Multilayer device, method for preparing same and uses thereof in fuel cells

Abstract

The present invention relates to a multilayer device, the method for preparing same and the uses thereof, in particular in fuel cells.

Description

MULTILAYER DEVICE, PREPARATION METHOD THEREOF AND USES THEREOF IN FUEL CELLS

[0001] The present invention relates to a multilayer device, its preparation method and its uses, in particular in fuel cells.

[0002] Among electrochemical reactors, fuel cells are undergoing significant development. Fuel cells are being considered, in particular, as a source of energy for motor vehicles that will be produced on a large scale in the future or as auxiliary energy sources in aeronautics.

[0003] A fuel cell is an electrochemical device that converts chemical energy directly into electrical energy. It consists of a series stack of several cells.

[0004] Among the known types of fuel cells, we can notably cite the proton exchange membrane fuel cell, called PEMFC (for "Proton Exchange Membrane Fuel Cell), operating at low temperature. Such fuel cells have particularly interesting compactness properties. Each cell comprises an electrolytic membrane allowing only the passage of protons and not the passage of electrons. The membrane comprises an anode on a first face and a cathode on a second face to form a membrane / electrode assembly called AME.

[0005] At the anode, hydrogen fuel is oxidized to produce protons that pass through the membrane. The membrane thus forms an ionic conductor. The electrons produced by this reaction migrate to a flow plate and then pass through an electrical circuit external to the cell to form an electric current. At the cathode, oxygen is reduced and reacts with the protons to form water.

[0006] The fuel cell may comprise several so-called bipolar plates, typically made of metal, stacked on top of each other. The membrane is arranged between two bipolar plates. The bipolar plates may comprise flow channels and orifices to continuously guide the reactants and products to / from the membrane. The bipolar plates continuously supply the reactive zone of the electrodes with reactants, as they are consumed. The bipolar plates also comprise flow channels to guide coolant removing the heat produced. The reaction products and non-reactive species are evacuated by entrainment by the flow to the outlet of the flow channel networks. The flow channels of the different flows are separated by the bipolar plates in particular.

[0007] The bipolar plates are also electrically conductive to collect the electrons generated at the anode and carry the current thus collected.

[0008] The bipolar plates also have a function of watertight separator between the fluid circuits, in particular between the anode circuit (hydrogen) and the cathode circuit (air), and the cooling.

[0009] The bipolar plates also have a mechanical function of transmitting the stack clamping forces, necessary for the quality of the electrical contact, the holding of the cell and the distribution of combustible and oxidizing gases.

[0010] A seal between the components constituting the stack and towards the outside of the stack is also ensured, during the stacking phase of the stack, by adding an elastomer type seal between the different interfaces of the components constituting the stack.

[0011] After metal, work has focused on the preparation of composite bipolar plates. These have the following advantages: Lightness: Composite bipolar plates are generally lighter than their metal counterparts, which can reduce the overall weight of the fuel cell. This can be an advantage in mobile applications or where weight reduction is essential; Corrosion resistance: Composite plates are generally more resistant to corrosion than metal plates. Fuel cells operate with aggressive chemical reactions, and corrosion resistance is essential to extend the life of the cell; Mechanical strength: Composites can be reinforced to improve their mechanical strength, which can make them more durable in demanding environments.

[0012] However, composite bipolar plates have a relatively high permeation rate for low thickness (less than 250µm).

[0013] One objective of the invention is thus to provide devices making it possible to limit the diffusion of gases, in particular hydrogen.

[0014] Another objective of the invention is to provide devices making it possible to limit the disadvantages linked to the diffusion of gases, in particular hydrogen, while allowing a good compromise between the electrical, mechanical, mass transport / permeation and size / volume properties.

[0015] Thus, the invention relates to a multilayer device comprising at least one layer of composite material A consisting of or comprising a carbon veil and a resin, as well as at least one layer of material B consisting of or comprising a metal and / or dense carbon.

[0016] By “at least one layer of composite material A” and “at least one layer of composite material B” is meant in particular that these layers are in contact with each other.

[0017] The term “carbon veil” means in particular a layer comprising or consisting of woven or non-woven carbon fibers, preferably non-woven. These fibers have in particular a diameter of 5µm to 10µm, and / or a length of less than 1mm, preferably of 50 to 500µm.

[0018] Said carbon veil is generally a layer of carbon fibers oriented in a particular direction or at random, for example entangled, and in particular linked by friction, cohesion, and / or adhesion.

[0019] According to a particular embodiment, the resin is a thermoplastic or thermosetting polymer.

[0020] According to a particular embodiment, the resin is an amorphous or semi-crystalline polymer.

