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  • 251.
    Wiezell, Katarina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Modelling and Experimental Investigation of the Dynamics in Polymer Electrolyte Fuel Cells2009Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In polymer electrolyte fuel cells (PEFC) chemical energy, in for example hydrogen, is converted by an electrochemical process into electrical energy. The PEFC has a working temperature generally below 100 °C. Under these conditions water management and transport of oxygen to the cathode are the parameters limiting the performance of the PEFC.

    The purpose of this thesis was to better understand the complex processes in different parts of the PEFC. The rate-limiting processes in the cathode were studied using pure oxygen while varying oxygen pressure and humidity. Mass-transport limitations in the gas diffusion layer using oxygen diluted in nitrogen or helium was also studied. A large capacitive loop was seen at 1-10 Hz with 5-20 % oxygen. When nitrogen was changed to helium, which has a higher binary diffusion coefficient, the loop decreased and shifted to a higher frequency.

    Steady-state and electrochemical impedance spectroscopy (EIS) models have been developed that accounts for water transport in the membrane and the influence of water on the anode. Due to water drag, the membrane resistance changes with current density. This gives rise to a low frequency loop in the complex plane plot. The loop appeared at a frequency of around 0.1 Hz and varied with D/Lm2, where D is the water diffusion coefficient and Lm is the membrane thickness. The EIS model for the hydrogen electrode gave three to four semicircles in the complex plane plot when taking the influence of water concentration on the anode conductivity and kinetics into account. The high-frequency semicircle is attributed to the Volmer reaction, the medium-frequency semicircle to the pseudocapacitance resulting from the adsorbed hydrogen, and the low-frequency semicircles to variations in electrode performance with water concentration. These low-frequency semicircles appear in a frequency range overlapping with the low-frequency semicircles from the water transport in the membrane. The effects of current density and membrane thickness were studied experimentally. An expected shift in frequency, when varying the membrane thickness was seen. This shift confirms the theory that the low-frequency loop is connected to the water transport in the membrane.

  • 252.
    Wiezell, Katarina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Holmström, Nicklas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Studying Low-Humidity Effects in PEFCs Using EIS II: Modeling2012Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 159, nr 8, s. F379-F392Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrochemical impedance spectroscopy (EIS) and steady-state models have been developed to investigate the influence of water transport on the membrane and electrode performance, with focus on the low-frequency impedance. Models for the membrane, hydrogen anode and oxygen cathode were connected in order to take the influence of water concentration on proton conductivity and hydrogen kinetics into account. At low frequencies, below 1 Hz, a pseudo-inductive loop was predicted, resulting from the overlap of the responses from anode and membrane. The anode response could be coupled to changes in the kinetics and polymer conductivity in the active layer, and the membrane response to changes in conductivity with changing water profile. The low frequency capacitive part was attributed to drying of the anode side of the membrane, while the inductive part was attributed to the rehydration of the membrane with water produced at the cathode. The loop appeared at a frequency proportional to 1/L-2, where L is the membrane thickness. The model was successfully fitted to experimental data at different membrane thicknesses, relative humidities and current densities. The modeled data follow the same trends as experimental data, giving an increase in impedance at dry conditions and with thicker membranes.

  • 253. Wijayasinghe, A.
    et al.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    LiFeO2-LiCoO2-NiO materials for Molten Carbonate Fuel Cell cathodes. Part I: Powder synthesis and material characterization2006Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, nr 1-2, s. 165-173Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ternary compositions of LiFeO2LiCoO2 and NiO are expected to posses desirable characteristics for the Molten Carbonate Fuel Cell (MCFC) cathode application. This paper presents a detailed description of the synthesis of LiFeO2-LiCoO2-NiO powders as well as dense sintered materials together with a brief discussion on the common aspects and trends observed in the characterization of these materials for MCFC cathode application. Feasibility of two wet-chemical powder preparation techniques, the Pechini method and the glycine-nitrate method, was investigated to obtain powders with characteristics appropriate for cathode fabrication. Materials in the LiFeO2-NiO binary system and five ternary subsystems, each with a constant molar ratio of LiFeO2/NiO while varying LiCoO2 content, were studied. Powders with characteristics appropriate for MCFC cathode fabrication could be obtained by the Pechini method. The particle size of LiFeO2-LiCoO2-NiO powders considerably depends on the calcination temperature and the material composition. The electrical conductivity study reveals the ability of preparing LiFeO2-LiCoO2-NiO materials with adequate electrical conductivity for MCFC cathode application.

