JP2006318691A - Fuel cell and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell, along with its manufacturing method, capable of assuring stable power generation by reducing movement resistance at draining of water generated inside the fuel cell. <P>SOLUTION: An electrode structure (MEA) 22 in which an electrolyte film 28 is arranged between an anode electrode 30 and a cathode electrode 32, and separators 24 and 26, are stacked in a fuel cell 10. A fuel gas channel 48 is formed between the anode electrode 30 and the adjoining separator 26, while an oxidant gas channel 46 is formed between the cathode electrode 32 and the adjoining separator 24. A seal member is interposed between both electrodes 30 and 32 and the adjoining separators 24 and 26, and a part of both gas channels is formed by the seal member. The contact angle of surface water of the separator forming both gas channels is 80° or less, and the difference is 40° or less from that of at least a part of the seal member forming both gas channels by adjoining the separator. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell and a method for manufacturing the fuel cell. In particular, the present invention relates to a fuel cell and a method for manufacturing the fuel cell that can ensure stable power generation by reducing movement resistance during drainage of water generated inside the fuel cell.

  In recent years, fuel cells are highly expected as a means for suppressing global warming and environmental destruction, and as a next-generation power generation system. A fuel cell generates energy by an electrochemical reaction between hydrogen and oxygen. For example, a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid electrolyte fuel cell, a solid polymer fuel cell, etc. Can be mentioned. Among these, the polymer electrolyte fuel cell has been attracting attention as a power source for automobiles (two-wheeled and four-wheeled) and portable power sources because it can be started from room temperature and has a small size and high output.

  A general polymer electrolyte fuel cell is a stack formed by combining several tens to hundreds of power generation cells (single cells) having an electrode structure (MEA) as a basic structural unit and sandwiching the electrode structure with a separator. Used as a (collective battery). The electrode structure, which is the basic structural unit of the stack, is formed of two electrodes, an anode electrode (fuel electrode) and a cathode electrode (air electrode), and a polymer electrolyte membrane sandwiched between these electrodes. Is formed of a catalyst layer that performs an oxidation / reduction reaction in contact with the polymer electrolyte membrane and a gas diffusion layer in contact with the catalyst layer.

  The polymer electrolyte fuel cell having such a configuration generates power by supplying a fuel containing hydrogen to the anode electrode (fuel electrode) side and supplying oxygen or air to the cathode electrode (air electrode) side. In the fuel gas supplied to the anode electrode (fuel electrode), hydrogen is ionized on the electrode catalyst and moves to the cathode electrode (air electrode) side through the electrolyte membrane, and the electrons generated during that time are taken out to the external circuit. It is used as direct current electric energy.

  By the way, as a separator of a polymer electrolyte fuel cell, a metal separator is often used because strength, compactness, and low temperature startability are required. In this metal separator, fuel gas on the anode electrode (fuel electrode) side, oxygen or air on the cathode electrode (air electrode) side, and water generated inside the fuel cell flow in the flow path as a liquid. For this reason, in the downstream region of the gas flow, the water generated by the power generation reaction tends to accumulate easily. Furthermore, the generated water may block the gas flow path and cause a phenomenon called flooding. The flooding phenomenon impairs the power generation stability of the fuel cell, causes the water generated during the previous power generation to freeze below the freezing point, deteriorates the fuel cell, or blocks the gas flow path to disable power generation. Therefore, it must be avoided.

Therefore, Patent Document 1 proposes a technique for preventing a decrease in the performance of the fuel cell by forming a hydrophilic coating film in a groove portion serving as a gas flow path of the separator. According to this technology, a gas flow is provided by imparting hydrophilicity to the groove that becomes the gas flow path of the separator by a hydrophilic coating film and efficiently discharging water droplets existing in the gas flow groove to the outside of the fuel cell. It is possible to prevent the groove from being blocked by water droplets.
JP 2001-093539 A

  By the way, a separator of a fuel cell may be provided with a seal portion made of a seal material for the purpose of preventing leakage of a reaction gas or the like. This sealing material may cover a part of the reaction gas flow path because of demands for productivity and sealing performance accuracy. This is because the production process is reduced or the mold is simplified, and the adhesive strength between the sealing material and the separator base material is improved, so that a separator having excellent durability can be obtained.

  Usually, since such a sealing material has water repellency, in a separator having a sealing member, the gas flow path is hydrophilic only by imparting hydrophilicity to the gas flow path portion as in Patent Document 1. However, the water droplets that come into contact with the seal portion of the separator have a ball shape (see FIG. 1A), and the contact angle θ with the surface of the seal portion increases. For this reason, although the drainage of the water generated inside the fuel cell is improved in the gas flow path portion of the separator, the portion in contact with the seal portion is still not sufficient, and the flow of the generated water to be discharged is hindered. End up. In particular, at the boundary between the hydrophilic gas flow path portion and the water-repellent seal portion, the change in the water repellency angle increases and the water transfer resistance increases rapidly, so that the discharge performance is significantly reduced. End up. As a result, the gas flow was hindered by the water droplets, and the power generation performance was unstable.

  The present invention has been made in view of the above problems, and a fuel cell and a fuel that can ensure stable power generation by reducing movement resistance during drainage of water generated inside the fuel cell. It aims at providing the manufacturing method of a battery.

  In order to solve the above-described problems, the present inventors have conducted extensive research focusing on the contact angle between the separator seal portion and water. As a result, it is possible to reduce the resistance to movement of water generated inside the fuel cell by using a separator in which the difference in contact angle between the separator seal portion and the base material portion of the separator is below a certain reference. The inventors have found that stable power generation can be ensured, and have completed the present invention. More specifically, the present invention provides the following.

