Method of disassembling a fuel cell

Abstract

Method for disassembling a fuel cell Method for disassembling a fuel cell comprising: a) providing a fuel cell comprising at least one stack comprising two membrane-electrode assemblies and a bipolar plate sandwiched between the membrane-electrode assemblies, each membrane-electrode assembly comprising an anode comprising an anodic gas diffusion layer and an anodic layer, a cathode comprising a cathodic gas diffusion layer and a cathodic layer, and a proton exchange membrane sandwiched between the anode and the cathode; b) introducing into the fuel cell a mixture comprising a disassembly fluid in the gaseous state capable of inducing a volume expansion of the membrane and a gas inert with respect to the anodic layer and the cathodic layer;and c) bringing the membrane-electrode assemblies into contact with the mixture, the absolute disassembly pressure of the mixture being strictly greater than 100 kPa. Figure for abstract: None;

Description

Title of the invention: Method for disassembling a fuel cell Technical field

[0001] The present invention relates to the field of recycling fuel cells and in particular end-of-life fuel cells in stacks. More specifically, it relates to a method for disassembling a proton exchange membrane fuel cell known by the acronym PEMFC ("Proton Exchange Membrane Fuel Cell"). It relates in particular to the disassembly of the membrane-electrode assemblies (known by the acronym "AME") of a PEMFC cell. Prior art

[0002] The operating principle of a PEMFC cell is based on the conversion of chemical energy into electrical energy by catalytic reaction of a fuel, generally hydrogen, and an oxidant, generally oxygen.

[0003] As illustrated in [Fig. 1] illustrating an example of a PEMFC cell, a PEMFC cell 100 generally comprises a stack of membrane-electrode assemblies 10. The membrane-electrode assemblies are separated from each other by bipolar plates 20. The bipolar plates 20 ensure the supply of oxidant to the cathode layer of a membrane-electrode assembly and the supply of fuel to the anodic layer of the contiguous membrane-electrode assembly. In addition, they electrically connect in series the adjacent membrane-electrode assemblies between which they are interposed. The cell 100 may further comprise terminal plates 28 sandwiching all of the membrane-electrode assemblies and bipolar plates and making it possible to press the bipolar plates 20 against the membrane-electrode assemblies 10 to ensure a good electrical connection and a good seal within the cell.Electrical power connectors may be present on the terminal plates.

[0004] As shown in [Fig.2] illustrating an example of a membrane-electrode assembly, a membrane-electrode assembly 10 comprises an anodic layer 35 and a cathodic layer 38, separated and carried by a solid electrolyte in the form of a proton exchange membrane 40 generally based on polymer. The anodic 35 and cathodic 38 layers each comprise a catalyst and are the location of the anodic and cathodic electrochemical reactions. The membrane-electrode assembly further comprises, on either side of the membrane, anodic 45 and cathodic 48 gas diffusion layers (GDL for “Gas Diffusion Layer” in English), arranged respectively on the side of the anodic 35 and cathodic 48 layers. of the cathode layer 38 relative to the membrane. The anodic 45 and cathodic 48 gas diffusion layers collect the electric current and allow the supply of reactive gas, and the elimination of water and heat produced within the membrane-electrode assembly. The membrane-electrode assembly may further comprise a reinforcement and / or a seal 30 in order to ensure the sealing of the AME to the fuel and the oxidant.

[0005] Several types of AME are known.

[0006] The membrane-electrode assembly may be of the “CCM” type, an acronym for “Catalyst Coated Membrane”. A CCM type MEA is obtained by depositing the anodic and cathodic layers on either side of the proton exchange membrane, the gas diffusion layers then being arranged on the anodic and cathodic layers. Hot pressing of the MEA may be implemented to ensure efficient assembly between the diffusion layers and the CCM.

[0007] Another known membrane-electrode assembly is of the “CCB” type, an acronym for “Catalyst Coated Backing”. A CCB type MEA is obtained by depositing an anodic layer or a cathodic layer on the gas diffusion layers. This assembly is called a “GDE”, an acronym for “Gas Diffusion Electrode”. An anodic GDE and a cathodic GDE are then applied on either side of the proton exchange membrane. Hot pressing of the MEA can be implemented to ensure an efficient assembly between the GDEs and the membrane.

[0008] In order to reduce the environmental impact and the cost of raw materials for the manufacture of fuel cells, the recycling of their materials and in particular of MEAs is generally sought. To this end, it has been proposed to disassemble the MEAs in order to recover and separate their different elements.

[0009] US 5,718,984 A describes for example the recovery of an electrolytic membrane with methanol and hydrogen peroxide which are toxic and / or not environmentally friendly. Methanol cannot be reused due to a dissolution reaction. It is also known that hydrogen peroxide causes degradation of electrolytic membranes.

[0010] US 8,124,261 B2 describes a method for recycling the elements of a membrane-electrode assembly of a PEMFC stack. The method comprises a first step of shredding the AME, which makes the steps of separating the elements of the AME and their subsequent reuse complex.

[0011] Carmo et al., International Journal of Hydrogen Energy 44, 3450-3455 (2019) describes a process for recycling catalyst-coated membranes (CCMs) used for water electrolysis. However, such a process is unsuitable for the case of an AME implemented in a fuel cell.

[0012] Other methods for recycling and / or disassembling AME are also described in DE 10 2012 109 063 Al, WO 2015 / 010793 A2, CN 106 898 790 A and CN 112 421 067 B. It is also possible to cite US 2018 / 108932 Al, KR 102 133 140 Bl, US 2021 / 296658 Al, US 2006 / 237034 Al, US 2010 / 200161 Al, US 2014 / 004448 Al, US 2007 / 134536 Al and US 8 535 841 Bl.

