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  • 201.
    Mussa, Abdilbari
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Klett, Matilda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. Scania CV AB, SE-151 87 Södertälje, Sweden.
    Gudmundson, Peter
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Svens, P.
    Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Inhomogeneous active layer contact loss in a cycled prismatic lithium-ion cell caused by the jelly-roll curvature2018In: Journal of Energy Storage, E-ISSN 2352-152X, Vol. 20, p. 213-217Article in journal (Refereed)
    Abstract [en]

    Internal resistance is a key parameter that affects the power, energy, efficiency, lifetime, and safety of a lithium-ion battery. It grows due to chemical and mechanical battery wear during ageing. In this work, the effect of the jelly-roll winding curvature on impedance rise is investigated. NMC electrode samples, harvested from the curved as well as the flat regions of the jelly-roll from cycle-aged and calendar-aged prismatic cells (25 Ah, hard casing) are investigated by electrochemical impedance spectroscopy. After cycling, larger impedance rise is observed at the outer radius (concave) of the curved region compared to the inner radius (convex) or the flat region of the jelly-roll, and the difference increases with a decrease in the jelly-roll radius of curvature, from the cell skin towards the core. To identify the causes behind the observed difference in the impedance rise, investigations at different external compression (0 and 2.5 MPa) and temperature (5 and 25 °C) are performed. The results show that contact loss between the current collector and the active layer is the main source of the difference in impedance rise. Mechanical mechanisms that may cause the contact loss are discussed and design recommendations to mitigate the rise in impedance are given. 

  • 202.
    Mussa, Abdilbari Shifa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Klett, Matilda
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindström, Rakel Wreland
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Fast-charging to a partial state of charge in lithium-ion batteries: A comparative ageing study2017In: Journal of Energy Storage, ISSN 2352-152X, Vol. 13, p. 325-333Article in journal (Refereed)
    Abstract [en]

    At electric vehicle fast-charging stations, it is generally recommended to avoid charging beyond similar to 80% State-of-Charge (SOC) since topping-off to full capacity disproportionately increases the charging time. This necessitates studying its long-term impact compared to slower rate charging to full capacity typical of home or residential charging. Here we present the long-term ageing effects on commercial 18650 NMC-LMO/graphite cell cycled between 2.6-4.2 V at three different charging protocols: 1.5 C-rate fast-partial charging ( to 82.5% SOC), 0.5 C-rate slow standard charging without or with a constant-voltage step (to 93% or 100% SOC). Quantitative discharge-curve and postmortem analyses are used to evaluate ageing. The results show that ageing rate increases in the order: fast-partial charging < standard charging < standard charging with constant-voltage period, indicating that higher SOC-range near full capacity is more detrimental to battery life than fast-charging. The capacity fade is totally dominated by cyclable-lithium loss. The similar to 8% NMC-LMO active material loss has negligible impact on the cell capacity fade due to the electrodes excess material in the fresh cell and its moderate loss rate with ageing compared to the cyclable-lithium. Similar ageing modes in terms of capacity fade and impedance rise are found irrespective of the charging protocol.

  • 203.
    Mussa, Abdilbari Shifa
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Klett, Matilda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Effects of external pressure on the performance and ageing of single-layer lithium-ion pouch cells2018In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 385, p. 18-26Article in journal (Refereed)
    Abstract [en]

    The effects of external compression on the performance and ageing of NMC(1/3)/Graphite single-layer Li-ion pouch cells are investigated using a spring-loaded fixture. The influence of pressure (0.66, 0.99, 1.32, and 1.98 MPa) on impedance is characterized in fresh cells that are subsequently cycled at the given pressure levels. The aged cells are analyzed for capacity fade and impedance rise at the cell and electrode level. The effect of pressure distribution that may occur in large-format cells or in a battery pack is simulated using parallel connected cells. The results show that the kinetic and mass transport resistance increases with pressure in a fresh cell. An optimum pressure around 1.3 MPa is shown to be beneficial to reduce cyclable-lithium loss during cycling. The minor active mass losses observed in the electrodes are independent of the ageing pressure, whereas ageing pressure affects the charge transfer resistance of both NMC and graphite electrodes and the ohmic resistance of the cell. Pressure distribution induces current distribution but the enhanced current throughput at lower pressures cell does not accelerate its ageing. Conclusions from this work can explain some of the discrepancies in non-uniform ageing reported in the literature and indicate coupling between electrochemistry and mechanics.

  • 204. Noponen, M.
    et al.
    Ihonen, Jari
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Current distribution measurements in a PEFC with net flow geometry2004In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 34, no 3, p. 255-262Article in journal (Refereed)
    Abstract [en]

    A measurement system for current distribution mapping for a PEFC has been developed. The segmented anode is constructed so as to have high thermal conductivity in order to prevent the formation of large temperature gradients between the electrodes. The construction is therefore feasible for use at high current densities. Both segmented and unsegmented gas diffusion layers are used. The effect of inlet humidification and gas composition at the cathode side is studied. In addition, two different flow geometries are studied. The results show that the measurement system is able to distinguish between current distribution originating from differences in proton conductivity, species concentration and gas diffusion layer properties.

  • 205. Noponen, Matti
    et al.
    Birgersson, Erik
    KTH, Superseded Departments, Mechanics.
    Ihonen, Jari
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Vynnycky, Michael
    KTH, Superseded Departments, Mechanics.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    A two-phase non-isothermal PEFC model: Theory and validation2004In: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 4, no 4, p. 365-377Article in journal (Refereed)
    Abstract [en]

    A two-dimensional, non-isothermal, two-phase model of a polymer electrolyte fuel cell (PEFC) is presented. The model is developed for conditions where variations in the stream-wise direction are negligible. In addition, experiments were conducted with a segmented cell comprised of net flow fields. The, experimentally obtained, current distributions were used to validate the PEFC model developed. The PEFC model includes species transport and the phase change of water, coupled with conservation of momentum and mass, in the porous backing of the cathode, and conservation of charge and heat throughout the fuel cell. The current density in the active layer at the cathode is modelled with an agglomerate model, and the contact resistance for heat transfer over the material boundaries is taken into account. Good agreement was obtained between the modelled and experimental polarization curves. A temperature difference of 6°C between the bipolar plate and active layer on the cathode, and a liquid saturation of 6% at the active layer in the cathode were observed at 1 A cm-2.