[0021] According to a more particular embodiment, the resin is chosen from the group of polymers comprising fluorinated ethylene-propylene (FEP), polyetheretherketone (PEEK), polyetherimide (PEI), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyvinyl fluoride (PVF), and mixtures thereof.

[0022] According to an even more particular embodiment, the resin is chosen from polyetheretherketones, polyetherimides, and their mixtures.

[0023] According to another more particular embodiment, the resin is chosen from phenolic resins.

[0024] According to another more particular embodiment, the resin is polymerized.

[0025] According to a particular embodiment, the resin is present in the at least one layer of composite material A at a level of 50 to 75% by volume relative to the total volume of the at least one layer of composite material A.

[0026] According to a particular embodiment, the metal is chosen from Al, Cu, stainless steel and their alloys.

[0027] According to a particular embodiment, the at least one layer of material B is in the form of a metal film coated on one of its carbon faces, in particular a copper film coated on one of its carbon faces.

[0028] According to a particular embodiment, the at least one layer of material B is in the form of a metal film coated on its two faces with carbon, in particular a copper film coated on its two faces with carbon.

[0029] According to a particular embodiment, the at least one layer of material B is in the form of a layer of dense carbon, for example chosen from carbon black and carbon nanotubes.

[0030] According to a particular embodiment, the at least one layer of material B is in the form of an expanded graphite film.

[0031] According to a particular embodiment, the at least one layer of material B is in the form of a layer of carbon powder.

[0032] According to a particular embodiment, the at least one layer of material B is in the form of a layer comprising carbon powder and the resin as defined previously.

[0033] According to a particular embodiment, the thickness of the at least one layer A is less than 200 µm, in particular from 10 to 150 µm, in particular from 10 to 50 or 100 µm.

[0034] According to a particular embodiment, the thickness of the at least one layer B is from 10 to 50 µm, in particular from 10 to 20 µm, in particular from 10 to 15 µm.

[0035] According to a particular embodiment, the thickness of the device according to the invention is from 20 µm to 250 µm, in particular from 100 to 210 µm.

[0036] According to a particular embodiment, the device according to the invention has an electrical resistance of less than 5 or 13 mΩ.cm².

[0037] According to a particular embodiment, the layers of the device as defined above are cohesive with each other. In this case, said layers are thus cohesive with the layers with which they are in contact.

[0038] According to a particular embodiment, the invention relates to a device as defined previously, comprising or consisting of, in this order: A layer of material A; A layer of material B; A layer of material A.

[0039] According to a particular embodiment, the material B is made of or comprises a metal.

[0040] According to a particular embodiment, the invention relates to a device as defined previously, comprising or consisting of: A layer of material A; A layer of material B.

[0041] According to a particular embodiment, material B is made of or comprises dense carbon.

[0042] When the device is a bipolar plate and / or is used within a fuel cell, the layer of material B may be present on the anode or cathode side, in particular on the anode side.

[0043] According to a particular embodiment, the invention relates to a device as defined previously, comprising or consisting of, in this order: A layer (i) of material B; A layer (ii) of material A; A layer (iii) of material B.

[0044] According to a particular embodiment, the material B of layers (i) and / or (iii) is made of or comprises dense carbon.

[0045] According to a particular embodiment, the invention relates to a device as defined above, comprising or consisting of, in this order: A layer (i) of material B; A layer (ii) of material A; A layer (iii) of material B; A layer (iv) of material A; A layer (v) of material B.

[0046] According to a particular embodiment, the material B of the layer (iii) is made of or comprises dense carbon.

[0047] According to a particular embodiment, the material B of layers (i) and / or (v) is made of or comprises dense carbon.

[0048] According to a particular embodiment, the invention relates to a device as defined previously, comprising or consisting of at least one layer A, and at least two layers B, the layers B being of different nature.

[0049] According to a particular embodiment, the device as defined previously is a bipolar plate, in particular a bipolar fuel cell plate, more particularly a proton exchange membrane fuel cell.

[0050] According to another aspect, the present invention also relates to the use of a device as defined above for preparing a bipolar plate.

[0051] According to another aspect, the present invention also relates to a method for preparing a device as defined above, comprising a step (1) of compressing a superposition of at least one layer B, and at least one layer A' and one layer A'', in contact with each other, the layer A' comprising or consisting of a carbon veil, the layer A'' comprising or consisting of a resin.

[0052] According to a particular embodiment, when the superposition comprises more than one layer A' and / or more than one layer A'', the layers A' and A'' are alternated, in contact with each other.

[0053] Such an embodiment is for example illustrated by the. In this, layers 1, 3 and 5 correspond to layers A', and layers 2 and 4 correspond to layers A'', as defined above. The layer obtained by step (1) of compression, for example by heating under pressure stress, here a layer of carbon fibers impregnated with resin, corresponds to layer A as defined above.