[0013] However, the methods known to date generally require first disassembling the fuel cell and / or using a significant quantity of solvent, and / or implementing complex separation steps.

[0014] Thus, there is a need for a method which is simple, rapid and inexpensive to implement and has a low environmental impact, in order to recover different constituent elements of a PEMFC cell and in particular different constituent elements of the AMEs of a fuel cell, with a view to recycling them and / or reusing them for the manufacture of a new PEMFC cell. Statement of the invention

[0015] The invention aims to at least partially satisfy these needs.

[0016] It relates to a method of disassembling a fuel cell comprising: (a) providing a fuel cell comprising at least one stack comprising two membrane-electrode assemblies and a bipolar plate sandwiched between the membrane-electrode assemblies, each membrane-electrode assembly comprising an anode comprising an anodic gas diffusion layer and an anodic layer, a cathode comprising a cathodic gas diffusion layer and a cathodic layer, and a proton exchange membrane sandwiched between the anode and the cathode; b) introducing into the fuel cell a mixture comprising a disassembly fluid in the gaseous state capable of inducing a volume expansion of the membrane and a gas inert with respect to the anodic layer and the cathodic layer; and c) bringing the membrane-electrode assemblies into contact with the mixture, the absolute disassembly pressure of the mixture being strictly greater than 100 kPa (1 bara) and preferably strictly less than 500 kPa (5 bara).

[0017] Within each of the assemblies, by layers, unless otherwise indicated, is meant at least any two layers from among the anodic layer, the cathodic layer and the anodic and cathodic gas diffusion layers.

[0018] Without being bound by any theory, the disassembly fluid, in particular under pressure, in step c) reaches the membrane through the gas diffusion layers and the cathode and anodic layers. The disassembly fluid then diffuses to the membrane, which generates a volume expansion of the membrane. The transfer of the fluid within the assembly induces a reduction in the cohesion force. between the layers and / or between the layers and the membrane and / or between one of the bipolar plates and the layers of the MEAs adjacent to said bipolar plate. It is then possible to separate the layers and / or the membrane and / or the bipolar plate from each other, in particular to separate the layers and / or the membrane from each other.

[0019] The method can allow the disassembly of the MEAs while maintaining the physical integrity of the MEA layers and membrane, in particular the gas diffusion layers and the membrane. It is therefore possible to avoid subsequent separation steps.

[0020] The method further makes it possible to disassemble a fuel cell, in particular the MEAs, directly by treating the fuel cell, without a prior step of dismantling the fuel cell. All the MEAs of a fuel cell can then be treated simultaneously, directly within the fuel cell, to reduce the cohesive force between the layers and / or between the layers and the membrane and / or between the bipolar plate and the layers of the MEAs adjacent to the bipolar plate. The method for disassembling the fuel cell thus makes it possible to quickly and efficiently disassemble several MEAs.

[0021] The method also makes it possible, by using the disassembly fluid in the gaseous state, in combination with an inert gas acting as a carrier gas, to significantly reduce the quantity of solvent used to separate the various constituent elements of a fuel cell, in particular the constituent elements of the MEAs. In addition, the disassembly fluid in the gaseous state makes it possible to limit the solubilization of the constituent elements of a fuel cell.

[0022] The method further allows the disassembly of most known MEAs. In particular, it is suitable for the disassembly of CCM type MEAs and CCB type MEAs.

[0023] The process is also environmentally friendly in that it generates little or no waste, and the disassembly fluid can be used in small quantities, or even recovered and recycled.

[0024] The ability of a fluid to induce volume expansion of the membrane can be evaluated by determining the volume of the membrane before and after contacting the membrane with the fluid.

[0025] In the remainder of the text, by "catalytic layers", unless otherwise indicated, is meant one and / or the other of the cathodic layer, also called cathodic catalytic layer, and anodic layer, also called anodic catalytic layer. Brief description of the drawings

[0026] [Fig. 1] schematically represents an example of a fuel cell in which an AME and a bipolar plate are separated from the rest of the stack for the sake of readability.

[0027] [Fig.2] schematically represents in an exploded view an example of assembly membrane electrodes in which the different layers are separated from each other for readability.

[0028] [Fig.3] is a photograph showing a bipolar plate and an AME separated from the side of the cathode at the end of the process according to the invention, as described in example 1.

[0029] [Fig.4] is a photograph showing the manual separation of a layer of diffusion of gas and of the membrane of an AME on the cathode side at the end of the process according to the invention, as described in example 1. Detailed description

[0030] In step a), the stack may comprise only two membrane-electrode assemblies or more than two membrane-electrode assemblies, the consecutively adjacent MEAs all being separated by a bipolar plate. In particular, the stack may comprise more than 5 membrane-electrode assemblies, in particular more than 10 membrane-electrode assemblies, or even more than 200 membrane-electrode assemblies.

[0031] The bipolar plate(s) may comprise one or more fuel supply channels for supplying the membrane-electrode assemblies with fuel and one or more oxidant supply channels for supplying the membrane-electrode assemblies with oxidant.

[0032] They may further comprise one or more anode discharge channels and / or one or more cathode discharge channels for purging the fuel cell of the anode reaction products and the cathode reaction products respectively.

[0033] The bipolar plate(s) may be made of graphite, metal, metal alloy, or an organic composite comprising conductive fillers such as carbon black, carbon fibers, or graphite.

[0034] The bipolar plates may be identical or different, in particular identical.

[0035] The stack may be gas-tight except for the fuel supply channels, the oxidant supply channels, the anode exhaust channels and the cathode exhaust channels.

