JP2006338880A - Membrane-electrode assembly and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane-electrode assembly having a high strength, and a fuel cell utilizing this. <P>SOLUTION: This is the membrane-electrode assembly to have the membrane part which has a through-hole communicating both sides of the membrane part and in which a polyelectrolyte is filled into the through-hole, to have a core material which have a frame part thicker than the membrane part, to have a polyelectrolyte layer formed on both faces of the membrane part, to have a catalyst layer formed outside the polyelectrolyte layer, and to have a gas diffusion layer formed outside the catalyst layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a membrane-electrode assembly and a fuel cell. More specifically, the present invention relates to a membrane-electrode assembly having a core material and a fuel cell using the same.

  A polymer electrolyte fuel cell has a structure in which a polymer electrolyte membrane having proton conductivity is sandwiched between two electrodes (an anode and a cathode). An oxidant gas such as oxygen is supplied to the cathode. A fuel such as hydrogen is supplied to the anode, and protons and electrons are generated by an electrode reaction. The protons pass through the polymer electrolyte membrane and move to the cathode, and react with oxygen to generate water and the like. Although the electrons also move to the cathode, the energy of the chemical reaction can be used as electric power by taking out the current at that time.

  In order to realize such an operation, in a polymer electrolyte fuel cell, electrodes are bonded to both surfaces of a polymer electrolyte membrane to form a membrane-electrode assembly (MEA). The membrane-electrode assembly is insulated by an air-tight separator having engraved flow paths for the oxidant gas and the fuel gas, and the membrane-electrode assembly and the separator are stacked to form a stack.

  In general, in the production of a membrane-electrode assembly, a polymer electrolyte membrane is sandwiched between electrodes and a separator and joined mechanically or by hot pressing. For this reason, it is necessary to give the polymer electrolyte membrane sufficient strength so that it can withstand the pressure at the time of bonding and so that physical damage due to wear or the like does not occur during long-term use. On the other hand, for reasons such as improving proton conductivity, the polymer electrolyte membrane needs to be as thin as possible. Therefore, it is desirable to increase the strength of the polymer electrolyte membrane without increasing the thickness.

As techniques for solving such a problem, there are techniques disclosed in Patent Documents 1 to 3. In Patent Documents 1 to 3, the polymer electrolyte is held by a porous resin or substrate, and the physical strength of the polymer electrolyte membrane is improved.
JP-A-8-162132 JP-A-8-329962 Japanese Patent Laid-Open No. 9-120827

  However, the conventional configuration also has a problem that the physical strength of the polymer electrolyte membrane is insufficient. The present invention has been made to solve the above-described problems, and an object thereof is to provide a membrane-electrode assembly having high strength and a fuel cell using the membrane-electrode assembly.

  The present inventors made a composite membrane by using a porous resin having voids as a core material and impregnating it with a polymer electrolyte. Then, an electrode was formed at the center of both surfaces of the composite membrane, and the peripheral portion of the composite membrane was sandwiched from both sides with a gasket to prepare a membrane-electrode assembly. And the fuel cell was assembled using the said membrane-electrode assembly, and the test was done. As a result, it was found that breakage that appears to be due to insufficient strength of the composite film occurred in the joint portion (peripheral part) between the composite film and the gasket. This is presumed to be because the pressure when forming a stack by stacking concentrates on the joint portion of the composite film.

  Therefore, the core material itself was formed so that the thickness of the joining portion (peripheral portion) was larger than that of the central portion, thereby forming a frame portion. In the central portion, the void (void derived from the porous material) is impregnated with a polymer electrolyte to form a membrane portion, and electrodes and gas diffusion layers (GDLs) are formed on both sides thereof. An electrode assembly was obtained. Then, without using a gasket, the frame portion of the core material was directly sandwiched between separators to create a stack. With such a configuration, damage to the membrane was reduced. In this configuration, the physical strength of the contact portion with the separator is improved by forming the frame portion thickly. This is presumed to have improved the durability of the membrane at the fastening portion during fastening.

  In the above configuration, the frame itself can serve as a spacer. Therefore, a spacer such as a gasket is not necessarily required, and the structure can be simplified. In addition, the core material comes into contact with the separator, not the gas diffusion layer or the catalyst layer. Therefore, the gas diffusion layer and the catalyst layer are not crushed at the joint portion with the gasket, and are pushed evenly by the main surface of the separator. Therefore, the gas distribution and the electrode reaction distribution in the electrode can be equalized.

  Further, in the conventional configuration, the polymer electrolyte membrane is sandwiched by the gasket, and after a long period of time, there has been a problem that loosening occurs due to plastic deformation and stress relaxation (creep) at the joint portion. However, the above configuration has an advantage that such a problem does not occur because the frame portion corresponding to the gasket and the membrane portion corresponding to the polymer electrolyte membrane are integrally formed.

  In the above configuration, it is possible to form a fitting structure between the frame portion and the separator, and it is expected that the sealing performance is improved as compared with the case where the membrane is simply sandwiched by the gasket.

  In the conventional configuration, the polymer electrolyte membrane is sandwiched between gaskets, and the portion of the polymer electrolyte membrane that overlaps the gasket and the outside thereof are not involved in proton transport. However, the above configuration does not require a gasket. For this reason, if the gas diffusion layer is made larger than the polymer electrolyte layer and the catalyst layer, the entire surface of the polymer electrolyte membrane can participate in proton transport. Therefore, the utilization efficiency of the polymer electrolyte is improved.

