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Träfflista för sökning "WFRF:(Lindahl Niklas 1981) "

Sökning: WFRF:(Lindahl Niklas 1981)

  • Resultat 1-10 av 16
  • [1]2Nästa
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1.
  • Fu, Yifeng, 1984, et al. (författare)
  • Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
  • 2012
  • Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
  • Tidskriftsartikel (refereegranskat)abstract
    • A template-assisted method that enables the growth of covalently bonded three-dimensional carbon nanotubes (CNTs) originating from graphene at a large scale is demonstrated. Atomic force microscopy-based mechanical tests show that the covalently bonded CNT structure can effectively distribute external loading throughout the network to improve the mechanical strength of the material.
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2.
  • Svensson, J., et al. (författare)
  • Carbon Nanotube Field Effect Transistors with Suspended Graphene Gates
  • 2011
  • Ingår i: Nano Letters. - : The American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:9, s. 3569-3575
  • Tidskriftsartikel (refereegranskat)abstract
    • Novel field effect transistors with suspended graphene gates are demonstrated. By incorporating mechanical motion of the gate electrode, it is possible to improve the switching characteristics compared to a static gate, as shown by a combination of experimental measurements and numerical simulations. The mechanical motion of the graphene gate is confirmed by using atomic force microscopy to directly measure the electrostatic deflection. The device geometry investigated here can also provide a sensitive measurement technique for detecting high-frequency motion of suspended membranes as required, e.g., for mass sensing.
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3.
  • Agostini, Marco, 1987, et al. (författare)
  • Free-Standing 3D-Sponged Nanofiber Electrodes for Ultrahigh-Rate Energy-Storage Devices
  • 2018
  • Ingår i: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 10:40, s. 34140-34146
  • 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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4.
  • Bitenc, Jan, et al. (författare)
  • Concept and electrochemical mechanism of an Al metal anode - organic cathode battery
  • 2020
  • Ingår i: Energy Storage Materials. - 2405-8297. ; 24, s. 379-383
  • Tidskriftsartikel (refereegranskat)abstract
    • Aluminum (Al) batteries are fundamentally a promising future post-Li battery technology. The recently demonstrated concept of an Al-graphite battery represents some significant progress for the technology, but the cell energy density is still very modest and limited by the quantity of the AlCl3 based electrolyte, as it relies on AlCl4- intercalation. For further progress, cathode materials capable of an electrochemical reaction with Al positively charged species are needed. Here such a concept of an Al metal anode - organic cathode battery based on anthraquinone (AQ) electrochemistry with a discharge voltage of 1.1 V is demonstrated. Further improvement of both the cell capacity retention and rate capability is achieved by nano-structured and polymerized cathodes. The intricate electrochemical mechanism is proven to be that the anthraquinone groups undergo reduction of their carbonyl bonds during discharge and become coordinated by AlCl2+ species. Altogether the Al metal anode - AQ cathode cell has almost the double energy density of the state-of-the-art Al-graphite battery.
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5.
  • Brown, Rosemary, 1990, et al. (författare)
  • Surface Composition of a Highly Active Pt3Y Alloy Catalyst for Application in Low Temperature Fuel Cells
  • 2020
  • Ingår i: Fuel Cells. - 1615-6846 .- 1615-6854. ; 20:4, s. 413-419
  • Tidskriftsartikel (refereegranskat)abstract
    • Currently, platinum is the most widely used catalyst for low temperature proton exchange membrane fuel cells (PEMFC). However, the kinetics at the cathode are slow, and the price of platinum is high. To improve oxygen reduction reaction (ORR) kinetics at the cathode, platinum can be alloyed with rare earth elements, such as yttrium. We report that Pt3Y has the potential to be over 2 times more active for the ORR compared with Pt inside a real fuel cell. We present detailed photoemission analysis into the nature of the sputtered catalyst surface, using synchrotron radiation photoelectron spectroscopy (SRPES) to examine if surface adsorbates or impurities are present and can be removed. Pretreatment removes most of the yttrium oxide in the surface leaving behind a Pt overlayer which is only a few monolayers thick. Evidence of a substochiometric oxide peak in the Y 3d core level is presented, this oxide extends into the surface even after Ar+ sputter cleaning in-situ. This information will aid the development of new highly active nanocatalysts for employment in real fuel cell electrodes.
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6.
  • Brown, Rosemary, 1990, et al. (författare)
  • Unraveling the Surface Chemistry and Structure in Highly Active Sputtered Pt3Y Catalyst Films for the Oxygen Reduction Reaction
  • 2020
  • Ingår i: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 12:4, s. 4454-4462
  • Tidskriftsartikel (refereegranskat)abstract
    • Platinum is the most widely used and best performing sole element for catalyzing the oxygen reduction reaction (ORR) in low-temperature fuel cells. Although recyclable, there is a need to reduce the amount used in current fuel cells for their extensive uptake in society. Alloying platinum with rare-earth elements such as yttrium can provide an increase in activity of more than seven times, reducing the amount of platinum and the total amount of catalyst material required for the ORR. As yttrium is easily oxidized, exposure of the Pt-Y catalyst layer to air causes the formation of an oxide layer that can be removed during acid treatment, leaving behind a highly active pure platinum overlayer. This paper presents an investigation of the overlayer composition and quality of Pt3Y films sputtered from an alloy target. The Pt3Y catalyst surface is investigated using synchrotron radiation X-ray photoelectron spectroscopy before and after acid treatment. A new substoichiometric oxide component is identified. The oxide layer extends into the alloy surface, and although it is not completely removed with acid treatment, the catalyst still achieves the expected high ORR activity. Other surface-sensitive techniques show that the sputtered films are smooth and bulk X-ray diffraction reveals many defects and high microstrain. Nevertheless, sputtered Pt3Y exhibits a very high activity regardless of the film's oxide content and imperfections, highlighting Pt3Y as a promising catalyst. The obtained results will help to support its integration into fuel cell systems.
