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
• • 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
  • H01M8/0204—Non-porous and characterised by the material
  • H01M8/0221—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
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/8605—Porous electrodes
• • 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
  • H01M8/0204—Non-porous and characterised by the material
  • H01M8/0213—Gas-impermeable carbon-containing materials
• • 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
  • H01M8/0204—Non-porous and characterised by the material
  • H01M8/0223—Composites
  • H01M8/0226—Composites in the form of mixtures
• • 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
• • 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
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249924—Noninterengaged fiber-containing paper-free web or sheet which is not of specified porosity

Definitions

• the present invention is directed towards a carbon fiber reinforced thermoplastic bipolar plate for an electrode in a fuel cell or battery.
• the use of carbonaceous material in conjunction with electron collection is well known.
• the function of the carbon or graphite has primarily been that of an electrical current (a currency) collector.
• the current collector also known as bipolar plate, has been formed from a number of conductive materials in a number of sizes and geometries.
• the secondary function of a bipolar plate is to provide an impermeable barrier to separate the gases present on either side of the plate. Fine grooves are typically present on one or both surfaces of the bipolar plate to feed and extract the two gas species involved in the device.
• fuel cells and batteries typically are built by assembling bipolar plates or electrodes and gas diffusion layers.
• the diffusion layer is commonly built from a carbonaceous fiber arrangement (carbon paper or fabric) impregnated with an ion exchange polymer such as fluoro-based polymers and catalysts.
• an ion exchange polymer such as fluoro-based polymers and catalysts.
• thermoset carbon reinforced composites using, for example, carbon fiber reinforcement in an epoxy or phenolic resin
• carbon fiber reinforced fluorocarbon-graphite see U.S. Patent No.4,339,322.
• Short carbon fiber reinforcements have been used to increase electrical conductivity and improve mechanical properties of bipolar plates. These reinforced composites, while having higher strength have certain shortcomings. For example, typically the reinforcement used is introduced in the form of random, short carbon fibers or oriented planar fabrics. These material designs and fabrication approaches result in composites with fibers arranged parallel to the in-plane direction of the bipolar plate. In these materials, with little fiber oriented in the through thickness direction, the carbon fiber only slightly contributes to the effective thorough thickness electro-conductivity. In addition, short fiber reinforced composites and un- reinforced solid graphite materials exhibit poor or moderate mechanical properties. The fabrication techniques associated with some of these materials are also not easily amenable to the shape forming of small details such as the grooves that are typically present at the surface of the bipolar plates.
• a yet further object of the invention is to provide for a bipolar plate that has improved thermal conductivity to dissipate heat.
• a still further object of the invention is to provide for a bipolar plate for which design criteria may be readily changed to meet a particular need. It is yet another object of the invention to be amenable to a low fabrication cost.
• the present invention envisions a carbon fiber reinforced thermoplastic bipolar plate where the continuous fiber is preferentially oriented for fuel cells or batteries.
• the starting fiber reinforcement can take on a variety of forms but essentially involves a carbon fiber mat which is woven, non-woven, knit, stitch bonded or a combination of woven, knit, stitch bonded and staple fibers.
• the mat is subsequently needle punched to orient a large portion of the carbon fibers in the through thickness direction, allowing it to achieve maximum electrical conductivity in the direction where it is the most important.
• the preferred path is parallel to the plate thickness.
• Such a carbonaceous mat may include thermoplastic fibers which are then heat molded into the desired shape to create grooves or other surface features heretofore typically achieved by machining.
• the mats may be impregnated with a thermoplastic resin (powder or solution form) and molded to shape using suitable temperature and pressure.
• Thermoset resins such as epoxy, phenolic vinyl ester or other resins suitable for the purpose may also be injected into the carbonaceous preform and then set into the desired shape.