  • 254. Wijayasinghe, A.
    et al.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    LiFeO2-LiCoO2-NiO materials for Molten Carbonate Fuel Cell cathodes. Part II. Fabrication and characterization of porous gas diffusion cathodes2006Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, nr 1-2, s. 175-184Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    LiFeO2-LiCoO2-NiO ternary materials are considered as more viable alternatives to lithiated NiO2 in solving the cathode dissolution problem of the Molten Carbonate Fuel Cell (MCFC). This paper presents a detailed description of fabrication and characterization of LiFeO2-LiCoO2-NiO porous gas diffusion cathodes for MCFC, together with a brief discussion on the limitations and trends observed in cathode optimization. Several LiFeO2-LiCoO2-NiO ternary compositions and a LiFeO2-NiO binary composition, were fabricated into porous cathodes by tape casting and sintering. The sintered cathodes were subjected to phase analysis, electrical conductivity and pore structural characterization. A bimodal pore structure, appropriate for the MCFC cathode, could be achieved in sintered cathodes prepared using poreformers and sub-micron size powders. The amount of poreformers significantly influences the pore structure and the electrical conductivity of sintered cathodes. Furthermore, this study indicates the nature of the compromise to be made between the electrical conductivity, phase purity, pore structure and porosity in optimization cathodes for the MCFC application.

  • 255.
    Wijayasinghe, Athula
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    LiFeO2-LiCoO2-NiO cathodes for molten carbonate fuel cells2005Inngår i: / [ed] Pierre Taxil, Catherine Bessada, Michel Cassir, Marcelle Gaune-Escard, 2005, s. 425-429Konferansepaper (Annet vitenskapelig)
  • 256.
    Wikander, Kjell
    et al.
    Chalmers tekniska högskola, Göteborg.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Palmqvist, Anders
    Chalmers tekniska högskola, Göteborg.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    On the influence of Pt particle size on PEMFC cathode performance2007Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, nr 24, s. 6848-6855Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Colloidal suspensions of almost spherical and crystalline Pt nanoparticles between 1.6 and 2.6 nm in diameter and with narrow size distribution were synthesized using the phase transfer method (PTM) with alkylamines, CnNH2, as stabilizing agents. Batches of such homogenous Pt-CnNH2 (n =8, 12) nanocrystals were deposited onto Vulcan XC-72 carbon powder, and the activity for the oxygen reduction reaction (ORR) of this series of Pt/C materials was evaluated under PEMFC conditions. The aim was to elucidate whether this type of stabilized Pt nanoparticles were as active for the ORR as a corresponding commercial Pt/C material, and if any difference in mass activity could be observed between catalysts with different Pt particle size. In the PEMFC experiments, i.e. voltammetry in oxygen and nitrogen, it was found that, after an initial electrode activation, the ORR activity of the catalysts prepared from the alkylamine-stabilized Pt nanoparticles deposited on carbon was as high as that of the employed commercial reference catalyst. In fact, all samples in the Pt/C series showed high and very similar ORR activity normalized to Pt-loading, without significant dependence on the initial Pt particle size. However, pre- and post-electrochemical characterization of the Pt/C material series with TEM showed that structural changes of the Pt nanoparticles occurred during electrochemical evaluation. In all samples studied the mean Pt particle size increased during the electrochemical evaluation resulting in decreased differences between the samples explaining the observed similar ORR performance of the different materials. These results emphasize the necessity of post-operation characterization of fuel cell catalysts when discussing electrocatalytic activity. In addition, employing complex preparation efforts for lowering the Pt particle size below 3 ran may have limited practical value unless the particles are stabilized from electrochemical sintering.