  Further, in the conventional configuration, it is necessary to provide an interval (space) between the gasket and the catalyst layer so that the members do not overlap when sandwiched by the gasket. For this reason, there is a problem that a gap is formed between the gasket and the catalyst layer or the gas diffusion layer, and a gas short circuit or wraparound occurs through the gap. However, with the above configuration, it is considered that a polymer electrolyte layer is formed on the entire surface of the membrane portion, and an electrode is formed on the entire surface, thereby eliminating gaps and preventing gas short-circuiting and wraparound.

  Furthermore, in the conventional configuration, the membrane is sandwiched between gaskets, but there is a problem that positioning at this time is difficult. Further, there is a problem that positioning when placing the gas diffusion layer on the membrane-electrode assembly is difficult. However, if it is set as said structure, a polymer electrolyte will be comprised integrally with the core material corresponded to a gasket. Therefore, by forming a positioning concave portion or convex portion corresponding to the shape of the separator in the frame portion or forming a concave portion for fitting the gas diffusion layer, positioning can be easily performed.

That is, the membrane-electrode assembly of the present invention has the membrane portion having a through hole communicating with both sides of the membrane portion, the membrane portion filled with a polymer electrolyte, and a frame portion thicker than the membrane portion. A core material, a polymer electrolyte layer formed on both surfaces of the membrane part, a catalyst layer formed on the outside of the polymer electrolyte layer,
A gas diffusion layer formed outside the catalyst layer.

  Thereby, a junction part (frame part) with a separator is constituted thick, and physical strength improves. Further, since the frame itself has a thickness, it can serve as a spacer. Therefore, a spacer such as a gasket is not necessarily required, and the structure can be simplified. Furthermore, since the frame portion corresponding to the gasket and the membrane portion corresponding to the polymer electrolyte membrane are integrally formed, loosening due to stress relaxation does not occur.

  In the membrane-electrode assembly of the present invention, the membrane part may be porous by having a void, and the void may form the through hole. In such a configuration, since the voids of the porous material itself function as the through holes, the through holes can be easily formed in the film part.

  In the membrane-electrode assembly of the present invention, the membrane part may have a hole penetrating both surfaces, and the through hole may be the hole. Thereby, even when there is no through hole in the material itself, the through hole can be formed in the film part by punching or the like.

  In the membrane-electrode assembly of the present invention, the main surface of the gas diffusion layer may cover the entire main surface of the polymer electrolyte layer. Thereby, the entire surface of the polymer electrolyte layer contributes to proton transport. Therefore, the utilization efficiency of the polymer electrolyte can be improved.

  In the membrane-electrode assembly of the present invention, the main surface of the gas diffusion layer may cover the entire main surface of the catalyst layer. Thereby, the reaction gas (fuel gas, oxidant gas) supplied from the gas diffusion layer spreads over the entire surface of the catalyst layer, and an electrode reaction occurs. Therefore, the utilization efficiency of the catalyst can be improved.

  In the membrane-electrode assembly of the present invention, the main surface of the polymer electrolyte layer and the main surface of the catalyst layer may be equal in size. Thereby, protons generated by the electrode reaction generated in the catalyst layer are efficiently distributed throughout the polymer electrolyte layer. That is, the utilization efficiency of the catalyst and the polymer electrolyte can be improved.

  In the membrane-electrode assembly of the present invention, a recess may be provided on the inner periphery of the frame portion, and the gas diffusion layer may be fitted in the recess. This facilitates positioning between the membrane-electrode assembly and the gas diffusion layer.

  Or you may have a recessed part in the main surface of the said frame part. Or you may have a convex part in the main surface of the said frame part. Positioning between the membrane-electrode assembly and the separator is facilitated by using the concave portion or the convex portion as a meshing portion.

  The fuel cell of the present invention includes a core material having a through hole communicating with both sides of the membrane part, the membrane part filled with a polymer electrolyte in the through hole, and a frame part thicker than the membrane part. A membrane having a polymer electrolyte layer formed on both sides of the membrane portion, a catalyst layer formed outside the polymer electrolyte layer, and a gas diffusion layer formed outside the catalyst layer -An electrode assembly and a separator are provided, and the membrane-electrode assembly and the separator are laminated.

  Thereby, the junction part (frame part) with the separator of the membrane-electrode assembly, which is a main part of the fuel cell, is formed thick, and the physical strength is improved. Further, since the frame itself has a thickness, it can serve as a spacer. Therefore, when forming the stack, a spacer such as a gasket is not necessarily required, and the structure of the fuel cell can be simplified. Furthermore, since the frame portion corresponding to the gasket and the membrane portion corresponding to the polymer electrolyte membrane are integrally formed, loosening due to stress relaxation does not occur.

  The present invention has the above-described configuration and has the following effects. That is, it is possible to provide a membrane-electrode assembly having high strength and a fuel cell using the same.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
[Construction]
1-A and FIG. 1-B are diagrams showing an example of a schematic configuration of the membrane-electrode assembly 10 according to the first embodiment of the present invention, and FIG. 1-A is an IA-IA in FIG. A cross-sectional view along the line, FIG. 1-B is a front view. Hereinafter, the membrane-electrode assembly of the present embodiment will be described with reference to FIG.

