JP2012226845A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: There is a problem that a fuel cell having an electrolyte layer made of a metal compound receives a clamping pressure in the stacking direction of the fuel cell through a sealing material and is damaged.
A sealing material for sealing a side surface between a pair of separators of a fuel cell having an electrolyte layer made of a metal compound is provided by adhesion, and the side surface of the electrolyte layer is adhered to the sealing material. A seal structure was adopted.
[Selection] Figure 1

Description

  The present invention relates to a cell structure of a fuel cell, and more particularly to a cell seal structure.

  A fuel cell is a device that directly converts chemical energy of fuel into electrical energy without passing through mechanical energy or thermal energy, and can achieve high energy efficiency. As a well-known fuel cell configuration, an electrolyte is arranged between a pair of electrodes to constitute a unit cell, and a fuel gas containing hydrogen is supplied to the anode electrode of each cell, and oxygen is contained in the cathode electrode. An electromotive force is obtained using an electrochemical reaction that occurs between the two electrodes.

  Fuel cells are usually classified according to the type of electrolyte used. That is, a phosphoric acid fuel cell (PAFC) that generates electricity at an operating temperature of about 190 ° C. using phosphoric acid as an electrolyte, and a solid polymer fuel cell that generates electricity at about 70 ° C. using an ion conductive polymer as an electrolyte ( PEFC), a solid oxide fuel cell (SOFC) that uses ion-conducting ceramics as an electrolyte and operates at about 1000 ° C.

  In recent years, research on solid oxide fuel cells capable of generating power at a lower temperature than before has been conducted. Patent Document 1 describes a solid oxide fuel cell using an oxide proton conductor as an electrolyte, which can obtain an electrical output from room temperature to less than 500 ° C.

Patent Document 2 describes a solid oxide fuel cell using an anion conductive basic oxide exhibiting high ionic conductivity at 300 ° C. or lower as an electrolyte.
Each cell of the fuel cell needs to seal the outer periphery of the gas so that the fuel gas containing hydrogen and the oxidant gas containing oxygen supplied to the anode electrode do not leak outside.

  FIG. 5 is a schematic view of a conventional general polymer electrolyte fuel cell. Electrodes 4a and 4b each comprising an anode catalyst layer 2a or a cathode catalyst layer 2b and a gas diffusion layer 3 are provided on both surfaces of an electrolyte layer 1 made of an ion conductive polymer, and a gas-impermeable separator 5 is provided on the outside thereof. Is provided. On the surface of the separator 5 on the electrode 4 side, a groove to be a gas flow path 6 is formed. The electrodes 4 a and 4 b are made slightly smaller than the electrolyte layer 1 and the separator 5, and the electrodes 4 a and 4 b between the peripheral edge of the electrolyte layer 1 and the peripheral edge of the separator 5 are sealed on the outer periphery. A material 7 is provided, and is configured to prevent the reaction gas supplied from the gas flow path 6 from leaking to the outside. In general, a plurality of fuel cells having such a configuration are stacked and tightened in the stacking direction to form a fuel cell stack to obtain a necessary voltage.

JP2004-63460 WO2010 / 007949

  In a solid electrolyte fuel cell using a solid electrolyte that operates at a relatively low temperature described in Patent Documents 1 and 2, an electrolyte plate formed by sintering a metal compound electrolyte as the electrolyte layer, or a metal compound electrolyte An electrolyte plate formed by mixing a resin with a resin is used as an electrolyte layer.

  Since these electrolyte plates are fragile materials, when a fuel cell having the same structure as the polymer electrolyte fuel cell shown in FIG. 5 described above is stacked and tightening pressure is applied, the electrolyte plate is sandwiched between the sealing materials of the electrolyte layer 1. Stress concentrates on the peripheral edge, and the electrolyte plate breaks, causing a cross leak in which gas leaks to the counter electrode side between the anode electrode and the cathode electrode, thereby significantly reducing the battery characteristics and making the operation impossible. There was a fear.

  Accordingly, an object of the present invention is to provide a fuel cell having a sealing structure in which the electrolyte layer is not damaged by being pressed by the sealing material.

In order to solve the above problems, in the present invention, an electrolyte layer made of a metal compound having an anode electrode on one main surface and a cathode electrode on the other main surface, and an anti-electrolyte of the anode electrode and the cathode electrode In a fuel cell provided with a separator on each layer side,
A sealing material that seals between the peripheral ends of the opposing separators is provided, and the sealing material and the side surface of the electrolyte layer are bonded to each other.

