WO2005081343A1 - Solid polymer electrolyte membrane and separator both for fuel cell - Google Patents

Abstract

A solid polymer electrolyte membrane (20) for fuel cells comprises a body section (21) forming a region interposed between a pair of gas diffusion layers (31, 32) functioning as electrodes, a projecting portion (22) projecting from the outer peripheries of the gas diffusion layers (31, 32), and a frame-shaped reinforcing section (23) formed by so applying a reinforcing material (24) to the projecting portion (22) as to cover the outer peripheries of the gas diffusion layers (31, 32). The reinforcing section (23) imparts a shape-holing force to prevent the body section (21) from curling to the body section (21). The reinforcing section (23) also serves as a sealing member (25) between separators (41, 42).

Description

 Specification

 Solid polymer electrolyte membrane and separator for fuel cell

 Technical field

 The present invention relates to a solid polymer electrolyte membrane and a separator for a fuel cell.

 Background art

 [0002] In a single cell of a solid polymer electrolyte fuel cell disclosed in Japanese Patent Application Laid-Open No. 7-249417, a solid polymer electrolyte membrane as a cation exchange membrane is sandwiched between a pair of gas diffusion layers functioning as electrodes. , And the outside thereof is sandwiched between a pair of separators. The solid polymer electrolyte membrane is formed as a thin film in order to suppress a voltage drop due to its resistance. Since the solid polymer electrolyte membrane, which is a thin film, has little force to maintain its shape, it is easily deformed under the influence of temperature and humidity, and has poor handling properties.

 [0003] Therefore, the outer edge of the solid polymer electrolyte membrane is sandwiched between a pair of frames to form an electrolyte membrane member. By using a plurality of parts as a whole, the solid-state polymer electrolyte membrane has improved nodling properties.

 Disclosure of the invention

 [0004] However, the handling properties of the solid polymer electrolyte membrane alone are not considered, and the deformation of the solid polymer electrolyte membrane alone cannot be sufficiently suppressed.

[0005] An object of the present invention is to provide a solid polymer electrolyte membrane and a separator for a fuel cell, which can simplify the production of the fuel cell.

[0006] More specifically, an object of the present invention is to provide a solid fuel cell for a fuel cell capable of improving the handleability of a single fuel cell, thereby simplifying the production of the fuel cell. It is to provide a secondary electrolyte membrane.

[0007] Another object of the present invention is to provide a fuel cell capable of simplifying the production of a fuel cell by applying a solid polymer electrolyte membrane having a good handling property as a single substance. It is to provide a separator for a pond.

[0008] Still other objects, features and characteristics of the present invention will become apparent by referring to the following description and preferred embodiments illustrated in the accompanying drawings. Brief Description of Drawings

 FIG. 1 is a cross-sectional view showing a single cell of a polymer electrolyte fuel cell to which a solid polymer electrolyte membrane and a separator for a fuel cell according to an embodiment of the present invention are applied.

 [FIG. 2] FIG. 2A is a perspective view showing a solid polymer electrolyte membrane on which a reinforcing portion having a frame shape is formed, and FIG. 2B is a sectional view taken along line 2B-2B in FIG. 2A.

 FIG. 3A and FIG. 3B are diagrams conceptually showing a method of applying a reinforcing material in a frame shape.

 BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

 A fuel cell is used in the form of a fuel cell stack in which a number of single cells 10 are stacked, for example, as a drive source of an automobile.

 [0012] The single cell 10 is a battery that can obtain electricity in the process of obtaining water by reacting hydrogen and oxygen using the reverse principle of electrolysis of water. The single cell 10 has a solid polymer electrolyte membrane 20 as a cation exchange membrane, a pair of gas diffusion layers 31 and 32 functioning as electrodes, and a pair of separators 41 and 42. The single cell 10 is configured such that the solid polymer electrolyte membrane 20 is sandwiched between a pair of gas diffusion layers 31 and 32, and the outside thereof is sandwiched between a pair of separators 41 and 42. In the separator 41 on the gas diffusion layer 31 side, a flow groove 43 for flowing cooling water and a flow groove 44 for flowing fuel gas (hydrogen) are formed. In the separator 42 on the gas diffusion layer 32 side, a flow channel 45 for flowing cooling water and a flow channel 46 for flowing oxidizing gas (air) are formed. The shape and arrangement of the channel grooves 43-46 need to consider gas diffusivity, pressure loss, discharge of generated water, cooling performance, etc., and have a fine and complicated configuration.

