| 1. |
- Ciosek Högström, Katarzyna, 1984-, et al.
(författare)
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Impact of the flame retardant additive triphenyl phosphate (TPP) on the performance of graphite/LiFePO4 cells in high power applications
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 256, s. 430-439
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Tidskriftsartikel (refereegranskat)abstract
- This study presents an extensive characterization of a standard Li-ion battery (LiB) electrolyte containing different concentrations of the flame retardant triphenyl phosphate (TPP) in the context of high power applications. Electrolyte characterization shows only a minor decrease in the electrolyte flammability for low TPP concentrations. The addition of TPP to the electrolyte leads to increased viscosity and decreased conductivity. The solvation of the lithium ion charge carriers seem to be directly affected by the TPP addition as evidenced by Raman spectroscopy and increased mass-transport resistivity. Graphite/LiFePO4 full cell tests show the energy efficiency to decrease with the addition of TPP. Specifically, diffusion resistivity is observed to be the main source of increased losses. Furthermore, TPP influences the interface chemistry on both the positive and the negative electrode. Higher concentrations of TPP lead to thicker interface layers on LiFePO4. Even though TPP is not electrochemically reduced on graphite, it does participate in SEI formation. TPP cannot be considered a suitable flame retardant for high power applications as there is only a minor impact of TPP on the flammability of the electrolyte for low concentrations of TPP, and a significant increase in polarization is observed for higher concentrations of TPP. (C) 2014 Elsevier B.V. All rights reserved.
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| 2. |
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| 3. |
- Ciosek, Katarzyna, et al.
(författare)
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Energy storage activities in the Swedish hybrid vehicle centre
- 2009
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Ingår i: World Electric Vehicle Journal. - : MDPI AG. - 2032-6653. ; 3:4, s. 858-862, s. 2850-2854
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Tidskriftsartikel (refereegranskat)abstract
- Significant efforts are put worldwide on developing new concepts for vehicle propulsion with the hybrid electric vehicle (HEV) being a prominent example. Hybrid technology is clearly a strategic future activity for automotive industries and in response to the rapid development in the area; the Swedish Hybrid Vehicle Centre (SHC) was formed in 2007 to join forces between Swedish industry and academia in the field. The centre emphasizes a holistic view to meet the environmental and societal needs with new technological solutions. The research within SHC is currently divided into three different themes whereof we here describe the Energy Storage theme with emphasis on the activities carried out at the involved universities in the current main project areas: Cell Properties, Electrode Materials and Electrolyte Additives. Examples are given on how these projects attacks the problems at hand separately, but also how we create synergy effects between the projects. As an example cell modelling is performed given a specific chemistry and cycling scheme, the same parameters are used for electrochemical experiments which provide macroscopic data that are connected with molecular level actions in the electrodes, the electrolyte, and the interfaces. All this is done using our base-line chemistry and a subsequent route is to investigate the role of different additives to overcome the limitations that are observed.
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| 4. |
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| 5. |
- Hellqvist Kjell, Maria, et al.
(författare)
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Electrochemical characterization of lithium intercalation processes of PAN-based carbon fibers in a microelectrode system
- 2013
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 160:9, s. A1473-A1481
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Tidskriftsartikel (refereegranskat)abstract
- A full electrochemical investigation of the lithium intercalation processes in a commercially available PAN-based carbon fiber, Toho Tenax IMS65 (unsized and sized) primarily intended to be used in structural lithium-ion batteries, has been performed. In order to extract the electrochemical properties, a specially designed microelectrode system consisting of a single fiber working electrode, lithium-foil counter electrode and well-characterized battery materials were utilized. The properties, for 5 to 100% state-of-charge (SOC), were mainly determined from electrochemical impedance spectroscopy (EIS) measurements by fitting of a physics-based model, and electronic conductivity examination. The study shows excellent mass transport and kinetic properties, especially at high SOCs for this specific carbon fiber compared to other negative electrode materials. Some electrochemical parameters vary depending on sizing, but are too small to affect the actual electrochemical performance. A strong SOC dependence is shown for most electrochemical properties, including the electronic conductivity.
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| 6. |
- Klett, Matilda, et al.
(författare)
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Altered electrode degradation with temperature in LiFePO4/mesocarbon microbead graphite cells diagnosed with impedance spectroscopy
- 2014
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 141, s. 173-181
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Electrode degradation in LiFePO4 / mesocarbon microbead graphite (MCMB) pouch cells aged at 55 °C by a synthetic hybrid drive cycle or storage is diagnosed and put into context with previous results of aging at 22 °C. The electrode degradation is evaluated by means of electrochemical impedance spectroscopy (EIS), measured separately on electrodes harvested from the cells, and by using a physics-based impedance model for aging evaluation. Additional capacity measurements, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) are used in the evaluation. At 55 °C the LiFePO4 electrode shows increased particle/electronic conductor resistance, for both stored and cycled electrodes. This differs from results obtained at 22 °C, where the electrode suffered lowered porosity, particle fracture, and loss of active material. For graphite, only cycling gave a sustained effect on electrode performance at 55 °C due to lowered porosity and changes of surface properties, and to greater extent than at low temperature. Furthermore, increased current collector resistance also contributes to a large part of the pouch cell impedance when aged at increased temperatures. The result shows that increased temperature promotes different degradation on the electrode level, and is an important implication for high temperature accelerated aging. In light of the electrode observations, the correlation between full-cell and electrode impedances is discussed.
