CN214848709U - Sealing structure for bipolar plate of fuel cell - Google Patents

Abstract

The utility model provides a seal structure for fuel cell bipolar plate. The bipolar plate includes a first bipolar plate and a second bipolar plate, and the sealing structure is tiled between the first bipolar plate and the second bipolar plate. The sealing structure comprises a sealing gasket, and the sealing gasket is made of fluororubber. At least one surface of the sealing gasket is provided with convex peaks, and the convex peaks comprise grid-shaped convex peaks or at least two circles of annular convex peaks. When the bipolar plates are assembled into a stack, the gaskets are in a compressed state, at which time the height of the gaskets is reduced by 20% to 30% compared to when they are in an uncompressed state. The sealing structure of the high-temperature proton exchange membrane fuel cell bipolar plate is made of fluororubber, so that the air tightness and the high-temperature resistance of the sealing structure are excellent, and the long-time stable and reliable operation of a fuel cell stack can be ensured.

Description

Sealing structure for bipolar plate of fuel cell

Technical Field

The utility model relates to a seal structure, concretely relates to a seal structure for high temperature proton exchange membrane fuel cell bipolar plate belongs to fuel cell technical field.

Background

The high temperature proton exchange membrane fuel cell (HT-PEMFC) refers to a proton exchange membrane fuel cell with an operating temperature of 100 to 200 ℃. Compared with the traditional low-temperature proton exchange membrane fuel cell, the high-temperature proton exchange membrane fuel cell has the following advantages: (1) the working temperature is high, which is beneficial to improving the activity of the electrochemical reaction and accelerating the speed of the electrochemical reaction; (2) the carbon monoxide poisoning resistance of the catalyst is improved; (3) the method is favorable for gaseous drainage, and can simplify the water heat management system of the battery.

Bipolar plates and membrane electrodes, which are core components of fuel cells, have been the focus of current research, and gaskets, by comparison, are parts that are extremely easy to ignore. However, the sealing member is also an important component of the fuel cell, and the performance of the sealing member directly affects the power generation efficiency and the life of the fuel cell. The working environment of the high-temperature proton exchange membrane fuel cell requires that the sealing material has high air tightness, acid resistance, temperature resistance, low substance precipitation, excellent mechanical property and good economy.

Compared with the common rubber, the fluororubber has the following advantages because the fluororubber has a plurality of excellent properties: high temperature resistance, corrosion resistance, swelling resistance, aging resistance, compression set resistance, mechanical property, high vacuum resistance, flame resistance and low temperature resistance. The fluororubber is used as a sealing material of the high-temperature proton exchange membrane fuel cell and has good prospect.

SUMMERY OF THE UTILITY MODEL

The utility model discloses the technical problem that will solve is: the service life of a bipolar plate sealing gasket of a high-temperature proton exchange membrane fuel cell is prolonged.

In order to solve the above technical problem, the present invention provides a sealing structure for a bipolar plate of a fuel cell, the bipolar plate comprises a first bipolar plate and a second bipolar plate, and the sealing structure is tiled between the first bipolar plate and the second bipolar plate;

the sealing structure comprises a sealing gasket, wherein the sealing gasket is made of fluororubber;

at least one surface of the sealing gasket is provided with convex peaks, and the convex peaks comprise latticed convex peaks or at least two circles of annular convex peaks;

the sealing pad is configured to: when the bipolar plates are assembled into a stack, the gaskets are in a compressed state, at which time the height of the gaskets is reduced by 20% to 30% compared to when they are in an uncompressed state.

In some embodiments, the gasket is a flat-bottomed, double-peak gasket having a height that is reduced by 20% to 25% when the double-peak gasket is in a compressed state as compared to when the double-peak gasket is in an uncompressed state.

In some embodiments, the two circles of annular peaks of the double-peak sealing gasket are parallel, and the top surfaces of the annular peaks are cambered surfaces.

In some embodiments, the first bipolar plate is provided with a first mounting groove for receiving the double-peak gasket, the width of the first mounting groove being greater than the width of the double-peak gasket in the non-compressed state.

In some embodiments, the bottom surface of the double-peak sealing gasket is in contact with the bottom surface of the first mounting groove, and two side surfaces of the double-peak sealing gasket are respectively spaced from the corresponding two side groove walls of the first mounting groove by about 0.1 mm.

In some embodiments, the second bipolar plate has a flat surface and is attached with a sealant layer.

In some embodiments, the sealant layer has a thickness of less than 0.025 millimeters.