  As shown in FIGS. 1A and 1B, the membrane-electrode assembly 10 of the present embodiment is a substantially rectangular plate-like core 1 as a whole having a membrane at the center and a frame at the periphery. A polymer electrolyte layer 2 formed on both sides of the main surface around the film-like portion of the core material 1, and a catalyst layer 3 (electrode layer) formed outside the polymer electrolyte layer 2; And a gas diffusion layer 4 formed outside the catalyst layer 3. That is, it has a structure in which the polymer electrolyte layer 2, the catalyst layer 3, and the gas diffusion layer 4 are sequentially laminated on both sides of the core portion 1 around the film-like portion.

  FIG. 2-A and FIG. 2-B are diagrams showing an example of a schematic configuration of the core material 1 in the first embodiment of the present invention, and FIG. 2-A is taken along line IIA-IIA in FIG. FIG. 2B is a plan view taken along a cross-sectional view. Hereinafter, the film-like portion at the center of the core material 1 is referred to as a film portion 5. A peripheral portion surrounding the film part 5 is called a frame part 6.

  Although the thickness of the membrane part 5 and the frame part 6 is not particularly limited, it is desirable that the membrane part 5 is as thin as possible from the viewpoint of ensuring proton conductivity. On the other hand, from the viewpoint of improving the strength, it is desirable that the thickness of the frame portion 6 is as thick as possible. Specifically, the thickness of the film part 5 is preferably about 1 to 20 μm, and the thickness of the frame part 6 is preferably about 100 to 500 μm.

  Referring to FIGS. 1-A, 1-B, 2-A, and 2-B, the thickness of the frame portion 6 is set so that both main surfaces thereof are positioned lower than the gas diffusion layer 4 in the thickness direction. Is formed. Moreover, it is preferable that the film part 5 is located in the middle of both main surfaces in the thickness direction of the frame part 6. Thereby, it becomes easy to arrange the polymer electrolyte layer 2, the catalyst layer 3, and the gas diffusion layer 4 symmetrically with respect to the membrane portion 5.

The polymer electrolyte layer 2 is preferably formed so as to overlap the membrane portion 5, that is, so as to cover the entire surface of the membrane portion 5 and the edges thereof coincide. The catalyst layer 3 is also preferably formed so as to overlap the main surface of the polymer electrolyte layer 2, that is, so as to cover the entire surface of the polymer electrolyte layer 2 and match the edges. That is, the areas of the membrane part 5, the polymer electrolyte layer 2, and the catalyst layer 3 are preferably substantially equal. The gas diffusion layer 4 is preferably formed so as to cover the entire main surface of the catalyst layer 3 and the periphery of the gas diffusion layer 4 protrudes from the edge of the catalyst layer 3. That is, the area of the gas diffusion layer 4 is preferably larger than that of the membrane part 5 and / or the polymer electrolyte layer 2 and / or the catalyst layer 3.
[material]
Polyphenyl sulfide (PPS) is preferably used as the material for the core material 1. In the case of using PPS, a hole penetrating the film part 5 in the thickness direction (called a through-hole) is formed in the film part 5 by punching or the like. The inside of the through hole is filled with a substance having proton conductivity (for example, an electrolyte, more preferably, a polymer electrolyte of the same kind or different kind from the polymer electrolyte layer 2). This is to ensure the proton conductivity of the membrane part 5. Therefore, in the core material 1, it is preferable that at least the film part 5 has a through hole in the film part 5. More preferably, it is preferable that a large number of through holes are formed uniformly on the entire surface of the film part 5. FIG. 3 is an enlarged schematic view of the cross section of the membrane portion 5 of the membrane-electrode assembly 10 according to the first embodiment of the present invention. As can be seen from FIG. 3, the membrane portion 5 has a number of through holes 1 a formed in the core material 1, and the inside of the through holes 1 a is filled with the polymer electrolyte 8.

As the material for the polymer electrolyte layer 2 and the polymer electrolyte 8, a polymer having proton conductivity can be used, and perfluorosulfonic acid is particularly preferably used. As the material of the catalyst layer 3, a conductor carrying a catalyst such as platinum (for example, acetylene black, ketjen, etc.) is preferably used. As the material of the gas diffusion layer 4, a conductor (for example, carbon nonwoven fabric, paper, etc.), filter paper, or the like is preferably used.
[Usage]
In the case of using the membrane-electrode assembly 10 of the present embodiment, the membrane-electrode assembly 10 is sandwiched by the separator 7 as shown by the dotted line in FIG. A flow path through which gas flows is formed in the separator 7 on the side in contact with the gas diffusion layer 4. Then, air, oxygen, or the like, which is an oxidant gas, flows through the flow path on one side (cathode side), and hydrogen-rich gas, which is a fuel gas, flows through the other (anode side). Each gas diffuses to the catalyst layer 3 through the gas diffusion layer 4. In the catalyst layer 3 on the anode side, protons and electrons are released from the fuel gas. The protons move to the cathode-side catalyst layer 3 through the anode-side polymer electrolyte layer 2, the core material 1, and the cathode-side polymer electrolyte layer 2. Therefore, the proton reacts with oxygen to produce water. On the other hand, since the electrons cannot pass through the polymer electrolyte layer 2, they move from the conductive catalyst layer 3 to the cathode through an external load. Thereby, the flow of electrons generated by a chemical reaction can be used as electric power.