  • 257.
    Wikander, Kjell
    et al.
    Chalmers tekniska högskola, Göteborg.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Palmqvist, Anders
    Chalmers tekniska högskola, Göteborg.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Holmberg, Krister
    Chalmers tekniska högskola, Göteborg.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Alternative catalysts and carbon support material for PEMFC2006Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 6, nr 1, s. 21-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to investigate the possibility of increasing the reactivity for oxygen reduction reaction (ORR) of the cathode in a PEMFC a series of Pt/C catalysts was prepared using water-in-oil microemulsions for synthesizing Pt nanoparticles. The Pt nanoparticles were deposited on porous carbon support (Vulcan XC-72 or a mesoporous carbon) and the catalysts were processed into MEAs. The MEA samples were evaluated and compared with a commercial sample and with Pt/C catalyst samples prepared using a conventional direct impregnation method. The mesoporous carbon support investigated as a potential alternative to Vulcan XC72 has a very high specific surface area and a narrow pore size distribution. The materials were characterized with XRD, TEM, SEM-EDX, N-2 sorption and steady state polarization. It was found that it is possible to increase the ORR reactivity using the microemulsion route for formation of Pt nanoparticles. It was concluded that the MEA processing conditions for the mesoporous carbon support have to be modified to reach improved ORR reactivity, likely due to the large differences in specific surface area, porosity and conductivity compared to the Vulcan carbon.

  • 258.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Hellqvist Kjel, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Thiol-ene systems in lithium ion conducting thermoset electrolytes2012Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Artikkel i tidsskrift (Annet vitenskapelig)
  • 259.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hellqvist Kjel, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Photoinduced polymerization of structural lithium-ion battery electrolytes2011Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 241Artikkel i tidsskrift (Annet vitenskapelig)
  • 260.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Hellqvist Kjell, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    New approaches for solid polymer electrolytes2012Inngår i: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials, European Conference on Composite Materials, ECCM , 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the present study, series of solid polymer electrolytes (SPEs) have been manufactured in a solvent free process through UV curing. All electrolytes are based on poly(ethylene oxide) systems, however the study also investigates the ability to involve thio ethers in the structure as well as inorganic reinforcing particles covalently bonded to the matrix. The SPEs are tested with EIS and DMA to establish the ionic conductivity and mechanical properties. Thio- ethers improve the conductivity but makes the material softer, while particle reinforcement increases the Tg although the ionic conductivity is constant.

  • 261.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Hellqvist Kjell, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    New structural lithium battery electrolytes using thiol-ene chemistry2013Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 236, s. 22-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of solid poly(ethylene oxide)-methacrylate lithium ion electrolytes containing thio-ether segments have successfully been produced and evaluated with respect to mechanical and electrical performance. The series have been varied in crosslink density and thio-ether content. The study presents thiol-ene compounds as yet another tool to design multifunctional electrolytes, and that they are compatible with and usable for polymer electrolyte systems. The electrolytes, produced in a solvent free process where the oligomers are active diluents of the lithium salt, express a broad range of both mechanical as well as ion conducting properties. Conductivity values presented ranges up to about 8 x 10(-7) S/cm, and a wide spectrum of values of the storage modulus is presented in a range from 2 MPa to 2 GPa at 20 degrees C. The influence of the crosslink density of the poly(ethylene oxide)-methacrylates with and without thio-ether segments is discussed. In order to present correlations between crosslink density and how the lithium ion transport is affected by incorporating multifunctional thiol monomers, density measurements have been undertaken to calculate the average molar mass between the crosslinks.

  • 262.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Kjell, Maria H.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jacques, Eric
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, N. Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Photoinduced free radical polymerization of thermoset lithium battery electrolytes2011Inngår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 47, nr 12, s. 2372-2378Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Series of solid poly(ethylene oxide)-methacrylate electrolytes have successfully been manufactured with an aim to serve in a multifunctional battery both as mechanical load carrier as well as lithium ion conductor. The electrolytes produced, in a solvent free process with no post cure swelling, hold a broad range of both mechanical as well as ion conducting properties. The monomer and Li-salt mixtures have been irradiated with UV light, initiating free radical polymerization to obtain solid smooth, homogenous specimens to be utilized as ion conducting electrolytes. The storage modulus at 20 degrees C is ranging from 1 MPa to almost 2 GPa. The conducting ability of the electrolyte ranges from 5.8 x 10(-10) up to 1.5 x 10(-6) S/cm. These large variations in both mechanical properties as well as ionic conductivity are discussed, but also the versatility within the production technique is emphasized.