  • 206. Nordlund, J.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    A model for the porous direct methanol fuel cells anode2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 9, p. A1107-A1113Article in journal (Refereed)
    Abstract [en]

    The influence of the porous structure on the direct methanol fuel cells (DMFC) anode was studied with a model and experimentally. An agglomerate model of the electrode is used and kinetic equations based on the reaction mechanism for the electrochemical oxidation of methanol are derived. A 1 cm(2) fuel cell is used for experimental validation of the model. The model shows that mass transport limitations in the agglomerates are small and that the anode model can be simplified. However, the mass transport limitations in the liquid phase are of importance at lower methanol concentrations. Experiments studying methanol oxidation at very low current show that electrochemical oxidation of methanol starts at a certain onset-potential and does not follow a simple Butler-Volmer relationship.

  • 207. Nordlund, J.
    et al.
    Roessler, A.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    The influence of electrode morphology on the performance of a DMFC anode2002In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 32, no 3, p. 259-265Article in journal (Refereed)
    Abstract [en]

    For low concentrations of methanol, mass transfer in the electrode is a limiting parameter for the direct methanol fuel cell (DMFC). To improve mass transfer, it is possible to induce convection in the gas backing layer or even in the porous electrode. In this study electrodes with different amounts of PTFE were compared to observe the influence of morphology on the anode performance. The hypothesis was that adding PTFE to the anode may make the morphology more favourable for carbon dioxide to evolve as a gas by creating the necessary pore sizes. Electrode performance was characterized electrochemically and the anode layer structure was studied using SEM, Hg-porosimetry and the van der Pauw method for measuring electric conductivity. Pores smaller than 0.04 mum were unaffected by adding PTFE while the volume fraction of pores of 0.04-1.0 mum diameter increased. Electrodes with 50% PTFE also performed as nonhydrophobized, despite the much higher ohmic losses and thickness. This implies that, above a certain amount, adding PTFE has a positive effect and that optimizing the electrode with PTFE may give better performance than electrodes without PTFE. The results suggest that gas evolves within the electrode, giving improved mass transfer in the liquid phase.

  • 208.
    Nordlund, Joakim
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Temperature-dependent kinetics of the anode in the DMFC2004In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 151, no 9, p. A1357-A1362Article in journal (Refereed)
    Abstract [en]

    The methanol oxidation kinetics was studied in a direct methanol fuel cell (DMFC) anode at 303, 323, and 343 K. The experimental result was fitted to a model for the porous anode and the kinetic parameters were extracted. In addition, a simplified kinetic equation for the porous anode was derived which directly gives the current density of the porous anode as a function of the potential, temperature, and methanol concentration. Both the more rigorous kinetic model and the empirical model fit well to the experimental data. The methodology used is shown to be very useful for applied modeling of the DMFC.

  • 209.
    Nordlund, Joakim
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Picard, C
    Birgersson, Erik
    KTH, Superseded Departments, Mechanics.
    Vynnycky, Michael
    KTH, Superseded Departments, Mechanics.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    The design and usage of a visual direct methanol fuel cell2004In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 34, no 8, p. 763-770Article in journal (Refereed)
    Abstract [en]

    In order to better understand the influence of gas evolution on the performance of the direct methanol fuel cell ( DMFC) anode, a visual DMFC, comprising of a transparent anode and a cathode endplate with an integrated heat exchanger, and a picture analysis methodology were developed. The result was an inexpensive, but very powerful, tool for analyzing the role of two-phase flow. An important finding is that gas bubbles do not appear uniformly throughout the fluid flow matrix, but rather only at a few active sites. Another important finding is that the gas saturation ( volume fraction of gas/volume fraction of liquid) increases along the streamwise direction.

  • 210.
    Nowak, Andrzej
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Hagberg, Johan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Leijonmarck, Simon
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Schweinebarth, Hannah
    Baker, Darren
    Uhlin, Anders
    Tomani, Per
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Lignin-based carbon fibers for renewable and multifunctional lithium-ion battery electrodes2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 2, p. 81-90Article in journal (Refereed)
    Abstract [en]

    Lignin-based carbon fibers (LCFs) from the renewable resource softwood kraft lignin were synthesized via oxidative thermostabilization of pure melt-spun lignin and carbonization at different temperatures from 1000 degrees C to 1700 degrees C. The resulting LCFs were characterized by tensile testing, scanning electron microscopy (SEM), X-ray diffraction (XRD) and confocal Raman spectroscopy. The microstructure is mainly amorphous carbon with some nanocrystalline domains. The strength and stiffness are inversely proportional to the carbonization temperature, while the LCFs carbonized at 1000 degrees C exhibit a strength of 628 MPa and a stiffness of 37 GPa. Furthermore, the application potential of LCFs was evaluated as negative electrodes in a lithium-ion battery (LIB) by electrochemical cycling at different current rates in a half-cell setup. The capacity drops with the carbonization temperature and the LCFs carbonized at 1000 degrees C have a capacity of 335 mAh g(-1). All LCFs showed good cycling stability. Because of the mechanical integrity and conductivity of the LCFs, there is no need to apply current collectors, conductive additives or binders. The advantage is an increased gravimetric energy density compared to graphite, which is the most common negative electrode material. LCFs show a promising multifunctional behavior, including good mechanical integrity, conductivity and an ability to intercalate lithium for LIBs.

  • 211.
    Nylén, Linda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Cornell, Ann M.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Investigation of the oxygen evolving electrode in pH-neutral electrolytes: Modelling and experiments of the RDE-cell2007In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, no 13, p. 4513-4524Article in journal (Refereed)
    Abstract [en]

    A model has been developed to illustrate the complex interplay between the acidifying electrode reactions for oxygen evolution, mass transport and homogeneous reactions in pH-neutral electrolytes. Modelled polarisation curves of the oxygen evolution reaction were verified by polarisation curves experimentally measured in 5 M NaClO4 on a RDE of DSA material. The conditions in the simulations and in the experiments were similar to those in the chlorate process (high ionic strength, 70 degrees C, chromate-containing electrolyte, DSA electrode), in which the oxygen evolution reaction is one of the possible side reactions. The model predicted the concentration gradients of H+, OH-, CrO42- and HCrO4- during oxygen evolution on the RDE. It was found that an important part of the chromate buffering effect at high current densities occurs in a thin (in the order of nanometers) reaction layer at the anode. From comparisons between the model and experiments, a buffering reaction has been proposed. The most likely reaction for the chromate buffering in the investigated system is CrO42- reacting with water to HCrO4- and OH-. In the chlorate process, where chromate is a buffer and oxygen evolution is a side reaction, it is likely that chromate promotes oxygen evolution from OH-.

