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  • 51.
    Ekström, Henrik
    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.
    A model for predicting capacity fade due to SEI formation in a commercial graphite/LiFePO4 cell2015In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 162, no 6, p. A1003-A1007Article in journal (Refereed)
    Abstract [en]

    An aging model for a negative graphite electrode in a lithium-ion battery, for moderate currents up to 1C, is derived and fitted to capacity fade experimental data. The predictive capabilities of the model, using only four fitted parameters, are demonstrated at both 25°C and 45°C. The model is based on a linear combination of two current contributions: one stemming from parts of the graphite particles covered by an intact microporous solid-electrolyte-interface (SEI) layer, and one contribution from parts of the particles were the SEI layer has cracked due to graphite expansion. Mixed kinetic and transport control is used to describe the electrode kinetics.

  • 52.
    Ekström, Henrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wickman, Björn
    Chalmers tekniska högskola, Göteborg.
    Gustavsson, Marie
    Chalmers tekniska högskola, Göteborg.
    Hanarp, Per
    Chalmers tekniska högskola, Göteborg.
    Eurenius, Lisa
    Chalmers tekniska högskola, Göteborg.
    Olsson, Eva
    Chalmers tekniska högskola, Göteborg.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Nanometer-thick films of titanium oxide acting as electrolyte in the polymer electrolyte fuel cell2007In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, no 12, p. 4239-4245Article in journal (Refereed)
    Abstract [en]

    0-18nm-thick titanium, zirconium and tantalum oxide films are thermally evaporated on Nation 117 membranes, and used as thin spacer electrolyte layers between the Nation and a 3 nm Pt catalyst film. Electrochemical characterisation of the films in terms of oxygen reduction activity, high frequency impedance and cyclic voltammetry in nitrogen is performed in a fuel cell at 80 degrees C and full humidification. Titanium oxide films with thicknesses up to 18 nm are shown to conduct protons, whereas zirconium oxide and tantalum oxide block proton transport already at a thickness of 1.5 nm. The performance for oxygen reduction is higher for a bi-layered film of 3 nm platinum on 1.5 or 18 nm titanium oxide, than for a pure 3 nm platinum film with no spacer layer. The improvement in oxygen reduction performance is ascribed to a higher active surface area of platinum, i.e. no beneficial effect of combining platinum with zirconium, tantalum or titanium oxides on the intrinsic oxygen reduction activity is seen. The results suggest that TiO2 may be used as electrolyte in fuel cell electrodes, and that low-temperature proton exchange fuel cells could be possible using TiO2 as electrolyte.

  • 53.
    Elger, Ragna
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Modelling and experimental validation of the electrochemical behaviour of a li-ion battery during repetitive pulses of charge and discharge2004Conference paper (Refereed)
    Abstract [en]

    In this study, a mathematical model describing the electrochemical and thermal behaviour of a cylindrical lithium-ion battery during high rate discharge and charge using a pulse typical for hybrid electric vehicles (HEV) is validated against experimental data. Experiments on the battery were performed in various constant temperature environments during a repeated pulse using high rate charge and discharge. The results show that the voltage losses increase as the temperature is lowered. The measurements show that as a good approximation, the surface temperature during the pulses can be assumed constant. The open circuit potential of LiNi0.8Co0.15Al0.05 was measured using GITT-experiments. The temperature dependence of the open circuit potential of LiNi0.8Co0.15Al0.05 was shown to be negligible. The experimental data will be used to validate the battery model. Some of the model parameters have yet to be fitted to the experimental results before a good agreement between experimental and model results is obtained.

  • 54. Enback, S.
    et al.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Experimentally validated model for CO oxidation on PtRu/C in a porous PEFC electrode2005In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 152, no 1, p. A23-A31Article in journal (Refereed)
    Abstract [en]

    Carbon monoxide oxidation in a porous polymer electrolyte fuel cell (PEFC) electrode with PtRu/C catalyst was studied with steady-state polarization curves and open- circuit decay measurements. The Tafel slope was about 210 mV/decade and the reaction order for CO was about 0.45 at 0.4 V vs. RHE. This experimental behavior is explained with a mathematical model with CO adsorbing on Pt and water adsorbing on Ru. Kinetic parameters are determined from a fitting of the model to both the steady-state and the transient measurements. A single rate-determining step cannot account for the polarization curves over the whole potential range. At mid-range potentials the oxidation step is rate-determining but at lower potentials the water adsorption might be rate-determining. The open- circuit decay measurements gave noise-free measurements and confirmed the accuracy of the steady-state measurements. The obtained model for CO oxidation where the coverage of COads on Pt is determined can be used together with a model for H-2 oxidation.

  • 55.
    Eric, Jacques
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Kjell, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Lindbergh, Göran
    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.
    Impact of the mechanical loading on the electrochemical capacity of carbon fibres for use in energy storage composite materials2011Conference paper (Other academic)
    Abstract [en]

    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.

  • 56.
    Eriksson, Björn
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Grimler, Henrik
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Carlson, Annika
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Ekström, Henrik
    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.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Quantifying water transport in anion exchange membrane fuel cells2019In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 44, no 10, p. 4930-4939Article in journal (Refereed)
    Abstract [en]

    Sufficient water transport through the membrane is necessary for a well-performing anion exchange membrane fuel cell (AEMFC). In this study, the water flux through a membrane electrode assembly (MEA), using a Tokuyama A201 membrane, is quantified using humidity sensors at the in- and outlet on both sides of the MEA. Experiments performed in humidified inert gas at both sides of the MEA or with liquid water at one side shows that the aggregation state of water has a large impact on the transport properties. The water fluxes are shown to be approximately three times larger for a membrane in contact with liquid water compared to vaporous. Further, the flux during fuel cell operation is investigated and shows that the transport rate of water in the membrane is affected by an applied current. The water vapor content increases on both the anode and cathode side of the AEMFC for all investigated current densities. Through modeling, an apparent water drag coefficient is determined to −0.64, indicating that the current-induced transport of water occurs in the opposite direction to the transport of hydroxide ions. These results implicate that flooding, on one or both electrodes, is a larger concern than dry-out in an AEMFC.

  • 57.
    Eriksson, Björn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Jaouen, F.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    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.
    Degradation and lifetime evaluation of Fe-N-C based catalyst in PEMFC2015In: Proceedings of the 6th European Fuel Cell - Piero Lunghi Conference, EFC 2015, ENEA , 2015, p. 223-224Conference paper (Refereed)
    Abstract [en]

    The restricted lifetime of Fe-N-C based catalysts is often assumed to be connected to the operating temperature. This study will investigate how the cell performance, electrode structure and composition vary over time, at different cell temperatures. At lower temperature, one may expect an increase in radical's stability, but a decrease in reactivity. Results show that the electrode degenerates over time, and that the electrochemical performance decay is similar for 40, 60, and 80° C. However, the loss of active sites is higher at higher temperature. This suggests that indirect production of radicals via H2O2 production during ORR is higher at higher temperatures and is a key degradation mechanism for this Fe-N-C catalyst.

