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
  • H01M4/8605—Porous electrodes
• • 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

Definitions

• the present invention relates to a fuel cell comprising a membrane of the ion exchange type as electrolyte, and more specifically a proton exchange membrane.
• the invention relates to elementary cells for fuel cells as well as to their manufacturing methods, the elementary cells also called “electrode-membrane-electrode assemblies” conventionally comprising two electrodes between which the membrane is located. ion exchange.
• the invention finds an application in the field of fuel cells of the PEMFC type (from the English “Proton Exchange Membrane Fuel Cell”), of the DMFC type (from the English “Direct Methanol Fuel Cell” ), or of the alkaline anion exchange type.
• a fuel cell comprises a stack of elementary cells, within which an electrochemical reaction takes place between two reagents which are introduced continuously.
• the fuel such as hydrogen for cells operating with hydrogen / oxygen mixtures, or methanol for cells operating with methanol / oxygen mixtures, is brought into contact with the anode, while the oxidant, generally the oxygen, is brought into contact with the cathode.
• the two electrodes are separated by an electrolyte, of the ion exchange membrane type.
• the electrochemical reaction splits into two half-reactions: an oxidation of the fuel taking place at the anode / electrolyte interface, producing in the case of hydrogen cells protons H + , which will pass through the electrolyte towards the cathode, as well as electrons joining the external circuit, in order to contribute to the production of electrical energy; a reduction of the oxidant ' taking place at the electrolyte / cathode interface, with production of water in the case of hydrogen fuel cells.
• the electrochemical reaction takes place, strictly speaking, at the level of an electrode-membrane-electrode assembly.
• the electrode-membrane-electrode assemblies are most often arranged in the form of a stack, the electrical continuity between the different assemblies being ensured by means of conductive plates, called bipolar plates.
• bipolar plates preferably made of graphite or stainless steel, provide the electrical junction between the anode of an electrode-membrane-electrode assembly and the cathode of the adjacent assembly.
• each electrode-membrane-electrode assembly is confined between two bipolar plates, the latter also fulfilling the function of distributing the reagents to the electrodes, and being able to have cooling elements in order to cope with possible overheating of the stack.
• the fuel cells known from the prior art generally have an architecture of the “filter press” type, corresponding to a specific design in which the bipolar plates and the elementary cells have flat surfaces, assembled one on the other. the others by clamping the various elements.
• the bipolar plates comprise a network of channels winding over the entire surface in contact with the cell elementary, in order to ensure the most homogeneous distribution of reagents possible towards an electrode of the cell.
• the analyzes carried out made it possible to locate the deformations of the membrane in zones located at the level of the channels of the adjacent bipolar plates, these channels being initially intended to be taken up by the reagents.
• the deformations encountered are largely explained by the non-homogeneity of the mechanical stresses exerted on the membrane during the tightening operation, these stresses being essentially concentrated on portions of the membrane facing the solid parts of the bipolar plates separating the various channels. It is specified that when the tightening operation is completed and the elementary cell maintained in position, the deformed parts of the membrane are blocked inside these channels, thus considerably reducing the lifetime of this membrane and of the cell. associated elementary.
• the object of the invention is therefore firstly to propose an elementary cell for a fuel cell comprising two electrodes between which there is an ion exchange membrane, the cell at least partially remedying the drawbacks mentioned above relating to the embodiments of prior art. More specifically, the object of the invention is to present an elementary cell for a fuel cell whose design significantly increases the life of the ion exchange membrane. Furthermore, the present invention also aims to propose a method of manufacturing such an elementary cell.
• the object of the invention is to present a fuel cell comprising a plurality of elementary cells such as those meeting the aim of the invention mentioned above.
• the invention relates to an elementary cell for a fuel cell comprising two electrodes between which is located an ion exchange membrane.
• one of the two electrodes has a threaded surface carrying the ion-exchange membrane, the assembly formed by this electrode and the ion-exchange membrane being able to be assembled in a screwed manner on a threaded surface belonging to the other of the two electrodes.
