JP5287357B2 - Gasket for fuel cell, fuel cell and fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell gasket, a fuel cell, and a fuel cell system.

  Solid polymer fuel cells that use hydrogen or liquid organic compound reformed fuel, or solid polymer fuel cells that use liquid organic compounds such as methanol, ethanol, and dimethyl ether as fuel, have low noise and low operating temperature ( (About 70 to 80 ° C.) and has features such as easy fuel supply. Therefore, a wide range of uses are expected as a portable power source, a power source for an electric vehicle, or a power source for an electric motorcycle, an assisted bicycle, and a light vehicle such as a wheelchair or a senior car for medical care.

  These fuel cells have a unit cell including a membrane-electrode assembly in which electrodes are formed on both surfaces of an electrolyte membrane that moves protons, and a separator placed so as to face each of the electrodes. The separator is formed with a flow path (channel) for circulating fuel or oxidant.

  In order to allow fuel or an oxidant to flow through the flow path of the separator, it is an important design matter to ensure the sealing property (sealability) at the contact surface between the separator and the membrane-electrode assembly. This is because if fluid such as fuel leaks from the contact surface to the outside of the cell, it causes problems such as a decrease in output performance.

  As examples of conventional techniques, Patent Documents 1 to 5 disclose sealing means on the contact surface.

  In Patent Document 1, a functional membrane material (ion exchange membrane, separator membrane, etc.) for battery configuration and a gasket (made of rubber) having a predetermined pattern are joined and integrated without an adhesive layer. A membrane member is disclosed.

  Patent Document 2 discloses a fuel cell separator adhesive seal structure in which a seal rubber molded in advance as a separate body is adhered to a groove portion provided in a required portion of a carbon separator as a retrofit.

  Patent Document 3 discloses a fuel in which a distributor plate (separator) integrated with a seal in contact with a membrane-electrode assembly has elasticity, is plastically deformable, has conductivity, and has a convex portion on the seal. A battery is disclosed. Since the separator and the seal can be manufactured from the same material, the above-described rubber gasket can be omitted, and a low-cost separator can be provided.

  Patent Document 4 discloses a graphite gasket material in which an expanded graphite sheet is impregnated with a liquid thermosetting resin and then laminated on both sides of a thin metal plate. This graphite gasket material is used for engine gaskets and has mechanical strength against high-load tightening.

  Patent Document 5 discloses an impregnated body containing an isocyanate and / or an epoxy resin in a synthetic resin impregnated body made of expanded graphite.

JP 2001-319669 A JP 2002-033109 A U.S. Pat. No. 5,928,807 Japanese Patent Laid-Open No. 1-158269 JP 2002-265212 A

  An object of the present invention is to provide a gasket that has high bending strength even if the plate thickness is small, is easy to manufacture, and improves the airtightness of the fuel cell.

  The gasket for a fuel cell of the present invention is a gasket for a fuel cell used as a seal between an electrolyte membrane and a separator, wherein the gasket is composed of a molded body obtained by mixing graphite particles and a resin binder, and the graphite particles And the resin binder are homogeneously dispersed.

  Further, the fuel cell of the present invention comprises a separator having an anode flow path for flowing fuel, a separator having a cathode flow path for supplying an oxidant, and an anode / electrolyte membrane / cathode disposed between the two separators. In the fuel cell having the configured membrane-electrode assembly, the fuel cell gasket is interposed between each separator and the electrolyte membrane.

  ADVANTAGE OF THE INVENTION According to this invention, even if thickness is small, a bending strength is high, manufacture is easy, and the gasket which improves the airtightness of a fuel cell can be provided.

It is sectional drawing of the single cell of the fuel cell which shows the Example by this invention. It is a top view of the separator used for the single cell of FIG. It is PP sectional drawing of the separator of FIG. 2A. It is sectional drawing which shows the state which an internal leak produces when the conventional gasket is used. It is a top view of the gasket which shows the Example by this invention. It is sectional drawing of the single cell which shows the Example by this invention. It is sectional drawing of the single cell which shows the other Example by this invention. It is sectional drawing of the single cell which shows the other Example by this invention. It is sectional drawing of the fuel cell system which shows the Example by this invention.

  An object of the present invention is to provide a new sealing means for a fuel cell (cell) including a membrane-electrode assembly (hereinafter referred to as MEA) sandwiched between two separators.

  The technical problems to be solved by the present invention are (1) that even if a seal is provided, it does not become an obstacle to making the separator thin, (2) that external leakage can be sufficiently suppressed even at low loads, and (3) internal leakage. It is also possible to prevent.

  In order to explain these three technical problems, the structure of a conventional fuel cell will be described.

  FIG. 1 illustrates a cross-sectional structure of a single cell according to the prior art. The basic structure of the single cell of the present invention is the same.

  In this figure, there is MEA in the center of the cross section of this single cell. This MEA has a three-layer structure in which the anode 101 is laminated on the upper surface of the electrolyte membrane 103 and the cathode 102 is laminated on the lower surface. The fuel-side separator 104 (also referred to as a first separator) has a fuel channel 105 and is disposed so that the channel surface is in contact with the anode 101. The oxidant side separator 106 (also referred to as a second separator) has an oxidant channel 107, and the channel surface 107 is in contact with the cathode 102. Gaskets 108 and 109 are provided on the outer peripheral portion of the separator so that fuel and oxidant do not leak to the outside, and so that one reactant does not leak into the flow path of the other reactant. Each reactant is separated by the gaskets 108 and 109 or the electrolyte membrane 103.

  Note that a through hole (referred to as a manifold) for supplying the reactant and a through hole for discharging are omitted from the cross section of FIG.

  2A shows a top view of the separator used in the single cell of FIG. 1, and FIG. 2B is a cross-sectional view of the separator of FIG. 2A taken along the line P-P. Here, a separator structure corresponding to the fuel-side separator 104 in FIG. 1 will be described.

  The fuel separator 204 is formed with through holes for a fuel supply manifold 210, a fuel discharge manifold 211, an oxidant supply manifold 212, an oxidant supply manifold 213, a coolant supply manifold 214, and a coolant discharge manifold 215.

  Fuel is introduced from the fuel supply manifold 210 into the plane of the separator 204. A plurality of flow paths 205 for flowing fuel are formed (in this example, 5 as an example), and these flow paths 205 are bent and pass through the surface of the separator 204 and communicate with a fuel discharge manifold 211 provided in a diagonal direction. Has been. The channel 205 is delimited by a convex portion 206 (also referred to as a rib). Note that the number of the flow path 205 may be one, but in order to reduce the pressure loss of the fuel or the like passing through the separator flow path, a plurality of the flow paths 205 are usually used. In addition to the meandering shape as shown in FIG. 2A, a linear pattern or other various patterns can be adopted as the flow path pattern.

