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
  • H01M8/0243—Composites in the form of mixtures
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/14—Making cellulose wadding, filter or blotting paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/44—Watermarking devices
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/006—Making patterned paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/06—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the cylinder type
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/06—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the cylinder type
  • D21F11/08—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the cylinder type paper or board consisting of two or more layers
• • 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

• Green paper to produce a gas diffusion layer for a fuel cell
• the invention relates to a green paper for producing a gas diffusion layer (GDL) for a fuel cell.
• the invention further relates to a method for producing a green paper for producing a gas diffusion layer (GDL) for a fuel cell.
• a fuel cell of the Proton Exchange Membrane Fuel Cell (PEMFC) type also referred to as a polymer electrolyte fuel cell
• the gas distribution is carried out via a so-called bipolar plate (BPP) and the gas diffusion layer (GDL) to the membrane coated with catalytic platinum (also known as GL or Catalyst Layer) is reached.
• BPP bipolar plate
• GDL gas diffusion layer
• MEA membrane-electrode assembly
• the fuel cell produces electricity, water vapor and heat through the catalytic oxidation of hydrogen and oxygen.
• a GDL made of a fiber material such as carbon fibers, and a coated BPP made of steel have become established for the automotive sector.
• the fiber material can be designed as a textile fabric/knitted fabric or as a fiber mat produced by paper technology, which is known, for example, from DE 102008 042415 B3. It can also consist of two layers, a fine layer bordering the CL and a coarser layer bordering the BPP and flow field.
• the fiber mat produced by paper technology is referred to as green paper or sintered paper, which is debindered and/or sintered in one of the following work steps and thus further processed into a GDL.
• a particular disadvantage of the production of GDLs based on carbon fibers is that carbon fibers and their further processing are associated with relatively high costs. Furthermore, carbon fibers are pressure sensitive, which can lead to fiber breakage, which can then potentially injure the CL/PEM. Furthermore, the carbon fibers can bulge or swell, entering the channels of the BPP, reducing gas and water flow and reducing fuel cell efficiency. Furthermore, the porosity of the GDL can only be adjusted to a limited extent and at least two additional work steps are necessary for a two-layer GDL with a combination of coarse and fine porosity.
• the flow field must be formed entirely by the BPP because a GDL known from the prior art does not offer any possibility for structuring.
• the BPP has to be embossed or the green paper has to be processed in order to achieve a gas distribution structure or a structuring for the flow field. This is usually a separate, time-consuming work process.
• the invention is therefore based on the object of developing a generic green paper for producing a gas diffusion layer (GDL) for a fuel cell and a generic method for producing a green paper for producing a gas diffusion layer (GDL) for a fuel cell in such a way that that the disadvantages of the prior art are eliminated.
• GDL gas diffusion layer
• GDL gas diffusion layer
• the green paper has at least one first paper web into which at least one watermark has been introduced.
• the watermark forms the structuring for the flow field or the gas distribution structure of the gas diffusion layer (GDL) produced from the green paper.
• the first paper web is particularly preferably mixed with metal powder and/or metal fibers.
• the final GDE is created after debinding, sintering, coating, deposition of atomic layers (AED - atomic layer deposition) and, if necessary, further process steps.
• the invention further relates to a method for producing a green paper for producing a gas diffusion layer (GDL), in which at least a first paper web preferably mixed with metal powder and/or metal fibers is produced, into which at least one watermark is introduced.
• GDL gas diffusion layer
• This paper web is then processed into the final GDL by debinding, sintering, coating, deposition of atomic layers (ALD - atomic layer deposition) using the thermal ALD method and, if necessary, further process steps.
• the GDL consists almost exclusively of a metal framework.
• the porosity of the metal structure depends in particular on the fiber density of the paper webs, the (grain) size of the metal powder and/or metal fibers and added additives.
• the subsequent flow field is integrated into the green paper without a separate operation by integrating a corresponding watermark into the watermark position on the cylinder mold of a paper machine.
