99 research outputs found
Inhomogeneity in Li(ion) Battery Electrodes: Causes and Effects
No full textThe environmental and climate change concerns are calling for rapid energy transition by the use of more green resources and zero emission solutions. This requires development of mature energy storage systems like rechargeable batteries. For instance, the Li-ion battery technology was first commercialized in 1985, but still is under research and development to increase energy density and cycle life beyond the state-of-the-art. The search for energy dense active-materials like high nickel content transition metal oxides, the use of solid electrolytes or the strive for enabling dendrite-free lithium metal anodes all aim to tackle the limitations of today’s technology. Another strategy is to ensure that the battery is manufactured authentically, devoid of defects and inhomogeneities. These inhomogeneities might exist at different length scales from nanoscale to macroscale or in other words from active-material level to cell pack level. The focus of this thesis is to investigate the causes and effects of inhomogeneities in the cells, especially at the electrode level, like poor carbon distribution or insufficient electrolyte wetting in the electrodes. Such flaws can interfere with electronic and ionic transport in the battery porous electrodes and possibly cause reduced performance, non-uniform degradation and accelerated aging.
The first chapter presents a brief review of Li-ion battery technology, porous electrode model, battery aging mechanisms and an introduction to inhomogeneities at different length scales. In the second chapter, we study LiNi0.6Mn0.2Co0.2O2 slurries prepared via different methods and characterize their viscoelastic behavior and dis/charge behavior of electrodes made thereof. We observed disparities among the dis/charge behavior, and ascribed it to the local variations in carbon-binder domain porosity and thickness. In chapter 3, we fabricated bilayer electrodes with a disparity among the two layers as inhomogeneity of porous electrodes. In our system, we had a carbon-deficient or carbon-rich layer near the electrode current collector. The results showed that the former can have a destructive effect on rate performance and aging while the latter appeared to have a constructive effect. Chapter 4 investigates possible aging mechanism in porous NMC electrodes in the presence of heterogeneity in the electrode structure. We observed frequent reductions in the charge transfer resistance of the electrodes during long term cycling of the electrodes which is correlated to the fracture of active-material particles. This hypothesis was further elaborated by cross-sectional imaging as well as observation of an unusual energy recovery which could be explained by intergranular fracture. Finally in chapter 5, we looked at the inhomogeneity in-plane of the battery electrodes. Large format lithium electrodes were made and tested in a home-made setup in symmetric configuration where both working and counter electrodes were lithium. The spatial distribution of degradation over the surface of large electrodes was correlated to non-uniform distribution of current density in-plane of the battery electrodes
Poly(ethylene disulfide)/graphene oxide nanocomposites: Dynamic-mechanical and electrochamical properties
No full textPoly(ethylene disulfide)/graphene oxide nanocomposites: Dynamic-mechanical and electrochemical properties
No full textIn this work, dynamic-mechanical and electrochemical properties of polyethylene disulfide and polyethylene disulfide/graphene oxide (GO) nanocomposites are investigated to explore their possible application in rechargeable batteries. The crude polyethylene disulfide, as well as GO and sodium dodecylbenzenesulfonate (SDBS) modified-GO loaded nanocomposites are synthesized through the in situ interfacial polymerization. The GO loaded nanocomposite presents a glass transition temperature of 4.5 °C and a high storage modulus of 115 MPa at 25 °C, which is 17% and 155% higher than that for the crude polyethylene disulfide and the SDBS-modified-GO loaded nanocomposite, respectively. Although the electrical conductivity of the 2 GO loaded nanocomposite is slightly higher than other two materials (due to the slightly higher electrical conductivity of GO nanosheets), the electrical conductivity of all polysulfide materials is very close and in the range of 10-6 and 10-4 S/m at low (10 Hz) and high frequencies (10 6 Hz), respectively. Notably, the polyethylene disulfide/GO nanocomposite presents a Coulombic efficiency of 97% in a lithium cell with a conventional liquid-electrolyte
Toward a synergistic optimization of porous electrode formulation and polysulfide regulation in lithium-sulfur batteries
No full textThe use of functional materials is a popular strategy to mitigate the polysulfide-induced accelerated aging of lithium-sulfur (Li-S) batteries. However, deep insights into the role of electrode design and formulation are less elaborated in the available literature. Such information is not easy to unearth from the existing reports on account of the scattered nature of the data and the big dissimilarities among the reported materials, preparation protocols, and cycling conditions. In this study, model functional materials known for their affinity toward polysulfide species, are integrated into the porous sulfur electrodes at different quantities and with various spatial distributions. The electrodes are assembled in 240 lithium-sulfur cells and thoroughly analyzed for their short- and long-term electrochemical performance. Advanced data processing and visualization techniques enable the unraveling of the impact of porous electrodes' formulation and design on self-discharge, sulfur utilization, and capacity loss. The results highlight and quantify the sensitivity of the cell performance to the synergistic interactions of catalyst loading and its spatial positioning with respect to the sulfur particles and carbon-binder domain. The findings of this work pave the road for a holistic optimization of the advanced sulfur electrodes for durable Li-S batteries.
