JP5205960B2 - Fuel cell and manufacturing method thereof - Google Patents

Description

  The present invention relates to a fuel cell and a method for manufacturing the same, and in particular, for example, in a polymer electrolyte fuel cell, when the periphery of a laminate of a membrane electrode assembly and a diffusion layer or a separator is integrated with a resin material that functions as a gasket. The present invention relates to a fuel cell having an improved bonding state and a method for manufacturing the same.

  A polymer electrolyte fuel cell is known as one of the fuel cells. FIG. 6 is a cross-sectional view showing an example thereof, in which a membrane electrode assembly 3 including an electrode layer 2 in which a catalyst layer and a diffusion layer are laminated in this order is formed on both surfaces of an electrolyte membrane 1, and a gas is formed on both sides thereof. Separators 5 and 5 having a flow path 4 are stacked. Usually, the separator 5 is made by processing a metal plate into a sheet metal. An electrolyte membrane 1a protrudes around the electrode layer 2, and a resin material is filled as a gasket 6 between the protruding electrolyte membrane portion 1a and the separator 5 to perform integration and sealing treatment.

  When the fuel cell is continuously operated, the electrolyte membrane expands and contracts due to intrusion of generated water and a temperature change. The stress may cause inconvenience such as peeling at the interface between the electrolyte membrane and the gasket. In order to cope with this, Patent Document 1 describes that an elastic reinforcing member formed of the same material as that for forming the electrolyte membrane is disposed at the interface between the gasket and the electrolyte membrane.

  As a separator for use in a fuel cell, a single metal plate is not processed into a sheet metal, but a first member which is a porous metal member in contact with the electrode layer side of the membrane electrode assembly and a flat plate laminated on the first member A separator composed of a second member has also been proposed (see Patent Documents 2 and 3, etc.). Also in this case, a resin material that functions as a gasket is filled between the membrane electrode assembly and the peripheral edge of the first member of the separator, and between the protruding portion of the electrolyte membrane and the second portion of the separator, so that integration and sealing treatment are performed. Is given.

JP 2003-68318 A JP 2002-184422 A JP 2005-317322 A

  The peeling that is likely to occur at the interface between the electrolyte membrane and the resin material gasket caused by the expansion and contraction of the electrolyte membrane is the same as that of forming an electrolyte membrane at the interface between the two as described in Patent Document 1. It can be improved by arranging an elastic reinforcing member made of a material. However, a separate process for arranging such members is required.

  Moreover, as described in Patent Documents 2 and 3, as a separator, a first member which is a metal porous body member in contact with the electrode layer side of the membrane electrode assembly and a flat plate-like second member laminated on the first member In a fuel cell using a structured separator, when a gasket made of a resin material is formed around the resin cell, the resin material penetrates into the periphery of the first member, which is a metal porous body member, and the effective reaction area of the membrane electrode assembly is increased. There is a risk of narrowing.

  In addition, when forming a gasket made of a resin material, a primer (binding aid) mixed with a silane coupling agent is applied to the contact surface between the membrane electrode assembly or the separator and the gasket. The main bonding force is due to hydrogen bonding, and there is a problem with durability. In the experiments of the present inventors, peeling may occur at the joint location by operation for about 100 to 500 hours.

  The present invention has been made in view of the above circumstances, and as a separator, a first member which is a metal porous body member in contact with the electrode layer side of a membrane electrode assembly and a flat plate laminated on the first member. In the fuel cell using the separator constituted by the second member and the manufacturing method thereof, in particular, the joining mode between the first member and the membrane electrode assembly and the gasket which is a resin material for sealing the periphery thereof is improved. It is an object of the present invention to prevent the effective reaction area of the membrane / electrode assembly from being narrowed by the resin material that is filled around to form a gasket.

  In order to solve the above problems, a fuel cell according to the present invention includes a membrane electrode assembly having electrode layers on both sides of an electrolyte membrane, and separators laminated on both sides of the membrane electrode assembly, the separator being a membrane electrode A first member which is a metal porous body member in contact with the electrode layer side of the joined body and a flat plate-like second member laminated on the first member, and a peripheral edge of the membrane electrode assembly and the first member In the fuel cell having at least a configuration in which the periphery of the member is integrated and sealed with a gasket made of a resin material, an elastic primer is applied to at least the interface between the membrane electrode assembly and the resin material. It is characterized by being.

