1,720,959 research outputs found
Developing Electrolyte Solutions for Sodium-Ion Batteries : Challenging the Use of Hexafluorophosphate
No full textThe ability to store energy will be critical for achieving a functioning electrified society largely based on renewable energy sources. Batteries are anticipated to be a vital part of the infrastructure required to facilitate this energy storage. Electrolyte solutions are an essential component of most batteries, including sodium-ion batteries, which are emerging as a potentially more sustainable alternative to lithium-ion batteries. This thesis critically assesses the use of sodium hexafluorophosphate as an electrolyte in sodium-ion batteries. Although widely used in lithium-ion batteries, the suitability of hexafluorophosphate for sodium-ion batteries needs re-evaluation. In this thesis, properties meriting the use of sodium hexafluorophosphate are explored, including its solubility in different organic solvents, conductivity, ability to prevent anodic aluminium dissolution, and cycling performance in battery cells. Sodium bis(oxalato)borate is investigated as an example of a fluorine-free alternative that may better align with the goal of increasing the sustainability of contemporary batteries. The main drawback of sodium bis(oxalato)borate is its significantly lower solubility compared to sodium hexafluorophosphate. However, at the same concentration in a given solvent, both electrolytes exhibit similar conductivities, challenging the notion that hexafluorophosphate enhances conductivity through low ion association. Both electrolytes also prevent anodic aluminium dissolution. However, the use of sodium hexafluorophosphate does not consistently ensure adequate passivation of the negative electrode, suggesting that solvents or additives are more central for this process in these systems. In contrast, sodium bis(oxalato)borate appear to significantly contribute to the passivation of the negative electrode, even when used as an additive. As a sole electrolyte, sodium bis(oxalato)borate enable promising cycling performance in both lab-scale cells and in cells close to commercial standards. This research indicates that sodium hexafluorophosphate can be replaced with a fluorine-free electrolyte without compromising battery performance. The findings highlight the potential for more sustainable sodium-ion batteries and represent a step towards reducing the environmental impact of an electrified society
Developing Electrolyte Solutions for Sodium-Ion Batteries : Challenging the Use of Hexafluorophosphate
No full textThe ability to store energy will be critical for achieving a functioning electrified society largely based on renewable energy sources. Batteries are anticipated to be a vital part of the infrastructure required to facilitate this energy storage. Electrolyte solutions are an essential component of most batteries, including sodium-ion batteries, which are emerging as a potentially more sustainable alternative to lithium-ion batteries. This thesis critically assesses the use of sodium hexafluorophosphate as an electrolyte in sodium-ion batteries. Although widely used in lithium-ion batteries, the suitability of hexafluorophosphate for sodium-ion batteries needs re-evaluation. In this thesis, properties meriting the use of sodium hexafluorophosphate are explored, including its solubility in different organic solvents, conductivity, ability to prevent anodic aluminium dissolution, and cycling performance in battery cells. Sodium bis(oxalato)borate is investigated as an example of a fluorine-free alternative that may better align with the goal of increasing the sustainability of contemporary batteries. The main drawback of sodium bis(oxalato)borate is its significantly lower solubility compared to sodium hexafluorophosphate. However, at the same concentration in a given solvent, both electrolytes exhibit similar conductivities, challenging the notion that hexafluorophosphate enhances conductivity through low ion association. Both electrolytes also prevent anodic aluminium dissolution. However, the use of sodium hexafluorophosphate does not consistently ensure adequate passivation of the negative electrode, suggesting that solvents or additives are more central for this process in these systems. In contrast, sodium bis(oxalato)borate appear to significantly contribute to the passivation of the negative electrode, even when used as an additive. As a sole electrolyte, sodium bis(oxalato)borate enable promising cycling performance in both lab-scale cells and in cells close to commercial standards. This research indicates that sodium hexafluorophosphate can be replaced with a fluorine-free electrolyte without compromising battery performance. The findings highlight the potential for more sustainable sodium-ion batteries and represent a step towards reducing the environmental impact of an electrified society
Influence of Battery Electrode Chemistry on Electrolyte Decomposition
No full textIn rechargeable batteries a stable electrode-electrolyte interface is the key for achieving high coulombic efficiency, rate capability, and cycle lifetime. Numerous studies are published on how the electrolyte influences the interface and whether it leads to the formation of a stable solid-electrolyte-interphase (SEI) on the anode surface. However, the influence of the electrode material upon formation of the SEI has so far not been a focus. In this study, the influence of battery electrode chemistry on electrolyte decomposition is highlighted by investigating three different electrode materials in model battery systems: carbonaceous (glassy carbon), semi-conducting (silicon), and metallic (copper). Electrochemical methods including linear sweep voltammetry and chronoamperometry in combination with hard X-ray photoelectron spectroscopy are used to unravel how and in which order SEI components nucleate depending on surface material and potential. The impact of the alkali metal cation (lithium vs sodium) upon SEI formation is additionally investigated. The findings reveal that SEI formation is highly dependent on the electrode material, reduction potential, and choice of alkali cation, emphasizing its non-universal nature. These insights highlight the need for a thorough understanding of SEI formation mechanisms when designing advanced electrode materials and electrolytes for next-generation batteries
