Ion-conducting membrane, its preparation method and application

Abstract

The present invention relates to an ion-conducting membrane comprising a matrix of a crosslinked polymer and a powder of an ion-conducting material, the powder being dispersed in a continuous solid matrix and occupying 33% to 66% by volume of the total volume of the ion-conducting membrane.

Description

[Technical Field]

[0001] The present disclosure relates to ion-conducting membranes, particularly anionic and / or cationic membranes, for fuel cells, especially of the polymer exchange membrane (PEM) type. [Background technology]

[0002] One of the essential components for the proper functioning of PEM-type fuel cells is the membrane that conducts ions inside the cell. Traditionally, these cells operate in the cationic mode, and this function is ensured by cation-conducting (particularly proton-conducting) ionomer materials such as Nafion®. However, this creates technical challenges by imposing a cationic operating system. Furthermore, it also requires the use of platinum as a catalyst. These technical challenges hinder the development of such devices. Platinum is a rare and expensive material and needs to be replaced by other, less expensive metals, such as nickel. Such metals are currently used in high-power stationary equipment operating at high temperatures to function under anionic conditions, thereby replacing platinum. However, these processes require high-temperature operation, and therefore it would be useful to provide a membrane that allows operation at ambient temperatures. This would open up the possibility of compact anionic fuel cells.

[0003] To overcome these difficulties, anion-conducting materials have been developed.

[0004] In this regard, WO 2015 / 044308 A1 describes a cationic substrate formed from an inorganic porous substrate, the pore surface of which is coated with silica gel functionalized with cationic groups. The described cationic substrate is intended to be used as an anionic membrane in a fuel cell.

[0005] Another strategy is to functionalize Nafion® to convert it into an anion conducting material.

[0006] The aforementioned approach was described in particular by Salerno Holly LS, et al. ("Anion exchange membranes derived from Nafion precursor for the alkaline fuel cell," Journal of Polymer Science Part B: Polymer Physics, 2012, 50, pp. 552-562). This paper reports the need for robust hydroxide-conducting membranes to obtain robust, durable, and low-cost alkaline fuel cells (AFCs). Nafion®-based anion exchange membranes (AEMs) have been synthesized by amination of Nafion® precursor membranes with 1,4-dimethylpiperazine. This initial reaction produces AEMs with covalently bound dimethylpiperazinium cations neutralized with fluoride anions, while a subsequent ion exchange reaction produces membrane-conducting hydroxide ions. These AEMs have high thermal stability and thermal transition temperatures different from those of Nafion®.

[0007] Modified Nafion® membranes are also known from Min-suk J. Jung et al. ("A Perfluorinated Anion Exchange Membrane with a 1,4 Dimethylpiperazinium Cation", J. Mater. Chem., 2011, 21, (17), pp 6158-6160), who showed that perfluorinated anion exchange membranes with 1,4-dimethylpiperazinium cations exhibit better hydroxide ion conductivity and a one-third reduction in water uptake compared to hydrocarbon AEMs with the same cations. The perfluorinated AEMs were stable in 2 M KOH at 60°C for 30 days and showed good performance in fuel cells.

[0008] Modified Nafion® membranes are also known from Schmidt, C. et al. ("Modification of Nafion Membranes by Impregnation with Ionic Liquids", Chemical Engineering & Technology, 2008, 31, No. 1, pp. 13-22), who describe the impregnation of a Nafion® 117 membrane with different imidazolium (1-hexyl-3-methyl-imidazolium / HMI, 1-butyl-3-methyl-imidazolium / BMI) and pyrrolidinium (1-butyl-1-methyl-pyrrolidinium / BMPyr) based ionic liquids with hydrophobic (tris(pentafluoroethyl)trifluorophosphate / FAP, bis(trifluoromethylsulfonyl)imide / BTSI, hexafluorophosphate / PF6) anions and more hydrophilic (tetrafluoroborate / BF4) anions. During this treatment, the cations of the ionic liquid partially replace the protons of the sulfonic acid groups in Nafion®. According to this paper, the modification of Nafion® with ionic liquids bearing bulky, hydrophobic FAP anions appears promising.

[0009] WO 2021 / 083922 A1 also describes a method for converting Nafion® by polymerizing in the pores of the material a monomer having a quaternary ammonium group that can ionically interact with the sulfonate groups of Nafion®.

[0010] However, the proposed method is complex to implement.

[0011] Nafion®, used as a substrate in most of the proposed methods, is also expensive. Furthermore, Nafion® is geometrically unstable, meaning that it is difficult to incorporate into fuel cells. Finally, measures must be taken to overcome its sensitivity to humidity.

[0012] The object of the present invention is to solve all or part of the above mentioned technical problems.

[0013] In particular, the present invention aims to provide alternative ion (cation or anion) conducting membranes that are simplified in manufacture compared to prior art membranes.