• the elementary cell according to the invention is designed such that during assembly of the assembly formed by one of the two electrodes and the ion exchange membrane on the other of the electrodes, the exchange membrane d he ions is confined between two threaded surfaces, allowing it to be pressurized continuously as the screwing operation proceeds.
• the mechanical stresses exerted on the membrane are substantially uniformly distributed over its entire surface in contact with the two electrodes, without presenting deformed zones as was the case in the achievements of the prior art.
• the absence of significant deformations on the ion exchange membrane is partly due to the sinusoidal shape of the threads present on the threaded surfaces, these threads greatly minimizing the stress concentrations on the membrane maintained between these two surfaces.
• the implementation of such an elementary cell does not favor the creation of zones of accelerated aging on the ion exchange membrane, which advantageously allows the latter not to be cracked, and therefore to have a considerably increased service life compared to that of the embodiments of the prior art.
• the threaded surfaces of the two rigid electrodes do not allow the ion exchange membrane to have undulations when the cell comprising the cell is put into operation.
• the swelling of the membrane resulting from its impregnation with water causes it to be pressed against the electrodes, so that the contact surfaces between these electrodes and the membrane are in no way reduced. Consequently, the electrochemical reaction takes place over a large part of the membrane, thus preventing accelerated aging of certain portions of this membrane.
• an advantage of the present invention lies in the increase, compared with the embodiments of the prior art, of the exchange surfaces between the ion exchange membrane and the electrodes.
• the elementary cell according to the invention has exchange surfaces of the helical type, consequently generating a growth in the current density which can be produced.
• the ion exchange membrane has two threaded surfaces capable of cooperating respectively with the threaded surfaces of the two electrodes, all of these surfaces being produced so that they have the same pitch.
• one of the two electrodes is constituted by a coating deposited on a screw, and the other of the two electrodes is constituted by a coating deposited on a nut formed in a substrate.
• the screw and the substrate are respectively provided with at least one orifice into which at least one reagent is capable of being injected.
• the ion-exchange membrane is carried by the electrode deposited on the screw, and each orifice provided in the substrate opens directly into a space at least partially delimited by the threaded surface of the 'electrode deposited on the nut, allowing the passage of each reagent in the interstices of a helical connection between the threaded surface of the electrode deposited on the nut and the ion exchange membrane.
• the subject of the invention is also a fuel cell comprising a plurality of elementary cells such as that which is the subject of the invention and described above, the cells being electrically connected to each other and having a common substrate.
• the exchange surface can be up to approximately twenty times greater than the exchange surface of a conventional battery of the prior art, of substantially identical dimensions.
• the subject of the invention also relates to a method of manufacturing such an elementary cell for a fuel cell.
• FIG. 1 shows a schematic front sectional view of an elementary cell according to a preferred embodiment of the present invention
• - Figure 2 shows an enlarged view of part of the elementary cell shown in Figure 1
• FIG. 3 represents a partial schematic view from above of a fuel cell comprising a plurality of elementary cells, such as that shown in FIG. 1.
• FIGS. 1 and 2 we see an elementary cell 1 for a fuel cell according to a preferred embodiment of the present invention.
• the elementary cell 1 for example capable of delivering a power of between 10 and 50 k when it enters into the constitution of fuel cells of medium power, can be implemented in any type of cell such as PEMFC cells and DMFC batteries.
• the elementary cell 1 comprises a substrate 2 preferably made of a porous material, in which a nut 4 is formed having a threaded surface 6.
• the first electrode 8 can equally extend over the entire height of the threaded surface 6 of the nut 4, or only over a portion of this threaded surface 6.
• the elementary cell 1 also includes a screw 12 preferably made of a porous material.
• the pitch of the threaded surface 16 is identical to the pitch of the threaded surface 6 of the nut 4.
• the second electrode 14 can equally extend over the entire height of the threaded surface 16 of the screw 12 , or only on a portion of this threaded surface 16.
• the two electrodes 8 and 14 are deposited so that when the screw 12 is in place on the nut 4, these two electrodes 8 and 14 are opposite the one from the other and extend over an identical height.