  • 58.
    Eriksson, Björn
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Montserrat-Sisó, Gerard
    Chalmers University of Technology.
    Brown, Rosemary
    Chalmers University of Technology.
    Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Wickman, Björn
    Chalmers University of Technology.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Evaluation of rare earth metal alloy catalysts for the oxygen reduction reaction in proton exchange membrane fuel cellsManuscript (preprint) (Other academic)
  • 59. Eriksson, T.
    et al.
    Hjelm, A. K.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Gustafsson, T.
    Kinetic study of LiMn2O4 cathodes by in situ XRD with constant-current cycling and potential stepping2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 9, p. A1164-A1170Article in journal (Refereed)
    Abstract [en]

    The structure and kinetics of LiMn2O4 electrodes have been investigated by in situ X-ray diffraction (XRD) measurements using a novel three-electrode in situ XRD cell, where the reference electrode is sited on the reverse side of the working electrode to facilitate accurate determination of the electrode potential. The use of ballmilling during electrode preparation resulted in a high level of utilization at high charge/discharge rates of LiMn2O4-based electrodes in both structural and electrochemical studies. No evidence of Li concentration gradients in the solid material could be observed from XRD, thus excluding solid-phase diffusion and also phase boundary movement, as described by Fick's law, as the rate-limiting step.

  • 60.
    Fillman, Benny
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sylwan, Christopher
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sparr, Mari
    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.
    Influence of process parameters on the system efficiency of anatural gas or a gasified biomass fueled MCFC systemManuscript (preprint) (Other academic)
  • 61.
    Fontes, Eduardo
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lagergren, Carina
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Simonsson, Daniel
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Influence of gas phase mass transfer limitations on molten carbonate fuel cell cathodes1997In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 27, no 10, p. 1149-1156Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to elucidate to what extent mass transfer limitations in the gas phase affect the performance of porous molten carbonate fuel cell cathodes. Experimental data from porous nickel oxide cathodes and calculated data are presented. One and two-dimensional models for the current collector and electrode region have been used. Shielding effects of the current collector are taken into account. The mass balance in the gas phase is taken into account by using the Stefan-Maxwell equation. For standard gas composition and normal operating current density, the effect of gas-phase diffusion is small. The diffusion in the gaseous phase must be considered at operation at higher current densities. For low oxygen partial pressures, the influence of mass transfer limitations is large, even at low current densities. To eliminate the influence of conversion on polarization curves recorded on laboratory cell units, measurements should always be performed with a five to tenfold stoichiometric excess of oxygen. Two-dimensional calculations show rather large concentration gradients in directions parallel to the current collector. However, the influence on electrode performance is still small, which is explained by the fact that most of the current is produced close to the electrolyte matrix.

  • 62. Georen, P.
    et al.
    Adebahr, J.
    Jacobsson, P.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Concentration polarization of a polymer electrolyte2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 8, p. A1015-A1019Article in journal (Refereed)
    Abstract [en]

    In this study, the salt concentration in a concentrated binary polymer electrolyte was measured in situ by means of confocal Raman spectroscopy during galvanostatic polarization experiments. The electrolyte studied was 0.8 M lithium bis(trifluoromethanesulfone)imide in a copolymer of ethylene- and propylene oxide at 25degreesC. Recent work with a transport model and characterization of the transport properties, for the same electrolyte, was verified with the spectroscopic results of this study. A good agreement between modeled and measured results was found. The spectroscopic method suited well for these studies. The possibilities of using a transport model are briefly demonstrated and discussed.

  • 63. Georen, P.
    et al.
    Hjelm, A. K.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundqvist, A.
    An electrochemical impedance spectroscopy method applied to porous LiMn2O4 and metal hydride battery electrodes2003In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, no 2, p. A234-A241Article in journal (Refereed)
    Abstract [en]

    An electrochemical impedance spectroscopy method utilizing the signals from reference electrodes positioned in front of and behind a porous electrode is investigated. The basis for the method is illustrated theoretically, and limiting values under different assumptions are presented. The method was applied to a porous metal hydride and a LiMn2O4 battery electrode. It was concluded that the method facilitates the separation of local impedance effects from the effects of the potential distribution in the porous electrode. Consequently, a more accurate determination of local kinetic parameters and the effective conductivity in the pore electrolyte could be obtained.

  • 64. Georen, P.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Characterisation and modelling of the transport properties in lithium battery polymer electrolytes2001In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 47, no 4, p. 577-587Article in journal (Refereed)
    Abstract [en]

    The ionic transport properties of solid polymer electrolytes can limit the performance of lithium batteries and are difficult to characterise. Few characterisation methods are available and the reported results show large discrepancies and the methods do not take variations of the properties with salt concentration into account although such are typical for polymer electrolytes. In this study, numerical macroscopic modelling, using the concentrated solution theory, was employed to determine the transport properties and thermodynamic activity factor, allowing concentration-dependent parameters. A copolymer of ethylene oxide and propylene oxide with 0.11 - 2 M LiTFSI was characterised at 25 degreesC using chronopotentiometry and concentration cell experiments. The determined ionic conductivity, kappa, apparent salt diffusion coefficient, D-s and cationic transport number, t(+)(0), were in line with previous results and kappa was also verified using electrochemical impedance spectroscopy. t(+)(0) values below 0.25 were measured, showing a decrease with increasing salt concentration. It was found that it was important to take into account the concentration dependence of the transport properties as well as the ionic interaction and the activity factor of the salt. The study resulted in a transport model well suited for the system that can easily be used to simulate the electrolyte behaviour for any current.

  • 65. Georen, P.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    On the use of voltammetric methods to determine electrochemical stability limits for lithium battery electrolytes2003In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 124, no 1, p. 213-220Article in journal (Refereed)
    Abstract [en]

    In previous studies a novel amphiphilic co-polymer was developed for use in lithium-ion batteries. In order to evaluate the electrochemical stability of that electrolyte and compare it with others, a voltammetric method was applied on a set of electrolytes with different salts, solvents and polymers. However, initially the voltammetric methodology was studied. Platinum was found to be the most suited electrode material, experiencing no significant interfering reactions and a proper diffusion-controlled kinetic behaviour when sweep rate was varied. Furthermore, the influence on the voltammograms of adding water traces to the electrolytes was studied. It could be established that the oxidation peak around 3.8 V versus Li was related to water reactions. It was concluded that quantitative voltage values of the stability limits were difficult to assess using voltammetry. On the other hand, the method seemed well suited for comparison of electrolytes and to investigate the influences of electrolyte components on the stability. The voltammetric results varied little between the different electrolytes evaluated and the anodic and cathodic limits, as defined here, were in the range of I and 4.5 V vs. Li, respectively. Although the novel polymer did not affect the stability limit significantly it seemed to promote the breakdown reaction rate in all electrolytes tested. Furthermore, the use of LiTFSI salt reduced the stability window.