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| 7. |
- Mellin, P., et al.
(författare)
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Moisture content analysis of metal powders, using oven desorption followed by Karl Fischer titration
- 2020
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Ingår i: Euro PM 2018 Congress and Exhibition. - 9781899072507
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Konferensbidrag (refereegranskat)abstract
- In this paper, we use Oven Desorption followed by Karl Fischer Titration (KF), to measure moisture content in a newly opened PBF-LB Hasteloy X powder (we found 28.8 ppm), an PBF-EB powder (13.7 ppm) and a HIP powder (6.7 ppm). This method heats a powder sample inside a hermetically closed vial, in an oven. At the same time an inert gas flow enters, flushes out the evaporated water and exits the vial, via a double hollow needle. The gas-water mixture that exits is directed to the Karl Fischer Titration, where the evaporated moisture is quantified. Included is also a comparison with thermogravimetric analysis (TGA) and a climate chamber moisturization experiment of a PBF-LB HX powder followed by KF analysis. After the moisturization and KF analysis, the same powder was characterized in terms of oxygen content.
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| 8. |
- Nyman, Andreas, et al.
(författare)
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A New Methodology for Evaluating the High-Power Behavior of a Li-ion Battery Cell
- 2010
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Ingår i: Rechargeable Lithium-Ion Batteries. - : Electrochemical Society. - 9781566778107 ; , s. 253-262
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Konferensbidrag (refereegranskat)abstract
- The internal sources of polarization are calculated and investigated for a graphite (MAG-10) vertical bar 1.2 M LiPF6 in EC: EMC (3: 7 by weight) vertical bar LiNi0.8Co0.15Al0.05O2 battery cell at SOC 40 and 80. A method is developed where the total polarization of the battery cell is split up into six polarizing subprocesses. The method involves two steps; the solving of an experimentally validated model that describes the dynamics of the battery cell during e. g. a hybrid pulse power characterization test and the use of the modeled cell's local potential, concentration profiles and local current density to calculate the internal losses. With this analysis the sources of polarization during an EUCAR test cycle are determined. The major factor limiting the performance is associated with the mass transport in the electrolyte.
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| 9. |
- Nyman, Andreas, et al.
(författare)
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Analysis of the Polarization in a Li-Ion Battery Cell by Numerical Simulations
- 2010
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:11, s. A1236-A1246
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Tidskriftsartikel (refereegranskat)abstract
- An experimentally validated model was developed to analyze the polarization of a LiNi0.8Co0.15Al0.05O2 vertical bar 1.2 M LiPF6 in ethylene carbonate (EC):ethyl methyl carbonate (EMC) (3:7)vertical bar MAG-10 battery cell during a hybrid pulse power characterization (HPPC) cycle. The analysis was made with a method where the polarization was split up into parts associated with activation of the electrochemical reactions, mass transport of species in the electrolyte and in the solid phase, and inadequate contact between the materials in the electrodes. Each contribution to the polarization was quantified as a snapshot in time and as an average over the HPPC cycle. The polarization during a cycle according to EUCAR was analyzed in detail for state of charge (SOC) 40 and 80. It arose mainly due to the mass transport in the electrolyte, e. g., at SOC 40 it contributed to 43% of the total polarization. In an ISO (International Organization for Standardization)-energy cycle where the current loads are higher and applied for longer times than the EUCAR cycle, the mass transport by diffusion in the electrolyte and in the solid phase of the negative electrode became more significant. The presented method offers the possibility to find a battery cell's optimal operational condition and design.
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| 10. |
- Saarimaa, Ville J., et al.
(författare)
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Assessment of pitting corrosion in bare and passivated (wet scCO2-induced patination and chemical passivation) hot-dip galvanized steel samples with SVET, FTIR, and SEM (EDS)
- 2020
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Ingår i: Materials and corrosion - Werkstoffe und Korrosion. - : Wiley-VCH Verlag. - 0947-5117 .- 1521-4176.
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the local electrochemical activity of untreated and passivated (natural or chemical passivation) zinc specimens was observed during immersion in a 0.1-M NaCl solution. The localized anodic activity during the exposure, measured with the scanning vibrating electrode technique, was linked to zinc dissolution by the pitting corrosion mechanism. It was correlated to specific corrosion products characterized by Fourier transmission infrared (FTIR) microscopy. FTIR molecule maps were produced from individual pitting corrosion sites (100–200 µm in width). With argon ion beam milling and latest energy-dispersive X-ray spectroscopy (EDS) technology, element maps with a high spatial resolution (≪100 nm) were recorded from abrasion- and beam-sensitive corrosion products, showing a residual layer structure. This study demonstrates the capability of FTIR mapping, cross-section polishing, and state-of-the-art scanning electron microscopy imaging, and EDS element mapping to produce high-resolution elemental, molecular, and visual information about pitting corrosion mechanisms on a hot-dip galvanized steel sample.
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