| 1. |
- Agostini, Marco, 1987, et al.
(författare)
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Free-Standing 3D-Sponged Nanofiber Electrodes for Ultrahigh-Rate Energy-Storage Devices
- 2018
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 10:40, s. 34140-34146
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Tidskriftsartikel (refereegranskat)abstract
- We have designed a self-standing anode built-up from highly conductive 3D-sponged nanofibers, that is, with no current collectors, binders, or additional conductive agents. The small diameter of the fibers combined with an internal spongelike porosity results in short distances for lithium-ion diffusion and 3D pathways that facilitate the electronic conduction. Moreover, functional groups at the fiber surfaces lead to the formation of a stable solid-electrolyte interphase. We demonstrate that this anode enables the operation of Li-cells at specific currents as high as 20 A g-1 (approx. 50C) with excellent cycling stability and an energy density which is >50% higher than what is obtained with a commercial graphite anode.
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| 2. |
- Agostini, Marco, 1987, et al.
(författare)
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Minimizing the Electrolyte Volume in Li–S Batteries: A Step Forward to High Gravimetric Energy Density
- 2018
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 8:26
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Tidskriftsartikel (refereegranskat)abstract
- Sulfur electrodes confined in an inert carbon matrix show practical limitations and concerns related to low cathode density. As a result, these electrodes require a large amount of electrolyte, normally three times more than the volume used in commercial Li-ion batteries. Herein, a high-energy and high-performance lithium–sulfur battery concept, designed to achieve high practical capacity with minimum volume of electrolyte is proposed. It is based on deposition of polysulfide species on a self-standing and highly conductive carbon nanofiber network, thus eliminating the need for a binder and current collector, resulting in high active material loading. The fiber network has a functionalized surface with the presence of polar oxygen groups, with the aim to prevent polysulfide migration to the lithium anode during the electrochemical process, by the formation of S–O species. Owing to the high sulfur loading (6 mg cm−2) and a reduced free volume of the sulfide/fiber electrode, the Li–S cell is designed to work with as little as 10 µL cm−2of electrolyte. With this design the cell has a high energy density of 450 Wh kg−1, a lifetime of more than 400 cycles, and the possibility of low cost, by use of abundant and eco-friendly materials.
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| 3. |
- Agostini, Marco, 1987, et al.
(författare)
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Rational Design of Low Cost and High Energy Lithium Batteries through Tailored Fluorine-free Electrolyte and Nanostructured S/C Composite
- 2018
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 11:17, s. 2981-2986
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Tidskriftsartikel (refereegranskat)abstract
- We report a new Li–S cell concept based on an optimized F-free catholyte solution and a high loading nanostructured C/S composite cathode. The Li2S8present in the electrolyte ensures both buffering against active material dissolution and Li+conduction. The high S loading is obtained by confining elemental S (≈80 %) in the pores of a highly ordered mesopores carbon (CMK3). With this concept we demonstrate stabilization of a high energy density and excellent cycling performance over 500 cycles. This Li–S cell has a specific capacity that reaches over 1000 mA h g−1, with an overall S loading of 3.6 mg cm−2and low electrolyte volume (i.e., 10 μL cm−2), resulting in a practical energy density of 365 Wh kg−1. The Li–S system proposed thus meets the requirements for large scale energy storage systems and is expected to be environmentally friendly and have lower cost compared with the commercial Li-ion battery thanks to the removal of both Co and F from the overall formulation.
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| 4. |
- Haridas, Anupriya K., et al.
(författare)
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An Electrospun Core–Shell Nanofiber Web as a High-Performance Cathode for Iron Disulfide-Based Rechargeable Lithium Batteries
- 2018
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 11:20, s. 3625-3630
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Tidskriftsartikel (refereegranskat)abstract
- FeS2/C core–shell nanofiber webs were synthesized for the first time by a unique synthesis strategy that couples electrospinning and carbon coating of the nanofibers with sucrose. The design of the one-dimensional core–shell morphology was found to be greatly beneficial for accommodating the volume changes encountered during cycling, to induce shorter lithium ion diffusion pathways in the electrode, and to prevent sulfur dissolution during cycling. A high discharge capacity of 545 mAh g−1 was retained after 500 cycles at 1 C, exhibiting excellent stable cycling performance with 98.8 % capacity retention at the last cycle. High specific capacities of 854 mAh g−1, 518 mAh g−1, and 208 mAh g−1 were obtained at 0.1 C, 1 C, and 10 C rates, respectively, demonstrating the exceptional rate capability of this nanofiber web cathode.
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| 5. |
- Lim, Du Hyun, 1983, et al.
(författare)
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An Electrospun Nanofiber Membrane as Gel-Based Electrolyte for Room-Temperature Sodium–Sulfur Batteries
- 2018
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Ingår i: Energy Technology. - : Wiley. - 2194-4296 .- 2194-4288. ; 6:7, s. 1214-1219
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis and characterization of an electrospun gel polymer electrolyte (GPE) membrane based on polyacrylonitrile nanofibers (PAN) swollen in a polyethylene glycol dimethyl ether/Na-salt electrolyte solution, for application in room temperature sodium–sulfur (Na–S) batteries. The membranes show a high ionic conductivity, wide electrochemical stability window, and good thermal stability. We demonstrate the performance of the membrane in an Na–S cell using a sulfur–carbon nanotubes composite cathode and Na metal as anode. Our results show that the GPE membrane stabilizes the Na metal anode resulting in stable cycling behavior. The capacity of the Na–S cell, using the GPE membrane and operating at room temperature, is approximately 500 mAh g−1over 40 cycles. The selected electrolyte configuration also provides improved safety by replacing the highly reactive sodium perchlorate (NaClO4) salt previously used in literature. All these benefits make the gel-polymer electrolyte membrane a very promising system for application in room-temperature sodium and sodium–sulfur batteries.
