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  • 151.
    Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Kortsdottir, Katrin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Active area determination for porous Pt-electrodes used in PEM fuel cells: Temperature and humidity effects2009Inngår i: Proton Exchange Membrane Fuel Cells 9 / [ed] T. Fuller, C. Hartnig, V. Ramani, H. Uchida, H. Gasteiger, S. Cleghorn, P. Strasser, T. Zawodzinski, D. Jones, P. Shirvanian, T. Jarvi, P. Zelenay, C. Lamy, P. Bele, 2009, s. 1211-1220Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper aim to discuss a proper measure of the electrochemical active area of carbon supported Pt nanoparticle catalyst used in polymer electrolyte membrane (PEM) fuel cells. The cyclic voltammetric determination of hydrogen under potential deposition (Hupd) and carbon monoxide monolayer oxidation (CO stripping) performed in a fuel cell at fuel cell relevant conditions are compared and the influences of operation temperature (25-80 {degree sign}C) and relative humidity (RH) (40-90% RH) are discussed. The results show that both the shape and the charge of the Hupd are strongly dependent on operating conditions. However, for the CO stripping experiments only a negative shift in potential with increasing temperature or humidity was observed in accordance with results from aqueous electrolytes, whereas the charges for CO monolayer oxidation were almost constant for the temperatures investigated.

  • 152.
    Lousada, Claudio M.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Brinck, Tore
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Application of reactivity descriptors to the catalytic decomposition of hydrogen peroxide at oxide surfaces2015Inngår i: Computational and Theoretical Chemistry, ISSN 2210-271X, E-ISSN 2210-2728, Vol. 1070, s. 108-116Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have employed density functional theory (DFT) calculations using the PBE0 functional to study the reaction of decomposition of H2O2 on clusters of: ZrO2, TiO2, Y2O3, Fe2O3, CeO2, CuO, Al2O3, NiO2, PdO2 and Gd2O3. The formation of the products of decomposition of H2O2 and their binding onto these oxides are discussed. The obtained energy barriers for H2O2 decomposition deviate from experimental data in absolute average by 4 kJ mol(-1). The only exceptions are CeO2 and Fe2O3 for which the deviations are very large. The adsorption of HO radicals onto the clusters was also studied. Reactivity descriptors obtained with DFT calculations are correlated with experimental data from literature. We found a direct correlation between the adsorption energy of HO radicals and the change in Mulliken charge of the cation present in the oxide, upon adsorption of these radicals. Other DFT and experimentally obtained reactivity descriptors based on properties of the cations present in the oxides, such as the ionization potential and electronegativity are plotted against experimental and DFT computed properties, respectively. Following the Bronsted-Evans Polanyi principle, there is a correlation between the adsorption energy of the product HO radical and the energy barrier for decomposition of H2O2. The good correlations between experimental data and the data obtained with DFF using minimalistic cluster models of the oxides surfaces indicates that on the real systems the processes that determine the reactivity of H2O2 are very dependent on localized properties of the surfaces.

  • 153.
    Lousada, Claudio M.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Johansson, Adam Johannes
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Brinck, Tore
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Mechanism of H2O2 Decomposition on Transition Metal Oxide Surfaces2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 17, s. 9533-9543Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We performed an experimental and density functional theory (DFT) investigation of the reactions of H2O2 with ZrO2, TiO2, and Y2O3. In the experimental study we determined the reaction rate constants, the Arrhenius activation energies, and the activation enthalpies for the processes of adsorption and decomposition of H2O2 on the surfaces of nano- and micrometersized particles of the oxides. The experimentally obtained enthalpies of activation for the decomposition of H2O2 catalyzed by these materials are 30 +/- 1 kJ.mol(-1) for ZrO2, 34 +/- 1 kJ.mol(-1) for TiO2, and 44 +/- 5 kJ.mol(-1) for Y2O3. In the DFT study, cluster models of the metal oxides were used to investigate the mechanisms involved in the surface process governing the decomposition of H2O2. We compared the performance of the B3LYP and M06 functionals for describing the adsorption energies of H2O2 and HO center dot onto the oxide surfaces as well as the energy barriers for the decomposition of H2O2. The DFT models implemented can describe the experimental reaction barriers with good accuracy, and we found that the decomposition of H2O2 follows a similar mechanism for all the materials studied. The average absolute deviation from the experimental barriers obtained with the B3LYP functional is 6 kJ.mol(-1), while with the M06 functional it is 3 kJ.mol(-1). The differences in the affinity of the different surfaces for the primary product of H2O2 decomposition, the HO radical, were also addressed both experimentally and with DFT. With the experiments we found a trend in the affinity of HO center dot toward the surfaces of the oxides, depending on the type of oxide. This trend is successfully reproduced with the DFT calculations. We found that the adsorption energy of HO center dot varies inversely with the ionization energy of the metal cation present in the oxide.

  • 154.
    Lu, Huiran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. Swerea KIMAB AB.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Flexible Paper Electrodes for Li-Ion Batteries Using Low Amount of TEMPO-Oxidized Cellulose Nanofibrils as Binder2016Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, nr 28, s. 18097-18106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Flexible Li-ion batteries attract increasing interest for applications in bendable and wearable electronic devices. TEMPO-oxidized cellulose nanofibrils (TOCNF), a renewable material, is a promising candidate as binder for flexible Li-ion batteries with good mechanical properties. Paper batteries can be produced using a water-based paper making process, avoiding the use of toxic solvents. In this work, finely dispersed TOCNF was used and showed good binding properties at concentrations as low as 4 wt %. The TOCNF was characterized using atomic force microscopy and found to be well dispersed with fibrils of average widths of about 2.7 nm and lengths of approximately 0.1-1 mu m. Traces of moisture, trapped in the hygroscopic cellulose, is a concern when the material is used in Li-ion batteries. The low amount of binder reduces possible moisture and also increases the capacity of the electrodes, based on total weight. Effects of moisture on electrochemical battery performance were studied on electrodes dried at 110 degrees C in a vacuum for varying periods. It was found that increased drying time slightly increased the specific capacities of the LiFePO4 electrodes, whereas the capacities of the graphite electrodes decreased. The Coulombic efficiencies of the electrodes were not much affected by the varying drying times. Drying the electrodes for 1 h was enough to achieve good electrochemical performance. Addition of vinylene carbonate to the electrolyte had a positive effect on cycling for both graphite and LiFePO4. A failure mechanism observed at high TOCNF concentrations is the formation of compact films in the electrodes.

