Composition and sealing gasket for electrochemical system and manufacturing process

Abstract

Composition and Seal for Electrochemical System and Manufacturing Method. The invention relates to a fluid composition for forming a gas-tight seal for an electrochemical system, characterized in that it comprises a main mineral filler phase and an additional mineral filler phase, the additional mineral filler phase comprising a powdered mixture of vermiculite and steatite, the mixture representing up to 30% by weight of the total weight of the composition. The invention also relates to a seal for an electrochemical cell unit formed from the fluid composition comprising the main mineral filler and the additional mineral filler, as well as a fuel cell or fuel cell component comprising one or more seals according to the invention. Figure for the abstract: Fig. 1

Description

Title of the invention: Composition and sealing gasket for electrochemical system and manufacturing process. Technical field

[0001] The present invention relates to a sealing composition for an electrochemical system, a sealing gasket formed with said composition, and a method for manufacturing this sealing composition. The invention will find application in the field of electrochemical systems producing energy or hydrogen. More particularly, the invention is intended to ensure the sealing of so-called solid oxide electrochemical systems (or SOCs for "Solid Oxide Cells"), which include solid oxide fuel cells (or SOFCs for "Solid Oxide Fuel Cells") and high-temperature electrolyzers (or SOECs for "Solid Oxide Electrolyzer Cells"). STATE OF THE ART

[0002] A SOC electrochemical cell is schematically represented by 3 layers, i.e., 2 electrodes separated by an electrolyte. The electrodes are the site of the electrochemical reactions and are electronically conductive, or even mixed electronic / ionic, while the electrolyte is solely ionically conductive.

[0003] SOFC fuel cells are electrochemical cells that produce electrical and thermal energy and use the chemical energy generated by the reaction of water formation from hydrogen and oxygen.

[0004] The operating principle of a SOFC cell is based on the following mechanism: oxygen from the air, which is supplied to the cathode, is dissociated to give O2- anions. The anions thus formed migrate through the electrolyte until they reach the anode, where they oxidize the hydrogen atoms supplied by the fuel. This reaction releases electrons and water.

[0005] Cells operating as SOECs (Solid Oxide Electrolysis Cells) are hydrogen-producing electrochemical cells whose operating principle is strictly the reverse of that of SOFCs. In an SOEC, water vapor is supplied to the cathode, and the water molecules are dissociated into hydrogen and O2- anions. The anions thus formed diffuse through the electrolyte to recombine as oxygen at the anode, while the hydrogen remains, along with the water vapor, at the cathode. This hydrogen can then be recovered for use as fuel in other applications.

[0006] Hydrogen is thus produced with a high yield, making this technology very relevant in the current energy context. Indeed, the increasing use of renewable energies, often intermittent, requires an efficient means of storage, and the hydrogen carrier then becomes particularly relevant.

[0007] A key aspect of SOC devices is the sealing design that must be implemented during the assembly of such devices. Sealing is primarily achieved through the use of gaskets, which play a crucial role in ensuring the system's efficiency and durability. These gaskets must exhibit high gas tightness (leakage rate <103 mbar.l / s), thermochemical and thermomechanical compatibility with adjacent materials, and stability under operating conditions (650°C to 850°C) throughout the system's lifetime (>90,000 h), allowing for thermal cycling between the operating temperature and ambient temperature. They must also possess high electrical resistivity and a coefficient of thermal expansion compatible with the other materials.

[0008] In planar systems, electrochemical cells are generally connected in electrical series and separated by interconnectors, primarily metallic, for example, ferritic stainless steels for cost reasons. One of the major difficulties encountered in these high-temperature systems is ensuring a seal between the hydrogen and oxygen compartments at each stage of these stacks, for each cell. In most geometries, the sealing zones are located between the electrochemical cell, more precisely between the dense electrolyte made of yttrium-doped zirconia, which is conventionally used in these cells, and the interconnector.

[0009] Two solutions very frequently used in this type of system are compression seals, of the mica type, and glass or glass-ceramics.

