WO2004107476A2 - Procede et composition pour lier et fermer hermetiquement des composants de pile a combustible - Google Patents

Procede et composition pour lier et fermer hermetiquement des composants de pile a combustible Download PDF

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Publication number
WO2004107476A2
WO2004107476A2 PCT/US2004/016339 US2004016339W WO2004107476A2 WO 2004107476 A2 WO2004107476 A2 WO 2004107476A2 US 2004016339 W US2004016339 W US 2004016339W WO 2004107476 A2 WO2004107476 A2 WO 2004107476A2
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WO
WIPO (PCT)
Prior art keywords
fuel cell
composition
cured
curable
cell assembly
Prior art date
Application number
PCT/US2004/016339
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English (en)
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WO2004107476A3 (fr
Inventor
Michael Paul Levandoski
Robert Michael Sarazin
Original Assignee
Henkel Corporation
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Publication date
Application filed by Henkel Corporation filed Critical Henkel Corporation
Publication of WO2004107476A2 publication Critical patent/WO2004107476A2/fr
Publication of WO2004107476A3 publication Critical patent/WO2004107476A3/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
    • H01M8/0286—Processes for forming seals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
    • H01M8/0263—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant having meandering or serpentine paths
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
    • H01M8/0273—Sealing or supporting means around electrodes, matrices or membranes with sealing or supporting means in the form of a frame
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
    • H01M8/028—Sealing means characterised by their material
    • H01M8/0284—Organic resins; Organic polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/2465—Details of groupings of fuel cells
    • H01M8/247—Arrangements for tightening a stack, for accommodation of a stack in a tank or for assembling different tanks
    • H01M8/248—Means for compression of the fuel cell stacks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a method and a composition for bonding and sealing components of a fuel cell and a fuel cell formed therefrom. More particularly, the present invention relates to a method and to a composition for bonding and sealing membrane, electrode assemblies, bipolar plates, and combinations of membrane electrode assemblies and bipolar plates to form rebuildable, repairable fuel cells!
  • PEM proton exchange membrane
  • the PEM fuel cell contains a membrane electrode assembly (MEA) provided between two flow field or bipolar plates. Gaskets are used between the bipolar plates and the MEA to provide seals thereat.
  • MEA membrane electrode assembly
  • gaskets are used between the bipolar plates and the MEA to provide seals thereat.
  • an individual PEM fuel cell typically provides relatively low voltage or power
  • multiple PEM fuel cells are stacked to increase the overall electrical output of the resulting fuel cell assembly. Sealing is also required between the individual PEM fuel cells.
  • cooling plates are also typically provided to control temperature within the fuel cell. Such plates are also sealed to prevent leakage within the fuel cell assembly. After assembling the fuel cell stack is clamped to secure the assembly.
  • the assignee of these patents describes in U.S. Patent No. 6,495,278 that such preformed patents tend to leak over time and that adhesive bonding of a membrane electrode assembly (MEA) to an adjacent pair of separator plates of a PEM fuel cell with epoxy resins, methacrylate resins, polyurethane polymers (PUR) or aliphatic polysulfides (ALIPS) reduces leakage.
  • MEA membrane electrode assembly
  • PUR polyurethane polymers
  • ALIPS aliphatic polysulfides
  • U.S. Patent Application Publication No. US 2001/0044042 describes the use of a thermosetting fluorine-containing material or a thermosetting silicone as a formed-in-place gasket material placed in grooves between separator plates of a fuel cell and in grooves between separator plates and membrane electrode assemblies of a fuel cell.
  • the material used between the separator plates and the membrane electrode assemblies is described as being adhesive to bond these components.
  • the material used between just the separator plates is described as being non-adhesive to permit replaceability of the components upon disassembly of the fuel cell assembly.
  • U.S. Patent Application Publication No. US 2002/0031698 describes the use of thermosetting silicone sealant to adhesively bond fuel cell components and the use of a thermosetting fluorine-containing sealant with low shear adhesive strength to non-adhesively bong the separator plates.
  • the later sealant is described as being useful for providing stacked fuel cell assemblies with separability and rebuildability features.
  • the sealants are described as being placed into grooves of opposing fuel cell elements. The opposing fuel cell elements are then placed together where the sealants are heated to cure the sealants and to seal and bond the elements.
  • a method for forming a disassembleable fuel cell assembly includes, but is not limited to, the steps of
  • Fuels cells formed by applying a curable composition, compressing the curable composition and then curing the curable composition have been found to offer increased leak- resistance in fuel cells as compared to the use of preformed or formed-in-place gaskets.
  • a method for forming a fuel cell includes the step of
  • the step of curing the curable composition between the first and second fuel cell components is done while the first and second fuel cell components are compressed under the compressive force.
  • the method of this aspect of the present invention may further include the steps of
  • the method of the present invention may further include repeating steps (a)-(d) to form at least two fuel cells and stacking the at least two fuel cells to form a fuel cell assembly which can be disassembled at the third fuel cell component.