  (1) An electrode structure in which an electrolyte membrane is disposed between an anode electrode and a cathode electrode and a separator are stacked, and a fuel gas flow path is formed between the anode electrode and a separator adjacent thereto. And a fuel cell in which an oxidant gas flow path is formed between the cathode electrode and a separator adjacent to the cathode electrode, and a seal member is interposed between the electrodes and the separator adjacent thereto. In addition, a part of both the gas flow paths is formed by the seal member, and the separator forming the both gas flow paths has a water contact angle of 80 degrees or less on the surface, and the separator The difference between the contact angle of water on the surface of at least a part of the seal member forming both the gas flow paths adjacent to the gas passage is 40 degrees or less.

  In the fuel cell of (1), a groove constituting the fuel gas channel and / or the oxidant gas channel is formed in the separator adjacent to both electrodes, and a part of both gas channels is formed by the seal member. It has been done. Here, the “seal member that forms both the gas flow paths adjacent to the separator” means that the “seal member” is in contact with the separator base material that forms the gas flow path and is sealed The member itself refers to a seal portion that forms both gas flow paths.

  According to the fuel cell of (1), the contact angle of water on the surface of the separator forming both gas flow paths is 80 degrees or less, and both gas flow paths are formed adjacent to this separator. By making the difference between the contact angle of water and at least a part of the surface of the sealing member 40 degrees or less, the contact angle of the generated water contacting not only the gas flow path but also the seal portion can be reduced. For this reason, even when the water generated in the fuel cell moves through the gas flow path, even when it comes into contact with the seal member, it is possible to prevent water droplets from forming a ball shape. It is possible to prevent the gas flow from being hindered by the water droplets.

  In addition, since the contact angle does not change greatly at the boundary between the gas flow path portion of the separator having hydrophilicity and the gas flow path portion configured by the seal member, the generated water moves through the gas flow path. It is possible to prevent the movement resistance of the material from increasing rapidly and the discharge performance from decreasing. For this reason, the water produced | generated by the electric power generation of a fuel cell can be efficiently discharged | emitted to the exterior of a fuel cell, and it becomes possible to ensure the stable electric power generation property.

  The contact angle of water on the surface of the separator that forms both gas flow paths, and the contact angle of water on the surface of at least a part of the seal member that forms both gas flow paths adjacent to the separator, Is preferably 30 degrees or less, and more preferably 20 degrees or less.

Here, the “contact angle” refers to an angle formed by an arc of a droplet formed when a solid and a liquid come into contact with the solid. FIG. 1A is a diagram illustrating a state of water droplets attached to a water-repellent solid surface. FIG. 1B is a diagram showing a state of water droplets attached to a hydrophilic solid surface. As shown in FIG. 1A, when the surface of the solid separator is water-repellent, the water droplets are ball-shaped and the contact angle θ ₁ is larger than 90 degrees. On the other hand, as shown in FIG. 1B, when the surface of the separator is hydrophilic, the water droplets are crushed and the contact angle θ ₂ becomes smaller than 90 degrees.

When the contact angle θ ₁ is large, the cross-sectional area of the gas flow path is blocked by the ball-shaped water, and the gas flow is prevented (see FIG. 1A). If the flow of gas is hindered by the ball-shaped water, sufficient reaction gas does not spread to each reaction part of the fuel cell, and power generation performance is reduced. Furthermore, since drainage is not performed sufficiently, a phenomenon called flooding occurs, and the power generation stability of the fuel cell is impaired, or the remaining water produced and generated during the previous power generation freezes below freezing point. Since stress is applied to the cell, the cell deteriorates or power generation becomes impossible.

Therefore, in order to avoid clogging of the gas flow path and improve the water discharge performance, at least the surface forming the gas flow path of the separator is required to be hydrophilic. When the surface of the separator is hydrophilic, the contact angle θ ₂ with water is small, and the attached water is crushed (see FIG. 1B). For this reason, a gas flow path is not obstruct | occluded with produced | generated water, and the above malfunctions do not arise.

  In this regard, in the present invention, the contact angle of the surface of the separator forming both gas flow paths is set to 80 degrees or less. By setting it to 80 degrees or less, the produced water adhering to the reaction gas flow path is crushed and spreads on the separator surface. Therefore, it is possible to prevent the generated water from becoming a pressure loss body in the gas flow path, and it is possible to prevent the gas flow from being hindered by the ball-shaped water and the power generation performance of the fuel cell from being lowered.

  The contact angle between the separator surfaces forming both gas flow paths is preferably 70 degrees or less, and more preferably 50 degrees or less.

  In the present invention, the separator is of course formed only when the grooves constituting the oxidant gas flow path and the fuel gas flow path of the separator are made hydrophilic and the contact angle of water on the surface thereof is 80 degrees or less. The contact angle of water on the entire surface of the substrate may be 80 degrees or less.

  As described above, when both gas flow paths by the separator base material are made hydrophilic for the purpose of avoiding blockage of the gas flow path and improving the water discharge performance, a sealing member for the purpose of preventing reaction gas leakage However, since the seal member has higher water repellency than the base material portion constituting the gas flow path of the separator, the gas flow path by the separator base material There is a large difference in hydrophilicity at the boundary portion where the gas flow path by the seal member is adjacent, for example, at the entrance / exit portion of both gas flow paths or the portion where the seal member is in contact with both gas flow paths. For this reason, when the water which moves a gas flow path approaches the said point, there exists a tendency for movement resistance to become large rapidly and to be stagnant, and drainage property will fall.