By making the contact surface with the gas diffusion layer 4 planar in the separator 7, the gas diffusion layer 4, the catalyst layer 3, and the polymer electrolyte layer 2 are equally subjected to pressure. In such a configuration, it is expected that the gas distribution and the electrode reaction distribution are made more uniform.
[Production method]
Next, an example of the manufacturing method of the membrane-electrode assembly 10 of this embodiment will be described. 4A to 4E are schematic views schematically showing an example of a method for manufacturing the membrane-electrode assembly 10 according to the first embodiment of the present invention. FIG. 4-A shows a state before thermocompression bonding. 4-B is a state after thermocompression bonding, FIG. 4-C is a state in which the polymer electrolyte layer 2 is formed on the membrane portion 5, FIG. 4-D is a state in which the catalyst layer 3 is formed, and FIG. The state in which the gas diffusion layer 4 is formed is shown. As shown in FIG. 4A, first, one PPS perforated film 30 having a large number of through holes at least in the center is prepared. Next, a plurality of frame-type frame sheets 31 (made of PPS) having a rectangular opening at the center are prepared. Then, the frame sheet 31 is thermocompression bonded while being superimposed on both surfaces of the perforated film 30. Thereby, as shown to FIG. 4-B, the core material 1 which has the thick frame-shaped frame part 6 and the thin film-like film | membrane part 5 is obtained.

  Next, as shown in FIG. 4C, perfluorosulfonic acid resin dispersed in alcohol is applied to both surfaces of the film part 5. As the alcohol is volatilized, the polymer electrolyte layer 2 is formed on both sides of the membrane part 5 and the inside of the through holes of the membrane part 5 is also filled with the polymer electrolyte. As a method of forming the polymer electrolyte layer 2, existing thin film manufacturing techniques such as casting, spraying, and bar coater can be used.

  Next, as shown in FIG. 4-D, the catalyst layer 3 is formed on the polymer electrolyte layer 2. In a state before the fastening with the separator, the catalyst layer 3 protrudes slightly (about 10 μm) from the surface of the frame portion 6, and in a state where the catalyst layer 3 is fastened with the separator, the end surfaces of the catalyst layer 3 and the frame portion 6 are flush with each other. It is preferable that the thicknesses of the molecular electrolyte layer 2 and the catalyst layer 3 are adjusted. Specifically, the frame portion 6 is covered with a masking sheet, and carbon particles carrying a catalyst such as platinum are applied in a paste state on the polymer electrolyte layer 2 to the height of the masking sheet. If the masking sheet is peeled off after application, the catalyst layer 3 slightly protrudes (projects) from the end face of the frame portion 6. According to such a method, a structure without a gap between the catalyst layer 3 and the frame portion 6 can be easily created, and gas wraparound can be easily prevented.

  Alternatively, acetylene black, ketchen or the like carrying platinum may be cut out on the polymer electrolyte layers 2 on both sides to the same size as the frame portion 6 and fitted inside the frame portion 6. Thereby, the catalyst layer 3 is formed. The size of the catalyst layer 3 is preferably the same as that of the membrane part 5. Also, when fitting, if a polymer electrolyte is applied to the polymer electrolyte layer 2 such as acetylene black or ketjen and then pressed onto the polymer electrolyte layer 2, the resistance to proton transfer is lowered. This is preferable because it can provide an appropriate adhesive strength.

  Next, as shown to FIG. 4-E, the gas diffusion layer 4 is formed by mounting the carbon nonwoven fabric cut out in the rectangular shape, paper, etc. on the catalyst layer 3 of both surfaces. Here, the gas diffusion layer 4 is preferably larger than the membrane part 5 and the polymer electrolyte layer 2.

By the above method, the membrane-electrode assembly 10 having a structure in which the polymer electrolyte layer 2, the catalyst layer 3, and the gas diffusion layer 4 are sequentially laminated on both surfaces of the membrane portion 5 in the center of the core material 1 is obtained. . Further, a manifold hole through which gas or cooling water flows may be formed in the frame portion 6 according to the usage mode.
[Features and effects]
The first feature of the membrane-electrode assembly 10 of the present embodiment is that the frame portion 6 constituting the peripheral portion of the core material 1 is formed thicker than the membrane portion 5 constituting the central portion. Thereby, when the frame part 6 is fixed by being sandwiched between separators, the strength and durability are remarkably improved as compared to the case where the polymer electrolyte membrane is directly sandwiched and fixed. At the same time, since the frame portion 6 has a thickness, the frame portion 6 itself can serve as a spacer. Therefore, a spacer such as a gasket is not necessary, and the structure can be simplified. Further, if the frame portion 6 of the core material 1 is laminated as a joining portion with a separator or the like, the pressing of the joining portion at the time of stack formation is concentrated on the frame portion 6. Thereby, the pressure of a junction part does not apply to the polymer electrolyte layer 2, the catalyst layer 3, and the gas diffusion layer 4. FIG. Therefore, if the contact surface between the separator and the gas diffusion layer 4 is planar, the distribution of gas and electrode reaction can be equalized. Further, since the frame portion 6 and the film portion 5 are integrally formed, loosening due to plastic deformation and stress relaxation (creep) hardly occurs even after a long period of time. Further, in such a configuration, a fitting structure can be formed between the frame portion 6 and the separator as will be described later, and the sealing performance can be improved as compared with the case where the film is simply sandwiched by the gasket. Be expected.