  • a fuel cell assembly in another aspect of the present invention, includes a plurality of fuel cells each comprising at least one mating surface, the fuel cells being mated with adjacent fuel cells at the mating surfaces and each mating surface having a cured composition formed therebetween as a compressible gasket, wherein at least one of the compressible gaskets between the fuel cell is adhesively bonded only to one of the adjacent mating surfaces and the other compressible gaskets are adhesively bonded to both of the adjacent mating surfaces.
  • the plurality of fuel cells include proton exchange membrane fuel cells, wherein the mating surfaces are selected from the group consisting of mating surfaces of bipolar plates, mating surfaces of membrane electrode assemblies, or combinations thereof.
  • the cured composition is compressible up to 35% of its thickness.
  • composition is applied at a thickness is at least 0.1 mils.
  • Fuel cells formed in accordance with the present invention are, when placed under a compressive force, substantially leak-free when tested at an internal pressure of at least 30 psig, provided that the compressive force is greater than the internal pressure.
  • the cured compositions of the present invention conform to its adjacent substrates to eliminate surface imperfections and/or leak-paths.
  • a useful composition includes a silicone composition.
  • the composition has low post-cure volatility and is compatible with proton exchange membranes.
  • the composition is advantageously a low-ionic silicone composition and is non-reactive with metals of group 8 of the periodic table, for example platinum.
  • a curable composition useful in fuel cell assemblies includes
  • R and R may be the same or different, and are selected from aryl, alkyl, haloalkyl, hydride, and hydroxide; and n is an integer within the range of about 25 to about 100,000;
  • R 3 is hydrogen and the other R 3 is within R 4 , R 4 is an unsubstituted or substituted monovalent hydrocarbon group; R 5 is hydrogen, or an unsubstituted or substituted monovalent hydrocarbon; or R 3 is within R 4 , provided at least one R 5 is hydrogen; x is an integer within the range of about 3 and 10 and y is an integer within the range of 0 to about 10,000; and
  • the addition cure catalyst is a metal-based addition cure catalyst, wherein the metal is a group 8 metal from the periodic table, for example platinum. It is also advantageous that the curable composition is a low ionic composition, including a composition having low amounts of destructive ionics. Further, curable compositions having less than about 1,000 ppm by weight of cyclic siloxanes on a total composition basis are useful.
  • FIG. 1 is a schematic of a fuel cell of the present invention containing a membrane electrode assembly disposed between opposed fluid-flow field plates, which are also commonly referred to as bipolar plates.
  • Figure 2 is a cross-sectional view with a partial cutaway of the fuel cell of Figure
  • Figure 3 is a partial cross-sectional view of the continuous fluid channels of the fuel cell of Figure 2.
  • Figure 4 is a cross-sectional view of a fuel cell having a membrane electrode assembly adhesively secured between opposed fluid-flow field plates.
  • Figure 5 is a cross-sectional view of a seven-layered membrane electrode assembly of the present invention.
  • Figure 6 is a cross-sectional view of a five-layered membrane electrode assembly of the present invention.
  • Figure 7 is a cross-sectional view of a three-layered membrane electrode assembly of the present invention.
  • Figure 8 is a cross-sectional view of two mono-polar plates joined to form a bipolar plate of a fuel cell.
  • Figure 9 is a cross-sectional view of a plurality of fuel cell components.
  • Figure 10 is a partial cross-sectional view of fuel cell components, one of which having a sealant composition thereon.
  • Figure 11 is a partial cross-sectional view of the fuel cell components of Figure 10 being in a compressed configuration.
  • Figure 12 is a cross-sectional view of the sealant composition of Figure 10 having a thickness.
  • Figure 13 is a cross-sectional view of the sealant composition of Figure 11 having a compressed thickness.
  • Figure 14 is a depiction of an assembled fuel cell assembly having a disassembly and repairability feature according to the present invention.
  • Figure 15 is a depiction of a disassembled fuel cell assembly having a disassembly and repairability feature according to the present invention.
  • Figure 16 is a schematic depiction of an assembly for forming fuel cells in accordance with the present invention.
  • Figure 17 is a schematic depiction of a fuel cell assembly of the present invention.
  • the present invention provides a low volatile, low ionic silicone composition for sealing and/or bonding fuel cell components.
  • the silicone composition contain an addition cure or hydrosilation catalyst that is compatible with the fuel cell assembly in that it does not poison or otherwise adversely effect the catalyst contained within the fuel cell assembly.
  • methods of the present invention include using the inventive compositions as a combination of a cure-in-place sealant and a formed-in-place sealant to provide enhance sealing and bonding while providing disassembly and repairability to the fuel cell assembly.
  • the phrase "cured-in-place” and it variants refer to a composition applied to the surface of one component and cured thereat. Sealing is achieved through compression of the cured material during assembly of the one component with another component. The composition is typically applied by tracing machines in precise patterns.
  • the phrase “formed-in-place” and its variants refer to a composition that is placed between two assembled components and is cured to both components.
  • the combination of the cure-in-place and formed-in-place techniques, for example applying and curing as formed-in-place and sealing as cured-in-place, used in conjunction with the inventive composition of the present invention offers enhanced sealing because both adhesion and compression is used to provide sealing.
  • This combination offers enhanced sealing because, among other things, the mechanical compression obviates the sealing concerns at the knit lines or other dispensing variations of the sealant in fuel cell assemblies.
