Sealant for fuel battery cell

Abstract

To provide a technology that can appropriately fix a separator and a sealant that sandwich a single cell of a fuel cell together using an adhesive.SOLUTION: A sealant 2 includes a seal base layer 4 and an adhesive layer 6 disposed on the surface of the seal base layer 4, the adhesive layer 6 includes a plurality of protrusions 8 protruding opposite a separator and having a height that decreases from a portion of the adhesive layer 6 toward the outer peripheral edge, and recesses 10 continuing between the plurality of protrusions 8 from the portion toward the outer peripheral edge. The plurality of protrusions 8 are configured to be crushed by the application of a load to fill the recesses 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a sealing material for cells of a fuel cell.

Background Art

[0002] For example, a cell of a polymer fuel cell includes a membrane electrode assembly (MEA) as a power generation unit, and gas diffusion layers are disposed on both sides thereof. A sealing portion for suppressing leakage of reaction gas (so-called cross leak) and electrical short circuit between catalyst electrodes is integrally formed on the outer periphery of the MEA (Membrane-Electrode Gas Diffusion Layer Assembly, hereinafter referred to as MEGA) on which the gas diffusion layer is disposed. The sealing material forming the sealing portion is sandwiched by a separator via an adhesive and integrated into the MEGA (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When joining a separator and a sealing material via an adhesive, air may remain (bubbles may be trapped) between the MEGA and the sealing material. The remaining air may reduce the joining strength and may impair the sealing performance.

[0005] This specification provides a technology for appropriately fixing a sealing material to a separator that sandwiches a single cell of a fuel cell using an adhesive.

Means for Solving the Problems

[0006] The technology disclosed in this specification provides a sealing material fixed to a separator that sandwiches a single cell of a fuel cell. The sealing material includes a seal base layer and an adhesive layer disposed on at least one surface of the seal base layer. The adhesive layer protrudes toward the separator and has a plurality of convex portions with a height that decreases from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer, and a concave portion that is continuous from the part toward the outer peripheral edge between the plurality of convex portions. The plurality of convex portions are configured to be crushed by the application of a load to fill the concave portion.

[0007] According to this sealing material, as the plurality of convex portions approach the outer peripheral edge from a part of the seal base layer, the space defined by the concave portions of the separator and the adhesive layer becomes smaller. Also, the plurality of convex portions are crushed by the load during joining to fill the concave portions. As a result, when joining the sealing material and the separator, the air intervening between the sealing material and the separator can be driven into a narrower space from the part toward the outer peripheral edge. As a result, the air between the sealing material and the separator can be discharged effectively in a certain direction, and the residual air can be suppressed or avoided. Also, by crushing the convex portions to fill the concave portions, the adhesive layer and the separator can be brought into close contact. Thereby, the joining strength and the sealing property with the separator can be ensured.

[0008] Also, according to this sealing material, in the past, the joining operation while suppressing the biting-in of air bubbles sometimes significantly reduced the productivity and workability, but such a joining operation can be avoided and efficient joining becomes possible.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0010] One embodiment of a sealing material for fixing a separator that sandwiches a single cell of a fuel cell disclosed in this specification includes a seal base layer and an adhesive layer disposed on at least one surface of the seal base layer. The adhesive layer protrudes toward the separator and has a plurality of convex portions having a height that decreases from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer, and a concave portion that is continuous from the part to the outer peripheral edge between the plurality of convex portions. The plurality of convex portions are configured to be crushed by the application of a load to fill the concave portion.

[0011] Another embodiment of the sealing material includes that the part of the adhesive layer is the central portion of the adhesive layer. By doing so, air is discharged from the central portion to the outer peripheral edge of the adhesive layer, so that the air is discharged evenly and effectively.

[0012] Another embodiment of the sealing material includes that at least some of the plurality of convex portions have two or more types of heights and are arranged so as to have a smaller height from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer. With such a plurality of convex portions, air can be effectively discharged during joining.

[0013] Another embodiment of the sealing material includes that at least some of the plurality of convex portions are arranged in a dot grid pattern in the adhesive layer. With such an arrangement, air is uniformly removed.

[0014] Another embodiment of the sealing material includes that at least one of the plurality of convex portions extends from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer and has a top surface that slopes so that the height gradually decreases from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer. With such convex portions, air can be effectively discharged during joining.

[0015] In this specification, the fuel cell is not particularly limited, but for example, a polymer electrolyte fuel cell (PEFC) may be suitable in some cases. In this specification, the fuel cell usually has at least a form of a laminate (stack) in which single cells are stacked. Note that the stacking form is not particularly limited. Also, in this specification, the fixing target of the sealing material is mainly the separator, but it may be one that fixes at least a part of the MEGA.