• a wide variety of reinforcements and shapes may be readily fabricated depending upon the particular application. Moreover, the need to machine the surface of the plates is avoided and thus a complicated and difficult task in their production is eliminated. Furthermore, in view of the superior strength, which results from such a construction, the thickness of the plate may be reduced so as to provide for an increased number of elements in a stack of a given height.
• Figures 1A-1D show a fuel cell stack and examples of bipolar plates configurations.
• Figure 2 is a side sectional view of a battery in the prior art, which generally illustrates a construction thereof;
• Figure 3 is a side sectional general view of a non- woven reinforcing mat containing carbon fibers prior to needling, incorporating the teachings of the present invention;
• Figure 4 is a side sectional view of the mat of Figure 2 after needling, incorporating the teachings of the present invention
• Figure 5 is a side sectional view of a woven mat incorporating woven carbon fibers and staple fibers, prior to needling, incorporating the teachings of the present invention
• Figure 6 is a side sectional view of the mat of Figure 4 after needling, incorporating the teachings of the present invention.
• Figure 7 is a side sectional view of a carbon reinforced bipolar plate after being molded into a composite using thermoplastic fibers or resin to create the desired shape, incorporating the teachings of the present invention.
• Figures 1 A- ID and 2 show representative depictions of a fuel cell and battery found in the prior art.
• Figures 1 A- ID describe a typical fuel cell stack 10 where a membrane 12, two catalyzed gas diffusion layers 14 and two bipolar plates 16, an anode 18 and a cathode 19, constitute an elementary cell unit.
• the hydrogen gas is fed through the grooves of the anode bipolar plate, and diffuses in the porosity of the GDL (gas diffusion layer), the hydrogen gas is separated into protons (hydrogen ions) and electrons.
• the electrolyte membrane 12 in the center allows only the protons to pass through the membrane 12 to the cathode 19 side of the fuel cell.
• FIG. 2 illustrates a battery described in U.S. Patent No. 4,830,938.
• the case has two internal cell separators defining a series of three cells.
• the internals of the cells are pairs of electrodes made from a carbonaceous material, which may be of the type hereinafter discussed. Electrodes are of a dimension such that they can be introduced into an adjacent cell in that portion of the adjacent cell having an opposite polarity. Electrodes are shown as a single piece bent to be insertable into adjacent cells. They can also be two electrodes connected in a manner to conduct current in the same manner as a single piece would. Separating the two electrodes in a cell from electrical contact with each other is a foraminous member, which will at least pass ions.
• Various forms of membrane like material may be employed, e.g. fiberglass mat, polypropylene scrim or film, ion exclusion membranes and the like.
• the preferred electrolyte for such a secondary cell is typically a mixture of an ionizable salt dissolved in a non aqueous non-conducting liquid or paste.
• the electrolyte may be ionizable to some extent as well as any non-conducting solid through which ions will be transported under the influence of electrical charge and discharge.
• the present invention relates to the use of specially designed fibrous carbon preforms that when combined with a thermoplastic polymer or thermoset resin can be used to fabricate a low cost fiber reinforced plastic bipolar plate in a one step process.
• Thermoplastic polymers are preferred, as they offer fast forming of reinforced plastics and do not emit toxic compounds in the resin stage like some thermosets.
• These plates may be used in fuel cells and batteries of the type, for example, shown in Figures 1A-1D and 2. This approach of orientating the conductive fibers in the most suitable direction, yields bipolar plates exhibiting superior electrical performance than that of current plates .
• Orientation of the conductive carbon fibers in the direction parallel to the thickness of the plate promotes improved electrical and thermal conductivity across the bipolar plate and "as-molded" in fine surface details eliminates post forming machining steps and provides two important features in optimizing performance and cost of a fuel cell. This is achieved by thermoforming a three dimensional carbon fiber needled mat containing thermoplastic elements into a composite plate.
• the carbon fiber present throughout the thickness of the plate, also provides a mechanical reinforcement in the construction of the bipolar plate, due to its high modulus and allows for thinner bipolar plates which may be used in the assembly of more compact fuel cells.