[0036] The fuel cell may comprise end plates sandwiching the stack. The end plates may comprise fuel or oxidant supply channels for supplying the membrane-electrode assemblies located at the ends of the stack.

[0037] The membrane-electrode assemblies of the fuel cell may be identical or different, in particular identical.

[0038] The membrane-electrode assemblies may be of the CCM type or of the CCB type. In particular, the membrane-electrode assemblies may be obtained by a process comprising a hot pressing step.

[0039] The proton exchange membrane can be chosen from the examples of membrane described in S. Lyonnard (Membranes for fuel cells: structure and transport. Contribution of neutron diffusion. Collection SFN 11 177-197, 2010, DOI: 10.1051 / sfn / 201011011).

[0040] The proton exchange membrane may comprise, or even consist of, a perfluorinated polymer, preferably a sulfonated perfluorinated polymer, in particular comprising a fluorocarbon main chain, in particular perfluorinated, for example of the polytetrafluoroethylene (PTFE) type such as Teflon® type chains, onto which are grafted pendant chains, in particular perfluorinated, for example of the perfluorovinylether type, terminated by a sulfonate ionic group. Examples of proton exchange membranes based on perfluorinated polymer are membranes of the Nafion®, Flemion™ (Asahi Glass), Aciplex-S™ (Asahi Chemical), Dow™ (Dow Chemical), Hyflon™ (Solvay-Solexis) and Aquivion™ (Solvay) type. An example of a proton exchange membrane based on sulfonated perfluorinated polymer is the Nafion® type membrane. Alternatively, the proton exchange membrane may be a membrane comprising, or even consisting of, a non-fluorinated polymer with an aromatic skeleton, in particular chosen from polymers comprising sulfonic acid functions, for example polystyrene-divinylbenzene sulfonic acid, aromatic ether polymers, for example poly(arylene ether sulfone), polyether ether ketone (PEEK), sulfonated polyimides (Pis).

[0041] In particular, the proton exchange membrane is a composite membrane comprising a polymer as described above, preferably comprising a sulfonated perfluorinated polymer such as Nafion®, in which polytetrafluoroethylene is incorporated, for example a Gore-Select® membrane.

[0042] Preferably, the proton exchange membrane may comprise, or even consist of, a sulfonated perfluorinated polymer, in particular may be a composite or non-composite membrane, the sulfonated perfluorinated polymer more preferably comprising a main fluorocarbon chain of polytetrafluoroethylene (PTFE) type onto which are grafted pendant chains of perfluorovinylether type terminated by a sulfonate ionic group. Preferably, the proton exchange membrane based on sulfonated perfluorinated polymer is a membrane of Nafion® type or of Gore-Select® type, in particular of Nafion® type.

[0043] The proton exchange membrane may have a thickness of between 8 pm and 175 pm, in particular between 10 pm and 175 pm.

[0044] The anodic and cathodic layers respectively comprise a catalyst for the anodic and cathodic reactions.

[0045] The anodic layer may comprise a catalyst chosen from platinum and bimetallics such as PtRu and PtSn, preferably platinum. Preferably, the anodic layer further comprises an ionomer, useful for proton conduction. It may have a thickness of at least 2 μm, in particular between 2 and 10 μm.

[0046] The cathode layer may comprise a catalyst chosen from platinum and bimetals such as PtCo and PtNi, preferably platinum. Preferably, the cathode layer further comprises an ionomer, useful for proton conduction. It may have a thickness of at least 5 μm, in particular between 5 and 20 μm.

[0047] The anodic and cathodic gas diffusion layers are respectively in contact with the anodic layer and the cathodic layer. They may be identical or different. They may comprise a substrate, in particular porous, more particularly carbon-based, in particular carbon paper or carbon fibers, woven or preferably non-woven, for example with a diameter of between 7 and 10 μm, and impregnated with a hydrophobic agent, in particular of the polytetrafluoroethylene (PTFE) type, at a content which may be between 5 and 30 wt% relative to the mass of the substrate. The substrate may be coated on one side with a microporous layer, called "MPL", an acronym for "Micro Porous Layer", which is hydrophobic electrically conductive.In particular, the hydrophobic electrically conductive MPL microporous layer may comprise a hydrophobic polymer binder, in particular at least polytetrafluoroethylene (PTFE), in which a carbon material, in particular at least carbon black and / or graphite, is dispersed. The gas diffusion layers may have a thickness of between 100 and 250 μm. The MPL microporous layers may have a thickness of between 20 and 50 μm.

[0048] The membrane-electrode assemblies may comprise a superposition of layers formed in succession by the anodic gas diffusion layer, the anodic layer, the membrane, the cathodic layer, and the cathodic gas diffusion layer. In particular, the layers and the membrane of the membrane-electrode assemblies have a surface area, in particular an active surface area, greater than 1 cm2, in particular greater than 1.8 cm2, in particular between 25 cm2 and 300 cm2, or even between 25 cm2 and 150 cm2. The active surface corresponds to the surface on which the electrochemical reaction takes place.

[0049] The fuel cell may be used. In particular, the fuel cell has been previously used as an electrochemical generator, in particular for several thousand hours. Preferably, the fuel cell provided in step a) has not undergone any disassembly and no modification of its structure. For example, a fuel cell, in particular used, may be directly provided in step a), in particular without a prior step.

[0050] The method may comprise, prior to step b), a step of purging the fuel cell by circulating a purge fluid in the fuel cell, in particular in the fuel supply channel(s) and / or in the oxidant supply channel(s). Preferably, the purging step is carried out by circulating a purge fluid in the fuel supply channel(s) and in the oxidant supply channel(s).

