JP2020149895A - Fuel battery cell and manufacturing method thereof - Google Patents

Abstract

To provide a manufacturing method of gas diffusion layer for fuel cell, restraining deterioration of gas diffusion property in a porous base material layer.SOLUTION: In a manufacturing method of fuel battery cell 10 comprising a gas diffusion layer 6 for fuel cell including a porous base material layer 5 and a microporous layer 4, and a separator 7, while bringing the convex part of a member having an irregular shape into contact with one surface of the porous base material layer 5, the other surface is coated with coating liquid for water repellent treatment and thermally dried, subsequently the surface on the opposite side is coated with the coating liquid for microporous layer formation, and then heated and calcined. Thereafter, the separator 7 having an irregular shape is placed on the opposite surface to the surface coated with the coating liquid for microporous layer formation. The separator is placed so that the convex part thereof comes into contact with the location facing the location where the convex part of the member having the irregular shape of the porous base material is brought into contact.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fuel cell and a method for manufacturing the same.

A fuel cell supplies chemical energy directly to electricity by supplying fuel gas (hydrogen gas) and oxidant gas (oxygen gas) to two electrically connected electrodes and electrochemically causing oxidation of the fuel. Convert to energy. This fuel cell is usually configured by stacking a plurality of fuel cell cells (single cells) having a membrane electrode assembly in which an electrolyte membrane is sandwiched between a pair of electrodes. Among them, the polymer electrolyte electrolyte fuel cell using the polymer electrolyte membrane as the electrolyte membrane has advantages such as easy miniaturization and operation at a low temperature, so that it is particularly portable and mobile. It is attracting attention as a body power source.

In the polymer electrolyte fuel cell, the reaction of the following formula (1) proceeds at the anode (fuel electrode) to which hydrogen is supplied.
_{^{H 2 → 2H + + 2e -}} ··· (1)

The electrons generated by the above equation (1) reach the cathode (oxidizing agent electrode) after working under an external load via an external circuit. On the other hand, the protons generated by the above equation (1) move from the anode side to the cathode side in the solid polymer electrolyte membrane by electroosmosis in a state of being hydrated with water.

On the other hand, at the cathode, the reaction of the following equation (2) proceeds.
2H ^＋ ＋ 1 / 2O ₂ ＋ 2e ⁻ → H ₂ O ・ ・ ・ (2)

Therefore, the chemical reaction shown in (3) below proceeds in the entire battery, electromotive force is generated, and electrical work is performed on the external load.
H ₂ + 1 / 2O ₂ → H ₂ O ・ ・ ・ (3)

Each electrode of the anode and the cathode generally has a structure in which a catalyst layer and a gas diffusion layer are laminated in this order from the electrolyte membrane side. The catalyst layer usually contains an electrode catalyst such as platinum or a platinum alloy for promoting the electrode reaction, a polymer electrolyte for ensuring proton conductivity, and a conductive material for ensuring electron conductivity. ing. Further, the gas diffusion layer is usually formed by using a conductive porous body capable of supplying the reaction gas to the catalyst layer, discharging excess water in the electrode, and the like.

In a fuel cell provided with a solid polymer electrolyte membrane represented by a perfluorocarbon sulfonic acid resin membrane, it is important to maintain a wet state of the electrolyte membrane and the catalyst layer in order to ensure ionic conductivity. Therefore, in general, the reaction gas is supplied to the electrode in a pre-humidified state.

On the other hand, in a fuel cell, as described above, water is generated along with power generation. Most of the generated water is discharged to the outside of the cell together with the unreacted gas (reaction gas that did not contribute to the electrode reaction) discharged from the electrode and the humidified water supplied as water vapor. However, a part of the generated water and the humidified water supplied as water vapor to the electrode together with the reaction gas is condensed depending on the environment in the fuel cell and exists in the electrode in a liquid state. At this time, if the condensed water (liquid water) stays in the electrode, the liquid water is clogged, that is, so-called flooding occurs, the supply of the reaction gas is hindered, and the power generation performance deteriorates. In particular, when the fuel cell is operated under high humidification conditions, a large amount of liquid water is generated, so it is necessary to ensure the discharge of liquid water from the electrodes.

