JP2007179992A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell stack which can prevent a metal current collector from coming into contact with cooling water and a reaction gas and is simple in structure. <P>SOLUTION: A film electrode complex 1 has gas diffusion electrodes on both sides of a solid polymer film. Gas separators 2, 3 have a fuel gas passage and an oxidizer gas passage 4 at least on one sides of themselves, where the fuel gas passage and the oxidizer gas passage 4 supply a fuel gas and an oxidizer gas to the gas diffusion electrodes, respectively. The film electrode complex 1 and the separators 2, 3 are arranged so that the fuel gas passage comes into contact with one side of the gas diffusion electrode and the oxidizer gas passage comes into contact with the other side of the gas diffusion electrode, and make up a basic structure element. A laminate is made up of a plurality of the basic structure elements and sandwiched/held by end plates 20 made up of a conductive inner plate 21, and an insulative outer plate 22. Further, a generated current of the fuel cell stack is extracted through the conductive plate 21, and the end plate is formed so that a fluid to be supplied/removed to/from the fuel cell stack comes into contact only with the insulative outer plate 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte fuel cell stack using a solid polymer having ion conductivity as an electrolyte, and more particularly to a fuel cell stack in which the structure of the end portion is improved.

  A fuel cell stack using a solid polymer electrolyte membrane having proton conductivity as an electrolyte is generally provided with gas flow passages on both sides of a membrane electrode assembly (MEA) in which the electrolyte membrane is sandwiched between a fuel electrode and an oxidant electrode. A single cell battery is configured by arranging electrically conductive separators, and both ends of a laminate formed by laminating a plurality of single cell batteries are held by a current collecting current collector plate and an end plate, and both end plates are A plurality of studs are passed through the through-holes, and the laminate is tightened via a spring.

  It is necessary to supply fuel (hydrogen) necessary for the reaction, oxidant (air), and cooling water required for cooling evenly to each single cell battery of the fuel cell stack having such a configuration. A manifold for distributing and collecting the cooling water is provided. Such manifolds include an internal manifold system and an external manifold system.

  The separator is generally a molded carbon plate formed by mixing carbon and resin, and the current collector plate is generally a metal plate such as stainless steel having a thickness of 2 mm or more. Since the carbon plate and stainless steel have a large contact resistance and a voltage drop occurs between the laminate and the current collector plate, it is common to form a coating such as gold on the stainless steel surface.

  However, the gold coating formed on the stainless steel surface has a problem that pinholes are easily generated, and galvanic corrosion occurs on the side surface of the cooling water internal manifold, so that metal components are eluted into the cooling water. In addition, since the end plate is generally made of a metal such as stainless steel, there is a problem that electrolytic corrosion occurs on the side surface of the cooling water internal manifold.

  Several countermeasures have been proposed for the problem that the current collector plate and the end plate have galvanic corrosion as described above. For example, in Patent Document 1, a structure in which an insulating plate is inserted between a metal end plate and a laminate, a cylindrical pipe is provided in a portion corresponding to the internal manifold of the insulating plate, and cooling water does not contact the end plate. It is said.

Further, in Patent Document 2, the end plate is made of resin, and the end plate is bitten inside the internal manifold penetrating the current collector plate so that the cooling water does not contact the current collector plate. Further, in Patent Document 3, an insulating plate is inserted between the end plate and the current collector plate, a cylindrical pipe is provided on the end plate side of the inner manifold of the insulating plate, and the inner plate penetrating the current collector plate is bitten into the inner manifold. The cooling water is not in contact with the end plate and the current collector plate.
JP 2002-164075 A JP 2003-163026 A JP 2003-331905 A

  However, the current collecting plate is not described in the method according to Patent Document 1, and the problem that the cooling water and the current collecting plate are in contact with each other is not solved. Further, in the methods according to Patent Document 2 and Patent Document 3, a structure in which the cooling water does not contact the end plate and the current collector plate can be realized. However, a cylindrical pipe is provided on the insulating plate or the resin end plate, or the current collector plate. However, there is a problem that the structure is complicated because the internal manifold is bitten. In addition, the current collector plate is exposed on the side surface of the laminate, and the external manifold system in which the manifold is mounted on the side surface has a problem that the cooling water contacts the current collector plate.