[0010] Deformable mica-type compression seals require the application of a compressive force to achieve a good level of sealing. This force is often high (>40 MPa) and may be incompatible with the materials used (fragile electrochemical cells, thin interconnectors, etc.) to avoid damaging them. The use of these solutions often results in a rather weak and insufficient seal.

[0011] Glasses and glass-ceramics are also very widely used in these high-temperature technologies. Due to the high operating temperature, sealing glasses are subjected to temperatures well above their Tg (glass transition temperature) for the entire operating period of the SOCs. Above the glass transition temperature, the characteristics of a viscous glass often result in high permeability and solubility for the gaseous species, and also increased reactivities with the metallic and ceramic components of the stack.

[0012] Conventional glass-ceramics used in SOC systems have certain disadvantages, sometimes being imperfect in guaranteeing good sealing of the system.

[0013] Furthermore, during their shaping, glasses or glass-ceramics use significant quantities of organic materials to form a slip. These organic materials, during the initial heating, must be released as a gas (often CO2), and generate bubbles or defects that hinder the achievement of a good seal.

[0014] There is therefore a need to propose a solution that resolves all or part of the aforementioned drawbacks for these sealing compositions. SUMMARY

[0015] To achieve this objective, according to one embodiment, a fluid composition is provided for the formation of a gas-tight seal of an electrochemical system characterized in that it comprises a main mineral filler phase and an additional mineral filler phase, the additional mineral filler phase comprising a mixture in powder form of vermiculite and steatite, the mixture representing up to 30% by weight of the total weight of the composition.

[0016] By proposing a glass-ceramic gasket into which mineral filler flakes are introduced, the invention provides an optimized gasket solution. The addition of this mixture allows the formation of a composite with the main mineral filler phase, such as glass or glass-ceramic, which improves pressure resistance. Indeed, the additional mineral filler is advantageously in the form of flakes, making it possible to multiply the number of local interfaces and thus prevent any movement of the main mineral filler. The presence of the additional mineral filler phase notably limits gas formation during the initial temperature rise and improves the sealing of the resulting gasket.

[0017] According to another aspect, the invention relates to a sealing gasket for an electrochemical cell unit formed from the fluid composition as described above comprising the main mineral charge and the additional mineral charge.

[0018] According to another aspect, the invention relates to a fuel cell or fuel cell component comprising one or more seals as described above.

[0019] According to another aspect, the invention relates to a method for manufacturing a composition such as the one described above comprising - a step of preparing a main mineral filler phase comprising the addition of a main mineral filler in at least one solvent, - a preparation step for the mixture of the additional mineral filler phase, including the reduction of vermiculite and steatite to powder form, - an assembly step of the additional mineral filler phase to the main mineral filler phase, the additional mineral filler phase representing up to 10% by weight of the total weight of the composition.

[0020] According to another aspect, the invention relates to a method for manufacturing a sealing gasket comprising - an application of the fluid composition as described above to a first surface, then advantageously, - the application of a second surface onto the fluid composition, then - a heat treatment of the first surface, of the fluid composition and of the second surface at a temperature greater than or equal to 700°C.

[0021] According to another aspect, the invention relates to the use of a fluid composition as described above as a gas seal for a fuel cell or fuel cell component, preferably a solid oxide. BRIEF DESCRIPTION OF THE FIGURES

[0022] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:

[0023] [Fig.1] Fig.1 represents a schematic diagram of sealing zones present in high-temperature electrochemical systems of planar technology comprising electrochemical cells.

[0024] [Fig.2] Fig.2 represents a SEM cross-sectional view of a sealing joint according to the invention on an electrochemical half-cell comprising a hydrogen electrode and an electrolyte.

[0025] [Fig.3] Fig.3 represents a diagram of the leak measurement setup.

[0026] [Fig. 4A] Figures 4A and 4B represent the comparison of leakage rates of a reference seal ([Fig.4A]) and the seal according to the invention ([Fig.4B]) at 700°C for different overpressures.

[0027] [Fig.4B]

[0028] [Fig. 5A] Figures 5A and 5B represent the comparison of leakage rates of a reference seal ([Fig.5A]) and the seal according to the invention ([Fig.5B]) at 800°C for different overpressures.

