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
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
• • 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
  • H01M4/88—Processes of manufacture
  • H01M4/8803—Supports for the deposition of the catalytic active composition
  • H01M4/8807—Gas diffusion layers
• • 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
  • H01M4/88—Processes of manufacture
  • H01M4/8803—Supports for the deposition of the catalytic active composition
  • H01M4/881—Electrolytic membranes
• • 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
  • H01M4/88—Processes of manufacture
  • H01M4/8825—Methods for deposition of the catalytic active composition
  • H01M4/8828—Coating with slurry or ink
• • 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
  • H01M4/88—Processes of manufacture
  • H01M4/8825—Methods for deposition of the catalytic active composition
  • H01M4/8828—Coating with slurry or ink
  • H01M4/8835—Screen printing
• • 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
  • H01M4/88—Processes of manufacture
  • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
  • H01M4/8882—Heat treatment, e.g. drying, baking
• • 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
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
  • H01M2004/8689—Positive 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
  • H01M8/10—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 fuel cells, in particular but not exclusively to fuel cells of the electrolyte type in the form of a polymer membrane (that is to say of the PEFC type for Polymer Electrolyte Fuel Cell).
• This invention relates more particularly to methods of manufacturing a membrane-electrode assembly for a fuel cell.
• Fuel cells are used as a source of energy in a variety of applications, including electric vehicles.
• PEFC polymer membrane electrolyte
• hydrogen is supplied to the anode of the fuel cell and oxygen is supplied as an oxidant to the cathode.
• PEFC polymer membrane fuel cells
• MEA membrane electrode assembly
• a membrane-electrode assembly (MEA) is sandwiched between a pair of electrically conductive elements, called bipolar plates, by means of gas diffusion layers, made for example of carbon fabric.
• Bipolar plates are generally rigid and thermally conductive.
• a fuel cell is thus formed by an MEA, including the gas diffusion layers, and two bipolar plates.
• a fuel cell can include a single cell or a plurality of cells formed as a stack of plates.
• a stack is thus made up of several individual cells connected in series.
• a fuel cell is powered by a fuel which is hydrogen which is supplied to the anode and by an oxidizer which is oxygen or air which is supplied to the cathode.
• the proton exchange membrane is in the form of a very thin film and is made, for example, from a sulfonated perfluorinated polymeric material.
• the anode and cathode side catalysts include finely divided catalytic particles, which are generally supported by carbon particles and mixed with a proton-conducting resin, such as an ionomer or a mixture of ionomers and with a solvent.
• the catalytic particles are generally particles of expensive precious metals, such as platinum.
• the catalysts are generally in the form of a liquid catalytic ink.
• This catalytic ink is deposited directly on a support of the MEA assembly, for example by spraying, by screen printing or by coating and spreading using a scraper.
• the catalytic ink can also be deposited indirectly on one or more constituents of an MEA by being transferred from another support impregnated with ink.
• a first method consists in coating each diffusion layer of gas with catalytic ink and is known under the name CCB (for catalyst coated backing) and then applying them on either side of a polymer membrane.
• the performance of a fuel cell from which the MEA was obtained by this method is generally low.
• hot pressing around 130 ° C
• a second method which gives better results in terms of fuel cell performance consists in coating with liquid catalytic ink the two faces of the polymer membrane and is known under the name CCM (for catalyst coated membrane).
• the membrane has a strong reactivity to organic or aqueous solvents which make up the catalytic ink and, therefore, it has a strong tendency to shrink and to wrinkle as soon as it comes into contact with the ink.
• Document EP 1 387 422 describes another method for applying a coating based on a catalytic ink on a gas diffusion layer or on a polymer membrane. of a fuel cell. This process comprises several successive steps consisting in applying, then leveling and drying the coating, each step being carried out under strict conditions of temperature, humidity and treatment time. Thus, by multiplying the stages and by imposing on them very severe conditions, this process proves to be complex to carry out.
• An objective of the invention is to remedy the drawbacks of the aforementioned documents and to provide an original solution for a method of manufacturing an assembly
• MEA membrane electrode
• a membrane-electrode assembly for a fuel cell comprising a polymer membrane proton exchange, catalytic layers and a first and a second gas diffusion layer, the method comprising the following steps:
• the coating formed in step a) corresponds to the cathode part of the membrane.
• the cathode side of the catalytic coating is that which comes into contact with oxygen (or compressed air), it has characteristics in terms of deposition which are directly linked to the performance of the fuel cell.
• this coating on the cathode side has a thickness of the coating less than that on the anode side and it must be well in contact with the membrane to guarantee the performance of the cell.
• the gas diffusion layer comprising the coating of catalytic ink can be applied by simple pressure, without heating, which avoids
• the membrane and the gas diffusion layers can be obtained by cutting steps to pre-established dimensions before step c).