  The present invention has been made to solve the above-described problems of the prior art, and its purpose is to prevent the cooling water and the reaction gas from contacting the metal current collector plate, The object is to provide a fuel cell stack having a simple structure capable of supporting both a manifold system and an external manifold system.

  In order to achieve the above object, the invention described in claim 1 is directed to a membrane electrode assembly in which gas diffusion electrodes are respectively disposed on both sides of a solid polymer membrane, and the gas diffusion of fuel gas and oxidant gas. A fuel gas flow path and an oxidant gas flow path, which are respectively supplied to the electrodes, and a separator provided on at least one surface; the fuel gas flow path is in contact with one surface of the gas diffusion electrode; and the oxidant gas flow path is the gas diffusion A fuel that is constructed by laminating a plurality of basic components arranged so as to be in contact with the other surface of the electrode to constitute a laminated body, and sandwiching the laminated body between end plates disposed at both ends thereof, and tightening and holding the fuel In the battery stack, the end plate is composed of a conductive inner plate and an insulating outer plate, and the generated current of the fuel cell stack is taken outside through the conductive inner plate. Together to, in the end plate portion, in which the fluid supply and exhaust to the fuel cell stack is characterized by being configured so as to contact only with the insulating outer plate.

  According to the first aspect of the present invention, the end plate is composed of the conductive inner plate and the insulating outer plate, and the fuel gas supplied to and exhausted from the fuel cell stack in the end plate. By making only the insulating outer plate the part where the oxidant gas and the cooling water are in contact with each other, the electrolytic corrosion of the conductive inner plate can be prevented. In addition, since the conductive inner plate and the insulating outer plate can be formed into a simple flat plate structure by taking out current through the conductive inner plate, the processing cost can be suppressed. .

  According to a second aspect of the present invention, in the fuel cell stack according to the first aspect, the separator is connected to the fuel gas supply manifold, the fuel gas discharge manifold, and the oxidant that communicate with the fuel gas flow passage and the oxidant gas flow passage. A gas supply manifold and an oxidant gas discharge manifold are provided to constitute an internal manifold of the laminate, and a fuel gas supply / discharge port and an oxidant gas supply are provided at positions in contact with the internal manifold of the insulating outer plate. -It is characterized by providing discharge ports and communicating with the corresponding manifolds.

  According to a third aspect of the present invention, in the fuel cell stack according to the first aspect, the fuel gas flow path or the oxidant gas flow path formed in the separator is extended to the end of the separator to extend to the side of the laminate. The external manifold is opened and communicated with an external manifold installed on a side surface of the laminate, and the external manifold is configured to be in contact with the insulating external plate.

  According to the invention described in claim 2 or claim 3 having the above-described configuration, it is possible to provide a fuel cell stack having a simple structure that can cope with both the internal manifold system and the external manifold system.

  According to a fourth aspect of the present invention, in the fuel cell stack according to the second or third aspect, a sealing material is inserted between the stacked body and the insulating outer plate, and the stacked body and the conductive material are inserted. A conductive cushion material is inserted between the inner plates.

  According to invention of Claim 4 which has the above structures, the electrolytic corrosion of an electroconductive internal plate is prevented more effectively by inserting a sealing material between a laminated body and an insulating external plate. be able to. Also, by inserting a conductive cushioning material between the laminate and the conductive inner plate, the Ni plating underlying the gold plating of the conductive inner plate, which has been a problem in the past, is prevented from corroding and eluting. be able to.

  According to the present invention, it is possible to provide a fuel cell stack having a simple structure that can prevent both cooling water and reaction gas from contacting a metal current collector plate and can be adapted to both an internal manifold system and an external manifold system. Can do.

  Embodiments of a fuel cell stack according to the present invention will be specifically described below with reference to the drawings.

(1) First Embodiment (1-1) Configuration The configuration of a polymer electrolyte fuel cell stack according to the present embodiment will be described with reference to FIG. That is, the single cell battery A includes a membrane electrode assembly (MEA) 1, an oxidant separator 2, and a fuel / cooling water separator 3. An oxidant gas flow passage 4 is provided on the surface of the oxidant separator 2, and the oxidant gas flow passage 4 includes an oxidant gas inlet manifold 5 formed on the side edge of the oxidant separator 2 and an oxidation gas. It communicates with an agent gas outlet manifold (not shown), and is configured to supply / discharge oxidant gas necessary for the reaction to / from the membrane electrode assembly 1.