  Therefore, in the present invention, in order to reduce the difference in hydrophilicity at the boundary portion where the gas flow path by the separator base material and the gas flow path by the seal member are adjacent, that is, the difference in the contact angle with water, Not only the formed gas flow path but also the portion of the gas flow path formed by the seal member imparts hydrophilicity.

  In the present invention, when the cooling medium flow path is provided in the separator and the cooling medium flows between the separators, the fuel gas flow path and the oxidant gas flow path are respectively formed on both sides of the separator, and the electrode structure Both cases of generating electricity only by sandwiching one separator between the two are included. Moreover, the fuel cell stack which used both forms together may be sufficient.

  (2) The two gas flow paths communicate with a gas inlet communication hole and a gas outlet communication hole penetrating in the stacking direction in the separator, and are at least one of seal members forming the gas flow paths. The fuel cell according to (1), wherein the portion is disposed in a communication portion between the both gas flow paths and the gas outlet communication hole.

  A sealing member provided for the purpose of preventing leakage of fuel gas, oxidant gas, and cooling medium gas of the fuel cell comes into contact with a boundary portion between the gas outlet communication hole and the gas flow path in the manufacturing process of the fuel cell. There is a case. Since this sealing member usually has water repellency, it causes a decrease in water dischargeability.

  According to the fuel cell of (2), among the contact angle of water on the surface of the separator that forms both gas passages and the seal member that forms both gas passages, both gas passages and gas outlets By reducing the difference between the water contact angle of the portion arranged in the communication portion with the communication hole and 40 degrees or less, the difference in hydrophilicity at the boundary portion adjacent to the gas flow path and the seal portion is reduced, Even if the water moving through the gas flow channel reaches the point, it is possible to prevent the movement resistance from increasing rapidly. For this reason, stagnation of water due to an increase in movement resistance can be prevented, and the blockage of the gas flow path can be suppressed. As a result, stable power generation can be ensured. At the same time, even if there is a location where both gas flow paths are covered by the sealing member in the manufacturing process of the fuel cell, the drainage of the generated water can be maintained, so that the productivity of the fuel cell can be improved.

  (3) The fuel cell according to (1) or (2), wherein at least a part of the seal member forming both the gas flow paths is arranged at a boundary portion of a region where the both gas flow paths are formed. .

  According to the fuel cell of (3), both the gas flow paths are formed among the contact angle of water on the surface of the separator that forms both the gas flow paths and the seal member that forms both the gas flow paths. By making the difference between the contact angle of the water in the portion arranged at the boundary portion of the region that is 40 degrees or less, the difference in hydrophilicity at the boundary portion between the gas flow path and the seal portion is reduced, and the gas flow Even if the water moving along the path contacts the seal portion, it is possible to reduce the resistance received during the movement. For this reason, the stagnation of water due to the movement resistance can be prevented, and the blockage of the gas flow path can be suppressed. As a result, stable power generation can be ensured. At the same time, even if there is a location where both gas flow paths are covered by the sealing member in the manufacturing process of the fuel cell, the drainage of the generated water can be maintained, so that the productivity of the fuel cell can be improved.

  (4) An electrode structure in which an electrolyte membrane is disposed between an anode electrode and a cathode electrode and a separator are stacked, and a fuel gas flow path is formed between the anode electrode and a separator adjacent thereto. And a method of manufacturing a fuel cell in which an oxidant gas flow path is formed between the cathode electrode and a separator adjacent to the cathode electrode, and a seal member is interposed between the electrodes and the separator adjacent thereto. Then, a part of both gas flow paths is formed by the seal member, the water contact angle on the surface of the separator forming the both gas flow paths, and the both gas flow paths are formed adjacent to the separator. A method of manufacturing a fuel cell, comprising adjusting a difference between a contact angle of water on at least a part of a surface of a sealing member.

  According to the fuel cell manufacturing method of (4), the contact angle of water on the surface of the separator that forms both gas flow paths, and at least a part of the seal member that forms both gas flow paths adjacent to the separator. By adjusting the difference between the water contact angle on the surface of the liquid and the water generated in the fuel cell, even when it contacts the seal member when moving through the gas flow path, Can be prevented from forming a ball shape, and therefore, it is possible to manufacture a fuel cell in which the flow of gas is prevented from being hindered by the ball-shaped water droplets.

  In addition, since the change in the contact angle can be suppressed at the boundary between the gas flow path portion of the hydrophilic separator and the gas flow path portion constituted by the seal portion, the generated water flows through the gas flow path. It can prevent that the movement resistance at the time of movement increases rapidly, and discharge property falls. For this reason, the water produced | generated by the electric power generation of a fuel cell can be efficiently discharged | emitted to the exterior of a fuel cell, and it becomes possible to manufacture the fuel cell which ensured the stable electric power generation property.

  According to the present invention, in a fuel cell in which the surface of the separator is hydrophilic, the hydrophilicity of the separator sealing member is improved, the contact angle of water on the surface of the separator forming both gas flow paths, and the separator By making the difference between the contact angle of water on the surface of at least a part of the surface of the sealing member forming both gas flow paths adjacent to a certain reference or less, stagnation of generated water due to movement resistance is prevented, In addition, blockage of the gas flow path can be suppressed. As a result, the flow of gas is prevented from being hindered, and sufficient reaction gas is distributed to each reaction part of the fuel cell, so that a decrease in power generation performance can be suppressed. Furthermore, since the water generated in the fuel cell is sufficiently drained, the flooding phenomenon can be avoided and stable power generation can be ensured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Overall configuration of fuel cell (stack)]
FIG. 2 is a perspective view of the fuel cell 10 according to the embodiment of the present invention. The fuel cell (stack) 10 includes a stacked body 14 in which a plurality of power generation cells (single cells) 12 are stacked in the direction of arrow A, and end power generation cells 12a and 12b are provided at both ends of the stacked body 14 in the stacking direction. End plates 20a and 20b are arranged via terminal plates 16a and 16b and insulating plates 18a and 18b.

