1,721,053 research outputs found
Safer electrolyte components for rechargeable batteries
No full textAmong the electrochemical energy storage systems, rechargeable lithium batteries are considered very promising candidates for the next generation power sources because of their high gravimetric and volumetric energy density with respect to other cell chemistries. The lithium-ion battery technology is based on the use of electrode materials able to reversibly intercalate lithium cations, which are continuously transferred between two host structures (negative and positive electrodes) during the charge and discharge processes. Commercial lithium-ion batteries commonly use liquid electrolytes based on suitable lithium salts (solute) and organic compounds (solvents). The latter, volatile and flammable, represent serious concerns for the safety of the electrochemical devices, this so far preventing their large diffusion in applications as automotive, storage from renewable sources, smart grids. One of the most appealing approaches is the partial or total replacement of the organic solvents with safer, less hazardous, electrolyte components. Here, a concise survey of ones of the most investigated types of alternative electrolyte components, proposed for safer and more reliable rechargeable lithium batteries, is reported. Graphical Abstract
Managing transport properties in composite electrodes/electrolytes for all-solid-state lithium-based batteries
No full textIn the global competition for ultimate electrochemical energy storage systems, the increasing tendency of original equipment manufacturers (OEM) worldwide is to consider solid-state technology as a solution to replace the current Li-ion batteries operating with liquid electrolytes. The reason for this is the need of enhanced energy density batteries which are also durable and inherently safe. Proper understanding of the electrode/electrolyte interface is of paramount importance for this purpose. Indeed, all-solid-state lithium-based secondary batteries require efficient ion conductive pathways through the whole thickness of the electrode to properly access all the active material particles, thus providing full electrode capacity. In this respect, here, we propose an overview of the strategies adopted to achieve this goal, including polymeric and inorganic ion conductors and composites thereof as well as their preparation procedures and characterisation techniques, which currently represent highly important topics in the academic/industrial community to provide solutions for the shortcomings of poor safety, low ion mobility and short cycle life
Ionic liquid electrolytes for safer and more reliable sodium battery systems
Full text linkNa+-conducting, binary electrolytic mixtures, based on 1-ethyl-3-methyl-imidazolium, trimethyl-butyl-ammonium, and N-alkyl-N-methyl-piperidinium ionic liquid (IL) families, were designed and investigated. The anions were selected among the per(fluoroalkylsulfonyl)imide families. Sodium bis(trifluoromethylsulfonyl)imide, NaTFSI, was selected as the salt. The NaTFSI-IL electrolytes, addressed to safer sodium battery systems, were studied and compared in terms of ionic conductivity and thermal stability as a function of the temperature, the nature of the anion and the cation aliphatic side chain length. Room temperature conductivities of interest for sodium batteries, i.e., largely overcoming 10-4 or 10-3 S cm-1, are displayed. Similar conduction values are exhibited by the EMI-based samples even below -10 °C, making these electrolyte mixtures potentially appealing also for low temperature applications. The NaTFSI-IL electrolytes, with the exception of the FSI-ones, are found to be thermally stable up to 275 °C, depending on the nature of the cation and/or anion, thus extending their applicability above 100 °C and remarkably increasing the reliability and safety of the final device, especially in the case of prolonged overheating
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
Explorative Approaches for Safer, Scalable, Lithium Battery Solid Electrolyte Technologies
No full textOne of the main drawbacks of commercial lithium-ion batteries is the safety issue because of the hazardous organic electrolyte compounds, especially in case of electric and/or mechanical abuse. With the aim of overcoming this limitation, two synergic approaches have been followed: i) replacement of the organic solvents with innovative, non-volatile and non-flammable fluids (ionic liquids); ii) confinement of the ionic liquid electrolytes within suitable polymeric hosts for obtaining solid-state, ionically conducting membranes. In the present work, the attention has been focused on the N1114FSI, EMIFSI and PYR14TFSI ionic liquids (combined with the LiTFSI salt), and the electro-spun PSU, PAN/PCL and PAN/PCL-OLG polymer hosts. This study presents an explorative approach for developing innovative thin-layer, solvent-free, scalable polymer electrolyte technologies from the safety and engineering points of views
Influence of Alkyl Chain Length on Microscopic Configurations of the Anion in the Crystalline Phases of PYR1A-TFSI
No full textThe infrared spectra and their temperature dependence are
measured for a series of pyrrolidinium based ionic liquids (ILs) sharing the
bis(trifluoromethanesulfonyl)imide (TFSI) anion and having alkyl chains of
different length. While in the liquid or glassy state, both conformers of TFSI are
retained for all compounds, in the solid state a strong predominance of trans-TFSI
occurs in ionic liquids with alkyl chains shorter than five C−H groups; on the
contrary, for alkyl chain longer than six C−H groups crystalline phases display only
cis-TFSI, which is a rare configuration in solids. Moreover, a mixed system
composed of a short chain liquid (PYR14-TFSI) with one having a longer chain
(PYR18-TFSI) in a mass ratio of 1:1 is studied. The competition between the two
conformers of TFSI hinders the crystallization and gives rise to a glass transition
around 183 K
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
Ionic liquid electrolytes for room temperature sodium battery systems
No full textSafer electrolytes for ambient temperature sodium batteries were prepared by blending the N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, PYR 14 TFSI, ionic liquid with the sodium bis(trifluoromethylsulfonyl)imide, NaTFSI, salt. The physicochemical as well as the electrochemical properties of the PYR 14 TFSI-NaTFSI binary electrolyte system were investigated as a function of the temperature and sodium salt mole fraction, and compared with those of organic electrolytes of interest for sodium batteries. A plethora of characterization techniques were adopted ranging from density, viscosity and conductivity measurements, thermogravimetry and electrochemical methods (linear sweep voltammetry, transference number, galvanostatic experiments). Preliminary galvanostatic cycling tests were carried out in Na/NaMnO 2 cells at room temperature. The results are presented and discussed in the present paper
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