  In the fuel cell described above, the elastic primer functions as a layer that absorbs membrane shear stress caused by expansion and contraction of the electrolyte membrane, and can prevent delamination at the interface between the electrolyte membrane and the gasket. The process of applying the primer is a process conventionally performed at the time of joining the two members, and the number of processes is not increased at the time of manufacturing. As the primer having elasticity, a rubber-based primer can be exemplified.

  In a preferred aspect of the fuel cell according to the present invention, at least a region of the first member constituting the separator located at the periphery of the membrane electrode assembly is filled with the primer.

  In this aspect, the filled primer functions as a weir for the resin material constituting the gasket, and prevents the resin material from entering the inside of the first member in the surface direction during manufacturing. Thereby, it can be effectively avoided that the effective reaction area of the membrane electrode assembly becomes narrower than the design value.

  In a preferred embodiment of the fuel cell according to the present invention, the primer includes both a functional group that reacts with the material of the electrolyte membrane and a functional group that reacts with the resin material constituting the gasket, and between the primer and the electrolyte membrane, A chemical bond is formed both between the primer and the gasket (resin material).

  In this embodiment, a bond due to a chemical reaction is formed at the bonding interface, and a stable bonding with a long durability can be obtained as compared with a hydrogen bond formed at the bonding interface when a conventional primer is used. As a result, a fuel cell with improved durability and no cross leak is obtained. When the electrolyte membrane has sulfonic acid groups and the gasket is a silicone resin, examples of this type of primer include silicone rubber-based primers.

  In one aspect of the fuel cell according to the present invention, a recess is formed in one of the first members constituting the separator, and a part of the membrane electrode assembly is accommodated in the recess, and the other of the first members is It has a flat plate shape. According to this aspect, in the fuel cell having the above-described effects, a fuel cell in which the membrane electrode assembly is not displaced can be obtained.

  The present invention further includes a step of filling the primer in a region where the periphery of the membrane electrode assembly is located in one of the first members in which the recess is formed, The step of housing the membrane electrode assembly coated with the primer in the recess, the step of placing the first member coated with the primer on the periphery on the electrode assembly, and drying the laminate Also disclosed is a method of manufacturing a fuel cell, comprising at least a process and a process of integrating and sealing with a resin material constituting the gasket around the laminated body after drying. .

  By the above manufacturing method, a fuel cell having the above-described effects can be manufactured in a state where the membrane electrode assembly is not displaced.

  According to the present invention, a separator composed of a first member which is a porous metal member in contact with the electrode layer side of the membrane electrode assembly and a flat plate-like second member laminated on the first member is used as the separator. In the fuel cell, there can be obtained a fuel cell in which the interface bond between the gasket and the electrolyte membrane, which are resin materials, or the gasket and the first member is stable and the durability is greatly improved.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a schematic view showing in cross section three different forms of a fuel cell according to the present invention, and FIGS. 2 and 3 are diagrams for explaining still another form of the fuel cell according to the present invention together with its manufacturing method. FIG. 4 is a view for explaining an example of a joined state between the primer and each member in the fuel cell according to the present invention.

[First form]
1A, the fuel cell A1 includes a membrane electrode assembly 3 and separators 4 disposed on both sides thereof. The membrane electrode assembly 3 includes an electrolyte membrane 1 having proton conductivity having, for example, a sulfonic acid group as a proton exchange group, and an electrode layer 2 disposed on both sides thereof. The electrode layer 2 includes a catalyst layer formed of a catalyst mixture including an electrolyte resin and a catalyst-carrying conductor. A platinum-based metal is mainly used for the catalyst, and carbon powder is mainly used for a conductor supporting the catalyst. A diffusion layer made of carbon paper, carbon cloth, or the like is laminated on the outside of the catalyst layer, but may be omitted.