[0051] The purge fluid may be a dry or wet inert gas, i.e. respectively free of water vapor or loaded with water vapor. Preferably, the purge fluid is argon or nitrogen, in particular dry or wet, in particular nitrogen, in particular dry or wet. The fuel cell may be heated up to 90°C in order to facilitate the desorption of the residual gases.

[0052] The purging step may comprise contacting the membrane-electrode assemblies with the purging fluid.

[0053] The purging step aims to purge the fuel cell, in particular the membrane-electrode assemblies, of residual reactive gases, in particular hydrogen and oxygen, in particular air, for example present in the fuel or oxidant supply channel(s) or adsorbed on the layers of the MEA. This preliminary step makes it possible to reduce the risks of inflammation linked to contact between the catalyst(s) of the catalytic layers, called platinum, and the disassembly fluid, in particular ethanol.

[0054] The mixture can be introduced in step b) into the fuel cell via the bipolar plates.

[0055] Preferably, the mixture is introduced in step b) into the fuel cell through the fuel supply channel(s) and / or the oxidant supply channel(s). In this way, the mixture can flow to the anode and / or cathode respectively. The mixture can be introduced in step b) into the fuel cell, preferably simultaneously, through the fuel supply channel(s) and the oxidant supply channel(s), in order to reach the anode and the cathode, preferably simultaneously.

[0056] The mixture may be introduced in step b) at an absolute pressure of the mixture strictly greater than 100 kPa (1 bara), in particular greater than or equal to 150 kPa (1.5 bara), more particularly greater than or equal to 200 kPa (2 bara).

[0057] The mixture may be introduced in step b) at an absolute pressure of the mixture strictly less than 500 kPa (5 bara), in particular less than or equal to 350 kPa (3.5 bara), more particularly less than or equal to 300 kPa (3 bara).

[0058] The mixture may be introduced in step b) at an absolute pressure of the mixture of between 100 kPa (1 bara) and 500 kPa (5 bara), preferably between 150 kPa (1.5 bara) and 350 kPa (3.5 bara), more preferably between 200 kPa (2 bara) and 300 kPa (3 bara).

[0059] The mixture may be introduced in step b) at a temperature greater than or equal to the boiling point of the disassembly fluid and less than or equal to the temperature of the fuel cell to avoid unwanted condensation of the disassembly fluid in the fuel cell during its introduction. Preferably, the mixture may be introduced in step b) at a temperature between 78°C and 100°C, more preferably between 78°C and 95°C.

[0060] The disassembly fluid may be chosen from solvents and their mixtures, in particular from polar solvents and their mixtures, preferably from protic polar solvents and their mixtures, in particular from alcohols and their mixtures.

[0061] In particular, the disassembly fluid is chosen from dimethyl sulfoxide (DMSO), acetone, N,N-dimethylformamide (DMF), acetonitrile, ethyl acetate, methanol, ethanol, isopropanol, water, hexafluoroisopropanol, formic acid, acetic acid, ammonia and mixtures thereof. Preferably, the disassembly fluid is chosen from ethanol, isopropanol and mixtures thereof, more preferably is ethanol.

[0062] Advantageously, isopropanol and ethanol are environmentally friendly disassembly fluids.

[0063] The inert gas allows the disassembly fluid to be transported in the fuel cell to the membrane-electrode assemblies. The inert gas can also be called an inert carrier gas.

[0064] By gas “inert with respect to the anodic layer and the cathodic layer” is meant a gas which does not react with the catalyst(s) present in the anodic and cathodic layers, unlike dioxygen or dihydrogen.

[0065] The inert gas may be chosen from argon and nitrogen, preferably nitrogen.

[0066] The mixture may comprise from 63% to 97% by volume of the disassembly fluid and from 3% to 37% by volume of the inert gas.

[0067] Preferably, the mixture consists of at least 90% by volume, in particular at least 95% by volume, more particularly at least 99% by volume, or even at least 99.5% by volume of the disassembly fluid in the gaseous state and of the inert gas in step b). In particular, the mixture consists of the disassembly fluid and the inert gas.

[0068] When the mixture comprises compounds distinct from the disassembly fluid and the inert gas, these are preferably in the gaseous state in step b). Preferably, the mixture is in the gaseous state in step b).

[0069] Preferably, the mixture is free of compounds which can react with the cathode layer and / or the anodic layer, in particular with the catalyst(s) present in the anodic and cathodic layers. In particular, the mixture is free of dioxygen and dihydrogen, more particularly is free of dioxygen, dihydrogen and water. The mixture is advantageously inert with respect to the anodic layer and the cathodic layer.

[0070] The method may comprise a step b') prior to step b), in which the mixture is formed by evaporation of the disassembly fluid, in particular by heating to a temperature greater than or equal to the boiling point of the disassembly fluid, and contacting the disassembly fluid with the inert gas, the contacting being simultaneous with or subsequent to the evaporation. The inert gas may pass through the disassembly fluid heated to at least its boiling point so that the inert gas becomes charged with disassembly fluid vapor.

[0071] The evaporation of the disassembly fluid can be carried out directly in the system for generating humidification of the combustible or oxidizing gases intended to supply the fuel cell during its operation by first replacing the water contained in the generation system with the disassembly fluid. In particular, the evaporation of the disassembly fluid can be carried out in a bubbler.

[0072] The inert gas may be bubbled into the liquid disassembly fluid as it evaporates to obtain the mixture, which allows the inert gas to become charged with disassembly fluid vapor. Alternatively, the inert gas may be introduced into the gaseous disassembly fluid obtained by evaporation.

