JP5611604B2 - Method for manufacturing membrane-electrode structure - Google Patents

Description

  The present invention relates to a method for producing a membrane-electrode structure.

  2. Description of the Related Art Conventionally, a membrane-electrode structure used in a fuel cell or the like includes a pair of electrodes including a catalyst layer and a gas diffusion layer, and a solid polymer electrolyte membrane sandwiched by the catalyst layers of both electrodes. Are known. In the membrane-electrode structure, for example, the catalyst layer and the gas diffusion layer of both electrodes are formed in the same size as the polymer electrolyte membrane, and the outer peripheral edge of both electrodes is the polymer electrolyte membrane. It is laminated | stacked so that it may correspond with the outer periphery.

  However, when the outer peripheral edges of the electrodes are stacked so as to coincide with the outer peripheral edge of the polymer electrolyte membrane, the gas supplied to each gas diffusion layer is opposite to the outer peripheral edge of the polymer electrolyte membrane. There is a problem of wrapping around and mixing each other. Moreover, since the positions of the outer peripheral edges of both electrodes are close, there is a problem that both electrodes may be electrically short-circuited.

  In order to solve the above problem, the polymer electrolyte membrane is formed larger than both electrodes, and is laminated such that the outer peripheral edge of both electrodes is located on the inner peripheral side of the outer peripheral edge of the polymer electrolyte membrane 2 -Electrode structures are known. According to the membrane-electrode structure having such a configuration, the gas supplied to each gas diffusion layer is shielded by the portions projecting outward from the outer peripheral edges of both electrodes of the polymer electrolyte membrane. Mixing can be prevented. Further, the overhanging portion of the polymer electrolyte membrane can prevent an electrical short circuit between both electrodes.

  However, in a fuel cell using the membrane-electrode structure, if the thickness of the polymer electrolyte membrane is reduced in order to improve the output, the mechanical strength of the polymer electrolyte membrane is reduced, and the outside of both electrodes The part that protrudes from the peripheral edge tends to be damaged. Therefore, the present applicant has positioned the catalyst layer on the inner peripheral side of the outer peripheral edge of the solid polymer electrolyte membrane, and the gas diffusion layer of at least one electrode covers the solid polymer electrolyte membrane. At the same time, there has been proposed a membrane-electrode structure that is bonded to the solid polymer electrolyte membrane via an adhesive layer provided on the entire periphery of the outer periphery (see Patent Document 1). In the membrane-electrode structure described in Patent Document 1, the adhesive layer is expected to protect the polymer electrolyte membrane extending outward from the outer peripheral edge of the catalyst layer and prevent damage. Is done.

  In the membrane-electrode structure described in Patent Document 1, the solid polymer electrolyte membrane sandwiched between the catalyst layers of the pair of electrodes is hot-pressed to integrate the electrodes and the solid polymer electrolyte membrane. It is manufactured by.

  By the way, the fuel cell is configured by laminating a large number of membrane-electrode structures with separators interposed therebetween. At this time, if the thickness of each membrane-electrode structure varies, a predetermined performance may not be obtained in the fuel cell. Therefore, the hot press is a membrane-electrode structure formed by pressing the solid polymer electrolyte membrane sandwiched between the pair of electrodes with a pressure of about 1.5 to 4.5 MPa. The body is plastically deformed to a predetermined thickness.

JP 2003-68323 A

  However, when the solid polymer electrolyte membrane sandwiched between the pair of electrodes is pressed with one behavior at a pressure in the range, the adhesive constituting the adhesive layer excessively penetrates the gas diffusion layer, There is an inconvenience that sufficient adhesive strength cannot be obtained between the solid polymer electrolyte membrane and the gas diffusion layer.

  The present invention eliminates such inconvenience, can prevent damage to the solid polymer electrolyte membrane extending outward from the outer peripheral edge of the catalyst layer, and can form a membrane-electrode structure with a predetermined thickness. In addition, an object is to provide a production method capable of obtaining excellent adhesive strength between the solid polymer electrolyte membrane and the gas diffusion layer.