In some embodiments, the second bipolar plate is provided with a second mounting groove, and the second mounting groove is opposite to the first mounting groove; flat annular supporting pad is settled in the second mounting groove, and two surfaces of supporting pad all level and smooth, and the supporting pad is made by viton.

In some embodiments, the sealing gasket is a grid sealing gasket, the bottom surface of the grid sealing gasket is flat, and the top of the grid sealing gasket is provided with grid-shaped convex peaks; the height of the grid gasket in the compressed state is reduced by 24 to 26 percent compared with the height of the grid gasket in the non-compressed state.

In some embodiments, the top surface of the grid-like peaks is planar.

The utility model has the advantages that: the sealing structure of the high-temperature proton exchange membrane fuel cell bipolar plate is made of fluororubber, so that the air tightness and the high-temperature resistance of the sealing structure are excellent, and the long-time stable and reliable operation of a fuel cell stack can be ensured.

Drawings

Fig. 1 is a schematic cross-sectional view of a bipolar plate sealing structure of a fuel cell in embodiment 1 of the present invention.

Fig. 2 is a schematic view of the overall structure of the gasket in embodiment 1 of the present invention.

Fig. 3 is a schematic cross-sectional view of a gasket according to embodiment 1 of the present invention.

Fig. 4 is a schematic cross-sectional view of a fuel cell bipolar plate sealing structure in embodiment 2 of the present invention.

Fig. 5 is a schematic view of an operating state of the bipolar plate sealing structure of the fuel cell according to embodiment 2 of the present invention.

Fig. 6 is a schematic cross-sectional view of a fuel cell bipolar plate sealing structure according to embodiment 3 of the present invention.

Fig. 7 is a schematic view of the overall structure of the gasket according to embodiment 3 of the present invention.

Fig. 8 is a schematic bottom view of a gasket according to embodiment 3 of the present invention.

The reference numerals in the above figures are as follows:

110 bipolar plate

111 groove

120 bipolar plate

130 bimodal gasket

131 substrate

132 convex peak

133 peak

140 sealant layer

150 membrane electrode frame

160 film electrode

210 bipolar plate

211 groove

220 bipolar plate

221 groove

230 double peak sealing gasket

231 base

232 peak

233 convex peak

240 support pad

250 membrane electrode frame

260 film electrode

310 bipolar plate

320 bipolar plate

330 grid gasket

331 peak

340 sealant layer

350 membrane electrode frame

360 film electrode

Detailed Description

As used in this specification and the appended claims, the terms "first," "second," and the like do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms "a" or "an," and the like, do not denote a limitation of quantity, but rather denote the presence of at least one. In the description of this patent, unless otherwise indicated, "a plurality" means two or more. The word "comprising" or "having", and the like, means that the element or item appearing before "comprises" or "having" covers the element or item listed after "comprising" or "having" and its equivalent, but does not exclude other elements or items.

In the description of this patent, it is to be understood that the terms "front", "back", "upper", "lower", "left", "right", "horizontal", "lateral", "longitudinal", "top", "bottom", "inner", "outer", "clockwise", "axial", "radial", "circumferential", and the like, indicate orientations and positional relationships that are based on the orientation or positional relationship illustrated in the drawings, are used for convenience in describing the patent and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the patent.

The present invention may be used in alternative or combined combinations between different embodiments, and therefore the present invention is also to be construed as encompassing all possible combinations of the same and/or different embodiments described. Thus, if one embodiment includes feature A, B, C and another embodiment includes feature B, D, the invention should also be construed as including embodiments that include all other possible combinations of one or more of A, B, C, D, even though such embodiments may not be explicitly recited in the following text.

The Membrane Electrode Assembly (MEA) is the most core component of a proton exchange Membrane fuel cell, is a multiphase substance transmission and electrochemical reaction site for energy conversion, relates to a three-phase interface reaction and a complex mass and heat transfer process, and directly determines the performance, the service life and the cost of the proton exchange Membrane fuel cell. The membrane electrode mainly comprises a gas diffusion layer, a catalytic layer and a proton exchange membrane, wherein the gas diffusion layer usually comprises carbon paper/carbon cloth and a microporous layer loaded on the carbon paper/carbon cloth. The MEA composed of the cathode gas diffusion layer, the cathode catalytic layer, the proton exchange membrane, the anode catalytic layer, and the anode gas diffusion layer is generally referred to as a "five-in-one" MEA, and the microporous layer is counted as the assembly referred to as a "seven-in-one" MEA. The MEA is used as the most core component of the fuel cell, and has very important significance in improving the performance and the service life of the fuel cell and reducing the cost.