  • 212.
    Nyman, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    A Theoretical and Experimental Study of the Mass Transport in Gel Electrolytes: I. Mathematical Analysis of Characterization Method2011In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 6, p. A628-A635Article in journal (Refereed)
    Abstract [en]

    Mass transport of lithium ions is one of the major limitations to the performance of high-rate lithium-ion batteries. This paper presents an analysis of a mass transport characterization method for gel electrolytes. The method is based on a Maxwell-Stefan transport model, which takes into account the polymer as an active specie in the transport. Nine apparent transport properties are defined from the model and their dependence on the Maxwell-Stefan diffusivities and the thermodynamic enhancement factors are presented. The characterization method is analyzed by finding analytical expressions that describe the characterization experiments. From the expressions it can be seen how the nine apparent transport properties influence the experimental response. The conclusions of the analysis will be used later in a characterization of the gel electrolyte: LiPF6-ethylene carbonate (EC)-propylene carbonate (PC)-poly(vinylidenefluoride-hexafluoropropylene) P(VdF-HFP).

  • 213.
    Nyman, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Electrochemical characterisation and modelling of the mass transport phenomena in LiPF6-EC-EMC electrolyte2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 22, p. 6356-6365Article in journal (Refereed)
    Abstract [en]

    The conductivity, the salt diffusion coefficient, the lithium-ion transport number and the thermodynamic factor of the salt and the solvent were reported for LiPF6 in EC:EMC (3:7) at 25 IC and for concentrations between 0.2 and 2.0 mol/d M3. The mass transport in the electrolyte was fully characterised by combining three types of electrochemical experiments; concentration cells, galvanostatic polarisation experiments and electrochemical impedance measurements with a mathematical description of the mass transport in the electrolyte. The apparent salt diffusion coefficient had a local maximum in the concentration range, while the viscosity-dependent salt diffusion coefficient decreased from 4.1 X 10-10 M2/s at 0.2 mol/d M3 to 4.4 x 10-11 M2/s at 2.0 mol/dM3. Both the thermodynamic factor and the conductivity varied strongly with the concentration. The conductivity had a maximum of 9.5 mS/cm at 1.0 mol/dm 3. The lithium-ion transport numberwith respect to the room decreased with increasing salt concentration, with a maximum of 0.37 at 0.2 molldm 3 in the concentration range. The Maxwell-Stefan diffusivities and the electrolyte potential drop in a lithium-ion battery at steady state were lastly calculated from the obtained transport properties. An analysis of the characterisation method was also done on the basis of the characterisation results.

  • 214.
    Nyman, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, N. Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    A Theoretical and Experimental Study of the Mass Transport in Gel Electrolytes: II. Experimental Characterization of LiPF6-EC-PC-P(VdF-HFP)2011In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 6, p. A636-A643Article in journal (Refereed)
    Abstract [en]

    The mass transport in a gel consisting of LiPF6 dissolved in ethylene carbonate (EC), propylene carbonate (PC) and poly(vinylide-nefluoride-hexafluoropropylene) (P(VdF-HFP)) was characterized at 25 degrees C. Four diffusion coefficients, two transport numbers, one conductivity and two parameters describing the relationship between a concentration and a potential gradient were obtained in the characterization. The transport properties were obtained by optimizing a Maxwell-Stefan based transport model to data from four types of experiments. The transport model and the characterization method were analyzed in Part I. In order to give the results a comprehensible interpretation and to present a way of benchmarking electrolytes, we introduce the concept of a normalized potential gradient for gel electrolytes. The optimum composition range of the gel in terms of mass transport was found to lie between 5 and 7 wt % LiPF6 and as little polymer as possible without compromising the mechanical stability. It is suggested that measuring the normalized potential gradient can be used as a screening method when benchmarking electrolytes.

  • 215.
    Nyman, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zavalis, Tommy Georgios
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Elger, Ragna
    Swerea.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    A New Methodology for Evaluating the High-Power Behavior of a Li-ion Battery Cell2010In: Rechargeable Lithium-Ion Batteries, Electrochemical Society, 2010, no 36, p. 253-262Conference paper (Refereed)
    Abstract [en]

    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.

  • 216.
    Nyman, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zavalis, Tommy Georgios
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Elger, Ragna
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Analysis of the Polarization in a Li-Ion Battery Cell by Numerical Simulations2010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 11, p. A1236-A1246Article in journal (Refereed)
    Abstract [en]

    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.

  • 217.
    Oyarce, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Gonzalez, Carlos
    Lima, Raquel Bohn
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Direct sorbitol proton exchange membrane fuel cell using moderate catalyst loadings2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 116, p. 379-387Article in journal (Refereed)
    Abstract [en]

    Recent progress in biomass hydrolysis has made it interesting to study the use of sorbitol for electricity generation. In this study, sorbitol and glucose are used as fuels in proton exchange membrane fuel cells having 0.9 mg cm(-2) PtRu/C at the anode and 0.3 mg cm(-2) Pt/C at the cathode. The sorbitol oxidation was found to have slower kinetics than glucose oxidation. However, at low temperatures the direct sorbitol fuel cell shows higher performance than the direct glucose fuel cell, attributed to a lower degree of catalyst poisoning. The performance of both fuel cells is considerably improved at higher temperatures. High temperatures lower the poisoning, allowing the direct glucose fuel cell to reach a higher performance than the direct sorbitol fuel cell. The mass specific peak power densities of the direct sorbitol and direct glucose fuel cells at 65 degrees C was 3.2 mW Mg-catalyst(-1) and 3.5 mW Mg-catalyst(-1), respectively. Both of these values are one order of magnitude larger than mass specific peak power densities of earlier reported direct glucose fuel cells using proton exchange membranes. Furthermore, both the fuel cells showed a considerably decrease in performance with time, which is partially attributed to sorbitol and glucose crossover poisoning the Pt/C cathode.

  • 218.
    Oyarce, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Holmström, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Boden, A.
    Randstrom, S.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    In-situ Measurements of Contact Resistance and In-situ Durability studies of Steels and Coatings to be used as Bipolar Plates in PEMFCs2009In: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, Vol. 25, no 1, p. 1791-1801Article in journal (Refereed)
    Abstract [en]

    In this study, a fast, low cost and reliable methodology for bipolar plate material screening and testing is presented. Ex-situ measurements of contact resistance are used as a screening tool, while in-situ measurements such as: fuel cell performance, in-situ contact resistance, high frequency impedance spectroscopy, together with post analysis of stainless steel surfaces, MEAs and fuel cell effluent water evaluates the real performance of the most promising stainless steels and coatings, providing reliable data for future fuel cell stack test.

