Composition and sealing gasket for electrochemical system and manufacturing method

Abstract

The invention relates to a fluid composition intended for forming a gas-tight sealing gasket of a solid oxide electrochemical system, characterised in that it comprises a main mineral filler phase and an additional mineral filler phase, the additional mineral filler phase comprising a mixture in the form of vermiculite and steatite powder, the mixture representing up to 30% by weight of the total weight of the composition. The invention also relates to a sealing gasket for an electrochemical cell unit, the sealing gasket being formed from the fluid composition comprising the main mineral filler and the additional mineral filler, and to a fuel cell or fuel cell component comprising one or more gaskets according to the invention.

Description

[0001] "Composition and sealing gasket for electrochemical system and manufacturing process"

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to a sealing composition for electrochemical systems, 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").

[0004] STATE OF THE ART

[0005] 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.

[0006] SOFC fuel cells are electrochemical cells that produce electrical and thermal energy using the chemical energy generated by the reaction of water formation from hydrogen and oxygen.

[0007] The operating principle of a SOFC cell is based on the following mechanism: oxygen from the air, supplied to the cathode, is dissociated to produce O2- anions. These anions migrate through the electrolyte to the anode, where they oxidize the hydrogen atoms supplied by the fuel. This reaction releases electrons and water.

[0008] Solid oxide electrolysis cells (SOECs) are hydrogen-producing electrochemical cells whose operating principle is the exact opposite of that of solid oxide fuel cells (SOFCs). In an SOEC, water vapor is supplied to the cathode, and the water molecules are dissociated into hydrogen and oxygen (O2-) anions. The anions thus formed diffuse through the electrolyte to recombine as oxygen at the anode, while the hydrogen, along with the water vapor, remains at the cathode. This hydrogen can then be recovered for use as fuel in other applications.

[0009] Hydrogen is thus produced with a high yield, making this technology highly relevant in the current energy context. Indeed, the increasing use of renewable energies, often intermittent, requires an efficient storage method, and hydrogen as a carrier then becomes particularly relevant.

[0010] A key aspect of SOC devices is the sealing design that must be implemented during their assembly. 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 <10 -3mbar.l / s), thermochemical and thermomechanical compatibility with adjacent materials, as well as stability under operating conditions (650°C to 850°C) during the system lifetime (>90000h) which allows thermal cycling between operating temperature and ambient temperature, high electrical resistivity and a coefficient of thermal expansion compatible with other materials.

[0011] In planar systems, electrochemical cells are generally connected in series and separated by interconnectors, primarily metallic, for example, ferritic stainless steels for cost reasons. One of the major challenges 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 yttrium-doped zirconia electrolyte typically used in these cells, and the interconnector.

[0012] Two solutions very frequently used in this type of system are compression seals, such as mica, and glass or glass-ceramics.

[0013] Deformable mica 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.

[0014] Glasses and glass-ceramics are also widely used in these high-temperature technologies. Due to the high operating temperature, sealing glasses are subjected to temperatures well above their glass transition temperature (Tg) throughout the SOC's operating life. Above the glass transition temperature, the characteristics of a viscous glass often result in high permeability and solubility for gaseous species, as well as increased reactivity with the metallic and ceramic components of the stack.

[0015] Conventional glass-ceramics used in SOC systems have certain disadvantages, sometimes being imperfect in guaranteeing good sealing of the system.

[0016] Furthermore, the manufacturing process for glass or glass-ceramics uses significant quantities of organic materials to form a slip. During the initial heating, these organic materials must be released as gas (often CO2), generating bubbles or defects that compromise the achievement of a good seal.