In a stack of proton exchange membrane fuel cells, the membrane electrodes are confined within a membrane electrode frame, which are co-located between two bipolar plates. Wherein, the membrane electrode frame is positioned at the position close to the edge of the bipolar plate, and the membrane electrode is positioned at the middle position of the bipolar plate. The bipolar plate and the membrane electrode frame are sealed by a sealing structure, so that liquid and gas are prevented from leaking. Because the membrane electrode is an all-in-one laminated structure, the diffusion layer therein must be subjected to a proper packaging force to maintain a good working condition of the membrane electrode. The contact resistance between the bipolar plates of the fuel cell decreases as the thickness of the diffusion layer decreases, i.e., the contact resistance decreases as the encapsulation force increases, the diffusion layer and the like are pressed thinner. Meanwhile, the diffusion layer is generally a porous loose medium, and when the diffusion layer is extruded and the thickness of the diffusion layer is reduced, the porosity is reduced, the permeability of hydrogen and oxygen is reduced, and the internal electrochemical reaction rate is influenced.

For pem fuel cells, there is an optimum packing force at which the diffusion layer contact resistance and air permeability are both optimum. The sealing structure is designed based on the optimal packaging force, and the sealing structure still has longer service life on the premise of ensuring the optimal performance of the battery. The packaging force of the stack is generally about 200-600 kg according to the size of the stack. The electric pile of the high-temperature proton exchange membrane fuel cell adopts about 500-600 kilograms of packaging force, and the compression ratio of a membrane electrode in the thickness direction is 11% -12%; namely: the thickness of the membrane electrode when the membrane electrode is arranged in the stack and pressed is reduced by 11 to 12 percent compared with the free thickness when the membrane electrode is not pressed. When the bipolar plate is assembled, the seal structure is also in a compressed state, at which time the height of the seal structure is reduced by 20% to 30% compared to its uncompressed state. Under a certain packaging force, the compression amount of the sealing structure is related to the elastic modulus, the geometric shape and other factors of the material.

The pile working temperature of the high-temperature proton exchange membrane fuel cell is 100-200 ℃, and a sealing structure made of common rubber can be rapidly aged and deteriorated at the working temperature. The fluororubber with better high temperature resistance and aging resistance is an ideal substitute and is used for manufacturing the sealing structure of the high-temperature proton exchange membrane fuel cell. The elasticity modulus of the fluororubber is different from that of the common rubber, and the sealing structure can work in the high-temperature proton exchange membrane fuel cell efficiently and durably by adopting a shape structure design scheme different from that of the prior art.

The fluororubber used in the present invention may be selected from (but not limited to) one of the following: fluororubbers 23, 26, 246, TP, metafluoroether rubber, perfluoroether rubber, fluorosilicone rubber, and the like. The fluororubber 23 (commonly called No. 1 gum in China) is a vinylidene fluoride and chlorotrifluoroethylene copolymer; the fluororubber 26 (commonly called No. 2 rubber in China) is a vinylidene fluoride and hexafluoropropylene copolymer; the fluororubber 246 (commonly called No. 3 rubber in China) is a terpolymer of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene; the fluororubber TP (commonly called tetrapropylene rubber in China) is a copolymer of tetrafluoroethylene and hydrocarbon propylene; the vinylidene fluoride ether rubber is a quadripolymer of vinylidene fluoride, tetrafluoroethylene, perfluoromethyl vinyl ether and a vulcanization point monomer; the perfluoroether rubber (also called perfluororubber) is a terpolymer of perfluoroether, tetrafluoroethylene and perfluoroolefin ether.

The utility model relates to a seal structure for high temperature proton exchange membrane fuel cell bipolar plate. For simplicity, this is illustrated by a "sandwich" structure of two bipolar plates sandwiching a membrane electrode. A number of such sets of "sandwich" structures are repeatedly stacked to form the actual stack. The sandwich structure comprises a first bipolar plate and a second bipolar plate, the sealing structures are paved between the first bipolar plate and the second bipolar plate, and each group of sealing structures consists of a sealing gasket and a sealing accessory.

The gasket is made of a fluoroelastomer, which may be in various forms. In one embodiment, the bottom surface of the base of the gasket is flat and two rings of annular ridges are attached to the top of the base, and this gasket can be referred to as a double-peak gasket. The top of the annular crest may be horizontal, circular arc, etc., and is preferably circular arc. In one embodiment, the two rings of annular peaks are parallel to each other. If there is only one turn of the peak, neither airtightness nor durability is satisfactory.

