Fuel cell disassembly process

Abstract

Method for dismantling a fuel cell. Method for dismantling a fuel cell comprising: a) the provision of a fuel cell comprising at least one stack having two membrane-electrode assemblies and a bipolar plate sandwiched between the membrane-electrode assemblies, each membrane-electrode assembly comprising an anode having an anodic gas diffusion layer and an anodic layer, a cathode having a cathodic gas diffusion layer and a cathodic layer, and a proton exchange membrane sandwiched between the anode and the cathode; b) the introduction into the fuel cell of a mixture comprising a dismantling fluid in the gaseous state capable of inducing volumetric 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 the abstract: None;

Description

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

[0001] The present invention relates to the field of fuel cell recycling, and in particular to end-of-life fuel cell stacks. More specifically, it relates to a method for disassembling a proton exchange membrane fuel cell (PEMFC). It relates in particular to the disassembly of the membrane-electrode assemblies (AMEs) of a PEMFC. 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], which shows an example of a PEMFC fuel cell, a PEMFC 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 supply the oxidant to the cathode layer of one membrane-electrode assembly and the fuel to the anodic layer of the adjacent membrane-electrode assembly. Furthermore, they electrically connect in series the adjacent membrane-electrode assemblies between which they are interposed. The fuel cell 100 may also include terminal plates 28 that sandwich all the membrane-electrode assemblies and bipolar plates, and that press the bipolar plates 20 against the membrane-electrode assemblies 10 to ensure a good electrical connection and a good seal within the fuel 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 polymer-based. The anodic layer 35 and the cathodic layer 38 each comprise a catalyst and are the site of the anodic and cathodic electrochemical reactions. The membrane-electrode assembly further comprises, on either side of the membrane, gas diffusion layers (GDLs) anodic 45 and cathodic 48 arranged respectively on the side of the anodic layer 35 and of the cathodic layer 38 relative to the membrane. The anodic gas diffusion layers 45 and cathodic gas diffusion layers 48 collect the electric current and allow the supply of reactive gas, and the removal of water and heat produced within the membrane-electrode assembly. The membrane-electrode assembly may further include a reinforcement and / or a seal 30 to ensure the tightness of the membrane electrode assembly (MEA) to the fuel and the oxidizer.

[0005] Several types of AME are known.

[0006] The membrane-electrode assembly can 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, with the gas diffusion layers then being placed on top of the anodic and cathodic layers. Hot pressing of the MEA can be used to ensure effective bonding 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 or cathodic layer onto 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 used to ensure effective bonding 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 AMEs, is generally sought. To this end, it has been proposed to disassemble the AMEs in order to recover and separate their different components.

[0009] US 5,718,984 A describes, for example, the recovery of an electrolytic membrane using methanol and hydrogen peroxide, which are toxic and / or environmentally unfriendly. Methanol cannot be reused due to a dissolution reaction. It is also known that hydrogen peroxide causes the 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 battery. The method includes a first step of shredding the AME, which makes the steps of separating the elements from 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 recycling and / or disassembly processes for 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 prior disassembly of the fuel cell and / or the use of a large quantity of solvent, and / or the implementation of complex separation steps.

[0014] Thus, there is a need for a process which is simple, quick 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. Description of the invention

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

[0016] It relates to a method for disassembling a fuel cell comprising: a) the supply of 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) the introduction into the fuel cell of a mixture comprising a disassembly fluid in a gaseous state capable of inducing a volumetric expansion of the membrane and a gas inert with respect to the anodic and cathodic layers; and c) the contacting of the membrane-electrode assemblies 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, means to designate at least two layers whatsoever 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, particularly under pressure, in step c) reaches the membrane through the gas diffusion layers and the cathodic and anodic layers. The disassembly fluid then diffuses to the membrane, generating a volumetric expansion of the membrane. The transfer of the fluid within the assembly induces a reduction in the cohesive 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 AMEs 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 process can allow the disassembly of the AMEs while preserving the physical integrity of the layers and the membrane of the AMEs, in particular the gas diffusion layers and the membrane. It is therefore possible to eliminate subsequent separation steps.

[0020] The process also allows for the disassembly of a fuel cell, particularly the AMEs, directly by processing the fuel cell, without a prior dismantling step. All the AMEs of a fuel cell can then be processed 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 AMEs adjacent to the bipolar plate. The fuel cell disassembly process thus allows for the rapid and efficient disassembly of several AMEs.