  The groove width and groove depth of the fuel flow path 205 can be set to optimum dimensions according to the fuel type and flow rate. Optimal dimensions are set to reduce pressure loss and to increase cell voltage (or output) as much as possible. If the distance between the protrusion 206 and the MEA on the flow path 205 becomes too large, the electrical resistance increases, so the width of the groove is set to a range of 1 to 5 mm and a depth of 0.1 to 5 mm. The A groove width of 1 to 2 mm and a groove depth of 0.3 to 2 mm are particularly desirable.

  The oxidant channel can be formed on the back surface of FIG. 2A. The oxidant is supplied from the oxidant supply manifold 212 and discharged to the oxidant discharge manifold 213 via the oxidant flow path formed on the back surface of the fuel side separator. Although the oxidant flow path is not shown because it is formed on the back surface of FIG. 2A, it may be the same pattern as the fuel flow path 205 of FIG. 2A or may be different. Alternatively, the oxidant can be discharged from the manifold 212 by using the manifold 213 as a supply manifold and flowing from the bottom to the top.

  Similarly, the groove width and groove depth of the oxidant channel can be set to optimum dimensions according to the type and flow rate of the oxidant. If the distance between the MEA on the oxidant flow path and the adjacent convex part becomes too large, the width of the groove should be in the range of 1 to 5 mm and the depth of 0.1 to 5 mm because the electrical resistance increases. Is desirable. Further, a groove width of 1 to 2 mm and a groove depth of 0.3 to 2 mm are particularly desirable.

  The cooling water flow path may be formed on the back surface of the fuel flow path in FIG. 2A, or the fuel flow path on the front surface in FIG. 2A may be replaced with a cooling water flow path to form an oxidant flow path on the back surface. . The cooling water is supplied from the cooling water supply manifold 214 and discharged to the cooling water discharge manifold 215 via the cooling water flow path. Here, similarly to the fuel flow path 205 and the oxidant flow path, the cooling water flow path can also have an arbitrary pattern, and can be supplied from the manifold 215 and discharged from the manifold 214.

  When liquid fuel such as methanol is used, the cooling water supply manifold 214 and the discharge manifold 215 may be omitted as long as the heat generated by the battery can be discharged out of the battery together with the fuel drainage or the oxidant exhaust gas.

  Taking the cell structure described above as an example, the first technical problem (thinning the separator) will be described.

  One means for applying a seal in the separator of FIG. 2A is a means for using a part of the separator itself as a seal. That is, the separator shown in FIG. 2A is manufactured from a mixture of graphite and a binder by a compression molding method, a convex easily compressible structure (low density region) is formed on the outer edge of the separator, and the convex portion is crushed so that the airtightness of the cell. Can be obtained. In order to obtain a sealing property by tightening the convex portion with a predetermined load, it is necessary to reduce the density. In order to simplify the battery structure by reducing the number of bolts or the like, it is desirable to obtain a sufficient sealing performance with as low a load as possible.

  When the low density region is formed in the portion to be sealed in this way, the MEA is sandwiched between two separators, and pressure is applied from the outside of the separator, so that the low density region can be compressed and function as a seal. . For example, a low density region having a density of 10 to 50% of the density of the flow path surface of the separator is formed on the outer edge of the graphite separator, and the low density region is compressed and sealed. As an example, the assumption example in which the low density region 216 is formed at the position of the dashed line in FIG. 2A is shown.

  However, when the low density region 216 is provided at the outer edge portion of the separator, the bending strength of that portion is reduced, and cracking is likely to occur starting from the low density region 216. This problem becomes significant when the thickness of the separator 204 is reduced to 1 mm or less. The above-mentioned problem can be avoided by increasing the thickness of the separator. However, if a thin separator with a thickness of less than 1 mm, particularly 0.3 mm or less, breakage occurs in the low density region.

  When the low density region 216 is formed on one surface, the lower portion thereof has substantially the same density, and the density decreases in the thickness direction of the separator. Since the entire low density region has low bending strength, the low density region is easily damaged from the outer edge of the separator in which the low density region 216 is formed. This does not depend on the manufacturing method, and is the same when graphite is compression molded or injection molded.

  Further, as the separator becomes thinner, it becomes difficult to reduce the thickness of the gasket, which causes manufacturing problems.

  Since the MEA is compressed until an appropriate compression ratio is obtained and the function as a cell is exhibited, the distance between the two separators is basically governed by the thickness of the MEA. However, if the gasket is thicker than the MEA, the gasket installation portion on the separator must be thinned. As a result, the thicker the gasket, the thicker the entire separator becomes in order to ensure the bending strength of the separator. Thus, if the thickness of the gasket is made close to the MEA, it is not necessary to make the gasket installation portion thin, and the thickness of the separator itself can be made as thin as possible. Usually, since the MEA thickness is 1 mm or less, it is desirable to use a thickness of 1 mm or less when using one gasket and 0.5 mm or less when using two sheets.

  However, according to the graphite gasket manufactured by the conventional impregnation method, the thinner the graphite molded body before impregnation with the epoxy resin or the like, the lower the bending strength and the more fragile. It was difficult. In particular, when the thickness is 0.5 mm or less, cracks are likely to occur, and the handleability is extremely poor. This is because a material for adhering graphite particles to each other is not added to the graphite molded body before resin impregnation.

  Thus, from the viewpoint of the mechanical strength of the separator and the manufacturing method of the gasket, the first technical problem is a great obstacle to the realization of a thin separator.

  Next, a second technical problem (suppression of external leakage at a low load) will be described. In the above description, conversely, if the convex portion is formed so that the outer edge portion has a high density and has a dense structure, damage from the outer edge portion can be avoided even if the separator thickness is reduced. . That is, if only focusing on the solution of the first technical problem, it is possible to obtain airtightness even with a thin separator.

  However, if the convex portions to be sealed are made dense, the compressibility of the convex portions with respect to the load decreases, and as a result, the airtightness cannot be secured unless the separators are fastened with a high load.

  For example, if the density of the region 216 to be sealed is the same as that of the flow path portion in FIG. 2A, that is, if the entire separator is molded at a high density, the separator 216 can be made thin while preventing damage from the region 216. Can be planned. However, since the convex portion for sealing becomes hard, even if pressure is applied from the outside of the separator, it is hardly compressed and leakage to the outside cannot be stopped or sealing cannot be performed unless an excessive load is applied. In the latter case, the MEA electrolyte membrane breaks and internal leaks occur.

