JP2007299673A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell stack which can improve an output density. <P>SOLUTION: The fuel cell stack is composed of a reaction part which divides and forms a gas passage 6 or an oxidant gas passage 7 with separators 12, 13 making a conductive corrugated metal plate to contact an anode 11b or a cathode 11c and a sealing part which surrounds the reaction part and is provided with a seal 14 to secure a sealing property between an electrolyte membrane/electrode assembly. The seal bonds the electrolyte/electrode assembly with the separator and a rigidity of the seal in a lamination direction is larger than a rigidity of a lamination direction of the reaction part of the separator, and the sealing part is arranged within a range of a height of a corrugation of the reaction part in a lamination direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell stack.

  An ordinary polymer electrolyte fuel cell has an electrolyte membrane / electrode structure (hereinafter referred to as a polymer ion exchange membrane) that is configured such that a polymer ion exchange membrane is sandwiched between both sides of a polymer ion exchange membrane (cation exchange membrane). And MEA) are further sandwiched between separators. The fuel gas (hydrogen-containing gas) supplied to the anode is hydrogen-ionized on the catalyst electrode, and moves to the cathode through an electrolyte membrane that is appropriately humidified. Electrons generated in the meantime are taken out to an external circuit and used as direct current electric energy. Since an oxidant gas such as an oxygen-containing gas or air is supplied to the cathode, the hydrogen ions, the electrons, and the oxygen gas react with each other to generate water at the cathode. The chemical formula showing the above reaction is as follows (see Patent Document 1).

Anodic reaction: H ₂ → 2H ⁺ + 2e ⁻ (1)
Cathodic reaction: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)
One set of the polymer electrolyte fuel cells is called a unit cell. A fuel cell stack is configured by stacking a predetermined number of unit cells.

  Further, in order to prevent leakage of supplied gas to the outside and mixing of gas, a liquid sealing material is applied between the MEA and the separator, or between each separator, and the outside of the gas from each gas flow path, or There is a technology for preventing leakage to other gas flow paths and ensuring sealing performance.

  Technologies for improving the output density and productivity of such fuel cell stacks are being researched every day. For example, as an example of means for improving the output density, metal is used to reduce the cell pitch, which is the stacking interval of single cells. In order to increase the area of the active area where the separator or the above-described reaction occurs, there is a technique for reducing the area of the seal portion which is an inactive area.

  As an example of the improvement in productivity, there is a technique of modularization of a single cell as shown in Patent Document 2. The technology of Patent Document 2 is to modularize an MEA and a separator sandwiching the MEA using an adhesive, and the adhesive used for modularization has elasticity even after curing, and as a spacer between separators An adhesive in which functional spherical beads are mixed into the adhesive.

Even after such curing, the MEA thermal expansion can be allowed by using an elastic adhesive, and electrical shorting between separators can be prevented by mixing beads as spacers into the adhesive. Can do.
JP-A-8-106914 JP 2002-352845 A

  However, in the technique described in Patent Document 2, if the beads as a spacer enter the active area between the separator and the MEA, the beads may damage the MEA due to the fastening load at the time of stacking the single cells. There is a problem that it is necessary to secure a sufficient seal area so as not to enter, and the fuel cell is increased in size and the output density is reduced.

  Accordingly, an object of the present invention is to provide a fuel cell stack capable of improving the power density.

  The present invention relates to an electrolyte membrane / electrode structure comprising a solid polymer electrolyte membrane, an anode and a cathode sandwiching the solid polymer electrolyte membrane, and sandwiching the electrolyte membrane / electrode structure, the anode and the cathode In the fuel cell stack configured by laminating a single cell composed of a fuel gas flow path through which a fuel gas and an oxidant gas are supplied and a pair of separators that form an oxidant gas flow path, the separator is A conductive metal plate press-molded into a corrugated shape so as to contact the anode or the cathode to surround the reaction part defining the fuel gas flow path or the oxidant gas flow path, A seal portion provided with a seal that ensures sealing performance between the electrolyte membrane / electrode structure, and the seal includes the electrolyte membrane / electrode structure and the separator. The rigidity in the stacking direction of the seal is greater than the rigidity in the stacking direction of the reaction part of the separator, and the seal part is within the height range of the corrugated shape of the reaction part in the stacking direction. Installed.

  In the present invention, without using beads as in the prior art, positioning between the electrolyte membrane / electrode structure and the separator is performed with a seal that is stiffer than the reaction portion, and the electrolyte membrane By permitting the deformation of the electrode structure, it is possible to suppress the expansion of the seal portion and improve the output density.