  • 66.
    Georen, Peter
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Characterisation and modelling of the transport properties in lithium battery gel electrolytes - Part I. The binary electrolyte PC/LiClO42004In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 49, no 21, p. 3497-3505Article in journal (Refereed)
    Abstract [en]

    A recent development trend for rechargeable lithium batteries is the use of ternary gel electrolytes. The main advantage of the gels is the mechanical rigidity, which improves as the polymer content is increased. However, the transport properties deteriorate with increasing polymer amount. This dualistic optimisation problem has caused an increased interest in understanding the transport processes in gels, however no full characterisation or modelling study could be found in the literature. In this paper, which is the first part of a study of the transport in the ternary gel system PMMA/PC/LiClO4, the liquid electrolyte PC/LiClO4 is characterised and modelled for concentrations between 0.1 and 2 M according to a previously employed methodology, based on electrochemical measurements. A model using concentration dependent interaction parameters proved to describe the results in the whole concentration region well. The cationic transport number and salt diffusivity were determined to be approximately 0.3 and 1e-10m(2)/s, respectively. The mean ionic activity factor variations prove to be substantial. Furthermore, it was demonstrated that the inter-ionic friction was important to consider at concentrations above 1 M. The fundamental friction parameters determined in this part will be used in the following part of the study to describe the friction between ions and solvent.

  • 67.
    Giordano, Giuseppe
    et al.
    Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden..
    Klass, Verena
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Behm, Mårten
    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.
    Sjöberg, Jonas
    Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden..
    Model-Based Lithium-Ion Battery Resistance Estimation From Electric Vehicle Operating Data2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 5, p. 3720-3728Article in journal (Refereed)
    Abstract [en]

    State-of-health estimates of batteries are essential for onboard electric vehicles in order to provide safe, reliable, and cost-effective battery operation. This paper suggests a method to estimate the 10-s discharge resistance, which is an established battery figure of merit from laboratory testing, without performing the laboratory test. Instead, a state-of-health estimate of batteries is obtained using data directly from their operational use, e.g., onboard electric vehicles. It is shown that simple dynamical battery models, based on a current input and a voltage output, with model parameters dependent on temperature and state of charge, can be derived using AutoRegressive with eXogenous input models, whose order can be adjusted to describe the complex battery behavior. Then, the 10-s discharge resistance can be conveniently computed from the identified model parameters. Moreover, the uncertainty of the estimated resistance values is provided by the method. The suggested method is validated with usage data from emulated electric vehicle operation of an automotive lithium-ion battery cell. The resistance values are estimated accurately for a state-of-charge and temperature range spanning typical electric vehicle operating conditions. The identification of the model parameters and the resistance computation are very fast, rendering the method suitable for onboard application.

  • 68.
    Gode, Peter
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Jannasch, Patric
    Polymer Science and Engineering, Lund University.
    Johansson, M.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Karlsson, Lina E.
    Polymer Science and Engineering, Lund University.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Sandquist, D.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    A novel sulfonated dendritic polymer as the acidic component in proton conducting membranes2006In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, no 7-8, p. 787-794Article in journal (Refereed)
    Abstract [en]

    The present study involves the synthesis of sulfonated poly(3-ethyl-3-(hydroxymethyl)oxetane), sPTMPO, by end-capping the hydroxy-groups in the PTMPO with 1,4-butane sultone. A series of the polymer with different degrees of substitution was investigated. Furthermore, the subsequent use of the sulfonated PTMPO as the acidic component in proton conducting membranes was explored. The membranes were prepared by either a) mixing the partly sulfonated PTMPO with hexamethoxymethyl melamine (HMMM) to form cross-links by ether formation between the methylol groups on HMMM and the remaining hydroxyl groups on the hyperbranched polyether or b) using the sulfonated polyether in conjunction with a pyridine functionalised polysulfone, PSU-pyridine, to produce acid-base blend membranes. Membrane properties such as proton conductivity, water uptake and mechanical properties are discussed.

  • 69.
    Gode, Peter
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Ihonen, Jari
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Strandroth, A.
    Ångström Laboratory, Department of Materials Chemistry, Uppsala University.
    Ericson, Hanna
    Department of Experimental Physics, Chalmers University of Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Paronen, Mikael
    Laboratory of Polymer Chemistry, University of Helsinki.
    Sundholm, Franciska
    Laboratory of Polymer Chemistry, University of Helsinki.
    Sundholm, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Walsby, Nadia
    Department of Material Science, Cranfield University, Shrivenham, United Kingdom.
    Membrane Durability in a PEM Fuel Cell Studied Using PVDF Based Radiation Grafted Membranes2003In: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 3, no 1-2, p. 21-27Article in journal (Refereed)
    Abstract [en]

    The durability testing of membranes for use in a polymer electrolyte fuel cell (PEFC) has been studied in situ by a combination of galvanostatic steady-state and impedance measurements. The PEFC measurements, which are time consuming, have been compared to fast ex situ testing in 3% H2O 2 solution. For the direct assessment of membrane degradation micro-Raman spectroscopy and determination of ion exchange capacity (IEC) have been used. PVDF based membranes, radiation grafted with styrene and sulfonated, were used as model membranes. By using low degrees of grafting, below about 35%, the durability of this type of membrane can be increased. Degradation in the fuel cell was found to be highly localised. It was found that in situ measurements in the PEFC alone are not sufficient. Measurement of the cell resistance via impedance is not always a reliable indicator of changes in membrane resistance because other resistance changes in the cell can easily interfere and cannot be separated from those caused by the membrane. Micro-Raman is an ideal complementary method to in situ testing, but it is time consuming. For fast pre-screening of membrane durability mass loss measurements during exposure to 3% H2O2 solution combined with the determination of changes in the IEC can be performed.