  • 155.
    Lu, Huiran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Alvarado, Fernando
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. Swerea SICOMP AB, Sweden.
    Li, Jiebing
    Tomani, Per
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lignin as a Binder Material for Eco-Friendly Li-Ion Batteries2016Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 9, nr 3, artikkel-id 127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The industrial lignin used here is a byproduct from Kraft pulp mills, extracted from black liquor. Since lignin is inexpensive, abundant and renewable, its utilization has attracted more and more attention. In this work, lignin was used for the first time as binder material for LiFePO4 positive and graphite negative electrodes in Li-ion batteries. A procedure for pretreatment of lignin, where low-molecular fractions were removed by leaching, was necessary to obtain good battery performance. The lignin was analyzed for molecular mass distribution and thermal behavior prior to and after the pretreatment. Electrodes containing active material, conductive particles and lignin were cast on metal foils, acting as current collectors and characterized using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge cycles. Good reversible capacities were obtained, 148 mAhg(-1) for the positive electrode and 305 mAhg(-1) for the negative electrode. Fairly good rate capabilities were found for both the positive electrode with 117 mAhg(-1) and the negative electrode with 160 mAhg(-1) at 1C. Low ohmic resistance also indicated good binder functionality. The results show that lignin is a promising candidate as binder material for electrodes in eco-friendly Li-ion batteries.

  • 156.
    Lu, Huiran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Guccini, Valentina
    KTH.
    Kim, Hyeyun
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Salazar-Alvarez, German
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Effects of Different Manufacturing Processes on TEMPO-Oxidized Carboxylated Cellulose Nanofiber Performance as Binder for Flexible Lithium-Ion Batteries2017Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, nr 43, s. 37712-37720Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carboxylated cellulose nanofibers (CNF) prepared using the TEMPO-route are good binders of electrode components in flexible lithium-ion batteries (LIB). However, the different parameters employed for the defibrillation of CNF such as charge density and degree of homogenization affect its properties when used as binder. This work presents a systematic study of CNF prepared with different surface charge densities and varying degrees of homogenization and their performance as binder for flexible LiFePO4 electrodes. The results show that the CNF with high charge density had shorter fiber lengths compared with those of CNF with low charge density, as observed with atomic force microscopy. Also, CNF processed with a large number of passes in the homogenizer showed a better fiber dispersibility, as observed from rheological measurements. The electrodes fabricated with highly charged CNF exhibited the best mechanical and electrochemical properties. The CNF at the highest charge density (ISSO mu mol g(-1)) and lowest degree of homogenization (3 + 3 passes in the homogenizer) achieved the overall best performance, including a high Young's modulus of approximately 311 MPa and a good rate capability with a stable specific capacity of 116 mAh g(-1) even up to 1 C. This work allows a better understanding of the influence of the processing parameters of CNF on their performance as binder for flexible electrodes. The results also contribute to the understanding of the optimal processing parameters of CNF to fabricate other materials, e.g., membranes or separators.

  • 157.
    Lu, Huiran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Guccini, Valentina
    Kim, Hyeyun
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Salazar-Alvarez, Germán
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Influence of the degree of fibrillation of TEMPO-CNF on its performance as electrode binder in flexible lithium-ion batteries.Manuskript (preprint) (Annet vitenskapelig)
  • 158.
    Lu, Huiran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hagberg, Johan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Li4Ti5O12 flexible, lightweight electrodes based on cellulose nanofibrils as binder and carbon fibers as current collectors for Li-ion batteries2017Inngår i: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 39, s. 140-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    TEMPO oxidized cellulose nanofibrils (TOCNF) were used as binder material to prepare bendable Li4Ti5O12 (LTO) electrodes. Carbon fiber (CF) layers were integrated as current collectors to enhance the mechanical properties and to increase the specific energy of the electrodes. These electrodes combined with CF current collectors (LTO/CF) show good electrochemical properties and are flexible, sustainable, mechanical and chemical stable, lightweight and produced by a water-based easy filtration process. An increase of the active material weight (LTO) from around 19% to 71% of the electrode and current collector combined weight is demonstrated with CF compared with a copper current collector. Additionally, preparation of the current collector material is non-expensive, quick and easy compared to that of carbon nanotube or graphene. To test the flexible battery application, 4000 times repeated bending was carried out on both the LTO electrodes and the LTO/CF electrodes. This had no significant effect on the morphology, mechanical and electrochemical properties of neither the LTO nor the LTO/CF electrodes. Addition of the CF layer improves the mechanical properties and specific capacity of the LTO-electrode. A thicker LTO electrode with only 2 wt% TOCNF is demonstrated which is promising for thicker electrodes with high energy density. A full cell was assembled with the LTO/CF as negative electrode and LiFePO4 (LFP)/CF as positive, which exhibited a stable cycling performance and good energy density.

  • 159.
    Lu, Huiran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hagberg, Johan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Flexible and lightweight lithium-ion batteries based on cellulose nanofibrils and carbon fibers.Inngår i: Journal of Power SourcesArtikkel i tidsskrift (Annet vitenskapelig)
  • 160.
    Lu, Huiran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hagberg, Johan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Li4Ti5O12 flexible, lightweight electrodes based on cellulose nanofibrils as binder and carbon fibers as current collectors for Li-ion batteries.Artikkel i tidsskrift (Annet vitenskapelig)
  • 161.
    Lundgren, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Thermal Aspects and Electrolyte Mass Transport in Lithium-ion Batteries2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Temperature is one of the most important parameters for the performance, safety, and aging of lithium-ion batteries and has been linked to all main barriers for widespread commercial success of electric vehicles.

    The aim of this thesis is to highlight the importance of temperature effects, as well as to provide engineering tools to study these.

    The mass transport phenomena of the electrolyte with LiPF6  in EC:DEC was fully characterized in between 10 and 40 °C and 0.5 and 1.5 M, and all mass transport properties were found to vary strongly with temperature.

    A superconcentrated electrolyte with LiTFSI in ACN was also fully characterized at 25 °C, and was found to have very different properties and interactions compared to LiPF6  in EC:DEC.

    The benefit of using the benchmarking method termed electrolyte masstransport resistivity (EMTR) compared to using only ionic conductivity was illustrated for several systems, including organic liquids, ionic liquids, solid polymers, gelled polymers, and electrolytes containing flame-retardant additives.