[0073] Evaporation of the disassembly fluid can also be carried out in an injector.

[0074] The introduction of the mixture into the fuel cell can allow the circulation of the mixture in the fuel cell to all the MEAs of the fuel cell. In particular, the circulation of the mixture can be carried out in a closed loop or an open loop, in particular in a closed loop, in particular by condensing the steam leaving the fuel cell in order to recover the solvent for reuse. When the circulation is carried out in an open loop, the mixture can be bubbled in water after its circulation in the fuel cell in order to dissolve the steam in a large volume of water and prevent its release into the atmosphere.

[0075] In particular, the mixture is circulated in the fuel cell, in particular in the fuel supply channel(s) and / or in the oxidant supply channel(s), at a flow rate of between 1 NL / h and 50 NL / h, in particular between 5 NL / h and 15 NL / h.

[0076] A normolitre NL of a gas is equal to the volume that said gas would occupy at a temperature of 0°C and under a pressure of 101,325 Pa.

[0077] The contacting in step c) can be carried out by circulating the mixture in the fuel cell up to the membrane-electrode assemblies, in particular up to the cathode or up to the anode of the membrane-electrode assemblies.

[0078] The mixture may be introduced in step b) into the fuel cell via the fuel supply channel(s) and / or via the oxidant supply channel(s), and the anode and / or the cathode are brought into contact in step c) with the mixture.

[0079] Preferably, the anode and the cathode are brought into contact in step c), preferably simultaneously, with the mixture at the absolute disassembly pressure.

[0080] When the mixture is brought into contact with the membrane-electrode assemblies, the mixture, in particular the disassembly fluid, can diffuse through the cathode and / or the anode, in particular through the anodic layer and the anodic gas diffusion layer and / or the cathodic layer and the cathodic gas diffusion layer, to the membrane. Preferably, the disassembly fluid diffuses into the membrane in step c), in particular so as to be absorbed by the membrane. In particular, the contact in step c) allows the disassembly fluid to induce a volume expansion of the membrane.

[0081] The absolute disassembly pressure of the mixture in step c) is strictly greater than 100 kPa (1 bara), in particular greater than or equal to 150 kPa (1.5 bara), more particularly greater than or equal to 200 kPa (2 bara).

[0082] It may be strictly less than 500 kPa (5 bara), in particular less than or equal to 350 kPa (3.5 bara), more particularly less than or equal to 300 kPa (3 bara). The pressure difference between the anode and cathode compartments is preferably less than or equal to 50 kPa (0.5 bara). The risk of damage to the membrane under pressure is thus reduced.

[0083] In particular, the absolute disassembly pressure of the mixture in step c) may be between 100 kPa (1 bara) and 500 kPa (5 bara), preferably between 150 kPa (1.5 bara) and 350 kPa (3.5 bara), more preferably between 200 kPa (2 bara) and 300 kPa (3 bara).

[0084] The temperature of the mixture in step c) may be between 15°C and 100°C, in particular between 78°C and 100°C, preferably between 78°C and 95°C.

[0085] The disassembly fluid in step c) may be in the liquid state or in the gaseous state.

[0086] Step c) may comprise bringing the membrane-electrode assemblies into contact with the disassembly fluid in the gaseous state, the mixture preferably being in step c) at an absolute pressure of between 100 kPa (1 bara) and 500 kPa (5 bara) and at a temperature of between 78°C and 100°C. The absolute difference between the pressure of the mixture in step b) and the pressure of the mixture in step c) may be less than or equal to 100 kPa (1 bara), in particular less than or equal to 80 kPa (0.8 bara), or even less than or equal to 50 kPa (0.5 bara). The use of the disassembly fluid in the gaseous state may advantageously make it possible to reduce the cohesive force between the catalytic layers and the gas diffusion layers.

[0087] Alternatively, step c) may comprise bringing the membrane-electrode assemblies into contact with the disassembly fluid at least partially in the liquid state, which makes it possible to facilitate the subsequent disassembly of an MEA. Preferably, the mixture is in step c) at an absolute pressure of between 100 kPa (1 bara) and 500 kPa (5 bara) and at a temperature of between 15°C and 70°C. The fluid may undergo condensation in the fuel cell by modifying the temperature and / or the pressure of the mixture after its introduction into the fuel cell. In particular, the temperature of the mixture is reduced after its introduction into the fuel cell. The use of the disassembly fluid in the liquid state may advantageously make it possible to reduce the cohesive force between the catalytic layers and the membrane.

[0088] According to a particular embodiment, step c) may comprise bringing the membrane-electrode assemblies into contact with the disassembly fluid in the gaseous state and in the liquid state. In particular, step c) may comprise one or more steps c1) in which the membrane-electrode assemblies of the fuel cell are brought into contact with the disassembly fluid in the gaseous state, and one or more steps c2) in which the membrane-electrode assemblies of the fuel cell are brought into contact with the disassembly fluid at least partially in the liquid state, the absolute disassembly pressure of the mixture being strictly greater than 100 kPa (1 bara) in steps c1) and c2). In particular, step c) comprises at least two cycles comprising step c1) and step c2).

[0089] The duration of step c) may be adapted according to the composition of the mixture. Advantageously, step c) is carried out until the cohesive force is reduced between at least two of said layers of the MEAs, or even between all of said layers in contact, and / or at least between one of said layers of the MEAs and the membrane of the MEAs or even between the membrane and all of the layers in contact with the membrane, and / or between the bipolar plate(s) and at least one MEA in contact with the bipolar plate(s) or even between the bipolar plate(s) and all of the MEAs in contact with the bipolar plate(s).