  • 70.
    Gode, Peter
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Jaouen, Frederic
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sundholm, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Influence of the composition on the structure and electrochemical characteristics of the PEFC cathode2003In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 48, no 28, p. 4175-4187Article in journal (Refereed)
    Abstract [en]

    The influence the composition of the cathode has on its structure and electrochemical performance was investigated for a Nafion content spanning from 10 to 70 wt.%. The cathodes were formed on a Nafion membrane by the spray method and using 20 wt.% Pt on Vulcan (E-TEK). Materials characterisation (SEM, STEM, gas and mercury porosimetry, electron conductivity) and electrochemical characterisation (steady-state polarisation curve, impedance spectroscopy in O-2 and current-pulse measurements in N-2) were performed. The impedance spectra were analysed using our dynamic agglomerate model. The results indicate that the agglomerate model is valid until a Nafion content of about 45 wt.%. Pt/C and Nation are homogeneously mixed for any composition and no Nafion film was observed. The cathodes containing 36-43 wt.% Nation display a single or double Tafel slope behaviour ascribed to diffusion limitations in the agglomerates. At larger Nation content, the agglomerate model can describe the curves only by assuming a diffusion coefficient 3-4 decades smaller than that of gases. At such compositions, the porosity was only 10%. These results were interpreted as a blocking of the pores and a non-percolating pore system for too large Nafion contents.

  • 71.
    Gode, Peter
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sundholm, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    In-situ measurements of gas permeability in fuel cell membranes using a cylindrical microelectrode2002In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 518, no 2, p. 115-122Article in journal (Refereed)
    Abstract [en]

    A new method to study permeation of gases in proton conducting membranes using a cylindrical microelectrode is presented. The focus of this work was to develop an in-situ method to study transport properties of hydrogen and oxygen close to real fuel cell operating conditions. The gas permeability is strongly affected by the change of water content in the membrane and it is therefore of advantage that, by using this method, measurements can be carried out over a wide range of relative humidities. The numerical method makes it possible to separate the diffusion coefficient and the concentration of dissolved gas in the membrane and also allows kinetic limitations to be taken into account. Chronoamperometric measurements on Nafion(R) 117 were successfully evaluated numerically. Experiments at temperatures of 25 and 60 degreesC with respect to oxygen permeation and at 60 degreesC for hydrogen permeation at relative humidities in the range 30-94% are presented. The reproducibility of data was excellent when measuring with different microelectrodes, on the same membrane sample, but differed when measuring on different samples. In general, the permeability increases with increasing temperature and relative humidity.

  • 72.
    Gomez, Yasna Acevedo
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Oyarce, Alejandro
    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.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Ammonia contamination of a proton exchange membrane fuel cell2018In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, no 3, p. F189-F197Article in journal (Refereed)
    Abstract [en]

    Reformate hydrogen from biogas is an attractive fuel alternative for energy conversion in PEM fuel cells. However, in the reformate traces of ammonia may be found, e.g. if the biogas is produced from agricultural resources. In this investigation the effect of ammonia in the fuel gas, on each part of the fuel cell, is studied by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), symmetrical hydrogen cell (H2|H2)- and real fuel cell operation. A considerable degradation in performance is observed by introducing 200 ppm ammonia. The results show that ammonia not only affects the polymer electrolyte membrane but also the oxygen reduction reaction (ORR) and catalyst ionomer in both electrodes, whereas the hydrogen oxidation reaction (HOR) is the worst affected. In the short-term, the performance is reversible if running the cell on neat hydrogen after ammonia exposure, but this does not apply for long-term exposure. A mitigation method with air bleed is tested but gives no improvement of the performance.

  • 73.
    Grimler, Henrik
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Carlson, Annika
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Ekström, Henrik
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. COMSOL.
    Lagergren, Carina
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology. 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.
    Lindbergh, Göran
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Determination of kinetic parameters for the oxygen reduction reaction on platinum in an AEMFCManuscript (preprint) (Other academic)
  • 74.
    Guan, Tingting
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Alvfors, Per
    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.
    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 system2014In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 130, p. 685-691Article in journal (Refereed)
    Abstract [en]

    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.

  • 75.
    Guccini, Valentina
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden.
    Carlson, Annika
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Yu, Shun
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden .
    Lindbergh, Göran
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology. 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.
    Salazar-Alvarez, German
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden .
    Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells2019In: Journal of Materials Chemistry A, ISSN 2050-7488Article in journal (Refereed)
    Abstract [en]

    The performance of thin carboxylated cellulose nanofiber-based (CNF) membranes as proton exchange membranes in fuel cells has been measured in situ as a function of CNF surface charge density (600 and 1550 μmol g−1), counterion (H+ or Na+), membrane thickness and fuel cell relative humidity (RH 55 to 95%). The structural evolution of the membranes as a function of RH, as measured by Small Angle X-ray Scattering, shows that water channels are formed only above 75% RH. The amount of absorbed water was shown to depend on the membrane surface charge and counter ions (H+ or Na+). The high affinity of CNF for water and the high aspect ratio of the nanofibers, together with a well-defined and homogenous membrane structure, ensures a proton conductivity exceeding 1 mS cm−1 at 30 °C between 65 and 95% RH. This is two orders of magnitude larger than previously reported values for cellulose materials and only one order of magnitude lower than Nafion 212. Moreover, the CNF membranes are characterized by a lower hydrogen crossover than Nafion, despite being ≈30% thinner. Thanks to their environmental compatibility and promising fuel cell performance the CNF membranes should be considered for new generation proton exchange membrane fuel cells.

  • 76.
    Gustavsson, John
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Hummelgård, Christine
    Institutionen för naturvetenskap, teknik och matematik, Mid Sweden University, Sundsvall, Sweden.
    Bäckström, Joakim
    Institutionen för naturvetenskap, teknik och matematik, Mid Sweden University, Sundsvall, Sweden.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Rahman, Seikh Mohammad Habibur
    Chalmers, Dept Chem & Biol Engn, Gothenburg, Sweden.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Eriksson, Sten
    Chalmers, Dept Chem & Biol Engn, Gothenburg, Sweden.
    Cornell, Ann
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    In-situ activated hydrogen evolution by molybdate addition to neutral and alkaline electrolytes2012In: Journal of Electrochemical Science and Engineering, ISSN 1847-9286, Vol. 2, no 3, p. 105-120Article in journal (Refereed)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron.

  • 77.
    Gustavsson, John
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hummelgård, Christine
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE 851 70 Sundsvall, Sweden.
    Bäckström, Joakim
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE 851 70 Sundsvall, Sweden.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rahman, Seikh Mohammed Habibur
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Eriksson, Sten
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden.
    Cornell, Ann
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    In-situ Activated Hydrogen Evolution by Molybdate Addition to Neutral and Alkaline ElectrolytesManuscript (preprint) (Other academic)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X‑ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X‑ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron‑molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron.