  The separator 4 includes a first member 5 that is a metal porous body member that contacts the electrode layer 2 side of the membrane electrode assembly 3, and a flat plate-like second member 6 that is laminated on the first member 5. . Specific examples of the first member 5 include a porous metal member having a knitted structure having conductivity and air permeability, such as an expanded metal or a metal mesh made of titanium, stainless steel, or aluminum. Specific examples of the second member 6 include a carbon material, which is a gas-impermeable conductive material, or a metal plate such as aluminum or stainless steel.

  The said 1st member 5 which comprises the separator 4 is laminated | stacked on both surfaces of the membrane electrode assembly 3, and it is set as the laminated body 10, and puts it in a shaping | molding die (not shown). The molding die is for molding a gasket 11 made of, for example, a silicone resin around the laminated body 10, and an injection molding apparatus is an example. When the laminated body 10 is set in the mold, at least in the region 1a where the electrolyte membrane 1 extends from the electrode layer 2 in the membrane electrode assembly 3, an elastic primer 20 (shown by a bold line in FIG. 1A) Apply). An example of the elastic primer 20 is a rubber-based primer. Preferably, a conventionally known silane coupling agent is mixed.

  After setting the laminated body 10 coated with the primer 20 in the cavity of the molding die, a resin material is injected and injected to form the gasket 11 around the laminated body 10. Thereby, the integration of the membrane electrode assembly 3 and the resin as the gasket 11 and the sealing for preventing the gas from flowing out from the side of the membrane electrode assembly 3 are performed. By laminating the second member 6 on the molded product and fixing it with an appropriate means, a fuel cell (single cell) A1 is obtained. Although not shown, the gasket 11 may be molded after the same or different primer is applied to other regions.

  FIG. 4A shows a joining state of the primer 20, the electrolyte membrane 1, and the silicone gasket 11 in the fuel cell (single cell) A1. Here, an electrolyte resin having a sulfonic acid group is used as the electrolyte membrane 1, and an addition-type silicone resin is used as the resin for the gasket 11. As shown in the figure, the electrolyte membrane 1 and the primer 20 and the gasket 11 and the primer 20 are joined by hydrogen bonding to exhibit a required bonding force between the electrolyte membrane 1 and the gasket 11. Furthermore, since the primer 20 has elasticity and is softer than the gasket 11, the primer layer functions as a membrane shear stress absorbing layer and prevents the separation at the interface between the electrolyte membrane 1 and the gasket 11. As a result, it is possible to avoid the occurrence of deterioration of the seal over a longer time than in the case of using a primer that does not have elasticity, and the life of the battery can be extended.

  As the primer 20 having elasticity, one having both a functional group that reacts with the material of the electrolyte membrane 1 and a functional group that reacts with the gasket 11 can be used. As an example of such a primer, a silane coupling agent having a functional group A chemically reacting with the sulfonic acid group of the electrolyte membrane 1 and a functional group B chemically reacting with the gasket 11 is added. Examples include silicone rubber-based primers. The joining state in the case of using such a silicone rubber-based primer is shown in FIG. 4B as before and after the reaction. As shown in the figure, in this case, a silane coupling agent having a functional group A that chemically reacts with the sulfonic acid group of the electrolyte membrane 1 is interposed between the electrolyte membrane 1 and the primer 20 as described above. In the primer 20, a silane coupling agent having a functional group B that chemically reacts with the gasket 11 is added to the primer 20 between the gasket 11 and the primer 20. The chemical reaction is caused by the inclusion. For this reason, a stronger bond can be formed at the interface between the two than the bonding by only hydrogen bonds, and the battery durability time is also increased. Examples of the functional group A include a vinyl group and an amino group. Examples of the functional group B include a vinyl group, a methacryl group, and a domemesyl group.

[Second form]
FIG. 1B shows a second embodiment of the fuel cell according to the present invention. This fuel cell A2 has, as a primer 20, a silane coupling having a functional group A that chemically reacts with the sulfonic acid group of the electrolyte membrane 1 and a functional group B that chemically reacts with the functional group that undergoes addition reaction with the gasket 11. A silicone rubber primer containing an agent is used, and the primer 20 is applied to the entire periphery of the membrane electrode assembly 3 including the periphery of the first member 5 constituting the separator 4. In this case, as shown in FIG. 4 (c), the functional group-containing primer 20 containing the silane coupling agent is bonded by a chemical reaction after heating in addition to hydrogen bonding by the silane coupling agent. In addition to the high interface bonding between the electrolyte membrane 1 and the gasket 11 described above, high and durable interface bonding between the gasket 11 and the first member 5 made of, for example, Ti constituting the separator 4. Can also be obtained.