• Any desired shape and gradation of the flow field channels can be achieved without any special effort by the design-dependent structuring of the watermark screen with the associated thickness modulation of the paper.
• a high-resolution or multi-level or multi-level watermark can also be used, as is known, for example, from EP 1432868 A1 or WO 2014/040706 A1.
• a watermark in the sense of this invention, is a true watermark where the thickness of the paper varies but the density of the paper does not vary. In this case, the paper has areas that are thicker and/or thinner than the adjacent areas, the density of the paper being the same in all areas.
• Such a watermark can either be introduced into the paper web during papermaking, for example by indentations or elevations being introduced into a cylinder mold, on which more or fewer paper fibers accumulate when the paper is scooped out of the pulp. However, it can also be subsequently introduced into the paper web by removing parts of the paper, for example mechanically by milling or by lasering.
• a fake watermark is also possible, in which the still wet paper web is embossed by an embossing process after the paper web has been removed from the cylinder mold, for example.
• a watermark is also referred to as a dandy roll watermark. Embossing reduces the thickness of the paper while increasing the density of the paper. The paper fibers are thus compacted or pressed together. This compression has the advantage that it prevents too much gas from diffusing through the GDL in the front area of the channel in the direction of the catalyst layer (CL), thus ensuring a more even gas distribution.
• a real watermark and a fake watermark can particularly preferably be combined with one another, for example by forming parts of a watermark with a real watermark and other parts with a fake watermark.
• the green paper consists of a first paper web and at least one second paper web.
• the green paper is formed from the first paper web and at least one second paper web.
• the second paper web is brought together with the first paper web while it is still wet and firmly connected.
• the second and/or each additional paper web can also have a watermark.
• the first and/or at least one second paper web can be produced in a cylinder mold paper machine.
• the first and/or the at least one second paper web can also be produced in a short former, in which the paper pulp is sprayed onto a cylinder mold.
• These production methods are for the production of security documents or documents of value, such as banknotes or identity cards, from WO 2006/099971 A2 are known and are also preferred methods according to the invention for producing a GDL from at least one paper web.
• the green paper highly filled with metal powder and/or metal fibers is produced in one operation, which, according to DE 10 2008 042415 B3, is processed with at least two different recipes to form a combined green paper with different properties.
• this is a thin layer with fine pores and a thicker layer with coarser pores.
• the porosity can also vary between two paper webs.
• the green paper consists of two paper webs, each of which has a watermark, with the structures of the watermark on the first paper web and the watermark on the second paper web not being identical, but being exactly mirror-symmetrical in terms of area and in the direction of the material thickness .
• the structures of the watermark of the first paper web are 180° out of phase with the structures of the watermark of the second paper web. This means that when the first paper web and the second paper web are joined together with their side structured by the watermark, the elevations of the first paper web coincide with the depressions of the second paper web.
• This embodiment has the particular advantage that the first and the second paper web can have different porosities after sintering.
• the first paper web facing the membrane has a lower porosity of 20% to 75% after sintering, and the second paper web has a higher porosity of 30% to 90% after sintering, so that the second paper web hardly than Resistance for the gas, but only acts as a spacer to the bipolar plate.
• optimal gas Distribution can be combined with optimal stackability and optimally even distribution of mechanical pressure over the entire PEM membrane.
• a micro-porous layer (MPL) is particularly advantageously located between the first paper web and the membrane, which has a fine surface with little roughness and smaller pores than the first and second paper web.
• the first paper web has a higher density than the second paper web.
• the first paper web has, for example, a density of 3 g/cm 3 to 10 g/cm 3
• the second has a density of 1 g/cm 3 to 5 g/cm 3 .
• the first paper web is particularly preferably formed by a finer paper fiber pulp than the second paper web, which accordingly leads to finer pores in this partial area of the sintered paper.