  Also, a fuel gas flow passage (not shown) is provided on one surface (the back side in the figure) of the fuel / cooling water separator 3, and this fuel gas flow passage is connected to the fuel / cooling water separator 3. Are connected to a fuel gas inlet manifold 6 and a fuel gas outlet manifold 7 formed at the upper and lower peripheral edges of the fuel cell, and are configured to supply and discharge fuel gas required for the reaction to and from the membrane electrode assembly 1.

  Further, a cooling water flow passage 8 is provided on the other surface of the fuel / cooling water separator 3, and the cooling water flow passage 8 is formed in the cooling water formed on the side edge of the fuel / cooling water separator 3. It communicates with the inlet manifold 9 and the cooling water outlet manifold 10 and is configured to supply a predetermined amount of cooling water to cool the heat generated by the reaction. A plurality of single cell batteries A configured as described above are stacked to form a stacked body.

  Moreover, the end plate 20 which consists of the electroconductive internal plate 21 and the insulating external plate 22 is arrange | positioned at the both ends of the laminated body comprised as mentioned above. The oxidant gas inlet manifold 5 formed in the laminate is connected to an oxidant inlet port 23 provided outside the insulating outer plate 22, and an oxidant gas outlet manifold (not shown) is oxidized. Connected to the agent outlet port 24, an internal manifold for supplying and discharging the oxidizing gas is configured.

  The fuel gas inlet manifold 6 formed in the laminate is connected to a fuel inlet port 25 provided outside the insulating outer plate 22, and the fuel gas outlet manifold 7 is connected to a fuel outlet port 26. An internal manifold for supplying and discharging fuel gas is configured. Further, the cooling water inlet manifold 9 formed in the laminate is connected to a cooling water inlet port 27 provided outside the insulating outer plate 22, and the cooling water outlet manifold 10 is connected to the cooling water outlet port 28. Thus, an internal manifold for supplying and discharging the cooling water is configured.

  The insulating external plate 22 is obtained by compression molding, injection molding, or machining a heat-resistant thermosetting resin material such as epoxy resin, vinyl ester resin, phenol resin, or the like. Since a tightening load is applied to the insulating external plate 22, it is preferable to use a material having excellent strength, and a glass epoxy resin laminate formed by impregnating and laminating an epoxy resin on a glass fiber sheet may be used. This glass epoxy resin laminate has anisotropy in strength depending on the direction of the glass fiber sheet, and the direction in which the bending strength is strong is preferably the longitudinal direction, that is, the vertical direction.

  The external plate 22 is provided with a concave recess 29 on the inner side corresponding to the battery reaction part. An inner manifold for the gas and cooling water is provided around the depression 29, communicated with the inner manifold of the laminate, and the gas and cooling water provided outside the insulating outer plate 22. The gas / cooling water can be supplied / discharged via the inlet / outlet ports 23 to 28.

  Further, projections 30 are provided at the four corners of the insulating outer plate 22, and a fastening stud 32 and a fastening spring 33 attached through a hole 31 provided at the center of the projection 30, the end plate 20. A laminated body disposed therebetween is fastened and fixed. The conductive inner plate 21 is a single flat plate made of a conductive material such as stainless steel, and is configured to be fitted into the recess 29 of the insulating outer plate 22. In addition, an opening 34 is provided at the center of the recess 29, and the power generation current of the laminate is taken out through the opening 34.

(1-2) Action / Effect In the present embodiment having the above-described configuration, the end plate 20 includes the conductive inner plate 21 and the insulating outer plate 22 and is in contact with the internal manifold of gas / cooling water. By constituting the (insulating outer plate) with an insulating material, the electrolytic corrosion of the conductive inner plate 21 can be prevented. Moreover, since the conductive inner plate 21 and the insulating outer plate 22 can be made a simple flat plate structure by taking out the current from the center of the insulating outer plate 22, the processing cost can be reduced. be able to.