  • This combination of techniques not only offers enhanced sealing over dimensional variations due to sealant dispensing techniques, but also offers enhanced sealing as it eliminates dimensional variations in the components of the fuel cells. Knit lines are junctions of applied sealant materials.
  • Sealants are typically applied as an elongate bead, elongate strip or elongate thread of material.
  • a knit line is formed where application of the sealant material starts and ends, typically u in abutting relationship to one and the other. At the knit line the amount of material or the corresponding height of material is greater as compared to other portions of applied material.
  • knit lines and dispensing variations are often located at a similar location or locations on like substrates or components. As the components are subsequently stacked to form an assembly of multiple components, the dimensional variability associated with the knit lines or dispensing variations of individual components are magnified.
  • FIG 1 shows, schematically, the basic elements of an electrochemical fuel cell, such as fuel cell 10.
  • Electrochemical fuel cells convert fuel and oxidant to electricity and reaction product.
  • the fuel cell 10 includes a membrane electrode assembly (“MEA") 12 consisting of a solid polymer electrolyte or ion exchange membrane 14 disposed between two electrodes 16A, 16C.
  • the electrodes 16A and 16C are typically formed of porous, electrically conductive sheet material, such as carbon fiber paper.
  • the present invention is not, however, limited to the use of carbon fiber paper and other materials may suitably be used.
  • the MEA 12 contains a layer of catalyst (not shown), typically in the form of finely conrminuted platinum, at each membrane/electrode interface 18 A, 18C to induce the desired electrochemical reaction.
  • the electrodes 16 A, 16C are electrically coupled to provide a path for conducting electrons between the electrodes to an external load (not shown).
  • the fuel permeates the porous electrode material of electrode 16A and reacts at the catalyst layer (not shown) at membrane/electrode interface 18A to form cations, which migrate through the ion exchange membrane 14 to cathode 22.
  • oxygen- containing gas reacts at the catalyst layer (not shown) at membrane/electrode interface 18C to form anions.
  • the anions formed at the cathode 22 react with the cations to form a reaction product.
  • the catalyzed reaction at the anode 26 produces hydrogen cations (protons) from the fuel supply.
  • the ion exchange membrane 14 facilitates the migration of hydrogen ions from the anode 20 to the cathode 22.
  • the ion exchange membrane 14 isolates the hydrogen-containing fuel stream from the oxygen-containing oxidant stream.
  • oxygen reacts at the catalyst layer (not shown) at membrane/electrode interface 18C to form anions.
  • the anions formed at the cathode 22 react with the hydrogen ions that have crossed the ion exchange membrane 14 to form liquid water as the reaction product.
  • the MEA 12 is disposed between two electrically conductive plates, such as fluid- flow field plates or bipolar plates 24A, 24C, each of which has at least one flow passage 26 A, 26C contained therein.
  • These fluid-flow field plates or bipolar plates 24A, 24C are typically formed of compressed, exfoliated graphite; porous graphite; stainless steel or graphite composites.
  • the plates may be treated to effect surface properties, such as surface wetting, or may be untreated.
  • the present invention is not, however, limited to the use of such materials for use as the bipolar plates and other materials may suitably be used.
  • the flow passage 26A directs the fuel, as indicated by arrows 28A, to the anode 20 on the fuel side.
  • the flow passage 26C directs the oxidant, as indicated by arrows 28C, to the cathode 22 on the oxidant side.
  • the bipolar plates 24A, 24C may have additional flow passages 27 opposed to flow passages 26A and 26C.
  • the additional flow passages 27 serve as fuel or oxidant flow paths for an adjoining fuel cell (not shown).
  • the plates 24 A and 24C are referred to as bipolar because they have opposed flow passages, for instance flow passages 26A and 27.
  • fluid-flow field plates are provided on each of the anode and cathode sides.
  • the plates act as current collectors, provide support for the electrodes, provide access channels for the fuel and oxidant to the respective anode and cathode surfaces, and provide channels in some fuel cell designs for the removal of water formed during operation of the cell.
  • Figure 2 is a cross-sectional view of a partial cutaway of the fuel cell 10 taken along the 2-2 axis showing fluid-flow field plate 24C.
  • the fluid-flow field plate 24C includes a single continuous fluid-flow channel 26C which has a fluid inlet 30C and a fluid outlet 32C. Fluid inlet 30C is connected to a source of oxidant (not shown). Continuous flow channel 26C traverses in a plurality of passes a major central area of fluid-flow field plate 24C, which , corresponds to the electrocatalytically active region of the cathode 22.
  • Fluid field flow plate 24A has a similarly connected fluid-flow channel 26A, but its fluid inlet is connected to a fuel source.
  • the fluid-flow channels 26A, 26C are typically 1.5 mm deep and 1 tol.5 mm wide and extend to cover the electrode area of the fuel cell 10.
  • the walls 34A, 34C are typically 1 to 1.5 mm inch thick.
  • the fluid-flow channels 26A, 26C maybe formed by a mechanical deformation process, such as stamping, pressing, milling, molding and the like. A compression plate bearing a relief pattern of the fluid-flow channel is useful to impress the pattern in a flexible graphite sheet.