  • 263.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Kjell, Maria H.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Effect of Lithium Salt Content on the Performance of Thermoset Lithium Battery Electrolytes2012Inngår i: American Chemical Society Symposium Series (ACS), ISSN 0097-6156, E-ISSN 1947-5918, s. 55-65Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Series of solid poly(ethylene glycol)-methacrylate electrolytes have successfully been manufactured in a solvent free process with an aim to serve in a multifunctional battery, both as mechanical load carrier as well as lithium ion conductor. The electrolytes have been studied with respect to mechanical and electrical properties. The thermoset series differs with respect to crosslink density and glass transition temperature (Tg). The results show that the conductivity increases, with salt content exhibiting similar trends, although at overall levels that differ if measured above or below the Tg of the system. The Tg transition on the other hand is more affected by the salt content for loosely crosslinked thermosets. The coordination of a lithium salt to the PEG-segments play a more important role for the physical state of the material when there are less restrictions due to crosslinking of the PEG-chains. The overall performance of the electrolyte at different temperatures will thus be more affected.

  • 264.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Kjell, Maria H.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Thiol-ene Systems in Lithium Ion Conducting Thermoset ElectrolytesManuskript (preprint) (Annet vitenskapelig)
  • 265.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Cellulose nanofibril reinforced composite electrolyte for lithium ion battery applicationsManuskript (preprint) (Annet vitenskapelig)
  • 266.
    Willgert, Markus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. Swerea SICOMP AB, Sweden.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Malmström Jonsson, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Johansson, Mats K. G.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Cellulose nanofibril reinforced composite electrolytes for lithium ion battery applications2014Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, nr 33, s. 13556-13564Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study describes the synthesis and characterization of a series of four composite electrolytes for lithium ion battery applications. The two-phase electrolytes are composed of a soft, ionic conductive poly(ethylene glycol) (PEG) matrix having stiff nanofibrillated cellulose (CNF) paper as reinforcement to provide mechanical integrity. The reinforcing CNF is modified in order to create covalent bonds between the phases which is particularly beneficial when swelling the composite with a liquid electrolyte to enhance the ionic conductivity. After swelling the composite polymer electrolyte, forming a gelled structure, values of ionic conductivity at 5 x 10(-5) S cm(-1) and an elastic modulus around 400 MPa at 25 degrees C are obtained.

  • 267.
    Wokpetah, Joseph
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. Pennsylvania State University, Department of Chemical Engineering, 212 Fenske Laboratory, University Park, PA, United States .
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Incorporating nano-Si particles into cellulose fibers as a way of making anodic composites for lithium-ion batteries2013Inngår i: Energy and Transport Processes 2013: Core Programming Area at the 2013 AIChE Annual Meeting: Global Challenges for Engineering a Sustainable Future, 2013Konferansepaper (Fagfellevurdert)
  • 268.
    Wreland Lindström, Rakel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Bränsleceller och material: Rapport från arbetsseminarium 16 juni 20112011Rapport (Annet (populærvitenskap, debatt, mm))
  • 269.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Aguinaga, Luis Guerrero
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Oyarce, Alejandro
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ubeda, Diego
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ingratta, Mark
    Jannasch, Patric
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Fuel cell performance using a phosphonated polysulphone ionomer (PSUgPVPA) in the PEM cathode electrode2013Inngår i: Fuel Cell Membranes, Electrode Binders, And Mea Performance, Electrochemical Society, 2013, nr 23, s. 33-45Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Inexpensive and environmentally friendly electrolyte polymers that can be operated at higher temperatures and drier conditions are highly interesting for PEM fuel cells for automotive, portable power and stationary electricity generation applications. In this study an ionomer based on polysulfone grafted with poly(vinylphosphonic acid) (PSUgPVPA) in the cathode Pt/C catalyst layer (CL) was electrochemically characterized and compared to Nafion (R). The performance at different levels of humidity at 80 degrees C was evaluated by polarization and cyclic voltammetry. The results show that the performance of the PSUgPVPA-based cathode CL is comparable to that of Nafion (R) at 100% relative humidity (RH) but with some instabilities. However, at drier conditions significant losses of performance for the PSUgPVPA-based cathode was observed, concomitant to a reduced electrochemical surface area. The lower performance at low humidity is concluded to be due to a combination of lower proton conductivity and wettability or interference with oxygen reduction reaction at lower RH.

