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
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/023—Porous and characterised by the material
  • H01M8/0241—Composites
  • H01M8/0245—Composites in the form of layered or coated products
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
  • B03C3/34—Constructional details or accessories or operation thereof
  • B03C3/40—Electrode constructions
  • B03C3/45—Collecting-electrodes
  • B03C3/47—Collecting-electrodes flat, e.g. plates, discs, gratings
• • 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
  • H01M4/8647—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites
  • H01M4/8657—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites layered
• • 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
  • H01M4/90—Selection of catalytic material
  • H01M4/92—Metals of platinum group
  • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
  • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
• • 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
  • H01M8/023—Porous and characterised by the material
  • H01M8/0234—Carbonaceous material
• • 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
  • H01M8/023—Porous and characterised by the material
  • H01M8/0239—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
  • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
  • H01M8/184—Regeneration by electrochemical means
  • H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
• • 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
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M2008/1095—Fuel cells with polymeric electrolytes
• • 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 separator plate, a method for producing the separator plate and its use.
• Separator plates or bipolar plates in proton exchange membrane (PEM) fuel cells, phosphoric acid fuel cells or redox flow batteries are either metal-based or carbon-based.
• metallic plates are very stable and can be very thin ( ⁇ 0.2 mm), it is necessary to protect the metal from corrosion and thus increase the service life of the entire system.
• Metallic plates are often coated with precious metals or carbon/graphite to protect against corrosion. This has the disadvantage that it is very expensive.
• Carbon-based plates do not show any corrosion problems, but are mechanically less stable and therefore have high wall thicknesses, typically greater than 0.6 mm. The high wall thicknesses have a negative effect both on the construction volume and weight of the overall system and on the higher costs due to higher manufacturing costs and use of materials.
• the separator plate can be manufactured as a continuous material, since the end product is installed in large numbers and this reduces production costs.
• Carbon fiber papers are known as precursors for gas diffusion layers in fuel cells or redox flow batteries, as described, for example, in EP1369528B1.
• the method described there can be carried out in a continuous process.
• the carbon fiber paper is impregnated with a phenolic resin slurry and then carbonized or graphitized (see exemplary embodiment 1 of EP1369528B1).
• the carbon fiber paper and also the first intermediate product after slurry impregnation and carbonization/graphitization have a very high porosity, which means that they have a very high permeability and also a low mechanical stability.
• the object of the present invention is therefore to provide a separator plate, and its production and use, which overcomes the above disadvantages of the prior art.
• the object is achieved by providing a separator plate comprising a monolayer of carbon fiber reinforced carbon impregnated with a duromer resin, the separator plate having a continuous electrically conductive carbon network and a thickness of less than 0.5 mm, preferably 0.1 to 0.3 mm and a tensile strength greater than 30 MPa, preferably greater than 35 MPa, particularly preferably greater than 45 MPa.
• a continuous electrically conductive network is understood to mean a network that is not interrupted.
• the thickness of the separator plate is understood as meaning the wall thickness, with a thickness of less than 0.5 mm having the advantage that it is mechanically stable enough and has less weight, and therefore requires less construction volume within the layer structure of the entire fuel cell. With a tensile strength of more than 30 MPa, the separator plate is sufficiently mechanically stable, which is why it can be manufactured and handled with a small thickness. With a thickness larger than 0.5 mm, the volume resistance increases so much that the entire fuel cell becomes inefficient.
• the separator plate has a volume resistance of less than 8 m ⁇ cm 2 , preferably less than 5 m ⁇ cm 2 , particularly preferably less than 3 m ⁇ cm 2 .
• volume resistance is greater than 8 m ⁇ cm 2 , the ohmic losses are too high and, for example, the fuel cell loses efficiency and heats up too much.
• the measurement of volume resistance is described below.
• the separator plate advantageously has a density of less than 1.7 g/cm 3 , preferably less than 1.4 g/cm 3 , particularly preferably less than 1.3 g/cm 3 . With a density greater than 1.7 g/cm 3 , the disadvantages of the resulting higher weight of the separator plate have a negative effect.
• carbon fiber reinforced carbon comprises a monolayer of carbon fiber fabric with carbon binder bridges between the carbon fibers. This enables a particularly thin and high-tensile separator plate due to the fiber reinforcement with good conductivity at the same time Carbon binder bridges between the carbon fibers, creating a continuous electrical conductivity network.