[0017] Hybrid multi-layer seals are known, as described in documents KR20160077520, XP028760243 - RAUTANEN MET AL: "Glass coated compressible solid oxide fuel cell seals", JOURNAL OF POWER SOURCES, vol. 247, August 31, 2013 (2013-08-31), pages 243-248, XP029104384, THOMANN O ET AL: "Postexperimental analysis of a solid oxide fuel cell stack using hybrid seals", JOURNAL OF POWER SOURCES, vol. 274, October 23, pages 1009-1015. These seals do not provide complete satisfaction in terms of sealing, pressure resistance, or resistance to initial temperature rise. Therefore, there is a need to propose a solution that resolves all or some of the aforementioned drawbacks of these sealing compositions. SUMMARY OF THE INVENTION

[0018] To achieve this objective, according to one embodiment, a fluid composition is provided for the formation of a gas-tight seal in a solid oxide electrochemical system, characterized in that it comprises a main mineral filler phase and an additional mineral filler phase. The additional mineral filler phase comprises a mixture of vermiculite and steatite in powder form, the mixture representing up to 30%, preferably from 1% to 30%, by weight of the total weight of the composition. As an example, the main mineral filler phase comprises a main mineral filler selected from at least one glass-ceramic and / or a silica powder.

[0019] The invention, by proposing a glass-ceramic gasket into which mineral filler flakes are introduced, provides an optimized sealing 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, increasing the number of local interfaces and thus preventing 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.

[0020] 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.

[0021] According to another aspect, the invention relates to a fuel cell or fuel cell component comprising one or more seals as described above.

[0022] According to another aspect, the invention relates to a process for manufacturing a composition as described above comprising a step of preparing a main mineral filler phase including the addition of a main mineral filler in at least one solvent, a step of preparing the mixture of the additional mineral filler phase including the reduction to powder form of vermiculite and steatite, a step of assembling 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.

[0023] According to another aspect, the invention relates to a method for manufacturing a sealing gasket comprising applying the fluid composition as described above to a first surface, then advantageously applying a second surface to the fluid composition, then heat treating the first surface, the fluid composition and the second surface at a temperature greater than or equal to 700°C.

[0024] 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.

[0025] BRIEF DESCRIPTION OF THE FIGURES OF THE INVENTION

[0026] 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:

[0027] Figure 1 represents a schematic diagram of sealing zones present in high-temperature planar technology electrochemical systems comprising electrochemical cells.

[0028] Figure 2 shows a SEM cross-sectional view of a sealing gasket according to the invention on an electrochemical half-cell comprising a hydrogen electrode and an electrolyte.

[0029] Figure 3 shows a diagram of the leak measurement setup.

[0030] Figures 4A and 4B represent the comparison of leakage rates of a reference seal (Figure 4A) and the seal according to the invention (Figure 4B) at 700°C for different overpressures.

[0031] Figures 5A and 5B represent the comparison of leakage rates of a reference seal (Figure 5A) and the seal according to the invention (Figure 5B) at 800°C for different overpressures.

[0032] The drawings are given as examples and are not limiting to the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications.

[0033] DETAILED DESCRIPTION OF THE INVENTION

[0034] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:

[0035] According to one example, the composition being in the form of a paste or slip;

[0036] 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;

[0037] According to one example, the composition includes 5% additional mineral filler phase, preferably a powder mixture comprising vermiculite and steatite, and 95% main mineral filler phase.

[0038] According to one example, the main mineral loading phase comprises 60 to 80% preferably 78.0% main mineral loading by weight of the total weight of the main mineral loading phase;

[0039] According to one example, the main mineral loading phase includes a solvent;

[0040] In one example, the solvent is chosen from methyl ethyl ketone-ethanol (mek-EtOH), toluene, or water;

[0041] According to one example, the main mineral filler phase includes a dispersant and / or a plasticizer and / or a binder;

[0042] According to one example, the dispersant is chosen from a phosphoric ester such as Beycostat CP213;

[0043] In one example, the binder is chosen from either vinyl polybutyral (PVB) or ethyl cellulose;

[0044] According to one example, the plasticizer is chosen from PolyEthylenGlycol (PEG);

[0045] According to one example, the main mineral loading phase includes

[0046] - 60 to 85% main mineral content

[0047] 13 to 40% solvent,

[0048] 1 to 3% binder,

[0049] - 21 to 3% plasticizer,

[0050] 0 to 1% dispersant.