  Similarly, in the case of a separator produced by pressing a metal plate, when a convex portion is formed on a portion where the separator is to be sealed, the portion is hard and the deformation amount due to compression is small. It is difficult to achieve.

  Thus, the second technical problem is to prevent external leakage with a low load.

  As explained above, if the seal is made of the same material as the separator and is formed at the same time, it is extremely possible to make the separator thinner (first technical problem) and lower load tightening (second technical problem). It becomes difficult. Thus, there is a limit to means for forming a seal with the same configuration as the separator physically and chemically.

  Next, the third technical problem (preventing internal leakage) will be examined.

  2B has a concavo-convex portion formed by the fuel flow path 205 and the convex portion 206. In this portion, a member having a sealing function is installed, and the separator is interposed through the contacting electrolyte membrane. Crimped. When this seal is incomplete, a part of the fuel supplied from the fuel supply manifold 210 flows into the opposite side of the electrolyte membrane (that is, the channel surface on the oxidant side). This is called an internal leak. Even in the flow path in the vicinity of the fuel discharge manifold 211, the seal is secured by forming a laminated structure of the seal and the electrolyte membrane, so the internal leak generation mechanism is the same.

  Now, according to the means for reducing the density of a part of the graphite separator described above and obtaining a seal, the protrusion 206 on the PP cross section is also reduced in density. With such a structure, the convex portion 206 is deformed by tightening the separators, and the flow path 205 is closed when the separator is bent. On the contrary, if the convex part 206 is made high density, the tightening load must be increased. Since the electrolyte membrane is sandwiched between the convex portion 206 and the separator facing the convex portion 206, the electrolyte membrane may be damaged, resulting in a problem that the output of the cell is reduced.

  Further, instead of means for reducing the density of a part of the graphite separator, means for using a flat gasket made of a rubber material can be considered. However, the following new problems arise.

  FIG. 3 shows a structural example of two gaskets and an electrolyte membrane in the PP cross section of FIG. 2B. In the drawing, the structure when an internal leak occurs is expressed with some emphasis. A gasket 308 in contact with the fuel flow path 305 (corresponding to the seal 108 in FIG. 1) is in contact with the convex part 306 of the fuel flow path (corresponding to the convex part 206 in the PP cross section in FIG. 2B). The electrolyte membrane 303 is disposed on the gasket 308, and the gasket 309 on the oxidant flow path side is further disposed on the gasket 308, and is sandwiched between the fuel side separator 304 and the oxidant side separator 310.

  A gasket using a rubber material has a large compressive displacement characteristic and is easy to obtain a seal even at a low load. On the other hand, as the tightening load increases, deformation in the lateral direction also progresses, and the gaskets 308 and 309 may sag into the space of the flow path 305, resulting in a gap 317. When this gap is formed, part of the fuel flowing through the flow path 305 leaks into the gap 317 and enters the oxidant flow path side of the electrolyte membrane 303. Due to such a mechanism, the internal leak occurs due to the lateral extension caused by the compression of the rubber-based flat gasket, and is a phenomenon that is often seen particularly when the tightening load between the separators is large.

  In addition, the gasket repeatedly undergoes thermal expansion and contraction due to the heat cycle of the power generation due to repeated starting and stopping of the fuel cell. The rate of thermal expansion is defined by the linear expansion coefficient of the gasket, and is particularly large for elastic rubber such as fluoro rubber and ethylene / propylene rubber. As a result, the deformation of the gasket as shown in FIG. 3 is further promoted.

  On the other hand, a gasket is installed in a point shape on the rib 206 near the PP cross section of the manifold 210 in FIG. 2A (including the corresponding portion of the manifold 211), and a convex gasket is bonded to the separator on the other separator surface. A means for forming a cell is also conceivable.

  However, deformation of the electrolyte membrane 303 and the oxidant side gasket 309 cannot be prevented only by eliminating the portion of the gasket 308 immediately above the flow path in FIG. 3 (that is, above the flow path 305). Therefore, it is difficult to completely eliminate the gap 317 even by means for forming the convex gasket. This is the third technical problem.

  In addition to the above three technical problems, chemical durability such as water resistance, reduction resistance by hydrogen, and oxidation resistance by oxygen is also required as a function required for the gasket. Therefore, when combined with a metal material as described in Patent Document 4, hydrogen ions in the electrolyte membrane are exchanged by elution of metal ions (especially iron ions), increasing the membrane resistance, and molecules of the membrane due to hydrogen peroxide. The destruction of the structure proceeds. Therefore, material selection considering the above-mentioned chemical durability is also an important requirement.

  As a result of intensive studies to solve the three technical problems, the inventors have constructed a new means.

  The gasket for a fuel cell of the present invention is a gasket for a fuel cell used as a seal between an electrolyte membrane and a separator, wherein the gasket is composed of a molded body obtained by mixing graphite particles and a resin binder, and the graphite particles And the resin binder are homogeneously dispersed.

  Further, the fuel cell of the present invention comprises a separator having an anode flow path for flowing fuel, a separator having a cathode flow path for supplying an oxidant, and an anode / electrolyte membrane / cathode disposed between the two separators. In the fuel cell having the configured membrane-electrode assembly, the fuel cell gasket is interposed between each separator and the electrolyte membrane.

  Hereinafter, description will be made using examples.

  In the first embodiment of the present invention, the gaskets 108 and 109 in FIG. 1 are replaced with the graphite-based gasket of the present invention.

  The graphite-based gasket of the present invention is obtained by mixing graphite and a resin binder and curing the binder by thermoforming. The shape was a sheet shape shown in FIG. In addition, the graphite to be used can select arbitrary graphite powder. In particular, expanded graphite or massive graphite is excellent in compression elasticity.

  First, the manufacturing method of the preforming sheet before cutting into the shape of FIG. 4 using expanded graphite is demonstrated.

  The raw material graphite is particulate natural graphite (for example, natural scaly graphite).

  This natural graphite is immersed in concentrated sulfuric acid or a mixture of concentrated sulfuric acid and concentrated nitric acid to expand the interval between the graphite layers, and then washed with water and dehydrated to sufficiently remove the acid adhering to the surface of the graphite. . Thereafter, the graphite is rapidly heated and heat-treated.