  • 78.
    Gustavsson, John
    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.
    Cornell, Ann
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    In-situ activation of hydrogen evolution in pH-neutral electrolytes by additions of multivalent cations2012In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, no 12, p. 9496-9503Article in journal (Refereed)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) in close to pH-neutral electrolytes can be achieved by addition of trivalent cations. This activation has been investigated using steady state polarization, electrochemical impedance spectroscopy (EIS) and chemical analysis of cathode films for yttrium. Several multivalent cations were included in this study, such as Al(III), Mg(II), Y(III), Sm(III), La(III) and Sc(III). In general the more acidic the metal ions the larger is the activation. Metal hydroxide films formed in the alkaline diffusion layer at the cathode surface can have a negative impact on the magnitude of this activation, and therefore complicate the interpretation of the results. The activation corresponds to a transport of metal ion complexes to the electrode surface and the reduction of bound ligand water to form hydrogen.

  • 79.
    Gustavsson, Marie
    et al.
    Chalmers tekniska högskola, Göteborg.
    Ekström, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hanarp, Per
    Chalmers tekniska högskola, Göteborg.
    Eurenius, Lisa
    Chalmers tekniska högskola, Göteborg.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Olsson, Eva
    Chalmers tekniska högskola, Göteborg.
    Kasemo, Bengt
    Chalmers tekniska högskola, Göteborg.
    Thin film Pt/TiO2 catalysts for the polymer electrolyte fuel cell2007In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 163, no 2, p. 671-678Article in journal (Refereed)
    Abstract [en]

    Thin film Pt/TiO2 catalysts are evaluated in a polymer electrolyte electrochemical cell. Individual thin films of Pt and TiO2, and bilayers of them, were deposited directly on Nafion membranes by thermal evaporation with varying deposition order and thickness (Pt loadings of 3-6 mu g cm(-2)). Structural and chemical characterization was performed by transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Oxygen reduction reaction (ORR) polarization plots show that the presence of a thin TiO2 layer between the platinum and the Nation increases the performance compared to a Pt film deposited directly on Nation. Based on the TEM analysis, we attribute this improvement to a better dispersion of Pt on TiO2 compared to on Nalion and in addition, substantial proton conduction through the thin Ti02 layer. It is also shown that deposition order and the film thickness affects the performance.

  • 80.
    Hagberg, Johan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Leijonmarck, Simon
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. Swerea KIMAB AB, Sweden.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    High Precision Coulometry of Commercial PAN-Based Carbon Fibers as Electrodes in Structural Batteries2016In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, no 8, p. A1790-A1797Article in journal (Refereed)
    Abstract [en]

    Carbon fibers have the combined mechanical and electrochemical properties needed to make them particularly well suited for usage as electrodes in a structural lithium-ion battery, a material that simultaneously works as a battery and a structural composite. Presented in this paper is an evaluation of commercial polyacrylonitrile-based carbon fibers in terms of capacity and coulombic efficiency, as well as a microstructural and surface evaluation. Some polyacrylonitrile based carbon fibers intercalate lithium ions, resulting in a similar capacity as state-of-the-art graphite based electrodes, presently the most commonly used negative electrode material. Using high precision coulometry, we found a capacity of around 250-350 mAh/g and a very high coulombic efficiency of over 99.9% after ten cycles, which is even higher than a commercial state-of-the art graphitic electrode evaluated as reference. The high coulombic efficiency is attributed to the very low surface area of the carbon fibers, resulting in a small and stable solid-electrolyte interface layer. A highly graphitized ultra high modulus carbon fiber was evaluated as well and, compared to the other fibers, less lithium was inserted (corresponding to approximately 150 mAh/g). We show that the use of carbon fibers as an electrode material in a structural composite battery is indeed viable.

  • 81.
    Hagberg, Johan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Maples, Henry A.
    Polymer and Composite Engineering (PaCE) Group, Institute of Materials Chemistry and Research, Faculty of Chemistry, University of Vienna, Währinger Straße 42, A-1090 Vienna, Austria .
    Alvim, Kayne S. P.
    Polymer and Composite Engineering (PaCE) Group, Institute of Materials Chemistry and Research, Faculty of Chemistry, University of Vienna, Währinger Straße 42, A-1090 Vienna, Austria .
    Xu, Johanna
    Polymeric Composite Materials, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-97187 Luleå, Sweden .
    Johannisson, Wilhelm
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Bismarck, Alexander
    Polymer and Composite Engineering (PaCE) Group, Institute of Materials Chemistry and Research, Faculty of Chemistry, University of Vienna, Währinger Straße 42, A-1090 Vienna, Austria ; Polymer and Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK .
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lithium iron phosphate coated carbon fiber electrodes for structural lithium ion batteries2018In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 162, p. 235-243Article in journal (Refereed)
    Abstract [en]

    A structural lithium ion battery is a material that can carry load and simultaneously be used to store electrical energy. We describe a path to manufacture structural positive electrodes via electrophoretic deposition (EPD) of LiFePO4 (LFP), carbon black and polyvinylidene fluoride (PVDF) onto carbon fibers. The carbon fibers act as load-bearers as well as current collectors. The quality of the coating was studied using scanning electron microscopy and energy dispersive X-ray spectroscopy. The active electrode material (LFP particles), conductive additive (carbon black) and binder (PVDF) were found to be well dispersed on the surface of the carbon fibers. Electrochemical characterization revealed a specific capacity of around 60–110 mAh g−1 with good rate performance and high coulombic efficiency. The cell was stable during cycling, with a capacity retention of around 0.5 after 1000 cycles, which indicates that the coating remained well adhered to the fibers. To investigate the adhesion of the coating, the carbon fibers were made into composite laminae in epoxy resin, and then tested using 3-point bending and double cantilever beam (DCB) tests. The former showed a small difference between coated and uncoated carbon fibers, suggesting good adhesion. The latter showed a critical strain energy release rate of ∼200–600 J m−2 for coated carbon fibers and ∼500 J m−2 for uncoated fibers, which also indicates good adhesion. This study shows that EPD can be used to produce viable structural positive electrodes.