[0090] The duration of step c) may be between 10 minutes and 10 hours, in particular between 30 minutes and 5 hours, more particularly between 30 minutes and 1 hour.

[0091] In particular, step c) can make it possible to reduce the cohesive force between the anodic and cathodic gas diffusion layers and respectively the anodic and cathodic catalytic layers of the MEAs of the fuel cell or between the membrane of the MEAs and each of the anodic and cathodic catalytic layers of the MEAs.

[0092] The layers and / or the membrane, in particular the layers and the membrane, obtained after step c) are self-supporting, that is to say they do not break under the effect of their own weight. In particular, less than 20% by mass, in particular less than 10% by mass, or even less than 5% by mass, or even less than 1% by mass of the layers and / or the membrane, in particular the layers and the membrane, are solubilized or dispersed in the mixture in step c). Preferably, at the end of step c), the layers and the membrane can be recovered from the fuel cell.

[0093] Preferably, the integrity of the layers and / or the membrane, in particular of the layers and the membrane, is preserved during step c), in particular during the process. For example, the length, width and thickness of said gas diffusion layers and of the membrane are substantially identical before and after step c), i.e. they have not varied by more than 5%, in particular by more than 1%, compared to the length, width and thickness measured in step a).

[0094] The method may comprise, at the end of step c) and preferably prior to dismantling the fuel cell, a step of inerting the fuel cell by circulating in the fuel cell, in particular in the fuel supply channel(s) and / or in the oxidant supply channel(s), an inerting fluid. In particular, the inerting step is carried out by circulating an inerting fluid in the fuel supply channel(s) and in the oxidant supply channel(s).

[0095] The inerting fluid may be a dry or wet inert gas, preferably wet. In particular, the purge fluid is nitrogen, in particular dry or wet, preferably wet.

[0096] The inerting step may comprise bringing the membrane-electrode assemblies into contact with the inerting fluid.

[0097] The inerting step aims to expel the vapor residues of the disassembly fluid, in particular ethanol, contained in the fuel cell in order to improve safety during the subsequent disassembly of the fuel cell, without risk of inhalation of solvent.

[0098] At the end of step c), if applicable at the end of the inerting step, the fuel cell can be dismantled.

[0099] At the end of step c), the bipolar plate and at least one membrane-electrode assembly in contact with the bipolar plate, in particular the two membrane-electrode assemblies in contact with the bipolar plate, can be separated from each other and / or at least two of said layers and / or the membrane and at least one of the layers in contact with the membrane can be separated from each other.

[0100] Alternatively, the method may further comprise a step d), subsequent to step c), where appropriate subsequent to the inerting step, during which the bipolar plate and at least one membrane-electrode assembly in contact with the bipolar plate, in particular the two membrane-electrode assemblies in contact with the bipolar plate, are separated from each other and / or at least two of said layers and / or the membrane and at least one of the layers in contact with the membrane are separated from each other, preferably at least two of said layers and / or the membrane and at least one of the layers in contact with the membrane are separated from each other. The separation of the layers and / or the membrane may be carried out mechanically, in particular manually, for example by peeling the layers off from each other, for example by stretching, winding or twisting a layer.Since the cohesive force between the different layers and / or between the layers and the membrane is reduced, it is easy to separate them without physically altering them.

[0101] Step d) may comprise separating the bipolar plate(s) from the anodic and cathodic gas diffusion layers of adjacent MEAs.

[0102] Preferably, step d) comprises separating the anodic and cathodic catalytic layers and the anodic and cathodic gas diffusion layers respectively, and / or separating the catalytic layers and the proton exchange membrane.

[0103] In particular, step d) may comprise the separation of the anodic gas diffusion layer, the cathodic gas diffusion layer and the assembly formed by the cathodic, anodic layers and the membrane, the cathodic and anodic layers remaining integral with the proton exchange membrane. Alternatively, step d) may comprise the separation of the membrane, the assembly formed by the cathodic layer and the cathodic gas diffusion layer, and the assembly formed by the anodic layer and the anodic gas diffusion layer, the cathodic and anodic layers remaining respectively integral with the cathodic and anodic gas diffusion layers.

[0104] Preferably, step d) comprises: - the separation of the bipolar plate(s) from the anodic and cathodic gas diffusion layers of the adjacent MEAs, and - the separation of the anodic gas diffusion layer, the cathodic gas diffusion layer and the assembly formed by the cathodic, anodic and the membrane or the separation of the membrane, of the assembly formed by the cathode layer and the cathode gas diffusion layer, and of the assembly formed by the anodic layer and the anodic gas diffusion layer.

[0105] The method may further comprise a step e) following step c), the inerting step or step d) comprising the recovery of the bipolar plate(s), the anodic and cathodic gas diffusion layers and the membranes separated from each other. In particular, step e) is carried out following step d).

[0106] The method may further comprise a step f), in particular following step d) and / or step e), of washing the membranes, and / or the anodic and cathodic gas diffusion layers, in particular by contacting with a washing liquid or by immersion in an ultrasonic bath, preferably by immersion in an ultrasonic bath. The ultrasonic bath may contain ethanol, isopropanol, water or mixtures thereof, in particular ethanol. The immersion of the membranes, and / or the anodic and cathodic gas diffusion layers in an ultrasonic bath may be carried out for a duration of less than 5 min, in particular between 1 min and 2 min.

[0107] This step makes it possible to eliminate the residues present on the surface of the recovered layers and / or membranes, these residues being in particular derived from the layers of the AME separated from said recovered layer or membrane.