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| 6. |
- Lim, Du Hyun, 1983, et al.
(författare)
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Tailor-Made Electrospun Multilayer Composite Polymer Electrolytes for High-Performance Lithium Polymer Batteries
- 2018
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Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880. ; 18:9, s. 6499-6505
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Tidskriftsartikel (refereegranskat)abstract
- A novel tailor-made multilayer composite polymer electrolyte, consisting of two outer layers of electrospun polyacrylonitrile (PAN) and one inner layer of poly(vinyl acetate) (PVAc)/poly(methyl methacrylate) (PMMA)/poly(ethylene oxide) (PEO) fibrous membrane, was prepared using continuous electrospinning. These membranes, which are made up of fibers with diameters in the nanometer range, were stacked in layers to produce interconnected pores that result in a high porosity. Gel polymer electrolytes (GPEs) were prepared by entrapping a liquid electrolyte (1 M LiPF6 in ethylene carbonate/dimethyl carbonate) in the membranes. The composite membranes exhibited a high electrolyte uptake of 450-510%, coupled with an improved room temperature ionic conductivity of up to 4.72 mS cm(-1) and a high electrochemical stability of 4.6 V versus Li/Li+. Electrochemical investigations of a composite membrane of PAN-PVAc-PAN, with a LiFePO4 cathode synthesized in-house, showed a high initial discharge capacity of 145 mAh g(-1), which corresponds to 85% utilization of the active material, and displayed stable cycle performance.
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| 7. |
- Mauri, Massimiliano, 1987, et al.
(författare)
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Byproduct-free curing of a highly insulating polyethylene copolymer blend: An alternative to peroxide crosslinking
- 2018
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7534 .- 2050-7526. ; 6:42, s. 11292-11302
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Tidskriftsartikel (refereegranskat)abstract
- High-voltage direct-current (HVDC) cables are a critical component of tomorrow's power grids that seamlessly integrate renewable sources of energy. The most advanced power cable technology uses crosslinked polyethylene (XLPE) insulation, which is produced by peroxide crosslinking of low-density polyethylene (LDPE). Peroxide crosslinking gives rise to hazardous byproducts that compromise the initially excellent purity and cleanliness of LDPE, and hence increase the electrical conductivity of the insulation material. Therefore, a byproduct-free curing process, which maintains the processing advantages and high electrical resistivity of LDPE, is in high demand. Here, we demonstrate a viable alternative to peroxide crosslinking that fulfils these requirements. Click chemistry reactions between two polyethylene copolymers allow the design of a curing process that is additive-free and does not result in the release of any byproducts. The thermoplastic copolymer blend offers a broad processing window up to 140 °C, where compounding and shaping can be carried out without curing. At more elevated temperatures, epoxy and acrylic acid functional groups rapidly react without byproduct formation to form an infusible network. Strikingly, the crosslinked copolymer blend exhibits a very low direct-current (DC) electrical conductivity of 2 × 10-16 S cm-1 at a typical cable operating temperature of 70 °C, which is on par with values measured for both ultra-clean LDPE and commercial XLPE. Hence, the use of polyethylene copolymer blends opens up the possibility to replace peroxide crosslinking with click chemistry type reactions, which may considerably expand the versatility of the most common type of plastic used today.
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| 8. |
- Senf, Deborah, et al.
(författare)
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Tailormade Polysaccharides with Defined Branching Patterns: Enzymatic Polymerization of Arabinoxylan Oligosaccharides
- 2018
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 57:37, s. 11987-11992
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Tidskriftsartikel (refereegranskat)abstract
- The heterogeneous nature of non-cellulosic polysaccharides, such as arabinoxylan, makes it difficult to correlate molecular structure with macroscopic properties. To study the impact of specific structural features of the polysaccharides on crystallinity or affinity to other cell wall components, collections of polysaccharides with defined repeating units are required. Herein, a chemoenzymatic approach to artificial arabinoxylan polysaccharides with systematically altered branching patterns is described. The polysaccharides were obtained by glycosynthase-catalyzed polymerization of glycosyl fluorides derived from arabinoxylan oligosaccharides. X-ray diffraction and adsorption experiments on cellulosic surfaces revealed that the physicochemical properties of the synthetic polysaccharides strongly depend on the specific nature of their substitution patterns. The artificial polysaccharides allow structure–property relationship studies that are not accessible by other means.
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| 9. |
- Verwohlt, Jan, et al.
(författare)
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Low Dose X-Ray Speckle Visibility Spectroscopy Reveals Nanoscale Dynamics in Radiation Sensitive Ionic Liquids
- 2018
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 120:16
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Tidskriftsartikel (refereegranskat)abstract
- X-ray radiation damage provides a serious bottleneck for investigating microsecond to second dynamics on nanometer length scales employing x-ray photon correlation spectroscopy. This limitation hinders the investigation of real time dynamics in most soft matter and biological materials which can tolerate only x-ray doses of kGy and below. Here, we show that this bottleneck can be overcome by low dose x-ray speckle visibility spectroscopy. Employing x-ray doses of 22-438 kGy and analyzing the sparse speckle pattern of count rates as low as 6.7×10-3 per pixel, we follow the slow nanoscale dynamics of an ionic liquid (IL) at the glass transition. At the prepeak of nanoscale order in the IL, we observe complex dynamics upon approaching the glass transition temperature TG with a freezing in of the alpha relaxation and a multitude of millisecond local relaxations existing well below TG. We identify this fast relaxation as being responsible for the increasing development of nanoscale order observed in ILs at temperatures below TG.
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