• the ion exchange membrane 20 is elastic and of diameter slightly less than the diameter of the threaded surface 18 of the second electrode 14, so that following a screw mounting, the two threaded surfaces concerned 18 and 22 are arranged relative to each other so as to marry completely.
• the ion exchange membrane 20 is designed to extend all around the second electrode 14, but also includes an annular portion 23 connected to the part extending all around the second electrode 14, the annular portion 23 being located under the head 24 of the screw 12 of the elementary cell 1.
• the assembly formed by the screw 12, the second electrode 14, the threaded surface 18 of the second electrode 14 and the ion exchange membrane 20 is assembled in a screwed manner on the threaded surface 10 of the first electrode 8.
• the ion exchange membrane 20 is preformed so as to have a second threaded surface 26 capable of cooperate with the threaded surface 10 of the first electrode 8, in order to establish a helical connection between the first electrode 8 and the membrane 20 of the elementary cell 1.
• the second threaded surface 26 of the membrane 20 is produced so as to have the same pitch as the other threaded surfaces 6,10,16,18 of the elementary cell 1, as well as of a diameter slightly greater than the diameter of the threaded surface
• the substrate 2 of the elementary cell 1 comprises a cylindrical boss 28 in which the nut 4 is partially made, this boss 28 protruding outside a main body 30 of this substrate 2. It should be noted that cylindrical bump
• the screw head 24 comprises an annular groove 34, at a lower surface intended to be pressed against the cylindrical boss 28 of the substrate 2.
• an annular groove 36 is located at an upper surface of the cylindrical boss 28, and disposed substantially opposite the annular groove 34 provided on the screw 12, when the latter is assembled on the substrate 2 of the elementary cell 1.
• O-ring seals 38, 40 are respectively intended to take place inside the annular grooves 34 and 36 and to come into contact with the annular portion 23 of the ion exchange membrane 20, so as to seal the elementary cell 1. It should be noted that this sealing is carried out in view of May maintain one or more reagents associated with each of the two electrodes 8 and 14, respectively in the substrate 2 and in the screw 12.
• the screw 12 is provided at its head 24 with a preferentially threaded end piece 42 capable of cooperating with injection means (not shown) of one or more reagents intended to supply the second electrode 14.
• the end piece 42 has internally a cylindrical orifice 44 of axis identical to the axis of the screw 12, this orifice 44 extending substantially all along the screw 12.
• the or the reagents used are then able to borrow this orifice 44 in the form of a longitudinal channel, and to diffuse in the direction of the first electrode 8 by circulating inside the screw 12 produced in a porous material.
• the helical contact zone between the threaded surface 18 of the second electrode 14 and the first threaded surface 22 of the membrane 20 then constitutes the exchange surface on which a first electrochemical reaction can take place.
• the substrate 2 has at its lower surface a tip 46 preferably taking the form of a threaded bore, capable of cooperating with injection means.
• the end piece 46 is extended by a cylindrical orifice 48 with an axis identical to the axis of the screw 12 and the nut 4 of the cell elementary 1.
• the orifice 48 opens into a space 50 partially delimited by the threaded surface 10 of the first electrode 8.
• the space 50 corresponds to a lower part of a hollowed out area defined by the nut 4 and / or the threaded surface 10 of the first electrode 8, this lower part being unoccupied by the screw 12 when it is assembled on the substrate 2.
• the space 50 into which the cylindrical orifice 48 opens also delimited by the ion exchange membrane 20, the latter having in fact a substantially flat portion 52 in the form of a disc extending perpendicular to the axis of the screw 12, and forming a cap at the level of the threaded end of this screw 12. Consequently, the threaded part of the screw 12 and the second electrode 14 are entirely confined in the ion-exchange membrane 20, so that the reagents injected into the screw 12 cannot come into contact with the reagents injected into the substrate 2.
• each reagent present in the space 50 is capable of infiltrating into interstices 51 of the existing helical connection between the first electrode 8 deposited on the nut 4, and the ion exchange membrane 20.
• a conventional helical connection like that provided between the elements mentioned above is such that there are contact zones between the elements, as well as zones in which the two elements are located at a distance from each other. In the latter zones communicating with each other and also called interstices of the helical connection, the fluid or liquid reagents can circulate freely in order to be distributed throughout the connection homogeneously.