[0051] The percentages are in weight of the total weight of the main mineral loading phase.

[0052] 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;

[0053] 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.

[0054] Vertical refers to what is directed along the thickness of the stack or substrate, that is, along the principal direction of extension of the stack or substrate, and horizontal refers to what is perpendicular to the vertical. The top and bottom are vertically opposite.

[0055] A transverse section is defined as a direction perpendicular to a longitudinal direction. The longitudinal direction refers to the thickness of the stack or substrate. A cross-section is a cut perpendicular to the longitudinal axis. A cross-section is a cut perpendicular to the thickness of the substrate stack.

[0056] For the purposes of this disclosure, "A and / or B" means (A), (B), or (A and B). For the purposes of this disclosure, "A, B, and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0057] The terms "first", "second" and "third", "additional", etc. are used simply as labels, and are not intended to impose numerical requirements on their objects.

[0058] The term "upper," used specifically to describe a face of a layer, here only designates 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, in contrast to a back face.

[0059] 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.

[0060] It is specified that, within the context of the present invention, the terms "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 does mean 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 element.

[0061] 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.

[0062] In the invention, the fuel cells can be of any suitable type, but are generally solid oxide fuel cells.

[0063] The fuel cell can be sealed between the cells 4 of a stack, that is, 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 such as elements added to ensure electrical insulation between interconnectors 2. The composition according to the invention is fluid. A fluid is understood to mean that the composition can flow freely.

[0064] Preferably, the composition is in the form of a paste or a slip. A paste is understood to be a soft, advantageously malleable substance. A slip is understood to be a paste diluted in a solvent. Slip is understood as a suspension or slurry.

[0065] According to the invention, the composition comprises a main mineral filler phase and an additional mineral filler phase.

[0066] The main mineral loading phase advantageously comprises a main mineral loading selected from at least one glass-ceramic and / or at least one silica powder. For example, the main mineral loading is glass, preferably Schott G018-311 glass. This glass has characteristics perfectly suited in terms of coefficient of thermal expansion and chemical compatibility to a SOFC / SOEC electrochemical cell.

[0067] In one scenario, the main mineral loading phase includes a solvent. For example, the solvent is chosen from at least one of the following: methyl ethyl ketone-ethanol (MEK-EtOH), toluene, or water.

[0068] The main mineral filler represents 50% to 85%, preferably 78% by weight of the total weight of the main mineral filler phase.

[0069] The additional mineral loading phase advantageously comprises a mixture of vermiculite and steatite.

[0070] Vermiculite is a naturally occurring mineral belonging to the phyllosilicate family, with the chemical formula (Mg,Ca)0.7(Mg,Fe,Al)6(Al,Si)8O22(OH)4 8H2O. It is formed by the hydration of certain basaltic minerals. It exhibits expansion properties under the influence of heat (exfoliation). Vermiculite is a hydrated phyllosilicate mineral generally considered to be an altered mica. The term vermiculite also extends to related minerals believed to have been formed in the same or a similar way and commonly called vermiculite, such as hydrobiotite. The term vermiculite also refers to 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. Upon washing 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. The water can be removed from the suspension to form dry, exfoliated vermiculite particles.

[0071] Steatite is a very dense volcanic rock. It contains talc, magnesite, and chlorite.

[0072] The mixture advantageously comprises at least 25% vermiculite and at least 15% steatite by weight of the total weight of the mixture.

[0073] The mixture preferably comprises 25 to 85%, more preferably 30 to 70%, and preferably 40 to 60% vermiculite.

[0074] The mixture preferably comprises at least 30%, more preferably at least 35%, more preferably at least 40% of vermiculite.