  • 219.
    Oyarce, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Holmström, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Bodén, A.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Operating conditions affecting the contact resistance of bi-polar plates in proton exchange membrane fuel cells2013In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 231, p. 246-255Article in journal (Refereed)
    Abstract [en]

    Both ex-situ and in-situ measurements of contact resistance between gas diffusion layer (GDL) and bi-polar plate (BPP) were carried out using the same fuel cell hardware. Each BPP sample was submitted to ex-situ testing at room temperature, ex-situ testing in simulated fuel cell environment and in-situ testing, isolating the effect of specific operating conditions on the contact resistance. Increasing cell temperatures and relative humidity (RH) of the gases lowered the contact resistance. However, the presence of liquid water, measured as an increase in pressure drop over the cathode, affected the contact resistance negatively. High current density operation raises the temperature of the cell, but simultaneously increases the water content at the cathode, causing an increase of the contact resistance. In the case of uncoated steel 316L and gold-coated steel 316L, high current density operation for an extended period of time also caused a progressive deterioration of the contact resistance, which without this in-situ measurement could have been mistaken for other ohmic losses, e.g. increased membrane resistance due to metal ion poisoning.

  • 220.
    Oyarce, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hussami, Linda L.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Corkey, Robert W.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Polyhedral Carbon Nanoforms as catalyst support in a Proton Exchange Membrance cathodeManuscript (preprint) (Other academic)
  • 221.
    Oyarce, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    The Electrochemical Response of a Corroded PEMFC Cathode: Mass-transport at low RHManuscript (preprint) (Other academic)
  • 222.
    Oyarce, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zakrisson, Erik
    Ivity, Matthew
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Baumann Ofstad, Axel
    Bodén, Andreas
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Comparing shut-down strategies for proton exchange membrane fuel cells2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 254, p. 232-240Article in journal (Refereed)
    Abstract [en]

    Application of system strategies for mitigating carbon corrosion of the catalyst support in proton exchange fuel cells (PEMFCs) is a requirement for PEMFC systems, especially in the case of systems for transport application undergoing thousands of start-ups and shut-downs (SU/SD) during its lifetime. This study compares several of the most common shut-down strategies for 1100 cycles SU/SD cycles at 70 C and 80% RH using commercially available fuel cell components. Each cycle simulates a prolonged shut-down, i.e. finishing each cycle with air filled anode and cathode. Furthermore, all start-ups are unprotected, i.e. introducing the H2 rich gas into an air filled anode. Finally, each cycle also includes normal fuel cell operation at 0.5 A cm-2 using synthetic reformate/air. H2 purge of the cathode and O2 consumption using a load were found to be the most effective strategies. The degradation rate using the H2 purge strategy was 23 μV cycle-1 at 0.86 A cm-2 using H 2 and air at the anode and cathode, respectively. This degradation rate may be regarded as a generally low value, especially considering that this value also includes the degradation rate caused by unprotected start-ups.

  • 223. Peelen, W. H. A.
    et al.
    Hemmes, K.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    CO2 dissolution into a 52/48 mol % Li/Na carbonate melt and the molten carbonate fuel cell cathode2000In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 147, no 6, p. 2122-2125Article in journal (Refereed)
    Abstract [en]

    O2- concentration relaxation experiments in a 52/48 moi % Li/Na molten carbonate melt saturated with NiO were performed. The Ni2+ was added to act as a probe for the O2- concentration. The dynamic behavior of the CO2 and O2- concentration during the relaxation of the melt back to the initial equilibrium was studied by recording square wave voltammograms. Our experiments show clearly that CO2 dissolution is the slowest step in the relaxation. Consequently the values for the recombination reaction rate obtained in other studies are not correct, since in them a fast CO2 dissolution was assumed.(1,2) A CO2 gas dissolution rate of 25(+/-5) 10(-4) cm/s and Henry's constant for CO2 of 20(+/-3) mu mol atm(-1) cm(-3) at 650 degrees C could be determined. Our numbers were used in simple calculations of the performance of the porous molten carbonate fuel cell cathode, and indicate that the CO2 dissolution rate determines the lower limit for p(CO2) Of 0.05 arm at 150 mA/cm(2) for proper cathode operation.

  • 224. Pettersson, Dan
    et al.
    Gustavsson, Marie
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    An experimental system for evaluation of well-defined catalysts on nonporous electrodes in realistic DMFC environment2006In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, no 28, p. 6584-6591Article in journal (Refereed)
    Abstract [en]

    This paper reports on an experimental setup wich enables us to investigate planar model catalysts in an environment closely resembling the environment found in an actual direct methanol fuel cell. The working electrodes were nano-structured catalyst particles immobilised on planar supports, reducing many of the commonly present non-catalyst related effects in conventional porous electrodes. Colloidal lithography was used for nano-structuring the samples. Nation was used as electrolyte. Results are presented for the oxidation of methanol, formaldehyde, formic acid and carbon monoxide at temperatures between 30 and 70 degrees C on Pt particles supported on glassy carbon disks.

  • 225.
    Rexed, Ivan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    della Pietra, Massimiliano
    University of Perugia.
    McPhail, Stephen
    ENEA.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Molten carbonate fuel cells for CO2 separation and segregation by retrofitting existing plants - An analysis of feasible operating windows and first experimental findings2015In: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 35, p. 120-130Article in journal (Refereed)
    Abstract [en]

    Molten carbonate fuel cells (MCFC) used as active carbon dioxide concentrator units are a promising solution to reduce greenhouse gas (GHG) emissions from traditional combustion plants. The cell reaction transfers carbonate ions from the cathode to the anode and allows the fuel cell to simultaneously produce power and separate CO2 from a stream of flue gas. Carbon dioxide separation is of high interest for use in natural gas combined cycles and coal gas combustion plants, as a large part of anthropogenic CO2 worldwide originates from such installations. The flue gas from these types of combustion technologies typically contains 3-15% CO2, which is in the lower operational range of the MCFC. The aim of this work was to investigate the possibility to retrofit existing power plants with MCFC to reduce the total release of CO2 without necessarily reducing the power output, and to understand which kind of power plant could have the major benefits with an MCFC retrofitting. The performance of lab scale MCFC fed with simulated flue gas was evaluated, and a number of operational parameters, such as utilization factor and cathode humidification were varied to study the effect on fuel cell performance. The results show that it is feasible to operate the MCFC as a CO2 separator for simulated gas turbine flue gas; however, the voltage drop due to low CO2 concentration may restrict the operating window depending on various operating conditions.