  Through this series of processing steps, expanded graphite having a bulk density several tens of times that of the raw graphite powder can be produced. The obtained powdery expanded graphite (referred to as expanded graphite particles) has high purity with an impurity concentration of several ppm or less, and has elasticity. Here, expanded graphite particles refer to those whose main component is expanded graphite by the above treatment, but those containing graphite other than the main component expanded graphite (for example, untreated natural graphite) are also expanded graphite particles. I will call it. That is, expanded graphite particles including those whose main component is larger than 50% by volume are referred to as expanded graphite particles.

  Next, a thermosetting resin binder is added to the expanded graphite particles. As this resin binder, phenol resin powder, epoxy resin, or the like can be used. In the present invention, a thermosetting resin is particularly desirable, but if it is a resin that does not soften at the operating temperature of the fuel cell and does not react with the reactants of the fuel cell (organic substances such as hydrogen and methanol and oxygen), thermoplasticity is sufficient. These materials can also be applied. For example, a thermoplastic material such as a polyamide resin, a polycarbonate resin, or a polyphenylene oxide resin can be used instead of the thermosetting material. If a thermoplastic resin is used, there exists an advantage which can shorten the molding time of a gasket.

  Here, a phenol resin was selected, and the amount added was 10 to 30% (weight composition ratio) with respect to the total weight. In the present invention, the gasket thickness only needs to be compressed to a required size according to the load of the battery, and therefore, it is possible to set various compositions according to the load.

  The graphite sheet described in the following description means a gasket formed by molding a mixture of graphite (expanded graphite particles) of the present invention and a resin.

  In the present invention, expanded graphite particles and a binder are mixed and kneaded by a Henschel mixer. The mixing method is not limited to this, and any method such as stirring and kneading can be applied. As the solvent that can be added to the powder at the time of mixing, any non-reactive solvent such as propyl alcohol can be selected. It is important to uniformly disperse the binder and graphite powder before molding the gasket in order to develop the elastic properties of the gasket.

A sheet-shaped preformed sheet is produced from the kneaded product using a roll press or a batch press. This is further thinned to a predetermined thickness to produce a graphite sheet having the required thickness accuracy. The density of the sheet thus produced is set in the range of 1.2 to 2.0 g / cm ³ . More desirably, is set to a range of 1.6~1.8g / cm ^3, when incorporated into the separator, clamping pressure can be obtained a sufficient air-tightness at a low pressure of 3~7kg / cm ³ .

In this way, when the MEA electrode layer is compressed in the range of ³ to 7 kg / cm ² , the initial thickness is determined so that the thickness of the gasket of the present invention is substantially the same. MEA and a gasket can be installed on a simple separator. As a result, there is no need to provide a step or a convex portion on the separator where the gasket is installed, and the separator structure can be complicated or molding defects can be avoided.

Further, when the density of the graphite sheet is set to 1.2 to 1.6 g / cm ³ , the pressure range can be further reduced. This is effective when the strength of the electrolyte membrane is relatively weak.

On the other hand, when the density of the graphite sheet is 1.8 g / cm ³ or more, if the resin membrane is reinforced with resin, the mechanical strength of the electrolyte membrane can be increased and low load tightening can be realized. . An embodiment with resin reinforcement will be described later.

  According to the above-mentioned mixing method of graphite and resin, the resin functions as a kind of binder before molding the gasket. As a result, even if the thickness of the gasket is 1 mm or less, the gasket is not damaged. The method of the present invention is suitable for manufacturing a thin gasket having a thickness of 1 mm or less, particularly 0.5 mm or less.

  On the other hand, if a method of impregnating the sheet with a resin after pre-manufacturing a graphite molded body (sheet-shaped molded body not containing a resin), the resin concentration in the vicinity of the graphite surface increases. Because of the slow penetration of the resin, a concentration difference was likely to occur between the graphite interior and the vicinity of the surface. In particular, when the resin segregates on the surface, there is a problem that the adhesiveness between the cured resin layer and the separator deteriorates.

  According to the mixing method of the present invention, since the resin is dispersed almost uniformly on the surface and in the bulk, the problem of adhesion can be avoided. Furthermore, if the pressure at the time of forming is controlled, it is easy to adjust the density of the graphite sheet, so that the elasticity necessary for the gasket can be obtained.

  On the other hand, when the resin is filled into the fine pores of the graphite molded body by the impregnation method, a hard columnar structure is formed in the thickness direction of the graphite molded body after the resin is cured. This structure is suitable for closing the gas passage and obtaining airtightness.

  However, the columnar structure repels the compressive force applied to the gasket and acts like a kind of beam. As a result, the elasticity that should originally be provided as a gasket is insufficient.

  Since the unevenness on the surface of the separator is usually about 50 μm, a displacement amount of at least 50 μm is required when a compressive force is applied to the gasket. In response to this requirement, the impregnation method has insufficient properties to expand and contract in the thickness direction of the gasket (so-called elasticity), and there is a problem in the adhesion between the separator and the gasket.

  It is also conceivable to adjust the amount of resin added so that the resin does not fill the entire pore volume of the graphite compact. If this can be realized, it seems that the strength of the beam can be reduced.

  However, since the resin is gradually filled from the pores on the surface of the graphite molded body, the amount of the resin on the surface is large and decreases inside. As a result, the surface of the gasket is hard and the inside is soft. Such a curing phenomenon on the gasket surface is also a factor that hinders the adhesion between the separator and the gasket. Furthermore, a decrease in the amount of resin inside the gasket impairs the strength inside the gasket and lowers the strength of the entire gasket.

  On the other hand, according to the mixing method of the present invention, since the granular or lump resin is mixed with the graphite powder, the resin particles are not strongly connected together. For this reason, the resin does not exhibit resilience like a beam inside the gasket, and the graphite particles expand and contract in the thickness direction throughout the gasket. Due to this characteristic, the gasket surface is also deformed minutely and adheres closely to the separator surface, thereby preventing gas leakage.

  The gasket 408 (graphite sheet) of the present invention can be formed into an arbitrary shape by punching with a mold. FIG. 4 shows one specific example.

  The thermal expansion coefficient (linear expansion coefficient) of the graphite sheet with adjusted density is less than 0.1% / ° C., and usually 0.02 to 0.05% / ° C. Compared with conventional rubber, fluororubber is about 2% at an environmental temperature of 100 ° C. or lower, and it can be seen that the gasket of the present invention has a characteristic that it is difficult to thermally expand. Due to this excellent low thermal expansibility, deformation and internal leakage due to heat generation of the fuel cell can be prevented in the cross-sectional structure shown in FIG.