[Third embodiment]
FIG.1 (c) shows the 3rd form of the fuel cell by this invention. The fuel cell A3 includes a primer (or the functional groups A and B) that has the elasticity in the first member 5 constituting the separator 4 in the region located at the periphery of the membrane electrode assembly 3 up to the inside thereof. This is different from the second embodiment in that it is filled with a primer 20 containing a silane coupling agent with

  As described in the first embodiment, when the fuel cell according to the present invention is manufactured, the laminate 10 in which the first member 5 constituting the separator 4 is laminated on both surfaces of the membrane electrode assembly 3 is placed in the cavity of the mold. Then, a resin material is injected and injected to form a gasket 11 around the laminate 10. In that case, there exists a possibility that the inject | emitted resin may enter into the peripheral part of the 1st member 5 which is the said metal porous body member. When the resin for forming the gasket enters the first member 5 as such, the effective reaction area of the membrane electrode assembly 3 becomes narrower than the design value.

  In the third embodiment, as described above, the region of the first member 5 located at the periphery of the membrane electrode assembly 3 is filled with the elastic primer 20a so as to enter the inside thereof, and the filled primer 20a functions as a weir (sealing material) for the resin to be infiltrated. Thereby, it can avoid effectively that the effective reaction area of the membrane electrode assembly 3 becomes narrower than a design value.

[Fourth form]
A fourth embodiment of the fuel cell according to the present invention will be described with reference to FIGS. In the fuel cell A4 of the fourth mode, a recess 7 is formed in one 5a of the first member 5 constituting the separator 4, and a part of the membrane electrode assembly 3 is accommodated in the recess 7, and the first The other member 5b of the one member 5 is different from the fuel cell A3 of the third embodiment in that it is flat.

  FIG. 2 illustrates the manufacturing process. First, using the same material as described above, the concave portion 7 is formed in the central portion to make one first member 5a. Next, the elastic primer 20a is applied and filled into the first member 5a along the outer periphery of the recess 7. Separately, a membrane electrode assembly 3 having an outer shape that enters the recess 7 is formed. The materials of the electrolyte membrane 1 and the electrode layer 2 constituting the membrane electrode assembly 3 may be the same as those described above. Preferably, as shown, a step is formed between the outer periphery of the upper electrode layer 2 and the outer edge of the electrolyte membrane 1. Then, the elastic primer (or a primer containing the silane coupling agent having the functional groups A and B) 20 is applied to the outer periphery of the membrane electrode assembly 3, preferably the step portion. The other 5b of the first member 5 is slightly smaller than the membrane electrode assembly 3, and is coated and filled with a primer 20a with a predetermined width from the outer periphery to the inside. The state is shown in FIG.

  Each of the above members is laminated as shown in FIG. The membrane electrode assembly 3 is positioned by entering the recess 7 of the lower first member 5a. On top of that, the upper first member 5b is laminated at a predetermined position. A drying process is performed in that state. At this time, the elastic primers 20 and 20a applied to or filled in each member function as a temporary fixing material between the vertically adjacent members and restrict free movement.

  After the laminated body 10 thus temporarily fixed is set in the cavity of the mold, a resin material is injected and injected to form a gasket 11 around the laminated body 10. A part of the molded fuel cell A4 is shown in FIG. The functions performed by the primers 20 and 20a are the same as those of the fuel cell A3 of the third embodiment. In FIG. 3, the second member 6 constituting the separator 4 is indicated by an imaginary line.

  In addition, in said 1st-4th form, although the rubber-type primer and the silicone rubber-type primer were shown as the primer 20 which has elasticity, this is an illustration and the primer which has elasticity in this invention is not restricted to this. Absent. The primer having a functional group is not limited to the silicone rubber primer containing the silane coupling agent having the functional groups A and B described above, and an electrolyte resin constituting the electrolyte membrane and a resin material constituting the gasket are used. In consideration thereof, an elastic primer having a functional group for them may be appropriately selected.

