JP2006216294A - Fuel battery cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery capable of reducing its size. <P>SOLUTION: The fuel cell is constituted of a plurality of cells composed of an electrode-electrolyte film junction 1, on both surfaces of which gas diffusion layers 4a, 4b are arranged, and separators 2, 3 contacting the gas diffusion layers at a central part 11 of one face to demarcate gas flow passages of fuel gas or oxidant gas. Plate-shaped members 9 are arranged between the separator and the electrode-electrolyte film junction so as to surround the central part of the separator. When the separators and the electrode-electrolyte film junctions are laminated, a thickness of the plate-shaped member in a lamination direction is set so that a compression ratio as a rate of change of a thickness of a contact part of the gas diffusion layer to which the separator contacts in a thickness direction becomes a prescribed value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell and a manufacturing method thereof.

  A polymer electrolyte fuel cell generally comprises a pair of separators provided with ribs defining flow paths for fuel gas and oxidant gas on the surface, and an electrode-electrolyte membrane assembly provided with gas diffusion layers on both sides. A plurality of cells are stacked, and one side of the separator is provided with a coolant channel through which a coolant that dissipates heat generated by power generation by contacting one side of the other separator (Patent Document) 1).

  Each flow channel rib of the separator is in contact with the gas diffusion layer of the electrode-electrolyte membrane assembly, whereby electrons generated at the anode of the electrode-electrolyte membrane assembly pass through the gas diffusion layer, and a pair of plates It reaches the cathode via the gas diffusion layer of the adjacent electrode-electrolyte membrane assembly through the separator composed of At this time, the electric resistance of the path through which the electrons flow becomes the loss of the fuel cell as it is, and among them, the contact resistance of the surface where the members contact each other is particularly large. Moreover, there exists a tendency for resistance of this contact surface to become small, so that the contact surface pressure of members is large. For this reason, the polymer electrolyte fuel cell usually has a structure in which a constant load is applied in the stacking direction. Carbon paper or carbon cloth made of carbon fiber is usually used for the gas diffusion layer. Since these materials have relatively high elasticity, the gas diffusion layer is used in a state compressed to some extent by the laminating load. . However, since the gas diffusibility deteriorates when compressed excessively, the compression ratio needs to be kept in an appropriate range.

  For this reason, conventionally, a contact surface with a certain height is provided on the outer periphery of the separator, and this is brought into contact with the outer periphery of the electrode-electrolyte membrane assembly, thereby preventing excessive compression of the gas diffusion layer. Was common.

In addition, the outer periphery of each separator and electrode-electrolyte membrane assembly is usually provided with a seal member such as a lip type compression gasket or a liquid gasket to prevent the gas and coolant in the cell from flowing out. Yes.
JP 2004-247154 A

  Carbon paper and carbon cloth used for the gas diffusion layer have a relatively large thickness variation, so when compressed to a height that is regulated by the abutment surface of the outer periphery as in the conventional structure, the thickness is lower. In such a case, the compression ratio is insufficient, and the contact resistance with the flow path rib of the separator is increased. In the case of the upper limit product, the compression ratio is excessive and the gas diffusibility is lowered. As a result, there has been a problem that the power generation performance of the fuel cell is lowered.

  On the other hand, it is necessary to make the separator thinner in order to reduce the size of the fuel cell. For this reason, recently, there is a tendency to use a press-formed product of a metal thin plate instead of a carbon molded product that is limited in thickness in terms of strength and gas permeation. In this case, since the thickness of the press-formed product is constant, a free shape cannot be formed on the front and back. For this reason, unlike carbon molded products, there are significant restrictions in providing a guide shape for rectifying the flow and a shape for preventing the gasket from protruding into the flow path when a liquid gasket is used for the seal.

  Accordingly, an object of the present invention is to provide a fuel cell capable of achieving both size reduction and power generation performance.