  The graphite sheet 408 has an opening 418 at the center so that the electrode and the flow path are in contact with each other. Further, the fuel supply manifold 410, the fuel discharge manifold 411, the oxidant supply manifold 412, the oxidant discharge manifold 413, the cooling water supply manifold 414, and the cooling water discharge manifold 415 are formed at substantially the same position as the separator of FIG. 2A. .

  In the second embodiment of the present invention, an insulating layer is formed on the contact surface between the seal and the separator. The configuration is shown in FIG.

  As in FIG. 1, the fuel flow path 505 is formed between the fuel side separator 504 and the anode 501. On the other hand, an oxidant side separator 506 having an oxidant flow path 507 faces the cathode 502. The anode 501 and the cathode 502 are held by the electrolyte membrane 503.

The anode side gasket 508 and the cathode side gasket 509 of the present invention are formed of a graphite sheet having the shape shown in FIG. 4 and a resin insulating layer 519 described later. The thickness of the graphite sheet was 150 μm (tolerance ± 30 μm), and the density was 1.7 g / cm ³ .

An epoxy resin is applied to one side of the graphite sheet with a dispenser, and is pressed and cured to a separator 504 having a fuel flow path 505 and a separator 506 having an oxidant flow path 507 to form an anode side gasket 508 and a cathode side gasket 509. did. The addition amount of the epoxy resin by the dispenser was adjusted so that the load upon curing was 50 μm at 1 kg / cm ³ . The load at the time of curing was controlled by a hot press machine by sandwiching a separator 504 or 506 with an anode side gasket 508 or a cathode side gasket 509 bonded on two metal flat plates. The curing temperature was 100 ° C. and the curing time was 2 hours. As a result, an extremely thin insulating layer 519 was formed.

The cell having the configuration shown in FIG. 5 was assembled so that the surface of the graphite gasket was in contact with the electrolyte 503 portion of the MEA (including the anode 501, the electrolyte membrane 503, and the cathode 502). The average tightening load of the separators 504 and 506 was 7 kg / cm ³ .

  Further, two current collector plates were arranged outside the separators 504 and 506, respectively. Insulating resin plates such as PTFE (polytetrafluoroethylene) were inserted between the current collector plates and the end plates, and bolts were passed through the end plates at both ends and tightened with springs from the outside of the end plates.

  In order to measure the air tightness of the single cell of this embodiment, helium gas equivalent to 50 kPa with respect to atmospheric pressure is filled from the piping connector of fuel, oxidant and cooling water, and the internal pressure change is measured by the pressure sensor. did. The initial pressure of 50 kPa maintained a high pressure of 49.8 kPa even after 10 minutes, and it was found that there was almost no leakage to the outside.

  Further, when 50 kPa of helium gas was charged only on the fuel side and the oxidant side was opened to the atmosphere, the pressure on the fuel side maintained high airtightness of 48.9 kPa after 10 minutes. Compared to the configuration of FIG. 6 (Example 3) described later, when the gasket of the present invention was directly bonded to the separator, the gasket 608 was firmly fixed to the separator, and displacement was less likely to occur. As a result, it is considered that the gap 317 shown in FIG.

Thereafter, hot water at 70 ° C. was circulated through the single cell, pure hydrogen was supplied as fuel, and air was supplied to the oxidant, and the power generation test and the stop operation were repeated. The power generation test was performed with a fuel utilization rate of 85%, an oxidant utilization rate of 55%, a current density of 0.3 A / cm ² and a power generation time of 3 hours. After power generation, the cooling water inlet temperature was set to 30 ° C., and the battery was rapidly cooled. Thereafter, after confirming that the temperature became 30 ° C. after about 1 hour, the cooling water inlet temperature was again raised to 70 ° C., and the previous power generation test was resumed. Thus, the heat cycle test by repeating power generation and cooling was performed 200 times.

  After the above heat cycle test, an airtight test was performed again. As a result, helium gas equivalent to 50 kPa with respect to atmospheric pressure was filled from the piping connector of fuel, oxidant and cooling water, and the internal pressure change was measured with a pressure sensor. The initial pressure of 50 kPa maintained a high pressure of 49.5 kPa even after 10 minutes, and it was found that almost no leakage to the outside occurred.

  Further, when 50 kPa of helium gas was charged only on the fuel side and the oxidant side was opened to the atmosphere, the pressure on the fuel side maintained high airtightness of 48.5 kPa after 10 minutes. It can be seen that the internal leak suppression effect is extremely excellent and the present invention is effective.

  In this example, an epoxy resin was used for the insulating layer (adhesive layer), but the shape did not change depending on the operating temperature of the fuel cell, water resistance, reduction resistance by hydrogen, oxidation resistance by oxygen, etc. Any material can be used as long as it has the chemical durability of

  In the third embodiment of the present invention, an insulating layer is formed on the contact surface between the seal and the electrolyte membrane. The configuration is shown in FIG.

  Similar to FIG. 1, the fuel flow path 605 is formed between the fuel-side separator 604 and the anode 601. On the other hand, an oxidant side separator 606 having an oxidant flow path 607 is opposed to the cathode 602. The anode 601 and the cathode 602 are held by the electrolyte membrane 603.

The graphite gasket used in this example includes a graphite sheet and an adhesive layer (also referred to as an adhesive layer) described later. Graphite sheets 608 and 609 having the shape shown in FIG. 4 were manufactured. The thickness was 150 μm (tolerance ± 30 μm), and the density was 1.7 g / cm ³ .

  An acrylic adhesive layer is formed on one side of the graphite sheets 608 and 609, and both the electrolyte membrane 603 of the membrane-electrode assembly and the graphite sheets 608 and 609 are pressure-bonded together so that the acrylic adhesive layer is the electrolyte. The film 603 was adhered. As needed, you may heat in the range of the heat-resistant temperature of an electrolyte membrane. For example, a fluorine-based electrolyte membrane has a heat resistance of 80 to 90 ° C. In this case, the laminate of the gasket and the electrolyte membrane is accommodated between two rigid plates, and the heat treatment can be performed in the above temperature range in a state where a load is applied to the upper and lower portions of the rigid plate. . For the load, a bolt can be passed through the rigid plate, and the load can be adjusted by a spring. The adhesive layer 619 of this example was controlled to a thickness of 50 μm by installing two metal spacers with a thickness of 50 μm on the outer periphery of the gasket and adding a load to the two rigid plates.