[0029] [Fig.5B]

[0030] The drawings are given as examples and are not limiting of the invention. They are schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. DETAILED DESCRIPTION

[0031] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:

[0032] According to one example, the composition being in the form of a paste or slip;

[0033] According to one example, the main mineral loading phase comprises a load main mineral chosen from at least one glass-ceramic and / or silica powder;

[0034] According to one example, the additional mineral filler phase of the mixture represents 1 to 10% by weight of the total weight of the composition;

[0035] According to one example, the composition comprising 5% of additional mineral filler phase, preferably of the mixture in powder form comprising vermiculite and steatite, and 95% of main mineral filler phase.

[0036] According to one example, the main mineral filler phase comprises 60 to 80% preferably 78.0% of main mineral filler by weight of the total weight of the main mineral filler phase;

[0037] According to one example, the main mineral loading phase comprises a solvent;

[0038] According to one example, the solvent is chosen from methyl ethyl ketone-ethanol (mek-EtOH), toluene, or water;

[0039] According to one example, the main mineral filler phase includes a dispersant and / or a plasticizer and / or a binder;

[0040] According to one example, the dispersant is chosen from a phosphoric ester such as Beycostat CP213;

[0041] According to one example, the binder is chosen from either vinyl polybutyral (PVB) or ethyl cellulose;

[0042] According to one example, the plasticizer is chosen from PolyEthylenGlycol (PEG);

[0043] According to one example, the main mineral loading phase comprises - 60 to 85% main mineral content - 13 to 40% solvent, - 1 to 3% binder, - 21 to 3% plasticizer, - 0 to 1% dispersant. the percentages being in weight of the total weight of the main mineral loading phase.

[0044] According to one example, the mixture comprises at least 25% vermiculite and at least 15% steatite by weight of the total weight of the mixture;

[0045] A parameter "approximately equal to / greater than / less than" or "of the order of" a given value means that this parameter is equal to / greater than / less than the given value, to within 10% or even 5% of that value.

[0046] Vertical means that which is directed along the thickness of the stack or substrate, that is to say along the principal direction of extension of the stack or substrate, and horizontal means that which is perpendicular to the vertical. The top and bottom being vertically opposite.

[0047] A transverse direction is understood to be a direction perpendicular to a longitudinal direction. The longitudinal direction is understood to be the thickness of the stack or substrate. A transverse section is a section perpendicular to the longitudinal axis. A transverse section is a section perpendicular to the thickness of the substrate stack.

[0048] For the purposes of this disclosure, the expression "A and / or B" means (A), (B) or (A and B). For the purposes of this disclosure, the expression "A, B and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0049] The terms "first", "second" and "third", "additional", etc. are used simply as labels, and are not intended to impose numerical requirements on their objects.

[0050] The term "upper," used in particular to describe a face of a layer, here serves only to designate one of the two faces of a layer (the other being the lower face), without making any assumptions about the relative position of the faces along a vertical direction. The upper face could thus also have been called the front face, as opposed to a back face.

[0051] The shapes or dimensions given for certain components of the present invention are always only indicative and are understood to include substantially equivalent shapes and dimensions.

[0052] It is specified that within the framework of the present invention, the term "on", "over", "covers", "above", "underlying", "below", "facing", or their equivalents do not necessarily mean "in contact with". For example, the deposition of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but it means that the first layer at least partially covers the second layer either by being directly in contact with it, or by being separated from it by at least one other layer or at least one other element.

[0053] The invention relates to a fluid composition intended for the formation of a sealing seal 1 of an electrochemical system, in particular of an electrochemical cell unit, or of a stack of electrochemical cell units such as fuel cells or fuel cell components comprising one or more seals.

[0054] In the invention, the fuel cells can be of any suitable type, but are generally solid oxide fuel cells.

[0055] The sealing of the fuel cell can be effected between the cells 4 of a stack, i.e. between cell 4 and an interconnector 2 or between the interconnectors 2, or between the cells 4 and an end plate or between an interconnector 2 and other contact surfaces 8 as added elements to ensure electrical insulation between interconnectors 2.