This research seeks to offer key insights into optimizing advanced electrodes for lithium-sulfur batteries. The study emphasizes the critical role of optimal catalyst quantity and strategic placement near sulfur particles or the carbon-binder domain. These factors notably impact capacity retention and rate-capability, governing the local balance between the conversion and migration rates of polysulfides.imag
Theoretical and Experimental Insights into Dendrite Growth in Lithium-Metal Electrode
No full textA stable lithium-metal electrode can enable the shift from the Li-ion batteries to the next generation chemistries such as Li-S and Li-O2 with significant gains in the energy density and sustainability. This transition, however, is hindered by the dendrite formation, high chemical reactivity, and volume changes of the Li electrode. Although recent advancements in computational and experimental research have deepened our understanding of these issues, the primary obstacles to the commercialization of the lithium-metal batteries (LMBs) still persist. To address these challenges, a synergistic approach that combines computational and experimental strategies shows great promise. In this regard, this paper reviews the current experimental and theoretical understanding of the lithium-metal electrodes in view of the initiation and growth mechanisms of the lithium dendrites and interface instability. Leveraging the strengths of both approaches can offer a holistic insight into the LMB performance and guide the development of innovative designs for electrolytes and electrodes that can enhance the stability and performance of the LMBs
Synergistic interactions between the charge‐transport and mechanical properties of the ionic‐liquid‐based solid polymer electrolytes for solid‐state lithium batteries
No full textH2020 LEIT Advanced Materials, Grant/Award Number: 87555
Bio-nanocomposites and their potential applications in physiochemical properties of cheese: an updated review
No full textCheese is a perishable commodity due to the dynamic biochemical and microbiological changes that occur throughout its manufacture, ripening, and marketing. Consequently, the cheese sector relies heavily on packaging. Growing environmental concerns regarding non-biodegradable cheese manufacturing and packaging components have motivated research into bio-nanomaterials as an alternative. By controlling the O2 and CO2 exchange rates and functioning as a vehicle for antimicrobial compounds, bio-nanocomposite sheets might be employed to minimize cheese’s weight loss and microbial breakdown. Bio-nanocomposites are organic polymeric materials made of two major components, one of which serves as a biopolymer structure (continuous phase) and the other as a reinforced material (dispersed phase) with dimensions between 1 and 100 nm. These components share characteristics such as flexibility, biocompatibility, biodegradability, green composites, and affordability. Bio-nanocomposites employed as antibacterial agents in the food coatings industry may inhibit the growth of microorganisms on food substrates, hence increasing the shelf life of the product. The beneficial antibacterial activity of bio-nanocomposites shows that they have several applications in the food industry. In this article, we will discuss the advantages and features of bio-nanocomposite films or coatings put to cheese slices in order to increase storage duration and reduce the usage of non-biodegradable materials. This study discusses the most recent scientific findings pertaining to bio-packaging ingredients and cheese variants
ارزيابي مخاطرات بالقوه به روش تجزيهوتحليل حالات شکست و اثرات آنها در يک شرکت توليد تجهيزات تهويه مطبوع
No full text Background & Objective: Failure is inevitable in the daily activities and machinery in industrial operations, the causes of which should be properly evaluated and analyzed. Failure mode and effects analysis (FMEA) is a potent and effective method for identifying and eliminating potential failure, as well as the difficulties and failures in systems, design, processes, and services. The present study aimed to assess the potential risk in an air conditioning equipment manufacturing company using the FMEA.