  • 226.
    Rexed, Ivan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Effect of sulfur contaminants on MCFC performance2014In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, no 23, p. 12242-12250Article in journal (Refereed)
    Abstract [en]

    Molten carbonate fuel cells (MCFC) used as carbon dioxide separation units in integrated fuel cell and conventional power generation can potentially reduce carbon emission from fossil fuel power production. The MCFC can utilize CO2 in combustion flue gas at the cathode as oxidant and concentrate it at the anode through the cell reaction and thereby simplifying capture and storage. However, combustion flue gas often contains sulfur dioxide which, if entering the cathode, causes performance degradation by corrosion and by poisoning of the fuel cell. The effect of contaminating an MCFC with low concentrations of both SO2 at the cathode and H2S at the anode was studied. The poisoning mechanism of SO2 is believed to be that of sulfur transfer through the electrolyte and formation of H2S at the anode. By using a small button cell setup in which the anode and cathode behavior can be studied separately, the anodic poisoning from SO2 in oxidant gas can be directly compared to that of H2S in fuel gas. Measurements were performed with SO2 added to oxidant gas in concentrations up to 24 ppm, both for short-term (90 min) and for long-term (100 h) contaminant exposure. The poisoning effect of H2S was studied for gas compositions with high- and low concentration of H-2 in fuel gas. The H2S was added to the fuel gas stream in concentrations of 1, 2 and 4 ppm. Results show that the effect of SO2 in oxidant gas was significant after 100 h exposure with 8 ppm, and for short-term exposure above 12 ppm. The effect of SO2 was also seen on the anode side, supporting the theory of a sulfur transfer mechanism and H2S poisoning. The effect on anode polarization of H2S in fuel gas was equivalent to that of SO2 in oxidant gas.

  • 227.
    Rexed, Ivan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Performance degradation of Molten Carbonate Fuel Cells caused by SO2 in simulated flue gasManuscript (preprint) (Other academic)
    Abstract [en]

    The effect on MCFC performance degradation SO2 contaminant at the cathode, in combination with operating the fuel cell with CO2 lean oxidant gas, simulating combustion flue gas, was evaluated. Of special focus was the effect of electrolyte degradation.

     Measurements were performed to test the effect of SO2 in the oxidant gas stream, followed by regeneration with clean gas. A 3cm2 button cell MCFC allowing active electrolyte management by refilling was for 1500h to benchmark the performance degradation without contaminants. In order to study the poisoning effect of SO2 entering the fuel cell gas, the MCFC was operated for 250h with the addition of 18ppm SO2 in the oxidant gas. Electrolyte was added after 1500h of benchmark operation and after 250h of contaminant operation. The addition of 18ppm SO2 greatly accelerated the performance degradation of the fuel cell. Measurements showed that the internal resistance was the single factor which was most affected by the SO2 poisoning, and that the performance degradation after 250h was not reversed by regeneration with clean gas, but with the addition of fresh electrolyte. This led us to conclude that SO2 in oxidant gas leads to an accelerated loss of electrolyte and subsequent decrease in conductivity of the electrolyte, causing loss of performance and meeting end of life criteria after relatively short operational time. Other factors, such as poisoning of the anode and corrosion of cathode side current collectors, were also detected. 

  • 228. Samarasingha, Pushpaka B.
    et al.
    Wijayasinghe, Athula
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Dissanayake, Lakshman
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Development of cathode materials for lithium ion rechargeable batteries based on the system Li(Ni1/3Mn1/3Co(1/3-x)Mx)O-2, (M = Mg, Fe, Al and x=0.00 to 0.33)2014In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 268, p. 226-230Article in journal (Refereed)
    Abstract [en]

    This study was based on developing Li(Ni1/3Mn1/3Co(1/3-x)Mx)O-2, (M = Mg, Fe, Al and x = 0 to 0.33) materials by substituting expensive Co content in this NMC system with cheaper Mg, Fe and Al additives for the cathode application in rechargeable lithium ion batteries (LIB). The Pechini method, which is a low-cost wet chemical technique, was used for powder synthesis in this study. The XRD phase analysis revealed the formation of solid solutions of appropriate layered Li(Ni1/3Mn1/3Co(1/3-x)Mx)O-2 phase.of R-3m structure in the prepared compositions over x = 0.11 substitution of Fe and Mg. Furthermore, these Fe and Mg substituted compositions showed considerably higher electrical conductivity than the base material Li(Ni1/3Mn1/3Co(1/3-x)Mx)O-2 (over 0.9 x 10(-5) S/cm at 25 degrees C). In the cell studies, the Fe and Mg substituted compositions with x = 0.11 showed a specific capacity of 122 and 125 mAhg(-1), respectively, which are comparable to the specific capacity of the state-of-the-art LiCoO2 cathode material of LIB. Altogether, this study shows the ability of preparing these NMC materials by Pechini method with appropriate structural and electrochemical properties suitable for the LIB cathode.

  • 229.
    Saxe, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Hedström, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Rissanen, Markku
    ABB AB, Corporate Research.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Ridell, Bengt
    Grontmij AB, Energy Systems.
    Operating experience and energy system analysis of the biogas-powered 5 kW SOFC system in GlashusEtt2008In: Proceedings of the WREC X conference, 2008Conference paper (Refereed)
  • 230.
    Sevencan, Suat
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Guan, Tingting
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Ridell, Bengt
    Fuel cell based cogeneration: Comparison of electricity production cost for Swedish conditions2013In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 10, p. 3858-3864Article in journal (Refereed)
    Abstract [en]

    A good portion of greenhouse gas emissions is caused by the energy used in the built environment. Emission reduction goals may be achieved by combining cogeneration with fuel cells (PC). This paper investigates electricity production costs for PC based cogeneration systems with recent data for Swedish conditions. The types of FCs that are investigated are proton exchange membrane PC and molten carbonate FC. Based solely on cost, PC based cogeneration systems cannot compete with conventional systems. However, our results show that Molten Carbonate PC based cogeneration systems will be profitable by 2020. To compete with conventional systems, the capital cost, lifetime and efficiency of FCs must be improved. Creation of a reasonably broad market is essential since it will greatly help to reduce capital costs and operation and maintenance (O&M) costs, the dominating parts of the overall costs according to the analysis.