The sealing material may be bonded with an adhesive or may be melted and bonded to the sealing material itself.
It is good also as providing a gasket further on the outer periphery of the said sealing material between the peripheral edge parts of the said separator.

  Alternatively, one side surface of the sealing material is bonded to the side surface of the electrolyte layer, and a gasket is interposed between each separator-facing surface of the sealing material and each separator peripheral end, and tightened from the outside of each separator. A sealed structure may be used.

  According to the present invention, the electrolyte layer made of a metal compound is bonded to the sealing material on the side surface and is not pressed between the sealing materials. Therefore, the electrolyte layer is not broken by the seal, and cross leakage between the anode and the cathode of the reaction gas can be prevented, and a high quality fuel cell can be provided.

1 is a schematic cross-sectional view of a fuel cell according to a first embodiment of the present invention. Schematic diagram of a fuel cell stack manufactured using the fuel cell according to the first embodiment of the present invention. Schematic sectional view of a fuel cell according to a second embodiment of the present invention Schematic sectional view of a fuel cell according to a third embodiment of the present invention Schematic sectional view of a fuel cell according to a fourth embodiment of the present invention Schematic sectional view of a conventional polymer electrolyte fuel cell

  The fuel cell according to the present invention uses a metal compound in the electrolyte layer, and cross-leaks the reaction gas from the side surface of the fuel cell by the seal material adhered to the side surface of the fuel cell without sandwiching the electrolyte layer between the seal material. The feature is that it prevents.

As the electrolyte layer, a sintered body made of a metal compound such as NaCo ₂ O ₄ , Bi ₄ Sr ₁₄ Fe ₂₄ O ₅₆ , LaFe ₃ Sr ₃ O ₁₀ can be used, but not limited to this. In addition, a material having ion conductivity at a temperature lower than the heat resistant temperature of the sealing material used in the fuel cell is used.

  As the sealing material, an insulating material such as a rubber material such as fluorine rubber, ethylene propylene rubber, or silicone rubber, or a resin material such as polytetrafluoroethylene (PTFE) is used. Further, as an adhesive used for bonding the sealing material, a silicone adhesive, liquid fluororubber, and an epoxy adhesive can be used. In addition, a double-sided adhesive tape may be used instead of the adhesive, or a material in which an adhesive is previously applied to the sealing material may be used. The sealing material and the adhesive are not limited to these, and can be used as long as they have heat resistance and insulation at the operating temperature of the fuel cell.

  Further, instead of the sealing material bonded by the adhesive, a meltable sealing material may be melted and bonded to the side surface of the fuel cell. As such a sealing material, thermoplastic resins such as polyethylene, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (hereinafter referred to as PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP) can be used. .

  Examples of the present invention will be described below.

FIG. 1 is a schematic sectional view of a fuel cell according to a first embodiment of the present invention. A manufacturing procedure of the fuel cell 10 of this embodiment will be described.
First, Na ₂ CO ₃ and CoCO ₃ powder were mixed at a molar ratio of 1: 2 by a ball mill, calcined at 1000 ° C. for 2 h, and then pulverized to obtain NaCo ₂ O ₄ powder. Next, this NaCo ₂ O ₄ powder was molded with a mold at a pressure of 1 MPa to obtain a square thin plate having a side of 50 mm and a thickness of 2 mm. This was fired at a temperature of 1000 ° C. for 3 hours to obtain a dense sintered body. This sintered body was used as the electrolyte layer 11 of the fuel cell of this example.

Next, a NaCo ₂ O ₄ powder carrying 15 wt% of Pd was mixed with ethylene glycol, and this was applied to one surface of the electrolyte layer 11 by screen printing, followed by heat treatment to form the anode catalyst layer 12a. Formed.

Further, a surface of the electrolyte membrane 11 opposite to the side on which the anode catalyst layer 12a is formed is coated with NaCo ₂ O ₄ powder mixed with ethylene glycol by a screen printing method, and then subjected to a heat treatment to form a cathode. A catalyst layer 12b was formed.