    TPP, a flame-retardant electrolyte additive, was evaluated using a HEV load cycle and was found to be unsuitable for high-power applications such as HEVs.

    A large-format commercial battery cell with a thermal management system was characterized using both experiments and a coupled electrochemical and thermal model during a PHEV load cycle. Different thermal management strategies were evaluated using the model, but were found to have only minor effects since the limitations lie in the heat transfer of the jellyroll.

  • 162.
    Lundgren, Henrik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical Characterization and Temperature Dependency of Mass-Transport Properties of LiPF6 in EC:DEC2015Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 162, nr 3, s. A413-A420Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mass transport in the electrolyte is one of the limiting processes when it comes to the power density and energy efficiency of lithium-ion batteries. Electrolyte characterizations are therefore of utmost importance. This study reports the ionic conductivity, diffusion coefficient, lithium-ion transport number, and thermodynamic enhancement factor, as well as density and viscosity, for the electrolyte LiPF6 in EC:DEC (1 1, by weight) at 10 degrees C, 25 degrees C, and 40 degrees C and for concentrations between 0.5 M and 1.5 M. By combining mathematical modeling and three experiments: conductivity measurements, concentration cells, and galvanostatic polarizations, the mass transport phenomena were fully characterized. All parameters were found to vary strongly with both concentration and temperature proving that temperature dependent parameters are essential when studying thermal behavior of lithium-ion batteries. Moreover, conductivity increased with temperature and showed a local maximum at around 1 M within the concentration range at all temperatures. The other parameters either showed a continuous decrease (diffusion coefficient and lithiumion transport number) or increase (thermodynamic enhancement factor) with concentration at all temperatures. Limited liquid range leading to solvent crystallization at 10 degrees C leads to very poor performance, possibly due to the strong coordination between the lithium ion and the crystallizing species, EC. Overall, the studied electrolyte is found to perform poorly compared to previously studied systems.

  • 163.
    Lundgren, Henrik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrolyte Mass-Transport Benchmarking of Four Types of Lithium-Ion Battery Electrolytes: Organic liquids, Ionic Liquids, Gelled Polymers, and Solid PolymersManuskript (preprint) (Annet vitenskapelig)
  • 164.
    Lundgren, Henrik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Scheers, Johan
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Characterization of the Mass-Transport Phenomena in a Superconcentrated LiTFSI: Acetonitrile Electrolyte2015Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 162, nr 7, s. A1334-A1340Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Superconcentration of aprotic electrolytes has recently emerged as a way to stabilize solvents that otherwise would be impossible to use, in e.g. lithium-ion batteries (LIBs). As demanding applications, such as hybrid electric vehicles and fast charging, become increasingly important, battery manufacturers are struggling to find a suitable electrolyte able to deliver high power with low polarization. Electrolyte characterizations able to accurately predict the high-power performance of such electrolytes are also of utmost importance. This study reports a full.characterization of the mass-transport phenomena for a superconcentrated LiTFSL-acetonitrile electrolyte in concentrations ranging from 2.7 M to 4.2 M. The method obtains the ionic conductivity, cationic transport number, diffusion coefficient, and the thermodynamic enhancement factor, by combining mathematical modeling and three electrochemical experiments. Furthermore, the density and the viscosity were measured. The transport number with respect to the room is found to be very high compared to other liquid LIB electrolytes, but a low diffusion coefficient lowers overall performance. The ionic conductivity decreases quickly with concentration, dropping from 12.7 mS/cm at 2.7 M to 0.76 mS/cm at 4.2 M. Considering all the effects in terms of the mass-transport of the electrolyte, the lower end of the studied concentration range is favorable.

  • 165.
    Lundgren, Henrik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Svens, Pontus
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Tengstedt, Carl
    Lindström, Johan
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Thermal Management of Large-Format Prismatic Lithium-Ion Battery in PHEV Application2016Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, nr 2, s. A309-A317Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal effects are linked to all main barriers to the widespread commercialization of lithium-ion battery powered vehicles. This paper presents a coupled 2D electrochemical - 3D thermal model of a large-format prismatic lithium-ion battery, including a thermal management system with a heat sink connected to the surface opposite the terminals, undergoing the dynamic current behavior of a plug-in hybrid electric (PHEV) vehicle using a load cycle with a maximum current of 8 C, validated using potential and temperature data. The model fits the data well, with small deviations at the most demanding parts of the cycle. The maximum temperature increase and temperature difference of the jellyroll is found to be 9.7 degrees C and 3.6 degrees C, respectively. The electrolyte is found to limit the performance during the high-current pulses, as the concentration reaches extreme values, leading to a very uneven current distribution. Two other thermal management strategies, short side and long side surfaces cooling, are evaluated but are found to have only minor effects on the temperature of the jellyroll, with maximum jellyroll temperatures increases of 9.4 degrees C and 8.1 degrees C, respectively, and maximum temperature differences of 3.7 degrees C and 5.0 degrees C, respectively.

  • 166.
    Malmgren, C.
    et al.
    Engineering Physics, Mid Sweden University.
    Hummelgård, M.
    Engineering Physics, Mid Sweden University.
    Bäckström, J.
    Permascand AB.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Olin, H.
    Engineering Physics, Mid Sweden University.
    Nanoscale characterization of crystallinity in DSA (R) coating2008Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 100, nr Part 5, s. 052026-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dimensionally Stable Anodes (DSA (R)) are used for industrial production of e. g. chlorine and chlorate. It is known that the superior electrocatalytical properties of DSA (R) is due to the large effective area of the porous coating. However, this knowledge is mainly found from in situ electrochemical measurements. Here, we used ex situ methods, AFM, TEM and gas porosimetry, for characterization at the nanoscale. The DSA (R) coating was found to consist of mono-crystalline grains with a size of 20-30 nm and with pores of about 10 nm in diameter. Using a simple geometrical model an effective area was calculated. For a typical coating thickness, an increase of about 1000 times in the effective surface area was found, which is consistent with in situ estimations. These results suggest that the dominating source of surface enlargement is due to nano-crystallinity.

