| 1. |
- Svens, Pontus, et al.
(författare)
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Li-Ion Pouch Cells for Vehicle Applications-Studies of Water Transmission and Packing Materials
- 2013
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 6:1, s. 400-410
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Tidskriftsartikel (refereegranskat)abstract
- This study includes analysis of encapsulation materials from lithium-ion pouch cells and water vapour transmission rate (WVTR) measurements. WVTR measurements are performed on both fresh and environmentally stressed lithium-ion pouch cells. Capacity measurements are performed on both the fresh and the environmentally stressed battery cells to identify possible influences on electrochemical performance. Preparation of the battery cells prior to WVTR measurements includes opening of battery cells and extraction of electrode material, followed by resealing the encapsulations and adhesively mounting of gas couplings. A model describing the water diffusion through the thermal welds of the encapsulation are set up based on material analysis of the encapsulation material. Two WVTR equipments with different type of detectors are evaluated in this study. The results from the WVTR measurements show how important it is to perform this type of studies in dry environment and apply a rigorous precondition sequence before testing. Results from modelling confirm that the WVTR method has potential to be used for measurements of water diffusion into lithium-ion pouch cells. Consequently, WVTR measurements should be possible to use as a complement or alternative method to for example Karl Fisher titration.
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| 2. |
- Acevedo Gomez, Yasna, et al.
(författare)
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Reformate from biogas used as fuel in a PEM fuel cell
- 2013
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Ingår i: EFC 2013 - Proceedings of the 5th European Fuel Cell Piero Lunghi Conference. ; , s. 163-164
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Konferensbidrag (refereegranskat)abstract
- The performance of a PEM fuel cell can be easily degraded by introducing impurities in the fuel gas. Since reformate of biogas from olive mill wastes will contain at least one third of carbon dioxide, its influence was studied on a PtRu catalyst. A clean reformate gas for the anode (67% H2 and 33% CO2) without any traces of other compounds was used and electrochemical measurements showed that the performance of the fuel cell was hardly affected. However, diluting the hydrogen with higher amounts of CO2 will reduce the performance remarkably.
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| 3. |
- 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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| 4. |
- Degerman Engfeldt, Johnny, et al.
(författare)
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Methodology for measuring current distribution effects in electrochromic smart windows
- 2011
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 50:29, s. 5639-5646
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Tidskriftsartikel (refereegranskat)abstract
- Electrochromic (EC) devices for use as smart windows have a large energy-saving potential when used in the construction and transport industries. When upscaling EC devices to window size, a well-known challenge is to design the EC device with a rapid and uniform switching between colored (charged) and bleached (discharged) states. A well-defined current distribution model, validated with experimental data, is a suitable tool for optimizing the electrical system design for rapid and uniform switching. This paper introduces a methodology, based on camera vision, for experimentally validating EC current distribution models. The key is the methodology's capability to both measure and simulate current distribution effects as transmittance distribution. This paper also includes simple models for coloring (charging) and bleaching (discharging), taking into account secondary current distribution with charge transfer resistance and ohmic effects. Some window-size model predictions are included to show the potential for using a validated EC current distribution model as a design tool.
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| 5. |
- Degerman Engfeldt, Johnny, 1982-
(författare)
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Predicting Electrochromic Smart Window Performance
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The building sector is one of the largest consumers of energy, where the cooling of buildings accounts for a large portion of the total energy consumption. Electrochromic (EC) smart windows have a great potential for increasing indoor comfort and saving large amounts of energy for buildings. An EC device can be viewed as a thin-film electrical battery whose charging state is manifested in optical absorption, i.e. the optical absorption increases with increased state-of-charge (SOC) and decreases with decreased state-of-charge. It is the EC technology's unique ability to control the absorption (transmittance) of solar energy and visible light in windows with small energy effort that can reduce buildings' cooling needs. Today, the EC technology is used to produce small windows and car rearview mirrors, and to reach the construction market it is crucial to be able to produce large area EC devices with satisfactory performance. A challenge with up-scaling is to design the EC device system with a rapid and uniform coloration (charging) and bleaching (discharging). In addition, up-scaling the EC technology is a large economic risk due to its expensive production equipment, thus making the choice of EC material and system extremely critical. Although this is a well-known issue, little work has been done to address and solve these problems. This thesis introduces a cost-efficient methodology, validated with experimental data, capable of predicting and optimizing EC device systems' performance in large area applications, such as EC smart windows. This methodology consists of an experimental set-up, experimental procedures and a twodimensional current distribution model. The experimental set-up, based on camera vision, is used in performing experimental procedures to develop and validate the model and methodology. The two-dimensional current distribution model takes secondary current distribution with charge transfer resistance, ohmic and time-dependent effects into account. Model simulations are done by numerically solving the model's differential equations using a finite element method. The methodology is validated with large area experiments. To show the advantage of using a well-functioning current distribution model as a design tool, some EC window size coloration and bleaching predictions are also included. These predictions show that the transparent conductor resistance greatly affects the performance of EC smart windows.
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| 6. |
- Ebin, B., et al.