Then, carbon paper having the same dimensions as the electrolyte layer 11 (manufactured by Toray, TGPH60) is laminated as the gas diffusion layer 13 on the surfaces of the anode catalyst layer 12a and the cathode catalyst layer 12b, and the catalyst layers 12a, 12b and the gas diffusion layer The anode electrode 14a and the cathode electrode 14b composed of 13 were formed. Further, a separator 15 was laminated on the surface of each gas diffusion layer 13.
The separator 15 was formed by forming a reaction gas channel 16 by molding a material made of carbon powder and resin. As the carbon powder, flake graphite powder was used. A phenol resin was used as the resin. A compound obtained by mixing these flake graphite powder and a phenol resin was press-molded to form a square separator 15 having a side 70 mm larger than the electrolyte layer 11.
As the separator 15, a metal separator obtained by processing a metal can be used instead of the carbon-based separator described above.

  Next, the reaction gas supplied from the reaction gas channel 16 when the fuel cell is operated leaks from the outer periphery (side surface) of the electrodes 14a and 14b and the outer periphery of the contact portion between the separator 15 and the electrodes 14a and 14b. A sealing material 17 is provided to prevent this. As the sealing material 17, fluororubber was used.

  In bonding the sealing material 17, the adhesive 18 is applied to the entire side surfaces of the electrolyte layer 11 and the electrodes 14 a and 14 b, and the fluororubber sealing material 17 is applied from the outside of the adhesive 18 so as to cover the entire side surface in an airtight manner. Glued to. Incidentally, the adhesive 18 and the sealing material 17 are hermetically covered up to the contact portion between the side surface of the gas diffusion layer 13 and the separator 15 so as to prevent the reaction gas from the peripheral portion of the contact portion between the separator 15 and the gas diffusion layer 13. .

As the adhesive 18, Alemcobond 570 (trade name, manufactured by Odec Co.) having heat resistance at 300 ° C. is used.
Instead of applying the adhesive 18 to the side surfaces of the electrolyte layer 11 and the electrode 14 as described above, the adhesive 18 is applied to the sealing material 17 side, and this is applied to the electrolyte layer 11 and the electrodes 14a and 14b. It is good also as making it adhere to the side surface.

  Further, the fluororubber sealing material 17 is formed in a frame shape in which the inner peripheral dimension is smaller than the outer peripheral dimension of the electrolyte layer 11 and the electrode 14, and the electrolyte layer is extended and coated with the adhesive 18. 11 and the electrode 14 can also be bonded over the outer periphery.

  An example in which a fuel cell stack 100 is configured by stacking a plurality of fuel cells 10 of the present embodiment manufactured as described above is shown in FIG. The fuel cell stack 100 is provided with a manifold 101 (one of four is shown in FIG. 2) on each of the four side surfaces, and supplies the reaction gas from the gas inlet manifold to each reaction gas flow path 16 to allow the reaction gas flow. The reaction gas after passing through the passage 16 is configured to be discharged to the gas outlet manifold.

A fuel cell according to a second embodiment of the present invention is shown in FIG. The same members as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.
In the separator 25 of the fuel cell 20 of this example, as shown in FIG. 3B, the reaction gas channel 26 is formed in a meandering groove, and through holes for a reaction gas manifold are formed at both ends of the meandering groove. At the gas inlet part and outlet part between the end of the first and last straight flow paths of the meandering groove and the manifold, the concave part 28 made of fluororesin shown in FIG. Thus, the surfaces of the gas inlet and the gas outlet were made to be the same height as the surface of the separator 25. The cathode electrode 14b side separator 25 shown in FIG. 3A is a cross-sectional view taken along a broken line AA shown in FIG.

The electrolyte layer 11 and the electrode catalyst layers 12a and 12b were the same as those in Example 1, and the gas diffusion layer 13 and the separator 25 described above were laminated thereon.
Next, the PTFE sheet was cut into a strip shape to obtain a sealing material 27. The adhesive 18 was applied along the two long sides of one surface of the sealing material 27, and the adhesive 18 was also applied to the side surface of the electrolyte layer 11. And as shown to Fig.3 (a), by sticking each long side of the sealing material 27, and the separator 25, and adhere | attaching the center part parallel to the long side of the sealing material 27 on the side surface of the electrolyte layer 11, The side surface of the fuel cell 20 was sealed.

  Next, four fluororubber gaskets 29 (FIG. 3D) were inserted in the peripheral portion between the two separators 25 so as to surround the electrolyte layer 11 and the electrode 14. A through hole is formed in the gasket 29 in a portion overlapping with the through hole of the separator 25 in advance, and both the through holes communicate with each other to form a reaction gas flow hole.

