1,721,084 research outputs found
Lithium dendrites in solid-state batteries - Where they come from and how to mitigate them
No full textA major contributor to global CO2 emissions is transportation and a transition to electric vehicles could lead to a significant reduction of those emissions. A roadblock in this transition are safety issues of electric vehicles. Namely that the batteries can burst into flames, be it in an accident or sometimes even without showing obvious signs during charging. This can be caused by filaments, also called dendrites growing within the battery causing a short circuit. By exchanging the flammable liquid electrolyte in the battery with a non-flammable solid one the safety aspect can be remedied. It also allows an increase of the battery capacity through the now viable use of lithium metal. This was deemed too dangerous with liquid electrolyte because lithium metal tends to form dendrites more easily which caused several accidents in the early advent of lithium-ion batteries. However, these dendrites can still form inside of solid electrolytes and while the consequences are less severe the possible lifetime of the battery is cut short.
Therefore, this work concerned itself with understanding the growth of dendrites in solid electrolytes, more specifically in the oxide based garnet Li7La3Zr2O12, and how to mitigate it. Starting with the influence of the charging mode of the cell on dendritic growth with the use of current pulses, increasing the charge rate. Followed by investigating the effect of altered near surface properties of the garnet via ion implantation, on the path of the dendrite. Finally x-ray microscopy observations into the environment close to the dendrite deliver more information what happens microscopically when the dendrite grows. Thus, bringing us closer to functional solid-state batteries without failure by dendrites
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
An operando 3D optical microscopy study on the Li metal anode formation in anode-less solid-state batteries
No full textFaststoffbatterier med metalliske litiumanoder har et stort potensiale til å betydelig øke ders energitetthet og har nylig fått mye oppmerksomhet. Komplekse og kostbare produksjonsprosesser hindrer imidlertid, for øyeblikket, deres kommersielle suksess. På den annen side finner man litiummetallbatterier uten overskudd av Li, såkalte ”anodefrie Li batterier”, som finner en måte å omgå disse problemene på, ved å elektroplettere Li-metallanoden in situ under den første oppladningen. Denne innovative tilnærmingen forenkler produksjonen ved å eliminere behovet for å håndtere Li, noe som fører til betydelige reduksjoner både i tid og kostnader. Likevel presenterer fraværet av et Li-reservoar i cellen et tveegget sverd; på den ene siden muliggjør det en potensiell fordobling av energitetthetene til dagens Li-ion-batterier, mens det på den andre siden innfører et krav om ultra-høy effekt ved hver ladesyklus for å forhinde unødvendig Li-forbruk. Videre kan ujevn vekst av Li føre til penetrering av faststoffelektrolytten, som utgjør en stor sikkerhetsrisiko, og er en betydelig begrensning i alle Li-metallbatterier. I denne studien adresserer vi derfor mulige løsninger for å overkomme disse utfordringene, spesifikt ved å undersøke effekten av trykk og legerende Mg-filmer på morfologien til avsatt Li. En spesialdesignet operando testcelle, kombinert med 3D-optisk mikroskopi, blir brukt for å studere litiumavsetning på en faststoff elektrolytt av type Li7La3Zr2O12. Det blir vist at Mg-filmer reduserer overpotensialet som kreves for å igangsette Li avsetning, og at trykk er helt essensielt for å unngå porer i disse Li formasjonene. Videre vises det at mekaniske og morfologiske egenskaper til de tynne, pletterte, strømkollektorene har stor påvirkning på Li-avsetningskarakteristikken. Disse funnene fremhever de lovende effektene av å implementere legerende filmer, samt at de impliserer viktigheten av å benytte tykkere, tettere strømkollektorer. Det konkluderes med at, til tross for problemene knyttet til Li avlegging i anodefritt design, så er det lovende fremskritt på vei for å muliggjøre mer jevne Li-lag, som dermed styrker deres posisjon innen avansert energilagring.Solid-state batteries incorporating lithium metal anodes exhibit great potential in boosting energy densities and have recently garnered substantial attention. However, their intricate and costly production processes currently hinder their commercial viability. Conversely, zero-excess lithium metal batteries, also known as ”anode-less Li batteries” provide a means of circumventing these issues by electrodepositing the Li metal anode in situ during the initial charge. This innovative approach streamlines production by eliminating the need to handle Li, leading to a considerable reduction in both time and cost expenses. Nevertheless, the absence of a Li reservoir in the cell presents a double-edged sword; on the one hand, enabling a potential doubling of state-of-the-art energy densities of Li-ion batteries, while on the other, being reliant on ultra-high cycling efficiencies to prevent detrimental Li consumption. Moreover, the inhomogeneous plating and safety concerns associated with Li penetration through the solid electrolyte pose a significant constraint in all Li metal cells. In this study, we address potential solutions to alleviate these challenges, specifically by investigating the impact of stack pressure and alloying Mg interlayers on the morphology of plated Li. A specially designed operando test cell, coupled with 3D-optical microscopy, is employed to examine lithium plating on garnet-type Li7La3Zr2O12 samples. It is found that Mg-interlayers reduce the overpotential needed to initiate Li deposition and that stack pressures are essential in preventing void formation in these deposits. Further, mechanical and morphological properties of the thin, deposited current collectors are shown to highly impact the Li plating characteristics. These findings highlight the promising effects of alloying interlayers, while also implicating the necessity of employing thicker and denser current collectors. It is concluded that, despite the plating issues exhibited by the ”anode-less” design, promising advancements in enabling more homogeneous deposition layers are underway, thereby enhancing their position in advanced energy storage applications
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
Phase-Engineering Closo-Borate Electrolytes and Optimizing Composite Cathode Tortuosity for All-Solid-State Na-S Batteries
No full textForskningen setter søkelys på å forbedre den elektrokjemiske ytelsen til natrium-svovel (Na-S) katodekompositter i faststoffbatterier ved å optimalisere den fastestoff elektrolytten og katodekomposisjonen. De høyt isolerende egenskapene til natrium-svovel skaper utfordringer for ionisk og elektrisk ledningsevne, som blir forsøkt å løse ved å inkludere høyt ledende natrium closo-hydroborat fastestoff elektrolytter (>1 mS/cm). Forskningen oppnådde den første rapporterte nesten rene «body-centered» kubiske fasen av Na4(B10H10)(B12H12), kjent for sin forbedrede ioniske ledningsevne, som ble bekreftet gjennom grundig røntgendiffraksjonsanalyse. Dette ble oppnådd ved kulemølling og påført trykk, som viste en økning i ledningsevne etter kulemølling, sammenlignet med urørt form.
Studien er definert av en grundig og omfattende eksperimentell metode, som sikrer pålitelighet og gyldighet av funnene. Na-S katodekompositter og de faste elektrolyttene ble nøye utviklet gjennom utforskning av ulike bearbeidingsmetoder for å identifisere de beste forholdene for å produsere et ensartet og godt integrert komposittmateriale. I tillegg ble ulike katodekomposisjoner produsert ved å justere forholdet mellom karbon og faste elektrolytt, med mål i å bestemme det optimale forholdet for forbedre den ioniske transporten, samt et godt trefasekontakt.
Avanserte karakteriseringsmetoder har spilt en avgjørende rolle i forskningen. Ex-situ røntgendiffraksjonsanalyse ble brukt til å analysere syntetiserte prøvers faserenhet og krystallografisk struktur. Skanningselektronmikroskopi ga detaljerte innsikter i komposittmaterialets mikrostruktur og morfologi, kritisk for å forstå de ioniske transports veiene. Videre ble Raman-spektroskopi og elektrokjemisk impedansspektroskopi brukt til å undersøke katodekomposittens kjemiske sammensetning og faststoff elektrolytten sin ionisk ledningsevne.
Ytelsen til den forbedrede Na-S katodekompositter ble vurdert gjennom galvanostatiske sykling og likestrømspolariseringstester. Disse testene ga viktig informasjon om stabiliteten til ladnings-utladningen, spesifikk kapasitet og coulombisk effektivitet. De innledende utladningskapasitetene ble registrert til å være over 1200 mAh/g, takket være tilsetningen av natrium closo-hydroborat fastestoff elektrolytt. Elektrolytten forbedret betydelig den ionisk ledningsevne og reduserte intern motstand i katoden. Den forbedrede ytelsen kan også tilskrives den optimaliserte mikrostrukturen, som muliggjør bedre ionetransport og kontakt med svovel innenfor komposittmaterialet.