[0056] The composition according to the invention is fluid. By fluid, it is understood that the composition can flow freely.

[0057] Preferably, the composition is in the form of a paste or a slip. Paste is understood to be a soft, advantageously malleable substance. Slip is understood to be a paste diluted in a solvent. Slip is understood to be a suspension or slurry.

[0058] According to the invention, the composition comprises a main mineral filler phase and an additional mineral filler phase.

[0059] The main mineral filler phase advantageously comprises a main mineral filler selected from at least one glass-ceramic and / or at least one silica powder. By way of example, the main mineral filler is glass, preferably of the Schott G018-311 type. This glass has characteristics perfectly suited in terms of coefficient of thermal expansion / chemical compatibility to a SOFC / SOEC electrochemical cell.

[0060] According to one possibility, the main mineral filler phase comprises a solvent. By way of example, the solvent is chosen from at least one of methyl ethyl ketone-ethanol (mek-EtOH), toluene, or water.

[0061] The main mineral filler represents from 50% to 85%, preferably 78% by weight of the total weight of the main mineral filler phase.

[0062] The additional mineral loading phase advantageously comprises a mixture of vermiculite and steatite.

[0063] Vermiculite is a natural mineral belonging to the phyllosilicate family with the chemical formula (Mg,Ca)0.7(Mg,Fe,Al)6(Al,Si)8O22(OH)4-8H2O, formed by the hydration of certain basaltic minerals. It exhibits expansion properties under the effect of heat (exfoliation). Vermiculite is a hydrated phyllosilicate mineral generally considered to be an altered mica. The term vermiculite also extends to minerals Related minerals believed to have formed in the same or a similar way and commonly referred to as vermiculite, such as hydrobiotite, are also known as exfoliated vermiculite. Exfoliated vermiculite is formed by chemically treating vermiculite ore and swelling it in water. In one possible preparation method, the ore is treated with a saturated sodium chloride solution to exchange magnesium ions for sodium ions, and then with n-butylammonium chloride to replace the sodium ions with n-butylammonium ions. Alternatively, the ore can be treated with a saturated lithium citrate solution in a single step. During washing of the treated ore with water, swelling occurs. The swollen material is then subjected to high shear to produce an aqueous suspension of very fine vermiculite particles (diameter less than 50 µm).Other chemical treatment agents are known to those skilled in the art. Water can be removed from the suspension to form dry particles of exfoliated vermiculite.

[0064] Steatite is a very dense volcanic rock. It contains talc, magnesite and chlorite.

[0065] The mixture advantageously comprises at least 25% vermiculite and at least 15% steatite by weight of the total weight of the mixture.

[0066] The mixture preferably comprises 25 to 85%, more preferably 30 to 70%, and even more preferably 40 to 60% of vermiculite.

[0067] The mixture preferably comprises at least 30%, more preferably at least 35%, more preferably at least 40% of vermiculite.

[0068] The mixture preferably comprises 15 to 75%, more preferably 30 to 70%, and preferably still 40 to 60% of steatite.

[0069] The mixture preferably comprises at least 30% steatite, more preferably at least 40%.

[0070] The mixture is in powder form. The vermiculite and steatite are reduced to a powder. The powder comprises sheets and platelets of varying sizes ranging from approximately 1 µm to approximately 150 µm.

[0071] As a preferred example, the mixture is thermiculite ® from Flexitallic, more specifically thermiculite ® 866. The thermiculite ® 866 is reduced to powder to form the mixture according to the invention.

[0072] The additional mineral filler phase, that is to say preferably, the mixture is present in the composition according to the invention in a range between 1 and 30% preferably from 1 to 10% and for example 5% by weight of the total weight of the composition.

[0073] The composition advantageously consists of the main mineral filler phase and the additional mineral filler phase.