A plurality of the fuel cells 20 assembled as described above are stacked and tightened in the stacking direction to form a fuel cell stack.
As a result, the bonding portion between the side surface of the electrolyte layer 11 and the sealing material 27 prevents cross leak of the reaction gas between the anode electrode 14a and the cathode electrode 14b, and the bonding portion between the separator 25 and the sealing material 27 serves as the fuel cell 20. The seal structure prevents leakage of reaction gas to the outside.

  In place of this embodiment, the adhesive 18 may be applied to the entire surface of the sealing material 27 and adhered to the side surface of the fuel cell 20, or the entire side surface of the fuel cell 20 and the sealing material 27 of the separator 25 Alternatively, the adhesive 18 may be applied to the bonded portion, and the sealing material 27 may be bonded thereto.

The fuel cell 30 of the present embodiment will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.
In the adhesion of the sealing material 37 of the fuel cell 30 of the present embodiment, the adhesive 18 is applied to the entire side surfaces of the electrolyte layer 11 and the catalyst layers 12a and 12b, and the fluororubber sealing material 37 is applied from the outside of the adhesive 18. Adhering was performed so that the entire side surfaces of the electrolyte layer 11 and the catalyst layers 12a and 12b were hermetically covered. A frame-shaped rubber gasket 39 was laminated between the separator 15 and the sealing material 37, and was tightened from the outside of both opposing separators to seal between the peripheral edges of the separator.

  In this embodiment, the adhesive 18 is applied to the entire side surfaces of the electrolyte layer 11 and the catalyst layers 12a and 12b and the sealing material 37 is adhered, but at least the side surfaces of the electrolyte layer 11 are adhered to the sealing material 37. If so, cross leak between the anode gas and the cathode gas can be prevented.

The fuel cell 40 of the present embodiment will be described with reference to FIG. The fuel cell 40 of this example was assembled using the same components as those of Example 1 except for the sealing material 47.
The electrolyte layer 11, the electrodes 14a and 14b, and the separator 15 are stacked and placed in the mold, and the sealing material layer 47 is thermally melted using PFA on the side surfaces of the electrolyte layer 11, the catalyst layers 12a and 12b, and the gas diffusion layer 13. Molded. Specifically, after the PFA sealing material was placed, the cell itself was heat-treated in the vicinity of the melting temperature of PFA to be adhered to the cell portion. Instead of this, it is also possible to install a battery in the mold and injection-mold the sealing material. According to this embodiment, the sealing material layer 47 can be integrally bonded to the side surfaces of the electrolyte layer 11, the catalyst layers 12 a and 12 b, and the gas diffusion layer 13.

  In this embodiment, the sealing material layer 47 is molded. However, the present invention is not limited to this, and the sealing material layer 47 is formed by adhering a molten sealing material to the side surfaces of the electrolyte layer 11 and the electrodes 14a and 14b. It is good.

1, 11 Electrolyte layer 2a, 12a Anode catalyst layer 2b, 12b Cathode catalyst layer 3, 13 Gas diffusion layer 4a, 14a Anode electrode 4b, 14b Cathode electrode 5, 15, 25 Separator 6, 16, 26 Reaction gas flow path 7, 17, 27, 37, 47 Seal material 18 Adhesive 28 Recess material 29 Gasket 10, 20, 30 Fuel cell 100 Fuel cell stack 101 Manifold

Claims (7)

In a fuel cell comprising an electrolyte layer made of a metal compound having an anode electrode on one main surface and a cathode electrode on the other main surface, and a separator on each of the anode electrode and the anti-electrolyte layer side of the cathode electrode,
A fuel cell comprising: a sealing material that seals between the peripheral end portions of the opposing separators, wherein the sealing material and a side surface of the electrolyte layer are bonded.   The fuel cell according to claim 1, wherein the sealing material is bonded with an adhesive.   The fuel cell according to claim 2, wherein the sealing material is fluorine rubber, ethylene propylene rubber, silicone rubber, or polytetrafluoroethylene.   The fuel cell according to any one of claims 1 to 3, further comprising a gasket on the outer periphery of the sealing material between the peripheral end portions of the separator.   One side surface of the sealing material is bonded to the side surface of the electrolyte layer, and a gasket is interposed between each separator-facing surface of the sealing material and each separator peripheral end, and tightened from the outside of each separator. The fuel cell according to any one of claims 1 to 3, wherein the seal is made by the following.   The fuel cell according to claim 1, wherein the seal material is bonded by melting and bonding the seal material.   The fuel cell according to claim 6, wherein the sealing material is any one of polyethylene, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, and a tetrafluoroethylene / hexafluoropropylene copolymer.