  FIG. 3 is a partially cutaway side view of the fuel cell 10 shown in FIG. FIG. 4 is an exploded perspective view of the power generation cell constituting the fuel cell 10 shown in FIG. As shown in FIGS. 3 and 4, each power generation cell (single cell) 12 includes an electrode structure (MEA) 22 stacked in the horizontal direction (the direction of arrow A), a first metal separator 24, and a second metal separator 24. Metal separator 26.

[Power generation cell (single cell)]
An electrode structure (MEA) 22 that is a structural unit of the power generation cell (single cell) 12 includes an anode electrode (fuel electrode) 30 and a cathode electrode (air electrode) 32, and a polymer electrolyte membrane disposed between these electrodes. 28. In some cases, both electrodes include a catalyst layer (not shown) in contact with the polymer electrolyte membrane and a gas diffusion layer (not shown) as components.

  An oxidant gas inlet for supplying an oxygen-containing gas, such as oxygen or air, is connected to one end edge of the power generation cell (single cell) 12 in the arrow direction B in the arrow direction A which is the stacking direction. The communication hole 40a, the cooling medium inlet communication hole 42a for supplying the cooling medium, and the fuel gas outlet communication hole 44b for discharging the hydrogen-containing gas as the fuel gas are arranged in the arrow direction C (vertical direction). Provided.

  The other end edge of the power generation cell (single cell) 12 in the arrow direction B communicates with each other in the arrow direction A, and a fuel gas inlet communication hole 44a for supplying fuel gas, and cooling for discharging the cooling medium. The medium outlet communication hole 42b and the oxidant gas outlet communication hole 40b for discharging the oxidant gas are arranged in the arrow direction C (vertical direction).

  In the fuel cell (stack) 10 according to the present embodiment, as shown in FIG. 2, in the end plate 20a constituting the fuel cell (stack) 10, the oxidizing gas inlet communication hole 40a is oxidized with oxygen, air, or the like. The agent gas is supplied, and a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas inlet communication hole 44a. Further, a cooling medium such as pure or ethylene glycol is supplied to the cooling medium inlet communication hole 42a.

[Separator]
The separators 24 and 26 according to the present embodiment are arranged on both electrode sides of the electrode structure (MEA) 22 and constitute the power generation cell (single cell) 12 together with the electrode structure (MEA) 22.

  An oxidant gas flow path 46 is provided on the surface 24 a adjacent to the electrode structure (MEA) 22 of the first metal separator 24. The oxidant gas passage 46 has a plurality of oxidant gas passage grooves 46 a and extends in the arrow direction B. Note that the oxidant gas flow channel groove 46a may constitute, for example, a serpentine flow channel that folds back and forth halfway in the arrow direction B.

  A fuel gas channel 48 is provided on a surface 26 a of the second metal separator 26 adjacent to the electrode structure (MEA) 22. The fuel gas passage 48 has a plurality of fuel gas passage grooves 48 a extending in the arrow direction B, like the oxidant gas passage 46.

  The first metal separator 24 and the second metal separator 26 integrally form a cooling medium flow path 50 between the surfaces 24b and 26b facing each other (see FIG. 3). The cooling medium flow path 50 has a plurality of cooling medium flow paths 50 a that are integrally formed on the back side of the oxidant gas flow path 46 and the back side of the fuel gas flow path 48 and extend in the arrow direction B. . The cooling medium flow path 50 communicates with the cooling medium inlet communication hole 42a and the cooling medium outlet communication hole 42b.

  In the present invention, it is possible to generate electric power by sandwiching one separator between the electrode structures by forming a fuel gas channel and an oxidant gas channel on both surfaces of the metal separator. It is. Therefore, in the fuel cell of the present invention, it is not always necessary to form the cooling medium flow path for each power generation cell, and the cooling medium flow path may be appropriately formed as necessary.

  In the present embodiment, as shown in FIG. 4A, the oxidant gas is introduced into the oxidant gas flow path 46 of the first metal separator 24 from the oxidant gas inlet communication hole 40a. In the oxidant gas flow path 46, the oxidant gas is dispersed in the plurality of oxidant gas flow path grooves 46a. For this reason, the oxidant gas moves along the cathode electrode (air electrode) 32 of the electrode structure (MEA) 22 via each oxidant gas flow channel groove 46a.

  On the other hand, as shown in FIG. 4B, the fuel gas is introduced into the fuel gas flow path 48 of the second metal separator 26 from the fuel gas inlet communication hole 44a. In the fuel gas channel 48, the fuel gas is dispersed in the plurality of fuel gas channel grooves 48a. Further, the fuel gas moves along the anode electrode (fuel electrode) 30 of the electrode structure (MEA) 22 via each fuel gas flow channel groove 48a.

In the electrode structure (MEA) 22, the hydrogen-containing gas serving as the fuel supplied to the anode electrode (fuel electrode) 30 and the oxygen-containing gas supplied to the cathode electrode (air electrode) 32 are expressed by the following equations: It is consumed by the electrochemical reaction shown in (1) and (2) and power is generated. At this time, water is generated by power generation on the cathode electrode (air electrode) 32 side.
Anode (fuel electrode) reaction: H ₂ → 2H ⁺ + 2e ⁻ (1)
Cathode (air electrode) reaction: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)

  Next, the oxidant gas consumed by being supplied to the cathode electrode (air electrode) 32 is discharged from the oxidant gas outlet communication hole 40b. Similarly, a hydrogen-containing gas that is supplied to and consumed by the anode electrode (fuel electrode) 30 is discharged from the fuel gas outlet communication hole 44b.