[0021] The process also makes it possible, by using the disassembly fluid in a gaseous state, in combination with an inert gas acting as a carrier gas, to significantly reduce the amount of solvent used to separate the various components of a fuel cell, particularly the components of the AMEs. Furthermore, the disassembly fluid in a gaseous state limits the solubilization of the fuel cell components.

[0022] The method also allows the disassembly of most known AMEs. In particular, it is suitable for disassembling CCM-type AMEs and CCB-type AMEs.

[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 a volumetric 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, "catalytic layers," unless otherwise indicated, refers to one or both of the cathodic layer, also called the cathodic catalytic layer, and the anodic layer, also called the 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 readability.

[0027] [Fig.2] schematically represents, in an exploded view, an example of an 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 cathode side 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 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 AMEs all being separated by a bipolar plate. In particular, the stack may comprise more than 5 membrane-electrode assemblies, notably more than 10 membrane-electrode assemblies, or even more than 200 membrane-electrode assemblies.

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

[0032] They may further include one or more anodic discharge channels and / or one or more cathodic discharge channels to purge the fuel cell of anodic reaction products and cathodic 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 can be gas-tight except for the fuel supply channels, oxidant supply channels, anodic exhaust channels and cathodic exhaust channels.

[0036] The fuel cell may include end plates sandwiching the stack. The end plates may include fuel or oxidant supply channels to feed 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] Membrane-electrode assemblies can be of the TLC or CCB type. In particular, membrane-electrode assemblies can 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 pour cells à combustible : structure et transport. Amplification de la diffusion neutron. 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 main fluorocarbon chain, especially a perfluorinated one, for example of the polytetrafluoroethylene (PTFE) type such as Teflon®-type chains, onto which are grafted pendant chains, especially perfluorinated ones, for example of the perfluorovinyl ether type, terminated by a sulfonate ionic group. Examples of proton exchange membranes based on perfluorinated polymers are Nafion®, Flemion™ (Asahi Glass), Aciplex-S™ (Asahi Chemical), Dow™ (Dow Chemical), Hyflon™ (Solvay-Solexis) and Aquivion™ (Solvay) type membranes. An example of a proton exchange membrane based on sulfonated perfluorinated polymer is the Nafion® type membrane. Alternatively, the proton exchange membrane can be a membrane comprising, or even consisting of, a non-fluorinated polymer with an aromatic skeleton, in particular chosen from polymers with 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 a composite or non-composite membrane, the sulfonated perfluorinated polymer more preferably comprising a main fluorocarbon chain of the polytetrafluoroethylene (PTFE) type onto which are grafted pendant chains of the perfluorovinyl ether type terminated by a sulfonate ionic group. Preferably, the proton exchange membrane based on the sulfonated perfluorinated polymer is a Nafion® type or Gore-Select® type membrane, in particular a Nafion® type membrane.

[0043] The proton exchange membrane may have a thickness 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 selected 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 pm, in particular between 2 and 10 pm.

[0046] The cathode layer may comprise a catalyst selected from platinum and bimetallics 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 pm, in particular between 5 and 20 pm.

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

[0048] Membrane-electrode assemblies may comprise a superposition of layers formed successively 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 may have been previously used as an electrochemical generator, especially for several thousand hours. Preferably, the fuel cell supplied in step a) has not undergone any disassembly or modification of its structure. For example, a fuel cell, especially a used one, may be supplied directly in step a), particularly without any prior steps.

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

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

[0052] The purging step may include bringing the membrane-electrode assemblies into contact with the purging fluid.

[0053] The purging step aims to purge the fuel cell, in particular the membrane-electrode assemblies, of residual reactive gases, including hydrogen and oxygen, especially air, for example present in the fuel or oxidant feed channel(s) or adsorbed on the MEA layers. This preliminary step helps reduce the risk of ignition due to contact between the catalyst(s) of the catalytic layers, namely 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), so as to reach the anode and the cathode, preferably simultaneously.

[0056] The mixture can 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 can 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 can be introduced in step b) at an absolute pressure of the mixture 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 can 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 can 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 can be chosen from solvents and their mixtures, in particular from polar solvents and their mixtures, preferably from protic polar solvents and their mixtures, especially from alcohols and their mixtures.