  • composition 36 may be used to securably seal and/or bond the elements of the MEA 12'.
  • composition 36 can adhesively and securably seal and/or bond the fluid-flow field plates or bipolar plates 24A, 24C to prevent leakage of the reactants (fuel and oxidant) and products (water) from the MEA 12'.
  • composition 36 may not be adhesively secured to abutting fuel cell components, such as field flow plates 24A and 24C.
  • composition 36 encapsulates the ends or edges 35 of MEA 12'. The present invention, however, is not so limited and other sealing techniques may be used to seal fuel cell edges.
  • a composition such as an adhesive composition, may be used to secure the various elements of MEA's.
  • a seven-layered MEA 12' is cross-sectionally depicted in Figure 5.
  • Catalyst layers 17A and 17C are disposed on opposed sides of the ion exchange membrane 14.
  • Compositions 19A and 19C sealablyjoin electrodes 16A and 16C, respectively.
  • MEA 12' is not, however, limited to a seven-layered structure.
  • a five-layered MEA 12' is depicted in Figure 6.
  • the five-layered MEA 12' of Figure 6 has the ion exchange membrane 14 with catalyst layers 17A and 17C and compositions 19A and 19C disposed thereover or disposed over portions of the catalyst layers 17A and 17C.
  • a three-layered MEA 12' is depicted in Figure 7 as having the ion exchange membrane 14 and opposed catalyst layers 17A and 17C.
  • the three-layered MEA 12' of Figure 7 does not have a sealing gasket or sealing material, such as compositions 19A and 19C as shown in Figures 5 and 6.
  • the present invention is not limited to the use of bipolar plates, which have opposed field flow passages.
  • mono-polar plates 29 and 29' which have only one set of field flow passages, may suitably be used.
  • Such mono-polar plates 29 and 29' may be adhesively or otherwise mechanically joined.
  • composition 31 may adhesively join mono-polar plates 29 and 29'.
  • Composition 31 may releasably join the mono-polar plates 29 and 29'.
  • composition 31 may be a conductive composition that permits electrical conductivity therethrough.
  • Two or more fuel cells 10 can be connected together, generally in series but sometimes in parallel, to increase the overall power output of the assembly.
  • one side of a given plate serves as an anode plate for one cell and the other side of the plate can serve as the cathode plate for the adjacent cell.
  • Such a series connected multiple fuel cell arrangement is referred to as a fuel cell stack (not shown), and is usually held together in its assembled state by tie rods and end plates.
  • the stack typically includes manifolds and inlet ports for directing the fuel and the oxidant to the anode and cathode flow field channels.
  • composition 36, 36' can securably seal and/or bond the fluid- flow field plates or bipolar plates 24A, 24C, which are shown as plate 25 having both flow passages 26A and 26C.
  • the composition 36 and 36' may be the same or different.
  • compositions of the present invention may be applied to a fuel cell component 31.
  • Fuel cell component 31 may be any of the above-described structures, for example a bipolar plate, a mono-polar plate, a MEA, different elements of a MEA, a coolant plate or a separator plate.
  • components 31 and 31' maybe pressed against one and the other to have composition 36 abuttingly disposed between mating surfaces 33 and 33' of fuel cell components 31 and 31', respectively.
  • Composition 36 may then be cured to adhesively join fuel cell components 31 and 31', as depicted in Figure 11.
  • composition 36 of Figure 10 has a thickness or height X as depicted in Figure
  • composition 12 has a compressed thickness or height X' as depicted in Figure 13, where X' is less than X.
  • composition 36 is resiliently compressible up to about 50% of its thickness, i.e., X' is up to about 50% of X.
  • Compositions with other resilient compressibilities may suitably be used.
  • compositions with resilient compressibilities from about 1% to about 50% are useful.
  • the composition has a resilient compressibility from about 10% to about 25%.
  • compressibility of a composition refers to the ability of the composition, that is substantially dimensionally stable on a substrate, to dimensionally reduce under force while maintaining its overall structure, sealing and adhesive characteristics.
  • composition may be squeezed to some degree while still maintaining its ability to sealingly join substrates.
  • the composition 36 of Figures 10 and 12 is shown as a round bead, but the present invention is not so limited, and other applied shapes may be suitably be used. Further, the composition 36 of Figures 11 and 13 is shown compressed as an elliptical shape, but other compressed shaped may suitably be used.
  • the amount of thickness X of composition 36 applied to a fuel cell component varies, and the composition 36 may be applied at a thickness of up to about 500 mils (about 13 mm) or greater. Desirably, the composition is applied at a thickness of about 0.1 mils to about 500 mils (or, about 0.0025 mm to about 33 mm). More desirably, the composition is applied from about 1 mil to about 40 mils (or, about 0.025 mm to about 1.0 mm), including thicknesses from about 1 mil to about 5 mils (or, about 0.025 mm to about 0.13 mm).
  • fuel cell assembly 100 includes a plurality of fuel cell modules 46A through 46F, which represent the plurality of fuel cells elements as described above, having compositions for sealing and/or bonding the modules.