In order to prevent the double-peak sealing gasket from sliding between the two bipolar plates to influence the sealing, a circle of first mounting groove is formed in the first bipolar plate, the double-peak sealing gasket is mounted in the mounting groove, the bottom surface of the double-peak sealing gasket is in contact with the groove bottom of the first mounting groove, and two circles of annular convex peaks face to the other bipolar plate. When the double-peak sealing gasket is in a compressed state, the overall height (base and convex peak) of the double-peak sealing gasket is reduced by 20-25% compared with that of the double-peak sealing gasket in a non-compressed state.

The width of the first mounting groove is greater than the width of the sealing gasket in a non-compression state, and preferably, the distance between the two sides of the first mounting groove and the wall of the mounting groove is 0.1 mm respectively when the sealing gasket is in the non-compression state. Because the double-peak gasket is resilient, it can be installed into the mounting groove even if it is slightly wider than the width of the mounting groove. Therefore, the 0.1 mm distance is not only for the purpose of facilitating the insertion of the double-peak gasket into the installation groove, but also for the purpose of facilitating the deformation of the gasket in the height direction (compression in the height direction and simultaneous expansion in the width direction). A 0.1 millimeter spacing is more or less the size of the substrate expansion of the gasket when it is compressed by the bipolar plate. If the spacing is greater than 0.1 mm, the bimodal gasket may still slip during compression, affecting the sealing performance.

The top of the annular hump is in contact with one face of the membrane electrode frame, and a sealing material is also required between the other face of the membrane electrode frame and the second bipolar plate. In one embodiment, a layer of sealant is applied to the surface of the second bipolar plate to a thickness of less than 0.025 mm. The mould electrode frame is attached to the layer of sealant, so that sealing is realized. The sealant layer has two disadvantages: firstly, the durability of the sealant is poor under the high-temperature use environment; and secondly, the sealant is firmly adhered to the surface of the bipolar plate and is difficult to remove. When the sealant is aged and damaged, the bipolar plate needs to be integrally replaced, and the cost is high.

In another embodiment, a second mounting groove is formed in the second bipolar plate, opposite to the first mounting groove in the first bipolar plate. Flat annular fluororubber supporting pad is arranged in the second mounting groove, and two surfaces of the supporting pad are flat. Thus, one surface of the mould electrode frame is contacted with the supporting pad, and the other surface is contacted with the tops of the two circles of annular convex peaks. When the two bipolar plates are pressed, the supporting pads and the sealing gaskets are deformed, so that the paired electrode frame and the bipolar plates are sealed.

In another embodiment, the gasket is a grid gasket, and the material is also fluororubber. The bottom surface of the grid sealing gasket is flat and is attached to the surface of the first bipolar plate, and the first bipolar plate in the scheme does not need to be grooved. The other surface of the sealing gasket is provided with latticed convex peaks. The sealing gasket is obtained by cutting, digging and trimming a complete section bar, and has low manufacturing cost but no poor sealing performance and durability. The surface of the second bipolar plate is flat, a layer of sealant is applied on the second bipolar plate, and the thickness of the sealant layer is less than 0.025 mm. The top surfaces of the grid-like peaks are flat so that the molded electrode frame is sandwiched between the grid gasket and the sealant layer to effect sealing. The height of the grid sealing gasket in a compressed state is reduced by 24-26% compared with the height of the grid sealing gasket in a non-compressed state.

The embodiments are further described below with reference to the accompanying drawings.

Example 1

Fig. 1 to 3 show schematic diagrams of a bipolar plate for a fuel cell and a sealing structure thereof according to the present embodiment. The bipolar plate 110 and the bipolar plate 120 sandwich the membrane electrode frame 150 and the membrane electrode 160 therebetween. The thickness of the bipolar plate 110 is 1.35 mm, the thickness of the main body of the bipolar plate 120 is 1.68 mm, and the thickness of the membrane electrode frame 150 is 0.05 mm. The bipolar plate 120 is provided with a limit step having a depth of 0.33 mm, on which the membrane electrode 160 is located. The thickness of the membrane electrode 160 before compression is 0.85-0.9 mm, the thickness after compression is 0.75 mm, and the compression rate is 11-12%.