Influence of Battery Electrode Chemistry on Electrolyte Decomposition
No full textIn rechargeable batteries a stable electrode-electrolyte interface is the key for achieving high coulombic efficiency, rate capability, and cycle lifetime. Numerous studies are published on how the electrolyte influences the interface and whether it leads to the formation of a stable solid-electrolyte-interphase (SEI) on the anode surface. However, the influence of the electrode material upon formation of the SEI has so far not been a focus. In this study, the influence of battery electrode chemistry on electrolyte decomposition is highlighted by investigating three different electrode materials in model battery systems: carbonaceous (glassy carbon), semi-conducting (silicon), and metallic (copper). Electrochemical methods including linear sweep voltammetry and chronoamperometry in combination with hard X-ray photoelectron spectroscopy are used to unravel how and in which order SEI components nucleate depending on surface material and potential. The impact of the alkali metal cation (lithium vs sodium) upon SEI formation is additionally investigated. The findings reveal that SEI formation is highly dependent on the electrode material, reduction potential, and choice of alkali cation, emphasizing its non-universal nature. These insights highlight the need for a thorough understanding of SEI formation mechanisms when designing advanced electrode materials and electrolytes for next-generation batteries
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
On the compatibility of high mass loading bismuth anodes for full-cell sodium-ion batteries
No full textMetallic bismuth is here studied as an anode material for sodium-ion batteries. The details of electrochemical redox reactions, rate performance and cycled life were investigated using relatively high mass loading electrodes in two- and three-electrode full-cells. It demonstrated that the rate capability of bismuth anodes with high mass loading are not as good as indicated in previous literatures where low mass loading electrodes were used. It also indicated that the resistances causing a faltering rate performance may be connected to a loss in particle contact during desodiation. Efforts were also made to study the different electrochemical processes that occur during early cycles. Less advantageous characteristics of bismuth electrodes are also discussed. For example, several different electrolyte solutions were tested for compatibility with the bismuth system, where only glyme-based solutions seemed to facilitate robust cycling
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
Developing Electrolyte Solutions for Sodium-Ion Batteries [Elektronisk resurs] : Challenging the Use of Hexafluorophosphate
No full textThe ability to store energy will be critical for achieving a functioning electrified society largely based on renewable energy sources. Batteries are anticipated to be a vital part of the infrastructure required to facilitate this energy storage. Electrolyte solutions are an essential component of most batteries, including sodium-ion batteries, which are emerging as a potentially more sustainable alternative to lithium-ion batteries.This thesis critically assesses the use of sodium hexafluorophosphate as an electrolyte in sodium-ion batteries. Although widely used in lithium-ion batteries, the suitability of hexafluorophosphate for sodium-ion batteries needs re-evaluation. In this thesis, properties meriting the use of sodium hexafluorophosphate are explored, including its solubility in different organic solvents, conductivity, ability to prevent anodic aluminium dissolution, and cycling performance in battery cells. Sodium bis(oxalato)borate is investigated as an example of a fluorine-free alternative that may better align with the goal of increasing the sustainability of contemporary batteries. The main drawback of sodium bis(oxalato)borate is its significantly lower solubility compared to sodium hexafluorophosphate. However, at the same concentration in a given solvent, both electrolytes exhibit similar conductivities, challenging the notion that hexafluorophosphate enhances conductivity through low ion association.Both electrolytes also prevent anodic aluminium dissolution. However, the use of sodium hexafluorophosphate does not consistently ensure adequate passivation of the negative electrode, suggesting that solvents or additives are more central for this process in these systems. In contrast, sodium bis(oxalato)borate appear to significantly contribute to the passivation of the negative electrode, even when used as an additive. As a sole electrolyte, sodium bis(oxalato)borate enable promising cycling performance in both lab-scale cells and in cells close to commercial standards. This research indicates that sodium hexafluorophosphate can be replaced with a fluorine-free electrolyte without compromising battery performance. The findings highlight the potential for more sustainable sodium-ion batteries and represent a step towards reducing the environmental impact of an electrified society.</p
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
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