(författare)
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Electrochemical properties of nanocrystalline LiCu xMn 2-xO 4 (x = 0.2-0.6) particles prepared by ultrasonic spray pyrolysis method
- 2012
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 136:2-3, s. 424-430
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Tidskriftsartikel (refereegranskat)abstract
- The nanocrystalline LiCu xMn 2-xO 4 (x = 0.2-0.6) particles were prepared by ultrasonic spray pyrolysis method using lithium nitrate, manganese nitrate and copper nitrate salts at 800 °C in air atmosphere. Particle properties were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy. Besides, voltammetric and galvanostatic tests were performed to investigate the effects of the copper substituted on electrochemical behavior. Particle characterization studies showed that low copper substituted nanocrystalline particles had single spinel structure, and increasing amount caused tendency of second spinel phase formation. Particles, ranging between 250 nm and 1.5 μm size, were formed by aggregation of nanoparticles. The cumulative discharge capacities of LiCu 0.2Mn 1.8O 4 were determined as 122, 105 and 87 mAh g -1 at 0.5, 1 and 2 C rates, respectively between 4.8 and 3 V potential range. The capacity fade is 44% of initial capacity after 50 cycles at 0.5C rate. Results showed that electrochemical properties of LiCu xMn 2-xO 4 (x = 0.2-0.6) particles were impaired by increasing Cu substitute due to the second phase formation and ionic displacement in the lattice.
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| 7. |
- Ebin, B., et al.
(författare)
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Electrochemical properties of nanocrystalline LiFe xMn 2-xO 4 (x = 0.2-1.0) cathode particles prepared by ultrasonic spray pyrolysis method
- 2012
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 76, s. 368-374
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Tidskriftsartikel (refereegranskat)abstract
- The nanocrystalline LiFe xMn 2-xO 4 (x = 0.2-1.0) particles were prepared by ultrasonic spray pyrolysis method using nitrate salts of ingredients at 800°C in air atmosphere. Particle properties were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy. Besides, cyclic voltammetry and galvanostatic tests were performed to investigate the effects of the iron substituent amount on electrochemical behavior. Particle characterization studies show that nanocrystalline particles have spinel structure and they are in submicron size range with spherical morphology. The lowest iron doped sample (LiFe 0.2Mn 1.8O 4) exhibits 117 mAh g -1 cumulative discharge capacity at 0.5 C and 88% capacity retention for 4 V plateau after 50 cycles. At higher iron concentrations, substituent tends to occupy the 8a tetrahedral sites, which prevent the lithium transport in the lattice during charge-discharge process. Increasing of the iron amount in the spinel structure causes the deterioration of the electrochemical performance.
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| 8. |
- Ebin, Burcak, et al.
(författare)
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Preparation and electrochemical properties of spinel LiFexCuyMn1.2O4 by ultrasonic spray pyrolysis
- 2014
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 40:1, s. 1019-1027
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Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline LiFexCuyMn1.2O4 (x and y=0.2, 0.4 and 0.6) particles were prepared by the ultrasonic spray pyrolysis method using nitrate salts at 800 degrees C in air atmosphere. Particle properties were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Also, cyclic voltammetry and galvanostatic tests were performed to investigate the effects of the double substituent and doping amounts on electrochemical behavior. Results show that the aggregation of nanocrystallites around 90 nm size formed submicron spherical cathode particles. Transition metal ratios in particles exhibited a perfect fit with desired amounts. Although the change of iron and copper amounts do not show significant differences in the particle size and shape morphology, they modify the 4 V and 3 V potential plateaus of spinel LiMn2O4. The discharge capacities of LiFe0.2Cu0.6Mn1.2O4 particles are 39 and 23 mAh g(-1) for 4 and 2.6 V potential regions, respectively. 4 V discharge capacity disappeared with increasing of iron and decreasing of copper contents due to random occupation of iron and copper ions in the spinel lattice.
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| 9. |
- Eric, Jacques, et al.
(författare)
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Impact of the mechanical loading on the electrochemical capacity of carbon fibres for use in energy storage composite materials
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Reducing system mass for improvements in system performance has become a priority for future applications such as mobile phones or electric vehicles which require load bearing components and electrical energy storage devices. Structure and energy storage are usually subsystems with the highest mass contributions but energy storage components are structurally parasitic. A novel solution is a multifunctional lightweight design combining these two functions in a single material entity able to simultaneously bear mechanical loads as a carbon fiber composite component and store electrochemical energy as a lithium-ion battery.
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| 10. |
- Guan, Tingting, et al.
(författare)
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Investigation of the prospect of energy self-sufficiency and technical performance of an integrated PEMFC (proton exchange membrane fuel cell), dairy farm and biogas plant system
- 2014
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 130, s. 685-691
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Tidskriftsartikel (refereegranskat)abstract
- A PEMFC fuelled with hydrogen is known for its high efficiency and low local emissions. However, the generation of hydrogen is always a controversial issue for the application of the PEMFC due to the use of fossil fuel and the possible carbon dioxide emissions. Presently, the PEMFC-CHP fed with renewable fuels, such as biogas, appears to be the most attractive energy converter-fuel combination. In this paper, an integrated PEMFC-CHP, a dairy farm and a biogas plant are studied. A PEMFC-CHP fed with reformate gas from the biogas plant generates electricity and heat to a dairy farm and a biogas plant, while the dairy farm delivers wet manure to the biogas plant as the feedstock for biogas production. This integrated system has been modelled for steady-state conditions by using Aspen Plus (R). The results indicate that the wet manure production of a dairy farm with 300 milked cows can support a biogas plant to give 1280 MW h of biogas annually. Based on the biogas production, a PEMFC-CHP with a stack having an electrical efficiency of 40% generates 360 MW h electricity and 680 MW h heat per year, which is enough to cover the energy demand of the whole system while the total efficiency of the PEMFC-CHP system is 82%. The integrated PEMFC-CHP, dairy farm and biogas plant could make the dairy farm and the biogas plant self-sufficient in a sustainable way provided the PEMFC-CHP has the electrical efficiency stated above. The effect of the methane conversion rate and the biogas composition on the system performance is discussed. Moreover, compared with the coal-fired CUP plant, the potentially avoided fossil fuel consumption and CO2 emissions of this self-sufficient system are also calculated.
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