  The second feature of the membrane-electrode assembly 10 of the present embodiment is that the gas diffusion layer 4 is larger than the polymer electrolyte layer 2 and the catalyst layer 3. Thereby, the entire surface of the polymer electrolyte layer 2 is involved in proton transport, and the utilization efficiency of the polymer electrolyte is improved. Further, the entire surface of the catalyst layer 3 is involved in the electrode reaction, and the utilization efficiency of the catalyst (platinum or the like) is improved.

The third feature of the membrane-electrode assembly 10 of the present embodiment is that the polymer electrolyte layer 2 is formed on the entire surface of the membrane portion 5 and the catalyst layer 3 is formed on the entire surface of the polymer electrolyte layer 2. is there. As a result, there is no gap between the frame 6 and the catalyst layer 3. Therefore, it is possible to prevent a short circuit and a wraparound of the reaction gas.
[Modification]
As a manufacturing method of the membrane-electrode assembly 10 of the present embodiment, the following may be considered. First, the polymer electrolyte layer 2 and the catalyst layer 3 are coated on a polypropylene film with a bar coater. At this time, the combined height of the polymer electrolyte layer 2 and the catalyst layer 3 slightly protrudes (about 10 μm) from the end face of the membrane part 5 to the end face of the frame part 6. Subsequently, the same size as the membrane part 5 is punched out, and the polymer electrolyte layer 2 and the catalyst layer 3 are laminated on the membrane part 5 in this order by transfer. Thereby, the catalyst layer 3 and the polymer electrolyte layer 2 become the same size, and the catalyst layer 3 becomes higher than the frame part 6. Subsequently, the gas diffusion layer 4 is formed on the catalyst layer 3, whereby the membrane-electrode assembly 10 is manufactured.

  The frame part 6 does not need to be thick over the entire circumference, and only a part of the frame part 6 may be formed thick. If only the junction with the separator is formed thick, the strength of the membrane-electrode assembly 10 can be improved.

  The material of the core material 1 is not necessarily polyphenyl sulfide (PPS). Any material may be used as long as it has sufficient strength to function as a core material and can secure voids (through holes) communicating with both sides (outside of both main surfaces) of the membrane portion 5. Preferably, a material having plastic deformability or a material having elasticity is preferable. Further, it is preferable to use a resin having thermoplasticity because molding is easy. As a material other than PPS, for example, polytetrafluoroethylene (PTFE) or the like can be used.

  The material of the film part 5 and the frame part 6 may not necessarily be the same kind. Any material may be used as long as the film portion 5 and the frame portion 6 can be firmly joined by welding or the like. For example, in FIG. 4, the perforated film 30 and the frame sheet 31 may be made of different materials. The perforated film 30 may be sandwiched between two frames (spacers) and joined.

  The through hole does not necessarily have to be macroscopic like a hole formed by punching. As long as both sides of the membrane part 5 are communicated with each other, a microscopic void that a porous material has may be used. In this case, the proton conductivity of the membrane part 5 can be ensured by making the voids derived from the porous pores and impregnating the voids with a polymer electrolyte. As a material having such voids, PTFE prepared to be porous is preferably used. When porous PTFE is used for the membrane part 5 of the core material 1, if the polymer electrolyte is applied from one side, the polymer electrolyte infiltrates to the opposite side due to capillary action, and the proton conductivity of the membrane part 5 Can be secured. That is, it is not necessary to apply the polymer electrolyte from both sides, and the processing method can be simplified. FIG. 5 is an enlarged schematic view of the cross section of the membrane portion 5 of the core material 1 when porous PTFE is used in the membrane-electrode assembly according to the first embodiment of the present invention. As can be seen from FIG. 5, the polymer electrolyte 8 is filled in the PTFE through holes 1a (voids), and the proton conductivity of the membrane part 5 is realized. In addition, when using porous PTFE, since it becomes possible to form the core material 1 not by thermocompression bonding of the sheet but by injection molding, there is an advantage that processing is easy. Note that the structure and the like of the membrane-electrode assembly are basically the same in the case of using PTFE as in the case of using PPS, and thus the description thereof is omitted.

  Further, the shape of the frame portion 6 does not necessarily have a flat surface as shown in FIG. The frame part 6 may be formed with a concave part or a convex part for joining a member (separator or the like) adjacent to the membrane-electrode assembly 10 at the time of lamination, or a concave part for fitting the gas diffusion layer. Thereby, positioning of a separator, a gas diffusion layer, etc. becomes easy. Moreover, airtightness can also be improved by fitting a separator etc. and the core material 1 over the perimeter of the frame part 6. FIG. The shape and position of the concave portion or convex portion provided in the frame portion 6 are not particularly limited. Hereinafter, although the specific example which provided the recessed part in the frame part 6 is demonstrated using FIG. 6 and FIG. 7, this invention is not limited to the following aspects.