  • Fuel cell modules 46A through 46C are adhesively secured to one and the other via composition 40
  • fuel cell modules 46D through 46F are adhesively secured to one and the other via composition 40.
  • Fuel cell modules 46C and 46D are sealed via composition 42, but not adhesively secured.
  • composition 42 is adhesively bonded to only one of the fuel cell modules, for example fuel cell module 46D, to provide a sealing function as a gasket upon mechanical securement of the fuel cell modules to form the fuel cell assembly 100. Because the composition is not adhesively bonded to both fuel cell modules, the fuel cell modules 46C and 46D are separable from one and the other, as depicted in Figure 15. Moreover, the fuel cell modules may have a mating surface 44 or groove for facilitating placement and compression of the silicone compositions of the present invention. [0057]
  • Figure 16 depicts an apparatus 50 useful for producing the fuel cell assemblies of the present invention. Fuel cell components 52, 54 and 56 have compositions 58 disposed thereon.
  • the composition 58 may be robotically dispensed, screen printed or dispensed by other methods onto the fuel cell components 52, 54 and 56.
  • the fuel cell components are then placed onto the base 60 of apparatus 50.
  • the fuel cell components 52, 54 and 56 are aligned and compressed to a desired height or thickness. Compression is accomplished by controllably forcing down top plate 62 toward the bottom plate 60.
  • the top plate 62 is then secured to control the desired height or thickness of the fuel cell components. Any suitable means may be used to clamp the top plate 62, for example a nut/bolt assembly 64 may be used.
  • the compositions 58 are then cured while under compression within apparatus 50.
  • top plate 62 is made from a releasable material or has a layer of releasable material associated with its surface 68.
  • a layer of releasable material may be placed between the top plate 62 and the fuel cell component 52, provides that it covers the composition deposited thereat. Any suitable release material, such as Teflon ® , may suitably be used.
  • cured compositions 58 are adhesively secured to adjacent fuel cell components, such as fuel cell components 52 and 54 and fuel cell components 54 and 56.
  • the composition 58' cured between the release layer and the fuel cell component 52 is adhesively secured only to fuel cell component 52.
  • This cured composition 58' after being released from the release layer, allows the fuel cell assemblies of the present invention to have repairability and rebuildability.
  • this cured composition 58' acts as a cured-in-place gasket while the other cured compositions 58 act as formed-in-place gaskets having the compressingly sealable features of cured-in-place gaskets.
  • the fuel cell component 52 with the cured composition 58' may be mated to any of the above-described fuel cell components or structures, for example a bipolar plate, a mono-polar plate, a MEA, different elements of a MEA, a coolant plate or a separator plate or alternatively, may be mated to fuel cell top or bottom plates, which are described below in conjunction with Figure 17.
  • fuel cell modules 82 are formed into a fuel cell assembly 80 by aligning and stacking the fuel cell modules 82 between fuel cell top plate 84 and fuel cell bottom plate 86. Compressive force is applied and maintained on the fuel cell modules 82 to mechanically compress the compositions of the present invention (not shown) to seal any leak paths of fuel cell assembly 80.
  • At least one of the fuel cell modules 82 advantageously have a repairable and/or rebuildable sealant composition.
  • One means for compressing the fuel cell assembly 80 is depicted in Figure 17 as nut and bolt assemblies 88. Other means for compressing and maintaining some compressive force may suitably be used.
  • the fuel cell assemblies or fuel cell modules of the present invention are substantially leak-free up to an internal pressure of about 60 psig, provided that the assemblies or modules are clamped together at a force greater than internal pressure. Desirably, the assemblies or modules are substantially leak-free up to an internal pressure of about 30 psig when clamped with a greater compressive force. Lower leak-free, internal pressures of about 7 to about 15 psig, which are typical operating pressures of PEM fuel cells, may be used with the present invention, but higher leak-free pressures are preferred.
  • compositions useful with the present invention include silicone compositions, the cured elastomers of which having improved adhesive and sealing properties for use in fuel cells.
  • the compositions include a reactive silicone component, where the silicone component cures by way of an addition cure mechanism.
  • An addition cure catalyst or hydrosilation catalyst is also provided.
  • addition curable silicone component includes addition curing silicone fluids curable under elevated temperature or room temperature conditions.
  • Such polymers are capable of curing in the presence of an addition cure catalyst at elevated temperature conditions, such as about room temperature or greater, but less than about 200°C.
  • the polymers are capable of curing in the presence of an addition cure catalyst at temperatures elevated from room temperature, for example from about 50°C to about 100°C.
  • the addition curable silicone component of the present invention contains functional groups capable of undergoing addition reactions in the presence of an addition cure catalyst.
  • the addition curable silicone component includes, for example, polydiorganosiloxanes having terminal vinyl groups that are curable, together with polydiorganosiloxanes having, for example, hydride functionality available for reaction to form an elastomer.
  • the vinyl-terminated polydimethylsiloxanes may be used in an amount within the range of about 25% to about 90% by weight of the composition, such as about 40% to about 80% by weight.
  • vinyl-terminated polydimethylsiloxanes may be found within the following structure I:
  • R 1 and R 2 may be the same or different, and are selected from aryl, alkyl, haloalkyl (such as triflouropropyl), hydride, hydroxide and the like; and n is an integer between about 25 and 100,000.