  • 82. Hagberg, Johan
    et al.
    Morozov, Evgeny
    Furo, Istvan
    KTH, Superseded Departments (pre-2005), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, Superseded Departments (pre-2005), Physics.
    Lindbergh, Göran
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Inequality of Axial and Radial Diffusion of Inserted Lithium Ions in Carbon Fibres as Revealed by Pulsed-Field Gradient NMRManuscript (preprint) (Other academic)
    Abstract [en]

    Nuclear Magnetic Resonance (NMR) studies has characterized lithiated polyacrylonitrile-based carbon fibres. The local dynamics has been probed by spin-lattice and spin-spin relaxation measurements and long range motion (diffusion) by pulsed field gradient NMR. Differences in fibre orientation was investigated by axially and radially aligned samples. One single peak related to lithium insertion was observed around 12-25 ppm, increasing with lithium load. A small effect of fibre orientation was observed on the relaxation behavior. The diffusion though was found to be around three times higher in axial compared to radial direction of the carbon fibres. This is believed to be due to the microstructure, with oriented crystallites along the carbon fibres contributing more in the axial direction to the average measured diffusion. The diffusion coefficients varied from around 10-12 m2/s to 4·10-12 m2/s, increasing with lithium load.

  • 83.
    Hallberg, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Vernersson, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Thyboll Pettersson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Dvinskikh, Sergey V.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Electrokinetic transport of water and methanol in Nafion membranes as observed by NMR spectroscopy2010In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 55, no 10, p. 3542-3549Article in journal (Refereed)
    Abstract [en]
    Electrophoretic NMR (eNMR) and pulsed-field-gradient NMR (PFG-NMR) methods were used to study transport processes in situ and in a chemically resolved manner in the electrolyte of an experimental direct methanol fuel cell (DMFC) setup, constituted of several layers of Nation 117. The measurements were conducted at room temperature for membranes fully swollen by methanol-water mixtures over a wide concentration interval. The experimental setup and the experimental protocol for the eNMR experiments are discussed in detail. The magnitude of the water and methanol self-diffusion coefficients show a good agreement with previously published data while the ratio of the two self-diffusion coefficients may indicate an imperfect mixing of the two solvent molecules. On the molecular level, the drag of water and methanol molecules by protons is roughly of the same magnitude, with the drag of methanol molecules increasing with increasing methanol content. The electro-osmotic drag defined on mass-flow basis increased for methanol from a low level with increasing methanol concentration while that of water remained roughly constant. (C) 2010 Elsevier Ltd. All rights reserved.
  • 84.
    Harnden, Ross
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Peuvot, Kevin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Multifunctional Performance of Sodiated Carbon Fibers2018In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, no 13, p. B616-B622Article in journal (Refereed)
    Abstract [en]

    An investigation is conducted into the potential for sodiated PAN-based carbon fibers (CFs) to be used in multifunctional actuation, sensing, and energy harvesting. Axial CF expansion/contraction is measured during sodiation/desodiation using operando strain measurements. The reversible expansion/contraction is found to be 0.1% - which is lower than that of lithiated CFs. The axial sodiation expansion occurs in two well-defined stages, corresponding to the sloping and plateau regions of the galvanostatic cycling curve. The results indicate that the sloping region most likely corresponds to sodium insertion between graphitic sheets, while the plateau region corresponds to sodium insertion in micropores. A voltage-strain coupling is found for the CFs, with a maximum coupling factor of 0.15 +/- 0.01 V/unit strain, which could be used for strain sensing in multifunctional structures. This voltage-strain coupling is too small to be exploited for harvesting mechanical energy. The measured axial expansion is further used to estimate the capacity loss due to solid electrolyte interphase (SEI) formation, as well as capacity loss due to sodium trapped in the CF microstructure. The outcomes of this research suggest that sodiated CFs show some potential for use as actuators and sensors in future multifunctional structures, but that lithiated CFs show more promise.

  • 85.
    Hedström, Lars
    et al.
    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.
    Saxe, Maria
    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
    Rissanen, Markku
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Operating Experience and Results from 3310 hours of Operation of a Biogas-powered 5 kW SOFC System in GlashusEttManuscript (preprint) (Other academic)
  • 86.
    Hedström, Lars
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Tingelöf, Thomas
    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.
    Experimental results from a 5 kW PEM fuel cell stackoperated on simulated reformate from highly dilutedhydrocarbon fuels: Efficiency, dilution, fuel utilisation,CO poisoning and design criteria2009In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, no 34, p. 1508-1514Article in journal (Refereed)
    Abstract [en]

    The present article analyses the effects of dilute biogas on efficiency, fuel utilisation, dynamics, control strategy, and design criteria for a polymer electrolyte fuel cell (PEFC) system. The tested fuel compositions are exemplified by gas compositions that could be attained within various Swedish biofuel demonstration projects. Experimental data which can serve as a basis for design of PEFC biogas systems operating in load-following, or steady-state mode, are reported for a 5 kW PEFC stack.

  • 87.
    Hellqvist Kjell, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Jacques, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    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.
    PAN-based carbon fiber negative electrodes for structural lithium-ion batteries2011In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 12, p. A1455-A1460Article in journal (Refereed)
    Abstract [en]

    Several grades of commercially-available polyacrylonitrile (PAN)-based carbon fibers have been studied for structural lithium-ion batteries to understand how the sizing, different lithiation rates and number of fibers per tow affect the available reversible capacity, when used as both current collector and electrode, for use in structural batteries. The study shows that at moderate lithiation rates, 100 mA g-1, most of the carbon fibers display a reversible capacity close to or above 100 mAh g-1 after ten full cycles. For most of the fibers, removing the sizing increased the capacity to some extent. However, the main factor affecting the measured capacity was the lithiation rate. Decreasing the current by a tenth yielded an increase of capacity of around 100 for all the tested grades. From the measurements performed in this study it is evident that carbon fibers can be used as the active negative material and current collector in structural batteries. © 2011 The Electrochemical Society.

  • 88.
    Hellqvist Kjell, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Jacques, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    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.
    PAN-based carbon fibers for structural lithium-ion batteries2012In: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials, European Conference on Composite Materials, ECCM , 2012Conference paper (Refereed)
    Abstract [en]

    Structural batteries have the potential to become an integrated part of the device, functioning as both a structural element and as energy storage by combining electrochemical properties and mechanical properties in the same material. In addition, an increase of power and energy density on a system level could be achieved. The electrochemical properties of seven different commercially available PAN-based carbon fibers have been investigated as negative electrodes for structural lithium-ion batteries. All of the tested fibers showed some ability to intercalate lithium ions. The performance varied significantly between the different grades of fiber. Fibers with intermediate modulus showed the most promising results.