  • 167. Malmgren, Christine
    et al.
    Eriksson, Annika K.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Bäckström, Joakim
    Eriksson, Sten
    Olin, Håkan
    Nanocrystallinity in RuO2 coatings-Influence of precursor and preparation temperature2010Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, nr 14, s. 3615-3618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of precursor and calcination temperature on the nano morphology of ruthenium dioxide on titanium, prepared from thermal decomposition of aqueous salt solutions were investigated. Transmission electron microscopy. X-ray diffraction, gas porosimetry and cyclic voltammetry showed that lower calcination temperature yielded smaller crystallites. The crystallites were between 6 and 22 nm in diameter. When using ruthenium nitrosyl nitrate the firing temperature had a large impact on the grain size, but for chloride there was only a minor effect in the temperature range 350-550 degrees C.

  • 168. Matic, H.
    et al.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jacobsson, P.
    In situ micro-Raman on the membrane in a working PEM cell2005Inngår i: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 8, nr 1, s. A5-A7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An electrochemical cell has been designed for in situ micro-Raman measurements on the polymer membrane in an operating polymer electrolyte cell (PEM). The method is applicable to studies of both the distribution of water and membrane structure in the working cell environment. An initial study of the water distribution across a Nafion 117 membrane in a cell working as a H-2/H-2 pump cell at hydrogen flow and currents from 0 to 300 mA/cm(2) is presented. The results show that a hydration profile with a lower water content at the anode forms as current is applied to the cell.

  • 169. Medard, C.
    et al.
    Lefevre, M.
    Dodelet, J. P.
    Jaouen, F.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Oxygen reduction by Fe-based catalysts in PEM fuel cell conditions: Activity and selectivity of the catalysts obtained with two Fe precursors and various carbon supports2006Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, nr 16, s. 3202-3213Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fe-based catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte membrane (PEM) fuel cell conditions have been prepared by adsorbing two Fe precursors on various commercial and developmental carbon supports. The resulting materials have been pyrolyzed at 900C in an atmosphere rich in NH3. The Fe precursors were: iron acetate (FeAc) and iron tetramethoxy phenylporphyrin chloride (ClFeTMPP). The nominal Fe content was 2000 ppm (0.2 wt.%). The carbon supports were HS300, Printex XE-2, Norit SX-Ultra, Ketjenblack, EC-600JD, Acetylene Black, Vulcan XC-72R, Black Pearls 2000, and two developmental carbon black powders, RC1 and RC2 from Sid Richardson Carbon Corporation. The catalyst activity for ORR has been analyzed in fuel cell tests at 80 C as well as by cyclic voltammetry in O-2 saturated H2SO4 at pH 1 and 25 C, while their selectivity was determined by rotating ring-disk electrode in the same electrolyte. A large effect of the carbon support was found on the activity and on the selectivity of the catalysts made with both Fe precursors. The most important parameter in both cases is the nitrogen content of the catalyst surface. High nitrogen content improves both activity towards ORR and selectivity towards the reduction of oxygen to water (4e(-) reaction). A possible interpretation of the activity and selectivity results is to explain them in terms of two Fe-based catalytic sites: FeN2/C and FeN4/C. Increasing the relative amount of FeN2/C improves both activity and selectivity of the catalysts towards the 4e(-) reaction, while most of the peroxide formation may be attributed to FeN4/C. When FeAc is used as Fe precursor, iron oxide and/or hydroxide are also formed. The latter materials have low catalytic activity for ORR and reduce O-2 mainly to H2O2.

  • 170.
    Mikkonen, Saara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jacksén, Johan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Emmer, Åsa
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Selective enrichment of amyloid beta peptides using isotachophoresisManuskript (preprint) (Annet vitenskapelig)
  • 171.
    Mussa, Abdilbari Shifa
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Klett, Matilda
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindström, Rakel Wreland
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Fast-charging to a partial state of charge in lithium-ion batteries: A comparative ageing study2017Inngår i: Journal of Energy Storage, ISSN 2352-152X, Vol. 13, s. 325-333Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 172.
    Nylén, Linda
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Influence of the electrolyte on the electrode reactions in the chlorate process2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The chlorate process is very energy intensive and a major part of the production costs are for electrical energy. Since the electricity prices are constantly increasing and may also vary periodically, the chlorate plants may be forced to adjust their production rate to the price at each moment in order to minimise their costs. Variation of current load requires increased knowledge regarding the electrode behaviour in a wide current range. In this thesis, the aim was to study the impact of the electrolyte on the electrode reactions in order to reduce the energy consumption. The work has mainly been experimental and additionally mathematical modelling has been carried out. A wide current range has been investigated in order to increase the understanding of the phenomena and to obtain results useful for low-load operation during the periods of high electricity cost.

    To operate the anode as energy efficiently as possible, the anode potential should not exceed the critical potential (Ecr), where the slope of the anodic polarisation curve increases, most likely due to ruthenium(VIII)-formation, and where the side reaction of oxygen evolution increases. In this work, the influence of different electrolyte parameters on Ecr has been studied. It was shown that a higher chloride concentration and an increased temperature lowered Ecr, which was expected to increase the risk of exceeding Ecr. However, this was not observed due to a simultaneous favouring of the chloride oxidation. Hence it was concluded that the electrolyte parameters should be optimised so that the lowest possible anode potential is obtained, which would enable higher current densities without exceeding Ecr. A further conclusion is that the increased slope of the polarisation curve at Ecr was possibly related to the lower activity for chloride oxidation on ruthenium oxidised to ruthenium(VIII).

    At full-load operation, the cathode potential was shown to be rather independent of the electrolyte composition despite a large variation of electrolyte parameters. The cathode composition appears to be more critical than the electrolyte composition when aiming at reducing the energy consumption. A strategy to increase the cathode activity could be to in situ apply a catalytic film onto the electrode surface. Therefore, Y(III) was added to a chloride electrolyte in order to form a yttrium hydroxide film on the alkaline cathode surface during hydrogen evolution. The yttrium-hydroxide film activated reduction of water (hydrogen evolution) and hindered hypochlorite reduction, proton reduction and nitrate reduction. The inhibiting properties are important for the prevention of side reactions, which currently are avoided by reducing Cr(VI) of the electrolyte on the cathode, producing an inhibiting chromium-hydroxide film. The studies on Y(III) increase the expectations for finding alternatives to the toxic Cr(VI).