• the thickness of the first paper web is preferably 5 ⁇ m to 50 ⁇ m, particularly preferably 10 ⁇ m to 20 ⁇ m, and that of the second paper web is 50 ⁇ m to 400 ⁇ m, particularly preferably 80 ⁇ m to 200 ⁇ m.
• the watermark is designed as a depression in the form of at least one channel, the channel serving for the passage of gas, ie the fuel or the oxygen.
• This channel is preferably designed to meander over the surface of the paper web.
• several channels, in the form of a lattice or in the form of rays, with connecting channels in the form of segments of a circle, are also possible.
• Additional channels for the transport of water can also be introduced in one or more of the paper layers according to one of the methods described above. These ensure balanced water transport and have the particular advantage that the PEM cell is neither flooded nor dried out, since both have a negative effect on the efficiency of the cell. On the other hand, water channels can also be used for the sustainable cooling of the cell.
• structuring is introduced into the surface of the green paper or the sintered green paper by means of lasers.
• a laser beam can be used, for example, to introduce deeper structures or structures with steeper flanks, or that already existing structures can be deepened or provided with steeper flanks.
• lasering can also be carried out in one or more former layers in order to introduce structures or channels into the intermediate layer between the watermark and the former layer and thus improve the gas distribution even further.
• the gases are coupled into the GDL in the middle of the bipolar plates (based on the top view of the bipolar plates) and then via various watermark structures and/or channels of the GDL to the outside or to the outer edge of the GDL to be distributed.
• the watermark structures and/or channels can, for example, radiate or spiral outwards from the center of the GDL, which can be supplemented by concentrically arranged ring-shaped watermark structures and/or channels.
• the GDL usually has an area of 300 cm 2 to 350 cm 2 and is between 100 gm and 300 gm thick, depending on the system and function. If the function of the flow field is integrated into the GDL, the thickness of the GDL can also be greater. The depth of the channels is up to 350 gm. Since that GDL must also have a certain compressibility and at the same time conduct the current between the individual cells, the GDL with forming layer and cylinder wire layer has a thickness of 100 gm to 400 jun and the BPP must be designed as smooth sheet with a thickness of 75 jun or less. Since the BPP usually also assumes a cooling function for the fuel cell, the BPP can then also be designed as a composite sandwich that has a porous or channel-like passage for coolant. Alternatively, the cooling channels can also be integrated into the GDL or MEA.
• the BPP has a simplified flow field structure and a partial flow field is additionally generated in the GDL.
• the former layer is designed thin so as not to take up too much space.
• the cell pitch is preferably 0.8 mm to 1 mm, since about 400 cells are stacked one on top of the other for a 120 kW fuel cell in a motor vehicle application.
• the fine former layer preferably has a thickness of between 5 ⁇ m and 50 ⁇ m.
• the former preferably has a proportion of 2% to 40% in the total GDL.
• fiducial marks, positioning aids, centering aids and attachments for openings are generated with the aid of high-resolution or multi-level or multi-level watermarks.
• This advantageously simplifies the further processing of the GDL to form the fuel cell stack, since, for example, with the aid of transmitted light/reflected light image processing systems, precise positioning of the GDL relative to the other components, such as BPP or GL, is possible.
• the structures of the GDL on the anode side and on the cathode side are not identical, but are exactly mirror-symmetrical in terms of area and in the direction of the material thickness.
• the structures of the anode side GDL are 180° out of phase with the structures of the cathode side GDL. This means that if an anode GDL is placed flow field side on the flow field side of a cathode GDL, the peaks of one GDL will exactly coincide with the valleys of the other GDL.
• the combination of two 3D mirror-symmetrical anode/cathode GDLs results in an exactly flat piece of green paper when placed one on top of the other. This embodiment has the advantage that the green paper can be compacted with any mechanical pressure without losing its channel structure.
• anode GDL and the cathode GDL can have different porosities.
• every second anode/cathode pair in the stack or every second stack can be equipped with 3D mirror-symmetrical GDLs.
• the fuel cell is particularly preferably a proton exchange membrane fuel cell (PEMFC) fuel cell.