The bipolar plate 110 has a groove 111 with a width of 3.2 mm and a depth of 0.32 mm. The base 131 of the double-peak gasket 130 is placed in the groove 111, and the width of the base 131 is about 3 mm, so that it is about 0.1 mm from both side walls of the groove 111, respectively. As shown in FIG. 2, the upper portion of the dual peak gasket 130 has two parallel gasket beads: a peak 132 and a peak 133. Wherein the hump 132 is located at the outer ring and the hump 133 is located at the inner ring, as shown in the cross-sectional view of fig. 3. The overall height of the bimodal seal 130 from the bottom surface to the top of the peaks was 0.95 mm.

The bottom surface of the bipolar plate 120 is formed with a sealant layer 140 by screen printing, and the thickness is 0.025 mm. After the bipolar plate 110 and the bipolar plate 120 are pressed, the peaks 132 and 133 are pressed and deformed, and the tops of the peaks are pressed against the membrane electrode frame 150, so that the membrane electrode frame 150 is slightly deformed, because the sealant layer 140 is present, it is ensured that both surfaces of the membrane electrode frame 150 are sealed, and the substance in the membrane electrode 160 does not leak outwards.

Example 2

Fig. 4 and 5 are schematic diagrams of a bipolar plate and a sealing structure thereof for a fuel cell according to the present embodiment. The membrane electrode frame 250 and the membrane electrode 260 are clamped between the bipolar plate 210 and the bipolar plate 220, the thickness of the bipolar plate 210 and the thickness of the bipolar plate 220 are both 1.68 mm, and the thickness of the membrane electrode frame 250 is 0.05 mm. The bipolar plate 210 and the bipolar plate 220 are respectively provided with a limit step, the two limit steps are opposite, the depth of each limit step is 0.33 mm, and the membrane electrode 260 is positioned between the two limit steps. The thickness of the membrane electrode 260 before compression is 0.85-0.9 mm, the thickness after compression is 0.75 mm, and the compression rate is 11-12%.

The bipolar plate 210 has a groove 211 with a width of 3.2 mm and a depth of 0.65 mm. The base 231 of the bimodal seal 230 is placed in the recess 211 as shown in figure 5. The width of the base 231 is about 3 mm so that it is about 0.1 mm from both side walls of the recess 211, respectively. The upper portion of the bimodal gasket 230 has two parallel gasket peaks: peaks 232 and 233. Wherein, the convex peak 232 is positioned at the outer ring, and the convex peak 233 is positioned at the inner ring. The overall height of the bimodal seal 230 from the bottom surface to the top of the peaks was 0.95 mm. In this embodiment, the shape, structure, size and material of the dual-peak gasket 230 are the same as or similar to the dual-peak gasket 130 of embodiment 1.

This example differs from example 2 in that: the support pad 240 is used instead of the sealant layer 140.

The bipolar plate 220 has a groove 221 with a width of 3.2 mm and a depth of 0.65 mm, and the groove 221 is opposite to the groove 211. The support pad 240 is disposed in the recess 221, and the support pad 240 has a flat ring shape having a height of 0.65 mm and a width of 3 mm such that it is spaced apart from both side walls of the recess 221 by about 0.1 mm, respectively. The bimodal gasket 230 is used in cooperation with a support pad 240, with a membrane electrode frame 250 sandwiched therebetween. When pressure is applied to the bipolar plate 210 and the bipolar plate 220, the ridges 232 and 233 are deformed in a pressing manner, and their tops are pressed against the membrane electrode frame 250. The height of the support pad 240 is the same as the depth of the groove 221, and the two are flush with each other, so that the membrane electrode frame 250 and the support pad 240 are pressed only slightly, and the membrane electrode frame 250 is not crushed. Both surfaces of the membrane electrode frame 250 are sealed and the substance in the membrane electrode 260 does not leak to the outside.

Finite element simulation is performed on the double-peak sealing gasket 230 and the supporting pad 240, and it is measured that the main deformation of the sealing structure of the design scheme is provided by the double-peak sealing gasket 230, the deformation of the two convex peak positions of the double-peak sealing gasket 230 is the largest, and the deformation of the supporting pad 240 is lower, as shown in fig. 5. The contact pressure of the upper plane of the supporting pad 240 is 1.85MPa, the contact width is 2.5 mm, the contact pressure of the lower plane is 3.04MPa, and the contact width is 2.04 mm, so that the sealing requirement is met. The upper part of the double-peak sealing gasket 230 has the contact pressure of 5.05MPa and the contact width of 0.75 mm, the lower plane has the contact pressure of 2.1MPa and the contact width of 2.8 mm, and the sealing requirement is met.

