1,720,967 research outputs found
Abnormal self-discharge in lithiom-ion batteries
No full textLithium-ion batteries are expected to serve as a key technology for large-scale energy storage systems
(ESSs), which will help satisfy recent increasing demands for renewable energy utilization. Besides their
promising electrochemical performance, the low self-discharge rate (o5% of the stored capacity over
1 month) of lithium-ion batteries is one of their most significant advantages for ESSs. Herein, contrary to
conventional belief, we report that the self-discharge of LIBs can be abnormally accelerated when the
battery has been exposed even to a routine short-term thermal exposure. We demonstrate that this
thermal ‘history’ in addition to the temperature itself is memorized in the battery and accelerates the
self-discharge rate. The series of characterizations performed in our work reveal that the electrolyte salt
acts as a strong oxidizing agent by vigorously damaging the surface of the cathode, producing an
internal ‘parasitic’ lithium source that continuously supplies lithium for the self-discharge. Although it is
widely known that battery operation at elevated temperature generally induces faster degradation of
capacity over multiple cycles, the key finding here is that not only the operation temperature but also
the ‘thermal history’ of the battery should be carefully considered because this history remains and
continues to affect the self-discharge rate afterwards. The self-discharge of LIBs has remained largely neglected; however, our findings suggest that close attention must be paid to the self-discharge of LIBs applied to large-scale ESSs, which, unlike mobile electronic devices, will be exposed to various outdoor temperature conditions.
© The Royal Society of Chemistry 201
Using First-Principles Calculations for the Advancement of Materials for Rechargeable Batteries
No full textRechargeable batteries have been regarded as leading candidates for energy storage systems to satisfy soaring energy demands and ensure efficient energy use, and intensive efforts have thus been focused on enhancing their energy densities and power capabilities. First-principles calculations based on quantum mechanics have played an important role in obtaining a fundamental understanding of battery materials, thus providing insights for material design. In this feature article, the theoretical approaches used to determine key battery properties, such as the voltage, phase stability, and ion-diffusion kinetics, are reviewed. Moreover, the recent contribution of first-principles calculations to the interpretation of complicated experimental characterization measurements on battery materials, such as those obtained using X-ray absorption spectroscopy, electron energy-loss spectroscopy, nuclear magnetic resonance spectroscopy, and transmission electron microscopy, are introduced. Finally, perspectives are provided on the research direction of first-principles calculations for the development of advanced batteries, including the further development of theories that can accurately describe the dissolved species, amorphous phases, and surface reactions that are integral to the operation of future battery systems beyond Li-ion batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim1331sciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Coupling structural evolution and oxygen-redox electrochemistry in layered transition metal oxides
No full textLattice oxygen redox offers an unexplored way to access superior electrochemical properties of transition metal oxides (TMOs) for rechargeable batteries. However, the reaction is often accompanied by unfavourable structural transformations and persistent electrochemical degradation, thereby precluding the practical application of this strategy. Here we explore the close interplay between the local structural change and oxygen electrochemistry during short- and long-term battery operation for layered TMOs. The substantially distinct evolution of the oxygen-redox activity and reversibility are demonstrated to stem from the different cation-migration mechanisms during the dynamic de/intercalation process. We show that the pi stabilization on the oxygen oxidation initially aids in the reversibility of the oxygen redox and is predominant in the absence of cation migrations; however, the pi-interacting oxygen is gradually replaced by sigma-interacting oxygen that triggers the formation of O-O dimers and structural destabilization as cycling progresses. More importantly, it is revealed that the distinct cation-migration paths available in the layered TMOs govern the conversion kinetics from pi to sigma interactions. These findings constitute a step forward in unravelling the correlation between the local structural evolution and the reversibility of oxygen electrochemistry and provide guidance for further development of oxygen-redox layered electrode materials. Transition metal oxide electrodes are promising for rechargeable batteries but are subject to suffer from structural transformations and electrochemical degradation. The evolution of oxygen-redox activity and reversibility in layered electrodes are shown to arise from cation-migration mechanisms during de/intercalation
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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
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