Carbon-Based Fibrous EDLC Capacitors and Supercapacitors

This paper investigates electrochemical double-layer capacitors (EDLCs) including two alternative types of carbon-based fibrous electrodes, a carbon fibre woven fabric (CWF) and a multiwall carbon nanotube (CNT) electrode, as well as hybrid CWF-CNT electrodes. Two types of separator membranes were also considered. An organic gel electrolyte PEO-LiCIO4-EC-THF was used to maintain a high working voltage. The capacitor cells were tested in cyclic voltammetry, charge-discharge, and impedance tests. The best separator was a glass fibre-fine pore filter. The carbon woven fabric electrode and the corresponding supercapacitor exhibited superior performance per unit area, whereas the multiwall carbon nanotube electrode and corresponding supercapacitor demonstrated excellent specific properties. The hybrid CWF-CNT electrodes did not show a combined improved performance due to the lack of carbon nanotube penetration into the carbon fibre fabric

Design of Porous Carbons for Supercapacitor Applications for Different Organic Solvent-Electrolytes

The challenge of optimizing the pore size distribution of porous electrodes for different electrolytes is encountered in supercapacitors, lithium-ion capacitors and hybridized battery-supercapacitor devices. A volume-averaged continuum model of ion transport, taking into account the pore size distribution, is employed for the design of porous electrodes for electrochemical double-layer capacitors (EDLCs) in this study. After validation against experimental data, computer simulations investigate two types of porous electrodes, an activated carbon coating and an activated carbon fabric, and three electrolytes: 1.5 M TEABF4 in acetonitrile (AN), 1.5 M TEABF4 in propylene carbonate (PC), and 1 M LiPF6 in ethylene carbonate:ethyl methyl carbonate (EC:EMC) 1:1 v/v. The design exercise concluded that it is important that the porous electrode has a large specific area in terms of micropores larger than the largest desolvated ion, to achieve high specific capacity, and a good proportion of mesopores larger than the largest solvated ion to ensure fast ion transport and accessibility of the micropores.</jats:p

Designing a Graphene Coating-Based Supercapacitor with Lithium Ion Electrolyte: An Experimental and Computational Study via Multiscale Modeling

Graphene electrodes are investigated for electrochemical double layer capacitors (EDLCs) with lithium ion electrolyte, the focus being the effect of the pore size distribution (PSD) of electrode with respect to the solvated and desolvated electrolyte ions. Two graphene electrode coatings are examined: a low specific surface area (SSA) xGNP-750 coating and a high SSA coating based on a-MWGO (activated microwave expanded graphene oxide). The study comprises an experimental and a computer modeling part. The experimental part includes fabrication, material characterization and electrochemical testing of an EDLC with xGNP-750 coating electrodes and electrolyte 1M LiPF6 in EC:DMC. The computational part includes simulations of the galvanostatic charge-discharge of each EDLC type, based on a continuum ion transport model taking into account the PSD of electrodes, as well as molecular modeling to determine the parameters of the solvated and desolvated electrolyte ions and their adsorption energies with each type of electrode pore surface material. Predictions, in agreement with the experimental data, yield a specific electrode capacitance of 110 F g−1 for xGNP-750 coating electrodes in electrolyte 1M LiPF6 in EC:DMC, which is three times higher than that of the high SSA a-MWGO coating electrodes in the same lithium ion electrolyte.</jats:p

Supercapacitors with lithium-ion electrolyte: An experimental study and design of the activated carbon electrodes via modelling and simulations

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2021 roadmap on lithium sulfur batteries

Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK's independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space

Fabrication and characterisation of biomimetic, electrospun gelatin fibre scaffolds for tunica media-equivalent, tissue engineered vascular grafts

It is increasingly recognised that biomimetic, natural polymers mimicking the extracellular matrix (ECM) have low thrombogenicity and functional motifs that regulate cell–matrix interactions, with these factors being critical for tissue engineered vascular grafts especially grafts of small diameter. Gelatin constitutes a low cost substitute of soluble collagen but gelatin scaffolds so far have shown generally low strength and suture retention strength. In this study, we have devised the fabrication of novel, electrospun, multilayer, gelatin fibre scaffolds, with controlled fibre layer orientation, and optimised gelatin crosslinking to achieve not only compliance equivalent to that of coronary artery but also for the first time strength of the wet tubular acellular scaffold (swollen with absorbed water) same as that of the tunica media of coronary artery in both circumferential and axial directions. Most importantly, for the first time for natural scaffolds and in particular gelatin, high suture retention strength was achieved in the range of 1.8–1.94 N for wet acellular scaffolds, same or better than that for fresh saphenous vein. The study presents the investigations to relate the electrospinning process parameters to the microstructural parameters of the scaffold, which are further related to the mechanical performance data of wet, crosslinked, electrospun scaffolds in both circumferential and axial tubular directions. The scaffolds exhibited excellent performance in human smooth muscle cell (SMC) proliferation, with SMCs seeded on the top surface adhering, elongating and aligning along the local fibres, migrating through the scaffold thickness and populating a transverse distance of 186 μm and 240 μm 9 days post-seeding for scaffolds of initial dry porosity of 74 and 83%, respectively

Change-of-state Paradigms and the middle in Kinyarwanda

This paper investigates the derivational relationships among members of verbal paradigms in Kinyarwanda (Bantu JD.61; Rwanda) by pursuing two interrelated goals. First, I describe a variety of derivational strategies for marking transitive and intransitive variants in change-of-state verb paradigms. Second, I focus on the detransitivizing morpheme –ik which serves as one possible marking for intransitive members of these paradigms. Ultimately, I argue that this morpheme is a marker of middle voice, and the variety of readings which appear with this form can be subsumed under a single operation of argument suppression. Finally, I provide a discussion of reflexives and the apparent lack of a reflexive reading with –ik by arguing that this reading is blocked by either lexical reflexives or the reflexive prefix i–

2021 roadmap on lithium sulfur batteries

Abstract: Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK’s independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space