  Since a gasket is also required on the opposite surface of the electrolyte membrane 603, a gasket on which an acrylic adhesive layer is formed is adhered to the electrolyte membrane 603 as described above.

  The gasket may be bonded to each side of the electrolyte membrane 603, or a membrane-electrode assembly may be inserted between the two gaskets and may be performed simultaneously.

  Further, the gasket adhesive is not limited to acrylic, and any material that does not react or dissolve with fuel, oxidant, or water can be used as the adhesive. In addition, it is necessary to use a material that does not change in the operating temperature range of the fuel cell. Any material can be used as long as the shape does not change depending on the operating temperature of the fuel cell and has chemical durability such as water resistance, hydrogen reduction resistance, and oxygen oxidation resistance.

As described above, a laminate of two gaskets and a membrane-electrode assembly (including an anode 601, an electrolyte membrane 603, and a cathode 602), a separator 604 in which a fuel channel 605 is formed, and an oxidant channel 607 are formed. The cell having the structure shown in FIG. 6 was assembled. The average tightening load of both separators was 7 kg / cm ³ . Two current collector plates were disposed outside the separators 604 and 606, respectively. Insulating resin plates such as PTFE (polytetrafluoroethylene) were inserted between the current collector plates and the end plates, and bolts were passed through the end plates at both ends, and then tightened with springs from the outside of the end plates.

  When the airtightness of such a single cell was measured, helium gas equivalent to 50 kPa with respect to atmospheric pressure was filled from the piping connector of fuel, oxidant, and cooling water, and the internal pressure change was measured with a pressure sensor. The initial pressure of 50 kPa maintained a high pressure of 49.6 kPa even after 10 minutes, and it was found that there was almost no leakage to the outside.

  Further, when 50 kPa of helium gas was charged only on the fuel side and the oxidant side was opened to the atmosphere, the pressure on the fuel side maintained high airtightness of 47.7 kPa after 10 minutes. Although the result is that the internal leak is slightly larger than in the case of Example 2, there is no problem in practical use. With the configuration of the present invention, not only the external airtightness but also the internal airtightness can be sufficiently secured.

Thereafter, hot water at 70 ° C. was circulated through the single cell, pure hydrogen was supplied as fuel, and air was supplied to the oxidant, and the power generation test and the stop operation were repeated. In the power generation test, the fuel utilization rate was 85%, the oxidant utilization rate was 55%, the current density was 0.3 A / cm ² , and the power generation time was 3 hours. After power generation, the cooling water inlet temperature was set to 30 ° C., and the battery was rapidly cooled. Then, after confirming that it became 30 degreeC after about 1 hour, the cooling water inlet temperature was heated up again to 70 degreeC, and the previous electric power generation test was restarted. Thus, the heat cycle test by repeating power generation and cooling was performed 200 times.

  After the above heat cycle test, an airtight test was performed again. As a result, helium gas equivalent to 50 kPa with respect to atmospheric pressure was filled from the piping connector of fuel, oxidant, and cooling water, and the internal pressure change was measured with a pressure sensor. The initial pressure of 50 kPa maintained a high pressure of 49.4 kPa even after 10 minutes, and it was found that almost no leakage to the outside occurred.

  Further, when 50 kPa of helium gas was filled only on the fuel side and the oxidizer side was opened to the atmosphere, the pressure on the fuel side maintained a high airtightness of 47.6 kPa after 10 minutes. The amount of internal leak hardly changed, and it was proved that the present invention is effective in suppressing internal leak.

  The fourth embodiment of the present invention has a configuration in which an insulating layer 719 is provided inside the gasket, and no insulating layer is provided on the contact surface between the separator and the electrolyte membrane. Graphite sheets 708 or 709 are bonded to both surfaces of the insulating layer 719. The configuration is shown in FIG.

  The insulating layer 719 in this example is obtained by joining a graphite gasket having a thickness of 60 μm to both surfaces of a polyimide resin sheet having a thickness of 50 μm. For bonding, an extremely thin epoxy resin was applied to the surface of the polyimide resin sheet, and was bonded by heat treatment at 100 ° C. The average thickness of the entire gasket sheet was 200 μm, and the variation was ± 10 μm. This was punched into the shape of FIG. 4 to produce a gasket.

As described above, the laminate of two gaskets and MEA (consisting of the anode 701, the electrolyte membrane 703, and the cathode 702) is combined with the separator 704 in which the fuel channel 705 is formed and the separator 706 in which the oxidant channel 707 is formed. The cell having the structure shown in FIG. 7 was assembled. The average tightening load of both separators was 7 kg / cm ³ . Further, two current collecting plates were arranged on the outside. Insulating resin plates such as PTFE (polytetrafluoroethylene) were inserted between the current collector plates and the end plates, and bolts were passed through the end plates at both ends and tightened with springs from the outside of the end plates.

  When the airtightness of such a single cell was measured, helium gas equivalent to 50 kPa with respect to atmospheric pressure was filled in the fuel and the oxidant, and the internal pressure change was measured with a pressure sensor. The initial pressure of 50 kPa maintained a high pressure of 49.5 kPa even after 10 minutes, and it was found that almost no leakage to the outside occurred.

  Further, when 50 kPa of helium gas was charged only on the fuel side and the oxidant side was opened to the atmosphere, the pressure on the fuel side maintained a high airtightness of 47.5 kPa after 10 minutes. Although the result is that the internal leak is slightly larger than in the case of Example 3, there is no problem in practical use. With the configuration of the present invention, not only the external airtightness but also the internal airtightness can be sufficiently secured.

Thereafter, hot water at 70 ° C. was circulated through the single cell, pure hydrogen was supplied as fuel, and air was supplied to the oxidant, and the power generation test and the stop operation were repeated. In the power generation test, the fuel utilization rate was 85%, the oxidant utilization rate was 55%, the current density was 0.3 A / cm ² , and the power generation time was 3 hours. After power generation, the cooling water inlet temperature was set to 30 ° C., and the battery was rapidly cooled. Then, after confirming that it became 30 degreeC after about 1 hour, the cooling water inlet temperature was heated up again to 70 degreeC, and the previous electric power generation test was restarted. Thus, the heat cycle test by repeating power generation and cooling was performed 200 times.

  After the above heat cycle test, an airtight test was performed again. As a result, helium gas equivalent to 50 kPa with respect to atmospheric pressure was filled from the piping connector of fuel, oxidant, and cooling water, and the internal pressure change was measured with a pressure sensor. The initial pressure of 50 kPa maintained a high pressure of 49.2 kPa even after 10 minutes, and it was found that almost no leakage to the outside occurred.