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081] In this case, the composition comprises an amount less than or equal to 30%, preferably from 1 to 10%, preferably 5%, of additional mineral filler phase, by weight of the total weight of the composition. In this case, the composition comprises the remaining main mineral filler phase. In one scenario, the composition includes a binder; more specifically, the main mineral filler phase includes at least one binder. For example, the binder is chosen from at least one of the following: polyvinyl butyral (PVB) or ethyl cellulose. In one scenario, the composition includes a plasticizer; more specifically, the main mineral filler phase includes at least one plasticizer. For example, the plasticizer is chosen from at least one of the following: Polyethylene Glycol (PEG). According to one possibility, the composition includes a dispersant; more precisely, the main mineral filler phase includes at least one dispersant. For example, the dispersant is chosen from at least one of the following: the phosphoric ester of Beycostat CP213 (CAS No. 152742-51-3), cetyltrimethylammonium bromide (CTAB (Ci6H33)N(CH3)3), or dibutyl sebacate. According to one embodiment, the main mineral loading phase comprises: - 60 to 85%, preferably 78.1%, of principal mineral content - 13 to 40%, preferably 16.9% solvent - 1 to 3%, preferably 2.2% binder, - 1 to 3%, preferably 2.2% plasticizer - 0 to 1%, preferably 0.6% dispersant, - the percentages are understood to be expressed as a percentage of the total weight of the mineral phase main. According to one embodiment, the main mineral loading phase comprises: - 78.1 g of main mineral filler - 16.9 g of solvent - 2.2g of binder - 2.2g of plasticizer - 0.6g of dispersant. According to one aspect, the invention relates to a gas-tight seal 1, for example formed on an electrochemical cell. The sealing gasket 1 is formed from the composition as described above and advantageously comprises the main mineral filler and the additional mineral filler. The sealing gasket 1 is advantageously formed from the fluid composition having undergone treatment, advantageously thermal treatment. intended to solidify seal 1. Seal 1 advantageously does not include the solvent. Seal 1 is advantageously more gas-tight than the composition.

[0082] According to one possibility, the gas tightness of a seal according to the invention is measured by measuring a leakage rate at temperature under pressure.

[0083] Preferably, the sealing gasket exhibits no leakage rate up to 500 mbar (50,000 pascal) of overpressure at 700°C.

[0084] Preferably, the sealing gasket exhibits no leakage rate up to 800 mbar (i.e., 80,000 pascals) of overpressure at 800°C.

[0085] Preferably, the sealing gasket has a leakage rate of less than 10⁴ mbar.l / s (i.e. 1000 pascal.l / s) at 1000 mbar d(100,000 pascal) of overpressure at 800°C.

[0086] According to one aspect, the invention relates to a method for manufacturing the composition as described above comprising a step of preparing the main mineral filler phase, a step of preparing the additional mineral filler phase and a step of mixing the main mineral filler phase and the additional mineral filler phase.

[0087] According to one embodiment, the preparation step of the main mineral filler phase comprises mixing a main mineral filler in a solvent, advantageously in the presence of a dispersant. Preferably, homogenization is carried out, for example by a planetary mixer. A binder and / or a plasticizer, possibly diluted in a solvent, are added. Preferably, homogenization is carried out again, for example by a planetary mixer.

[0088] According to one embodiment, the preparation step for the additional mineral filler phase includes grinding the vermiculite and the steatite or thermiculite® if the latter is used. Grinding is carried out, for example, by manual grinding with a mortar and pestle or any conventional grinding system (planetary mill, attrition mill, etc.).

[0089] According to one embodiment, the mixing step of the main mineral filler phase and the additional mineral filler phase includes adding the powder of the additional mineral filler phase obtained in the preparation step to the main mineral filler phase. Preferably, 5%, by weight of the total weight of the composition, of the additional mineral filler phase is added to the main mineral filler phase, which represents approximately 95%.

[0090] According to one aspect, the invention relates to a method for forming a sealing joint 1.

[0091] The process includes a step of depositing the fluid composition. The composition obtained as described above is applied to an electrochemical cell 2 or a half-electrochemical cell 10, for example, onto the solid electrolyte so as to ensure an interface between the solid electrolyte and a metallic interconnector 2. The composition is deposited in a fluid state. This fluid deposition allows the composition to conform to the roughness of the facing surfaces and thus form a better quality interface.