Materials and Methods: In this descriptive cross-sectional study, all activities and machinery in different units of the air conditioning equipment manufacturing company were analyzed by census evaluation and FMEA risk assessment. Cutoff point was determined at 70%, and the risks were categorized into three levels of acceptable (L), medium (M), and unacceptable (H); based on the classification of the organization and control ability. Data analysis was performed in Microsoft Excel 2010.
Results: Among 1,453 identified risks, 237 risks (16.3%) were in the H category with the ratio of 1/6, 473 risks (32.6%) were in the L category with the ratio of 1/3 , and 743 risks (51.1%) were in the M category with the ratio of 1/2 . Moreover, 44 unacceptable risks (H) (3%) were in the Likert classification developed by the researcher in accordance with the organization, which were considered acceptable in the FMEA classification. These risks could be considered the margins of control measures.
Conclusion: According to the FMEA classification, the ratio of H risks to the total risks is 1/10 , while it was obtained at 1/6 in the present study. On the other hand, high number of the identified risks does not necessarily indicate the manufacturing units to be of high risk.
How to cite this article: Yari S.Assessment of Potential Risk by the Failure Mode and Effects Analysis in an Air Conditioning Equipment Manufacturing Company.Irtiqa Imini Pishgiri Masdumiyat (Safety Promotion and Injury Prevention). 2017; 5(2):89-96.سابقه و هدف:هر فعاليت و ماشيني در عمليات صنعتي بهطور روزانه تن به حالاتي از شکست ميدهد که ميبايست مورد تجزيهوتحليل قرار گيرد. حالت شکست و تجزيهوتحليل اثرات آن، روشي قدرتمند و مؤثر جهت شناسايي و حذف شکست بالقوه، مشکلات و خطاها از سيستم، طراحي، فرآيند و خدمات است. هدف از اين مطالعه نيز ارزيابي مخاطرات بالقوه ايمني و بهداشت به روش تجزيهوتحليل حالات شکست و اثرات آنها در يک شرکت توليد تجهيزات تهويه مطبوع ميباشد.
روش بررسي: در اين مطالعه توصيفي- مقطعي کليه فعاليتها و ماشينآلات واحدهاي مختلف يک شرکت توليدي تجهيزات تهويه مطبوع با استفاده از سرشماري و به روش ارزيابي ريسک حالات شکست و تجزيهوتحليل اثرات آنها مورد ارزيابي قرار گرفتند. Cut of point ريسکها 70% بود و همچنين ريسکها با توجه به گروهبندي سازمان بر اساس توانايي کنترل در سه سطح قابلقبول (L)، متوسط(M) و غيرقابلقبول(H) گروهبندي شدند و درنهايت دادهها به کمک نرمافزارMicrosoft Excel(2010) مورد تجزيهوتحليل قرار گرفتند.
يافتهها: از تعداد 1453 ريسک شناساييشده 237 ريسک (3/16%) با نسبت 6/1 در اولويت H، 473 ريسک (6/32%) با نسبت 3/1 در اولويت L و 743 ريسک (1/51%) با نسبت 2/1 در اولويت M قرار گرفتند. تعداد 44 ريسک غيرقابلقبول(H) (3%) در گروهبندي ليکرتي که توسط محقق با توجه به نظر سازمان تدوينشده است قرار دارد که در گروهبندي FMEA در گروه قابلقبول قرار دارند که ميتوان اين ريسکها را حاشيه اقدامات کنترلي قلمداد کرد.