[0014] It is a further object of the present invention to provide an ion (cation or anion) conducting membrane that has reduced manufacturing costs compared to prior art membranes. In particular, the present invention aims to provide an ion conducting material prepared from a material other than Nafion®.

[0015] It is a further object of the present invention to provide an ion (cation or anion) conducting membrane having improved mechanical strength compared to prior art membranes.

[0016] It is a further object of the present invention to provide an ion (cation or anion) conducting membrane that can be used in fuel cells at ambient temperatures. It is also an object of the present invention to provide an anionic membrane that allows for the replacement of platinum in fuel cells with other metals, particularly less expensive metals such as nickel. An even further object is to provide an anionic membrane that is stable in alkaline media.

[0017] It is therefore an object of the present invention to provide a stable, low-cost membrane with electrical conductivity performance approaching that of conventional proton membranes used in fuel cells.

[0018] It is a further object of the present invention to provide a membrane that can be used in biologically compatible devices, especially devices intended for implantation in the human or animal body. Summary of the Invention

[0019] The present invention relates first to an ion-conducting membrane comprising a matrix of a crosslinked polymer and a powder of an ion-conducting material, the powder of the ion-conducting material being dispersed in a solid continuous matrix and occupying 33% to 66% by volume of the total volume of the ion-conducting membrane.

[0020] In one preferred embodiment, the solid continuous matrix is ​​obtained by crosslinking, in particular chemical or physical crosslinking, of a crosslinkable polymer selected from among polysiloxanes, thermosetting resins, polyamides, polyesters, polyolefins, and mixtures thereof, preferably selected from among polydimethylsiloxanes, epoxy resins, and mixtures thereof.

[0021] Preferably, the powder of the ion-conductive material has a particle size of 20 μm or less, preferably in the range of 100 nm to 10 μm.

[0022] This small particle size of the powder of ion-conducting material contributes to obtaining membranes with good conductivity and mechanical properties, in particular, this small size makes it possible to obtain membranes with smaller thicknesses, thereby improving their flexibility and opening up new perspectives for the application of these membranes.

[0023] Preferably, the powder of the ion-conductive material has a particle size equal to or smaller than half the thickness of the ion-conductive membrane.

[0024] More preferably, the ionically conductive material is selected from among inorganic silicon-based materials, optionally functionalized organic materials such as ion exchange resins, or any mixture thereof.

[0025] Advantageously, the ionically conductive material is chosen from among silicates, optionally functionalized ion exchange resins, and mixtures thereof.

[0026] In one embodiment, the ion-conducting membrane of the present invention is porous, preferably having a porosity in the range of 1% to 25%, more preferably in the range of 3% to 20%.

[0027] The subject of the present invention is also a method for preparing an ion-conducting membrane as defined above and described in detail below, said method comprising the steps of: a) providing powders of (i) a crosslinkable polymer and (ii) an ionically conductive material; b) dispersing the powder in the crosslinkable polymer to form a homogeneous mixture, the powder comprising 33% to 66% by volume of the total volume of the mixture; c) forming a film from the mixture obtained in b), in particular by depositing the mixture on the surface of a substrate; d) crosslinking the crosslinkable polymer.

[0028] In one particular embodiment, the method of the present invention includes a prior step for functionalizing a powder of ion-conducting material.

[0029] A further subject of the present invention is a fuel cell comprising an ion-conducting membrane as defined above and described in detail below, or an ion-conducting membrane as defined above and obtained by the method described in detail below.

[0030] Finally, the present invention relates to a biocompatible device comprising an ion-conducting membrane as defined above and described in detail below, or an ion-conducting membrane as defined above and obtained by the method described in detail below. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention first relates to an ion-conducting membrane.

[0032] By "ion-conducting membrane" is meant a semipermeable membrane that allows ions to be conducted between a first medium and a second medium on either side of the membrane. In particular, the ion-conducting membrane of the present invention is a material that can transport ions, optionally selectively allowing these ions to pass through the membrane from the first medium to the second medium, but is impermeable to gases such as dioxygen or dihydrogen.

[0033] The ion-conducting membranes of the present invention typically comprise a matrix of cross-linked polymer in which a powder of ion-conducting material is dispersed.

[0034] The cross-linked polymer controls the mechanical properties (flexibility or stiffness) of the membrane, while the powder of ion-conducting material allows for the selection of the type of ion conductivity.

[0035] matrix The purpose of the matrix of the present invention is to act as a substrate for the ionically conductive material, in particular, the matrix of the present invention provides good mechanical strength.

[0036] Preferably, the matrix of the present invention is solid.

[0037] Also preferably, the matrix of the present invention is continuous.

[0038] A crosslinked polymer in the present invention means a polymer having covalent chemical bonds between the polymer backbones.