  • 270.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hildebrandt, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Polymera bränsleceller (PEMFC): Teknikbevakningsrapport 20092009Rapport (Annet (populærvitenskap, debatt, mm))
  • 271.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Kortsdottir, Katrin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Pérez Ferriz, Francisco Javier
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Conde Lopez, Julio Jose
    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 Effect of Hydrocarbon Impurities in the Hydrogen Fuel on the Anode Activity in PEMFC2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The reformate fuel cell has recently gained increasing attention both for APUs in vehicles

    operating on diesel and in stationary applications such as micro-CHP operating on natural

    or biogas. In addition to hydrogen gas, reformate contain considerable amounts of CO2,

    nitrogen, water vapour and traces of CO, sulphur species and hydrocarbons. CO and H2S

    are well known poisons to the anode [1] but the influence of hydrocarbon species in the

    fuel cell has not been much investigated. We have previously investigated toluene [2] and

    ethene [3] on the anode Pt/C catalyst in the PEM fuel cell. In this paper we will discuss the

    influences of alkenes and alkanes in the light of some novel results on the effect of

    propene, propane and methane in the PEM fuel cell. We have especially focused on the

    adsorption and deactivation phenomena of low concentrations of contaminant on a Pt/C

    catalyst. In the experiments, in situ stripping voltammetry and on-line mass spectrometer

    were employed. The effects of adsorption potential and temperature are discussed. We

    show that propene is more poisonous to the Pt/C catalyst than ethene as it is adsorbed on

    the catalyst surface within the Hupd region and forms an adlayer that can be oxidized in two

    steps between 0.5-1 V (at 80°C, 90%RH) or be hydrogenated to propane in the Hupd region

    and in the presence of hydrogen.

  • 272.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Kortsdottir, Katrin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wesselmark, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Oyarce, Alejandro
    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.
    Active Area Determination of Porous Pt Electrodes Used in Polymer Electrolyte Fuel Cells: Temperature and Humidity Effects2010Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, nr 12, s. B1795-B1801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper discusses the proper measure of the electrochemically active area (ECA)of carbon supported Pt catalyst in PEM fuel cells employing in situ cyclic voltammetry. The charges of the hydrogen underpotential deposition (Hupd) and CO stripping peak obtained in situ are compared, and the influence of operation temperature (25–80°C) and relative humidity (40%–90%) is discussed. The results show that the charges of the Hupd decrease with rising temperature, while the corresponding charges of the CO stripping peak are essentially independent of temperature, at least at high relative humidity. The unexpectedly small Hupd charges are explained by the significant overlap with the hydrogen evolution reaction in a fuel cell at elevated temperatures. According to our results, it is proposed that a more reliable value of Pt ECA is estimated from the CO stripping charge. However, with decreasing humidity the charges of both Hupd and CO stripping peaks decrease, which is probably an effect of increasing blockage of Pt active sites by hydrophobic domains in the electrode ionomer. Some implications of varying cell conditions on the estimated Pt ECA and its correlation with fuel cell activity are discussed in an example from a fuel cell degradation test.

  • 273.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Teknikbevakning av polymera bränsleceller (PEFC)2011Rapport (Annet (populærvitenskap, debatt, mm))
  • 274.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Oyarce, Alejandro
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Aguinaga, Luis Guerrero
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ubeda, Diego
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ingratta, Mark
    Jannasch, Patric
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance of Phosphonated Hydrocarbon Ionomer in the Fuel Cell Cathode Catalyst Layer2013Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 160, nr 3, s. F269-F277Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inexpensive and environmentally friendly electrolyte polymers that can be operated at higher temperatures and drier conditions are highly interesting for PEM fuel cells for automotive, portable power and stationary electricity generation applications. In this study an ionomer based on polysulfone grafted with poly(vinylphosphonic acid) (PSUgPVPA) in the cathode Pt/C catalyst layer was electrochemically characterized and compared to Nafion. The performance at different levels of humidity at 80 degrees C was evaluated by polarization measurements, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results show that the performance of the PSUgPVPA-based cathode catalyst layer is comparable to that of Nafion-at 100% relative humidity (RH) but with some instabilities. However, at drier conditions significant losses of performance for the PSUgPVPA-based cathode was observed. This could be an effect of catalyst poisoning by the ionomer interfering with ORR. However, the concomitant decrease of the electrochemical surface area, double layer capacitance and increased imaginary impedance, indicate that the poorer performance at low humidity is mainly an effect of reduced catalyst wetting by the ionomer in combination with the decreased proton conduction in the ionomeric phase.