  Furthermore, since the laminated body is fastened by the fastening stud 32 and the fastening spring 33 via the insulating external plates 22 disposed at both ends of the laminated body, the insulating spacer of the fastening stud 32 is not necessary, and the number of parts is reduced. Is possible.

(2) Second Embodiment This embodiment is a modification of the first embodiment, and is between the insulating outer plate 22 and the conductive inner plate 21 and between the conductive inner plate 21 and the oxidant separator. A sealing material is inserted between the two.

(2-1) Configuration In this embodiment, as shown in FIG. 2, an internal plate sealing material for preventing leakage of reaction gas and cooling water between the insulating external plate 22 and the conductive internal plate 21. 40 is inserted. The inner plate sealing member 40 has substantially the same shape as the conductive inner plate 21, and has a rectangular hole at the center thereof at a position corresponding to the opening 34 formed in the insulating outer plate 22. 41 is formed. Then, the current extraction cable 43 fixed to the conductive inner plate 21 by the fixing bolt 42 is drawn out through the rectangular hole 41 and the opening 34.

  Further, an external plate sealing material 44 is inserted between the insulating external plate 22 and the oxidant separator 2 at the end of the laminate to prevent leakage of reaction gas and cooling water. The outer plate sealing material 44 has a frame shape so as to be in close contact with the edge portion 22 a of the insulating outer plate 22. The outer plate seal material 44 has holes 44a, 44b and the like at positions corresponding to the oxidant gas inlet manifold 6, the oxidant gas outlet manifold 7 and the like formed in the oxidant separator 2 and the insulating outer plate 22. Is formed.

  Further, a conductive cushion sheet 45 made of expanded graphite is disposed between the conductive inner plate 21 and the oxidant separator 2 at the end of the laminate. The conductive cushion sheet 45 made of expanded graphite is flexible and is provided not only for reducing the contact resistance between the metal and the carbon material but also for preventing the elution of the metal component.

  In addition, heat-resistant rubber materials such as EPDM, silicon, and fluorine rubber are suitable for each of the above-described sealing materials, and in order to achieve a reliable seal, a foam material or a structure provided with a convex lip on the surface is used. .

(2-2) Action / Effect In the present embodiment, the inner plate sealing material 40 is inserted between the insulating outer plate 22 and the conductive inner plate 21, and the conductive inner plate 21 and the oxidant separator 2 Since the outer plate seal material 44 is inserted between them, in addition to the operation and effect of the first embodiment, it is possible to further prevent electrolytic corrosion of the conductive inner plate 21.

  In addition, since the conductive inner plate 21 is made of metal and has a high contact resistance with a separator using carbon, the conductive inner plate 21 has been conventionally subjected to a surface treatment such as gold plating. In addition to being high, there is a problem that the Ni plating on the base of the gold plating is easily corroded and eluted.

  However, in this embodiment, there is flexibility between the conductive inner plate 21 and the oxidizer separator 2 at the end of the laminate, and the conductive material is made of expanded graphite that can reduce the contact resistance between the metal and the carbon material. By disposing the cushion sheet 45, it is possible to prevent the metal component from being eluted.

(3) Third Embodiment (3-1) Configuration The configuration of the polymer electrolyte fuel cell stack according to the present embodiment will be described with reference to FIG. That is, the single cell battery A includes a membrane electrode assembly (MEA) 1, an oxidant separator 2, and a fuel / cooling water separator 3. An oxidant gas flow passage 4 is provided on the surface of the oxidant separator 2, and an end portion of the oxidant gas flow passage 4 is opened on the side of the separator and is disposed on the side of the laminate. It communicates with the gas inlet / cooling water outlet external manifold 50 and the oxidant gas outlet / cooling water inlet external manifold 51, and is configured to supply / discharge the oxidant gas necessary for the reaction to the membrane electrode assembly 1. .

  In addition, a fuel gas flow passage (not shown) is provided on one surface (the back side in the figure) of the fuel / cooling water separator 3, and the end portions of the fuel gas flow passage are formed above and below the separator. A fuel electrode inlet external manifold 52 opened at the top of the stack and a fuel gas outlet external manifold 53 disposed at the bottom of the stack are communicated with the membrane electrode assembly. 1 is configured to supply and discharge.