  • 231.
    Sevencan, Suat
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Alvfors, Per
    An Economical Comparison of Power-to-Gas Alternatives in Bozcaada - TurkeyManuscript (preprint) (Other academic)
    Abstract [en]

    Although currently conventional electricity generation methods dominate the market, the share of renewable energy systems is constantly increasing. Intermittent nature of solar and wind cause several problems. Power-to-gas is a method that can help with these problems by generating and storing hydrogen gas during off-peak hours so it can be reconverted into electricity via fuel cells and/or H2 internal combustion engines coupled with electricity generators during peak hours. In this study an economical evaluation of power-to-gas systems for an existing photovoltaic-Wind hybrid power system was made. Results indicate that although the photovoltaic-Wind may reduce the energy bill considerably when it is possible to sell electricity to the grid, coupling it with a power-to-gas system makes it unprofitable over the lifetime of the system.

  • 232.
    Sevencan, Suat
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Economic feasibility study of a fuel cell-based combined cooling, heating and power system for a data centre2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 111, p. 218-223Article in journal (Refereed)
    Abstract [en]

    The energy use of data centres is increasing as the data storage needs increase. One of the largest items in the energy use of these facilities is cooling. A fuel cell-based combined cooling, heating and power system can efficiently meet such a centre's need for cooling and in the meantime generate enough electricity for the centre and more. In this paper the economic feasibility of a fuel cell-based combined cooling, heating and power system that meets the energy demands of such a facility is investigated using operational data from an existing data centre in Stockholm, Sweden. The results show that although the system is not feasible with current energy prices and technology it may be feasible in the future with the projected changes in energy prices.

  • 233.
    Soares, Rudi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. KTH.
    Bessman, Alexander
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Svens, Pontus
    Scania.
    An Experimental Setup with Alternating Current Capability for Evaluating Large Lithium-Ion Battery Cells2018In: Batteries-Basel, ISSN 2313-0105, Vol. 4, no 3, article id 38Article in journal (Refereed)
    Abstract [en]

    In the majority of applications using lithium-ion batteries, batteries are exposed to some harmonic content apart from the main charging/discharging current. The understanding of the effects that alternating currents have on batteries requires specific characterization methods and accurate measurement equipment. The lack of commercial battery testers with high alternating current capability simultaneously to the ability of operating at frequencies above 200 Hz, led to the design of the presented experimental setup. Additionally, the experimental setup expands the state-of-the-art of lithium-ion batteries testers by incorporating relevant lithium-ion battery cell characterization routines, namely hybrid pulse power current, incremental capacity analysis and galvanic intermittent titration technique. In this paper the hardware and the measurement capabilities of the experimental setup are presented. Moreover, the measurements errors due to the setup’s instruments were analysed to ensure lithium-ion batteries cell characterization quality. Finally, this paper presents preliminary results of capacity fade tests where 28 Ah cells were cycled with and without the injection of 21 A alternating at 1 kHz. Up to 300 cycles, no significant fade in cell capacity may be measured, meaning that alternating currents may not be as harmful for lithium-ion batteries as considered so far.

  • 234.
    Soares, Rúdi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. KTH.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Lindbergh, Göran (Contributor)
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Svens, Pontus (Contributor)
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Analysis and Prediction of the Harmonic Content in the Battery Currentof a Commercial Hybrid-Electric BusIn: IEEE Transactions on Transportation ElectrificationArticle in journal (Refereed)
    Abstract [en]

    This paper presents a comparison of the harmoniccontent in the battery current in two, commercialhybrid electric vehicles (HEVs) (intercity passenger buses)when operated in realistic drive scenarios. These harmonicscan contribute to issues related to electromagnetic compatibilityand indirectly accelerate the aging of the battery dueto elevated cell temperatures caused by associated ohmiclosses. A key finding is that low-frequency harmonics (upto approximately 130 Hz) attributed to resolver eccentricityand non-ideal effects in the voltage-source inverter (VSI) (upto approximately 260 Hz) were significant in terms of magnitudes.Also, the variation between the two HEVs (in termsof current magnitude) were substantial for these harmonics.This is an important observation since it demonstratesthat significant, low-frequency harmonics can be presentin the battery current and that modeling and collectingexperimental data from a single corresponding vehicle maynot sufficiently represent the harmonic content in the batterycurrent for a fleet of vehicles.

  • 235.
    Soares, Rúdi
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Bessman, Alexander
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Svens, P.
    Measurements and analysis of battery harmonic currents in a commercial hybrid vehicle2017In: 2017 IEEE Transportation and Electrification Conference and Expo, ITEC 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 45-50Conference paper (Refereed)
    Abstract [en]

    In this paper, the harmonic content of the battery current in a commercial hybrid vehicle (bus) is measured and analyzed for a number of different driving situations. It is found that the most prominent harmonic reaches peak magnitudes that can be higher than 10% of the maximum dc-current level with a maximum frequency less than 150 Hz. Further, it is found that this harmonic can be approximated using a fitted, simple analytical expression with reasonable agreement for all driving situations considered.

  • 236.
    Soares, Rúdi
    et al.
    KTH.
    Bessman, Alexander
    KTH.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Lindbergh, Göran
    KTH.
    Svens, Pontus
    KTH.
    A Control Method for Battery Heating Using Alternating CurrentManuscript (preprint) (Other academic)
  • 237.
    Soares, Rúdi
    et al.
    KTH.
    Bessman, Alexander
    KTH.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Svens, Pontus
    KTH.
    An Experimental Setup with Alternating Current Capability for Evaluating Large Lithium-ion Batteries CellsManuscript (preprint) (Other academic)
  • 238.
    Sparr, Mari
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Bodén, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    A Steady-State Model of the Porous Molten Carbonate Fuel Cell Anode for Investigation of Kinetics and Mass Transfer2006In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, no 8, p. A1525-A1532Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper was to investigate the effect of gas phase mass transfer and the influence of different reactions on the anode performance and to understand previously made experiments better. This has been done by mathematically modeling how different effects influence the polarization curve of the anode. Some previously obtained experimental data were used as input for the model. In this study, results from using the mechanisms proposed for the hydrogen oxidation by Jewulski and Suski and Ang and Sammels, respectively, show that they are equally likely. Furthermore, the direct electrochemical oxidation of carbon monoxide only slightly influences the anode performance. The concentration gradients in the current collector are larger than inside the electrode for gases not in equilibrium when entering the current collector; this is an effect caused by the shift reaction inside the electrode. However, if the gas compositions correspond to equilibrium at the current collector, the gas composition profiles become almost uniform. The disparities of the partial pressure dependency found in earlier experiments may be explained if the inlet gas composition is assumed to be the one obtained directly after humidification and not in equilibrium, as generally assumed.