[0061] In particular, 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, the disassembly fluid is selected from ethanol, isopropanol, and mixtures thereof; more preferably, ethanol.

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

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

[0064] By "inert gas with respect to the anodic and cathodic layers" 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 can 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 the inert gas in step b). In particular, the mixture consists of the disassembly fluid and the inert gas.

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

[0069] Preferably, the mixture is free of compounds that 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, and more specifically, is free of dioxygen, dihydrogen, and water. The mixture is advantageously inert with respect to the anodic and cathodic layers.

[0070] The process may include a step b') prior to step b), in which the mixture is formed by evaporating the disassembly fluid, in particular by heating it to a temperature greater than or equal to the boiling point of the disassembly fluid, and contacting the disassembly fluid with the inert gas, such contact 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 saturated with vapor of the disassembly fluid.

[0071] The evaporation of the disassembly fluid can be carried out directly in the system for generating the humidification of the fuel 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 can be bubbled in the disassembly fluid in its liquid state during evaporation to obtain the mixture, which allows the inert gas to become saturated with vapor from the disassembly fluid. Alternatively, the inert gas can be introduced into the disassembly fluid in its gaseous state obtained by evaporation.

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

[0074] Introducing the mixture into the fuel cell can allow the circulation of the The mixture circulates throughout the fuel cell, reaching all the active membrane elements (AMEs). Specifically, the mixture can be circulated in a closed or open loop. In a closed loop, the vapor exiting the fuel cell is condensed to recover the solvent for reuse. When circulating in an open loop, the mixture can be bubbled in water after circulating through the fuel cell to dissolve the vapor 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 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 contact in step c) can be achieved by circulating the mixture in the fuel cell to the membrane-electrode assemblies, in particular to the cathode or to the anode of the membrane-electrode assemblies.

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

[0079] Preferably, the anode and 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, specifically 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), particularly in such a way as to be absorbed by the membrane. In particular, the contact in step c) allows the disassembly fluid to induce a volumetric expansion of the membrane.

[0081] The absolute disassembly pressure of the mixture at 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 bar), in particular less than or equal to 350 kPa (3.5 bar), more particularly less than or equal to 300 kPa (3 bar). The pressure difference between the anodic and cathodic compartments is preferably less than or equal to 50 kPa (0.5 bar). The risk of damage to the pressurized membrane is thus reduced.

[0083] In particular, the absolute disassembly pressure of the mixture at step c) can 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) can 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) can be in liquid or gaseous state.

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

[0087] Alternatively, step c) may involve contacting the membrane-electrode assemblies with the disassembly fluid, at least partially in a liquid state, which facilitates the subsequent disassembly of an AME. Preferably, the mixture in step c) is at an absolute pressure between 100 kPa (1 bara) and 500 kPa (5 bara) and at a temperature between 15°C and 70°C. The fluid may undergo condensation in the fuel cell by modifying the temperature and / or 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. Using the disassembly fluid in a liquid state can advantageously reduce the cohesive force between the catalytic layers and the membrane.

[0088] According to a particular embodiment, step c) may include contacting the membrane-electrode assemblies with the disassembly fluid in the gaseous and liquid states. In particular, step c) may include one or more steps c1) in which the fuel cell membrane-electrode assemblies are contacted with the disassembly fluid in the gaseous state, and one or more steps c2) in which the fuel cell membrane-electrode assemblies are contacted 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 bar) in steps c1) and c2). In particular, step c) includes at least two cycles comprising step c1) and step c2).

[0089] The duration of step c) can 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 AME layers, or even between all said layers in contact, and / or at least between one of said AME layers and the AME membrane or even between the membrane and all layers in contact with the membrane, and / or between the bipolar plate(s) and at least one AME in contact with the bipolar plate(s) or even between the bipolar plate(s) and all AMEs in contact with the bipolar plate(s).

[0090] The duration of step c) can 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 AMEs of the fuel cell or between the membrane of the AMEs and each of the anodic and cathodic catalytic layers of the AMEs.

[0092] The layers and / or the membrane, in particular the layers and the membrane, obtained after step c) are self-supporting, i.e., they do not break under 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 in the fuel cell.

[0093] Preferably, the integrity of the layers and / or the membrane, in particular the layers and the membrane, is maintained 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 not by more than 1%, compared to the length, width and thickness measured in step a).

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

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

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

[0097] The inerting step aims to expel vapor residues from 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 solvent inhalation.