• thermoplastic matrix having similar physical properties as the membrane material should enhance the performance of the fuel cell. It will provide better contact surface due to similar thermal expansions which is conducive to better electrical conductivity and good chemical/physical compatibility.
• PEEK porous polyether etherketone
• the invention utilizes a three-dimensional carbon textile form, for example a needle punched mat, to achieve preferential orientation of the conductive fibers along the direction yielding maximum electronic conductivity. In the case of a bipolar plate, the preferred electronic path is through the plate thickness.
• Needle punching of short length fibers and/or continuous fibers allows the introduction of a substantial amount of fibers in the direction parallel to the thickness of the preforms. Also, the use of heat- treated pre-oxidized carbon fiber, heat-treated thermoset pitch fiber, carbon PAN fiber or pitch carbon fiber through the thickness of the bipolar plate will optimize electrical and thermal conductivity.
• thermoplastic fibers or resin provide the means to achieve an impermeable wall between the feed gases.
• the combination of carbon fibers with a polymeric matrix yields a composite exhibiting excellent strength and damage tolerance.
• the polymer may be selected for the particular application to withstand the operating environment of the fuel cell and, in this regard, should be heat and chemical resistant.
• the polymer associated with the carbon reinforcement may be any one of the following polymers: polypropylene, polyamide, polyester, fluoropolymers, polyphenylene sulfide (PPS), polyetherimide
• thermoplastic polymers and thermoset resins such as vinyl ester, epoxy, phenols, etc. suitable for the purpose which may be extruded in a fiber form, may be a resin put in a solution form or may be available in a powder form.
• Fibrous carbon preforms can be a short length fiber, paper, unidirectional tape, woven and non-woven fabric including knitted, stitch bonded multi-axial fabric, 2 and 3 directional fiber weaves.
• Lower cost fibers such as fiberglass or other fillers (carbonaceous conductive and non- conductive fillers) may be combined with the carbon fibers in the needled mat to reduce cost.
• Processing of the final product is accomplished by a number of thermoforming processes (application of temperature and pressure): diaphragm forming, compression molding, pressure/vacuum forming, resin transfer molding, lamination or stamping to consolidate the thermoplastic matrix. To achieve the desired orientation of fibers, the carbon mat is subjected to needle punching.
• Needle punching of carbon fibers is presently used to make thick billets for aircraft brake disks or propulsion hardware.
• These fibrous carbon preforms are usually prepared from pre-oxidized PAN precursor fibers and are subsequently heat-treated at high temperature to transform the low carbon content fiber into a carbon fiber. The carbonization or graphitization temperature determines the fiber carbon content.
• the needling process or mechanical entangling of the fibers
• a certain percentage of fibers are oriented in the direction parallel to the thickness of the preform. The amount of through the thickness fiber is related to the type of needle used and the intensity of needling.
• Carbonaceous needled preforms may also be directly fabricated from PAN fibers and carbonized pitch fibers.
• the present invention envisions the fabrication of thin needle mats from either pre-oxidized PAN fibers, thermoset pitch fibers, or directly from graphitized PAN fibers and/or carbonized pitch fibers.
• the starting fibers can be in either of two general forms. One is pre-oxidized fibers or thermoset fibers where the fibers are only partially heat-treated. These are sometimes referred to as green fibers.
• the pre-oxidized fibers require full heat treatment (carbonization and graphitization) prior to the introduction of the thermoplastic.
• the second form of fibers are those that are fully heat-treated to high temperatures, which allow the introduction of the thermoplastic at an earlier stage. Depending on the state of the carbon fiber, the plastic component of the bi-polar plate is introduced at specific stages of fabrication.
• the type, length and geometry of the pre-oxidized or thermoset fibers, the needling parameters and the type of needles are selected to fabricate needled preforms exhibiting specific amount of through the thickness fiber and fiber volume.