  • the hydride-functionalized polydimethylsiloxanes should be present in an amount within the range of about 1% to about 15% by weight of the total composition, such as about 3% to about 10% by weight.
  • n R4 is an unsubstituted or substituted monovalent hydrocarbon group exemplified by alkyl groups, such as methyl, ethyl, propyl and butyl groups; cycloalkyl groups, such as cyclopentyl and cyclohexyl groups; alkenyl groups, such as vinyl and allyl groups; and aryl groups, such as phenyl and tolyl groups; as well as those substituted groups obtained by replacing at least a portion of the hydrogen atoms in the hydrocarbon groups with electron withdrawing groups, such as halogen atoms, cyano groups and the like; R 5 is hydrogen, or an unsubstituted or substituted monovalent hydrocarbon group exemplified by alkyl groups, such as methyl, ethyl, propyl and butyl groups; cycloalkyl groups, such as cyclopentyl and cyclohexyl groups;
  • the vinyl-terminated polydimethylsiloxanes can have viscosities that range from about 100 cst (or centistokes) to about 400,000 cst, desirably from about 4,000 cst to about 50,000 cst.
  • the hydride-functionalized polydimethylsiloxanes can have viscosities that range from about 5 cst to about 1,000 cst, desirably from about 20 cst to about 100 cst.
  • the silicone compositions of the present invention have a low, post- cure volatility.
  • the phrase "low post-cure volatility" and its variants refer to compositions having a low migration of volatile species from the cured composition to adjoining or proximal substrates.
  • One group of materials that potentially migrate from cured compositions are cyclic siloxanes. Such compounds can potentially migrate into fuel cell components or substrates and can effect the electrical properties of the components or substrates, as cyclic siloxanes are non-conductive.
  • compositions of the present invention have low, post- cure volatilities as indicated by having less than about 1,000 wppm (parts-per-million by weight) of cyclic siloxanes. More desirably, compositions of the present invention have less than about 300 wppm of cyclic siloxanes. Even more desirably, compositions of the present invention have less than about 50 wppm of cyclic siloxanes.
  • the silicone compositions of the present invention are low ionic compositions.
  • ionics and its variants refer to materials that are water- extractable or leachable from cured compositions. Such ionics can lead to buildup of corrosion products with the fuel cell. Further, certain ionics are destructive to fuel cells as they poison the fuel cell catalyst. Such destructive ionics include, but are not limited to, water-extractable compounds of or containing sulfur; including sulfides, sulfites and sulfates; phosphorus, including phosphates; nitrogen, including nitrides, amides, amines and hydrazides; tin, lead and arsenic.
  • the compounds of the present invention have less than about 20 wppm of destructive ionics or destructive ionic compounds. More desirably, the compounds of the present invention have less than about 5 wppm of destructive ionics or destructive ionic compounds. Additionally, the total ionics or amount of total ionic materials in the composition of the present invention should be less than 20 wppm and desirably less than about 5 wppm.
  • ionic materials include water-extractable compounds of or containing aluminum, barium, bromine, calcium, chromium, chloride, copper, fluorine, iron, lead, lithium, magnesium, manganese, nitrogen, phosphorous, potassium, sodium, strontium, tin and zinc.
  • the silicone compositions of the present invention may also include certain fillers for example, lithopone, zirconium silicate, hydroxides, such as hydroxides of calcium, aluminum, magnesium, iron and the like, diatomaceous earth, carbonates, such as sodium, potassium, calcium, and magnesium carbonates, oxides, such as zinc, magnesium, chromic, cerium, zirconium and aluminum oxides, calcium clay, fumed silicas, treated silicas, precipitated silicas, untreated silicas, graphite, synthetic fibers and mixtures thereof, provided that the fillers do not contain significant amounts of water-extractable ionic materials.
  • fillers for example, lithopone, zirconium silicate, hydroxides, such as hydroxides of calcium, aluminum, magnesium, iron and the like, diatomaceous earth, carbonates, such as sodium, potassium, calcium, and magnesium carbonates, oxides, such as zinc, magnesium, chromic, cerium, zirconium and aluminum oxides, calcium clay, fumed silicas, treated silicas
  • the filler may be used in an amount within the range of about 1% to 70% by weight of the total composition, such as about 10% to about 50% by weight.
  • the inventive silicone compositions also include an addition cure or hydrosilation catalyst.
  • Suitable addition cure catalysts that can be used with the present compositions include group 8 metal-based catalysts, such as but not limited to, platinum-based or rhodium-based catalysts.
  • a platinum-based catalyst is used, such as platinum-siloxane complex commercially available from Bayer Corporation under the trade designation BAYSILONE U catalyst Pt/L (CAS 73018-55-0).
  • Catalysts which may interfere with the fuel cell catalyst should be avoided.
  • tin-based catalysts should be avoided.
  • the addition cure catalyst should be used in an amount within the range of about
  • additives can also be incorporated into the inventive compositions, provided they do not adversely affect the ability of the compositions to seal or bond fuel cell components or to 1 otherwise adversely affect the performance of the fuel cell.