نتيجهگيري: بر اساس گروهبندي FMEA نسبت ريسکهاي H بهکل ريسکها 10/1 ميباشد درصورتيکه اين نسبت در گروهبندي محقق 6/1 است. از طرفي تعداد زياد ريسکهاي شناساييشده در واحدها دليل بر پرخطر بودن آن واحد نميباشد.
واژگان کليدي:
How to cite this article:
Yari S.Assessment of Potential Risk by the Failure Mode and Effects Analysis in an Air Conditioning Equipment Manufacturing Company. J Saf Promot Inj Prev. 2017; 5(2):89-96 .
 
Pixelated flesh
No full textThe pixel and the technique of pixelating faces belong to a politics of fear and a digital aesthetics of truth which shapes public perceptions of criminality and the threat of otherness. This article will draw on Paul Virilio's account of the pixel in Lost Dimension in order to analyze its specific role and operation in relation to contemporary representations of incarceration. In particular, the article will consider the figure of the incarcerated informant. The incarcerated criminal or informant plays a complex role as both subversive other and purveyor of truth and as such constitutes an important example of the ways in which pixelation functions as a visible signifier of a dangerous truth whilst blurring, erasing and, ultimately, dehumanizing those "speaking" this truth. Our discussion forms part of a larger analysis of the production, framing and circulation of images of otherness, identifying Virilio as key to debates around the violence of the screen
Demystifying Charge Transport Limitations in the Porous Electrodes of Lithium‐Ion Batteries
No full textA possible strategy to give a simultaneous boost to the energy and power attributes of the current generation of lithium-ion batteries is developing thick porous electrodes with high loading of active material alongside optimal percolation networks for the ions and electrons. However much the insertion capacity and kinetics of the single particle lithium-insertion materials, the energy and power density of the cell might be significantly capped by the ionic and electronic transport limitations in the porous electrode. In this work, a physical picture grounded in experiment and theory is proposed to spotlight and quantify the pivotal role of the micro-scale porosity and active-material loading in determining the tortuosity, effective transport properties, and performance limitations of a porous electrode. The outcome is a phenomenological picture coupled with a theoretical framework for the deconvolution of the relative shares of the electronic and ionic transport limitations over short and long ranges in the performance limitation of lithium-ion batteries. The porous electrodes' microstructure is well recognized to have a pivotal role in determining the energy and power capabilities and the life time of lithium ion batteries (LIBs). [1-2] This is due to the fact that the effective transport properties, namely ionic and electronic conductivities together with the ion diffusivity are strong functions of the microstructural details such as porosity and tortuosity of the electrodes. [3-5] Notwithstanding the high interest to quantify the rate limiting phenomena in the LIBs, the reports on the detailed juxtaposition of the electronic and ionic percolation limitations to the performance of LIBs are very scarce. [4] Although the current literature provides invaluable information about the methods for measuring the effective ionic [3,6-9] and electronic [9-11] conductivity in the lithium ion battery electrodes, but there are very limited comprehensive reports on the interplay between the electrode recipe, transport limitations, and the battery performance. [12-15] A variety of experimental and theoretical techniques have been proposed for the (in)direct measurement of the effective conductivities in the porous electrodes of LIBs. Several studies have investigated the ionic and electronic conduction in LIBs by reconstructing the three dimensional (3D) structure of the porous electrodes based on the cross sectional images obtained via X-ray tomography [6,16-19] or focused ion beam-scanning electron microscopy (FIB-SEM).The authors are grateful for financial support to FWO-Vlaanderen (SBO XL-Lion, S005017N) and the Special Research Fund BOF of Hasselt University. H.H. and M.S. acknowledge Prof. Wouter Marchal for the PSD measurements and Jan Mertens for the technical support
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