In order to achieve such an object, the present invention provides a membrane-electrode structure comprising a pair of electrodes comprising a catalyst layer and a gas diffusion layer, and a solid polymer electrolyte membrane sandwiched between the catalyst layers of both electrodes. The catalyst layers of both electrodes are located on the inner peripheral side of the outer peripheral edge of the solid polymer electrolyte membrane, and the gas diffusion layer of at least one electrode covers the solid polymer electrolyte membrane, In the method of manufacturing a membrane-electrode structure bonded to the solid polymer electrolyte membrane via an adhesive layer provided on the entire outer periphery, the solid height sandwiched between the pair of electrodes. A first pressing step of pressing a molecular electrolyte membrane to cure the adhesive layer to form a membrane-electrode structure; and pressing the membrane-electrode structure with a pressure greater than that of the first pressing step. The second pressing process for forming the membrane-electrode structure to a predetermined thickness With the door, the second pressing step, and carrying out immediately following the first pressing step.

According to the manufacturing method of the present invention, when the solid polymer electrolyte membrane sandwiched between the pair of electrodes is pressed to integrate the electrodes and the solid polymer electrolyte membrane, first, the first press The adhesive layer is cured in the process. Then, immediately after the first pressing step, in the second pressing step, the membrane-electrode structure is pressed at a predetermined thickness by pressing the membrane-electrode structure with a pressure larger than that of the first pressing step. Molded to the size.

  Therefore, according to the manufacturing method of the present invention, the adhesive forming the adhesive layer is prevented from excessively penetrating into the gas diffusion layer, and between the solid polymer electrolyte membrane and the gas diffusion layer. Excellent adhesion strength can be obtained. As a result, according to the production method of the present invention, the solid polymer electrolyte membrane extending outward from the outer periphery of the catalyst layer can be protected by the gas diffusion layer, and the solid polymer electrolyte membrane can be protected. Can be prevented from being damaged.

  Furthermore, according to the manufacturing method of the present invention, after the adhesive layer is cured and the solid polymer electrolyte membrane and the gas diffusion layer are bonded, the membrane- By pressing the electrode structure, the membrane-electrode structure can be plastically deformed and reliably formed into a predetermined thickness.

  In the production method of the present invention, the first pressing step is performed at a pressure in the range of 0.15 to 0.75 MPa, and the second pressing step is performed at a pressure in the range of 1.5 to 4.5 MPa. Preferably it is done.

  If the pressure in the first pressing step is less than 0.15 MPa, it may be difficult to cure the adhesive layer. Moreover, when the pressure in the first pressing step exceeds 0.75 MPa, the adhesive forming the adhesive layer easily penetrates into the gas diffusion layer.

  On the other hand, if the pressure in the second pressing step is less than 1.5 MPa, the membrane-electrode structure formed in the first pressing step may not be plastically deformed. Further, when the pressure in the second pressing step exceeds 4.5 MPa, the membrane-electrode structure may be excessively plastically deformed.

Explanatory sectional drawing which shows the example of 1 structure of the membrane-electrode structure obtained by the manufacturing method of this invention. The top view which shows the structure of the electrode used for the membrane-electrode structure shown in FIG. Explanatory sectional drawing which shows the manufacturing method of the membrane-electrode structure shown in FIG.

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

  The manufacturing method of this embodiment is used, for example, for manufacturing the membrane-electrode structure 1 having the configuration shown in FIG. The membrane-electrode structure 1 includes a polymer electrolyte membrane 2 and a pair of electrodes 3 and 4 that sandwich the polymer electrolyte membrane 2. Each of the electrodes 3 and 4 includes catalyst layers 5 and 6 and gas diffusion layers 7 and 8, and the polymer electrolyte membrane 2 is sandwiched between the catalyst layers 5 and 6.

  In the membrane-electrode structure 1, one electrode 3 is located on the inner peripheral side of the outer peripheral edge of the solid polymer electrolyte membrane 2, and the catalyst layer 5 and the gas diffusion layer 7 have the same size. ing. On the other hand, in the other electrode 4, the catalyst layer 6 is located on the inner peripheral side with respect to the outer peripheral edge of the solid polymer electrolyte membrane 2, but the gas diffusion layer 8 is the same as the solid polymer electrolyte membrane 2. It has a size and is adhered to the solid polymer electrolyte membrane 2 via an adhesive layer 9 provided on the outer peripheral edge. The adhesive layer 9 is formed over the entire outer periphery of the gas diffusion layer 8, and the inner periphery is in contact with the outer periphery of the catalyst layer 6.