The present invention will be described with reference to examples and comparative examples.
[Example 1]
A fuel cell according to a fourth embodiment shown in FIG. 3 was manufactured by injection molding a silicone resin around the periphery of the laminate 10 and integrally molding the gasket 11. As the electrolyte membrane constituting the membrane electrode assembly, an electrolyte resin membrane having a sulfonic acid group was used, and an addition type silicone resin was used as the resin material of the gasket. As an elastic primer, a silicone rubber primer to which the silane coupling agent having functional groups A and B described above was added was used.

  The laminate in which the gasket was integrally formed was sandwiched between the second members 6 and 6 of the separator 4 to generate power as a single cell, and the durability of the seal was verified. As shown by the line a in FIG. 5, the initial seal strength (N / mm) was maintained even after 5000 hours of operation.

[Example 2]
A single cell was produced in the same manner as in Example 1 except that an elastic primer was used which was obtained by adding an arbitrary silane coupling agent having no functional groups A and B to a rubber primer. Thus, the durability of the seal was verified. As shown by the line b in FIG. 5, it was observed that the seal strength (N / mm) gradually decreased after almost 500 hours.

[Comparative example]
A single cell was produced in the same manner as in Example 1 except that a liquid silane coupling agent was used as a primer, and the durability of the seal was verified in the same manner. As indicated by the line c in FIG. 5, it was observed that the seal strength (N / mm) gradually decreased after almost 100 hours.

1A, 1B and 1C are schematic views showing in cross section three different forms of a fuel cell according to the present invention. The figure explaining further another form of the fuel cell by this invention with a manufacturing method. FIG. 3 is a schematic cross-sectional view showing a completed state of the fuel cell shown in FIG. 2. 4A, 4B, and 4C are views for explaining an example of a joining state between a primer and each member in the fuel cell according to the present invention. The graph which shows the relationship between the sealing strength and durability in an Example and a comparative example. The figure for demonstrating an example of a polymer electrolyte fuel cell.

Explanation of symbols

A1 to A4: Fuel cell, 1 ... Electrolyte membrane, 2 ... Electrode layer (catalyst layer), 3 ... Membrane electrode assembly, 4 ... Separator, 5 ... First member which is a porous metal member constituting the separator, 6 ... 2nd plate-shaped second member constituting the separator, 10 ... laminated body of membrane electrode assembly and first member, 11 ... gasket, 20, 20a ... primer having elasticity

Claims (6)

A membrane electrode assembly having electrode layers on both sides of the electrolyte membrane; and a separator laminated on both sides of the membrane electrode assembly, the separator being a porous metal member in contact with the electrode layer side of the membrane electrode assembly. 1 member and a flat plate-like second member laminated on the first member, and the peripheral edge of the membrane electrode assembly and the peripheral edge of the first member are integrated and sealed by a gasket made of a resin material. In a fuel cell comprising at least the applied configuration,
A primer having elasticity is applied to at least an interface between the membrane electrode assembly and the gasket ,
The primer includes both a functional group that reacts with the material of the electrolyte membrane and a functional group that reacts with the gasket, and a chemical bond is formed between the primer, the electrolyte membrane, and the gasket. A fuel cell.   2. The fuel cell according to claim 1, wherein at least a region of the first member located at a peripheral edge of the membrane electrode assembly is filled with the primer. Recess is formed in one of said first member, a portion of the membrane electrode assembly in the recess is accommodated, the other of the first member according to claim 1 or 2, wherein the tabular A fuel cell according to claim 1. The fuel cell according to any one of claims 1 to 3 , wherein the primer is a silicone rubber-based primer. A method of manufacturing a fuel cell according to claim 3 ,
Filling the primer in a region where a peripheral edge of the membrane electrode assembly in one of the first members in which the recess is formed;
A step of accommodating the membrane electrode assembly with the primer applied to the periphery in the recess;
Placing the other of the first members coated with the primer on the periphery on the membrane electrode assembly;
A step of drying the laminate, and
A method for producing a fuel cell, comprising at least a step of performing integration and sealing treatment with a resin material constituting the gasket around the laminated body after drying. 6. The method of manufacturing a fuel cell according to claim 5 , wherein a silicone rubber-based primer is used as the primer.

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