  FIG. 1 is a perspective view showing a fuel cell stack 1, and FIG. 2 is a front view of the same. The fuel cell of this embodiment is a solid polymer electrolyte fuel cell mounted on a vehicle, for example.

  The stack 1 is a stacked battery including a cell stack 10a in which a predetermined number of single cells 10 as unit batteries that generate electromotive force are stacked. Each single cell 10 is formed as a polymer electrolyte fuel cell, and each single cell 10 generates an electromotive voltage of about 1V.

  In the stack 1, current collector plates 2 are installed at both ends of the cell stack 10 a, and end plates 4 are arranged via insulating plates 3. Furthermore, the stack 1 includes a tension rod 5 that tightens the cell stack 10a in the stacking direction.

  The current collector plate 2 is formed of a gas-impermeable conductive member such as dense carbon or copper plate, and the electromotive force generated by the cell stack 10a composed of the single cells 10 connected in series is It is supplied to a load (not shown) connected to the terminal 2a.

  The insulating plate 3 is formed of an insulating member such as rubber or resin, and ensures insulation between the current collector plate 2 and the end plate 4.

  The end plate 4 is made of a material having rigidity, for example, a metal material such as steel.

  The current collector plate 2, the insulating plate 3, and the end plate 4 are formed with through holes that communicate with a fuel gas flow path 6, an oxidant gas flow path 7, and a cooling medium flow path 8 of a single cell 10 described later.

  The tension rod 5 fastens the cell stack 10a in the cell stacking direction so that a predetermined pressure acts on each single cell 10. The tension rod 5 is formed in a bolt shape, is inserted into a through-hole penetrating the corner of the cell laminate 10a, and a nut is screwed into a screw portion formed at the end of the tension rod 5, whereby the cell laminate 10a. Tighten in the stacking direction. The tension rod 5 is formed of a material having rigidity, for example, a metal material such as steel, and has a structure in which the surface is insulated in order to prevent an electrical short circuit between the single cells 10.

  Note that the cell stack 10a is not tightened by passing the tension rod 5 through the inside of the cell stack 10a, but by placing the tension rod 5 outside the stack 1 and sandwiching the end plates 4 sandwiching the cell stack. A mechanism for tightening with the tension rod 5 may be used.

  Further, a second end plate is additionally arranged between one end plate 4 and the insulating plate 2 adjacent to the end plate 4, and a spring or the like is provided between the one end plate 4 and the second end plate. A mechanism may be provided in which a pressurizing device is installed and the second end plate and the other end plate 4 are tightened by the tension rod 5, and the present invention is not limited to these pressurizing methods, and other methods may be used. .

  FIG. 3 is a partial cross-sectional view of the cell stack 10a showing the configuration of the separator according to the first embodiment of the present invention.

  The single cell 10 includes an MEA 11, an anode separator 12 that sandwiches the MEA 11, and a cathode separator 13.

  The MEA 11 is disposed so as to face an electrolyte membrane 11a made of an ion exchange membrane, one surface of the electrolyte membrane 11a, an anode (fuel electrode) 11b made of a gas diffusion layer, a water repellent layer, and a catalyst layer, and the electrolyte membrane 11a. The cathode (air electrode) 11c is disposed facing the opposite surface and is composed of a gas diffusion layer, a water repellent layer, and a catalyst layer.

  The electrolyte membrane 11a is a proton conductive ion exchange membrane formed of a solid polymer material such as a fluorine resin, and exhibits good electrical conductivity in a predetermined wet state.

  The anode 11b and the cathode 11c are gas diffusion electrodes, and are composed of a gas diffusion layer, a water repellent layer, and a catalyst layer. The gas diffusion layer is constituted by a member having appropriate gas diffusibility and conductivity, such as carbon cloth woven with yarn made of carbon fiber, carbon paper, or carbon felt. The water repellent layer is a layer containing, for example, polyethylene fluoroethylene and a carbon material, and the catalyst layer is made of carbon black carrying platinum.