The present invention comprises an electrode-electrolyte membrane assembly provided with gas diffusion layers on both sides,
A separator that is in contact with the gas diffusion layer in the center of one surface and that defines a gas flow path of fuel gas or oxidant gas;
In a fuel cell configured by stacking a plurality of cells made of
Between the separator and the electrode-electrolyte membrane assembly, provided is a plate-like member disposed so as to surround the central portion of the separator,
The thickness in the laminating direction of the plate member is the rate of change in the laminating direction thickness of the contact portion of the gas diffusion layer that contacts the separator when the separator and the electrode-electrolyte membrane assembly are laminated. It is set so that a certain compression ratio becomes a predetermined value.

  In the present invention, the thickness of the plate-like member is adjusted so that the compression rate of the gas diffusion layer becomes a predetermined value according to the variation between the separator and the electrode-electrolyte membrane assembly. Thus, the power generation performance of the fuel cell can be properly exhibited.

  The fuel cell structure of the present invention shown in FIGS. 1 and 2 is a cell structure of a polymer electrolyte fuel cell using a metal sheet press-molded product as a separator. FIG. 1 is a plan view of the fuel cell, and FIG. 2 is a cross-sectional view (cross section AA) of the fuel cell.

  The fuel cell S includes an electrode-electrolyte membrane assembly (hereinafter referred to as MEA) 1, an anode separator 2 and a cathode separator 3 that sandwich the MEA 1, and a gas diffusion layer installed between each separator 2, 3 and the MEA 1. 4a and 4b. The fuel cell is usually used as a stack structure in which a plurality of cells S are stacked.

  Each of the separators 2 and 3 is formed in a corrugated shape in the central region 11 facing the gas diffusion layers 4a and 4b. According to FIG. 2, the corrugated convex portion 2a is formed on the anode side gas diffusion layer of the MEA 1. The hydrogen flow path 5 through which hydrogen (or hydrogen-rich reformed gas) flows is partitioned by contacting with 4a. Also, the coolant channel 7 through which the coolant flows is formed by contacting the recess 2b of the anode separator 2 with the projection 3a of the cathode separator 3 of another cell S adjacent thereto. The recess 3b of the cathode separator 3 forming the coolant channel 7 is in contact with the cathode side gas diffusion layer 4b of another adjacent cell S to form an air channel 6 through which air (or oxygen) flows.

  In this way, hydrogen and air are supplied to the flow paths 5 and 6 from a compressor and a high-pressure tank (not shown), supplied to each electrode of the MEA 1 through the gas diffusion layers 4 provided on both sides of the MEA 1, and used for power generation. Is done. A coolant such as water is circulated in the coolant channel 7 in order to cool the cell S heated by the heat generated by the power generation.

  In the anode of the MEA 1 configured as described above, the hydrogen supplied from the hydrogen flow path 5 through the gas diffusion layer 4a releases electrons and ionizes, and the ionized hydrogen reaches the cathode through the electrolyte membrane. At the same time, the electrons pass through the gas diffusion layer 4a, the anode separator 2 and the cathode separator 3, and further reach the cathode of the adjacent MEA 1 via the cathode side gas diffusion layer 4b of the adjacent MEA 1.

  On the other hand, at the cathode electrode, hydrogen ions and electrons that have passed through the electrolyte and oxygen contained in the air supplied from the air flow path 6 chemically react to generate water, and the generated water is discharged from the cathode separator 2.

  In addition, the gas diffusion layer 4 is disposed at a position facing the central region 11 of each separator 2 and 3, and no chemical reaction occurs in the outer region, and therefore there is a region that does not contribute to the chemical reaction in the outer peripheral portion of the MEA 1. In this region, a resin frame 8 for fixing the gas diffusion layer 4 is provided. A plate-like member 9 is disposed between the frame 8 and the separators 2 and 3 and between the separators forming the coolant channel 7, and each fluid is leaked so as to surround the plate-like member 9. A liquid gasket 10 is disposed as a sealing material to prevent.