  As shown in FIG. 4C, the cooling medium supplied to the cooling medium inlet communication hole 42a flows into the cooling medium flow path 50 formed between the first metal separator 24 and the second metal separator 26. be introduced. In the cooling medium flow path 50, the cooling medium moves in the arrow direction B (horizontal direction). For this reason, the cooling medium can be cooled over the entire power generation surface of the electrode structure (MEA) 22, and then discharged from the cooling medium outlet communication hole 42b.

{Contact angle of separator forming reaction gas flow path}
The oxidant gas flow path 46 provided in the separator 24a according to the present embodiment and the fuel gas flow path 48 provided in the separator 26a have hydrophilicity, and water on the surface of the separator forming these flow paths. The contact angle is 80 degrees or less. 70 degrees or less is more preferable, and 50 degrees or less is more preferable.

  In addition, a conventionally well-known method can be used for the measurement of the contact angle of a separator. For example, it can be measured using a known contact angle meter.

  The method for setting the contact angle of the surfaces of the separators forming both gas flow paths to 80 degrees or less is not particularly limited, and a known method can be used. For example, the separator may be manufactured with a hydrophilic material, or a method of providing a hydrophilic film at least on both gas flow paths, a method of performing an alkali treatment, a method of performing electrolytic degreasing, and the like can be employed. .

  In the present invention, only the portion constituting the oxidant gas flow path and the fuel gas flow path of the separator is made hydrophilic and the contact angle of water on the surface is 80 degrees or less, as a matter of course. The entire surface of the material may be 80 degrees or less.

[Seal member]
The seal member of the present invention is provided so as to be interposed between both electrodes and a separator adjacent to these electrodes, and serves to prevent leakage of fuel gas, oxidant gas, and cooling medium, part of which is fuel. Part of the gas flow path and the reaction gas flow path is configured.

  In the present embodiment, the first seal member 54 is integrally provided on the surfaces 24 a and 24 b of the first metal separator 24 so as to go around the outer peripheral edge of the first metal separator 24. The first seal member 54 covers the oxidant gas inlet communication hole 40a, the oxidant gas outlet communication hole 40b, and the oxidant gas flow path 46 on the surface 24a, thereby preventing the oxidant gas from leaking. In addition, the cooling medium is prevented from leaking by covering the cooling medium inlet communication hole 42a, the cooling medium outlet communication hole 42b, and the cooling medium flow path 50 on the surface 24b.

  Further, a second seal member 56 is integrally provided on the surfaces 26 a and 26 b of the second metal separator 26 so as to go around the outer peripheral edge of the second metal separator 26. The second seal member 56 covers the fuel gas inlet communication hole 44a, the fuel gas outlet communication hole 44b, and the fuel gas passage 48 on the surface 26a, thereby preventing fuel gas from leaking. The surface 26b covers the cooling medium inlet communication hole 42a, the cooling medium outlet communication hole 42b, and the cooling medium flow path 50, thereby preventing the cooling medium from leaking.

  In addition, as an aspect which arrange | positions a sealing member in this invention, if it is an aspect provided so that it may interpose between both electrodes and the separator adjacent to these, it will not specifically limit. For example, the embodiment provided in the electrode structure (MEA) in addition to the embodiment provided directly on the separator so as to go around the outer peripheral edge of the separator, as in the present embodiment.

  In the present invention, the fuel gas flow path and the oxidant gas flow path are formed on both surfaces of the metal separator, respectively, and when power is generated simply by sandwiching one separator between the electrode structures, the oxidation of the separator is performed. Seal members may be provided on both the surface on which the agent gas flow path is provided and the surface on which the fuel gas flow path is provided. Thereby, leakage prevention of both oxidant gas and fuel gas can be performed.

{Contact angle of seal member forming gas flow path}
Of the seal members 54 and 56 according to the present embodiment, at least a part of the seal members forming the fuel gas channel 48 and the oxidant gas channel 46 have hydrophilicity. The difference between the contact angle of water on the surface of the separator substrate that is adjacent to the seal portion and forms the gas flow path and the contact angle of water on the surface of the seal portion is 40 degrees or less. This difference is preferably 30 degrees or less, and more preferably 20 degrees or less.

  In addition, the measurement of a contact angle can use a conventionally well-known method similarly to the measurement of the contact angle of the water of the separator surface which forms said reaction gas flow path. For example, it can be measured using a known contact angle meter.

  In the present invention, the contact angle of water on the surface of the separator base material forming the gas flow path and the water on the surface of at least a part of the seal member forming both gas flow paths adjacent to the separator. In order to make the difference from the contact angle 40 degrees or less, the seal member needs to be hydrophilic.

  The method for making the seal member hydrophilic is not particularly limited. For example, a hydrophilic material is used as the seal member in addition to a method of applying a hydrophilic treatment to the portion of the seal member to which hydrophilicity should be imparted. A method can be mentioned.

  As a specific example of the hydrophilization treatment method, a halogenation treatment such as a chlorination treatment, a plasma treatment, a UV treatment, a corona discharge, an excimer laser treatment, an ozone treatment, and a radiation treatment are performed on the position of the sealing member to be imparted with hydrophilicity. The method of giving is mentioned. These may be used alone or in combination of two or more. According to these methods, since it is possible to process only a portion to which hydrophilicity should be imparted, it is possible to suppress the influence of impurity contamination due to the processing.

  As another example of the hydrophilization treatment method, a method of applying, coating, and vapor-depositing a hydrophilic material such as polysilazane to the portion of the sealing member to which hydrophilicity should be imparted can be mentioned. As the polysilazane, a commercially available product can be used. For example, NP-P140-01 manufactured by Clariant can be used.