En av de viktigste funnene er den kritiske rollen til mengden blanding for å bestemme ytelsen til Na-S katodekompositter. Mens høyenergi kulemølling effektivt oppnådde homogenitet, introduserte det materialedegradering, noe som forårsaket et kapasitetstap på >80\% etter 50 sykluser. Derfor var balansering av blanding og bevaring av materialets integritet avgjørende for optimal ytelse. I tillegg avslørte degraderingsmekanismene identifisert fra differentialkapasitet (dQ/dV) plottene dannelse av potentiselle ikke-ledende faser under sykling, og understreker behovet for gjennomtenkt materialbehandling og sammensetningsoptimalisering.
Denne studien bidrar til materialteknologi og elektrokjemi med betydelige implikasjoner for energilagring. Den understreker potensialet til natrium-svovel katodekompositter og natrium closo-hydroborat faststoff elektrolytter for å forbedre elektrokjemisk ytelse i faststoffbatterier. Funnene understreker levedyktigheten til Na-S katodekompositter som bærekraftige alternativer for energilagringssystemer i neste generasjon.The research focuses on improving the electrochemical performance of sodium-sulfur (Na-S) cathode composites in all-solid-state batteries by optimizing the solid electrolyte and cathode composition. The high-insulating nature of sodium-sulfur presents challenges for ionic and electrical conductivity, addressed by incorporating highly conductive sodium closo-hydroborate solid electrolytes (>1mS/cm). The research achieved the first reported nearly pure body-centered cubic (BCC) phase of Na4(B10H10)(B12H{12), known for its improved ionic conductivity, confirmed through rigorous X-ray diffraction analysis. This was achieved by ball-milling and applied pressure, showing an increase in conductivity after ball-milling, compared to pristine.
The study is defined by a thorough and comprehensive experimental approach, which ensures the reliability and validity of the findings. The Na-S cathode composite and the solid electrolytes were carefully developed through the exploration of various processing methods to identify the best conditions for producing a uniform and well-integrated composite material. In addition, different cathode compositions were created by adjusting the ratio of carbon and solid electrolytes, with the aim of determining the most effective combination for improved ionic transport and good triple-phase contact.
Advanced characterization techniques played a pivotal role in the research. Ex-situ X-ray diffraction analysis was utilized to analyze the synthesized materials' phase purity and crystallographic structure. Scanning Electron Microscopy provided detailed insights into the composites' microstructure and morphology, critical for understanding the ionic pathways. Furthermore, Raman spectroscopy and Electrochemical Impedance Spectroscopy were used to investigate the cathode composites' chemical composition and solid electrolytes's ionic conductivity.
The performance of the improved Na-S cathode composites was assessed through galvanostatic cycling and direct-current polarization tests. These tests provided important data on the stability of charge-discharge cycling, specific capacity, and coloumbic efficiency. The initial discharge capacities were recorded to be above 1200 mAh/g, thanks to the addition of sodium closo-hydroborate solid electrolytes. These electrolytes significantly improved ionic conductivity and reduced internal resistance. The enhanced performance can also be attributed to the optimized microstructure, which enables better ionic transport and sulfur contact within the composite material.
One of the key findings is the critical role of the degree of mixing in determining the performance of the Na-S cathode composites. While high-energy ball milling effectively achieved homogeneity, it induced material degradation, causing a capacity loss of >80\% after 50 cycles. Therefore, balancing mixing and preserving material integrity was essential for optimal performance. Additionally, the degradation mechanisms identified from the differential capacity (dQ/dV) plots revealed potentially the formation of non-conductive phases during cycling, emphasizing the need for careful material processing and composition optimization.
This study contributes to the fields of materials science and electrochemistry with significant implications for energy storage. It highlights the potential of sodium-sulfide cathode composites and sodium closo-hydroborate solid electrolytes to enhance electrochemical performance in all-solid-state batteries. The findings emphasize the viability of Na-S cathode composites as sustainable alternatives for next-generation energy storage systems
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