  The cell S is loaded in the stacking direction, and the contact portion of the gas diffusion layer 4 is compressed by the separators 2 and 3 by this load. When the plate-like member 9 comes into contact with the frame 8 and the separators 2 and 3, the compression amount of the contact portion of the gas diffusion layer 4 is regulated. The compression amount of the gas diffusion layer 4 is determined by the thickness of the gas diffusion layer 4, the thickness of the frame 8, and the height of the separators 2 and 3 in the hydrogen flow path 5 and the air flow path 6. However, each of these dimensions has a manufacturing variation, and especially the manufacturing variation of the thickness of the gas diffusion layer 4 is large. On the other hand, in the present invention, a plurality of plate-like members 9 having different thicknesses are prepared in advance at the time of assembly, depending on the thickness of each gas diffusion layer 4 and the thickness of the frame 8 and the height of the separators 2 and 3. The thickness of the plate member 9 is selected so that the compressibility of the gas diffusion layer 4 (= thickness change rate relative to the thickness before contact in the stacking direction of the gas diffusion layer 4) becomes a predetermined value. Assemble. As a result, an appropriate contact surface pressure between the separators 2 and 3 and the gas diffusion layer 4 is ensured to reduce contact resistance, and deterioration of gas diffusion due to excessive compression of the gas diffusion layer 4 is prevented, and power generation efficiency is improved. A decrease can be prevented.

Therefore, the manufacturing process of the fuel cell of the present invention is as follows.
1. The thickness of the MEA 1, the thicknesses of the separators 2 and 3 and the height in the central region 11, the thickness of the gas diffusion layer 4, and the thickness of the frame 8 are measured (note that the measured thickness and height are the stacking direction) Dimensions).
The plate-like member 9 having a different thickness is prepared in accordance with the variation in the measurement result of item 2.1.
3. The gas diffusion layer 4 in which the above-described structural members (excluding the plate-like member 9) such as the thickness constituting the fuel cell are selected and the separators 2 and 3 are in contact with each other when the cells are stacked from the dimensions of the selected structural members. A plate-like member 9 having a thickness at which the compression ratio becomes a predetermined value is selected.
4). The selected components are installed from below, for example, as shown in FIG. Similarly, between the anode separator 2 and the cathode separator 3, the thickness of the plate-like member 9 is determined in accordance with the measured height of each separator 2, 3 so that the anode separator and the cathode separator 3 are reliably in contact with each other. Select and install. At this time, the plate-like member 9 is selected so that there is no leakage in each coolant channel 7. Accordingly, the separators 2 and 3 are appropriately brought into contact with each other to reduce contact resistance, and a gap is not generated, so that stable lamination can be performed.
5. A liquid gasket 10 is disposed between the frame 8 and the separators 2 and 3 and between the separators 2 and 3.
6). In this procedure, a predetermined number of cells S are stacked and tightened by applying a predetermined pressure to each cell S with bolts and nuts that apply a load in the axial direction (not shown) to assemble the fuel cell. Complete.

  Further, sealing means for preventing leakage of fluid flowing through these flow paths is provided on the outer periphery of the hydrogen flow path 5, the air flow path 6 and the coolant flow path 7 so as to surround these flow paths. Is normal. However, in this embodiment, the liquid gasket 10 is used on the outer periphery of the plate-like member 9 as this sealing means, and fluid is prevented from leaking from each flow path to the outside through the plate-like member 9. The liquid gasket 10 is used by being crushed between upper and lower members after being applied to each separator 2, 3 or frame 8. When it is crushed and brought into close contact, it spreads in the lateral direction, and if the expanded portion protrudes and hardens, it may interfere with the flow of fluid. However, in the present invention, the plate-like member 8 serves as a weir, and this extra liquid gasket can be prevented from flowing into the hydrogen flow path 5, the air flow path 6 and the coolant flow path 7.