    The addition of chromate to the chlorate electrolyte gives a high cathodic current efficiency and chromate has buffering properties in the electrolyte. The role of the buffer has been investigated for the oxygen evolution from water (one possible anodic side reaction), as well as cathodic hydrogen evolution. Models have been developed for these systems to increase the understanding of the interaction between buffer, electrode reactions and mass transport; the results have been verified experimentally. The chromate buffer increased the limiting current significantly for the cathodic H+ reduction and the cathodic overpotential was reduced drastically at currents lower than the limited current. A too low overpotential could result in the cathodic protection being lost. The presence of chromate buffer increased the limiting current for the oxygen evolution from OH-. The modelling of these systems revealed that the homogeneous reactions connected to the electrode reactions were not in equilibrium at the electrode surface. Further, a good resolution of the interface at the electrode surface was crucial since the, for the electrode reactions, important buffering takes place in an nm-thick reaction layer.

  • 173.
    Nylén, Linda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Investigation of the oxygen evolving electrode in pH-neutral electrolytes: Modelling and experiments of the RDE-cell2007Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, nr 13, s. 4513-4524Artikkel i tidsskrift (Fagfellevurdert)
    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-.

  • 174.
    Nylén, Linda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Critical Anode Potential in the Chlorate Process2006Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, nr 1, s. D14-D20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Anodic polarization curves on dimensionally stable anodes (DSAs) of RuO2/TiO2 in chlorate electrolyte bend to a higher Tafel slope at the critical potential (E-cr) of approximately 1.2 V vs Ag/AgCl. Operating the chlorate process above E-cr leads to increased oxygen evolution and higher potential losses. In this study the impact of different electrolyte parameters and electrolyte impurities on the risk of reaching/exceeding E-cr was investigated. A dependency of Cl- concentration on E-cr of about -90 mV/dec C-Cl(-) was found at pH 2. An addition of Na2Cr2O7 to chlorate electrolyte is necessary in order to keep a high current efficiency on the cathode but was found to increase the anode potential and thereby increase the risk of exceeding E-cr at galvanostatic operation. Additions of impurities as 30 g/L Na2SO4 or 100 ppm Si (added as SiO2) resulted in increased anode potentials, but adding 1.4 g/L KH2PO4 or 1 g/L HF did not have significant short-term impact on the potential. The anode potential as well as E-cr decreased with increased temperature. A high temperature is beneficial in terms of the decreased anode potential, which outweighs the negative effect of a decrease in Ecr.

  • 175.
    Nylén, Linda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Effects of electrolyte parameters on the iron/steel cathode potential in the chlorate process2009Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 39, nr 1, s. 71-81Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study focuses on how different electrolyte parameters of the chlorate process affect the cathode potential for hydrogen evolution on iron in a wide current-density range. The varied parameters were pH, temperature, mass transport conditions and the ionic concentrations of chloride, chlorate, chromate and hypochlorite. At lower current densities, where cathodic protection of the electrode material is important, the pH buffering capacity of the electrolyte influenced the potential to a large extent. It could be concluded that none of the electrolyte parameters had any major effects (< 50 mV) on the chlorate-cathode potential at industrially relevant current densities (around 3 kA m(-2)). Certainly, there is more voltage to gain from changing the cathode material than from modifying the electrolyte composition. This is exemplified by experiments on steel corroded from operation in a chlorate plant, which exhibits significantly higher activity for hydrogen evolution than polished steel or iron.

  • 176.
    Nylén, Linda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Gustavsson, John
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cathodic reactions on an iron RDE in the presence of Y(III)2008Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 155, nr 10, s. E136-E142Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During electrolysis of a solution containing Y(III) ions, a hydrous Y(OH)(3) film forms in the alkaline layer close to a hydrogen-evolving cathode. The film hinders the reduction of dissolved oxygen and activates the reduction of water, hydrogen evolution. The ability to hinder certain reactions while catalyzing hydrogen evolution may be useful in electrolysis applications. In this work the electrochemical properties of an in situ formed yttrium-hydroxide film were studied on an iron rotating disk electrode (RDE) in 0.5 M NaCl with addition of YCl3, NaClO, and of NaNO3. It was found that the film also hinders the reduction of protons, hypochlorite ions, and nitrate ions. At low concentration of Y(III) or at high current density, when the hydrogen evolution was vigorous, no activation of hydrogen evolution was observed. Under these conditions the film still hindered the reduction of ions. The reactant in the catalyzed hydrogen evolution reaction is most likely water molecules within the hydrous film. Nitrate ions were easily reduced on an iron cathode when no Y(III) ions were present in the solution. When studying effects of yttrium addition to a chloride solution the use of YCl3, rather than Y(NO3)(3), as Y(III) source is recommended.

  • 177.
    Nyman, Andreas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    An Experimental and Theoretical Study of the Mass Transport in Lithium-Ion Battery Electrolytes2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lithium‐ion batteries are particularly suitable as energy storage solutions in high power applications, such as hybrid electric vehicles. It is generally considered that one of the processes that limit the power density for lithium‐ion batteries is the mass transport in the electrolyte. Yet, it is still difficult to find a set of properties that fully describe the mass transport for the most common electrolytes. In this work, characterization studies of the mass transport were undertaken for two technically important lithium‐ion battery electrolytes: (1) a liquid electrolyte which consist of LiPF6 dissolved in ethyl methyl carbonate (EMC) and ethylene carbonate (EC) and, (2) a gel electrolyte which consists of LiPF6 dissolved in ethylene carbonate, propylene carbonate (PC) and poly(vinylidenefluoride‐hexafluoropropylene) (P(VdFHFP)).The mass transport in the electrolytes was characterized by combining several experiments. The Maxwell‐Stefan equation was used as basis for the characterization. Models of the transport were formulated from the equation and the apparent transport properties were identified. The characterization methods were first analyzed mathematically in order to establish at which conditions the characterization experiments should be performed. The values of the apparent transport properties were then obtained by optimizing the models to the experimental responses. In order to give the characterization results a comprehensible interpretation and to allow benchmarking of electrolytes, the concept of a normalized potential gradient was introduced.The characterization results of the liquid electrolyte were used in a full cell model of a LiNi0.8Co0.15Al0.05O2 | LiPF6 EC:EMC (3:7) | MAG‐10 cell. The model was developed to analyze the mass transport during a hybrid pulse power characterization (HPPC) test. The analysis was made with a method where the polarization was split up into parts each associated with a process within the cell. The optimum composition in terms of mass transport was found to lie between 0.5 and 1.2 mol/dm3 LiPF6 for the liquid electrolyte and between 5 and 7 wt. % LiPF6 for the gel electrolyte. Less amount of polymer in the gel electrolyte gave a faster mass transport. It was also found that the mass transport in the liquid electrolyte contributed to a major part of the polarization during HPPC tests.