[0039] The matrix of the membrane of the present invention is typically obtained by crosslinking a crosslinkable polymer.

[0040] Preferably, the crosslinkable polymer is a non-fluorinated polymer, ie, does not contain fluorine atoms.

[0041] Preferably, the crosslinkable polymer is non-ionically conductive.

[0042] Preferably, the crosslinkable polymer is selected from the group consisting of polysiloxanes, thermosetting resins, polyamides, polyesters, polyolefins, epoxy resins, polyacrylamides, and mixtures thereof.

[0043] Preferably, when the crosslinkable polymer is selected from among polysiloxanes, the crosslinkable polymer is a polyalkylsiloxane, in particular one in which the alkyl groups are C1 to C 10It is preferably selected from polyalkylsiloxanes selected from alkyl groups, more preferably C1 to C5 groups, and even more preferably C1 to C3 groups.

[0044] Preferably, the polysiloxane has alkyl groups each independently having a C1 to C 10 Preferably, the alkyl group is selected from polydialkylsiloxanes selected from alkyl groups, more preferably C1 to C5 groups, and even more preferably C1 to C3 groups.

[0045] More preferably, the alkyl substituents are all the same and are C1 to C 10 It is preferably selected from alkyl groups, more preferably C1 to C5 groups, and even more preferably C1 to C3 groups.

[0046] Advantageously, when the cross-linkable polymer is chosen among the polysiloxanes, it is chosen among the polydimethylsiloxanes (PDMS, polydimethylsiloxane).

[0047] Among the thermosetting resins, mention may in particular be made of phenolic, ester or epoxy resins.

[0048] Preferably, when the crosslinkable polymer is chosen from among thermosetting resins, it is chosen from among epoxy resins, more preferably from among resins of the epoxidized maleated castor oil type.

[0049] Epoxidized maleated castor oil type resins are typically obtained by reacting castor oil with maleic anhydride, followed by an epoxidation step.

[0050] Among the polyamides, mention may in particular be made of nylon, polyacrylamide, polybisacrylamide or copolymers of acrylamide and bisacrylamide.

[0051] Among the polyesters, mention may in particular be made of polyethylene terephthalate or polybutylene terephthalate.

[0052] Among the polyolefins, mention may be made in particular of homopolymers of olefins such as polyethylene, polypropylene, polybutylene, or copolymers of different olefins.

[0053] As examples of olefin copolymers, mention may be made in particular of copolymers having monovinyl aromatic hydrocarbon units, typically copolymers of styrene and divinylbenzene.

[0054] Advantageously, the cross-linkable polymer is chosen from the group consisting of polysiloxanes, thermosetting resins, and mixtures thereof.

[0055] More preferably, the crosslinkable polymer is selected from the group consisting of polydimethylsiloxane, epoxy resin, and mixtures thereof.

[0056] Crosslinking of the polymers can be achieved by any method known to those skilled in the art, for example by chemical crosslinking, in particular using sulfur, or by physical crosslinking, for example by heat treatment or electron beam irradiation.

[0057] The stiffness and / or flexibility of the final ion-conducting membrane can be adjusted by selecting the starting crosslinkable polymer used to form the matrix. In particular, the selection of one or more polymers to prepare a membrane with specific mechanical properties can be performed by a person skilled in the art. Thus, the present invention makes it possible to obtain rigid membranes, but also flexible membranes depending on the polymers used.

[0058] Preferably, the matrix occupies 33% to 66% by volume of the total volume of the ion conductive membrane.

[0059] Ion Conductive Powder The membrane of the present invention further comprises at least one powder of an ionically conductive material, said powder of an ionically conductive material being dispersed in the matrix.

[0060] In one preferred embodiment, the powder of the ion-conducting material is uniformly distributed within the matrix.

[0061] In the present invention, the term "ionically conductive material" refers to a material that can transport ions. The ionic conduction behavior of a material is evaluated by measuring the ionic conductivity σi of the material.

[0062] The ionic conductivity of a material can be determined by any method known to those skilled in the art. For example, the ionic conductivity can be measured as follows: a pellet of the material whose ionic conductivity is to be determined is mixed with a powder of the material at 5 t / cm 2 The pellet is prepared by pressing it under a pressure of 1000 kJ / cm² and subsequently sintering it for 2 hours at a temperature 30% below the melting temperature (expressed in K) of the material in question. A gold film is deposited on the surface of the pellet to improve the contact between the current collector and the sample. Finally, the pellet is placed between two nickel collectors on the surface.

[0063] Impedance is measured by applying a sinusoidal voltage of 10 mV amplitude to the pellet at different frequencies (1 MHz to 0.01 Hz). In a Nyquist diagram, the blocking electrode signal can be seen at the lowest frequency. The intersection point between the extrapolation of the blocking electrode signal and the axis of the true impedance value RT corresponds to the sum of the ionic resistance Ri and electronic resistance Re of the pellet.

