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Litiumioniakkujen sähkökemiallisen purun parantaminen rautapohjaisten redox-parielektrolyyttien avulla
No full textThe demand for lithium-ion batteries (LIB) is increasing rapidly around the world, driven especially by electrification of transport. This leads to increasing amounts of end-of-life LIBs in the future. LIBs contain both environmentally hazardous materials and valuable finite metals and therefore, efficient recycling methods are needed. However, a major obstacle in LIB recycling is that spent LIBs often contain residual energy, which can lead to fires and explosions during the recycling process. Electrochemical discharge using salt solutions is reported to completely discharge LIBs efficiently. The method causes significant corrosion on the battery and potentially releases toxic gases to the environment. Additionally, the voltage recovery effect is often not considered, where the battery voltage increases after discharge.
The discharge behaviour and the recovery effect are studied in this thesis through numerous experiments. A novel approach of using an iron-based redox couple electrolyte is introduced. The batteries were submerged in a solution and their voltage was measured hourly both during discharge and after it. From the experimental data, the effects of electrolyte concentration, discharge time and battery type are investigated.
The results show that in general, the redox couple electrolyte discharges the batteries to lower voltages compared to previous experiments using single salts found in literature. The discharge rate was found to increase with electrolyte concentration, while discharge time reduced the voltage recovery effect. However, the battery type has a significant impact on the discharge behaviour and safe voltages were not reached with all batteries. Additionally, some amount of variance was found between individual batteries of the same type. Some batteries experienced corrosion, also depending on the battery used. Therefore, the method doesn’t seem to be universally applicable to all different kinds of batteries.Litiumioniakkujen kysyntä kasvaa nopeasti maailmanlaajuisesti, erityisesti ajoneuvojen sähköistymisen ansiosta. Tämä johtaa myös kasvavaan käytettyjen litiumioniakkujen määrään tulevaisuudessa. Litiumioniakut sisältävät sekä ympäristölle haitallisia aineita että arvokkaita metalleja, joten niille tarvitaan tehokkaita kierrätysmenetelmiä. Suuri haaste käytettyjen litiumioniakkujen kierrätyksessä on niiden sisältämä ylijäämäenergia, joka voi aiheuttaa tulipaloja tai räjähdyksiä kierrätysprosessin aikana. Sähkökemiallinen purku suolaliuosten avulla on väitetysti tehokas menetelmä litiumioniakkujen täydelliseen purkamiseen. Tämä menetelmä kuitenkin aiheuttaa merkittävästi korroosiota akkuun ja voi mahdollisesti aiheuttaa haitallisia päästöjä ympäristöön. Lisäksi jännitteen palautumista ei ole huomioitu, missä litiumioniakun jännite kasvaa sähkökemiallisen purkamisen jälkeen.
Tässä diplomityössä litiumioniakkujen käyttäytymistä purun aikana ja jännitteen palautumista tutkitaan useiden kokeiden avulla. Uusi lähestymistapa käyttää redox-parielektrolyyttiä esitellään. Akut upotettiin suolaliuokseen ja niiden jännite mitattiin tunneittain sekä purun aikana että sen jälkeen. Elektrolyytin konsentraation, purkuajan ja akkutyypin vaikutuksia analysoidaan kokeellisesta datasta.
Tulokset osoittavat, että yleisesti ottaen redox-parielektrolyytit purkavat akkuja alhaisempaan jännitteeseen verrattuna aiempiin kokeisiin kirjallisuudessa yksittäisillä suoloilla. Purku nopeutuu elektrolyytin konsentraation kasvaessa, kun taas jännite palautuu vähemmän pidemmillä purkuajoilla. Akkutyypillä on kuitenkin merkittävin vaikutus purkukäyttäytymiseen ja turvallisen jännitteen rajoihin ei päästy kaikilla akuilla. Lisäksi saman akkutyypin yksittäisten akkujen välillä on pieniä eroavaisuuksia. Jotkin akut korrondoituivat purun aikana, riippuen akkutyypistä. Tätä menetelmää ei voi siis täysin soveltaa kaikille erilaisille akuille
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
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
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