  As a specific example in the case of forming a sealing member using a hydrophilic material, a method of blending a hydrophilic additive into a material to be a sealing member can be mentioned. Hydrophilic additives include silica, mica, talc, titanium oxide, platinum and other inorganic substances having bound water, and molecular structures such as PVA (polyvinyl alcohol), surfactants, higher fatty acids and higher alcohols. Examples thereof include organic compounds having a hydrophilic group such as a hydroxyl group, a carboxyl group, an amino group, a carbonyl group, and a sulfonic acid group.

  Also, a method using a material itself having a hydrophilic group such as a hydroxyl group, a carboxyl group, an amino group, a carbonyl group, or a sulfonic acid group in the molecular structure as a material for a seal member, or such a material is used as a seal member. A method of blending into the material can also be adopted. Examples of the material having a hydrophilic group in the molecular structure include hydrophilic rubber such as vinyl silicone rubber.

  In the present invention, the location of the sealing member that needs to be imparted with hydrophilicity is imparted with hydrophilicity by any of the above methods to reduce the contact angle between the surface of the location and water, and the gas flow path is provided. The difference between the contact angle of water on the surface of the separator substrate that is formed and the contact angle of water on the surface of the sealing member that forms both gas flow paths adjacent to the separator and the hydrophilicity imparted portion Is set to 40 degrees or less.

  In the present invention, the material for the seal member used in addition to the material having the hydrophilic group is not particularly limited as long as it can prevent leakage of the reaction gas and the cooling solvent. . For example, elastic bodies such as fluorine rubber, silicone rubber, and EPDM (ethylene-propene-diene copolymer) can be used.

{Location of seal member to be hydrophilic}
In the present invention, the location of the sealing member to which hydrophilicity is to be imparted is at least a part of the sealing member forming both gas flow paths in the entire sealing member. Of the surfaces forming the fuel gas channel and the oxidant gas channel, when there is a large difference in hydrophilicity at the boundary between the location formed by the base material of the separator and the location formed by the seal member When the generated water that moves through the gas flow path comes into contact with the seal member, the movement resistance rapidly increases. For this reason, the stagnation of the generated water is likely to occur, and the gas flow is suppressed by the water-repellent ball-shaped water on the surface of the gas flow path formed by the seal member, and further the flooding phenomenon is induced due to the decrease in drainage. As a result, the power generation performance of the fuel cell becomes unstable. In this regard, in the fuel cell according to the present invention, both gas flow paths are made hydrophilic, at least a part of the seal member forming the gas flow path is made hydrophilic, and the movement resistance of the generated water moving through the gas flow path is reduced. Reduced and improved discharge.

  FIG. 5 is a diagram showing a preferred example of the location of the sealing member to which hydrophilicity should be imparted. FIG. 6 is a partially enlarged view of the dotted line range of FIG. Further, FIG. 7 is a cross-sectional view taken along line A-A ′ in FIG. 6.

  As shown in FIG. 5, among the sealing members forming part of the reaction gas flow path, preferable locations where hydrophilicity should be imparted include, for example, both gas flow paths and both gas outlet communication holes. A communication part (range P enclosed by the dotted line in FIG. 5) is mentioned.

  As shown in FIG. 6, the reaction gas flow path in the range P includes a groove portion formed by the separator base material (a groove portion in the dotted line range Q), a groove portion formed by the seal member (a groove portion in the dotted line range R), Have And while the groove part (groove part in dotted line range Q) formed with a separator base material has hydrophilicity, the seal member is water-repellent in the groove part (groove part in dotted line range R) formed by the seal member. Therefore, it usually has water repellency. The reaction gas flow path formed by the groove in the dotted line range R may be formed entirely by a seal member or partially by an electrode structure depending on the size of the separator and the electrode structure. Sometimes it is done. In the case where the entire surface in the flow path is formed of a seal member, it is possible to ensure good water discharge performance by hydrophilizing at least the groove.

  When the water generated by the power generation of the fuel cell moves inside the reaction gas flow path, it moves in the direction of the arrow shown in FIGS. 5 and 6, that is, in the same direction as the movement direction of both reaction gases. Then, it is drained from each gas outlet communication hole to the outside of the cell. At this time, when the difference in hydrophilicity is large at the boundary between the gas flow path formed of the separator substrate and the gas flow path formed of the seal member, the contact angle between the flow path surface and the passing water Will change drastically.

  8 and 9 are diagrams showing the relationship between the flow of water and the contact angle in the gas flow path in the vicinity of the communicating portion with both gas outlet communicating holes. FIG. 8 is a view when the seal member is water-repellent, and FIG. 9 is a view when the seal member is hydrophilic. The gap part of the graph in FIG. 8, FIG. 9 is the groove part (groove part in dotted line range Q) formed by the separator base material shown in FIG. 6, the groove part (groove part in dotted line range R) formed by the seal member, This is the boundary point.

  As shown in FIG. 8, in the gas flow path in which the sealing member is water repellent, the groove formed by the separator base material (the groove in the dotted line range Q in FIG. 6) and the groove formed by the seal member (FIG. At the boundary point between the separator 6 and the groove portion in the dotted line range R, the gap of the contact angle when changing from the hydrophilic surface by the separator base material to the water-repellent surface by the seal member is large. If this gap is large, the resistance to movement of water increases, which may impede discharge.

  On the other hand, as shown in FIG. 9, in the gas flow path in which the seal member is hydrophilic, the seal member is formed by a groove portion (groove portion in the dotted line range Q in FIG. 6) formed by the separator base material. Even at the boundary point between the groove portion (the groove portion in the dotted line range R in FIG. 6), the gap of the contact angle when changing from the surface by the separator base material to the surface by the seal member is small. For this reason, the movement resistance of water can be reduced, and as a result, favorable discharge property can be obtained.

