composite materials based on Ni3.4Sn4 by adding C, Al and Si elements. Reaction mechanisms during mechanical alloying and during electrochemical cycling have been investigated and the role of the different elements has been demonstrated. Finally, a discussion of the microstructure influence on the electrochemical performance of the composite materials is given. The best electrochemical properties are obtained for the composite material with nominal composition Ni0.14Sn0.17Si0.32Al0.04C0.35, which has a reversible capacity of 920 mAh/g with a very good stability of 280 cycles. Excellent kinetics during délithiation are obtained : 90% of capacity can be delivered in less than 5 minutes. However, the irreversible capacity (20 %) remains high and should be improved by stabilizing the solid/electrolyte interface (SEI
Étude de nouveaux matériaux composites de type Si/Sn Ni/Al/C pour électrode négative de batteries lithium ion
No full textThis study is devoted to a new Si/Sn-Ni/Al/C composite material usable as negative electrode for lithium-ion batteries. The composite microstructure is made from Si nanoparticles embedded in a matrix, consisting of conductive carbon and Ni3.4Sn4 intermetallic compound. The nanostructure and composition of the composite material give excellent properties regarding reversible capacity, electrochemical stability, and reaction kinetics. Mechanical alloying has been chosen as synthesis method. The material structural and chemical properties have been determined by XRD analysis, by electron microscopy TEM and SEM, by EDX and EFTEM analysis and 119Sn Mössbauer spectroscopy. The electrochemical characterization was carried out by galvanostatic cycling and cyclic voltammetry. Lithium reactivity of these materials was studied by in-situ XRD analysis and 119Sn Mössbauer spectroscopy. This manuscript details the structural and electrochemical results obtained from various composite materials based on Ni3.4Sn4 by adding C, Al and Si elements. Reaction mechanisms during mechanical alloying and during electrochemical cycling have been investigated and the role of the different elements has been demonstrated. Finally, a discussion of the microstructure influence on the electrochemical performance of the composite materials is given. The best electrochemical properties are obtained for the composite material with nominal composition Ni0.14Sn0.17Si0.32Al0.04C0.35, which has a reversible capacity of 920 mAh/g with a very good stability of 280 cycles. Excellent kinetics during délithiation are obtained : 90% of capacity can be delivered in less than 5 minutes. However, the irreversible capacity (20 %) remains high and should be improved by stabilizing the solid/electrolyte interface (SEI)Ce mémoire est consacré à l'étude de nouveaux matériaux composites de type Si/Sn-Ni/Al/C pour former des électrodes négatives de batteries lithium ion. La microstructure de ces matériaux se présente sous la forme de nanoparticules de Si enrobées dans une matrice conductrice constituée de carbone et d'un composé intermétallique Ni3,4Sn4. La nanostructure et la composition du matériau composite lui confèrent de très bonnes performances en termes de capacité réversible, de stabilité électrochimique, et de cinétique de réaction. La mécanosynthèse a été choisie comme méthode d'élaboration. Les propriétés structurales et chimiques du composite ont été déterminées par analyses DRX, par microscopies électroniques MET et MEB, par analyses EDX et EFTEM et par spectroscopie Mössbauer de 119Sn. La caractérisation électrochimique a été réalisée par cyclage galvanostatique et par voltamétrie cyclique. La réactivité de ces matériaux envers le lithium a été étudiée par analyses DRX et spectroscopie Mössbauer de 119Sn in-situ. Ce mémoire détaille les résultats structuraux et électrochimiques obtenus pour différents matériaux composites basés sur Ni3,4Sn4 en ajoutant les éléments C, Al et Si. Une étude des mécanismes réactionnels lors du broyage mécanique ainsi que pendant le cyclage électrochimique a été effectuée et le rôle des différents éléments a été mis en évidence. Enfin, une discussion sur l'influence de la microstructure sur les performances électrochimiques des matériaux composites est donnée. Les meilleures performances électrochimiques sont obtenues pour le composite de composition nominale Ni0,14Sn0,17Si0,32Al0,04C0,35. Il présente une capacité réversible de 920 mAh/g avec une très bonne stabilité sur 280 cycles. Le matériau possède une excellente cinétique de délithiation : 90% de la capacité peut être délivrée en moins de 5 minutes. La capacité irréversible (20%) reste toutefois élevée et doit être encore améliorée en stabilisant l'interface solide/électrolyte (SEI
Green biomass-derived hierarchically porous non-activated carbon from carob waste for high-performance lithium-sulfur batteries