  Further, a cooling water flow passage 8 is provided on the other surface of the fuel / cooling water separator 3, and an end portion of the cooling water flow passage 8 is opened on a side surface of the separator, and is disposed on a side portion of the laminate. The oxidant gas inlet / cooling water outlet external manifold 50 and the oxidant gas outlet / cooling water inlet external manifold 51 are connected to supply a predetermined flow rate of cooling water to cool the heat generated by the reaction. Has been. A plurality of single cell batteries A configured as described above are stacked to form a stacked body.

  Thus, in the present embodiment, the oxidant gas inlet / cooling water outlet external manifold 50, the oxidant gas outlet / cooling water inlet external manifold 51, the fuel gas inlet external manifold 52, and the fuel gas outlet are provided on the side surface of the laminate. An external manifold 53 is disposed, and each manifold communicates with a corresponding oxidant gas flow path, fuel gas flow path, and cooling water flow path, and supplies and discharges fuel / oxidant gas necessary for the reaction to the membrane electrode assembly. At the same time, a predetermined flow rate of cooling water is supplied to cool the heat generated by the reaction. The other configuration is the same as that of the first embodiment shown in FIG.

  Next, the end structure including the insulating outer plate 22 and the conductive inner plate 21 will be described in detail. That is, as shown in FIGS. 4 and 5, an inner plate seal member 40 is inserted between the insulating outer plate 22 and the conductive inner plate 21 to prevent leakage of reaction gas and cooling water. The inner plate sealing member 40 has substantially the same shape as the conductive inner plate 21, and has a rectangular hole at the center thereof at a position corresponding to the opening 34 formed in the insulating outer plate 22. 41 is formed. Then, the current extraction cable 43 fixed to the conductive inner plate 21 by the fixing bolt 42 is drawn out through the rectangular hole 41 and the opening 34.

  Further, an external plate sealing material 44 is inserted between the insulating external plate 22 and the oxidant separator 2 at the end of the laminate to prevent leakage of reaction gas and cooling water. The outer plate sealing material 44 has a frame shape so as to be in close contact with the edge portion 22 a of the insulating outer plate 22.

  Further, a conductive cushion sheet 45 made of expanded graphite is disposed between the conductive inner plate 21 and the oxidant separator 2 at the end of the laminate. The conductive cushion sheet 45 made of expanded graphite is flexible and is provided not only for reducing the contact resistance between the metal and the carbon material but also for preventing the elution of the metal component.

  In addition, heat-resistant rubber materials such as EPDM, silicon, and fluorine rubber are suitable for each of the above-described sealing materials, and in order to achieve a reliable seal, a foam material or a structure provided with a convex lip on the surface is used. .

(3-2) Actions / Effects In this embodiment in which the manifold is disposed outside the laminate, the same actions / effects as in the first embodiment can be obtained. That is, the end plate 20 is composed of a conductive inner plate 21 and an insulating outer plate 22, and a portion (insulating outer plate) that is in contact with the external manifold of gas / cooling water is made of an insulating material. The electric corrosion of the plate 21 can be prevented.

  Moreover, since the conductive inner plate 21 and the insulating outer plate 22 can be made a simple flat plate structure by taking out the current from the center of the insulating outer plate 22, the processing cost can be reduced. be able to.

  Furthermore, since the laminated body is fastened by the fastening stud 32 and the fastening spring 33 via the insulating external plates 22 disposed at both ends of the laminated body, the insulating spacer of the fastening stud 32 is not necessary, and the number of parts is reduced. Is possible.

  Further, an inner plate sealing material 40 is inserted between the insulating outer plate 22 and the conductive inner plate 21, and an outer plate sealing material 44 is inserted between the conductive inner plate 21 and the oxidant separator 2. Therefore, the electrolytic corrosion of the conductive inner plate 21 can be more effectively prevented.

  Further, a conductive cushion sheet 45 made of expanded graphite is provided between the conductive inner plate 21 and the oxidant separator 2 at the end of the laminate, which is flexible and can reduce the contact resistance between the metal and the carbon material. By installing, it can prevent that a metal component elutes.