  • 178.
    Nyman, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A Theoretical and Experimental Study of the Mass Transport in Gel Electrolytes: I. Mathematical Analysis of Characterization Method2011Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, nr 6, s. A628-A635Artikkel i tidsskrift (Fagfellevurdert)
    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).

  • 179.
    Nyman, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical characterisation and modelling of the mass transport phenomena in LiPF6-EC-EMC electrolyte2008Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 22, s. 6356-6365Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 180.
    Nyman, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, N. Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A Theoretical and Experimental Study of the Mass Transport in Gel Electrolytes: II. Experimental Characterization of LiPF6-EC-PC-P(VdF-HFP)2011Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, nr 6, s. A636-A643Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 181.
    Nyman, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zavalis, Tommy Georgios
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Elger, Ragna
    Swerea.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A New Methodology for Evaluating the High-Power Behavior of a Li-ion Battery Cell2010Inngår i: Rechargeable Lithium-Ion Batteries, Electrochemical Society, 2010, nr 36, s. 253-262Konferansepaper (Fagfellevurdert)
    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.

  • 182.
    Nyman, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zavalis, Tommy Georgios
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Elger, Ragna
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Analysis of the Polarization in a Li-Ion Battery Cell by Numerical Simulations2010Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, nr 11, s. A1236-A1246Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 183.
    Oyarce, Alejandro
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrode degradation in proton exchange membrane fuel cells2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The topic of this thesis is the degradation of fuel cell electrodes in proton exchange membrane fuel cells (PEMFCs). In particular, the degradation associated with localized fuel starvation, which is often encountered during start-ups and shut-downs (SUs/SDs) of PEMFCs. At SU/SD, O2 and H2 usually coexist in the anode compartment. This situation forces the opposite electrode, i.e. the cathode, to very high potentials, resulting in the corrosion of the carbon supporting the catalyst, referred to as carbon corrosion. The aim of this thesis has been to develop methods, materials and strategies to address the issues associated to carbon corrosion in PEMFC.The extent of catalyst degradation is commonly evaluated determining the electrochemically active surface area (ECSA) of fuel cell electrode. Therefore, it was considered important to study the effect of RH, temperature and type of accelerated degradation test (ADT) on the ECSA. Low RH decreases the ECSA of the electrode, attributed to re-structuring the ionomer and loss of contact with the catalyst.In the search for more durable supports, we evaluated different accelerated degradation tests (ADTs) for carbon corrosion. Potentiostatic holds at 1.2 V vs. RHE were found to be too mild. Potentiostatic holds at 1.4 V vs. RHE were found to induce a large degree of reversibility, also attributed to ionomer re-structuring. Triangle-wave potential cycling was found to irreversibly degrade the electrode within a reasonable amount of time, closely simulating SU/SD conditions.Corrosion of carbon-based supports not only degrades the catalyst by lowering the ECSA, but also has a profound effect on the electrode morphology. Decreased electrode porosity, increased agglomerate size and ionomer enrichment all contribute to the degradation of the mass-transport properties of the cathode. Graphitized carbon fibers were found to be 5 times more corrosion resistant than conventional carbons, primarily attributed to their lower surface area. Furthermore, fibers were found to better maintain the integrity of the electrode morphology, generally showing less degradation of the mass-transport losses. Different system strategies for shut-down were evaluated. Not doing anything to the fuel cell during shut-downs is detrimental for the fuel cell. O2 consumption with a load and H2 purge of the cathode were found to give around 100 times lower degradation rates compared to not doing anything and almost 10 times lower degradation rate than a simple air purge of the anode. Finally, in-situ measurements of contact resistance showed that the contact resistance between GDL and BPP is highly dynamic and changes with operating conditions.

  • 184.
    Oyarce, Alejandro
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Gonzalez, Carlos
    Lima, Raquel Bohn
    Wreland Lindström, Rakel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Direct sorbitol proton exchange membrane fuel cell using moderate catalyst loadings2014Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 116, s. 379-387Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 185.
    Oyarce, Alejandro
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Holmström, Nicklas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Boden, A.
    Randstrom, S.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    In-situ Measurements of Contact Resistance and In-situ Durability studies of Steels and Coatings to be used as Bipolar Plates in PEMFCs2009Inngår i: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, Vol. 25, nr 1, s. 1791-1801Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 186.
    Oyarce, Alejandro
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Holmström, Nicklas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Bodén, A.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Operating conditions affecting the contact resistance of bi-polar plates in proton exchange membrane fuel cells2013Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 231, s. 246-255Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 187.
    Oyarce, Alejandro
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hussami, Linda L.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Corkey, Robert W.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Polyhedral Carbon Nanoforms as catalyst support in a Proton Exchange Membrance cathodeManuskript (preprint) (Annet vitenskapelig)
  • 188.
    Oyarce, Alejandro
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    The Electrochemical Response of a Corroded PEMFC Cathode: Mass-transport at low RHManuskript (preprint) (Annet vitenskapelig)
  • 189.
    Oyarce, Alejandro
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zakrisson, Erik
    Ivity, Matthew
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Baumann Ofstad, Axel
    Bodén, Andreas
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Comparing shut-down strategies for proton exchange membrane fuel cells2014Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 254, s. 232-240Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 190. Parsa, Jalal Basiri
    et al.
    Abbasi, Mahmoud
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Improvement of the Current Efficiency of the Ti/Sn-Sb-Ni Oxide Electrode via Carbon Nanotubes for Ozone Generation2012Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 159, nr 5, s. D265-D269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanocrystalline coatings of a Sn-Sb-Ni-CNT composite were applied on titanium mesh using a dip coating and annealing procedure, and investigated as anode material for ozone generation in perchloric acid. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to reveal the electrode composition and morphology, and voltammetry and current efficiency measurements for electrochemical characterization. Addition of CNT resulted in coatings with a higher loading, a higher onset potential for oxygen evolution and in a higher current efficiency for ozone generation. A long term test of the CNT-containing electrodes at a constant current density (53.5 mA/cm(2)) for 17 h indicated a stable anode potential.