  According to the membrane-electrode structure 1 having the above-described configuration, the solid polymer electrolyte membrane 2 extends outward from the outer peripheral edges of the catalyst layers 5 and 6, and thus is supplied to the gas diffusion layers 7 and 8. Gases can be prevented from mixing with each other. Moreover, it is possible to prevent the electrodes 3 and 4 from being electrically short-circuited. Furthermore, since the solid polymer electrolyte membrane 2 is bonded to the gas diffusion layer 8 via the adhesive layer 9 and supported by the gas diffusion layer 8, it can be prevented from being damaged.

  In the membrane-electrode structure 1, the catalyst layer 6 of the electrode 4 is smaller than the catalyst layer 5 of the electrode 3 and is located on the inner peripheral side of the outer peripheral edge of the catalyst layer 5. By doing so, the edges of the catalyst layers 5, 6 are arranged at different positions with respect to the solid polymer electrolyte membrane 2, and the solid polymer electrolyte membrane 2 is formed by the edges of the catalyst layers 5, 6. Such stress can be reduced.

  Next, a method for manufacturing the membrane-electrode structure 1 will be described.

  First, the solid polymer electrolyte membrane 2 is prepared. As the solid polymer electrolyte membrane 2, a membrane made of a polymer electrolyte such as a perfluorosulfonic acid polymer compound (for example, Nafion (trade name) manufactured by DuPont) or a sulfonated polyarylene compound can be used. The solid polymer electrolyte membrane 2 can be formed by a conventional method, for example, a cast method from an organic solvent solution of the polymer electrolyte.

  Next, the electrodes 3 and 4 are produced. The electrodes 3 and 4 are formed by laminating catalyst layers 5 and 6 on gas diffusion layers 7 and 8 made of a porous body such as carbon cloth or carbon paper. The catalyst layers 5 and 6 can be formed by applying or depositing a catalyst paste on the gas diffusion layers 7 and 8. The catalyst paste includes, for example, catalyst particles in which platinum particles are supported on carbon black, and an ion conductive binder.

  Here, as shown in FIG. 2 (a), the electrode 3 is coated with the catalyst paste on the entire surface of the gas diffusion layer 7 having a size that fits on the inner peripheral side of the outer peripheral edge of the solid polymer electrolyte membrane 2. The catalyst layer 5 is formed by vapor deposition. On the other hand, as shown in FIG. 2B, the electrode 4 is accommodated on the gas diffusion layer 8 having the same size as that of the solid polymer electrolyte membrane 2 so as to be accommodated on the inner peripheral side from the outer peripheral edge of the gas diffusion layer 8. Further, the catalyst layer 6 is formed by applying or vapor-depositing the catalyst paste.

  In addition, the electrode 4 is coated with an adhesive over the entire circumference of the outer peripheral edge thereof, and forms an adhesive layer 9 in contact with the catalyst layer 6. Examples of the adhesive that forms the adhesive layer 9 include adhesives such as epoxy resin adhesives, olefin resin adhesives, acrylic resin adhesives, urethane resin adhesives, and fluororesin adhesives. be able to.

  Next, as shown in FIG. 3, the electrodes 3 and 4 are laminated on the front and back surfaces of the solid polymer electrolyte membrane 2 so as to be in contact with the solid polymer electrolyte membrane 2 on the catalyst layers 5 and 6 side.

  Next, a first hot press process is performed on the solid polymer electrolyte membrane 2 on which the electrodes 3 and 4 are laminated, thereby forming a membrane-electrode structure 1 having the configuration shown in FIG. The first hot press treatment is performed, for example, at a temperature in the range of 100 to 200 ° C., a pressure in the range of 0.15 to 0.75 MPa, and a time within 60 seconds. As a result, the catalyst layers 5 and 6 are thermocompression bonded to the solid polymer electrolyte membrane 2 and the adhesive layer 9 is cured to securely bond the gas diffusion layer 8 on the electrode 4 side to the solid polymer electrolyte membrane 2. .

  Next, the membrane-electrode structure 1 formed by the first hot press process is subjected to a second hot press process to form the film-electrode structure 1 to a predetermined thickness. The second hot press treatment is performed, for example, at a temperature in the range of 100 to 200 ° C., a pressure in the range of 1.5 to 4.5 MPa, and a time within 50 to 500 seconds. As a result, the membrane-electrode structure 1 can be plastically deformed and formed to a predetermined thickness. At this time, since the adhesive layer 9 has already been cured by the first hot press treatment, it is possible to prevent the adhesive from penetrating into the gas diffusion layer 8.