  • 275.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Seidel, Y. E.
    Jusys, Z.
    Gustavsson, M.
    Wickman, B.
    Kasemo, B.
    Behm, R. J.
    Electrocatalysis and transport effects on nanostructured Pt/GC electrodes2010Inngår i: J ELECTROANAL CHEM, ISSN 1572-6657, Vol. 644, nr 2, s. 90-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The role and contribution of transport processes in electrocatalytic reactions was investigated in model studies of the oxidation of CO (single-product reaction) and formaldehyde (dual-product reaction), using nanostructured Pt/glassy carbon electrodes with variable Pt loading and defined reactant transport conditions. Nanostructured electrodes with monodispersed, uniformly distributed Pt nanostructures (100-140 nm diameter) supported on planar glassy carbon (GC) electrodes with different densities were prepared by Colloidal Lithography (CL) or Hole-Mask Colloidal Lithography (HCL). Transport effects were evaluated by varying the density of the nanostructures and the electrolyte flow. The resulting changes in the transport limited reaction current (CO oxidation - transition from planar to spherical diffusion with decreasing Pt nanostructure density) and in the distribution of the reaction products HCOOH and CO2 (HCHO oxidation), which is probed by differential electrochemical mass spectrometry (DEMS), are discussed focusing on transport effects. The increasing amount of CO2 with decreasing space velocity (higher nanostructure density, lower electrolyte flow) is explained by increasing re-adsorption and further reaction of desorbing reaction intermediates. (C) 2009 Elsevier B.V. All rights reserved.

  • 276. Wulff, Josefin
    et al.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cathodic current efficiency in the chlorate process2007Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 37, nr 1, s. 181-186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sodium chlorate is produced in undivided electrolysis cells. Hydrogen is evolved on the cathodes, usually made of steel, while chloride ions are oxidised to chlorine on the anodes, usually DSA (R) s. Parasitic cathodic reactions, lowering the cathodic current efficiency (CE), are the reduction of hypochlorite and chlorate ions. These reactions are suppressed by the addition of Cr(VI) to the electrolyte. In this work the effects that time of the electrolysis, chromate concentration and interruption of the electrolysis process have on CE has been investigated. New steel, as well as steel samples cut from cathodes used in a chlorate plant, were used as cathode material. Laboratory experiments in a divided cell were made to determine the rate of hydrogen production, and thereby indirectly CE, at varying operating conditions. It was found that the chromate concentration is important for the CE in the range 0.5-6 g l(-1) Na2Cr2O7. The CE was higher on new steel than on the used steel, which had a more corroded and inhomogeneous surface. When starting the electrolysis the CE was initially low, at a value depending on the operating conditions, but increased with time of polarisation. The time to reach an approximate steady CE was generally in the order of hours. Electrolysis shut downs in the presence of hypochlorite (<= 3 g l(-1) NaClO) resulted in corrosion of iron and a low CE when restarting the process. After one such corrosion shut down the new steel showed as low CE as the used steel. When restarting the electrolysis after a shut down without hypochlorite the CE was higher than before the shut down. Current densities of a simulated bipolar plate during a shut down were measured to 50-150 A m(-2), resulting from oxidation of steel and reduction of oxy chlorides on the catalytic DSA (R) electrode.

  • 277.
    Xu, Yunhua
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Åkermark, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Gyollai, Viktor
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Zou, Da-Peng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Eriksson, Lars
    Duan, Lele
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Zhang, Rong
    Åkermark, Björn
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    A New Dinuclear Ruthenium Complex as an Efficient Water Oxidation Catalyst2009Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 48, nr 7, s. 2717-2719Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A dinuclear ruthenium complex, which acts as a molecular catalyst for water oxidation, has been synthesized and characterized. The electronic and electrochemical properties were studied by UV-vis spectroscopy and cyclic voltammetry. The oxidation potentials of the complex are significantly lowered by introducing a negatively charged carboxylate ligand, in comparison with those of the reported complexes that have neutral ligands. The catalytic activity of the complex toward water oxidation using Ce(NH4)(2)(NO3)(6) as a chemical oxidant was investigated by means of an oxygen electrode and mass spectrometry. The turnover number of this catalyst with Ce-IV as the chemical oxidant was found to be ca. 1700. The mass spectroscopic analysis of the isotopomer distribution in oxygen evolved from O-18-labeled water indicates that O atoms in the evolved oxygen originate from water.