[0016] Hereinafter, a sealing material for fixing a separator that sandwiches a single cell of the fuel cell of the present disclosure will be described with appropriate reference to the drawings. FIG. 1 shows a sealing material 2 fixed to a separator that sandwiches the MEGA constituting a single cell of the PEFC.

[0017] As shown in FIG. 1(a), the sealing material 2 includes a seal base layer 4 and an adhesive layer 6. The seal base layer 4 has a shape necessary for securing a sealing material between the MEGA and the separator without particular limitation. The seal base layer 4 can be appropriately selected from various known resins that can be used for sealing, such as the outer periphery of the MEGA of the PEFC, without particular limitation.

[0018] The adhesive layer 6 is provided as a layer with a predetermined thickness on a part or the whole of at least one surface of the seal base layer 4. The adhesive layer 6 is provided on the surface facing at least one of the separators that sandwich the MEGA. Note that the adhesive layer 6 may be provided on the other surface of the seal base layer 4 for bonding with the other separator. Also, an adhesive layer may be provided on the other surface of the seal base layer 4. The adhesive layer 6 can be appropriately selected from various known adhesive resins and other adhesives that can be used for the seal part of the PEFC.

[0019] As shown in Fig. 1(a), the adhesive layer 6 has a plurality of convex portions 8 that protrude facing the separator. The plurality of convex portions 8 can have the same adhesive component as the adhesive layer 6. Further, the plurality of convex portions 8 are configured to have properties such as viscoelasticity to the extent that they can be crushed by the load from the separator side when joined to the separator or the like, and adjacent convex portions 8 can be continuous and fill the concave portions 10.

[0020] The planar form of the plurality of convex portions 8 is not particularly limited. The plurality of convex portions 8 may be, for example, convex portions having a rectangular cross-section perpendicular to the direction in which the convex portions 8 protrude, as shown in Figs. 1(a) and 1(b). Also, the planar forms of the plurality of convex portions 8 may be the same or different. The arrangement pattern of the plurality of convex portions 8 on the adhesive layer 6 is not particularly limited, but ultimately, when the convex portions 8 are crushed, adjacent convex portions 8 are continuous with each other and are set so as to fill the concave portions 10 described later and be in close contact with a joining object such as a separator. For example, as shown in Fig. 1(b), it may be arranged as a dot grid configured at regular intervals.

[0021] Here, as shown in Fig. 1(c), the plurality of convex portions 8 are arranged such that the height of the top surface 8b gradually decreases from the central portion 6a of the adhesive layer 6 toward the left and right outer peripheral edges 6b, 6c. The range of the height that the convex portion 8 can have is not particularly limited, but for example, it is about several μm to several tens of μm.

[0022] The gradually decreasing height of the plurality of convex portions 8 can be a stepwise decreasing height. For example, the convex portions 8 close to the central portion 6a and the convex portions 8 closest to the outer peripheral edges 6b, 6c can each have a flat top surface 8a with different heights. Also, for example, the gradually decreasing height can be a continuously decreasing height. As shown in Fig. 1(d), for example, the convex portions 8 close to the central portion 6a and the convex portions 8 closest to the outer peripheral edges 6b, 6c can each have an inclined top surface 8a that follows an inclined line having the height at the central portion 6a as the highest point and the height at the outer peripheral edges 6b, 6c as the lowest point.

[0023] As shown in FIGS. 1(a) to 1(d), the adhesive layer 6 has recesses 10. By forming a plurality of convex portions 8 spaced apart on the adhesive layer 6, the recesses 10 are simultaneously formed between the convex portions 8 arranged spaced apart from each other. The recesses 10 communicate with each other at least in part, and are configured to be open at the outer peripheral edge portion including the outer peripheral edges 6b and 6c of the adhesive layer 6 in plan view. The formation pattern of the recesses 10 depends on the arrangement pattern of the convex portions 8. The formation pattern of the recesses 10 is, for example, a lattice pattern formed around each convex portion 8 as shown in FIG. 1(b), communicates with each other, and is open at a plurality of locations on the outer peripheral edges 6b and 6c of the adhesive layer 6.

[0024] As shown in FIGS. 1(c) to 1(d), since the plurality of convex portions 8 are arranged such that their heights gradually decrease, the depth of the recesses 10 decreases. In other words, when pressure-bonded to the separator to be joined, the volume of the space defined by the separator and the recesses 10 is formed to gradually decrease.