• the carbon fiber textile is advantageously from the group of carbon fiber paper, carbon fiber non-woven fabric, carbon fiber fabric or staple fiber fabric.
• Carbon fiber nonwovens are three-dimensional structures that are produced by laying short fibers wet or dry, with the three-dimensional structure being created by mechanical strengthening using needles or water jets.
• Carbon fiber fabrics are textile fabrics that have at least two thread systems that do not run parallel and thus intersect. Staple fiber fabrics are woven yarns made from stretch-broken and twisted filaments.
• the duromer resin includes resins from the group of epoxy resin, phenolic resin, furan resin or benzoxazine resin.
• the duromer resin closes the pores of the carbon fiber textile and at the same time maintains the conductivity based on the carbon network. This also increases the impermeability and mechanical strength.
• the duromer resin includes dispersed fillers.
• the fillers are selected from the group of carbon black, expanded graphite, natural graphite or synthetic graphite, ground carbon fibers or mixtures thereof.
• the conductivity can be further increased by the fillers, since the continuous conductive carbon network is further expanded by the fillers.
• they can also have a positive effect on the tightness of the separator plate, for example by Prevent the formation of pores by better wetting of the carbon network to be impregnated or form an interlocked layer as a gas barrier in the case of a platelet-like anisotropic morphology.
• the mass fraction of fillers is 0% by weight to 40% by weight, preferably 5% by weight to 20% by weight, particularly preferably 8% by weight to 15% by weight. Less than 5% by weight does not lead to a sufficient increase in conductivity and more than 40% by weight leads to high viscosities, which can lead to problems with complete impregnation.
• the cross section of the separator plate has a concentration gradient of the fillers.
• concentration gradient depends on the type of filler and in particular on the particle size. The fact that the fillers mainly remain on the surface further increases the tightness of the separator plate, improves conductivity and reduces contact resistance.
• the separator plate advantageously has a permeation coefficient of less than 5 ⁇ 10 5 cm 2 /s, preferably less than 1 ⁇ 10 5 cm 2 /s. With a permeation coefficient of less than 5x10 -5 cm 2 /s, one can speak of a technically tight separator plate, ie the technical tightness satisfies the requirements for use as a separator plate for various gas or liquid spaces.
• the surface of the carbon fiber-reinforced carbon impregnated with the duromer resin has a structure.
• the structuring enables a targeted and controlled supply of gases/liquids and the removal of any reaction products that may arise.
• the structuring can be used for water cooling of the stack structure.
• Another subject of the invention is a method for producing the separator plate comprising the following steps: a) providing a carbon fiber textile b) impregnating the carbon fiber textile with a carbon donor c) high-temperature treatment under an inert gas atmosphere of the impregnated carbon fiber textile at temperatures greater than 1300° C., preferably greater than 1700 °C, particularly preferably greater than 2000°C d) providing a duromer resin system e) impregnating the carbon fiber-reinforced carbon obtained in step c) with the duromer resin system provided in step d) f) curing and pressing the resin-impregnated carbon fiber-reinforced carbon from step e ) under a pressure of 1-50 bar
• a carbon donor in step b) is understood as meaning a resin with a carbon yield of greater than 20% by weight, and this can additionally be filled with carbon, graphite or carbon black.
• An inert gas atmosphere is understood to mean a nitrogen or argon atmosphere. Impregnation steps b) and e) can be carried out on one or both sides. The impregnation with the duromer resin system, curing and pressing in steps e) and f) increases the tightness and the mechanical strength of the carbon-reinforced carbon, which is why the separator plate can be made very thin.
• the surface can be activated by grinding, blasting, chemical treatment or plasma treatment on both sides. Activation can remove any electrically insulating layer (resin layer) present on the separator plate.
• 0% by weight to 40% by weight, preferably 5% by weight to 20% by weight, particularly preferably 8% by weight to 15% by weight, are present in the duromer resin system.
• the conductivity and the tightness can be further increased or improved by the fillers.
• the pressing step is advantageously carried out using a structured tool.
• a tool is understood to mean an embossing roller, forming roller or plate. Forming is achieved by pressing with a structured tool.