[0064] The ionic resistance Ri is calculated from the relationship Ri=RT-Re, and the ionic conductivity σi is calculated by applying the following equation:

number

[0065] Preferably, the ion-conducting material has a conductivity of 0.1 Sm -1More than 50 S.m -1 It has an ionic conductivity of at least 1000 vol%.

[0066] More preferably, the ion-conducting material has a conductivity of 0.1 Sm -1 ~100 S.m -1 , preferably 10 S.m -1 ~100 S.m -1 The ionic conductivity ranges from 0.1 to 0.5.

[0067] The type of ion-conducting material is not particularly limited, and in particular, the ion-conducting material can be selected from organic or inorganic materials.

[0068] Organic materials suitable for the present invention are typically those that contain charged chemical groups, examples of which include ion exchange resins in particular.

[0069] Among the inorganic materials suitable for the present invention, silicon-based materials can be mentioned in particular.

[0070] By "silicon-based material" in the present invention is meant a material that comprises a network of silicon atoms directly or indirectly bonded to one another.

[0071] As examples of silicon-based materials, mention may be made in particular of silicalite, silica gel or silicates.

[0072] Preferably, when the ionically conductive material is selected from silicates, it is selected from aluminosilicates, more preferably from zeolites, typically from Y-type zeolites.

[0073] Preferably, the ionically conductive material is selected from the group consisting of silicates, ion exchange resins, and mixtures thereof.

[0074] More preferably, the ionically conductive material is selected from the group consisting of aluminosilicates, ion exchange resins, and mixtures thereof.

[0075] Advantageously, the ionically conductive material is selected from the group consisting of zeolites, ion-exchanged ions, and mixtures thereof.

[0076] In one particular embodiment, the powder of ionically conductive material is in the form of a mixture of at least two different ionically conductive materials.

[0077] Preferably, in this embodiment, the powder of ion-conducting material comprises, or more preferably consists of, a first powder of anion-conducting material and a second powder of cation-conducting material, which is particularly suitable for preparing mixed anion- and cation-conducting membranes.

[0078] More preferably, in this embodiment, the membrane of the present invention has a volume of: 33% by volume of a powder of an anion conducting material; 33% by volume of a powder of a cation-conducting material; 33% by volume of a matrix, preferably 34% by volume of a matrix, and preferably consists of these.

[0079] Advantageously, the powder of ion-conductive material has a particle size of 50 μm or less, preferably in the range of 50 nm to 30 μm, more preferably in the range of 100 nm to 10 μm, even more preferably in the range of 500 nm to 8 μm, and even more preferably in the range of 1 μm to 5 μm.

[0080] The particle size of the powder can be measured using any method known to one of ordinary skill in the art, for example, by laser diffraction or dynamic light scattering.

[0081] In one preferred embodiment, the powder of ion-conducting material is porous, preferably having open porosity.

[0082] In the present invention, "material with open porosity" means a material with interconnected pores that form a continuous network within the material.

[0083] Advantageously, the powder of ion-conducting material has a porosity in the range of 5% to 40%, more preferably in the range of 10% to 30%.

[0084] The porosity of the powder can be measured by any method known to those skilled in the art, for example, using a mercury porosimeter.

[0085] Preferably, the powder of the ion conductive material occupies 33 to 66% by volume, more preferably 33 to 55% by volume, and more preferably 40 to 50% by volume, of the total volume of the ion conductive membrane.

[0086] The volume content of the ion-conducting material in the membrane is an important parameter for the material of the present invention. This content follows the law of percolation, which the inventors have discovered is applicable to the matrix of the present invention. The basic concept of this theory is that as the number of bonds in the network increases (through the volume content of the ion-conducting material), global clusters of connected nodes suddenly appear. Therefore, to obtain electrical conductivity, it is essential that this value should not be lower than the threshold for three-dimensional percolation (33%). Furthermore, since too high a content of the ion-conducting material is detrimental to mechanical strength, a maximum limit for the ion-conducting material allows for optimization of the mechanical strength and ionic conductivity of the membrane. Therefore, a range of volume content of the ion-conducting material confers both good conductivity and good mechanical strength to the membrane.

[0087] ion-conducting membrane Preferably, the ion-conducting membrane of the present invention is porous.

[0088] More preferably, the ion-conductive membrane of the present invention has a porosity in the range of 1% to 25%, and even more preferably in the range of 3% to 20%.

[0089] Ion conducting membranes are typically selected from cationic membranes, anionic membranes, and mixed membranes that are partly anionic and partly cationic.

[0090] In a first embodiment, the ion-conducting membrane is cationic. In the present invention, the term "cationic membrane" refers to an ion-conducting membrane that can transport cations but cannot transport anions.

[0091] Cationic membranes typically comprise materials with anionic groups that can interact with the transported cations via electrostatic bonds.