  Further, among the seal members forming part of the reaction gas flow path, another example of a preferable portion to which hydrophilicity should be imparted is a seal that is a boundary portion of a region where both gas flow paths are formed. It is the location of the member. When the seal member is arranged so as to go around the outer peripheral edge of the separator, the end of the seal member may be applied to the reaction gas flow path provided in the separator due to productivity problems. In such a case, the generated water that moves through the gas flow path comes into contact with the seal portion and receives resistance when the seal portion is water-repellent. Therefore, it is preferable to make the sealing member hydrophilic at a boundary portion between the sealing member and the separator base material, and at a place where both the gas flow paths are applied.

  FIG. 10 is a view showing another example as a preferable portion to which hydrophilicity should be imparted among the sealing members forming a part of the reaction gas flow path. As shown in FIG. 10, an embodiment in which hydrophilicity is imparted to the seal member disposed on the side surface of the reaction gas channel is also a preferred embodiment in the present invention.

[Manufacturing method of fuel cell (stack)]
The fuel cell (stack) 10 according to the present embodiment includes, for example, a step of obtaining the electrode structure (MEA) 22 by arranging the polymer electrolyte membrane 28 between the anode electrode 30 and the cathode electrode 32, and the electrode structure. By disposing the separators 24 and 26 on both sides of the (MEA) 22, a fuel gas flow path 48 is provided between the anode electrode 30 and the second metal separator 26, and the cathode electrode 32 and the first metal separator 26 are arranged. A step of obtaining a power generation cell (single cell) 12 provided with an oxidant gas flow path 46 between the metal separator 24 and a fuel cell (stack) 10 obtained by stacking a plurality of power generation cells (single cells) 12. A manufacturing method that further includes a step of circling the outer peripheral edges of the separators 24 and 26 to provide the sealing members 54 and 56 and imparting hydrophilicity to the sealing members 54 and 56. Ri is manufactured.

  Further, in the present invention, a fuel gas flow path and an oxidant gas flow path are provided on both surfaces of a single separator, and a seal member is disposed so as to circulate around the outer peripheral edge of each surface. A method of alternately laminating electrode structures (MEA) and the separator can also be mentioned. In this case, a plurality of separators are appropriately arranged as necessary, and a cooling medium flow path is formed between the separators.

[Manufacturing method of separator]
In the manufacturing method of the separators 24 and 26 according to the present embodiment, first, the separator itself is molded by metal pressing or metal shaving. In that case, the groove part for forming a fuel gas flow path, an oxidant gas flow path, and a cooling medium flow path is provided. Next, a seal member necessary for preventing leakage of the oxidant gas, the fuel gas, and the cooling medium is provided so as to go around the outer peripheral edge of the separator. At this time, the sealing material is installed while adjusting the contact angle of the portion that should be hydrophilic among the seal members and the contact angle of the gas flow path adjacent to the portion using a contact angle meter. . Specifically, the position of the sealing member is made hydrophilic by using any one of the above-described methods for imparting hydrophilicity, and the relationship with the contact angle between adjacent gas flow paths is adjusted. In addition, the surface treatment etc. for providing rust prevention property may further be included.

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

<Example 1>
[Separator molding process]
A separator for a fuel cell was obtained by using a stainless steel plate SUS316L as a material and molding it by press working. The integral seal molding using silicone rubber was performed so as to go around the outer peripheral edge of the obtained separator.

[Step of imparting hydrophilicity to sealing member]
Among the obtained separators, plasma irradiation was carried out on the seal member forming the gas flow path near the reaction gas outlet communication hole under the following apparatus and conditions.
Device: DEM-451T manufactured by Anerva
Irradiation conditions: 200 W, 13.56 MHz, 1 min

<Example 2>
[Separator molding process]
A separator was molded in the same manner as in Example 1 except that EPDM rubber (ethylene-propylene-diene copolymer rubber) was used instead of silicone rubber.

[Step of imparting hydrophilicity to sealing member]
Among the obtained separators, chlorination treatment was carried out by bringing chlorosulfonic acid (manufactured by Kanto Chemical Co., Inc.) into contact with a sealing member forming a gas flow path near the reaction gas outlet communication hole for 30 minutes.

<Example 3>
[Separator molding process]
A separator was molded in the same manner as in Example 1.

[Step of imparting hydrophilicity to sealing member]
Among the obtained separators, polysilazane (NP-P140-01 manufactured by Clariant) is sprayed on a sealing member that forms a gas flow path near the reaction gas outlet communication hole, and left at room temperature for 7 days. A glass coat was formed.

<Example 4>
[Separator molding process]
A separator was molded in the same manner as in Example 1 except that the following composition containing a hydrophilic additive was used as the material for the seal member.
EPDM rubber (ethylene-propylene-diene copolymer rubber): 100 parts by mass Dodecylbenzenesulfonic acid (manufactured by Kanto Chemical Co., Inc.): 0.5 parts by mass Titanium oxide: 10 parts by mass

<Example 5>
[Separator molding process]
A separator was molded in the same manner as in Example 1 except that the following composition containing a hydrophilic additive was used as the material for the seal member.
EPDM rubber (ethylene-propylene-diene copolymer rubber): 100 parts by mass Dodecylbenzenesulfonic acid (manufactured by Kanto Chemical Co.): 0.1 parts by mass Titanium oxide: 3 parts by mass

<Example 6>
[Separator molding process]
A separator was molded in the same manner as in Example 1 except that vinyl silicone (manufactured by Sakai Chemical Industry Co., Ltd., Mutsumi Sea Grease Injection), which is a hydrophilic rubber, was used as the material for the seal member.