  According to FIG. 3, the anode separator 12 defines a fuel gas flow path 6 through which fuel gas flows in contact with the anode 11 b, a reaction portion formed in a waveform from the top portion 12 a and the bottom portion 12 b, and the reaction portion Is formed of a planar seal portion 12c provided with a seal 14 that prevents the fuel gas flowing through the reaction portion from leaking to the outside. The seal portion 12c is disposed between the top portion 12a and the bottom portion 12b of the reaction portion at a distance from the MEA 11 in the stacking direction, and seals between the anode separator 12 and the MEA 11 (the holding portion of the electrolyte membrane 11a). 14 is installed. The seal 14 is an adhesive that secures a sealing property between the anode separator 12 and the MEA 11, and this adhesive has an insulating property, and the rigidity in the stacking direction after curing is the sealing portion 12 c of each separator 12, 13. , 13c, an adhesive characterized by being higher than the rubber seal 15 is used, for example, an epoxy adhesive. By using such a highly rigid seal 14, it is possible to prevent an electrical short circuit between the single cells.

  The rubber seal 15 uses, for example, a silicon-based or fluorine-based rubber material, and prevents leakage of the refrigerant from the refrigerant flow path 8 formed between the separators 12 and 13 to the outside. Note that the space required for the seal portions 12c and 13c is minimized by arranging the seal 14 and the rubber seal 15 so that the center position of the seal 14 and the center position of the rubber seal 15 substantially coincide with each other when viewed from the stacking direction. Can be improved, the output density of the fuel cell can be improved.

  The surface roughness of the seal portions 12c and 13c of the separators 12 and 13 to which the seal 14 is applied is set to be rougher than the surface roughness of the reaction portion, so that the seal 14 is adhered to the surfaces of the seal portions 12c and 13c due to the wedge effect. Can do.

  The bottom 12b of the anode separator 12 is in contact with the anode 11b of the MEA 11, and defines a fuel gas flow path 6 for supplying fuel gas (hydrogen) to the anode 11b. Further, the refrigerant flow path 8 in which the refrigerant that radiates heat of the single cell 10 flows between the top part 12a of the anode separator 12 and the top part 13a of the cathode separator 13 with the top part 12a in contact with the bottom part 13b of the adjacent cathode separator 13. Is defined.

  Similarly to the anode separator 12, the cathode separator 13 also defines an oxidant gas flow path 7 through which the oxidant gas flows in contact with the cathode 11c, and a reaction portion formed in a waveform from the top portion 13a and the bottom portion 13b. The seal portion 13c is provided in which a seal 14 formed around the reaction portion and preventing the oxidant gas flowing through the reaction portion from leaking to the outside is installed. The seal portion 13c is disposed between the top portion 13a and the bottom portion 13b of the reaction portion at a distance from the MEA 11 in the stacking direction, and the seal 14 is formed between the cathode separator 13 and the MEA 11 (the holding portion of the electrolyte membrane 11a). Installed between.

  The top portion 13a of the cathode separator 13 is in contact with the cathode 11c of the MEA 11, and defines an oxidant gas flow path 7 for supplying an oxidant gas (oxygen, usually air) to the cathode 11c.

  Each of the separators 12 and 13 is formed by press working using, for example, a thin metal plate material having appropriate conductivity, strength, and corrosion resistance. The press-molded separators 12 and 13 have a corrugated shape as described above, and the rigidity in the stacking direction, particularly the rigidity of the reaction part, is suppressed to be lower than that of the adhesive as the seal 14. For this reason, even if the MEA 11 is deformed after bonding the seal 14 as shown in FIG. 5 described later, the deformation of the MEA 11 can be allowed by the deformation of the separators 12 and 13.

  The anode 11b and the cathode 11c are arranged up to the vicinity of the seal portions 12c and 13c, and the reaction portion is laid out as large as possible. Specifically, as shown in FIG. 3, it is set from the center of the fuel gas passage 6 or the oxidant gas passage 7 adjacent to the seal portions 12c and 13c to the seal portion side.

  FIG. 4 is a diagram for explaining the positional relationship in the stacking direction of the seal portion of the separator. The seal portion is disposed so as to be positioned between the top and bottom of each separator in the stacking direction, from the surface of the electrode film 11a. The distance L to the seal portions 12c and 13c is expressed by the following formula.

Here, H1: the height in the stacking direction of each separator, that is, the distance from the top of the anode separator or cathode separator to the bottom of the separator,
H2: Distance in the stacking direction from the end of the separator far from the MEA to the seal portion, that is, the distance from the seal portion of the anode separator or cathode separator to the bottom of the separator (H1> H2),
t2: The thickness of the anode or cathode in the fuel cell stack state. The distance L is preferably set so as to be separated from the anode 11b or the cathode 11c in the stacking direction after satisfying the above equation.

  FIG. 5 is a diagram for explaining the effect of the forming method of the single cell 10 and the corrugated separator.