[0092] Cationic membranes can be general or universal, that is, capable of transporting any type of cation.

[0093] Alternatively, the cationic membrane may be specific, i.e., capable of transporting only certain cations or certain families of cations. Examples of selective cationic membranes include the lithium ion-specific cationic membranes routinely used to extract lithium from seawater.

[0094] The general / universal or specific properties of the membrane depend on the chemical nature of the ion-conducting material dispersed in the matrix, and the selection of a suitable conductive material is made by a person skilled in the art according to the desired final properties of the membrane.

[0095] In a second embodiment, the ion-conducting membrane is anionic. In the present invention, the term "anionic membrane" refers to an ion-conducting membrane that can transport anions but cannot transport cations.

[0096] Anionic membranes typically comprise materials having cationic groups capable of interacting with the transported cations via electrostatic bonds.

[0097] Anionic membranes can be general or universal, i.e., capable of transporting all anions, or they can be specific, i.e., capable of transporting only certain anions or certain families of anions.

[0098] The general / universal or specific properties of the membrane depend on the chemical nature of the ion-conducting material dispersed in the matrix, and the selection of a suitable conductive material is made by a person skilled in the art according to the desired final properties.

[0099] In a third embodiment, the ion-conducting membrane is a mixed, partially anionic and partially cationic membrane. In the present invention, the term "mixed, partially anionic and partially cationic membrane" refers to an ion-conducting membrane that can transport both anions and cations. This type of membrane is typically obtained from a mixture of several ion-conducting materials, including at least one anionic material and at least one cationic material.

[0100] For cationic and anionic membranes, general / universal or specific properties can be tailored by selecting ion-conducting materials for both cations and anions.

[0101] In one particular embodiment, the ion conducting membrane of the present invention is an electronically insulating material. The electronic insulating property of the membrane of the present invention is not required for all applications. However, electronic insulation is particularly suitable for ion conducting membranes for fuel cells.

[0102] In the present invention, the term "electronically insulating material" refers to a material that cannot transport electrons. Typically, in the context of the present invention, an electronically insulating material has an electronic resistance of 1 Megohm (MΩ) or greater.

[0103] The electronic resistance of a material can be determined by any method known to those skilled in the art. For example, the electronic resistance can be measured as follows. A pellet of the material whose electrical resistance value is to be determined is placed in a powder of the material at 5 t / cm 2The pellet is prepared by pressing it at 1000 K, followed by sintering it for 2 hours at a temperature 30% lower than the melting temperature (expressed in K). A gold film is deposited on the surface of the pellet to improve the contact between the current collector and the sample. Finally, the pellet is placed between two nickel collectors on the surface. A voltage is applied to the electrode terminals and the change in the current circulating in the pellet is measured as a function of time. The graph obtained by plotting this change in current as a function of the applied voltage is a straight line with a slope corresponding to the electronic resistance Re of the pellet.

[0104] The ion-conductive membrane of the present invention preferably has a thickness in the range of 1 μm to 1 mm, more preferably in the range of 10 μm to 500 μm, even more preferably in the range of 20 μm to 100 μm, and typically 50 μm.

[0105] The present invention is advantageous in that it allows for the preparation of ion-conducting membranes, particularly anionic and / or cationic membranes, that can exhibit various mechanical properties, particularly with regard to stiffness and flexibility. In particular, through the selection of matrix-forming materials, the present invention allows for the tailoring of the final membrane's mechanical properties, particularly with regard to the final membrane's end use. For example, the present invention allows for the preparation of flexible ion-conducting membranes suitable for incorporation into flexible assemblies / devices, such as clothing, particularly for the production of smart clothing. Conversely, the present invention allows for the preparation of rigid ion-conducting membranes particularly suitable for industrial equipment or vehicles.

[0106] Manufacturing method A further subject of the present invention is a method for producing an ion-conducting membrane according to the invention as defined above.

[0107] Preferably, the method of the present invention comprises the following steps: a) providing a powder of (i) a crosslinkable polymer as defined above and (ii) an ionically conductive material as defined above; b) dispersing the powder in the crosslinkable polymer to form a homogeneous mixture; c) forming a film from the mixture obtained in b), in particular by depositing the mixture on the surface of a substrate; d) crosslinking the crosslinkable polymer, preferably in an oven.

[0108] Preferably, in step b), the powder of the ion-conductive material is dispersed in the crosslinkable polymer so that the powder occupies 33% to 66% by volume of the total volume of the mixture of powder and crosslinkable polymer.