Example 3

Fig. 6 to 8 show schematic diagrams of a bipolar plate for a fuel cell and a sealing structure thereof according to the present embodiment. The membrane electrode frame 350 and the membrane electrode 360 are clamped between the bipolar plate 310 and the bipolar plate 320, the thickness of the bipolar plate 310 is 1.39 mm, the thickness of the bipolar plate 320 is 1.63 mm, and the thickness of the membrane electrode frame 350 is 0.05 mm. The first surface of the bipolar plate 310 is flat and the bottom surface of the mesh gasket 330 is flat and in contact with the first surface of the bipolar plate 310. The width of the mesh gasket 330 is 6 mm. The top of the mesh gasket 330 has a grid of peaks 331 with their top surfaces flush against one face of the membrane electrode frame 350. The bipolar plate 320 is provided with a stop step having a depth of 0.33 mm where the membrane electrode 360 is located. The thickness of the membrane electrode 360 before compression is 0.85-0.9 mm, the thickness after compression is 0.75 mm, and the compression rate is 11% -12%.

The bottom surface of the bipolar plate 320 is screen printed with a sealant layer 340 having a thickness of 0.025 mm. After the bipolar plate 310 and the bipolar plate 320 are pressed, the convex peaks 331 of the grid gasket 330 are pressed and deformed, and the tops of the convex peaks are pressed against the membrane electrode frame 350, so that the membrane electrode frame 350 is slightly deformed, because the sealant layer 340 ensures that both surfaces of the membrane electrode frame 350 are sealed, and the substances in the membrane electrode 360 do not leak outwards.

The foregoing has described in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be devised by those skilled in the art in light of the teachings of the present invention without undue experimentation. Therefore, the technical solutions that can be obtained by a person skilled in the art through logic analysis, reasoning or limited experiments based on the prior art according to the concepts of the present invention should be within the scope of protection defined by the claims.

Claims (10)

1. A seal structure for a fuel cell bipolar plate, the bipolar plate comprising a first bipolar plate and a second bipolar plate, the seal structure lying between the first bipolar plate and the second bipolar plate,

the sealing structure comprises a sealing gasket, and the sealing gasket is made of fluororubber;

at least one surface of the sealing gasket is provided with convex peaks, and the convex peaks comprise latticed convex peaks or at least two circles of annular convex peaks;

the sealing pad is configured to: when the bipolar plates are assembled into a stack, the gaskets are in a compressed state, at which time the height of the gaskets is reduced by 20% to 30% compared to when they are in an uncompressed state.

2. A seal structure for a bipolar plate of a fuel cell according to claim 1, wherein said seal gasket is a double-peak seal gasket having a flat bottom surface, and the height of said double-peak seal gasket in a compressed state is reduced by 20% to 25% from that in a non-compressed state.

3. A sealing structure for a bipolar plate of a fuel cell according to claim 2, wherein the two circles of annular peaks of the double-peak sealing gasket are parallel, and the top surfaces of the annular peaks are cambered surfaces.

4. A seal structure for a fuel cell bipolar plate according to claim 2, wherein said first bipolar plate is provided with a first fitting groove for fitting said bimodal seal gasket, said first fitting groove having a width larger than that of said bimodal seal gasket in a non-compressed state.

5. A sealing structure for a bipolar plate of a fuel cell according to claim 4, wherein the bottom surface of the double-peak sealing gasket is in contact with the groove bottom of the first mounting groove, and both side surfaces of the double-peak sealing gasket are spaced from the corresponding both side groove walls of the first mounting groove by about 0.1 mm, respectively.

6. A seal structure for a fuel cell bipolar plate according to claim 4, wherein said second bipolar plate has a flat surface and is attached with a sealant layer.

7. A seal structure for a fuel cell bipolar plate according to claim 6, wherein said sealant layer has a thickness of less than 0.025 mm.

8. A sealing structure for a fuel cell bipolar plate according to claim 4, wherein said second bipolar plate is provided with a second mounting groove, said second mounting groove being opposed to said first mounting groove; flat annular supporting pad is installed in the second mounting groove, two surfaces of supporting pad are all level and smooth, the supporting pad is made by viton.

9. A sealing structure for a bipolar plate of a fuel cell according to claim 1, wherein said sealing gasket is a mesh sealing gasket having a flat bottom surface and having mesh-like peaks at its top; the height of the grid gasket in the compressed state is reduced by 24-26% compared with the height of the grid gasket in the non-compressed state.

10. A seal structure for a fuel cell bipolar plate according to claim 9, wherein the top surfaces of said lattice-like peaks are flat.

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