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

[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), optionally subsequent to the inerting step, in which the bipolar plate and at least one membrane-electrode assembly in contact with the bipolar plate, in particular both 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 apart, for example by stretching, rolling, 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 include the separation of the bipolar plate(s) from the anodic and cathodic gas diffusion layers of the adjacent AMEs.

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

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

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

[0105] The process may further include 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 process may further include 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 them 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 period of less than 5 minutes, in particular between 1 and 2 minutes.

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

[0110] The process may further include the recovery of the mixture, in particular the disassembly fluid. The recovered disassembly fluid may, in particular, be used in a process 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 following example illustrates a method according to the invention, which was carried out on a fuel cell comprising a stack of two CCM-type AMEs separated by a bipolar plate having fuel and oxidant supply channels. The stack is placed between two terminal plates. The AMEs comprise:

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

[0113] - a cathode layer based on a Pt / C type catalyst loaded with 47% Pt (Tanaka) and an anodic layer based on a 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 AME 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 is 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 Liquid ethanol is placed in a bubbler initially intended for fuel. Nitrogen is circulated above the liquid ethanol to mix with the generated ethanol vapors. The ethanol-nitrogen vapor mixture is circulated for 2 hours at a flow rate of 5 NL / h and a pressure of 200 kPa (2 bar) through the fuel and oxidizer feed channels of the bipolar plate. The entire fuel cell is maintained at a temperature of 90°C, and the heating lines in the gas feed lines are maintained at 95°C.

[0119] - Step 3: The fuel cell is then inert for 30 minutes with nitrogen is 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 disassembled 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 the anode. In other words, the bipolar plate is separated on one side from the anodic gas diffusion layer of one MEA and on the other side from the cathodic gas diffusion layer of the other MEA.

[0123] As illustrated in [Fig.4], the AMEs 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 following example 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 having fuel and oxidant supply channels. The stack is placed between two terminal plates.

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

[0126] The second AME comprises:

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

[0128] - a cathode layer based on a Pt / C type catalyst loaded with 47% Pt (Tanaka) and an anodic layer based on a 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 AME 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 is 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 Liquid ethanol is placed in a bubbler initially intended for fuel. Nitrogen is bubbled into the liquid ethanol to mix with the generated ethanol vapors. Two cycles of steps 2a and 2b, detailed below, are performed.

[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 bar) 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 bar) 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. Circulation in the fuel and oxidant supply channels of the fuel cell's bipolar plate is facilitated by 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 disassembled at a temperature below 50°C.

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

[0140] The two AMEs 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 attached respectively to the anodic and cathodic gas diffusion layers.

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

Claims

Demands

1. Method for disassembling a fuel cell (100) comprising: a) supplying 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) the introduction into the fuel cell (100) of a mixture comprising a disassembly fluid in the gaseous state capable of inducing a volumetric 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. A method according to the preceding claim, wherein the bipolar plate (20) has 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) through the fuel supply channel(s) and / or through the oxidant supply channel(s).

3. A method according to the preceding claim, wherein 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 cathode are brought into contact in step c), preferably simultaneously, with the mixture at the absolute disassembly pressure.

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

5. A method according to any one of the preceding claims, wherein the absolute disassembly pressure of the mixture at 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 method according to any one of the preceding claims, wherein the temperature of the mixture at 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. A method according to any one of the preceding claims, wherein 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 between 100 kPa and 500 kPa and at a temperature between 78°C and 100°C.

8. A method according to any one of the preceding claims, wherein 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 between 100 kPa and 500 kPa and at a temperature between 15°C and 70°C.

9. A method according to any one of the preceding claims, wherein the disassembly fluid is selected from solvents and mixtures thereof, in particular from polar solvents and mixtures thereof, preferably from protic polar solvents and mixtures thereof, in particular from alcohols and mixtures thereof.

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 ethanol.

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

12. A method according to any one of the preceding claims, comprising a step b') prior to step b), wherein 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 contact being simultaneous with or subsequent to the evaporation.

13. A method according to any one of the preceding claims, 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. A 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. A 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 circulating in the fuel cell (100), in particular in the fuel supply channel(s) and / or in the oxidant supply channel(s), an inerting fluid, in particular nitrogen, preferably wet.

16. A disassembly method according to any one of the preceding claims, further comprising a step (d) subsequent to step (c), optionally 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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