  • an adhesion promoter can be added to the inventive compositions.
  • Such an adhesion promoter can include, for example, octyl trimethoxysilane (commercially available from Witco Corporation, Greenwich, Connecticut under the trade designation A- 137), glycidyl propyl trimethoxysilane (commercially available from Witco under the trade designation A-187), methacryloxypropyl trimethoxysilane (commercially available from Witco under the trade designation A- 174), vinyl trimethoxysilane, methyltrimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, enoxysilanes, tetraethoxysilane and combinations thereof.
  • octyl trimethoxysilane commercially available from Witco Corporation, Greenwich, Connecticut under the trade designation A- 137
  • glycidyl propyl trimethoxysilane commercially available from Witco under the trade designation A-187
  • the adhesion promoter is glycidyl propyl trimethoxysilane, vinyl trimethoxysilane and combinations thereof.
  • the adhesion promoters when present, may be used in an amount within the range of about 0.05 to about 2% by weight of the total composition.
  • the silicone compositions of the present invention may also include additional crosslinkers.
  • the additional crosslinkers are those capable of reacting with vinyl-terminated and/or hydride-functionalized polydimethylsiloxanes. For instance, trimethylsilyl-terminated hydrogenmethyl dimethyl siloxane copolymer with two or more hydrides per molecule (commercially available from PPG Industries as MASIL XL-1) is appropriate for use herein.
  • Other conventionally known crosslinkers can also be used with the present compositions provided they are able to crosslink the present compositions through an addition cure mechanism without adversely affecting the adhesive and sealant properties of the fuel cell assembly.
  • a thixofropic agent may also be included.
  • the thixofropic agent may be used in an amount within the range of about 0.05 to about 25% by weight of the total composition.
  • examples of such a thixofropic agent include reinforcing silicas, such as fused or fumed silicas, and may be untreated or treated so as to alter the chemical nature of their surface. Virtually any reinforcing fused, precipitated or fumed silica may be used.
  • Examples of such treated fumed silicas include polydimethylsiloxane-treated silicas and hexamethyldisilazane-freated silicas.
  • Such treated silicas are commercially available, such as from Cabot Corporation under the tradename CAB-O-SIL ND-TS and Degussa Corporation under the tradename AEROSIL, such as AEROSIL R805.
  • amorphous and hydrous silicas may be used.
  • commercially available amorphous silicas include AEROSIL 300 with an average particle size of the primary particles of about 7 nm, AEROSIL 200 with an average particle size of the primary particles of about 12 nm, AEROSIL 130 with an average size of the primary particles of about 16 nm; and commercially available hydrous silicas include NIPSIL El 50 with an average particle size of 4.5 nm, NIPSIL E200A with and average particle size of 2.0 nm, and NIPSIL E220A with an average particle size of 1.0 nm (manufactured by Japan Silica Kogya Inc.).
  • Hydroxyl-functional alcohols are also well-suited as the thixofropic agent, such as tris[copoly(oxypropylene)(oxypropylene)] ether of trimethylol propane, and

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Abstract

La présente invention concerne un procédé de formation d'un ensemble pile à combustible démontable. Ce procédé comporte trois opérations: (a) formation d'au moins deux ensembles de pile à combustible, (b) alignement de ces ensembles de piles à combustible de façon que la composition aux silicones, placée extérieurement et durcie, vienne dans la suite des ensembles, et (c) compression des ensembles de pile à combustible de façon à constituer un joint réparable disposé entre les ensembles de pile à combustible. En l'occurrence, la formation en (a) des ensembles de pile à combustible, se décompose en plusieurs opérations: (i) obtention d'un ensemble à électrode à membrane et de deux plaques bipolaires; (ii) application d'une première partie d'une composition aux silicones durcissable sur les surfaces internes correspondante de l'une au moins des plaques bipolaires; (iii) alignement de l'ensemble électrode à membrane entre les deux plaques bipolaires; (iv) compression des plaques bipolaires de façon que la première partie de la composition aux silicones vienne dans la suite de la surface adjacente interne correspondante de la plaque bipolaire adjacente; (v) prise de la première partie de la composition aux silicones de façon à réaliser une liaison adhésive entre les surfaces adjacentes internes correspondantes; (v) poursuite de la compression des plaques bipolaires de façon à comprimer la première partie durcie de la composition aux silicones, pour fermer hermétiquement de façon mécanique les surfaces correspondantes adjacentes contre les imperfections de surface et/ou les chemins de fuite; (vii) application d'une seconde partie de la composition aux silicones durcissable sur les surfaces correspondantes les plus extérieures de l'une au moins des plaques bipolaires; (viii) alignement d'une plaque bipolaire supplémentaire sur les surfaces correspondantes les plus extérieures; enfin (ix) prise de la seconde partie de la composition aux silicones durcissable sans adhérer à la surface correspondante de la plaque bipolaire supplémentaire.