  • 278. Yli-Rantala, E.
    et al.
    Pasanen, A.
    Kauranen, P.
    Ruiz, V.
    Borghei, M.
    Kauppinen, E.
    Oyarce, Alejandro
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Darab, M.
    Sunde, S.
    Thomassen, M.
    Ma-Andersen, S.
    Skou, E.
    Graphitised Carbon Nanofibres as Catalyst Support for PEMFC2011Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 11, nr 6, s. 715-725Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Graphitised carbon nanofibres (G-CNFs) show superior thermal stability and corrosion resistance in PEM fuel cell environment over traditional carbon black (CB) and carbon nanotube catalyst supports. However, G-CNFs have an inert surface with only very limited amount of surface defects for the anchorage of Pt catalyst nanoparticles. Modification of the fibre surface is therefore needed. In this study Pt nanoparticles have been deposited onto as-received and surface-modified G-CNFs. The surface modifications of the fibres comprise acid treatment and nitrogen doping by pyrolysis of a polyaniline (PANI) precursor. The modified surfaces were studied by FTIR and XPS and the electrochemical characterization, including long-term Pt stability tests, was performed using a low-temperature PEMFC single cell. The performance and stability of the G-CNF supported catalysts were compared with a CB supported catalyst and the effects of the different surface treatments were discussed. On the basis of these results, new membrane electrode assemblies (MEAs) were manufactured and tested also for carbon corrosion by in situ FTIR analysis of the cathode exhaust gases. It was observed that the G-CNFs showed 5?times lower carbon corrosion compared to CB based catalyst when potential reached 1.5?V versus RHE in simulated start/stop cycling.

  • 279.
    Zavalis, Tommy Georgios
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Mathematical Models for Investigation of Performance, Safety, and Aging in Lithium-Ion Batteries2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Rechargeable lithium-ion batteries have both the power and energy capabilities to be utilized in hybrid electric vehicles and other power demanding applications. However, there are obstacles primarily related to reliability in safety and lifetime. Additionally, there is still room for improvement in the battery performance.

    In this work, physics-based mathematical models have been successfully set-up and numerically solved to investigate performance, safety, and aging in lithium-ion battery systems. This modeling approach enabled a detailed analysis of the electrochemical processes related to these issues. As the models included many parameters and spatial resolution of several variables with time or frequency, strategies for investigation needed to be developed for most of the work. The accuracy of the investigation was consolidated by the utilization of parameters characterized from experimental work.

    The performance expressed in terms of polarization was determined for a power-optimized battery cell undergoing various operating conditions. A methodology that separated and quantified the contribution of each process to the polarization was set up, allowing the study of the contributions as a snapshot in time and as an average over a cycle. Mass transport in electrolyte was shown to be a crucial feature to improve especially if the battery is expected to undergo high current-loads for long periods of time.

    Safety-concerns when a battery cell is short-circuited were investigated for three types of short-circuit scenarios. All scenarios raised the temperature to the point where exothermic side reactions were initiated. The similarities between the scenarios in temperature increase were a result of the limiting current being reached. The differences, however small, were related to the placement of the short-circuit. Especially when the current collectors were not directly connected by the short circuit, an increased electronic resistance was observed which lowered both the generated current and heat.

    The aging of a battery cell was investigated by model analysis of electrodes harvested from fresh and aged cells. A methodology was used where a frequency-dependent model was fitted to three-electrode impedance experiments by tuning parameters associated to electrode degradation. For cycled cells, electrolyte decomposition products inhibiting the mass transport in the electrolyte and particle cracking in the positive electrode increased the impedance. A similar model was also set up for investigation of the lithium intercalation processes in PAN-based carbon fibers, showing it to have both good mass transport and kinetic capabilities.