The second hot press process is performed immediately after the first hot press process to prevent misalignment of the solid polymer electrolyte membrane 2, the catalyst layers 5, 6, and the gas diffusion layers 7, 8. can do. In addition, an effect of shortening the cycle time can be obtained by performing the second hot press process immediately after the first hot press process.

  In the method of the present embodiment, the catalyst layers 5 and 6 are formed by applying or vapor-depositing the catalyst paste on the gas diffusion layers 7 and 8, but the catalyst paste is applied on a substrate such as another film. The catalyst layers 5 and 6 thus formed may be thermally transferred to the solid polymer electrolyte membrane 2. In this case, the gas diffusion layer 7 and the gas diffusion layer 8 on which the adhesive layer 9 is formed are laminated on the solid polymer electrolyte membrane 2 to which the catalyst layers 5 and 6 are transferred, and the first and the first The hot pressing process 2 may be performed.

  Next, examples and comparative examples of the present invention are shown.

  In this example, the gas diffusion layer 8 was produced using an epoxy resin adhesive (trade name: TB2204, manufactured by Three Bond Co., Ltd.) as an adhesive for forming the adhesive layer 9.

  Next, the solid polymer electrolyte membrane 2 on which the electrodes 3 and 4 were laminated was subjected to a first hot press treatment to form a membrane-electrode structure 1 having the configuration shown in FIG. The first hot press treatment was performed at a pressure of 0.3 MPa at a temperature of 160 ° C. for 30 seconds.

  Next, the membrane-electrode structure 1 formed by the first hot press process was subjected to a second hot press process to form the film-electrode structure 1 to a predetermined thickness. The second hot press treatment was performed at a temperature of 160 ° C. and a pressure of 3 MPa for 4 minutes and 30 seconds.

As a result, it was possible to obtain a membrane-electrode structure 1 having a predetermined thickness and having the gas diffusion layer 8 on the electrode 4 side securely bonded to the solid polymer electrolyte membrane 2.
[Comparative Example]
In this comparative example, only the second hot press process was performed for 5 minutes on the solid polymer electrolyte membrane 2 on which the electrodes 3 and 4 were laminated without performing the first hot press process in the above example. Except for the above, the membrane-electrode structure 1 was molded to a predetermined thickness in exactly the same manner as in the previous example.

  As a result, the membrane-electrode structure 1 having a predetermined thickness could be obtained. In the membrane-electrode structure 1, the adhesive forming the adhesive layer 9 was diffused on the electrode 4 side. Layer 8 was penetrating excessively. For this reason, in the membrane-electrode structure 1, sufficient adhesive force could not be obtained between the gas diffusion layer 8 on the electrode 4 side and the solid polymer electrolyte membrane 2.

  DESCRIPTION OF SYMBOLS 1 ... Membrane-electrode structure, 2 ... Solid polymer electrolyte membrane, 3, 4 ... Electrode, 5, 6 ... Catalyst layer, 7, 8 ... Gas diffusion layer, 9 ... Adhesive layer.

Claims (2)

A membrane-electrode structure comprising a pair of electrodes comprising a catalyst layer and a gas diffusion layer, and a solid polymer electrolyte membrane sandwiched between the catalyst layers of both electrodes, wherein the catalyst layers of both electrodes are The gas diffusion layer of at least one electrode located on the inner peripheral side of the outer peripheral edge of the solid polymer electrolyte membrane covers the solid polymer electrolyte membrane, and is provided on the outer peripheral edge over the entire periphery In the method for producing a membrane-electrode structure bonded to the solid polymer electrolyte membrane via an agent layer,
A first pressing step of pressing the solid polymer electrolyte membrane sandwiched between the pair of electrodes to cure the adhesive layer to form a membrane-electrode structure;
A second pressing step of pressing the membrane-electrode structure with a pressure larger than that of the first pressing step to form the membrane-electrode structure to a predetermined thickness;
The method of manufacturing a membrane-electrode structure, wherein the second pressing step is performed immediately after the first pressing step.   2. The method of manufacturing a membrane-electrode structure according to claim 1, wherein the first pressing step is performed at a pressure in a range of 0.15 to 0.75 MPa, and the second pressing step is 1.5 to 0.75. The manufacturing method of the membrane-electrode structure characterized by performing by the pressure of the range of 4.5 Mpa.

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