• PEMFC proton exchange membrane fuel cell
• the first paper web in the gas diffusion layer made from the green paper forms a diffusion layer for a membrane (GL) coated with catalytic metal, preferably platinum, and the second paper web forms in the gas diffusion layer made from the green paper.
• Layer a distribution layer with flow field.
• PEMEC Proton Exchange Membrane Electrolyser Cell
• electrolyzer cells or other Power to X technology.
• the paper web preferably consists, inter alia, of paper made of cellulose fibers or of cotton fibers, such as is used for banknotes, or of other natural fibers or of synthetic fibers or a mixture of natural and synthetic fibers. Furthermore, the paper web preferably consists of a combination of at least two different substrates arranged one above the other and connected to one another, a so-called hybrid. Information on the weight of the paper web used is given, for example, in document DE 10243 653 A9, the details of which are included in this application in their entirety.
• the metal-filled green paper can have a grammage of 100 g/m 2 to 1200 g/m 2 .
• All metal powders and metal fibers on a micro scale can be used as filler materials for the sintered paper, for example titanium, copper, zinc or stainless steels, as are known from DE 10 2008 042415 B3. It is important that different mixtures are used for the forming layer and the cylinder mold layer in order to achieve different porosity of the paper layers.
• the former layer is to be made finer than the cylinder wire layer. Nanopowders can also be used in the forming layer.
• a (thermal) ALD coating or other coating methods are used in one of the subsequent process steps.
• the cuts are outside the area at risk of corrosion, or the cuts are specially sealed in the further process steps for the finished cell. Otherwise, there is also the option of coating the GDL with ALD, etc. after punching and packaging.
• FIG. 1 shows a twin cylinder paper machine for producing a green paper according to the invention
• FIG. 3 shows a two-layer GDE with a meandering channel formed by a watermark and in this case on the left in a plan view and on the right in a sectional view along section AB,
• Fig. 4 the two-layer GDE from Fig. 3 supplemented by registration marks, positioning aids and centering aids,
• FIG. 5 shows a combination of two 3D mirror-symmetrical anode and cathode GDLs and in this case on the left in a top view and on the right in a sectional view along section A-B,
• Fig. 6 shows a GDL with watermark-shaped channels leading outwards from the center of the GDL, showing Fig. 6a with radial channels, Fig. 6b with radial and concentric channels, and Fig. 6c with spiral channels.
• FIG. 1 shows a schematic representation of a twin cylinder paper machine 10, as is known, for example, from WO 2006/099971 A2 for the production of security paper.
• the paper machine 10 contains two cylinder mold paper machines 12 and 14 which are connected to one another via a pick-up felt 16 .
• a paper web 20 is formed on a cylinder mold 18 in the first paper machine 12 .
• a second, homogeneous paper web 30 is produced in the second paper machine 14, removed from the cylinder mold 34 by means of the take-off felt 16 and guided to the first paper machine 12, where it is connected to the first paper web 20 in the area of the pressure roller 36.
• the interconnected paper webs 38 together form the GDL and are fed to further processing stations.
• the second paper web 30 can also be produced with a short former 40 in which the paper pulp is sprayed onto the surface of a cylinder mold 44 with a headbox nozzle 42 .
• a short former 40 in which the paper pulp is sprayed onto the surface of a cylinder mold 44 with a headbox nozzle 42 .
• Particularly thin layers of paper for example with a grammage of 15 to 25 g/m2, can be produced with such a short former.
• Fig. 3 shows schematically a two-layer GDL 1 with a meandering channel 2 formed by a watermark and in this case on the left in a top view and on the right in a sectional view along the section AB.
• the black area 3 shows the cylinder wire layer with a structured watermark as channel 2 and the patterned area 4 shows the former layer with a fine pore structure.
• the individual layers 3 and 4 can have a different basic thickness.
• a sectional profile formed by the water jet runs as a thickness modulation through the cylinder wire layer, which has a semicircular shape in the drawing.