  • 280.
    Zavalis, Tommy Georgios
    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.
    Investigation of Short-Circuit Scenarios in a Lithium-Ion Battery Cell2012Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 159, nr 6, s. A848-A859Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A short-circuited lithium-ion battery cell is likely to generate sufficient heat to initiate exothermic side reactions causing thermal runaway. A 2D coupled electrochemical-thermal model was developed to investigate a prismatic LiNi0.8Co0.15Al0.05O2 vertical bar LiPF6, EC/EMC (3:7)vertical bar MAG-10 battery cell that is short-circuited. Three short-circuit scenarios are investigated during the events from when short circuit occurs until exothermic side reactions initiate. The scenarios are an external short circuit, a nail penetration and an impurity-induced short circuit. The model is used to predict the temperature increase within the cell and to explain how the interrelation between the electrochemical processes and the thermal properties affects the increase. Important safety measures are also examined with the model. The simulation results highlight general short-circuit characteristics and critical distinctions between the scenarios. The mass transport of lithium ions in the electrolyte is found to be the most important general characteristic that determines the rate of the temperature increase. The electric resistance distinguishes the scenarios from each other. The rate of the temperature increase is dictated by the mass transport in the electrolyte even when large variations in available active material are made and it is shown to be difficult to slow down the rate by cooling.

  • 281.
    Zavalis, Tommy Georgios
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Klett, Matilda
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Kjell, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wreland Lindström, Rakel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Aging in Lithium-Ion Batteries: Experimental and Model Investigation of Harvested LiFePO4 and Mesocarbon Microbead Graphite Electrodes2013Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 110, s. 335-348Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates aging in LiFePO4/mesocarbon microbead graphite cells that have been subjected to either a synthetic hybrid drive cycle or calendar aging, at 22 C. The investigation involves detailed examination and comparison of harvested fresh and aged electrodes. The electrode properties are determined using a physics-based electrochemical impedance spectroscopy (EIS) model that is fitted to three-electrode EIS measurements, with input from measured electrode capacity and scanning electrode microscopy (SEM). Results from the model fitting provide a detailed insight to the electrode degradation and is put into context with the behavior of the full cell aging. It was established that calendar aging has negligible effect on cell impedance, while cycle aging increases the impedance mainly due to structural changes in the LiFePO4 porous electrode and electrolyte decomposition products on both electrodes. Further, full-cell capacity fade is mainly a consequence of cyclable lithium loss caused by electrolyte decomposition.

  • 282.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Jacques, Eric
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Multifunctional Composite Materials using Lithium Ion Functionalization2015Inngår i: International Conference on Composite Materials 20, ICCM-20, Copenhagen, Denmark, 2015, Copenhagen: ICCM , 2015Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper we show how one can functionalise carbon fibres by using them as an electrochemicalelectrode. The electrochemical process is the same as in a lithium-ion battery cell so that the carbonfibres act as an active electrode in future structural battery concepts. The functionalization of carbonfibres using lithium ion intercalation reveals three novel and interesting possibilities enabling carbonfibres composites to obtain several other multi-functionalities. These are strain sensing, actuation andenergy harvesting.We have found that by intercalating lithium ions into the nano-/micro-structure of carbon fibres apiezo-electrochemical effect is revealed. This is observed as a change in the potential of the carbon fibreelectrode when applying a mechanical load. The response is direct and easily measurable being in theorder of several mV. This can be utilised as a strain sensor since there is a relation between the potentialchange and the strain in the carbon fibre.Secondly, we have measured substantial axial expansion of carbon fibres when intercalated withlithium ions. The strain measured is as high as 1%. Since the stiffness of carbon fibres is very high, thiscorresponds to very large forces. This can be used for actuation or morphing.Thirdly, the newly found piezo-electrochemical effect can be used to harvest energy by convertingmechanical work to electrical energy. Applying a tensile force to carbon fibre bundles used as Liintercalatingelectrodes results in a response of the electrode potential of a few mV which allows, at lowcharge rates, discharge at higher electrode potential than at charge. More electrical energy is therebyreleased from the cell at discharge than provided at charge, harvesting energy from the mechanical workof the applied force.

3456 251 - 282 of 282
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