No full textTo expedite the development of lithium-sulfur (Li–S) battery technology, it is necessary to address the inherent technological hurdles surrounding sulfur-based cathodes, including mitigating the shuttle effect and enhancing the electrical conductivity of sulfur. The use of biomass-derived carbonaceous materials offers a promising avenue to alleviate these challenges and help reduce the carbon footprint associated with battery technologies. Herein, we report the green synthesis of carob-derived carbonaceous material without additional physical/ chemical activation steps, making the process sustainable, affordable, and eco-friendly. The obtained carobderived carbon (CC) offers a hierarchical micro/meso/macroporous structure with a high surface area of 633 m2 g− 1. The electrochemical performance with a sulfur content of 70% (CC@S70) in the composite and a sulfur mass loading of 1 mg cm− 2 delivers an initial discharge capacity of 1405 mAh g− 1, reducing to 798 mAh g− 1 after 260 cycles. Increasing the sulfur content to 90% in the cathode (CC@S90) yields a high capacity in Li–S cells, reaching a discharge capacity of 937 mAh g− 1 with a sulfur loading of 2 mg cm− 2 at 0.3C (1C = 1675 mA g− 1) after 100 cycles. The improved performance can be attributed to the well-preserved interconnected pores within the carbon material, serving as an efficient framework to accommodate high sulfur content.Fil: Zoubir, Otmane. Mohammed Vth University in Rabat; MarruecosFil: Lallaoui, Abdelfettah. No especifíca;Fil: Edfouf, Zineb. Mohammed Vth University in Rabat; MarruecosFil: Caballero, Alvaro. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy. - Universidad Nacional de Jujuy. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy. - Gobierno de la Provincia de Jujuy. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy; ArgentinaFil: Tesio, Alvaro Yamil. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy. - Universidad Nacional de Jujuy. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy. - Gobierno de la Provincia de Jujuy. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy; Argentin
Étude de nouveaux matériaux composites de type Si/Sn Ni/Al/C pour électrode négative de batteries lithium ion
No full textCe mémoire est consacré à l'étude de nouveaux matériaux composites de type Si/Sn-Ni/Al/C pour former des électrodes négatives de batteries lithium ion. La microstructure de ces matériaux se présente sous la forme de nanoparticules de Si enrobées dans une matrice conductrice constituée de carbone et d'un composé intermétallique Ni3,4Sn4. La nanostructure et la composition du matériau composite lui confèrent de très bonnes performances en termes de capacité réversible, de stabilité électrochimique, et de cinétique de réaction. La mécanosynthèse a été choisie comme méthode d'élaboration. Les propriétés structurales et chimiques du composite ont été déterminées par analyses DRX, par microscopies électroniques MET et MEB, par analyses EDX et EFTEM et par spectroscopie Mössbauer de 119Sn. La caractérisation électrochimique a été réalisée par cyclage galvanostatique et par voltamétrie cyclique. La réactivité de ces matériaux envers le lithium a été étudiée par analyses DRX et spectroscopie Mössbauer de 119Sn in-situ. Ce mémoire détaille les résultats structuraux et électrochimiques obtenus pour différents matériaux composites basés sur Ni3,4Sn4 en ajoutant les éléments C, Al et Si. Une étude des mécanismes réactionnels lors du broyage mécanique ainsi que pendant le cyclage électrochimique a été effectuée et le rôle des différents éléments a été mis en évidence. Enfin, une discussion sur l'influence de la microstructure sur les performances électrochimiques des matériaux composites est donnée. Les meilleures performances électrochimiques sont obtenues pour le composite de composition nominale Ni0,14Sn0,17Si0,32Al0,04C0,35. Il présente une capacité réversible de 920 mAh/g avec une très bonne stabilité sur 280 cycles. Le matériau possède une excellente cinétique de délithiation : 90% de la capacité peut être délivrée en moins de 5 minutes. La capacité irréversible (20%) reste toutefois élevée et doit être encore améliorée en stabilisant l'interface solide/électrolyte (SEI)This study is devoted to a new Si/Sn-Ni/Al/C composite material usable as negative electrode for lithium-ion batteries. The composite microstructure is made from Si nanoparticles embedded in a matrix, consisting of conductive carbon and Ni3.4Sn4 intermetallic compound. The nanostructure and composition of the composite material give excellent properties regarding reversible capacity, electrochemical stability, and reaction kinetics. Mechanical alloying has been chosen as synthesis method. The material structural and chemical properties have been determined by XRD analysis, by electron microscopy TEM and SEM, by EDX and EFTEM analysis and 119Sn Mössbauer spectroscopy. The electrochemical characterization was carried out by galvanostatic cycling and cyclic voltammetry. Lithium reactivity of these materials was studied by in-situ XRD analysis and 119Sn Mössbauer spectroscopy. This manuscript details the structural and electrochemical results obtained from various composite materials based on Ni3.4Sn4 by adding C, Al and Si elements. Reaction mechanisms during mechanical alloying and during electrochemical cycling have been investigated and the role of the different elements has been demonstrated. Finally, a discussion of the microstructure influence on the electrochemical performance of the composite materials is given. The best electrochemical properties are obtained for the composite material with nominal composition Ni0.14Sn0.17Si0.32Al0.04C0.35, which has a reversible capacity of 920 mAh/g with a very good stability of 280 cycles. Excellent kinetics during délithiation are obtained : 90% of capacity can be delivered in less than 5 minutes. However, the irreversible capacity (20 %) remains high and should be improved by stabilizing the solid/electrolyte interface (SEI)PARIS-EST-Université (770839901) / SudocSudocFranceF
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
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
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