• the large arrows show the gas inlet/outlet. The gasket around the GDL must be designed accordingly.
• FIG. 4 schematically shows the two-layer GDL from FIG. 3 supplemented by registration marks, positioning aids and centering aids.
• registration marks, positioning aids, centering aids and approaches for passages can be installed to simplify further processing of the GDL into the fuel cell stack. This ensures that, e.g. with the help of transmitted light/reflected light image processing systems, the GDL can be precisely positioned relative to the other components such as BPP or GL.
• the lines 5 are intended, for example, to represent cutting marks for the GDL implemented as highlight watermarks, and the circles 6 are intended to represent centering/positioning aids. These can of course be introduced in any form. HD watermark laser screens could also be used.
• FIG. 5 shows a schematic of a combination of an anode GDL 7.1 and a 3D mirror-symmetrical cathode GDL 7.2 formed thereto and in this case top left in a plan view of the surface of the anode GDL 7.1, bottom left in a plan view of the surface of the cathode GDL 7.2 and right each in a sectional view along section AB.
• the elevations and depressions of the green paper or of the finished GDL that are generated by the watermark and form flow field channels 8.1 and 8.2 can be restored by pressing and other mechanical loads injured, pushed back or even equalized, so that channels 8.1 and 8.2 can no longer be fully effective.
• the anode GDL 7.1 and the cathode GDL 7.2 can have different porosities.
• the anode GDL 7.1 can have a porosity of 20% to 75% and the cathode GDL 7.2 has a porosity of 30% to 90%, so that the cathode GDL 7.2 hardly serves as a resistance for the gas, but only as a spacer bipolar plate works.
• Fig. 6 shows three embodiments in plan view, in which the gases are coupled into the GDL in the middle of the bipolar plates (not shown) and then flow to the outside or to the GDL via various watermark structures and/or channels of the GDL. distributed towards the outer edge of the GDL.
• the channels of the watermark structures radiate out from the center of the GDL.
• the gases are supplied via the circular opening in the middle of the GDL, the areas shown in black represent the areas of the watermark, which have a higher GDL thickness than the areas of reduced GDL thickness shown in white that form the channels.
• FIG. 6b shows an exemplary embodiment in which radial channels of the watermark structures are supplemented by concentrically arranged annular channels, resulting in a structure similar to a spider's web.
• the gases are supplied via the circular opening in the middle of the GDL.
• the areas shown in black represent the areas of the watermark that have a greater thickness of the GDL than the areas shown in white with a reduced thickness of the GDL that form channels.
• FIG. 6c shows an embodiment in which the channels of the watermark structures are spirally formed, starting from the center of the GDL.
• the gases are supplied via the circular opening in the middle of the GDL.
• the areas shown in black represent the areas of the watermark that have a greater thickness of the GDL than the areas shown in white that have a reduced thickness of the GDL form channels.

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• Chemical & Material Sciences (AREA)
• Sustainable Energy (AREA)
• Electrochemistry (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
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• Composite Materials (AREA)
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• Life Sciences & Earth Sciences (AREA)
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• Paper (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

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• 2020
  • 2020-09-07 DE DE102020005480.3A patent/DE102020005480A1/de not_active Withdrawn
• 2021
  • 2021-08-31 JP JP2023514853A patent/JP7787159B2/ja active Active
  • 2021-08-31 PL PL21769890.1T patent/PL4211306T3/pl unknown
  • 2021-08-31 KR KR1020237008006A patent/KR20230095920A/ko active Pending
  • 2021-08-31 WO PCT/EP2021/025327 patent/WO2022048794A1/de not_active Ceased
  • 2021-08-31 ES ES21769890T patent/ES2987076T3/es active Active
  • 2021-08-31 CN CN202180054285.5A patent/CN116075612A/zh active Pending
  • 2021-08-31 EP EP21769890.1A patent/EP4211306B1/de active Active
  • 2021-08-31 US US18/024,885 patent/US20230317973A1/en active Pending

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