  Further, when 50 kPa of helium gas was charged only on the fuel side and the oxidant side was opened to the atmosphere, the pressure on the fuel side maintained high airtightness of 47.2 kPa after 10 minutes. The amount of internal leak hardly changed, and it was proved that the present invention is effective in suppressing internal leak.

  Next, an application example to a cell stack using the seal of the present invention is shown in FIG. A plurality of separators shown in FIG. 5 having the highest internal leak suppression effect were manufactured, and a polymer electrolyte fuel cell stack having a rated output of 1 kW was manufactured.

  By laminating the gasket 805 manufactured in Example 4, the MEA electrolyte membrane portion, and the gasket 805 in this order between the two single-cell separators 804, the leakage of fuel and oxidant is prevented. Yes.

  The cathode is composed of a catalyst layer and a gas diffusion layer. The catalyst layer is fixed to the surface of the electrolyte membrane 802. This may be applied to the gas diffusion layer. The catalyst layer is generally a mixture of a powder in which platinum fine particles are supported on graphite powder and an electrolyte binder, but other catalysts may be used. A gas diffusion layer is provided on the catalyst layer.

  The anode is also composed of a catalyst layer and a gas diffusion layer. The catalyst layer supports platinum fine particles on graphite powder, or supports fine particles made of platinum alloyed with a promoter such as lutite that has the function of oxidizing and removing carbon monoxide generated during the process of fuel oxidation. And further bonded with an electrolyte binder. Other catalysts may be used. After this catalyst layer is fixed to the other surface of the electrolyte membrane, a gas diffusion layer is provided on the catalyst layer. The cathode or anode catalyst layer may be applied to the gas diffusion layer.

  Moreover, the cooling cell 808 which has a cooling water flow path inside was inserted for every two cells. This is for removing heat generated during power generation.

A plurality of single cells 801 are connected in series, current collector plates 813 and 814 are installed at both ends, and are further tightened by an end plate 809 from the outside via an insulating plate 807. If the end plate is an insulating material, the insulating plate 807 can be omitted. Bolts 816, springs 817, and nuts 818 are used as fastening parts. The tightening load was adjusted so that the MEA electrode surface and the gasket of the present invention each had an average pressure of 3 to 7 kg / cm ² .

  Note that a graphite plate 803 is inserted between the current collector plate 813 and the end separator and between the current collector plate 814 and the end separator. This is to prevent the cooling water from directly contacting the current collector plates 813 and 814 because the cooling water flow path is formed on the separator.

  The fuel is supplied from a supply connector 810 provided on the left end plate 809, passes through each single cell 801, and is discharged on the opposite end plate 809 after the fuel is oxidized on the anode of the MEA. It is discharged from the connector 822. Here, a liquid organic fuel such as methanol can be used as the fuel. Furthermore, it is possible to use a liquid fuel such as a methanol aqueous solution.

  Similarly, the oxidizing agent is supplied from a supply-side connector 811 provided on the left end plate 809 shown in FIG. 8 and discharged from a discharge-side connector 823 of the opposite end plate 809. Air was supplied through piping from an air blower installed outside the battery.

  The cooling water is supplied from a supply-side connector 812 provided on the end plate 809 and discharged from a discharge-side connector 824 of the opposite end plate 809. The cooling water discharged from here is removed by cold water in a heat exchanger (not shown) and supplied again to the pipe connector 812. A pump was used to circulate the cooling water.

  A cell stack composed of 25 single cells 801 was manufactured with such a component structure. The cell stack was filled with helium gas equivalent to 50 kPa with respect to atmospheric pressure from the pipe connector of fuel, oxidant and cooling water, and the internal pressure change was measured by a pressure sensor. The initial pressure of 50 kPa maintained a high pressure of 49.1 kPa even after 10 minutes, and it was found that almost no leakage to the outside occurred.

  Further, when 50 kPa of helium gas was charged only on the fuel side and the oxidant side was opened to the atmosphere, the pressure on the fuel side maintained high airtightness of 47.0 kPa after 10 minutes. On the contrary, when the fuel side was opened to the atmosphere and helium gas of 50 kPa was filled on the oxidant side, the pressure on the oxidant side maintained high airtightness of 46.8 kPa after 10 minutes. In both tests, the cooling water piping was open to the atmosphere.

  Thereafter, hot water at 70 ° C. was circulated through the cell stack, the fuel was a mixed gas of 70% hydrogen and 30% carbon dioxide, air was supplied to the oxidant, and the power generation test and the stop operation were repeated. The current collector plate terminals 813 and 814 of the fuel cell are connected to an inverter 820 (which may be a DC-DC converter) via a cable 819. Here, AC power is supplied to the load 821.

In the power generation test of the fuel cell, the fuel utilization rate was 85%, the oxidant utilization rate was 55%, the current density was 0.3 A / cm ² , and the power generation time was 3 hours. After power generation, the cooling water inlet temperature was set to 30 ° C., and the battery was rapidly cooled. Thereafter, after confirming that the temperature became 30 ° C. after about 1 hour, the cooling water inlet temperature was again raised to 70 ° C., and the previous power generation test was resumed. Thus, the heat cycle test by repeating power generation and cooling was performed 200 times.

  After the above heat cycle test, an airtight test was performed again. As a result, helium gas equivalent to 50 kPa with respect to atmospheric pressure was filled from the pipe connector of fuel, oxidant, and cooling water, and the internal pressure change was measured with a pressure sensor. The initial pressure of 50 kPa maintained a high pressure of 48.9 kPa even after 10 minutes, and the amount of leakage to the outside hardly increased.

  Further, when 50 kPa of helium gas was charged only on the fuel side and the oxidizer side was opened to the atmosphere, the pressure on the fuel side maintained high airtightness of 46.7 kPa after 10 minutes. The amount of internal leak hardly changed, and it was proved that the present invention is effective in suppressing internal leak.

  When the sealing material of the present invention is used, a secondary effect that enables recycling is also obtained. For example, the gasket incorporated in the cell stack of FIG. 8 can be collected and carbon can be reused by pulverization, heat treatment, or the like. This is because carbon itself is chemically stable and does not substantially deteriorate. In addition to reuse as a fuel cell gasket, various mold materials having heat conductivity, heat transfer materials, and the like are conceivable.

  In the gasket using the conventional rubber material, the vicinity of the manifold 210 in FIG. 2A (periphery of the PP cross section), the flow path in the vicinity of the manifold 211 at the diagonal position, and the entire outer edge of the separator 204 are covered. Make a gasket as follows. And most of the central surface consisting of the flow path 205 and the rib 206 is in an open state so that the anode and the flow path face each other.