  FIG. 6 is a schematic cross-sectional view of the membrane-electrode assembly according to the first embodiment of the present invention in which a step-shaped recess 9 a serving as a guide for fitting a separator is formed on the outer edge of the frame portion 6. In such a configuration, by providing a convex portion corresponding to the separator 7, positioning between the separator 7 and the membrane-electrode assembly 10 is facilitated.

  FIG. 7 is a schematic cross-sectional view of the membrane-electrode assembly according to the first embodiment of the present invention in which a stepped recess 9b serving as a guide for fitting the gas diffusion layer 4 is formed on the inner edge of the frame portion 6. It is. With this configuration, positioning between the gas diffusion layer 4 and the core material 1 is facilitated.

  In this embodiment, the structure does not include a gasket, but a structure including a gasket may be used as necessary. When the gasket is provided, the frame portion 6 is formed with a concave portion or a convex portion corresponding to the concave and convex portions of the gasket, thereby facilitating positioning and improving the sealing performance.

Further, it goes without saying that the membrane-electrode assembly 10, the core material 1, and the film part 5 do not necessarily have a rectangular plate shape as shown in FIG. 1, and may have a disk shape or the like. Further, the frame portion 6 may have a manifold through which oxidant gas, fuel gas, internal cooling water, and the like flow.
(Second Embodiment)
[Structure and materials]
FIG. 8 is a schematic diagram schematically showing a configuration example of the fuel cell 20 according to the second embodiment of the present invention. Hereinafter, the fuel cell 20 of the present embodiment will be described with reference to FIG.

  As shown in FIG. 8, the fuel cell 20 has a structure called a stack in which many cells 11 are stacked. The cell 11 is in contact with the membrane-electrode assembly 10 of the first embodiment, the anode separator 97 in contact with the anode-side main surface of the membrane-electrode assembly 10, and the cathode-side main surface of the membrane-electrode assembly 10. A cathode separator 96.

  The structure of the membrane-electrode assembly 10 includes a frame 6, a fuel gas supply manifold hole 102 a, an oxidant gas supply manifold hole 101 a, an internal cooling water supply manifold hole 103 a, a fuel gas discharge manifold hole 102 b, and an oxidant gas discharge manifold. Except for the fact that one hole 101b, one internal cooling water discharge manifold hole 103b, and six bolt holes 104 are formed, the description is omitted because it is the same as the description in the first embodiment.

  In the anode separator 97, a groove-like fuel gas channel 99 is formed on the main surface on the side in contact with the membrane-electrode assembly 10, and the groove-shaped internal cooling is formed on the main surface on the side not in contact with the membrane-electrode assembly 10. A water channel 100b is formed. A fuel gas supply manifold hole 102a, an oxidant gas supply manifold hole 101a, an internal cooling water supply manifold hole 103a, a fuel gas discharge manifold hole 102b, and an oxidant gas are provided at the peripheral part of the anode separator 97 so as to penetrate the peripheral part. One discharge manifold hole 101b, one internal cooling water discharge manifold hole 103b, and six bolt holes 104 are formed. The fuel gas flow path 99 is formed to connect the fuel gas supply manifold hole 102a and the fuel gas discharge manifold hole 102b, and the internal cooling water flow path 100b is connected to the internal cooling water supply manifold hole 103a and the internal cooling water discharge manifold hole. 103b is connected.

  Further, the cathode separator 96 has a groove-like oxidant gas flow path 98 formed on the main surface on the side in contact with the membrane-electrode assembly 10, and the groove-shaped on the main surface on the side not in contact with the membrane-electrode assembly 10. An internal cooling water channel 100a is formed (not shown in the figure, but the shape is the same as the internal cooling water channel 100b). A fuel gas supply manifold hole 102a, an oxidant gas supply manifold hole 101a, an internal cooling water supply manifold hole 103a, a fuel gas discharge manifold hole 102b, and an oxidant gas are provided at the peripheral part of the cathode separator 96 so as to penetrate the peripheral part. One discharge manifold hole 101b, one internal cooling water discharge manifold hole 103b, and six bolt holes 104 are formed. The oxidant gas flow path 98 is formed to connect the oxidant gas supply manifold hole 101a and the oxidant gas discharge manifold hole 101b, and the internal cooling water flow path 100b is connected to the internal cooling water supply manifold hole 103a and the internal cooling water. It is formed so as to connect to the discharge manifold hole 103b.

  As a result, the fuel cell 20 includes the fuel gas supply manifold hole 102a, the oxidant gas supply manifold hole 101a, and the internal cooling water supply manifold hole 103a formed in the membrane-electrode assembly 10, the anode separator 97, and the cathode separator 96. The fuel gas discharge manifold hole 102b, the oxidant gas discharge manifold hole 101b, the internal cooling water discharge manifold hole 103b, and the bolt hole 104 are connected to each other, and the fuel gas supply manifold, the oxidant gas supply manifold, and the internal cooling water supply manifold are connected. A fuel gas discharge manifold, an oxidant gas discharge manifold, an internal cooling water discharge manifold, and six bolt holes are formed. Further, the internal cooling water channel 100 b on the outer surface of the anode separator 97 and the internal cooling water channel 100 a on the outer surface of the cathode separator 96 are combined to form one internal cooling water channel between two adjacent cells 11.