• the pressing step allows the duromer resin system to penetrate further into the interior of the carbon fiber textile, whereby the fillers, depending on the size of the particles, can remain mainly on the surface, so that a concentration gradient is formed.
• the separator plate has a concentration gradient in cross section, which decreases on both sides of the separator plate from the outside to the inside of the separator plate.
• the concentration gradient depends on the type of filler and in particular on the particle size. Because the fillers remain predominantly on the surface, the conductivity can be improved and the contact resistance can be reduced, and the tightness of the separator plate can be further increased.
• the process can be carried out as a continuous or batch process.
• the continuous process is advantageous.
• Another subject is the use of the separator plate for redox flow batteries or fuel cells or as an electrode for electrostatic air cleaning devices.
• FIG. 1 Separator plate (4) comprising a monolayer of carbon fiber reinforced carbon (1) with a duromer resin (2)
• FIG. 2 Separator plate (4) comprising a monolayer of carbon fiber reinforced carbon (1) with a duromer resin (2) and fillers (3)
• Figure 3 Separator plate (4) comprising a monolayer of carbon fiber reinforced carbon (1) with a duromer resin (2) and fillers (3)
• FIG. 5 shows a micrograph of a separator plate according to the invention
• Diagram 1 Volume resistance as a function of the surface pressure
• FIG. 1 shows a separator plate (4) comprising a monolayer of a carbon fiber-reinforced carbon (1) which is impregnated with a duromer resin (2).
• FIG. 2 shows a separator plate (4) comprising a monolayer of a carbon fiber-reinforced carbon (1), which is impregnated with a duromer resin (2) and has fillers (3). Due to the nature of the fillers, a concentration gradient occurs which ensures that the fillers only penetrate very little into the interior of the porous carbon fiber-reinforced carbon (1).
• Figure 3 shows a separator plate (4) comprising a monolayer of carbon fiber-reinforced carbon (1), which is impregnated with a duromer resin (2) and has fillers (3), due to the different particle sizes of the filler, smaller particles penetrate further into the interior of the carbon fiber reinforced carbon material (1) than larger.
• FIG. 4 shows an SEM image of a porous carbon fiber-reinforced carbon (1) prior to sealing with the duromer resin system.
• the carbon binder bridges between the carbon fibers are clearly visible.
• the combination of fiber and binder bridge creates the continuous conductive network.
• FIG. 5 shows a micrograph of a separator plate according to the invention, with the outer regions having an accumulation of filler and the filler concentration being lower on the inside.
• Diagram 1 shows the volume resistance as a function of the surface pressure.
• the initially high volume resistance (with low surface pressure) not only represents the pure material resistance, but also reflects a considerable proportion of contact resistance.
• the contact resistance decreases and the measured volume resistance is dominated by the material resistance contribution.
• surface pressures in the range of 1-1.5 MPa a stationary volume resistance level is almost reached.
• a surface pressure level of 1 MPa roughly corresponds to the real application conditions in a fuel cell stack.
• Diagram 1 shows embodiment 1 together with a reference measurement of the external GDL (gas diffusion layers). You can see that the additional material layer of the separator plate only has a small part in the total resistance of the sandwich layer structure with 2 GDL layers.
• a separator plate can be produced as described below.
• the resulting hardened separator plate is measured in a layer sandwich analogous to the arrangement in a fuel cell between two gas diffusion layers (GDL 22BB; SIGRACET ® ).
• the volume resistance R z is calculated using the following formula:
• AU is the voltage between the electrodes
• A is the area of the sample
• AI is the current.
• the electrodes are coated with gold to avoid possible contact resistance caused by oxidized surfaces.
• different contact pressures from 5 psi (US unit) to 1.5 MPa are applied and the layer thickness is determined simultaneously.
• a reference measurement was carried out with only 2 GDL 22BB layers. Since the material resistances add up in this series circuit, the material resistance of the sample can be determined as the difference between the resistance of the GDL 22BB/Probe/GDL 22BB layer structure and the reference measurement of two GDL 22BB layers.
• the permeation coefficient is measured according to DIN 51935:2019-06.
• the strength was determined using tensile strength tests based on DIN EN ISO 13934-1:2013-08. While in the standard-compliant test, beams with a length of 160 mm and a consistently constant width of 50 mm are used as test specimen geometry, in deviation from this, a tapered specimen geometry was used which, with the same length in the free crack length, also has a width of 50 mm, but has a width of 80 mm in the clamping area in order to avoid failure within the clamping area.