  • 89.
    Hellqvist Kjell, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Malmgren, Sara
    Ciosek, Katarzyna
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Edström, Kristina
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Comparing aging of graphite/LiFePO4 cells at 22 degrees C and 55 degrees C - Electrochemical and photoelectron spectroscopy studies2013In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 243, p. 290-298Article in journal (Refereed)
    Abstract [en]

    Accelerated aging at elevated temperature is commonly used to test lithium-ion battery lifetime, but the effect of an elevated temperature is still not well understood. If aging at elevated temperature would only be faster, but in all other respects equivalent to aging at ambient temperature, cells aged to end-of-life (EOL) at different temperatures would be very similar. The present study compares graphite/LiFePO4-based cells either cycle- or calendar-aged to EOL at 22 degrees C and 55 degrees C. Cells cycled at the two temperatures show differences in electrochemical impedance spectra as well as in X-ray photoelectron spectroscopy (XPS) spectra. These results show that lithium-ion cell aging is a complex set of processes. At elevated temperature, the aging is accelerated in process-specific ways. Furthermore, the XPS results of cycle-aged samples indicate increased deposition of oxygenated LiPF6 decomposition products in both the negative and positive electrode/electrolyte interfaces. The decomposition seems more pronounced at elevated temperature, and largely accelerated by cycling, which could contribute to the observed cell impedance increase.

  • 90.
    Hellqvist Kjell, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zavalis, Tommy
    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 characterization of lithium intercalation processes of PAN-based carbon fibers in a microelectrode system2013In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 160, no 9, p. A1473-A1481Article in journal (Refereed)
    Abstract [en]

    A full electrochemical investigation of the lithium intercalation processes in a commercially available PAN-based carbon fiber, Toho Tenax IMS65 (unsized and sized) primarily intended to be used in structural lithium-ion batteries, has been performed. In order to extract the electrochemical properties, a specially designed microelectrode system consisting of a single fiber working electrode, lithium-foil counter electrode and well-characterized battery materials were utilized. The properties, for 5 to 100% state-of-charge (SOC), were mainly determined from electrochemical impedance spectroscopy (EIS) measurements by fitting of a physics-based model, and electronic conductivity examination. The study shows excellent mass transport and kinetic properties, especially at high SOCs for this specific carbon fiber compared to other negative electrode materials. Some electrochemical parameters vary depending on sizing, but are too small to affect the actual electrochemical performance. A strong SOC dependence is shown for most electrochemical properties, including the electronic conductivity.

  • 91.
    Hellqvist Kjell, Maria
    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.
    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.
    Characterization of Lithium Intercalation Processes of PAN-based Carbon Fibers in a Microelectrode SystemArticle in journal (Other academic)
  • 92. Hjelm, A. K.
    et al.
    Eriksson, T.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Electrochemical investigation of LiMn2O4 cathodes in gel electrolyte at various temperatures2002In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 48, no 2, p. 171-179Article in journal (Refereed)
    Abstract [en]

    A composite lithium battery electrode of LiMn2O4 in combination with a gel electrolyte (1 M LiBF4/24 wt% PMMA/1:1 EC:DEC) has been investigated by galvanostatic cycling experiments and electrochemical impedance spectroscopy (EIS) at various temperatures, i.e. -3 < T < 56 degreesC, For analysis of EIS data, a mathematical model taking into account local kinetics and potential distribution in the liquid phase within the porous electrode structure was used. Reasonable values of the double-layer capacitance, the exchange-current density and the solid phase diffusion were found as a function of temperature. The apparent activation energy of the charge-transfer ( similar to 65 kJ mol(-1)), the solid phase transfer ( similar to 45 kJ mol(-1)) and of the ionic bulk and effective conductance in the gel phase ( similar to 34 kJ mol(-1)), respectively, were also determined, The kinetic results related to ambient temperature were compared to those obtained in the corresponding liquid electrolyte. The incorporated PMMA was found to reduce the ionic conductivity of the free electrolyte, and it was concluded that the presence of 24 wt% PMMA does not have a significant influence on the kinetic properties of LiMn2O4.

  • 93. Hjelm, A. K.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Experimental and theoretical analysis of LiMn2O4 cathodes for use in rechargeable lithium batteries by electrochemical impedance spectroscopy (EIS)2002In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 47, no 11, p. 1747-1759Article in journal (Refereed)
    Abstract [en]

    A comparative study of the impedance response measured with composite electrodes and thin film electrodes of LiMn2O4 was conducted. The electrodes were prepared on different current collectors (i.e. aluminium, carbonised aluminium and gold) and the experiments were run at various state-of-discharge (SOD) and liquid electrolyte compositions. The impedance response was shown to be strongly dependent on the current collector used. It was demonstrated that the high-to-medium frequency semicircle can be attributed to the contact resistance between the current collector and the active electrode material and that the medium-to-low frequency semicircle can be ascribed to the active electrode material. For the analysis, a mathematical model based on a resistance between the current collector and the active electrode material, interfacial-charge transfer coupled to the double-layer charging and solid-phase diffusion was developed. Potential distribution due to porous electrode effects was also considered, Fitting the model to experimental data enabled reasonable values of the exchange-current density, the double-layer capacitance and the solid-phase diffusion coefficient. However, the very low fitted value of the effective conductivity in the liquid phase indicates that this model does not give a satisfying description of the intercalation process of LiMn2O4.

  • 94. Hjelm, A. K.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundqvist, A.
    Investigation of LiMn2O4 cathodes for use in rechargeable lithium batteries by linear sweep voltammetry (LSV) Part II. Experimental study using thin films, single particles and composite electrodes2001In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 509, no 2, p. 139-147Article in journal (Refereed)
    Abstract [en]

    Thin films, single particles and a composite electrode of the cathode material LiMn2O4 in the lithium battery system were investigated by linear sweep voltammetry (LSV) in 1 M LiClO4 + PC:EC. The experimental data were compared to and analysed by mathematical models described in Part I of this work. Analysis of the measured peak potential. E-p, showed clearly that the larger the characteristic length, the larger is the potential peak shift., at a given sweep rate. From the observations of the measured peak current behaviour, I-p, it seems that the composite electrode and the single particles are semi-infinite diffusion limited at all sweep rates applied. For the thin films, when increasing the sweep rate, a transition from finite to semi-infinite mass transfer limitation is indicated. A model based on solid-phase diffusion, interfacial charge transfer and an external IR-drop could fairly well be fitted to the experimental data measured on a single electrode system at a given sweep rate. It was found that the determined parameter values. i.e. solid-phase diffusion coefficient and the IR-drop, vary greatly with sweep rate and characteristic length. These results indicate that the physical description used is an oversimplification for describing the reaction mechanism in LiMn2O4.