The anode separator 97 and the cathode separator 96 are made of a conductor. Since the cell 11 functions as a battery by itself, the cells 11 are connected in series by stacking the cells 11 and function as a single large battery as a whole. A pair of end plates 12 are disposed at both ends of the stack, and a current collector plate (not shown) and an electrical output terminal (not shown) are arranged on each end plate. The cell 11 has a bolt hole at the periphery. The cells 11 are stacked, both ends are pressed by the end plates 12, and then fastened by bolts (not shown) that penetrate the bolt holes.
[Usage]
The usage mode of the fuel cell power generation of the present embodiment having the above configuration will be schematically described below.

  First, the flow of fuel gas and oxidant gas and power generation will be described. In this embodiment, for example, hydrogen is used as the fuel gas, and air is used as the oxidant gas. Then, the fuel gas and the oxidant gas are supplied from the external supply device to the fuel gas channel 99 and the oxidant gas channel 98 through the fuel gas supply manifold and the oxidant gas supply manifold, respectively.

  When the fuel gas and the oxidant gas are supplied to the fuel cell 20, the fuel gas and the oxidant gas cause an electrochemical reaction in each of the cells 11 to generate electric power. The electric power is taken out through the electric output terminal and used.

  In the fuel cell 20, fuel exhaust gas and oxidant exhaust gas are generated from the fuel gas and oxidant gas. The fuel exhaust gas and the oxidant exhaust gas are discharged out of the system through a fuel gas exhaust manifold and an oxidant gas exhaust manifold, respectively.

Next, the flow of internal cooling water and generation of heat will be described. In order to efficiently generate an electrochemical reaction in the fuel cell 20, it is necessary to keep the temperature of the cell 11 at a constant temperature. When the electrochemical reaction occurs, heat is generated. In order to remove the heat, the internal cooling water is supplied to the internal cooling water flow paths 100a and 100b of the respective cells 11 through the internal cooling water supply manifold by a cooling water pump or the like. And after receiving heat from the cell 11, internal cooling water is discharged | emitted out of a system through an internal cooling water discharge manifold. Thereby, the heat generated inside the fuel cell 20 is discharged outside the system. The temperature of the cell 11 is kept constant by adjusting the flow rate of the fuel gas, the oxidant gas, the internal cooling water, and the like.
[Features and effects]
The feature of the fuel cell 20 of the present embodiment is that the membrane-electrode assembly 10 of the first embodiment is provided. That is, the membrane-electrode assembly 10 included in the fuel cell 20 has a substantially rectangular plate-shaped core material 1 having a membrane portion 5 and a frame portion 6 as shown in FIG. A polymer electrolyte layer 2 formed on both sides of the main surface, a catalyst layer 3 formed outside the polymer electrolyte layer 2, and a gas formed outside the catalyst layer 3 And a diffusion layer 4.

  That is, the first feature of the fuel cell 20 of the present embodiment is that in the membrane-electrode assembly 10, the frame portion 6 of the core material 1 is formed thicker than the membrane portion 5. Thereby, when the frame part 6 is fixed by being sandwiched between separators, the strength and durability are remarkably improved as compared to the case where the polymer electrolyte membrane is directly sandwiched and fixed. At the same time, since the frame portion 6 has a thickness, the frame portion 6 itself can serve as a spacer. Therefore, a spacer such as a gasket is not necessary, and the structure can be simplified. Further, if the frame portion 6 of the core material 1 is laminated as a joining portion with a separator or the like, the pressing of the joining portion at the time of stack formation is concentrated on the frame portion 6. Thereby, the pressure of a junction part does not apply to the polymer electrolyte layer 2, the catalyst layer 3, and the gas diffusion layer 4. FIG. Therefore, if the contact surface between the separator and the gas diffusion layer 4 is planar, the distribution of gas and electrode reaction can be equalized. Furthermore, since the frame portion 6 and the film portion 5 are integrally formed, loosening due to plastic deformation and stress relaxation (creep) is unlikely to occur even after a long period of time. Further, in such a configuration, it is possible to dispose the meshing portion between the frame portion 6 and the separator, and it is expected that the sealing performance is improved as compared with the case where the membrane is simply sandwiched by the gasket.

  The second feature of the fuel cell 20 of the present embodiment is that the gas diffusion layer 4 is larger than the polymer electrolyte layer 2 and the catalyst layer 3 in the membrane-electrode assembly 10. Thereby, the entire surface of the polymer electrolyte layer 2 is involved in proton transport, and the utilization efficiency of the polymer electrolyte is improved. Further, the entire surface of the catalyst layer 3 is involved in the electrode reaction, and the utilization efficiency of the catalyst (platinum or the like) is improved.

  The third feature of the fuel cell 20 of the present embodiment is that in the membrane-electrode assembly 10, the polymer electrolyte layer 2 is formed on the entire surface of the membrane portion 5, and the catalyst layer 3 is further formed on the entire surface of the polymer electrolyte layer 2. There is a place to form. Thereby, there is no gap between the frame portion 6 and the catalyst layer 3. Therefore, it is possible to prevent a short circuit and a wraparound of the reaction gas. Therefore, the fuel utilization efficiency is improved.