  • 191. Pettersson, Dan
    et al.
    Gustavsson, Marie
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    An experimental system for evaluation of well-defined catalysts on nonporous electrodes in realistic DMFC environment2006Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, nr 28, s. 6584-6591Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 192.
    Randström, Sara
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    New Materials for the Molten Carbonate Fuel Cell2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [sv]

    Smältkarbonatbränslecellen (MCFC) är en högtemperaturbränslecell för stationära applikationer. Den har samma höga totalverkningsgrad som konventionella kraftvärme-anläggningar, men kan byggas i mindre moduler (från 250 kWe). De små modulerna och den bränsleflexibilitet (naturgas, biogas, etanol, diesel) som MCFC har, gör den intressant för exempelvis industrier med organiska restprodukter och höga krav på tillförlitlighet. Den höga temperaturen och närvaron av en saltsmälta gör dock materialdegradering till en viktig faktor för forskning och utveckling inom området. För även om de fälttester som nyligen gjorts har visat på att vissa av degraderingsprocesserna är mindre allvarliga än förväntat, finns fortfarande ett behov av utveckling för att sänka kostnaderna och förlänga livstiden.

    I första delen av detta arbete undersöktes material för olika delar av cellen inom ramarna för EU-projektet IRMATECH. Materialen ansågs vara interessanta alternativ till de nuvarande materialen på grund av deras lägre kostnad och/eller bättre prestanda. Två alternativa anodströmtilledarmaterial undersöktes. För anodströmtilledaren är korrosionen och den elektriska resistansen av det eventuella oxidlagret nyckelparametrar. Dessa parametrar undersöktes och utvärderades. Fastän de båda alternativa materialen hade oxidlager med låg resistans, fanns indikationer på korrosionsprocesser som kan äventyra materialets långtidsstabilitet.

    För katodmaterialet, NiO, har upplösningen varit problemet. De upplösta nickeljonerna fälls ut i elektrolyten och bildar dendriter som kan kortsluta cellen. Därför undersöktes nickelupplösningen hos tre alternativa katodmaterial. Det mest lovande materialet, en nickeloxid-katod dopad med magnesium och järn testades i en singelcell för att studera elektrokemisk prestanda, morfologi och områden där nickelutfällning skett. Resultaten visade att prestandan var jämförbar med NiO, men att den mekaniska stabiliteten måste undersökas ytterligare.

    I ”wet-seal”-området är det rostfria stålet belagt med ett aluminiumskikt för att skydda det från den mycket korrosiva miljön. Tillverkningsprocesserna för dessa aluminiumbeläggningar har hittills varit dyra och komplexa. Därför utvärderades en alternativ tillverkningsprocess. Beläggningen, studerad i både reducerande och oxiderande miljö visade en tendens till att spricka och därmed exponera det underliggande rostfria stålet. Detta berodde troligtvis på en manuell beläggningsprocess som resulterade i ett inhomogent ytskikt.

    I den andra delen av arbetet föreslogs en alternativ tillverkningsmetod, baserad på nyligen publicerade resultat där man elektrodeponerat aluminium från jonvätskor. Dessa har ett större katodiskt fönster än vatten och möjliggör därför elektrodeponering av elektropositiva material. För att göra processen industrivänlig provades ett alternativ till den vanligen använda aluminiumtrikloriden. Det visade sig dock att påverkan av miljön på stabiliteten hos jonvätskan behövde undersökas innan några material kunde tillverkas. Vatten i kombination med syre visade sig ha en stor inverkan på den katodiska strömtätheten. I frånvaro av dessa komponenter var jonvätskan mycket stabil.

  • 193.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Appetecchi, Giovanni Battista
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Moreno, Angelo
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    Passerini, Stefano
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    The influence of air and its components on the cathodic stability of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide2007Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 4, s. 1837-1842Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although water- and air-stable ionic liquids have been in use for some years, experiments found in the literature are still per-formed in inert gas with ppm levels of oxygen and water. In this study, the influence of different environments (vacuum, argon, nitrogen, air and oxygen and water) on the cathodic electrochemical window of the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) is reported and compared with investigations and processes found in the literature. The investigation indicates that this ionic liquid is highly stable in a vacuum and under argon flow. However, its cathodic stability is reduced in nitrogen and dry air. The simultaneous presence of water and air strongly affected the useful electrochemical window, as seen previously for imidazolium-based ionic liquids.

  • 194.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Capobianco, Paolo
    Ansaldo Fuel Cells S.p.A, Italien.
    Corrosion of anode current collectors in MCFC2005Inngår i: / [ed] Pierre Taxil, Catherine Bessada, Michel Cassir, Marcelle Gaune-Escard, 2005, s. 439-441Konferansepaper (Annet vitenskapelig)
  • 195.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Capobianco, Paolo
    Ansaldo Fuel Cells S.p.A.
    Corrosion of anode current collectors in molten carbonate fuel cells2006Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 160, nr 2, s. 782-788Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Corrosion of metallic parts is one of the life-time limiting factors in the molten carbonate fuel cell. In the reducing environment at the anode side of the cell, the corrosion agent is water. As anode current collector, a widely used material is nickel clad on stainless steel since nickel is stable in anode environment, but a cheaper material is desired to reduce the cost of the fuel cell stack. When using the material as current collector one important factor is a low resistance of the oxide layer formed between the electrode and the current collector in order not to decrease the cell efficiency. In this study, some candidates for anode current collectors have been tested in single cell molten carbonate fuel cells and the resistance of the oxide layer has been measured. Afterwards, the current collector was analysed in scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). The results show that the resistances of the formed oxide layers give a small potential drop compared to that of the cathode current collector.

  • 196.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Scaccia, Silvera
    Hydrogen and Fuel Cells Project, ENEA.
    Investigation of a Ni(Mg,Fe)O Cathode for Molten Carbonate Fuel Cell Applications2007Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 7, nr 3, s. 218-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Molten Carbonate Fuel Cell (MCFC) converts chemical energy into electrical energy and heat. Since the working temperature is high, less expensive materials can be used compared to low temperature fuel cells. However, the components of the fuel cell still need to be improved. The dissolution of the NiO cathode has, for a long time, been a problem for the Molten Carbonate Fuel Cell (MCFC) and this area is still the focus for MCFC component research. In this study, solubility measurements for a NiC) cathode material doped with magnesium and iron are carried out and the electrochemical performance of this cathode material is tested under the standard conditions of the MCFC over 2,000 hours and compared with the performance of a standard NiO cathode. After operation, nickel precipitation in the matrices is investigated. It is concluded that a NiO cathode with magnesium and iron could be a viable candidate material for the MCFC.