• the fibrous needle mat can be impregnated with a number of thermoplastic polymers. This is achieved using solution coating and powder-coating processes. High thermal conductivity, inorganic powders may also be introduced within the porosity of the carbon preform during that step.
• the prepreg mat is ready to be thermoformed to the final geometry of the bipolar plate using a number of thermoforming processes: diaphragm forming, compression forming, pressure / vacuum forming, resin transfer molding or any other forming process suitable for the purpose.
• the prepreg needled mat may also be formed into a pre-consolidated plate, called a laminate, and subsequently molded to final shape using, for example, stamping. In the situation where PAN fibers or carbonized pitch fibers are used for the mat which exhibit a high modulus, these are more difficult to needle but can be handled using proper techniques and raw materials. Two approaches may be used to introduce the polymer component in the preform.
• the carbon fibers can actually be blended with thermoplastic fibers prior to fabricating the needled preform.
• the thermoplastic fiber can be any of the following polymers: polypropylene, polyamide, polyester, polyphenylene sulfide (PPS), polyether etherketone (PEEK), polyether ketone ketone (PEKK), or any other fiber composition suitable for the purpose.
• the fiber may be pre- blended with the carbon fiber (co-mingled yarn, co-mingled unidirectional tape, co-mingled fabric, etc.) or mixed and fed to the needling machine with the carbon yarn.
• the thermoplastic fiber when melted and subjected to pressure, encapsulates the carbon fibers and allows the formation of very fine surface details upon molding.
• the thermoplastic fibers become the matrix of the composite bipolar plate.
• Another approach is to needle the carbon PAN fiber and subsequently impregnate the porosity of the carbon preform with a selected thermoplastic polymer of the type as aforenoted with regard to the pre-oxidized needled mats. This is achieved using solution coating and powder-coating.
• the prepreg mat can be thermoformed to the final geometry of the bipolar plate using a number of molding processes such as diaphragm forming, compression forming, resin transfer molding, or pressure/vacuum forming.
• the prepreg mat may be formed into a pre-consolidated plate, such as a laminate formed to its final shape by stamping.
• the needled carbon PAN mat may also include some filler such as glass fiber to reduce the cost of the preform.
• bipolar plates may take on other forms of carbon fiber preform.
• chopped carbon fiber mixed with a thermoplastic resin unidirectional tapes, 2D fabrics, 3D weave fabric directly assembled in an organized hybrid textile including thermoplastic fibers or subsequently impregnated with a thermoplastic resin may also be used to fabricate reinforced thermoplastic bipolar plates with fine details.
• carbon fibers exhibiting in their final form a high modulus (i.e. greater than 33 MSI)
• it is desirable to start with a low modulus fiber to achieve a needled preform with the highest possible amount of through the thickness fiber since barbs from the needles tend to cut high modulus fibers and the transfer efficiency is quite poor.
• Pre-oxidized PAN fibers, thermoset pitch fibers or low carbonization temperature pitch fibers are desirable low modulus fibers to begin with to optimize fiber transfer through the thickness. Some specific PAN higher modulus fibers may also be used, with, however, a lesser effectiveness.
• the preforms may be subjected to further heat treatments to raise the carbon content of the fiber. Electrical conductivity in carbon fiber is related to both the nature of the carbon source and to the level of graphitization the fiber is subjected to.
• FIGs 3 through 7 illustrate the carbon mat 20 of the present invention.
• Figure 3 shows a non- woven mat made out of carbon fibers 22.
• the carbon fibers 22 are randomly oriented. Included in the mat as aforenoted might be thermoplastic fiber or filler fibers.
• the mat 20 is needle punched by way of a needling device 24 which is generally illustrated and is well known in the art.
• a needling device 24 which is generally illustrated and is well known in the art.
• the fiber orientation after needle punching a portion of the mat 20 is oriented parallel to the thickness T of the mat 20.