• the coating of catalytic layer according to the invention can be obtained by a process for the direct deposition of a catalytic ink on one of the faces of the membrane and on one of the faces of the gas diffusion layer by a process included in the group
• the coating deposition step according to the invention can be followed by a drying step. Drying can be done using a forced air flow heated to a temperature accepted by the membrane material, generally less than or equal to 100 ° C.
• the method of the invention may include an additional step of bonding on the rim of each of the faces of the membrane of a reinforcement carrying a seal.
• step c) the assembly of step c) can be done by gluing.
• the invention also relates to an assembly line for carrying out the implementation of the method of manufacturing an electrode membrane assembly according to the invention.
• the object of the invention is also achieved with a fuel cell comprising at least one cell comprising an electrode membrane assembly of the invention sandwiched between two bipolar plates.
• FIG. 1 is a schematic view of an assembly line which performs the implementation of the method of the invention
• - Figure 2 is a graphical representation of the performance of a fuel cell obtained with the method of the invention compared to that of a fuel cell of the prior art
• - Figure 3 is a perspective view of part of a membrane-electrode assembly obtained with the method of the invention.
• FIG. 1 schematically illustrates an assembly line 1 which makes it possible to obtain a membrane-electrode assembly (MEA) 100 with the method of the invention.
• a membrane-electrode assembly 100 generally comprises a membrane 10, two catalytic layers 20, 30 forming electrodes arranged on either side thereof, and a gas diffusion layer 40, 50 arranged opposite each electrode.
• the membrane 10 is in the form of a very thin film of a proton-conducting polymer called an ionomer.
• a proton-conducting polymer called an ionomer.
• Such an ionomer is for example Nafion® N1 17 and is delivered by its manufacturer in the form of a film roll.
• the film is a strip a few tens of pm thick, a few tens of cm wide and a few meters long.
• the film is wound on a reel while being supported on an interlayer (or sometimes it is disposed between two interleaves) which can be a polyester film.
• the electrodes are porous structures obtained by depositing and drying a catalytic ink on a support.
• the catalytic ink preferably contains particles of a catalyst of nanometric size (for example between 1 and 10 nm) supported or not by carbon particles of larger size (for example between 10 and 100 nm).
• the catalyst may be platinum, platinum / ruthenium or another element or group of elements chosen from the group of platinum of the periodic table.
• the ink further comprises a binder, such as an ionomer (for example Nafion®), a solvent (for example water, glycerol, etc.). Additives can be added to the formulation, for example a surfactant.
• the ink generally in the liquid state, is deposited on the support and dried so as to obtain a catalyst charge of approximately 0.1 to 0.2 mg / cm 2 .
• a gas diffusion layer 40, 50 or GDL is a porous medium to allow the transport of the reactant from its entry towards the catalyst. It must also be electrically conductive to conduct the charges.
• Such a gas diffusion layer is thus advantageously made from carbon fibers which are woven or knitted together or are in the form of a non-woven fabric.
• One can also treat such a gas diffusion layer for example by applying a micro coating made of PTFE and carbon particles) so that it is hydrophobic in order to better channel the water which results from the reaction within the battery.
• the gas diffusion layers used are of the type used in the manufacture of fuel cells. They are generally delivered in the form of a roll by their manufacturer.
• a first electrode is formed by applying a coating or catalytic layer 20 obtained based on a catalytic ink 60 on a first face 14 of the membrane 10, the opposite face 15 being supported by an interlayer 12.
• the first electrode or catalytic layer 20 is that corresponding to the cathode side of the membrane.
• direct deposition methods for example by coating with a roller or scraper, or by flexography, or even by spraying, can be used to apply the ink to the film constituting the membrane.
• An indirect deposition method for example by pad printing using a PTFE transfer buffer can also be used.
• the coating application step is followed by a drying step.
• This step can be done by exposing the film to ambient air for a predetermined period of time or using a flow of blown air, optionally heated to a temperature accepted by the material of the membrane, generally less than or equal to 100 ° C. to reduce the drying time of the coating.
• the interlayer 12 is separated, which is driven using a motorized roller 18 and wound around a reel 17 for recycling.
• the film 11 covered with a coating formed by the first catalytic layer 20 is brought by a transfer device, which can be a movable head comprising a bar engaging the end of the film (not shown), which ensures the movement of the film until it is placed near a first cutting device 70 (which may be a knife or laser cutting device) which cuts the outline of the membrane 10.
• a transfer device which can be a movable head comprising a bar engaging the end of the film (not shown), which ensures the movement of the film until it is placed near a first cutting device 70 (which may be a knife or laser cutting device) which cuts the outline of the membrane 10.
• the film 11 coated with catalytic ink is wound on a reel before cutting the membrane, the film being tensioned in this case using intermediate tensioning rollers .