[0109] Preferably, the method of the present invention comprises the following steps: a) providing a powder of (i) a crosslinkable polymer as defined above and (ii) an ionically conductive material as defined above; b) measuring by weighing the powders of the crosslinkable polymer and the ion-conducting material, taking into account their respective densities in order to respect the law of permeation, so that each of these two components has a volume greater than 33% and less than 66% of the total volume of the membrane; c) mixing the powder with the crosslinkable polymer to form a homogeneous mixture; d) forming a film of desired thickness from the mixture obtained in c), in particular by depositing the mixture on the surface of a substrate; e) crosslinking the crosslinkable polymer, preferably in an oven.

[0110] Preferably, the amount of powder dispersed in the polymer in step b) is adjusted to obtain a mixture with good spreading properties at ambient temperature and with viscoelastic properties adapted in particular to allow the formation of a film in step c).

[0111] Preferably, the film obtained upon completion of c) has a thickness in the range of 1 μm to 1 mm, more preferably in the range of 10 μm to 500 μm, even more preferably in the range of 20 μm to 100 μm, and typically 50 μm.

[0112] The crosslinking of the polymer in step b) can be carried out by any method known to those skilled in the art, for example, the crosslinking of the polymer can be obtained by chemical crosslinking, in particular with sulfur, or by physical crosslinking, for example by heat treatment or electron beam irradiation.

[0113] In one particular embodiment, the method of the invention comprises, before step b), a preceding step for preparing a powder of ionically conductive material, typically by functionalizing a precursor material, which functionalization step typically makes it possible to modify the ionic conductivity of the precursor material before dispersing it in the crosslinkable polymer.

[0114] In a first embodiment, the precursor material is ionically non-conductive. Therefore, in this first embodiment, the preliminary preparation step consists of a functionalization step of the precursor material, which grafts charged organic groups onto its surface, making it ionically conductive. This grafting step is typically carried out using any method known to those skilled in the art.

[0115] In a second embodiment, the precursor material is ionically conductive. Thus, in this second embodiment, a prior preparation step allows for modification of the conductivity of the precursor material. For example, a functionalization step can be carried out to convert an anion-conducting material into a cation-conducting material. This step of modifying the conductivity of the material can be carried out using any known method, for example, the grafting method described in WO 2021 / 083922 A1.

[0116] Purpose A further subject of the present invention is a device incorporating an ion-conducting membrane as defined above or obtained by the method described above.

[0117] The type of the device is not particularly limited: for example, the device may be a fuel cell, an electrolyzer, a desalination apparatus (or desalination device), a device for extracting lithium from seawater, etc. The invention particularly relates to a fuel cell comprising an ion-conducting membrane as defined above or obtained by the method described above.

[0118] Methods for preparing fuel cells have been described in the prior art and can be applied by analogy.

[0119] Current microcells consist of a stack of membranes and electrodes compressed to ensure a seal.

[0120] The microcells of the present invention can be mass-produced using automated means from the semiconductor industry, and the size and geometry of the cells can be easily adapted.

[0121] Preferably, the fuel cell of the present invention comprises: a cathode part including a cathode; - an anode part containing an anode; one or more devices allowing a water source and / or an oxygen source to be placed in contact with the cathode part; - hydrogenated porous silicon in contact with the anode part; The cathode portion and the anode portion are physically separated by the ion-conducting membrane of the invention.A further subject of the invention is a method for producing dihydrogen, for example from water and oxygen.

[0122] In the present invention, the operating temperature of the fuel cell is typically about 10° C. to about 70° C., preferably ambient temperature (20-25° C.). The reaction is preferably carried out at atmospheric pressure or slightly higher pressure, typically below about 2 bar, typically about 1 bar to 1.5 bar.

[0123] The diffusion media in fuel cells are typically electronic conductors, typically made of woven carbon fibers with porous graphite particles embedded within them. In this case, gas molecules pass through the mesh of the woven fibers, and electrons are carried by the carbon fibers. In another embodiment, the diffusion media in fuel cells may also be made of a gas-permeable cross-linked polymer, such as PDMS (polydimethylsiloxane), filled with porous graphite particles.

[0124] Several methods can be used to stack the active layers of a fuel cell. The first method is to stack the layers on top of each other, usually from the anode to the cathode, to form a complete stack of microcells. The second method is to manufacture the anode and cathode separately and then assemble them together, for example under a press. These two methods use similar layer deposition techniques, although the final assembly method differs.

[0125] A further subject of the present invention is an electrolytic cell comprising an ion-conducting membrane as defined above or obtained by the method described above.

[0126] Methods for preparing electrolytic cells are described in the prior art and can be applied by analogy.

[0127] An electrolyzer typically consists of a stack of two electrodes, optionally coated with a catalyst, between which an ion-conducting membrane is positioned.

[0128] Typically, the devices of the present invention, and more particularly the fuel cells, may be portable or stationary.

[0129] Advantageously, the device is biocompatible and comprises an ion-conducting membrane as defined above or obtained by the method described above.