• the number of fibers so oriented will depend upon the degree to which the needle punching is done. Obviously, the highest number of carbon fibers so oriented is most desirable and the entire mat 22 is subject to needle punching. If the mat 20 comprises fibers in need of further • carbonization, then it can be treated accordingly to effect the same. Once this is completed, the mat 20 would, if it contains thermoplastic fibers, be subject to being shaped by thermoforming or other means suitable for the purpose into a composite.
• the mat 20 can be impregnated with an appropriate thermoplastic polymer, which is then processed in a manner as aforenoted into a composite.
• the composite forms the bipolar plate 26 generally illustrated in Figure 7.
• the plate 26 can be provided as part of the molding process (e.g. thermoforming or setting a resin) with a surface configuration 28 of a desirable nature.
• the resulting product is a bipolar plate 26, which has oriented carbon fibers in a matrix having the desired surface configuration.
• the plate 22 is mechanically rigid, impermeable, highly conductive and of the desired shape with the need for machining all but eliminated.
• FIGS 5 and 6 they are directed to a mat 30 which is woven, knitted or of another construction using yarns of suitable material
• the weave pattern may be any one suitable for the purpose.
• the mat 30 includes staple fiber made of carbon 32 and/or other material as aforesaid.
• the mat 30 is needle punched by way of the needling device 24 which serves to orientate the fibers in the desired direction (i.e. parallel to the mat's thickness T.
• the resulting mat 30 is shown in Figure 6.
• the mat 30 can then be processed in a manner as aforenoted with regard to mat 20.
• a bipolar plate can be fabricated having a superior structure and characteristic whilst avoiding the need for machining the surface. Also, due to the mechanical strength of such a reinforced composite structure, it may be relatively thin so as to allow for compact stacking and otherwise reduce fuel cell size. Also, since the bipolar plate is molded, in addition to being able to mold in surface configurations, the plate itself can be molded into different shapes to meet differing applications adding to the versatility of the design.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Electrochemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Manufacturing & Machinery (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Composite Materials (AREA)
• Fuel Cell (AREA)
• Inert Electrodes (AREA)
• Reinforced Plastic Materials (AREA)
• Laminated Bodies (AREA)
• Woven Fabrics (AREA)
• Nonwoven Fabrics (AREA)

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• 2002
  • 2002-05-23 US US10/155,469 patent/US20030219646A1/en not_active Abandoned
• 2003
  • 2003-04-25 JP JP2004508435A patent/JP2005527092A/ja active Pending
  • 2003-04-25 RU RU2004137659A patent/RU2316851C2/ru not_active IP Right Cessation
  • 2003-04-25 ES ES03733893T patent/ES2274241T3/es not_active Expired - Lifetime
  • 2003-04-25 BR BR0311235-7A patent/BR0311235A/pt not_active Application Discontinuation
  • 2003-04-25 DE DE60309312T patent/DE60309312T2/de not_active Expired - Lifetime
  • 2003-04-25 EP EP03733893A patent/EP1506585B1/en not_active Expired - Lifetime
  • 2003-04-25 CN CNB038117681A patent/CN100334760C/zh not_active Expired - Fee Related
  • 2003-04-25 NZ NZ536520A patent/NZ536520A/en unknown
  • 2003-04-25 DK DK03733893T patent/DK1506585T3/da active
  • 2003-04-25 AT AT03733893T patent/ATE343854T1/de not_active IP Right Cessation
  • 2003-04-25 AU AU2003239177A patent/AU2003239177B2/en not_active Ceased
  • 2003-04-25 KR KR10-2004-7018914A patent/KR20050004204A/ko not_active Ceased
  • 2003-04-25 CA CA002486694A patent/CA2486694A1/en not_active Abandoned
  • 2003-04-25 WO PCT/US2003/012856 patent/WO2003100892A1/en not_active Ceased
  • 2003-04-25 MX MXPA04011601A patent/MXPA04011601A/es unknown
• 2004
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