  On the other hand, the inside of each plate-like member 9 is hollowed out, and the inner peripheral end 9a facing each flow path has a central region 11 and each for supplying fluid to the central region 11 as shown in FIG. Manifold holes 12 to 14 for each fluid are formed, and a diffuser portion 15 for communicating these is formed, and this diffuser portion 15 has a guide shape for rectifying the fluid. Thereby, the fluid can be smoothly supplied from the manifold holes 12 to 14 to the central region 11.

  The surfaces of the separators 2 and 3 on which the coolant channels 7 are formed are uniform in the thickness of the separators 2 and 3 when a metal thin plate press-formed product is used for the separators 2 and 3 as in this embodiment. For this reason, it is difficult to form a guide shape like the diffuser portion 15 on both surfaces of the separators 2 and 3. However, in the present invention, since the guide shape is constituted by a member (a plate-like member 9) different from the separators 2 and 3, an appropriate shape can be obtained. Further, since the upper and lower surfaces of the guide shape are in contact with the separators 2, 3 or MEA 1 without a gap, the fluid can be rectified more reliably.

  FIG. 3 shows a cross-sectional view of the fuel cell according to the second embodiment. In the present embodiment, a plate-like member similar to that of the first embodiment is used, and both sides of the plate-like member are bonded to the outer peripheral portions of the separators 2 and 3 or the resin frame 8 with an adhesive to provide a sealing function. It is a configuration. Thereby, since it is not necessary to provide sealing means dedicated to the sealing function (the liquid gasket 10 described above), the size of the cell can be reduced.

  Therefore, in the present invention, the thickness of the plate-like member 9 in the stacking direction is changed, and the contact portion of the gas diffusion layer 4 that contacts the separators 2 and 3 when the separators 2 and 3 and the MEA 1 are stacked is stacked. Since the compression rate, which is the rate of change of the thickness in the direction, is set to a predetermined value, the power generation performance of the fuel cell can be appropriately exhibited while maintaining the compression rate of the gas diffusion layer 4 at a predetermined value.

  Since the plate-like member is provided between the adjacent separators 2 and 3 so that the refrigerant flow path is formed, the refrigerant flow path can be easily provided and the leakage of the refrigerant can be prevented.

  The central region 11 of the separators 2 and 3 is formed in a corrugated shape in which convex portions 2a and 3a and concave portions 2b and 3b are formed on the upper and lower sides, and one surface of the gas diffusion layer 4 is in contact with one of the convex portions 2a. Since the flow path 5 is defined and one of the convex portions 3a of the separator 3 of another cell S adjacent to the other concave portion 2b is in contact with each other to form the coolant flow path 7, the gas flow paths 5 and 6 and the coolant flow are easily obtained. A path 7 can be formed.

  The plate-like member 9 is formed in a hollow shape so that the gas or refrigerant from each of the manifolds 12 to 14 that supplies gas or refrigerant to the flow paths 5 to 7 is supplied to the gas flow paths 5 and 6 or the coolant flow path 7. Therefore, the flow path can be easily formed.

  Since the liquid gasket 10 that secures the sealing performance of each of the flow paths 5 to 7 is provided on the outside of the plate-like member 9, the plate-like member 9 suppresses the liquid gasket 10 from protruding into each flow path, and the sealing performance. Can be secured.

  Moreover, since the sealing property is secured by bonding the plate-like member 9 and the separators 2 and 3 and between the plate-like member 9 and the MEA 1 with an adhesive, there is no need to provide a component for sealing. The dimensions of the cell S can be reduced.