  • 239.
    Sparr, Mari
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Experimental Studies of the Direct Oxidation of Carbon Monoxide in a Small Molten Carbonate Fuel CellManuscript (Other academic)
  • 240.
    Sparr, Mari
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sylwan, Christpher
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Kivisaari, Timo
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Fillman, Benny
    KTH, Superseded Departments, Chemical Engineering and Technology.
    A stack model for MCFC system studies for process simulationsManuscript (preprint) (Other academic)
  • 241.
    Svens, Pontus
    et al.
    Scania CV AB, Sweden.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lithium-Ion Battery Cell Cycling and Usage Analysis in a Heavy-Duty Truck Field Study2015In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, no 5, p. 4513-4528Article in journal (Refereed)
    Abstract [en]

    This paper presents results from a field test performed on commercial power-optimized lithium-ion battery cells cycled on three heavy-duty trucks. The goal with this study was to age battery cells in a hybrid electric vehicle (HEV) environment and find suitable methods for identifying cell ageing. The battery cells were cycled on in-house developed equipment intended for testing on conventional vehicles by emulating an HEV environment. A hybrid strategy that allows battery usage to vary within certain limits depending on driving patterns was used. This concept allows unobtrusive and low-cost testing of battery cells under realistic conditions. Each truck was equipped with one cell cycling equipment and two battery cells. One cell per vehicle was cycled during the test period while a reference cell on each vehicle experienced the same environmental conditions without being cycled. Differential voltage analysis and electrochemical impedance spectroscopy were used to identify ageing of the tested battery cells. Analysis of driving patterns and battery usage was performed from collected vehicle data and battery cell data.

  • 242.
    Svens, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Eriksson, Rickard
    Uppsala University.
    Hansson, Jörgen
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Gustafson, Torbjörn
    Uppsala University.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Analysis of ageing of commercial composite metal oxide: Li4Ti5O12 battery cellsManuscript (preprint) (Other academic)
    Abstract [en]

    Commercial battery cells with Li4Ti5O12 negative electrode and composite metal oxidepositive electrode have been analyzed with respect to ageing mechanisms. Electrochemical impedancespectroscopy (EIS), differential capacity analysis (dQ/dV), differential voltage analysis (dV/dQ) andscanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) were used to identifydifferent ageing mechanisms such as lithium inventory loss, loss of active electrode material andsurface film growth. The active material of the positive electrode was also examined by X-raydiffraction (XRD). Ageing mechanisms were studied for both calendar-aged and cycle-aged cells. Datafrom half cells prepared from post mortem harvested electrode material, using lithium foil as negativeelectrode and pouch material as encapsulation, were used as reference to full cell data. Electrochemicalanalysis of full and half cells combined with material analysis showed to be a powerful method toidentify ageing mechanisms in this type of commercial cells. The calendar-aged cell showedinsignificant ageing while the cycle-aged cell showed noticeable loss of positive electrode activematerial and loss of cyclable lithium, but only minor loss of negative electrode active material. Theresults imply that Li4Ti5O12 negative electrode material is a good alternative to other materials if highenergy density is not the primary goal.

  • 243.
    Svens, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. Scania CV AB, Sweden .
    Eriksson, Rickard
    Hansson, Jörgen
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Gustafsson, Torbjörn
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Analysis of aging of commercial composite metal oxide - Li 4Ti5O12 battery cells2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 270, p. 131-141Article in journal (Refereed)
    Abstract [en]

    Commercial battery cells with Li4Ti5O12 negative electrode and composite metal oxide positive electrode have been analyzed with respect to aging mechanisms. Electrochemical impedance spectroscopy (EIS), differential capacity analysis (dQ/dV), differential voltage analysis (dV/dQ) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) were used to identify different ageing mechanisms such as lithium inventory loss, loss of active electrode material and surface film growth. The active material of the positive electrode was also examined by X-ray diffraction (XRD). Aging mechanisms were studied for both calendar-aged and cycle-aged cells. Data from half cells prepared from post mortem harvested electrode material, using lithium foil as negative electrode and pouch material as encapsulation, were used as reference to full cell data. Electrochemical analysis of full and half cells combined with material analysis showed to be a powerful method to identify aging mechanisms in this type of commercial cells. The calendar-aged cell showed insignificant aging while the cycle-aged cell showed noticeable loss of positive electrode active material and loss of cyclable lithium, but only minor loss of negative electrode active material. The results imply that Li4Ti5O12 negative electrode material is a good alternative to other materials if high energy density is not the primary goal.

  • 244.
    Svens, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hellqvist Kjell, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Tengstedt, Carl
    Flodberg, Göran
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Li-Ion Pouch Cells for Vehicle Applications-Studies of Water Transmission and Packing Materials2013In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 6, no 1, p. 400-410Article in journal (Refereed)
    Abstract [en]

    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.

  • 245.
    Svens, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindström, Johan
    Scania CV AB, Södertälje, Sweden.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    HEV lithium-ion battery testing and driving cycle analysis in a heavy-duty truck field study2012In: ECS Transactions: Volume 41, Issue 32, 2012, 2012, p. 12-26Conference paper (Refereed)
    Abstract [en]

    This paper presents early results from an ongoing field test of HEV batteries on heavy-duty trucks. The presented results focus on the parameters that can affect ageing, such as SOC and power. The goal with this study is to correlate battery ageing to battery usage. Commercial LMO/LTO lithium-ion battery cells were tested onboard four Scania trucks. The test equipment was designed for this type of HEV battery testing on conventional vehicles by emulating an HEV environment. This concept allows unobtrusive and low cost testing of battery cells under realistic conditions. Each truck is equipped with test equipment containing one cycled battery cell and one calendar aged cell. The hybrid strategy used in this test allows battery power and SOC to vary depending on drive pattern within certain limits. Battery capacity and resistance is measured periodically and this makes it possible to receive information about battery ageing without bringing the cells to the lab.