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7.
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8.
  • Jankowski, Piotr, 1990, et al. (författare)
  • Chemically soft solid electrolyte interphase forming additives for lithium-ion batteries
  • 2018
  • Ingår i: Journal of Materials Chemistry A. - 2050-7488 .- 2050-7496. ; 6:45, s. 22609-22618
  • Tidskriftsartikel (refereegranskat)abstract
    • The solid electrolyte interphase (SEI) layer is a key element of lithium-ion batteries (LIBs) enabling stable operation and significantly affecting the cycling performance including life-length. Here we present the concept of chemically soft SEI-forming additives, created by introducing aromatic ring based derivatives of already well-known SEI-formers to render them chemically soft, resulting in 1,3,2-benzodioxathiole 2,2-dioxide (DTDPh), 3H-1,2-benzoxathiole 2,2-dioxide (PSPh), and 1,4,2-benzodioxathiine 2,2-dioxide (PSOPh). A computational DFT based comparison predicts promise with respect to both early and controlled reduction processes. These predictions are verified by basic electrochemical studies targeting appropriate additive reduction potentials i.e. prior to any electrolyte solvent or salt decomposition. In addition, the decomposition paths of the SEI-formers are projected and the end products compared with spectroscopic data for the SEI-layers formed in LIB cells. The SEI-layers formed finally show very good properties in terms of improved capacity retention, improved coulombic efficiency, and reduced resistance for the graphite/electrolyte/LFP full cells made, especially observed for PSOPh. That is due to the preferred C-O bond breaking mechanism, observed also for DTDPh, and supported by the S-C bond breaking mechanism, together resulting in well conductive and good adhesion properties of the SEI-layers. This is expedited by higher softness, eventuating in a formation process stabilizing some of the radicals and/or lowering the kinetic barriers. These positive effects are confirmed both when applying a commercial style electrolyte and for a new generation electrolyte based on the LiTDI salt, where suppression of the TDI anion reduction is truly crucial.
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9.
  • Jankowski, Piotr, 1990, et al. (författare)
  • Impact of Sulfur-Containing Additives on Lithium-Ion Battery Performance: From Computational Predictions to Full-Cell Assessments
  • 2018
  • Ingår i: ACS Applied Energy Materials. - 2574-0962. ; 1, s. 2582-2591
  • Tidskriftsartikel (refereegranskat)abstract
    • Electrolyte additives are pivotal for stabilization of lithium-ion batteries, by suppressing capacity loss through creation of an engineered solid-electrolyte-interphase-layer (SEI-layer) at the negative electrode and thereby increasing lifetime. Here, we compare four different sulfur-containing 5-membered-ring molecules as SEI-formers: 1,3,2-dioxathiolane-2,2-dioxide (DTD), propane-1,3-sultone (PS), sulfopropionic acid anhydride (SPA), and prop-1-ene-1,3-sultone (PES). Density functional theory calculations and electrochemical measurements both confirm appropriate reduction potentials. For a connection of the protective properties of the SEIs formed to the chemical structure of the additives, the decomposition paths are computed and compared with spectroscopic data for the negative electrode surface. The performance of full-cells cycled using a commercial electrolyte and the different additives reveals the formation of organic dianions to play a crucial beneficial role, more so for DTD and SPA than for PS and PES.
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10.
  • Lindahl, Niklas, 1981, et al. (författare)
  • Aluminum Metal-Organic Batteries with Integrated 3D Thin Film Anodes
  • 2020
  • Ingår i: Advanced Functional Materials. - 1616-301X. ; 30:51
  • Tidskriftsartikel (refereegranskat)abstract
    • Aluminum 3D thin film anodes fully integrated with a separator are fabricated by sputtering and enable rechargeable aluminum metal batteries with high power performance. The 3D thin film anodes have an approximately four to eight times larger active surface area than a metal foil, which significantly both reduces the electrochemical overpotential, and improves materials utilization. In full cells with organic cathodes, that is, aluminum metal-organic batteries, the 3D thin film anodes provide 165 mAh g(-1)at 0.5 C rate, with a capacity retention of 81% at 20 C, and 86% after 500 cycles. Post-mortem analysis reveals structural degradation to limit the long-term stability at high rates. As the multivalent charge carrier active here is AlCl2+, the realistic maximal specific energy, and power densities at cell level are approximate to 100 Wh kg(-1)and approximate to 3100 W kg(-1), respectively, which is significantly higher than the state-of-the-art for Al batteries.
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