<Comparative Example 1>
A separator was molded in the same manner as in Example 1 except that the hydrophilic treatment by plasma irradiation was not performed.

<Comparative Example 2>
[Separator molding process]
A separator was molded in the same manner as in Example 2 except that the hydrophilic treatment by chlorination treatment was not performed.

<Evaluation>
[Measurement of contact angle]
About the separator obtained in Examples 1-6 and Comparative Examples 1-2, a separator base material (stainless steel plate SUS316L) that forms a gas flow path using a contact angle meter (Kyowa Interface Science Co., Ltd., CA-X). Measure the contact angle between the surface of the water and distilled water and the contact angle between the surface of the seal member (silicone rubber) that forms the hydrophilized gas flow path and distilled water, and the difference (Δ contact angle) Got. The results are shown in Table 1.

[Evaluation of water drainage]
The electrode structures (MEA) were sandwiched between the separators obtained in Examples 1 to 6 and Comparative Examples 1 and 2, and power generation cells (single cells) were created. 50 cc of water was added from the gas inlet communication hole of the cell, and then the reaction gas was scavenged for 10 seconds. The remaining amount of water was calculated by measuring the weight of the cell after scavenging, and the following evaluation was performed for water discharge. The results are shown in Table 1.
○: 90% or more of water was discharged out of the cell.
X: More than 10% of water remained in the cell.

  In Examples 1 to 6 in which the seal member forming the gas flow path is hydrophilic, the difference in contact angle (Δ contact angle) is small compared to Comparative Examples 1 and 2 in which the seal member is water repellent. Was confirmed. Thereby, it turns out that the movement resistance of generated water is small. Moreover, in Examples 1-6, while water discharge property was all favorable, Comparative Examples 1 and 2 had a large residual amount of water in the cell. Thereby, the sealing member that forms the gas flow path is made hydrophilic, and the difference in hydrophilicity with the gas flow path formed by the separator base material is within a certain range, thereby reducing the water movement resistance. It was found that the water discharge performance was improved, and as a result, the power generation stability of the fuel cell could be secured.

It is a figure which shows a contact angle. 1 is a perspective view of a fuel cell 10 according to the present embodiment. FIG. 3 is a partially cutaway side view of the fuel cell 10 shown in FIG. 2. FIG. 3 is an exploded perspective view of a power generation cell constituting the fuel cell 10 shown in FIG. 2. It is a figure which shows a preferable example as a location of the sealing member which should provide hydrophilicity. It is the elements on larger scale of the dotted line range P in FIG. It is sectional drawing of A-A 'in FIG. It is a figure showing the relationship between the flow of water and a contact angle. It is a figure showing the relationship between the flow of water and a contact angle. It is a figure which shows another example preferable as a location of the sealing member which should provide hydrophilicity.

Explanation of symbols

10 Fuel cell (stack)
12 Power generation cell (single cell)
12a, 12b End power generation cell 14 Laminated body 16a, 16b Terminal plate 18a, 18b Insulating plate 20a, 20b End plate 22 Electrode structure (MEA)
24 1st metal separator 26 2nd metal separator 28 Polymer electrolyte membrane 30 Anode electrode (fuel electrode)
32 Cathode electrode (Air electrode)
40a Oxidant gas inlet communication hole 40b Oxidant gas outlet communication hole 42a Cooling medium inlet communication hole 42b Cooling medium outlet communication hole 44a Fuel gas inlet communication hole 44b Fuel gas outlet communication hole 46 Oxidant gas flow path 48 Fuel gas flow path 50 Cooling medium flow channel 54 First seal member 56 Second seal member 1 Seal member 2 Separator base material 3 Reactive gas flow channel 4 Water droplet

Claims (4)

An electrode structure in which an electrolyte membrane is disposed between an anode electrode and a cathode electrode, and a separator are laminated to form a fuel gas flow path between the anode electrode and a separator adjacent thereto; and A fuel cell in which an oxidant gas flow path is formed between the cathode electrode and a separator adjacent thereto,
A seal member is interposed between the two electrodes and the separator adjacent thereto, and a part of the two gas flow paths is formed by the seal member,
The separator that forms both the gas flow paths has a water contact angle of 80 degrees or less on the surface, and at least a part of the seal member that forms the both gas flow paths adjacent to the separator. The fuel cell whose difference with the contact angle of water of the surface of this is 40 degrees or less.   The gas passages communicate with a gas inlet communication hole and a gas outlet communication hole penetrating in the stacking direction in the separator, and at least a part of the seal member forming the gas flow paths is The fuel cell according to claim 1, wherein the fuel cell is disposed in a communication portion between the gas flow paths and the gas outlet communication hole.   3. The fuel cell according to claim 1, wherein at least a part of the sealing member forming both the gas flow paths is disposed at a boundary portion of a region where the both gas flow paths are formed. An electrode structure in which an electrolyte membrane is disposed between an anode electrode and a cathode electrode, and a separator, and a fuel gas flow path is formed between the anode electrode and a separator adjacent thereto; and A fuel cell manufacturing method for forming an oxidant gas flow path between the cathode electrode and a separator adjacent thereto,
A seal member is interposed between the both electrodes and the separator adjacent thereto, and a part of both gas flow paths is formed by the seal member,
Adjust the difference between the water contact angle on the surface of the separator that forms both gas flow paths and the water contact angle on the surface of at least a part of the sealing member that forms both gas flow paths adjacent to the separator. The manufacturing method of the fuel cell including the process to do.

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