  • 246.
    Svens, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindström, Johan
    Scania CV AB, Södertälje, Sweden.
    Gelin, Olle
    Scania CV AB, Södertälje, Sweden.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Novel Field Test Equipment for Lithium-Ion Batteries in Hybrid Electrical Vehicle Applications2011In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 4, no 5, p. 741-757Article in journal (Refereed)
    Abstract [en]

    Lifetime testing of batteries for hybrid-electrical vehicles (HEV) is usually performed in the lab, either at the cell, module or battery pack level. Complementary field tests of battery packs in vehicles are also often performed. There are, however, difficulties related to field testing of battery-packs. Some examples are cost issues and the complexity of continuously collecting battery performance data, such as capacity fade and impedance increase. In this paper, a novel field test equipment designed primarily for lithium-ion battery cell testing is presented. This equipment is intended to be used on conventional vehicles, not hybrid vehicles, as a cheaper and faster field testing method for batteries, compared to full scale HEV testing. The equipment emulates an HEV environment for the tested battery cell by using real time vehicle sensor information and the existing starter battery as load and source. In addition to the emulated battery cycling, periodical capacity and pulse testing capability are implemented as well. This paper begins with presenting some background information about hybrid electrical vehicles and describing the limitations with today's HEV battery testing. Furthermore, the functionality of the test equipment is described in detail and, finally, results from verification of the equipment are presented and discussed.

  • 247.
    Tennakoon, T. M. T. N.
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Bergman, Bill
    KTH, School of Industrial Engineering and Management (ITM).
    Performance of LiCoO2 cathodes, prepared using the Pechini method, in molten carbonate fuel cells1997In: Journal of the Electrochemical Society, Vol. 144, no 7, p. 2296-2301Article in journal (Refereed)
    Abstract [en]

    The Pechini method has successfully been used to fabricate a high-purity, ultrafine, homogeneous LiCoO2 powder. The powder has been used to cast tapes together with a plastic pore former. Sintered tapes show a bimodal pore size distribution comparable to that of state-of-the-art NiO cathodes and a homogeneous distribution of the pores throughout the tape. It is also shown that total porosity can be changed while retaining approximately the same pore size distribution using different sintering temperatures. Cell characterization, in a 3 cm2 lab cell, was performed on three cathodes sintered at 850, 900, and 950°C with total porosity ranging from 57 to 69%. It is concluded that (i) the selected chemical powder preparation technique provides pure, stable LiCoO2 with high surface area and high electrical conductivity and (ii) the cathode sintered at 900°C possesses a compromise of both phase purity, maximum possible porosity, and particle size, and hence gives a cathode polarization of 88 mV for 160 mA/cm2 at 650°C under optimum electrolyte content, which is comparable to state-of-the-art lithiated NiO. However, the voltage loss due to the interface resistance between current collector and electrode is on the order of 100 mV, which leads to a less advantageous total cathode performance.

  • 248.
    Tingelöf, Thomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Hedström, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Holmström, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    The influence of CO2, CO and air bleed on the current distribution of a polymer electrolyte fuel cell2008In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, no 33, p. 2064-2072Article in journal (Refereed)
    Abstract [en]

    The influence of CO2, CO and air bleed on current distribution was studied during transient operation, and the dynamic response of the fuel cell was evaluated. CO causes significant changes in the current distribution in a polymer electrolyte fuel cell. The current distribution reaches steady state after approximately 60 min following addition of 10 ppm CO to the anode fuel stream. Air bleed may recover the uneven current distribution caused by CO and also the drop in cell voltage due to CO and CO2 poisoning. The recovery of cell performance during air bleed occurs evenly over the electrode surface even when the O-2 partial pressure is far too low to fully recover the CO poisoning. The O-2 supplied to the anode reacts on the anode catalyst and no O-2 was measured at the cell outlet for air bleed levels up to 2.5%.

  • 249.
    Varini, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Campana, Pietro Elia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes. Malardalen Univ, Sch Business Soc & Engn, Box 883, SE-72123 Vasteras, Sweden..
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    A semi-empirical, electrochemistry-based model for Li-ion battery performance prediction over lifetime2019In: Journal of Energy Storage, E-ISSN 2352-152X, Vol. 25, article id UNSP 100819Article in journal (Refereed)
    Abstract [en]

    Predicting the performance of Li-ion batteries over lifetime is necessary for design and optimal operation of integrated energy systems, as electric vehicles and energy grids. For prediction purposes, several models have been suggested in the literature, with different levels of complexity and predictability. In particular, electrochemical models suffer of high computational costs, while empirical models are deprived of physical meaning. In the present work, a semi-empirical model is suggested, holding the computational efficiency of empirical approaches (low number of fitting parameters, low-order algebraic equations), while providing insights on the processes occurring in the battery during operation. The proposed model is successfully validated on experimental battery cycles: specifically, in conditions of capacity fade > 20%, and dynamic cycling at different temperatures. A comparable performance to up-to-date empirical models is achieved both in terms of computational time, and correlation coefficient R-2. In addition, analyzing the evolution of fitting parameters as a function of cycle number allows to identify the limiting processes in the overall battery degradation for all the protocols considered. The model suggested is thus suitable for implementation in system modelling, and it can be employed as an informative tool for improved design and operational strategies.

  • 250.
    Vernersson, Thomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lafitte, B.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Jannasch, P.
    A sulfophenylated polysulfone as the DMFC electrolyte membrane - an evaluation of methanol permeability and cell performance2006In: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 6, no 5, p. 340-346Article in journal (Refereed)
    Abstract [en]

    A sulfophenylated polysulfone (PSU-sph), carrying 0.8 sulfonic acid units per repeating unit of the polymer, is evaluated as a membrane electrolyte for DMFC applications. The liquid uptake, methanol transport characteristics, electrolyte conductivity, and fuel cell performance are investigated. The methanol transport and DMFC performance results are compared to those of Nafion(R) 117. The PSU-sph membrane investigated shows superior qualities with regard to methanol crossover, with a methanol permeability of approximately 25% compared to that of Nafion(R). The conductivity measured to be 15% compared to that of Nafion(R). However, this could not fully account for the internal resistance of the cell, implying that the contact resistance between the electrodes and electrolyte is higher when PSU-sph is used, probably because the electrodes are developed for use with Nafion(R) membranes. The stability of the PSU-sph membrane seems promising, with very low degradation observed over a period of 72 hours. It was concluded that although the mass transport properties of the PSU-sph membrane sample investigated were superior, it could not match the performance of Nafion(R) 117 in a DMFC application. However, a higher degree of sulfonation may have a significant positive effect on cell performance. The results also showed that a fully intergrated MEA is needed to fully assess new membrane materials.

23456 201 - 250 of 297
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