• the geometric density was determined by weighing a circular sample with a diameter of 50 mm.
• the monolayer of a carbon fiber-reinforced carbon can be produced, for example, as described in EP1369528B1.
• the volume resistance at 1 MPa compression is 7.8 mOhm cm 2 .
• the permeation coefficient is 2.2 * 10 -6 cm 2 /s.
• the thickness of the separator plate obtained in this way is 210 ⁇ m (measured at a 5 psi load).
• the geometric density is 1.14 g/cm.
• the tensile strength is 47 MPa.
• the volume resistance at 1 MPa surface pressure is 7.7 mOhm cm 2 .
• the permeation coefficient is 1.4 * 10 ⁇ 5 cm 2 /s.
• the thickness of the separator plate thus obtained is 200 ⁇ m (measured at 5 psi load).
• the geometric density is 1.18 g/cm 3 .
• the tensile strength is 39 MPa.
• the thickness of the separator plate obtained in this way is 202 ⁇ m (measured at a load of 5 psi) and the geometric density is 1.04 g/cm 3
• the 10% by weight is made up of conductive carbon black (Super P from Imerys) and expanded graphite (Sigratherm® GFG5 from SGL Carbon) in a ratio of 70:30.
• the coated monolayer is then cured in a hot press at a pressure of 32.5 bar and 130° C. for 60 minutes.
• the volume resistance at 1 MPa surface pressure is 6.2 mOhm cm 2 .
• the permeation coefficient is 2.2*10 6 cm 2 /s.
• the thickness of the separator plate thus obtained is 220 ⁇ m (measured at 5 psi load) and the geometric density is 1.18 g/cm 3 .
• a monolayer of carbon fiber reinforced carbon (1) with a thickness of 225 ⁇ m (measured at 5 psi load) (commercially available from SGL Carbon GmbH with the designation GDL 36 AA; SIGRACET ® ) is coated on one side with a 180 ⁇ m thick epoxy resin film (2), 10% by weight of fillers being dispersed in the epoxy resin.
• the 10% by weight is made up of conductive carbon black (Super P from Imerys Graphite & Carbon) and expanded graphite (Sigratherm® GFG5 from SGL Carbon) in a ratio of 30 to 70.
• the coated monolayer is then cured in a hot press at a pressure of 32.5 bar and 130° C. for 60 minutes.
• the volume resistance at 1 MPa surface pressure is 8 mOhm cm 2 .
• the permeation coefficient is 3.7 *10 - 6 cm 2 /s.
• the thickness of the separator plate obtained in this way is 208 ⁇ m (measured at 5 psi load) and the geometric density was determined to be 1.04 g/cm 3 .
• the volume resistance at 1 MPa compression is 5.4 mOhm cm 2 .
• the permeation coefficient is 3.9 *10 _6 cm 2 /s.
• the thickness of the separator plate obtained in this way is 205 ⁇ m (measured at a load of 5 psi) with a geometric density of 1.15 g/cm 3

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
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• Engineering & Computer Science (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Manufacturing & Machinery (AREA)
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• Composite Materials (AREA)
• Materials Engineering (AREA)
• Fuel Cell (AREA)
• Cell Separators (AREA)
• Electrostatic Separation (AREA)

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• 2021
  • 2021-03-31 DE DE102021203265.6A patent/DE102021203265B3/de active Active
• 2022
  • 2022-03-22 KR KR1020237036855A patent/KR20230162051A/ko active Pending
  • 2022-03-22 CN CN202280025389.8A patent/CN117083736A/zh not_active Withdrawn
  • 2022-03-22 CA CA3215445A patent/CA3215445A1/en active Pending
  • 2022-03-22 JP JP2023560707A patent/JP7691514B2/ja active Active
  • 2022-03-22 US US18/553,375 patent/US20240178411A1/en active Pending
  • 2022-03-22 WO PCT/EP2022/057454 patent/WO2022207405A1/de not_active Ceased
  • 2022-03-22 EP EP22718086.6A patent/EP4315459A1/de active Pending
  • 2022-03-28 TW TW111111670A patent/TW202306224A/zh unknown

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