[0092] The process then preferably includes a heat treatment step, preferably, a heat treatment at a temperature greater than or equal to 700°C is applied.

[0093] By way of example, a heat treatment at 860°C for one hour in an air furnace with temperature ramps of 100°C / h is carried out on the composition and the surfaces between which it is arranged.

[0094] During testing, it was observed that the interface between the composition and a half-cell is of good quality, without any apparent defects. Platelets that can serve as attachment points and as germination / growth sites for the glass-ceramic are observed to develop within the composition.

[0095] Figure 1 illustrates an electrochemical cell 1 surrounded by an interconnector 2 on each of its faces, with an electrical contact layer 8 placed on both faces of the cell. The gas channels 3 for supplying the cell are also shown. The joint 1 is formed, for example, between the two interconnectors, and between the interconnector 2 and the electrochemical cell 4.

[0096] Example 1: Preparation of a main mineral phase.

[0097] The main mineral filler phase is prepared as a glass-ceramic paste using the following process: mixing 0.62 g of dispersant and 3.65 g of solvent (MEK-ethanol type), and adding 78 g of the main mineral filler (for example, G018-311 glass-ceramic marketed by Schott). The mixture is then homogenized using a planetary mixer. Next, 2.16 g of binder (PVB type) and 2.16 g of plasticizer, dissolved in 13.24 g of solvent (50%-50% MEK-ethanol type), are added to this mixture. The mixture is then homogenized using a planetary mixer.

[0098] Example 2: Preparation of the additional mineral phase mixture

[0099] To prepare this mixture, Thermicullite® 866 plates (marketed by Flexitallic) are used. This material is a mixture of exfoliated vermiculite and steatite. These plates were ground into a powder by manual grinding for 15 minutes using a mortar and pestle until a relatively fine and homogeneous powder was obtained. SEM observation shows that the additional mineral filler 9, and more particularly the ground vermiculite / steatite mixture, takes the form of sheets or platelets of considerably variable sizes, ranging from a few microns to about one hundred microns.

[0100] Example 3: obtaining the composition according to the invention

[0101] 5% by mass of the powder prepared in Example 2 is added to the paste phase of main mineral charge prepared in example 1. The mixture is then made until a homogeneous mixture is obtained.

[0102] The composition obtained is usable for the formation of a sealing joint 1 of an electrochemical cell.

[0103] Example 4: Comparative sealing measurements between a reference seal and the invention

[0104] Leak tests were conducted to validate the benefit obtained from the invention. A temperature-under-pressure leakage rate measurement test was used. The setup shown schematically in [Fig. 3] allows testing of a composition obtained according to Example 3. The composition is formed into a bead approximately 3 mm in diameter between two metal interconnectors 2 separated by a spacer 5 with a thickness of 180 µm. The composition is heat-treated as described above to form the seal 1. A load 6 of approximately 4 kg is positioned on the setup to ensure contact between the interconnectors 2 and the spacers 5. Overpressure is provided by a central gas supply pipe 8, equipped with a pressure sensor.

[0105] When the desired overpressure is reached (under air in these tests), the pressure drop is measured as a function of time, which makes it possible to obtain a leakage rate of the composition studied.

[0106] In the same assembly, shown in [Fig.3], a reference seal formed by a Schott® G018-311 glass, and a seal 1 according to the invention obtained with the composition according to example 3 were tested, at 700°C and 800°C up to an overpressure of 1 bar.

[0107] At 700°C ([Fig.4A]), the leakage rate of the reference seal increases with overpressure, up to 8.10 4 mbar.l / s (i.e. 800 pascal.l / s) at 300 mbar (i.e. 30,000 pascal) of overpressure; for the seal 1 according to the invention ([Fig.4B]), no leakage rate was measurable, up to 500 mbar (i.e. 50,000 pascal) of overpressure (no change in pressure over a time greater than 10 minutes, measured with an accuracy of 0.1 mbar (i.e. 10 pascal).