[0130] The present invention is advantageous in that it allows for the preparation of ion-conducting membranes that are particularly suitable for use in fuel cells using methods that are simplified compared to the prior art.

[0131] Furthermore, the present invention makes it possible to significantly reduce the manufacturing costs of ion-conducting membranes, firstly by eliminating the need for expensive polymers such as Nafion®, and secondly by a manufacturing method that is simple to implement.

[0132] The membranes of the present invention also exhibit improved mechanical strength compared to prior art membranes.

[0133] Finally, the present invention is advantageous in that it makes available ion-conducting membranes with a range of flexibility depending on the polymer used to form the matrix. [Example]

[0134] Example 1 - Preparation of an anionic membrane of the present invention from zeolite Na-Y and polydimethylsiloxane polymer material - Zeolite Na-Y (CAS 1318-02-01), - ion exchange resins available from DuPont under the trade name Amberlite® H; - 3-(trimethoxysilyl)propyl-N,N,N-trimethylammonium- 15 N-chloride (TMSPA, CAS 35141-36-7), - polydimethylsiloxane polymer + curing agent, available in the form of a mixture from DOW CHEMICALS under the trade name Sylgard® 184; - Substrate in polytetrafluoroethylene (PTFE).

[0135] Preparation of anionic membranes First step: Conversion of zeolite Na-Y to zeolite YH Mix 300 mg of zeolite Na-Y powder with 5 mL of water. +is added to the solution. The mixture is left to react under stirring for 24 hours. Analysis by infrared spectroscopy confirms that zeolite YH has been obtained (free sodium Na + The cation is converted to hydrogen H + via substitution with ions).

[0136] Second step: Conversion of cation-conducting zeolite YH to anion-conducting material.

[0137] The TH zeolite powder was dried and mixed with 5 mL of TMSPA to convert the cation conduction to anion conduction. The mixture was left to react for 10 hours. The product was rinsed and dried. The conversion of the zeolite was confirmed by infrared spectroscopy.

[0138] Third step: membrane preparation The converted zeolite powder is then mixed with an equal mass of a mixture of polydimethylsiloxane polymer and curing agent. The resulting mixture is deposited on a PTFE substrate to form a 100 μm thick film, the thickness of which is controlled using adhesive strips of tape as a template. The film is then placed at 50°C for 24 hours to allow crosslinking of the polymer. The film is then peeled off the substrate and cut into 11 mm diameter disks using a die cutter.

[0139] Example 2 - Preparation of a cationic membrane of the present invention from an ion exchange resin and a polydimethylsiloxane polymer material - sodium, commercially available from DuPont under the trade name Amberlite® IRP69 + a strongly acidic cationic ion exchange resin in the form of - polydimethylsiloxane polymer + curing agent, available in the form of a mixture from DOW CHEMICALS under the trade name Sylgard® 184; - Polytetrafluoroethylene (PTFE) substrate.

[0140] Cationic membrane production 900 mg of ion exchange resin was mixed with 400 mg of a mixture of polydimethylsiloxane polymer and curing agent. The resulting mixture was deposited on a PTFE substrate to form a 100 μm-thick film, the thickness of which was controlled using adhesive strips of tape as a template. The film was then placed at 50°C for 24 hours to induce crosslinking of the polymer. The film was then peeled off from the substrate and placed in a water-saturated atmosphere for 12 hours to rehydrate. It was then cut into 11 mm-diameter disks using a die cutter.

[0141] Example 3 - Preparation of an electrolytic cell from a membrane of the invention and evaluation of the membrane's conductance The ionic conductivities of the membranes prepared in Examples 1 and 2 were evaluated in an electrolytic cell-type device.

[0142] Preparation of the electrolytic cell An electrolytic cell was prepared from each of the membranes. In particular, the electrolytic cells were prepared by stacking the following layers: - a carbon fabric electrode; a membrane to be evaluated; - Carbon fabric electrodes.

[0143] Evaluation of electrolytic cell performance The electrical conduction of the different electrolytic cells was evaluated by measuring the change in the intensity of the current measured at the terminals of the electrolytic cell as a function of the applied voltage.

[0144] The results obtained are shown in FIGS. [Brief explanation of the drawings]

[0145] [Figure 1] FIG. 1 is a curve showing the change in intensity measured at the terminals of an electrolytic cell incorporating the composite membrane prepared in Example 1 as a function of the applied voltage.

[0146] [Figure 2] FIG. 2 is a curve showing the change in intensity measured at the terminals of an electrolytic cell incorporating the composite membrane prepared in Example 2 or a Nafion® type membrane as a function of the applied voltage.

[0147] Curve 1 was obtained from an electrolytic cell incorporating the composite membrane prepared in Example 2.

[0148] Curve 2 (comparison) was obtained from an electrolyzer incorporating a Nafion® type membrane.