[0054] According to a more particular embodiment, the total number of layers A' and A'' alternating and in contact with each other is from 2 to 9, in particular from 3 to 7, in particular 5.

[0055] Without wishing to be limited to any theory, compression allows the impregnation, under pressure stress, of the A' layers by the A'' layers, to form the A layers as defined previously. The A' and A'' layers are thus precursors of the A layer.

[0056] According to a particular embodiment, the resin of the at least one layer A'' is a thermosetting polymer.

[0057] According to a particular embodiment, the compression of step (1) is carried out at a pressure of 8 to 30 MPa.

[0058] According to a particular embodiment, the compression of step (1) is carried out at a temperature of from 80 to 200°C, in particular from 200 to 400°C when the resin is for example a thermoplastic polymer, or from 80 to 200°C when the resin is for example a polymer or thermosetting material.

[0059] According to a particular embodiment, the compression of step (1) is carried out for a duration of 1 to 5 minutes.

[0060] The pressure, temperature and time values ​​mentioned above are given as examples and can be adapted by a person skilled in the art according to his general knowledge.

[0061] According to another aspect, the present invention also relates to a superposition of at least one layer B, and of at least one layer A' and one layer A'', in contact with each other, the layers A', A'' and B being as defined previously.

[0062] According to another aspect, the present invention also relates to the use of an overlay as defined above to prepare the device as defined above.

[0063] According to another aspect, the present invention also relates to the use of an overlay as defined above to prepare a bipolar plate.

[0064] According to another aspect, the present invention also relates to the use of a device as defined above or of a bipolar plate as defined above for the preparation of a fuel cell, in particular a proton exchange membrane fuel cell. DEFINITIONS

[0065] As used herein, the value ranges of "xy" or "from x to y" or "between x and y" include the bounds x and y, the integers between these bounds, and all other real numbers between these bounds. For example, "1-5", or "from 1 to 5" or "between 1 and 5" designates the integers 1, 2, 3, 4 and 5, as well as all other real numbers between 1 and 5. Preferred embodiments include each individual integer in the value range, as well as any subcombination of these integers and any set of real numbers between these integers. For example, preferred values ​​for "1-5" might include the integers 1, 2, 3, 4, 5, 1-2, 1-3, 1-4, 1-5, 2-3, 2-4, 2-5, etc.

[0066] As used herein, the term "about" refers to a range of values ​​within ± 10% of a specific value. For example, the term "about 20" includes values ​​of 20 ± 10%, or values ​​from 18 to 22. FIGURES

[0067] The invention relates to a method for preparing a device according to the invention, comprising a step (1) of compressing a superposition of at least one layer B, and at least one layer A' and one layer A'', in contact with each other, the layer A' comprising or consisting of a carbon veil, the layer A'' comprising or consisting of a resin.

[0068] Illustrates an experimental device for measuring gas tightness as described in Example 1.

[0069] Presents the gas permeation measurements (He) carried out under the conditions of example 1 on a control and the devices of example 2. EXAMPLES

[0070] Example 1: Witness outside the invention and flux measurement at He

[0071] A polymer membrane, Nafion® XL, was taken as a reference, constituting the membrane electrode assembly (MEA) and allowing, among other things, to separate and make sufficiently gas-tight the anodic and cathodic compartments of a PEMFC. The permeation test will be considered conclusive if the value achieved is similar to, or even lower than, that of this control polymer membrane.

[0072] For this reference outside the invention as for the devices of the invention exemplified below, the gas tightness was evaluated by measuring the He flow (permeation test).

[0073] The developed system uses helium, with its small molecular radius, to determine the gas tightness of the samples studied. A sample holder allows, upstream, to supply helium gas up to pressures of 3 bars and downstream, a leak detector allows to measure a minimum helium flow of 5.10-12 mbar.l / s or 5.10-12 Ncm3 / s. Knowing the diameter or the passage section of the gas in the sample (estimated at 40mm for a sample of diameter 63mm), its thickness and the upstream gas pressure, we can therefore indicate a leak flow rate in Ncm3.cm.cm-2.s-1.Pa-1. The sample holder can be installed in an oven to simulate the operating temperature of a battery.