[0075] The mixture preferably comprises 15 to 75%, more preferably 30 to 70%, and preferably still 40 to 60% steatite.

[0076] The mixture preferably comprises at least 30% steatite, more preferably at least 40%.

[0077] The mixture is in powder form. Vermiculite and steatite are ground into a powder. The powder comprises sheets and platelets of varying sizes, ranging from approximately 10 µm to approximately 150 µm.

[0078] 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.

[0079] 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.

[0080] The composition advantageously consists of the main mineral filler phase and the additional mineral filler phase.

[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.

[0082] 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 selected from at least one of the following: polyvinyl butyral (PVB) or ethyl cellulose. In another scenario, the composition includes a plasticizer; more specifically, the main mineral filler phase includes at least one plasticizer. For example, the plasticizer is selected from at least one of the following: polyethylene glycol (PEG).

[0083] 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: Beycostat CP213 phosphoric ester (CAS No. 152742-51-3), cetyltrimethylammonium bromide (CTAB (CieH33)N(CH3)3), or dibutyl sebacate.

[0084] According to one embodiment, the main mineral loading phase comprises:

[0085] - 60 to 85%, preferably 78.1%, of principal mineral content

[0086] 13 to 40%, preferably 16.9% solvent

[0087] 1 to 3%, preferably 2.2% binder,

[0088] 1 to 3%, preferably 2.2% plasticizer

[0089] 0 to 1%, preferably 0.6% of dispersant, the percentages being understood as weight of the total weight of the main mineral phase.

[0090] According to one embodiment, the main mineral loading phase comprises: 78.1g of main mineral loading

[0091] 16.9 g of solvent

[0092] - 2.2g of binder

[0093] - 2.2g of plasticizer

[0094] 0.6g of dispersant.

[0095] According to one aspect, the invention relates to a gas-tight seal 1, for example formed on an electrochemical cell.

[0096] The sealing compound 1 is formed from the composition as described above and advantageously comprises the main mineral filler and the additional mineral filler. The sealing compound 1 is advantageously formed from the fluid composition after it has undergone a treatment, advantageously a thermal treatment, intended to solidify the compound 1. The compound 1 advantageously does not include the solvent. The compound 1 is advantageously more gas-tight than the composition.

[0097] 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.

[0098] As a preferred option, the sealing gasket exhibits no leakage rate up to 500 mbar (50,000 pascal) of overpressure at 700°C.

[0099] As a preferred option, the sealing gasket exhibits no leakage rate up to 800 mbar (or 80,000 pascals) of overpressure at 800°C.

[0100] As a preferred option, the sealing gasket has a leakage rate of less than 10' 4 mbar.l / s (i.e. 1000 pascal. l / s) at 1000 mbar d(100,000 pascal) of overpressure at 800°C.

[0101] 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.

[0102] In 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.

[0103] In one embodiment, the preparation step for the additional mineral loading phase includes grinding the vermiculite and 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 machine, etc.).

[0104] In 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%.

[0105] According to one aspect, the invention relates to a method for forming a sealing joint 1.

[0106] The process includes a step of depositing the fluid composition. The composition obtained, as described above, is applied to an electrochemical cell 2 or, for example, a half-electrochemical cell 10, 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 deposition of the composition in a fluid state allows the composition to conform to the roughness of the opposing surfaces and thus to form a higher-quality interface.

[0107] 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.

[0108] As an example, a heat treatment at 860°C for one hour in an air oven with temperature ramps of 100°C / h is carried out on the composition and the surfaces between which it is arranged.

[0109] 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 adhesion sites and as germination / growth sites for the glass-ceramic were observed within the composition.

[0110] 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.

[0111] Example 1: Preparation of a main mineral phase.

