1,721,011 research outputs found
Lithium-oxygen batteries: the significance of the electrolyte and the use of soluble catalysts
No full textResearch has been carried out into lithium-oxygen cells over the last 20 years in an effort to develop the next generation of energy storage devices. Due to the high theoretical specific capacity of lithium peroxide, 1165 mAh . g-1Li2O2, lithium-oxygen cells promise to deliver high specific energy devices. However, their development has been hampered by several issues, including degradation reactions primarily initiated by the reactive superoxide radical, an intermediate reduction product of oxygen. Another issue is the slow kinetics of both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). In this work the use of in situ SERS spectroscopy as a method for monitoring the degradation of electrolytes has been investigated. It was demonstrated that it was possible to monitor the formation of superoxide in two ionic liquids. As the experiment progressed it was possible to monitor the formation of breakdown products resulting from degradation reactions in one ionic liquid, while in the second ionic liquid it was possible to observe the formation of lithium peroxide, the desired discharge product.The use of soluble redox catalyst for both the ORR and OER offers many advantages in lithium-oxygen cells. This is primarily a result of the nature of the lithium peroxide discharge product. As it is both insoluble and insulating, it forms a deposit on the electrode surface that limits the cell performance. In this work we have demonstrated techniques that can be used to assess the performance of potential soluble redox catalysts. Based on their standard potentials and their Gibbs free energy of reaction ethyl viologen was identified as being a suitable redox catalyst of the ORR, while cobalt terpyridine (CoTerpy) was identified as being a suitable catalyst of both the ORR and the OER. However, experimental results showed that while ethyl viologen was an efficient mediator of the ORR CoTerpy was not able to mediate the ORR or the OER
A redox shuttle to facilitate oxygen reduction in the lithium air battery
No full textA novel design of the non-aqueous lithium air cell is presented with a demonstration of a new reaction concept, involving a soluble redox shuttle to catalyse oxygen reduction. In principle, this can relieve the requirement for fast diffusion of molecular oxygen from the air interface to the positive electrode. To demonstrate this concept, ethyl viologen ditriflate was dissolved in BMPTFSI, reduced at a carbon electrode and regenerated by aspiration with oxygen. Useful shuttle behaviour, confirmed by several reduction–oxidation cycles, was observed in the case where the electrolyte contained at least 0.3 M lithium salt. The beneficial effect of the salt was attributed to its critical role in converting superoxide, which would otherwise destroy the shuttle, into the more desirable product of oxygen reduction, lithium peroxide.<br/
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
Dataset for In situ Phase Behaviour of a High Capacity LiCoPO4 Electrode During Constant or Pulsed Charge of a Lithium Cell
No full textData files in support of:
Palmer, Michael et al (2016) In situ Phase Behaviour of a High Capacity LiCoPO4 Electrode During Constant or Pulsed Charge of a Lithium Cell. Chemical Communications (doi:10.1039/C6CC07756K).</span
An in-situ Raman study of the oxygen reduction reaction in ionic liquids
No full textIn-situ Raman spectroscopy is applied, for the first time, to elucidate the reaction products of oxygen reduction in two types of ionic liquids: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C2mimTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr14TFSI). The degradation of C2mimTFSI by superoxide attack is evidenced by the appearance of bands characteristic of amide and carbonate compounds. On the contrary, Pyr14TFSI is found to be resistant towards degradation. It is observed that superoxide is the first product of oxygen reduction in Pyr14TFSI, and the formation of Li2O2 is observed at longer time
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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