Considering the above characteristics, the fuel cell 20 of the present embodiment is expected to extend the life of the fuel cell and the fuel cell and improve the utilization efficiency of the fuel and the catalyst.
[Modification]
The fuel cell 20 of this embodiment may be configured as a fuel cell system including a fuel supply device (hydrogen generation device), an oxidant supply device, an internal cooling water circulation device, and the like.

  The membrane-electrode assembly and fuel cell of the present invention are useful as a membrane-electrode assembly having high strength and a fuel cell using the same.

It is sectional drawing which shows an example of schematic structure of the membrane-electrode assembly of 1st Embodiment of this invention. It is a front view which shows an example of schematic structure of the membrane-electrode assembly of 1st Embodiment of this invention. It is sectional drawing which shows an example of schematic structure of the core material in 1st Embodiment of this invention. It is a top view which shows an example of schematic structure of the core material in 1st Embodiment of this invention. It is the schematic diagram which expanded the cross section of the film | membrane part of the membrane-electrode assembly of 1st Embodiment of this invention. It is a schematic diagram which shows roughly an example of the manufacturing method of the membrane-electrode assembly of 1st Embodiment of this invention, Comprising: It is a figure which shows the state before thermocompression bonding. It is a schematic diagram which shows roughly an example of the manufacturing method of the membrane-electrode assembly of 1st Embodiment of this invention, Comprising: It is a figure which shows the state after thermocompression bonding. It is a schematic diagram which shows roughly an example of the manufacturing method of the membrane-electrode assembly of 1st Embodiment of this invention, Comprising: It is a figure which shows the state which formed the polymer electrolyte layer in the film | membrane part. It is a schematic diagram which shows roughly an example of the manufacturing method of the membrane-electrode assembly of 1st Embodiment of this invention, Comprising: It is a figure which shows the state in which the catalyst layer was formed. It is a schematic diagram which shows roughly an example of the manufacturing method of the membrane-electrode assembly of 1st Embodiment of this invention, Comprising: It is a figure which shows the state in which the gas diffusion layer was formed. In the membrane-electrode assembly of 1st Embodiment of this invention, it is the schematic diagram which expanded the cross section of the film | membrane part of the core material at the time of using porous PTFE. In the membrane-electrode assembly of 1st Embodiment of this invention, it is a schematic diagram of the cross section at the time of forming the recessed part used as a guide for inserting a separator in the outer edge of a frame part. In the membrane-electrode assembly of 1st Embodiment of this invention, it is a schematic diagram of the cross section at the time of forming the recessed part used as a guide for inserting a gas diffusion layer in the inner edge of a frame part. It is a schematic diagram which shows the structural example of the fuel cell of 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core material 1a Through-hole 2 Polymer electrolyte layer 3 Catalyst layer 4 Gas diffusion layer 5 Membrane part 6 Frame part 7 Separator 8 Polymer electrolyte 9a Recess 9b Recess 10 Membrane-electrode assembly 11 Cell 12 End plate 20 Fuel cell 30 Existence Perforated film 31 Frame sheet 96 Cathode separator 97 Anode separator 98 Oxidant gas channel 99 Fuel gas channel 100a, 100b Internal coolant channel 101a Oxidant gas supply manifold hole 101b Oxidant gas discharge manifold hole 102a Fuel gas supply manifold hole 102b Fuel gas discharge manifold hole 103a Internal cooling water supply manifold hole 103b Internal cooling water discharge manifold hole 104 Bolt hole

Claims (10)

A core material having a through hole communicating with both sides of the film part and having the film part filled with a polymer electrolyte in the through hole, and a frame part thicker than the film part;
A polymer electrolyte layer formed on both surfaces of the membrane part;
A catalyst layer formed outside the polymer electrolyte layer;
And a gas diffusion layer formed outside the catalyst layer. The membrane-electrode assembly according to claim 1, wherein the membrane part is porous by having a void, and the void forms the through hole. 2. The membrane-electrode assembly according to claim 1, wherein the film part has a hole penetrating both sides of the film part, and the through hole is the hole. The membrane-electrode assembly according to claim 1, wherein the main surface of the gas diffusion layer covers the entire main surface of the polymer electrolyte layer. The membrane-electrode assembly according to claim 1, wherein the main surface of the gas diffusion layer covers the entire main surface of the catalyst layer. The membrane-electrode assembly according to claim 1, wherein the main surface of the polymer electrolyte layer and the main surface of the catalyst layer have the same size. 2. The membrane-electrode assembly according to claim 1, wherein the inner periphery of the frame has a recess, and the gas diffusion layer is fitted in the recess. The membrane-electrode assembly according to claim 1, wherein the main surface of the frame portion has a recess. The membrane-electrode assembly according to claim 1, wherein the main surface of the frame portion has a convex portion. A core having a membrane portion filled with a polymer electrolyte, a frame portion thicker than the membrane, a polymer electrolyte layer formed on both surfaces of the membrane, and the polymer electrolyte layer A membrane-electrode assembly having a catalyst layer formed on the outside and a gas diffusion layer formed on the outside of the catalyst layer;
A separator,
A fuel cell in which the membrane-electrode assembly and the separator are laminated.

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