[0112] 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 (such as MEK-ethanol), and adding 78 g of the main mineral filler (for example, G018-311 glass-ceramic sold by Schott). The mixture is then homogenized using a planetary mixer. Next, 2.16 g of binder (such as PVB) and 2.16 g of plasticizer, dissolved in 13.24 g of solvent (such as a 50%-50% MEK-ethanol mixture), are added to this mixture. The entire mixture is then homogenized using a planetary mixer.

[0113] Example 2: Preparation of the additional mineral phase mixture

[0114] To prepare this mixture, Thermicullite® 866 plates (marketed by Flexitallic) were used. This material is a mixture of exfoliated vermiculite and steatite. These plates were ground into a powder by hand for 15 minutes using a mortar and pestle until a relatively fine and homogeneous powder was obtained. SEM analysis revealed that the additional mineral filler, and more specifically the ground vermiculite / steatite mixture, takes the form of sheets or platelets of varying sizes, ranging from a few microns to about one hundred microns.

[0115] Example 3: Obtaining the composition according to the invention

[0116] 5% by mass of the powder prepared in example 2 is added to the main mineral filler phase paste prepared in example 1. The mixture is then carried out until a homogeneous mixture is obtained.

[0117] The resulting composition can be used to form the sealing gasket 1 of an electrochemical cell. Example 4: Comparative sealing measurements between a reference gasket and the invention. Sealing tests were conducted to validate the benefit obtained with the invention. A temperature- and pressure-based leakage rate measurement test was used. The setup shown schematically in Figure 3 allows testing 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 gasket 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.

[0118] 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 being studied.

[0119] In the same setup, shown in Figure 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.

[0120] At 700°C (Figure 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 (figure 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).

[0121] At 800°C, (Figure 5A) the leakage rate of the reference seal reaches 5.10 -4 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 (Figure 5B) exhibits no measurable leakage rate up to 800 mbar (i.e., 80,000 pascal) of overpressure, and a leakage rate of less than 10' 4 mbar.l / s (i.e. 1000 pascal. l / s) 1000 to 1000 mbar (i.e. 100,000) of overpressure.

[0122] The tests carried out show a real gain of the seal 1 according to the invention compared to a reference seal.

[0123] The invention is not limited to the embodiments described above and extends to all embodiments covered by the invention. LIST OF REFERENCES

[0124] 1. Joint

[0125] 2. Interconnector 3. Gas channel

[0126] 4. Electrochemical cell

[0127] 5. Wedge

[0128] 6. Charge

[0129] 7. Gas supply and measurement 8. Electrical contact layer

[0130] 9. Additional mineral charge

[0131] 10. Electrochemical half-cell

Claims

DEMANDS 1. Fluid composition intended for the formation of a gas-tight seal of a solid oxide electrochemical system characterized in that it comprises a main mineral filler phase and an additional mineral filler phase, the main mineral filler phase comprising a main mineral filler selected from at least one glass-ceramic and / or silica powder, the additional mineral filler phase comprising a mixture in powder form of vermiculite and steatite, the mixture representing from 1% 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 additional mineral filler phase consists of the mixture and represents from 1 to 10% by weight of the total weight of the composition.

4. 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.

5. 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.

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

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

8. 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.

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

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

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

12. Composition according to any one of the preceding claims, wherein the main mineral filler 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 are in weight of the total weight of the main mineral loading phase.

13. 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.

14. 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.

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

16. A method for manufacturing a composition according to any one of claims 1 to 13 comprising a step of preparing a main mineral filler phase including the addition of a main mineral filler in at least one solvent, a step of preparing the mixture of the additional mineral filler phase including the reduction to powder form of vermiculite and steatite, a step of assembling 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.

17. Method for manufacturing a sealing gasket comprising - an application of the fluid composition according to any one of claims 1 to 13 on a first surface, - the application of a second surface onto the fluid composition, - 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. 17 18. Use of a fluid composition according to any one of claims 1 to 13 as a gas seal for a fuel cell or fuel cell component.

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