 [0013] The solid polymer electrolyte membrane 20 is a polymer membrane having a function of moving hydrogen ions. The solid polymer electrolyte membrane 20 is formed in a thin film (for example, about several tens to 100 m) in order to suppress a voltage drop due to its resistance.

[0014] The formed solid polymer electrolyte membrane 20 is usually stored or stored in a state of being wound around a core in a roll shape, and is used while being sequentially fed out when manufacturing a fuel cell. . As shown in FIGS. 2A and 2B, the solid polymer electrolyte membrane 20 includes a main body 21 forming a region interposed between the pair of gas diffusion layers 31 and 32, and a gas diffusion layer 31, A protruding portion 22 protruding from the outer peripheral edge of the protruding portion 32 and a reinforcing portion 23 having a frame shape formed by applying a reinforcing material to the protruding portion 22 so as to surround the outer peripheral edge of the gas diffusion layers 31 and 32. In. The reinforcing portions 23 are formed on both surfaces (upper and lower surfaces in FIG. 2B) of the protruding portion 22 and have a rectangular cross section. When assembling the single cell 10, the main body 21 is sandwiched between the pair of gas diffusion layers 31 and 32, and the reinforcing portion 23 protrudes from the gas diffusion layers 31 and 32 and is disposed between the pair of separators 41 and 42. (See Figure 1). As will be described later, in the present embodiment, the reinforcing portion 23 has a sealing function.

 The reinforcing portion 23 gives the main body portion 21 a shape retaining force for preventing the main body portion 21 from rolling. That is, while the solid polymer electrolyte membrane 20 is stored in a rolled state, the main body 21 has a curl. Further, the solid polymer electrolyte membrane 20, which is a thin film, has little force to maintain its shape, and is easily deformed under the influence of temperature and humidity. On the other hand, since the reinforcing portion 23 has a frame shape, it can withstand the curling force acting on the main body portion 21 due to the curl and the deformation force due to the influence of temperature and humidity. The force for holding the flat shape, that is, the shape holding force is strong. As a result of the reinforcing portion 23 applying the shape holding force to the main body portion 21, the main body portion 21 is prevented from being rounded or deformed.

 [0017] The reinforcing portion 23 having a frame shape is formed by applying a reinforcing material to the protruding portion 22.

 Here, as the reinforcing material, an appropriate material can be selected as long as the reinforcing portion 23 can impart shape retaining force to the main body portion 21. In the present embodiment, since the reinforcing portion 23 is also intended to have a sealing function, the reinforcing material is selected in consideration of the sealing property. Silicon rubber (having a Shore hardness of 25 or more) or fluorine rubber can be suitably used as the reinforcing material in terms of both imparting shape retention and providing a sealing function. It is also possible to use a two-component curing type curing agent having quick drying properties.

 FIGS. 3A and 3B are diagrams conceptually showing a method of applying the reinforcing material 24 in a frame shape.

In order to apply the reinforcing material 24 in a frame shape, a masking method (FIG. 3A), Printing method (Fig. 3B) can be adopted. 3A and 3B show, for convenience of explanation, a form in which the reinforcing material 24 is applied to a cut piece obtained by cutting the solid polymer electrolyte membrane 20 into a size used for the single cell 10. However, since the solid polymer electrolyte membrane 20 before the formation of the reinforcing portion 23 has poor handling properties, in the actual manufacturing process, after the reinforcing material 24 is applied in a lattice shape, the size used for the single cell 10 is reduced. Then, it is cut into a lattice so that a plurality of cut pieces provided with the reinforcing portions 23 can be obtained at a time. This is because it is preferable to increase the efficiency of the application work of the reinforcing material 24.

Referring to FIG. 3A, in the masking method, a protective film 50 previously attached to both surfaces of solid polymer electrolyte membrane 20 can be used as a masking material. FIG. 3A shows a state in which only the peripheral portion of the protective film 50 is removed, and the protruding portion 22 is exposed while the main body 21 is masked. The reinforcing material 24 such as silicon rubber is applied to the exposed portion while moving the nozzle 51 of the application device. Then, when the remaining protective film 50 is removed, the reinforcing material 24 is applied in a frame shape. The solid polymer electrolyte membrane 20 is turned upside down, and the reinforcing material 24 is similarly applied to the opposite surface in a frame shape.