[0108] At 800°C, ([Fig. 5A]) the leakage rate of the reference seal reaches 5 x 10⁴ mbar.l / s (i.e., 500 pascal.l / s) at 500 mbar (i.e., 50,000 pascal) of overpressure. The seal 1 according to the invention ([Fig. 5B]) exhibits no measurable leakage rate up to 800 mbar (i.e., 80,000 pascal) of overpressure, and a leakage rate of less than 10⁴ mbar.l / s (i.e., 1000 pascal.l / s) at 1000 mbar (i.e., 1000 pascal) of overpressure.

[0109] The tests carried out show a real gain of the seal 1 according to the invention compared to a reference seal.

[0110] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention. [YES] List of references 1. 2. 3. 4. 5. 6. Gas Channel Interconnector Joint Electrochemical Cell Wedge Charge 7. 8. 9. 10. Gas Supply and Measurement Electrical Contact Layer Additional Mineral Charge Electrochemical Half-Cell

Claims

Demands

1. Fluid composition intended for the formation of a gas-tight seal of an electrochemical system characterized in that it comprises a main mineral filler phase and an additional mineral filler phase, the additional mineral filler phase comprising a mixture in powder form of vermiculite and steatite, the mixture representing up to 30% by weight of the total weight of the composition.

2. Composition according to the preceding claim being in the form of a paste or slip.

3. Composition according to any one of the preceding claims wherein the main mineral filler phase comprises a main mineral filler selected from at least one glass-ceramic and / or silica powder.

4. Composition according to any one of the preceding claims wherein the additional mineral filler phase consists of the mixture and represents from 1 to 10% by weight of the total weight of the composition.

5. Composition according to any one of the preceding claims comprising 5% additional mineral filler phase, preferably of the mixture in powder form comprising vermiculite and steatite, 95% main mineral filler phase.

6. Composition according to any one of the preceding claims wherein the main mineral filler phase comprises from 60 to 80%, preferably 78%, of main mineral filler by weight of the total weight of the main mineral filler phase.

7. Composition according to any one of the preceding claims wherein the main mineral filler phase comprises a solvent.

8. Composition according to the preceding claim wherein the solvent is selected from methyl ethyl ketone-ethanol (mek-EtOH), toluene, or water.

9. Composition according to any one of the preceding claims wherein the main mineral filler phase comprises a dispersant and / or a plasticizer and / or a binder.

10. Composition according to the preceding claim wherein the dispersant is selected from a phosphoric ester such as Beycostat CP213

11. Composition according to any one of the two preceding claims wherein the binder is selected from polyvinyl butyral (PVB) or ethyl cellulose.

12. Composition according to any one of the three preceding claims wherein the plasticizer is selected from PolyEthylenGlycol (PEG).

13. A composition according to any one of the preceding claims, wherein the main mineral filler phase comprises: - 60 to 85% main mineral filler, - 13 to 40% solvent, - 1 to 3% binder, - 21 to 3% plasticizer, - 0 to 1% dispersant. The percentages are expressed by weight of the total weight of the main mineral filler phase.

14. Composition according to any one of the preceding claims wherein the mixture comprises at least 25% vermiculite and at least 15% steatite by weight of the total weight of the mixture.

15. Sealing gasket for electrochemical cell unit formed from the fluid composition according to any one of the preceding claims comprising the main mineral filler and the additional mineral filler.

16. Fuel cell or fuel cell component comprising one or more seals according to the preceding claim.

17. A method for manufacturing a composition according to any one of claims 1 to 14 comprising a step of preparing a main mineral filler phase including the addition of a main mineral filler to at least one solvent, a step of preparing the mixture of the additional mineral filler phase including the reduction of vermiculite and steatite to powder form, a step of combining the additional mineral filler phase with the main mineral filler phase, the mineral filler phase additional representing up to 10% by weight of the total weight of the composition.

18. Method of manufacturing a sealing gasket comprising - applying the fluid composition according to any one of claims 1 to 14 onto a first surface, - applying a second surface onto the fluid composition, - heat treating the first surface, the fluid composition and the second surface at a temperature greater than or equal to 700°C.

19. Use of a fluid composition according to any one of claims 1 to 14 as a gas seal for a fuel cell or fuel cell component.

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