(4) Other Embodiments The present invention is not limited to the above-described embodiments, and the size, shape, and the like of each member can be changed as appropriate.

  FIG. 6 is a modification of FIG. 5, and fixing bolt penetrating openings 51 and 52 are provided in the insulating outer plate 22 and the inner plate seal material 40, and the inner plate fixing bolt 53 allows the conductive inner The plate 21 and the insulating external plate 22 are configured to be fixed.

  With this configuration, when the fuel cell stack is assembled, the conductive inner plate 21 can be fixed to the insulating outer plate 22 in advance, and the handling becomes easy. Further, when the inner plate fixing bolt 53 is made of metal, the inner plate fixing bolt 53 and the conductive inner plate 21 are electrically connected. It may also serve as a takeout terminal. In this case, the current extraction opening (opening 34, rectangular hole 41) can be omitted.

1 is an exploded perspective view showing a configuration of a first embodiment of a fuel cell stack according to the present invention. Sectional drawing which shows the structure of 2nd Embodiment of the fuel cell stack concerning this invention. The disassembled perspective view which shows the structure of 3rd Embodiment of the fuel cell stack based on this invention. The disassembled perspective view which shows the structure of the edge part of the fuel cell stack in 3rd Embodiment shown in FIG. Sectional drawing which shows the structure of the fuel cell stack in 3rd Embodiment shown in FIG. Sectional drawing which shows the structure of the modification of the fuel cell stack which concerns on this invention.

Explanation of symbols

1 ... Membrane electrode assembly (MEA)
2 ... oxidant separator 3 ... fuel / cooling water separator 4 ... oxidant gas flow passage 5 ... oxidant gas inlet manifold 6 ... fuel gas inlet manifold 7 ... fuel gas outlet manifold 8 ... cooling water flow passage 9 ... cooling water inlet manifold 10 ... Cooling water outlet manifold 20 ... End plate 21 ... Conductive inner plate 22 ... Insulating outer plate 29 ... Depression 30 ... Protrusion 32 ... Tightening stud 33 ... Tightening spring 34 ... Opening 40 ... Inner plate sealing material 41 ... Rectangular hole 42 ... Fixing bolt 43 ... Current extraction cable 44 ... External plate sealing material 45 ... Conductive cushion sheet 51, 52 ... Fixing bolt penetration opening 53 ... Internal plate fixing bolt

Claims (4)

A membrane electrode assembly in which gas diffusion electrodes are arranged on both sides of a solid polymer membrane, and a fuel gas flow path and an oxidant gas flow path for supplying fuel gas and oxidant gas to the gas diffusion electrode, respectively, are provided on at least one side. A plurality of basic components configured such that the fuel gas flow passage is in contact with one surface of the gas diffusion electrode and the oxidant gas flow passage is in contact with the other surface of the gas diffusion electrode. In a fuel cell stack that is configured by stacking to form a stack, sandwiching the stack with end plates disposed at both ends thereof, and holding it tightly,
The end plate is composed of a conductive inner plate and an insulating outer plate, and the generated current of the fuel cell stack is taken out through the conductive inner plate, and the end plate portion is connected to the fuel cell stack. A fuel cell stack characterized in that a fluid to be supplied / exhausted is in contact with only the insulating outer plate.   The separator is provided with a fuel gas supply manifold, a fuel gas discharge manifold, an oxidant gas supply manifold, and an oxidant gas discharge manifold that communicate with the fuel gas flow passage and the oxidant gas flow passage. In addition, a fuel gas supply / discharge port and an oxidant gas supply / discharge port are provided at positions in contact with the internal manifold of the insulating outer plate, and communicated with the corresponding manifolds, respectively. The fuel cell stack according to claim 1.   The fuel gas flow path or the oxidant gas flow path formed in the separator is extended to the end of the separator and opened on the side surface of the laminate, and is communicated with an external manifold installed on the side surface of the laminate. The fuel cell stack according to claim 1, wherein the fuel cell stack is configured to be in contact with the insulating outer plate.   4. A sealing material is inserted between the laminated body and the insulating outer plate, and a conductive cushioning material is inserted between the laminated body and the conductive inner plate. The fuel cell stack described in 1.

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