[0108] The recovered layers, membranes and bipolar plates can be recycled independently of each other.

[0109] Alternatively, the recovered layers and / or membranes may be reused, following step d) or, preferably, step e) to manufacture one or more new AMEs. Preferably, the recovered layers and / or membranes may undergo at least one treatment before their reuse.

[0110] The method may further comprise recovering the mixture, in particular the disassembly fluid. The recovered disassembly fluid may in particular be used in a method according to the invention. When the mixture is recovered in the gaseous state, the disassembly fluid may be recovered by condensation. Examples Example 1

[0111] The example below illustrates a method according to the invention, which was carried out on a fuel cell comprising a stack of two CCM type MEAs separated by a bipolar plate comprising fuel and oxidant supply channels. The stack is placed between two end plates. The MEAs comprise:

[0112] - two gas diffusion layers, anodic and cathodic, marketed under the denomination H23C7 by the Freudenberg company;

[0113] - a cathodic layer based on a Pt / C type catalyst loaded with 47% Pt (Tanaka) and an anodic layer based on Pt / C type catalyst loaded with 30% Pt (Tanaka); and

[0114] - a long-chain PFSA-based proton exchange membrane from the company Gore.

[0115] The active surface area of ​​the AMEs is 220 cm2.

[0116] The fuel cell is placed on a test bench. The following steps are implemented.

[0117] - Step 1: The fuel cell is first purged for one hour with dry nitrogen introduced into the fuel cell through the oxidant and fuel supply channels using a bubbler.

[0118] - Step 2: Ethanol vapors are generated by heating 600 mL to 90°C of liquid ethanol in a bubbler initially intended for the fuel. Nitrogen is circulated above the liquid ethanol to be mixed with the generated ethanol vapors. The mixture of ethanol and nitrogen vapors is circulated for 2 hours at a flow rate of 5 NL / h and a pressure of 200 kPa (2 bara) in the fuel and oxidant supply channels of the bipolar plate. The entire fuel cell is maintained at a temperature of 90°C and the heating lines located at the gas supply conduits are maintained at a temperature of 95°C.

[0119] - Step 3: The fuel cell is then inerted for 30 minutes with nitrogen introduced into the fuel cell through the fuel and oxidant supply channels of the bipolar plate using the bubbler initially intended for the oxidant, the fuel cell being maintained at a temperature of 50°C.

[0120] - The following day, step 2 is performed again for 30 minutes, followed by step 3 for 30 minutes.

[0121] - At the end of the process, the volume of ethanol remaining in the bubbler is 520 mL.

[0122] The fuel cell is then dismantled at a temperature below 50°C. As illustrated in [Fig.3], the bipolar plate can be manually separated from the two adjacent MEAs, respectively at the cathode or anode. In other words, the bipolar plate is separated on the one hand from the anodic gas diffusion layer of one MEA and on the other hand from the cathodic gas diffusion layer of the other MEA.

[0123] As illustrated in [Fig.4], the MEAs are then disassembled by manually separating the anodic and cathodic gas diffusion layers from the assembly. formed by the anodic and cathodic layers and the membrane, the cathodic and anodic layers remaining attached to the membrane. Example 2

[0124] The example below illustrates a method according to the invention, which was carried out on a fuel cell comprising a stack of two identical CCM type AMEs but with different GDLs separated by a bipolar plate comprising fuel and oxidant supply channels. The stack is placed between two end plates.

[0125] The first AME is identical to the AME described in example 1.

[0126] The second AME includes:

[0127] - two gas diffusion layers, anodic and cathodic, marketed under the name SGL24BC by the company SGL;

[0128] - a cathodic layer based on a Pt / C type catalyst loaded with 47% Pt (Tanaka) and an anodic layer based on Pt / C type catalyst loaded with 30% Pt (Tanaka); and

[0129] - a long-chain PFSA-based proton exchange membrane from the company Gore.

[0130] The active surface area of ​​the AMEs is 220 cm2.

[0131] The fuel cell is placed on a test bench. The following steps are implemented.

[0132] - Step 1: The fuel cell is first purged for 30 minutes with dry nitrogen introduced into the fuel cell through the oxidant and fuel supply channels using a bubbler initially intended for the oxidant.

[0133] - Step 2: Ethanol vapors are generated by heating 600 mL to 90°C of liquid ethanol in a bubbler initially intended for fuel. Nitrogen is bubbled into the liquid ethanol to be mixed with the ethanol vapors generated. Two cycles of steps 2a and 2b detailed below are carried out.

[0134] Step 2a: The mixture of ethanol and nitrogen vapors is circulated for 30 minutes at a flow rate of 5 NL / h and a pressure of 300 kPa (3 bara) in the fuel and oxidant supply channels of the bipolar plate. The entire fuel cell is maintained at a temperature of 90°C and the heating lines are maintained at a temperature of 95°C.

[0135] Step 2b: The mixture of ethanol and nitrogen vapors is circulated for 1 hour at a flow rate of 5 NL / h and a pressure of 300 kPa (3 bara) in the fuel and oxidant supply channels of the bipolar plate. The entire fuel cell is maintained at a temperature of 50°C and the heating lines are maintained at a temperature of 95°C.

[0136] - Step 3: The fuel cell is then inerted with wet nitrogen placed in circulation in the fuel and oxidant supply channels of the bipolar plate of the fuel cell, using the bubbler initially intended for the oxidant. The fuel cell is maintained at a temperature of 50°C, the heating lines at 70°C, and the bubbler at 60°C.

[0137] - At the end of the process, the volume of ethanol remaining in the bubbler is 480 mL.

[0138] The fuel cell is then dismantled at a temperature below 50°C.