  • 95. Hjelm, A. K.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundqvist, A.
    Investigation of LiMn2O4 cathodes for use in rechargeable lithium batteries by linear sweep voltammetry Part I. Theoretical study2001In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 506, no 2, p. 82-91Article in journal (Refereed)
    Abstract [en]

    Linear sweep voltammetry (LSV) is a well-known tool for electrochemical investigations. Different aspects on the use of LSV in the study of an intercalation electrode in the rechargeable lithium battery system have been studied. Mathematical models were used to simulate voltammetry responses for an intercalation material influenced by solid phase diffusion, charge transfer and IR-drop. It was shown how the peak potential and the peak current density vary with sweep rate for different rate determining processes. The simulations show that finite and semi-infinite diffusion is relatively easy to distinguish and also, these two processes behave differently from processes influenced by charge transfer and an external IR-drop. However, the separation of charge transfer and IR-drop is difficult. The use of the convolution sweep voltammetry method was also investigated. It was found that finite diffusion and a non-zero initial concentration limit the applicability in these systems.

  • 96.
    Holmström, Nicklas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wiezell, Katarina
    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.
    Studying Low-Humidity Effects in PEFCs Using EIS I: Experimental2012In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 159, no 8, p. F369-F378Article in journal (Refereed)
    Abstract [en]

    A suitable electrochemical characterization technique for studying water effects at low-humidity conditions is electrochemical impedance spectroscopy (EIS). In general, an EIS spectrum for a PEFC shows one or several capacitive loops and in some situations an inductive loop at the lowest frequencies depending on operating conditions. In this study, low-humidity effects in an operating polymer electrolyte fuel cell have been investigated by using electrochemical impedance spectroscopy (EIS), with the focus on the low-frequency impedance. Measurements have been carried out using several membranes with different thicknesses at various current densities and operating conditions. At frequencies, around 1 Hz down to 5 mHz a pseudo-inductive loop was seen. The magnitude of this loop increased with thicker membranes and at lower humidities. Based on the results the pseudo-inductive loop was attributed to water transport characteristics in the membrane, where the capacitive part is attributed to drying out of the anode and parts of the membrane closest to the anode while the inductive part is attributed to rehydration of the membrane and the anode by product water from the oxygen reduction reaction on the cathode. In addition, both the magnitude and the top-frequencies of the pseudo-inductive loop were affected by the flow rate.

  • 97.
    Holmström, Niklas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ihonen, J.
    Lundblad, Anders
    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 influence of the gas diffusion layer on water management in polymer electrolyte fuel cells2007In: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 7, no 4, p. 306-313Article in journal (Refereed)
    Abstract [en]

    Performance losses due to flooding of gas diffusion layers (GDLs) and flow fields as well as membrane dehydration are two of the major problems in PEFC. In this investigation, the effect of GDL on the cell water management in PEFC is studied using segmented and single cell experiments. The behaviour of four different commercial GDLs was investigated at both high and low inlet humidity conditions by galvanostatic fuel cell experiments. The influence of varying reactant humidity and gas composition was studied. The results at high inlet humidity show that none of the studied GDLs are significantly flooded on the anode side. On the other hand, when some of the GDLs are used on the cathode side they are flooded, leading to increased mass transfer losses. The results at low inlet humidity conditions show that the characteristics of the GDL influence the membrane hydration. It is also shown that inlet humidity on the anode side has a major effect on flooding at the cathode.

  • 98.
    Hu, Lan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ekström, Henrik
    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.
    A model for gas phase mass transport on the porous nickel electrode in the molten carbonate electrolysis cellManuscript (preprint) (Other academic)
    Abstract [en]

    A one-dimensional model based on the Maxwell-Stefan diffusion equations was applied to evaluate the effect of the reverse water-gas shift reaction and the influence of the gas phase mass transport on the performance of the porous nickel electrode in the molten carbonate electrolysis cell. The concentration gradients in the current collector are larger than in the electrode for the inlet gases not in equilibrium, due to the shift reaction taking place in the electrode. When the humidified gas compositions enter the current collector, the decrease of the shift reaction rate increases the electrode performance. The model well describes the polarization behavior of the Ni electrode in the electrolysis cell when the inlet gases have low contents of hydrogen. The mass-transfer limitations at low contents of water and carbon dioxide are captured in the model, but the effect on the electrode polarization, especially of carbon dioxide, is overestimated. Despite an overestimation in the calculations, the experimental data and the modeling results are still consistent in that carbon dioxide has a stronger effect on the gas phase mass transport than other components, i.e. water and hydrogen.

  • 99.
    Hu, Lan
    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.
    Electrode Kinetics of the Ni Porous Electrode for Hydrogen Production in a Molten Carbonate Electrolysis Cell (MCEC)2015In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 162, no 9, p. F1020-F1028Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to elucidate the kinetics of a porous nickel electrode for hydrogen production in a molten carbonate electrolysis cell. Stationary polarization data for the Ni electrode were recorded under varying gas compositions and temperatures. The slopes of these iR-corrected polarization curves were analyzed at low overpotential, under the assumption that the porous electrode was under kinetic control with mass-transfer limitations thus neglected. The exchange current densities were calculated numerically by using a simplified porous electrode model. Within the temperature range of 600-650 degrees C, the reaction order of hydrogen is not constant; the value was found to be 0.49-0.44 at lower H-2 concentration, while increasing to 0.79-0.94 when containing 25-50% H-2. The dependence on CO2 partial pressure increased from 0.62 to 0.86 with temperature. The reaction order of water showed two cases as did hydrogen. For lower H2O content (10-30%), the value was in the range of 0.47-0.67 at 600-650 degrees C, while increasing to 0.83-1.07 with 30-50% H2O. The experimentally obtained partial pressure dependencies were high, and therefore not in agreement with any of the mechanisms suggested for hydrogen production in molten carbonate salts in this study.

  • 100.
    Hu, Lan
    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.
    Electrode kinetics of the NiO porous electrode for oxygen production in the molten carbonate electrolysis cell (MCEC)2015In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 182, p. 493-509Article in journal (Refereed)
    Abstract [en]

    The performance of a molten carbonate electrolysis cell (MCEC) is to a great extent determined by the anode, i.e. the oxygen production reaction at the porous NiO electrode. In this study, stationary polarization curves for the NiO electrode were measured under varying gas compositions and temperatures. The exchange current densities were calculated numerically from the slopes at low overpotential. Positive dependency on the exchange current density was found for the partial pressure of oxygen. When the temperature was increased in the range 600-650 degrees C, the reaction order of oxygen decreased from 0.97 to 0.80. However, there are two different cases for the partial pressure dependency of carbon dioxide within this temperature range: positive values, 0.09-0.30, for the reaction order at lower CO2 concentration, and negative values, -0.26-0.01, with increasing CO2 content. A comparison of theoretically obtained data indicates that the oxygen-producing reaction in MCEC could be reasonably satisfied by the reverse of oxygen reduction by the oxygen mechanism I, an n = 4 electron reaction, assuming a low coverage of oxide ions at high CO2 content and an intermediate coverage for a low CO2 concentration.

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