• the interstices 51 allow the reagents to circulate homogeneously on the first electrode 8, while the contact zones between surface 10 and surface 26 have the function of serving as an exchange surface on which is capable of producing a second electrochemical reaction.
• the reagent (s) would be injected into one or more orifices of any shape provided in the substrate 2, the latter then being made of a porous material capable of allowing the diffusion of the reagents to the first electrode 8.
• the invention relates to a method for producing an elementary cell 1 for a fuel cell, such as that which has just been described.
• the ion exchange membrane 20 is first preformed, in particular using the screw 12.
• the membrane 20 can have first and second threaded surfaces 22 and 26, at a pitch identical to that of the threaded surface 16 of the screw 12.
• the second electrode 14 is deposited in the form of a coating on the threaded surface 16 of the screw 12, the deposit s 'effecting according to conventional deposition techniques such as the CVD method (from the English “Chemical Vapor Deposition”), or from the PVD method (from the English “Physical Vapor Deposition”).
• the coating obtained following the previous step is then machined so that the second electrode 14 is provided with the threaded surface 18, intended to receive the first threaded surface 22 of the ion exchange membrane 20.
• the substrate 2 comprises a nut 4 on which a coating is deposited in order to produce the first electrode 8, still using the conventional deposition techniques mentioned above.
• the coating obtained is then tapped so that the first electrode 8 has the threaded surface 10, intended to receive the second threaded surface 26 of the ion exchange membrane 20.
• the second electrode 14 is assembled by screwing the ion exchange membrane 20 onto the threaded surface 18 of the second electrode 14. Note that as the membrane 20 is preformed to the diameter of the screw 12 and not to the diameter of the threaded surface 18 of the second electrode 14 which is greater than it, the membrane 20 completely follows the threaded surface 18 of this second electrode. Consequently, there are no gaps between the threaded surface 18 of the second electrode 14 and the first threaded surface 22 of the ion exchange membrane 20.
• FIG. 3 there is partially shown a fuel cell 100 according to a preferred embodiment of the invention, the cell 100 comprising a plurality of elementary cells 1, such as that which has just been described.
• the substrate 2 is common to all the elementary cells 1, and the nuts 4 carrying the screws 12 are arranged in a matrix fashion on this substrate 2.
• the substrate 2 is then designed to supply each of the first electrodes 8 coating the nuts 4.
• the electrodes 8 and 14 (not shown in FIG. 3) of the cells 1 are electrically connected together, so that the power delivered by the battery 100 corresponds to the sum of the powers generated by each elementary cell 1 constituting the stack 100.
• the overall exchange surface of the battery 100 corresponding to the sum of the exchange surfaces of each of the elementary cells 1, is greatly increased compared to that obtained in fuel cells of the prior art.
• the matrix arrangement of the elementary cells 1 makes it possible to carry out maintenance operations without dismantling the entire stack, insofar as each of the elements 1 is accessible individually.
• the matrix arrangement facilitates the implantation of reserve elements, the latter being able to simply replace elements becoming defective and capable of being short-circuited.
• various modifications can be made by those skilled in the art to the elementary cell 1, to the fuel cell 100 and to the method of manufacturing the elementary cell 1 which have just been described, only by way of non-illustrative examples. limiting.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Fuel Cell (AREA)
• Inert Electrodes (AREA)

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• 2002
  • 2002-05-27 FR FR0206422A patent/FR2840109B1/fr not_active Expired - Fee Related
• 2003
  • 2003-05-23 JP JP2004508439A patent/JP4503432B2/ja not_active Expired - Fee Related
  • 2003-05-23 EP EP03755195A patent/EP1522112A2/fr not_active Withdrawn
  • 2003-05-23 WO PCT/FR2003/001569 patent/WO2003100896A2/fr active Application Filing
  • 2003-05-23 US US10/484,041 patent/US7445863B2/en not_active Expired - Fee Related
  • 2003-05-23 CN CNB038011557A patent/CN100539281C/zh not_active Expired - Fee Related

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