[0149] 1 shows that a non-zero current is measured at the terminals of an electrolytic cell incorporating the composite membrane (of the present invention) prepared in Example 1. Thus, the prepared electrolytic cell is electrically conductive, demonstrating the ability of the membrane (of the present invention) prepared in Example 1 to conduct ions through the membrane. Thus, the membrane prepared in Example 1 is ionically conductive.

[0150] 2, it can be seen that a non-zero current is measured at the terminals of the electrolytic cell incorporating the composite membrane (of the invention) prepared in Example 2. Thus, the electrolytic cell is electrically conductive, demonstrating the ability of the membrane prepared in Example 2 to conduct ions through the membrane. Thus, the membrane (of the invention) prepared in Example 2 is ionically conductive.

[0151] 2, the current measured at the terminals of an electrolytic cell incorporating the membrane prepared in Example 2 (curve 1) is significantly greater than the current measured at the terminals of an electrolytic cell incorporating a Nafion® membrane (curve 2). Thus, the membrane prepared in Example 2 (of the present invention) exhibits significantly higher ionic conductivity than Nafion® membranes.

[0152] Example 4 - Preparation of cells from membranes of the present invention The performance levels of the membranes prepared in Examples 1 and 2 were also evaluated in cells.

[0153] material The cell was prepared from the following materials: an electrode, commercially available from FuelCell Store under the reference W1S1011, consisting of a substrate of carbon fabric coated with a catalyst supported on Vulcan carbon (20%) and a surface coating of Nafion®; - a crosslinked polymer of polyacrylic acid sold under the reference Carbopol® 940.

[0154] Cell preparation The surface coating of the electrode was preliminarily modified to convert it into an anion-conducting material by applying the method described in WO 2021 / 083922(A1). Similarly, a cross-linked polymer of polyacrylic acid was modified according to the same method. These preliminaries ensure good ionic conduction between the membrane and the supported catalyst of the electrode.

[0155] Cells were then prepared from each of the membranes prepared above. Specifically, the cells were prepared by stacking the following layers: - an electrode modified according to the method described above; - a layer of a crosslinked polymer of polyacrylic acid modified according to the method described above; a membrane to be evaluated; - a layer of a crosslinked polymer of polyacrylic acid modified according to the method described above; - An electrode modified according to the method described above.

[0156] Cell evaluation OCV, voltage and power measurements were carried out on the different cells and the following results were obtained:

[0157] For the cell incorporating the membrane (of the invention) prepared in Example 1, the measured OCV is 700 mV.

[0158] For the cell incorporating the membrane (of the invention) prepared in Example 2, the measured OCV is 700 mV and the measured power density is 100 mW / cm 2 is.

Claims

1. 1. An ion-conducting membrane comprising a matrix of a cross-linked polymer and a powder of an ion-conducting material, said powder of ion-conducting material being dispersed in a continuous solid matrix and occupying 33% to 66% by volume of the total volume of said ion-conducting membrane.

2. 2. The membrane according to claim 1, wherein the continuous solid matrix is ​​obtained by crosslinking, in particular chemical or physical crosslinking, of a crosslinkable polymer chosen from among polysiloxanes, thermosetting resins, polyamides, polyesters, polyolefins, and mixtures thereof, preferably chosen from among polydimethylsiloxanes, epoxy resins, and mixtures thereof.

3. 3. The membrane according to claim 1 or 2, wherein said powder of ion-conducting material has a particle size of less than or equal to 20 μm, preferably in the range of 100 nm to 10 μm.

4. 4. The membrane according to any one of claims 1 to 3, wherein the ion-conducting material is selected from inorganic silicon-based materials, optionally functionalized organic materials such as ion exchange resins, or mixtures thereof.

5. 5. The membrane of claim 4, wherein the ion-conducting material is selected from the group consisting of silicates, optionally functionalized ion exchange resins, and mixtures thereof.

6. 6. The membrane of any one of claims 1 to 5, wherein the ion-conducting membrane is porous, preferably having a porosity in the range of 1% to 25%, more preferably in the range of 3% to 20%.

7. A method for preparing the ion-conducting membrane according to any one of claims 1 to 6, comprising the steps of: a) providing powders of (i) a crosslinkable polymer and (ii) an ionically conductive material; b) dispersing the powder in the crosslinkable polymer to form a homogeneous mixture in an amount of 33% to 66% by volume based on the total volume of the mixture; c) forming a film from the mixture obtained in b), in particular by depositing said mixture on the surface of a substrate; d) crosslinking said crosslinkable polymer.

8. 8. The method of claim 7, including a prior step of functionalizing the powder of ionically conductive material.

9. A fuel cell comprising a membrane according to any one of claims 1 to 6 or obtained by the method according to claim 7 or 8.

10. A biocompatible device comprising a membrane according to any one of claims 1 to 6 or a membrane obtained by the method according to claim 7 or 8.

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