 [0021] In order to enable the peripheral portion of the protective film 50 to be removed, it is preferable to form a cut body such as a perforation on the protective film 50 in advance. As a coating device, a device for coating a liquid packing for a field molded gasket (FIPG) used in engine parts, transmission parts, and the like can be used. By using this type of coating device, the reinforcing material 24 can be uniformly applied.

Referring to FIG. 3B, in the screen printing method, plate 52 having a thickness substantially equal to a desired coating thickness is used. The plate 52 has a through groove 53 that exposes only the protruding portion 22. The plate 52 is placed on the solid polymer electrolyte membrane 20 placed on the base 54, and the reinforcing material 24 is dropped on the plate 52. After that, the surface layer of the plate 52 is rubbed with a squeegee 55 made of plastic or metal, and the excess reinforcing material 24 is removed while filling the through-hole 53 with the reinforcing material 24. Then, when the plate 52 is removed, the reinforcing material 24 is applied in a frame shape. The solid polymer electrolyte membrane 20 is turned upside down, and the reinforcing material 24 is similarly applied to the opposite surface in a frame shape. Referring to FIG. 2A, frame-shaped reinforcing portions 23 are uniformly formed on rectangular cut pieces. The cut piece is prevented from being rounded or deformed by the shape retaining force provided by the reinforcing portion 23, and retains the original flat shape. Therefore, the handling performance of the solid polymer electrolyte membrane 20 alone is improved, and it is easy to perform the joining work with the gas diffusion layers 31 and 32 and the assembling work with the separators 41 and 42 to be performed later. The work can be automated.

 Referring to FIG. 1, in the solid polymer electrolyte membrane 20 of the present embodiment, the reinforcing portion 23 forms a seal member 25 between the reinforcing portions 23 and the separators 41 and 42.

 More specifically, the separators 41 and 42 of the present embodiment include first holding portions 41a and 42a that are bonded to the reinforcing portion 23 to hold the protruding portion 22, and a pair of gas diffusion layers 31 and 32. The second holding portions 41b and 42b for pressing the gas diffusion layers 31 and 32 against the respective surfaces of the main body portion 21 while holding the first holding portions 41a and 42a and the gas diffusion layers 31 and 32 outside. And void portions 47 and 48 formed between the peripheral portion and the peripheral portion. Reinforcing part 23 and first holding parts 41a, 4

 2a is bonded via an adhesive. The second holding portions 41b and 42b have a cross-sectional shape recessed with respect to the first holding portions 41a and 42a in order to receive the gas diffusion layers 31 and 32.

 [0026] The voids 47 and 48 are set to have a size that absorbs the crushing allowance of the gas diffusion layers 31 and 32 when the gas diffusion layers 31 and 32 are pressed against the main body 21. For this reason, the gas diffusion layers 31 and 32 can be pressed against the main body 21 with a sufficient surface pressure. An increase in internal resistance caused by an excessively small surface pressure is suppressed, and sufficient performance of the single cell 10 and, consequently, the fuel cell stack can be secured. Since the gas diffusion layers 31 and 32 are relatively thin, the dimensions between the first sandwiching portions 41a and 42a and the outer peripheral edges of the gas diffusion layers 31 and 32 are set as the sizes of the gaps 47 and 48. For example, a few mm is sufficient.

Further, the reinforcing portion 23 forms a seal member 25 with the first holding portions 41a and 42a. The gas seal is performed by the reinforcing portion 23 being pressed against the first holding portions 41a and 42a and elastically deforming. Since the member (reinforcing part 23) that enhances the handling properties of the solid polymer electrolyte membrane 20 alone has the function of sealing the gas flowing through the flow channels 44 and 46, a separate member only for sealing is separately provided. Reduced number of parts and manufacturing compared to the form of installation The process can be simplified.

 As described above, according to the present embodiment, in the solid polymer electrolyte membrane 20 for a fuel cell, the region interposed between the pair of gas diffusion layers 31 and 32 functioning as electrodes is formed. The main body part 21 to be formed, the protruding part 22 protruding from the outer peripheral edge of the gas diffusion layers 31 and 32, and the reinforcing material 24 applied to the protruding part 22 so as to surround the outer peripheral edge of the gas diffusion layers 31 and 32. And a reinforcing portion 23 having a shape of a frame formed.The reinforcing portion 23 imparts a shape retaining force to the main body portion 21 to prevent the main body portion 21 from being rounded. The flat shape that is the shape described in (1) above is maintained, and the handleability of the single unit becomes good. Through this, the production of the fuel cell can be simplified.