  In (a), it arrange | positions so that MEA11 may be pinched | interposed between the anode separator 12 and the cathode separator 13, the adhesive agent as the seal | sticker 14 may be apply | coated between the anode separator 12, the cathode separator 13, and MEA11, and MEA11 may be predetermined | prescribed. It clamps with the load F and waits for the seal | sticker 14 to harden | cure with the clamped state maintained. The single cell 10 is formed by bonding the separators 12 and 13 and the MEA 11 using the seal 14.

  After the adhesive as the seal 14 is cured, when the load F is removed, the thickness of the anode 11b and the cathode 11c increases from t2 to t1 as shown in FIG. However, since the adhesive as the seal 14 used for forming the single cell 10 uses a highly rigid adhesive after curing, the deformation accompanying the increase in the thickness of the anode 11b and the cathode 11c is caused by the separators 12, Absorbs 13 by bending. Accordingly, the shape, material, thickness, and the like of the separators 12 and 13 are determined so that the rigidity in the stacking direction of the separators 12 and 13 is set lower than the spring characteristics in the stacking direction of the anode 11b and the cathode 11c. The rigidity of the seal 14 after curing is set to be higher than the rigidity in the stacking direction of the anode 11b and the cathode 11c. Here, the thickness t2 of the anode 11b and the cathode 11c corresponds to the thickness in the state of the fuel cell stack 1.

  Therefore, in the present invention, the reaction part of the separator is formed into a corrugated shape to allow deformation of the MEA 11, and by using a highly rigid adhesive as a seal, the distance between the MEA 11 and each separator is maintained. There is no need to use beads as in the prior art, and the area of the seal portion can be suppressed and the output density of the fuel cell stack can be improved.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

It is a perspective view of a fuel cell stack. It is a front view of a fuel cell stack. It is a partial cross section figure of the cell laminated body which shows the structure of a separator. It is a figure explaining the position of the seal part of a separator. It is a figure explaining the shaping | molding method of a single cell, and the effect of a waveform-shaped separator.

Explanation of symbols

6: Fuel gas flow path 7: Oxidant gas flow path 8: Refrigerant flow path 10: Single cell 11: MEA
11a: electrolyte membrane 11b: anode 11c: cathode 12: anode separator 12a: top 12b: bottom 13: cathode separator 13a: top 13b: bottom 14: seal 15: rubber seal

Claims (6)

An electrolyte membrane / electrode structure comprising a solid polymer electrolyte membrane and an anode and a cathode sandwiching the solid polymer electrolyte membrane;
The electrolyte membrane / electrode structure is sandwiched between the fuel gas flow path for the fuel gas and the oxidant gas supplied to the anode and the cathode, and a pair of separators that form the oxidant gas flow path. In a fuel cell stack configured by stacking single cells,
The separator is
A reaction part that defines the fuel gas flow path or the oxidant gas flow path by contacting a conductive metal plate pressed into a corrugated shape with the anode or the cathode;
A seal portion that surrounds the reaction portion and is provided with a seal that ensures sealing performance between the electrolyte membrane and the electrode structure;
The seal adheres the electrolyte membrane / electrode structure and the separator, and the rigidity in the stacking direction of the seal is larger than the rigidity in the stacking direction of the reaction part of the separator,
The fuel cell stack according to claim 1, wherein the seal portion is disposed within a height range of the corrugated shape of the reaction portion in a stacking direction.   2. The fuel cell stack according to claim 1, wherein the seal portion is installed at a predetermined distance L from the electrolyte membrane / electrode structure in the stacking direction. The fuel cell stack according to claim 2, wherein the predetermined distance L is calculated by the following equation.
Here, H1: height of each separator in the stacking direction,
H2: From the end of the separator far from the electrolyte membrane / electrode structure to the seal
Distance in the stacking direction (H1> H2),
t2: The thickness of the anode or the cathode in the fuel cell stack state. A refrigerant flow path for flowing a refrigerant for controlling the temperature of the fuel cell stack is formed between the pair of separators, and is made of a rubber material so that the refrigerant does not leak outside along the outer edge of the refrigerant flow path. Place the rubber seal,
2. The fuel cell stack according to claim 1, wherein the rigidity of the seal in the stacking direction is greater than the rigidity of the rubber seal in the stacking direction.   2. The fuel cell stack according to claim 1, wherein the seal and the rubber seal are arranged so as to substantially coincide with each other when viewed from the stacking direction.   6. The fuel cell stack according to claim 1, wherein a surface roughness of the seal portion is rougher than a surface roughness of the reaction portion.