  Therefore, in the case of a flat gasket using a conventional rubber material, the opening and the manifold portion are punched out after the flat sheet is manufactured. The rubber material punched out in this way is subjected to a crosslinking treatment and is chemically changed, so that it is difficult to reuse. Also, it is difficult to reuse the cell stack used after use. Even when a convex gasket is formed on the separator, it is difficult to recover the gasket from the separator, and it is difficult to reuse it.

  According to the present invention, it is possible to recycle materials while solving the conventional technical problems, and it is effective in reducing the environmental load.

  The fifth embodiment according to the present invention has a configuration in which the adhesive layer 619 of the embodiment 3 is formed after interposing a resin reinforcing sheet previously bonded to the electrolyte membrane 603.

  The resin reinforcing sheet was formed at the interface between the adhesive layer 619 and the electrolyte membrane 603 in FIG. 6 (omitted in FIG. 6). The resin reinforcing sheet was a polyimide film (thickness: 50 μm) and was adhered with an extremely thin epoxy resin. The resin reinforcing sheet was bonded to both the anode surface and the cathode surface of MEA (membrane-electrode assembly).

With the addition of the resin reinforcing sheet, the thickness of the graphite gasket was changed from 150 μm (tolerance ± 30 μm) to 100 μm (tolerance ± 30 μm). The density was 1.7 g / cm ³ .

  An acrylic adhesive layer was applied to both surfaces of the graphite sheets 608 and 609 and adhered to a MEA resin reinforcing sheet to prepare an MEA with a graphite gasket.

This was inserted between the separator 604 formed in the fuel flow path 605 and the separator 606 formed with the oxidant flow path 607 to assemble a cell having the configuration shown in FIG. The average tightening load of both separators was 7 kg / cm ³ . Two current collector plates were disposed outside the separators 604 and 606, respectively. Insert an insulating resin plate such as PTFE (polytetrafluoroethylene) between these current collector plates and end plates, pass bolts through the end plates on both ends, and tighten them with springs from the outside of the end plates It was.

  When the airtightness of the entire single cell was measured by the same procedure as in Example 3, the initial pressure of 50 kPa maintained a high pressure of 49.8 kPa even after 10 minutes, and there was almost no leakage to the outside. all right.

  Further, when 50 kPa of helium gas was charged only on the fuel side and the oxidizer side was opened to the atmosphere, the pressure on the fuel side maintained high airtightness of 49.5 kPa after 10 minutes. The internal airtightness was better than in the case of Example 3. This suggests that the resin reinforcing membrane joined to the electrolyte membrane can effectively prevent the deformation of the gasket shown in FIG.

  101: anode, 102: cathode, 103: electrolyte membrane, 104: fuel side separator, 105: fuel flow path, 106: oxidant side separator, 107: oxidant flow path, 108: anode side gasket, 109: cathode side gasket 205: fuel flow path, 206: convex portion (rib), 210: fuel supply manifold, 211: fuel discharge manifold, 212: oxidant supply manifold, 213: oxidant discharge manifold, 214: cooling water supply manifold, 215: Cooling water discharge manifold, 304: fuel side separator, 305: fuel flow path, 306: convex portion (rib), 308: anode side gasket, 309: cathode side gasket, 310: cathode side separator, 317: gap, 408: gasket 410: Fuel supply manifold, 411: Fuel Outlet manifold, 412: Oxidant supply manifold, 413: Oxidant discharge manifold, 414: Cooling water supply manifold, 415: Cooling water discharge manifold, 418: Opening, 501: Anode, 502: Cathode, 503: Electrolyte membrane, 504 : Fuel side separator, 505: fuel flow path, 506: oxidant side separator, 507: oxidant flow path, 508: anode side gasket, 509: cathode side gasket, 519: insulating layer, 601: anode, 602: cathode, 603: Electrolyte membrane, 604: Fuel side separator, 605: Fuel channel, 606: Oxidant side separator, 607: Oxidant channel, 608: Anode side gasket, 609: Cathode side gasket, 619: Insulating layer, 701: Anode, 702: cathode, 703: electrolyte membrane, 704 Fuel side separator, 705: Fuel channel, 706: Oxidant side separator, 707: Oxidant channel, 708: Anode side gasket, 709: Cathode side gasket, 719: Insulating layer, 801: Single cell, 802: Membrane Electrode assembly (MEA), 803: flat plate component facing cooling water flow path, 804: separator for single cell, 805: gasket (seal), 807: insulating plate, 808: cooling cell, 809: end plate, 810: fuel Connector for piping, 811: Connector for oxidant piping, 812: Connector for cooling water piping, 813: Current collecting plate, 814: Current collecting plate, 816: Bolt, 817: Spring, 818: Nut, 819: External power line, 820 : Inverter, 821: Load installed outside, 822: Connector for fuel piping, 823: Connector for oxidant piping, 824: For cooling water piping connector.

Claims (9)

In a fuel cell gasket used as a seal between an electrolyte membrane and a separator, the gasket is formed of a molded body in which graphite particles and a resin binder are mixed, and the graphite particles and the resin binder are uniformly dispersed. configurations der is, fuel cell gaskets, characterized in that provided inside the insulating layer of the gasket.   2. The fuel cell gasket according to claim 1, wherein the graphite particles include expanded graphite particles.   The fuel cell gasket according to claim 1, wherein the resin binder contains a thermosetting resin.   The fuel cell according to any one of claims 1 to 3, wherein the gasket has a contact portion that contacts the separator of the fuel cell, and a convex portion is provided at a part of the contact portion. Gasket. A separator having an anode flow path for flowing fuel, a separator having a cathode flow path for supplying an oxidizing agent, and a membrane-electrode assembly composed of an anode / electrolyte membrane / cathode disposed between the two separators; A fuel cell comprising: a fuel cell gasket according to any one of claims 1 to 4 interposed between each separator and the electrolyte membrane. 6. The fuel cell according to claim 5 , wherein an insulating layer is provided at a contact portion between the gasket and each separator or the electrolyte membrane. The fuel cell according to claim 6 , wherein the insulating layer includes an adhesive resin layer. The fuel cell according to any one of claims 5 to 7 , wherein at least one of the separators having a contact portion that contacts the gasket has a convex portion at a part of the contact portion. A fuel cell system comprising a plurality of the fuel cells according to any one of claims 5 to 8 .

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