 [0029] Since the reinforcing portion 23 forms the seal member 25 between the separators 41 and 42, the reinforcing portion 23, which is a member for improving the handling property of the solid polymer electrolyte membrane 20 alone, Since the gas sealing function is exhibited, the number of parts can be reduced and the manufacturing process can be simplified as compared with a case where a member only for sealing is separately provided.

 [0030] Separators 41 and 42 for further sandwiching a pair of gas diffusion layers 31 and 32 sandwiching the main body 21 in the solid polymer electrolyte membrane 20 including the reinforcing portion 23, and are bonded to the reinforcing portion 23. First sandwiching portions 41a and 42a for sandwiching the protruding portion 22 and a pair of gas diffusion layers 31 and 32 for sandwiching the gas diffusion layers 31 and 32 against the respective surfaces of the main body portion 21 by pressing. And the second sandwiching portions 41b and 42b, and voids 47 and 48 formed between the first sandwiching portions 41a and 42a and the outer peripheral edges of the gas diffusion layers 31 and 32. , 48 are set to a size that absorbs the crushing allowance of the gas diffusion layers 31, 32 when the gas diffusion layers 31, 32 are pressed against the main body 21. , 42a, the sealing member 25 is formed between the solid polymer electrolyte membrane 20 having the reinforcing portion 23 and the main body 21 sandwiched therebetween. It can provide a suitable separator 41, 42 to further sandwich the gas diffusion layer 31, 32. In other words, the application of the solid polymer electrolyte membrane 20 having a good handling property as a single unit makes it possible to simplify the production of the fuel cell. Can be provided.

[0031] The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the claims. For example, the protruding portion 22 of the solid polymer electrolyte membrane 20 that protrudes from the gas diffusion layers 31 and 32 is located at a substantially central portion between the pair of separators 41 and 42. For this reason, when forming the reinforcing portion 23 having a gas sealing function, it is preferable that the cross-sectional shape of the reinforcing portion 23 is symmetrical with respect to the main body portion 21. This is to ensure a uniform pressing force between the separators 41 and 42. When the thickness dimensions of the gas diffusion layers 31 and 32 are different, the cross-sectional shape of the reinforcing portion 23 may be asymmetrical with respect to the main body portion 21 in order to secure a uniform pressing force.

 Further, the reinforcing portion 23 having only the function of preventing the force main body portion 21 from being rounded as described for the reinforcing portion 23 having the gas sealing function may be used. In this case, the reinforcing portion 23 can be formed only on either the front surface or the back surface of the solid polymer electrolyte membrane 20.

 [0034] Further, the present application is based on Japanese Patent Application No. 2004-048300 filed on February 24, 2004, the disclosure of which is referenced and incorporated in its entirety.

Claims

The scope of the claims  [1] In a solid polymer electrolyte membrane for a fuel cell,  A main body (21) forming a region interposed between the pair of gas diffusion layers (31, 32) functioning as electrodes;  A protruding portion (22) protruding from the outer peripheral edge of the gas diffusion layer (31, 32); and the reinforcing material (22) so that the protruding portion (22) surrounds the outer peripheral edge of the gas diffusion layer (31, 32). 24), and a frame-shaped reinforcing portion (23) formed by applying  The solid polymer electrolyte membrane for a fuel cell, wherein the reinforcing portion (23) imparts a shape retaining force to the main body (21) to prevent the main body (21) from rolling. [2] The reinforcing portion (23) includes the pair of gas diffusion layers (31, 2. The solid polymer electrolyte membrane for a fuel cell according to claim 1, wherein a see-through member (25) is formed between the separator and the separator (41, 42) for further sandwiching the (32). [3] A separator for further sandwiching a pair of gas diffusion layers (31, 32) sandwiching the main body (21) in the solid polymer electrolyte membrane for a fuel cell according to claim 1,  First holding portions (41a, 42a) bonded to the reinforcing portion (23) to hold the protruding portion (22);  A second sandwiching portion (41b, 42b) for sandwiching the pair of gas diffusion layers (31, 32) and pressing each gas diffusion layer against each surface of the main body (21);  A void portion (47, 48) formed between the first holding portion (41a, 42a) and an outer peripheral edge of the gas diffusion layer (31, 32);  The voids (47, 48) are sized to absorb the collapse of the gas diffusion layers (31, 32) when the gas diffusion layers (31, 32) are pressed against the main body (21). The separator for a fuel cell, wherein the reinforcing portion (23) constitutes a sealing member (25) between the reinforcing portion (23) and the first holding portions (41a, 42a).