  Furthermore, in the present invention, a plurality of plate-like members 9 surrounding the central portion 11 of the separators 2 and 3 are provided with different thicknesses in the stacking direction, the thickness of the gas diffusion layer 4 in the stacking direction, and the stacking direction of the separators 2 and 3 And measuring the thickness of the central portion 11 and the measured dimensions of the gas diffusion layer 4 and the separators 2 and 3, the gas diffusion layer 4 and the separators 2 and 3 are stacked when the gas diffusion layer 4 and the separators 2 and 3 are laminated. Selecting a plate-like member 9 so that the compression rate, which is the rate of change in thickness in the stacking direction of the gas diffusion layer 4 at the contact portion of the separators 2 and 3, becomes a predetermined value. Therefore, the power generation performance of the fuel cell can be properly exhibited while maintaining the compression ratio of the gas diffusion layer at a predetermined value.

It is a fuel cell cell top view of the present invention. It is a fuel cell sectional view similarly (section AA of Drawing 1). It is fuel cell sectional drawing of 2nd Embodiment.

Explanation of symbols

1: MEA
2: Anode separator 3: Cathode separator 4: Gas diffusion layer 5: Anode separator gas flow path 6: Cathode separator gas flow path 7: Coolant flow path 8: Frame 9: Plate member 10: Liquid gasket 11: Central region 12: Hydrogen manifold hole 13: Coolant manifold hole 14: Air manifold hole 15: Diffuser section

Claims (7)

An electrode-electrolyte membrane assembly having gas diffusion layers on both sides;
A separator that is in contact with the gas diffusion layer at the center of one surface and defines a gas flow path of fuel gas or oxidant gas;
In a fuel cell configured by stacking a plurality of cells made of
Between the separator and the electrode-electrolyte membrane assembly, provided is a plate-like member disposed so as to surround the central portion of the separator,
The thickness in the laminating direction of the plate member is the rate of change in the laminating direction thickness of the contact portion of the gas diffusion layer that contacts the separator when the separator and the electrode-electrolyte membrane assembly are laminated. A fuel cell characterized in that a certain compression ratio is set to a predetermined value. The other surface of the separator defines a coolant channel with the other surface of the other separator,
The plate member is provided between the separators,
2. The fuel cell according to claim 1, wherein a thickness of the plate-shaped member in a stacking direction is set so that the separators are in contact with each other to define the refrigerant flow path.   The central portion of the separator is formed in a corrugated shape with convex portions formed on the top and bottom, and one surface of the gas diffusion layer is in contact with one convex portion to define the gas flow path, and adjacent to the other convex portion. 3. The fuel cell according to claim 1, wherein one of the protrusions of the separator of the other cell that is in contact with each other forms the refrigerant flow path.   The plate-like member is formed in a hollow shape so that the gas or refrigerant from each manifold that supplies the gas or the refrigerant to the flow path is supplied to the gas flow path or the refrigerant flow path. The fuel cell according to claim 1 or 2.   4. The fuel cell according to claim 2, wherein a liquid gasket is provided so as to enclose the gas flow path and the refrigerant flow path so as to surround the plate-shaped member.   The seal between the plate member and the separator and between the plate member and the electrode-electrolyte membrane assembly is secured by an adhesive to ensure sealing performance. The fuel cell as described. An electrode-electrolyte membrane assembly having gas diffusion layers on both sides;
A separator that is in contact with the gas diffusion layer in the center of one surface and that defines a gas flow path of fuel gas or oxidant gas;
In a fuel cell configured by stacking a plurality of cells made of
Provide a plurality of plate-like members surrounding the central portion of the separator so that the thickness in the stacking direction is different,
Measuring the thickness of the gas diffusion layer in the stacking direction, the thickness of the separator in the stacking direction, and the height of the central portion;
From the measured dimensions of the gas diffusion layer and the separator, when the gas diffusion layer and the separator are laminated, the compressibility is a rate of change in thickness in the stacking direction of the gas diffusion layer at the contact portion with the separator Selecting the plate-like member so that becomes a predetermined value;
Disposing the selected plate-shaped member between the separator and the electrode-electrolyte membrane assembly provided with the gas diffusion layer having a predetermined compression rate.
A method for producing a fuel cell, comprising:

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