[0025] Next, with reference to FIG. 2, the operation when joining the sealing material 2 including such an adhesive layer 6 to the separator 20 will be described.

[0026] As shown in FIG. 2, the separator 20 is placed on the adhesive layer 6 of the sealing material 2, and a predetermined load is applied from the separator 20 side. At this time, the separator 20 abuts on the highest convex portion 8 in the central portion 6a of the adhesive layer 6, presses and crushes the convex portion 8, and further abuts on, presses and crushes the lower convex portions 8 on the left and right. At the same time, the crushed convex portions 8 fill the recesses 10 between the adjacent convex portions 8 and continue with the convex portions 8. As a result, the air between the recesses 10 and the separator 20 is gradually pushed out in the direction toward the outer peripheral edges 6b and 6c of the adhesive layer 6.

[0027] When the loading on the separator 20 is completed, all of the plurality of convex portions 8 of the adhesive layer 6 are crushed, the concave portions 10 are filled, and the convex portions 8 are continuous. As a result, the newly formed adhesive layer 6' is brought into close contact with and joined to the separator 20. The air in the concave portions 10 is finally discharged to the outside at the outer peripheral edges 6b and 6c, which are the ends of the concave portions 10.

[0028] Through the above joining process, the air between the sealing material 2 and the separator 20 is discharged, and by being integrated with each other, the sealing performance and the joining strength are ensured.

[0029] As described above, according to the sealing material 2, since the sealing material 2 includes the adhesive layer 6 having a specific shape, the joining with the separator 20 can be realized without performing a complicated operation for degassing while ensuring sufficient sealing performance and joining strength.

[0030] In the above embodiment, the plurality of convex portions 8 are provided with a height that decreases from the central portion 6a of the adhesive layer 6 toward the left and right outer peripheral edges 6b and 6c in FIG. 1(b), but the present invention is not limited to this. It suffices that the height decreases from a part of the adhesive layer 6 toward the outer peripheral edge. For example, depending on the joining site of the separator 20 or the like, the height may be provided so as to decrease from one outer peripheral edge 6b of the adhesive layer 6 toward the opposite outer peripheral edge 6c. Further, in the above embodiment, the height is provided so as to decrease from the central portion 6a of the adhesive layer 6 toward the left and right outer peripheral edges 6b and 6c, but the height may be provided so as to decrease from the central portion 6a toward all the outer peripheral edges in the four directions in FIG. 1(b).

[0031] In the above embodiments, the plurality of convex portions 8 each have a top surface with a different height, and these plurality of convex portions 8 are arranged, but the present invention is not limited thereto. For example, as shown in Fig. 3(a), a single convex portion 18 may have an inclined top surface 18a that becomes lower from the central portion of the adhesive layer 6 toward the outer peripheral edge portions 6b and 6c. Also, as shown in Fig. 3(b), it may have an inclined top surface 18a that becomes lower from one outer peripheral edge portion 6b of the adhesive layer 6 toward the other outer peripheral edge portion 6c. By providing such convex portions 18, it is also possible to suppress or avoid the entrapment of air bubbles during joining by using the concave portions 10 formed between the convex portions 18 as air discharge ports.

Explanation of Reference Numerals

[0032] 2 Sealant material, 4 Sealant base layer, 6 Adhesive layer, 8, 18 Convex portion, 8a, 18a Top surface, 10 Concave portion, 20 Separator

Claims

1. A sealing material fixed to a separator that sandwiches a single cell of a fuel cell, comprising: a seal base layer; an adhesive layer disposed on at least one surface of the seal base layer; and having: the adhesive layer has a plurality of convex portions that protrude toward the separator and have a height that decreases from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer, and a concave portion that is continuous from the part toward the outer peripheral edge between the plurality of convex portions; the plurality of convex portions are configured to be crushed by the application of a load to fill the concave portion. A sealing material.

2. The sealing material according to claim 1, wherein the part of the seal base layer is the central part of the adhesive layer.

3. The sealing material according to claim 1 or 2, wherein at least some of the plurality of convex portions have two or more types of heights and are arranged so as to have a smaller height from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer.

4. The sealing material according to claim 3, wherein at least some of the plurality of convex portions are arranged in a dot grid pattern in the adhesive layer.

5. The sealing material according to claim 1 or 2, wherein at least one of the plurality of convex portions extends from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer and has a top surface that slopes so that the height gradually decreases from a part of the adhesive layer toward the outer peripheral edge of the adhesive layer.

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