• FIG. 3 schematically illustrates a sub-assembly formed by the membrane 10 covered with the catalytic layer 20 which is integral with a reinforcement 21 provided with a silicone seal 23.
• the reinforcement 21 includes cutouts 22 allowing communication through the various assemblies and a seal 23 deposited by screen printing and which provides sealing around the periphery of the membrane and cutouts of the reinforcement.
• a second electrode is formed by applying a coating or catalytic layer 30 from a catalytic ink 60 on a first face of the first gas diffusion layer 50.
• the second electrode corresponds to the anode side of the cell fuel.
• a roll 59 of media 51 is unwound forming a gas diffusion layer (GDL) wound around a hub 53.
• GDL gas diffusion layer
• the hub 53 is rotated around its axis, for example using a motor (not shown).
• a coating of catalytic ink 60 is then applied directly to a first face 54 of the media 51 of the gaseous diffusion layer from an ink tank 61 by a direct deposition process, for example by screen printing.
• the opposite face 55 of the media 51 is not covered.
• Other direct deposition methods for example by coating with a roller or scraper, or by flexography, or even by spraying can be used to apply the ink to the gas diffusion layer (GDL).
• An indirect deposition method for example by pad printing using a PTFE transfer buffer can also be used.
• the coating application step is followed by a drying step. This step can be done by exposing the media to ambient air for a predetermined period or using a flow of blown air, possibly heated to around 100 ° C to reduce the drying time of the coating.
• the media 51 forming a gas diffusion layer of the roller 59 covered with the second coating layer 30 is then brought in by a transfer device, which can be a movable head comprising a bar engaging the end of the media (not shown ), which ensures its movement until it is placed near a second cutting device 80 (which can be a knife or laser cutting device) which cuts the outline of the gas diffusion layer 50.
• a transfer device which can be a movable head comprising a bar engaging the end of the media (not shown ), which ensures its movement until it is placed near a second cutting device 80 (which can be a knife or laser cutting device) which cuts the outline of the gas diffusion layer 50.
• the media 51 of gas diffusion layer coated with catalytic ink is wound on a coil before cutting to the dimensions of the gas diffusion layer 50, the media being tensioned in this case at using intermediate tensioning rollers.
• a second roll 49 of media 41 of gas diffusion layer GDL is unwound, tensioned and brought near a third cutting device 90 which cuts the outline of the second gas diffusion layer 40.
• the last step in the process involves assembling the MEA components.
• the uncovered face of the membrane 10 is brought into contact with the face covered with catalytic ink forming the electrode 30 of the first gas diffusion layer 50 and the coated covered face forming the electrode 20 of the membrane. 10 with one face of the second gas diffusion layer 40.
• the assembly of all the layers can be done by bonding, for example by bonding the two gas diffusion layers 40 and 50 on either side of the subassembly of Figure 3. Such bonding can be done for example by hot pressing, applying pressure to all of the layers and heating at the same time.
• a MEA thus obtained is sandwiched between two bipolar plates to form an elementary cell of a fuel cell. It is then possible to produce a stack of several elementary cells as a function of the power sought for the fuel cell. The stack thus obtained is then closed by end plates and it is connected to the various circuits which ensure the operation of the fuel cell.
• the graph in FIG. 2 shows, by spaced lines (triangle-shaped beacon), the performance of a fuel cell of the state of the art in which the membrane-electrode assembly (MEA) is carried out by the CCM method, judged as that giving the best results.
• the same graph also shows, by dotted lines (square-shaped beacon), the performance of a fuel cell of the invention in which the membrane-electrode assembly was obtained with the method of l invention (CCMix in Figure 2).
• the other components of the fuel cell are identical (including their materials, catalytic ink, etc.), as well as the assembly of the stack and the aging of the cells. It can be seen from this graphical representation that the performances of the two fuel cells are very close. A fuel cell is thus obtained having good operating performance, while using an easier manufacturing process.
• the deposition of catalytic ink on the membrane or on the gas diffusion layer can be done by other methods, such as extrusion, calendering or physical vapor deposition.
• the method of the invention can be used to cover with a catalytic layer a membrane and a gas diffusion layer previously cut (in the form of sheets).

Applications Claiming Priority (3)

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• 2018
  • 2018-12-07 FR FR1872533A patent/FR3089694A3/fr active Pending
• 2019
  • 2019-02-01 FR FR1900983A patent/FR3089693B1/fr active Active
  • 2019-12-09 CN CN201980087949.0A patent/CN113366676A/zh active Pending
  • 2019-12-09 US US17/299,912 patent/US20220037690A1/en active Pending
  • 2019-12-09 EP EP19842798.1A patent/EP3891827A1/de not_active Withdrawn

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