  • 197.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Montanino, Maria
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Appetecchi, Giovanni B.
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Moreno, Angelo
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Passerini, Stefano
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Effect of water and oxygen traces on the cathodic stability of N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide2008Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 22, s. 6397-6401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although research in the field of ionic liquids for electrochemical applications has led to a deeper knowledge in their electrochemical properties, doubts in the interpretation of the experimental results are still encountered in the literature due to the poor control of the experimental conditions and/or to the limited number of experiments conducted. In this work, the effect of water and oxygen traces on the cathodic stability window of hydrophobic, air-stable ionic liquids composed of N-alkyl-N-methylpyrrolidinium (PYR1A') cations and bis(trifluoromethanesulfonyl)imide (TFSI-) anion, is reported. The extensive investigation performed by linear sweep voltarnmetry (LSV) and cyclic voltarnmetry (CV) indicates that the TFSl- anion is cathodically stable if the ionic liquid is pure and dry. The N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids investigated showed featureless cathodic linear sweep voltarnmetry curves before the massive cation decomposition took place at very low potentials.

  • 198.
    Rashtchi, Hamed
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Acevedo Gomez, Yasna
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Raeissi, Keyvan
    Shamanian, Morteza
    Eriksson, Björn
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zhiani, Mohammad
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wreland Lindström, Rakel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance of a PEM fuel cell using electroplated Ni–Mo and Ni–Mo–P stainless steel bipolar plates2017Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, nr 13, s. F1427-F1436Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The performance and durability of 316L stainless steel bipolar plates (BPP) electroplated with Ni–Mo and Ni–Mo–P coatings are investigated in a proton exchange membrane fuel cell (PEMFC), using a commercial Pt/C Nafion membrane electrode assembly (MEA). The effect of the BPP coatings on the electrochemical performance up to 115 h is evaluated from polarization curves, cyclic voltammetry and electrochemical impedance spectroscopy together with interfacial contact resistance (ICR) measurements between the coatings and the gas diffusion layer. The results show that all the coatings decrease the ICR in comparison to that of uncoated 316L BPP. The Ni-Mo coated BPP shows a low and stable ICR and the smallest effects on MEA performance, including catalyst activity/usability, cathode double layer capacitance, and membrane and ionomer resistance build up with time. After electrochemical evaluation, the BPPs as well as the water effluents from the cell are examined by Scanning Electron Microscopy, Energy Dispersive and Inductively Coupled Plasma spectroscopies. No significant degradation of the coated surface or enhancement in metal release is observed. However, phosphorus addition to the coating does not show to improve its properties, as deterioration of the MEA and consequently fuel cell performance losses is observed.

  • 199.
    Rashtchi, Hamed
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Raeissi, K.
    Shamanian, M.
    Acevedo Gomez, Yasna
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindström, Rakel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Rajaei, V.
    Evaluation of Ni-Mo and Ni-Mo-P Electroplated Coatings on Stainless Steel for PEM Fuel Cells Bipolar Plates2016Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 16, nr 6, s. 784-800Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stainless steel bipolar plates (BPPs) are the preferred choice for proton exchange membrane fuel cells (PEMFCs); however, a surface coating is needed to minimize contact resistance and corrosion. In this paper, Ni–Mo and Ni–Mo–P coatings were electroplated on stainless steel BPPs and investigated by XRD, SEM/EDX, AFM and contact angle measurements. The performance of the BPPs was studied by corrosion and conduction tests and by measuring their interfacial contact resistances (ICRs) ex situ in a PEMFC set-up at varying clamping pressure, applied current and temperature. The results revealed that the applied coatings significantly reduce the ICR and corrosion rate of stainless steel BPP. All the coatings presented stable performance and the coatings electroplated at 100 mA cm−2showed even lower ICR than graphite. The excellent properties of the coatings compared to native oxide film of the bare stainless steel are due to their higher contact angle, crystallinity and roughness, improving hydrophobicity and electrical conductivity. Hence, the electroplated coatings investigated in this study have promising properties for stainless steel BPPs and are potentially good alternatives for the graphite BPP in PEMFC.

  • 200.
    Rexed, Ivan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Applications for Molten Carbonate Fuel Cells2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Molten Carbonate Fuel cells are high temperature fuel cells suitable for distributed generation and combined heat and power, and are today being installed on commercial basis in sizes from 100kW to several MW. Novel applications for MCFC which have attracted interest lately are MCFC used for CO2 separation from combustion flue gas, and high temperature electrolysis with reversible fuel cells. In the first application, the intrinsic capability of the MCFC to concentrate CO2 from the cathode to the anode side through the cell reaction is utilized. In the second application, the high operating temperature and relatively simple design of the MCFC is utilized in electrolysis, with the aim to produce a syngas mix which can be further processed into hydrogen of synthetic fuels.

    In this thesis, the effect on fuel cell performance of operating a small lab-scale molten carbonate fuel cell in conditions which simulate those that would apply if the fuel cell was used for CO2 separation in combustion flue gas was studied. Such operating conditions are characterized especially by a low CO2 concentration at the cathode compared to normal operating conditions. Sulfur contaminants in fuel gas, especially H2S, are known poisoning agents which cause premature degradation of the MCFC. Furthermore, combustion flue gas often contains sulfur dioxide which, if entering the cathode, causes performance degradation by corrosion and by poisoning of the fuel cell. This makes poisoning by sulfur contaminants of great concern for MCFC development. In this thesis, the effect of sulfur contaminants at both anode and cathode on fuel cell degradation was evaluated in both normal and in low CO2 simulated flue gas conditions.     

    The results suggested that the poisoning effect of SO2 at the cathode is similar to that of H2S at the anode, and that it is possibly due to a transfer of sulfur from cathode to anode. Furthermore, in combination with low CO2 conditions at the cathode, SO2 contaminants cause fuel cell poisoning and electrolyte degradation, causing high internal resistance.

    By using a small lab-scale MCFC with commercial materials and standard fuel cell operating conditions, the reversible MCFC was demonstrated to be feasible. The electrochemical performance was investigated in both fuel cell (MCFC) and electrolysis cell (MCEC) modes. The separate electrodes were studied in fuel cell and electrolysis modes under different operating conditions. It was shown that the fuel cell exhibited lower polarization in MCEC mode than in MCFC mode, and a high CO2 concentration at the fuel cell anode reduced the polarization in electrolysis mode, which suggested that CO2 is reduced to produce CO or carbonate.

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