PCT/US2004/016339 2003-05-29 2004-05-25 Procede et composition pour lier et fermer hermetiquement des composants de pile a combustible WO2004107476A2 (fr)

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WO2007024640A1 (fr) * 2005-08-19 2007-03-01 Ballard Power Systems Inc. Joint integre pour ensemble pile a combustible et assemblage de piles a combustible
WO2007084472A2 (fr) * 2006-01-17 2007-07-26 Henkel Corporation Composants de pile à combustible à agent d'étanchéité intégré et procédés et systèmes pour les produire
WO2007084561A2 (fr) 2006-01-17 2007-07-26 Henkel Corporation Ensemble pile à combustible assemblé, procédés, systèmes et compositions d'agent d'étanchéité pour le produire
WO2008016384A2 (fr) 2006-01-17 2008-02-07 Henkel Corporation Agents d'étanchéité durcissables par uv pour piles à combustible et piles à combustible formées avec ces agents
EP1974402A2 (fr) * 2006-01-17 2008-10-01 Henkel Corporation Ensemble pile à combustible collé et procédés et systèmes pour la fabrication de celui-ci
US8066288B2 (en) 2005-10-20 2011-11-29 Henkel Corporation Components comprising polyisobutylene compositions
JP2014225456A (ja) * 2006-01-17 2014-12-04 ヘンケル コーポレイションＨｅｎｋｅｌ Ｃｏｒｐｏｒａｔｉｏｎ 接着燃料電池アセンブリ、接着燃料電池アセンブリを製造するための方法、システムおよびシーラント組成物
DE102016202481A1 (de) * 2016-02-18 2017-08-24 Volkswagen Aktiengesellschaft Brennstoffzellenstapel und Verfahren zum Herstellen eines solchen Brennstoffzellenstapels

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US20010055708A1 (en) * 1998-12-11 2001-12-27 Myron Krasij Proton exchange membrane fuel cell external manifold seal
US20010044042A1 (en) * 2000-05-02 2001-11-22 Masajiro Inoue Fuel cell having sealant for sealing a solid polymer electrolyte Membrane
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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007024640A1 (fr) * 2005-08-19 2007-03-01 Ballard Power Systems Inc. Joint integre pour ensemble pile a combustible et assemblage de piles a combustible
US7914943B2 (en) 2005-08-19 2011-03-29 Daimler Ag Integrated seal for fuel cell assembly and fuel cell stack
US8066288B2 (en) 2005-10-20 2011-11-29 Henkel Corporation Components comprising polyisobutylene compositions
JP2009524193A (ja) * 2006-01-17 2009-06-25 ヘンケル コーポレイション シーラント統合燃料電池部品及びこれを製造する方法及びシステム
WO2007084472A2 (fr) * 2006-01-17 2007-07-26 Henkel Corporation Composants de pile à combustible à agent d'étanchéité intégré et procédés et systèmes pour les produire
EP1974411A2 (fr) * 2006-01-17 2008-10-01 Henkel Corporation Agents d'étanchéité durcissables par uv pour piles à combustible et piles à combustible formées avec ces agents
EP2033248A2 (fr) * 2006-01-17 2009-03-11 Henkel Corporation Ensemble pile à combustible assemblé, procédés, systèmes et compositions d'agent d'étanchéité pour le produire
WO2007084472A3 (fr) * 2006-01-17 2009-05-07 Henkel Corp Composants de pile à combustible à agent d'étanchéité intégré et procédés et systèmes pour les produire
WO2008016384A2 (fr) 2006-01-17 2008-02-07 Henkel Corporation Agents d'étanchéité durcissables par uv pour piles à combustible et piles à combustible formées avec ces agents
WO2007084561A2 (fr) 2006-01-17 2007-07-26 Henkel Corporation Ensemble pile à combustible assemblé, procédés, systèmes et compositions d'agent d'étanchéité pour le produire
EP1974402A2 (fr) * 2006-01-17 2008-10-01 Henkel Corporation Ensemble pile à combustible collé et procédés et systèmes pour la fabrication de celui-ci
US8197989B2 (en) 2006-01-17 2012-06-12 Henkel Corporation UV-curable fuel cell sealants and fuel cells formed therefrom
US8197990B2 (en) 2006-01-17 2012-06-12 Henkel Corporation Sealant integrated fuel cell components and methods and systems for producing the same
EP2033248A4 (fr) * 2006-01-17 2012-08-08 Henkel Corp Ensemble pile à combustible assemblé, procédés, systèmes et compositions d'agent d'étanchéité pour le produire
EP1974411A4 (fr) * 2006-01-17 2012-08-15 Henkel Corp Agents d'étanchéité durcissables par uv pour piles à combustible et piles à combustible formées avec ces agents
EP1974402A4 (fr) * 2006-01-17 2012-08-22 Henkel Corp Ensemble pile à combustible collé et procédés et systèmes pour la fabrication de celui-ci
JP2014225456A (ja) * 2006-01-17 2014-12-04 ヘンケル コーポレイションＨｅｎｋｅｌ Ｃｏｒｐｏｒａｔｉｏｎ 接着燃料電池アセンブリ、接着燃料電池アセンブリを製造するための方法、システムおよびシーラント組成物
DE102016202481A1 (de) * 2016-02-18 2017-08-24 Volkswagen Aktiengesellschaft Brennstoffzellenstapel und Verfahren zum Herstellen eines solchen Brennstoffzellenstapels

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