[0074] Example 2: Preparation of devices according to the invention

[0075] The following devices were considered:

[0076] - H14-Vulcan / FEP100 / Vulcan-H14 for H14 carbon veil (Freudenberg) -Vulcan carbon powder / fluorinated ethylene-propylene 100 / Vulcan carbon powder- H14 carbon veil (Freudenberg);

[0077] - H14 / FEP50 / Cu / FEP50 / H14 for carbon veil H14 (Freudenberg) / fluorinated ethylene-propylene 50 / Copper / fluorinated ethylene-propylene 50 / carbon veil H14 (Freudenberg);

[0078] - C3 / FEP25 / H14 / FEP25 / C3 for expanded graphite C3 / fluorinated ethylene-propylene 25 / carbon veil H14 (Freudenberg) / fluorinated ethylene-propylene 25 / expanded graphite C3;

[0079] - C3 / PEN25 / H14 / PEN25 / C3 for expanded graphite C3 / polyethylene naphthalate 25 / carbon veil H14 (Freudenberg) / polyethylene naphthalate 25 / expanded graphite C3;

[0080] and prepared as follows:

[0081] -sampling of 50mm diameter disc of materials by punching;

[0082] -stacking in the desired order of these different materials.

[0083] A device outside the invention was also considered as a control, as mentioned in Example 1 (Nafion Gore B0046).

[0084] These devices have a total thickness of 100 to 210 µm.

[0085] They were obtained, in the example and results below, from thermoplastic, by impregnation at a temperature of 330°C to 450°C under a stress of between 8 and 22MPa depending on the polymers used.

[0086] Their gas tightness was tested according to the protocol of example 1, and is presented in.

[0087] The device examples are given with a thermoplastic resin, and it should be noted that the same will be true with a thermosetting resin.

[0088] This figure shows that the devices according to the invention have a helium permeation rate (the trend will be identical with the passage of hydrogen) of the same order of magnitude, or even lower than that of the reference outside the invention, while presenting a better compromise between the electrical, mechanical, mass transport / permeation and size / volume properties, than this reference.

[0089] It should be noted that the copper layer can be replaced by a copper layer coated on both sides with carbon, in particular an ARMOR copper layer (EN'safe 123), a dense carbon layer, or by an expanded graphite film, in particular of the Sinon Sigraflex (SGL) or Permafoil (ToyoTanso) type.

Claims

Multi-layer device comprising at least one layer of composite material A consisting of or comprising a carbon veil and a resin, and at least one layer of material B consisting of or comprising a metal and / or dense carbon. A multilayer device according to claim 1, wherein:the resin is a thermoplastic or thermosetting polymer, said resin being in particular chosen from the group of polymers comprising fluorinated ethylene-propylene (FEP), polyetheretherketone (PEEK), polyetherimide (PEI), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyvinyl fluoride (PVF), and mixtures thereof, and / orthe resin is present in the at least one layer of composite material A at a level of 50 to 75% by volume relative to the total volume of the at least one layer of composite material A. Multilayer device according to any one of the preceding claims, in which:the metal is chosen from Al, Cu, stainless steel and their alloys, orthe at least one layer of material B is in the form of a metal film coated on one of its faces with carbon, orthe at least one layer of material B is in the form of a metal film coated on both of its faces with carbon, orthe at least one layer of material B is in the form of a dense carbon layer, orthe at least one layer of material B is in the form of an expanded graphite film, orthe at least one layer of material B is in the form of a carbon powder layer, orthe at least one layer of material B is in the form of a layer comprising carbon powder and a resin identical to that defined in claim 1 with regard to the composite material A. Multilayer device according to any one of the preceding claims, wherein:the thickness of the at least one layer A is less than 200 µm, in particular from 10 to 150 µm, in particular from 10 to 50 or 100 µm,the thickness of the at least one layer B is from 10 to 50 µm, in particular from 10 to 20 µm, in particular from 10 to 15 µm, and / orits thickness is from 20 µm to 250 µm, in particular from 100 to 210 µm. A multilayer device according to any preceding claim, which has an electrical resistance of less than 5 or 13 mΩ.cm². Multilayer device according to any one of the preceding claims, which is a bipolar plate, in particular a bipolar plate of a fuel cell, more particularly of a proton exchange membrane fuel cell. Multilayer device according to any one of the preceding claims, comprising or consisting of at least one layer A, and at least two layers B, the layers B being of different nature. Method for preparing a device according to any one of claims 1 to 7, comprising a step (1) of compressing a superposition of at least one layer B, and at least one layer A' and one layer A'', in contact with each other, the layer A' comprising or consisting of a carbon veil, the layer A'' comprising or consisting of a resin, the layers A' and A'' being precursors of the layer A as defined in claim 1. Method according to claim 8, in which the compression of step (1) is carried out: at a pressure of 8 to 30 MPa, at a temperature of 80 to 200°C, in particular 200 to 400°C when the resin is for example a thermoplastic polymer, or 80 to 200°C when the resin is for example a polymer or thermosetting material, and / or for a period of 1 to 5 minutes. Superposition of at least one layer B, and at least one layer A' and one layer A'', in contact with each other, layers A' and A'' being precursors of layer A as defined in claim 1, and layer B being as defined in claim 1.

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