[0139] The bipolar plate can be manually separated from the two adjacent MEAs as detailed in example 1.

[0140] The two MEAs of the fuel cell are then disassembled by manually separating the membrane from the anodic and cathodic gas diffusion layers, the anodic and cathodic layers remaining secured to the anodic and cathodic gas diffusion layers respectively.

[0141] For FAME comprising Freudenberg GDLs, it is observed that the separation is facilitated in example 2 compared to example 1.

Claims

Claims

1. A method of disassembling a fuel cell (100) comprising: a) providing a fuel cell (100) comprising at least one stack comprising two membrane-electrode assemblies (10) and a bipolar plate (20) sandwiched between the membrane-electrode assemblies (10), each membrane-electrode assembly (10) comprising an anode comprising an anodic gas diffusion layer (45) and an anodic layer (35), a cathode comprising a cathodic gas diffusion layer (48) and a cathodic layer (38), and a proton exchange membrane (40) sandwiched between the anode and the cathode; b) introducing into the fuel cell (100) a mixture comprising a disassembly fluid in the gaseous state capable of inducing a volume expansion of the membrane (40) and a gas inert with respect to the anodic layer (35) and the cathodic layer (38);and c) bringing the membrane-electrode assemblies (10) into contact with the mixture, the absolute disassembly pressure of the mixture being strictly greater than 100 kPa.;

2. Method according to the preceding claim, according to which the bipolar plate (20) comprises one or more fuel supply channels for supplying the membrane-electrode assemblies (10) with fuel and one or more oxidant supply channels for supplying the membrane-electrode assemblies (10) with oxidant, and the mixture is introduced in step b) into the fuel cell (100) via the fuel supply channel(s) and / or via the oxidant supply channel(s).

3. Method according to the preceding claim, according to which the mixture is introduced in step b) into the fuel cell (100), preferably simultaneously, through the fuel supply channel(s) and through the oxidant supply channel(s), and the anode and the cathode are brought into contact in step c), preferably simultaneously, with the mixture at the absolute disassembly pressure.

4. A method according to any preceding claim, wherein the disassembly fluid diffuses into the membrane (40) in step c).

5. Method according to any one of the preceding claims, according to which the absolute disassembly pressure of the mixture in step c) is strictly less than 500 kPa, in particular between 150 kPa and 350 kPa, more preferably between 200 kPa and 300 kPa.

6. A process according to any one of the preceding claims, wherein the temperature of the mixture in step c) is between 15°C and 100°C, in particular between 78°C and 100°C, preferably between 78°C and 95°C.

7. Method according to any one of the preceding claims, according to which step c) comprises bringing the membrane-electrode assemblies (10) into contact with the disassembly fluid in the gaseous state, the mixture preferably being in step c) at an absolute pressure of between 100 kPa and 500 kPa and at a temperature of between 78°C and 100°C.

8. Method according to any one of the preceding claims, according to which step c) comprises bringing the membrane-electrode assemblies (10) into contact with the disassembly fluid at least partially in the liquid state, the mixture preferably being in step c) at an absolute pressure of between 100 kPa and 500 kPa and at a temperature of between 15°C and 70°C.

9. Method according to any one of the preceding claims, according to which the disassembly fluid is chosen from solvents and their mixtures, in particular from polar solvents and their mixtures, preferably from protic polar solvents and their mixtures, in particular from alcohols and their mixtures.

10. A method according to any one of the preceding claims, wherein the disassembly fluid is selected from dimethyl sulfoxide (DMSO), acetone, N,N-dimethylformamide (DMF), acetonitrile, ethyl acetate, methanol, ethanol, isopropanol, water, hexafluoroisopropanol, formic acid, acetic acid, ammonia and mixtures thereof, preferably from ethanol, isopropanol and mixtures thereof, more preferably is ethanol.

11. A method according to any preceding claim, wherein the inert gas is selected from argon and nitrogen, preferably nitrogen.

12. Method according to any one of the preceding claims, comprising a step b') prior to step b), in which the mixture is formed by evaporation of the disassembly fluid, in particular by heating to a temperature greater than or equal to the boiling point of the disassembly fluid, and bringing the disassembly fluid into contact with the inert gas, the contacting being simultaneous with or subsequent to the evaporation.

13. A method according to any preceding claim, wherein the mixture comprises from 63% to 97% by volume of the disassembly fluid and from 3% to 37% by volume of the inert gas.

14. Method according to any one of the preceding claims, comprising, prior to step b), a step of purging the fuel cell (100) by circulating in the fuel cell (100), in particular in the fuel supply channel(s) and / or in the oxidant supply channel(s), a purging fluid, preferably argon or nitrogen, in particular nitrogen.

15. Method according to any one of the preceding claims, comprising, at the end of step c) and preferably prior to dismantling the fuel cell (100), a step of inerting the fuel cell (100) by circulation in the fuel cell (100), in particular in the fuel supply channel(s) and / or in the oxidant supply channel(s), of an inerting fluid, in particular nitrogen, preferably wet.

16. Disassembly method according to any one of the preceding claims, further comprising a step d), subsequent to step c), where appropriate subsequent to the inerting step, during which the bipolar plate (20) and at least one membrane-electrode assembly (10) in contact with the bipolar plate (20), in particular the two membrane-electrode assemblies (10) in contact with the bipolar plate (20), are separated from each other and / or at least two of said layers and / or the membrane (40) and at least one of the layers in contact with the membrane (40) are separated from each other, preferably at least two of said layers and / or the membrane (40) and at least one of the layers in contact with the membrane (40) are separated from each other.

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