Therefore, it is desired that the liquid water in the electrode is quickly discharged to the outside of the cell to prevent the liquid water from staying in the electrode.

As a gas diffusion layer for suppressing this flooding, a microporous layer (also referred to as a microporous layer) having a pore diameter smaller than that of the porous substrate layer is laminated on the porous substrate layer having a porous structure. Those having the above-mentioned structure are known. By providing this fine porous layer, it is said that the ultrafine porous structure of the fine porous layer inhibits the formation of a liquid water film and improves the drainage property of the gas diffusion layer.

Such a fine porous layer is formed by applying a coating liquid for forming a fine porous layer to a porous base material layer and firing it. At the time of this coating, a coating for forming a fine porous layer is formed. A phenomenon called strike-through may occur in which the liquid permeates into the porous base material layer and penetrates through the porous base material layer. If the coating liquid for forming a fine porous layer penetrates into the porous base material layer and strike-through occurs, the gas diffusibility of the gas diffusion layer may decrease.

Many techniques have been proposed in order to prevent strike-through of such a coating liquid for forming a fine porous layer. Patent Document 1 is a method for producing a gas diffusion layer for a fuel cell having a porous base material layer and a fine porous layer, wherein one surface of the porous base material layer is coated to form a fine porous layer. A method has been proposed in which the liquid is applied and a step of applying a coating liquid for water repellent treatment to the other surface of the porous base material layer is provided. Further, Patent Document 2 includes a step of applying a coating liquid for water-repellent treatment to a porous base material layer and then applying a coating liquid for forming a fine porous base material, and transports the porous base material layer. A method for producing a gas diffusion layer for a fuel cell has been proposed in which the contact surface of the roller with the porous base material layer is water repellent.

Japanese Unexamined Patent Publication No. 2015-076371 Japanese Unexamined Patent Publication No. 2015-050073

According to the method for producing a gas diffusion layer described in Patent Document 1 and Patent Document 2, the porous base material layer is coated with a coating liquid for water repellent treatment, or the transfer roller of the porous base material layer is used. By making the surface water-repellent, the amount of strike-through of the coating liquid for forming a fine porous layer from the porous base material layer can be reduced, but the fine porous layer is formed inside the porous base material layer. It is not possible to sufficiently suppress the infiltration of the coating liquid. As a result, in such a conventional method, when the coating liquid for forming the fine porous layer is applied to the porous base material layer, the coating liquid for forming the fine porous layer is inside the porous base material layer. There is a problem that the power generation performance of the fuel cell incorporating the obtained gas diffusion layer is deteriorated by infiltrating and inhibiting the gas diffusivity inside the porous base material layer.

The present invention has been made in view of the above circumstances, and suppresses the infiltration of the coating liquid for forming a fine porous layer into the inside of the porous base material layer, and gas diffusion inside the porous base material layer. It is an object of the present invention to provide a fuel cell having a gas diffusion layer that suppresses deterioration of the property and a method for producing the same.

The present invention achieves the above object by the following means.

<1> A method for manufacturing a fuel cell, which includes a gas diffusion layer for a fuel cell having a porous base material layer and a fine porous layer, and a separator. The following steps (1) The porous material. Applying a water-repellent coating liquid to one surface of the base material layer,
(2) The porous base material layer coated with the water-repellent coating liquid is heated and dried.
(3) Applying the coating liquid for forming a fine porous layer to the surface of the porous base material layer opposite to the surface to which the coating liquid for water repellent treatment is applied.
(4) The porous base material layer coated with the coating liquid for forming the fine porous base material is heated and fired, and (5) for forming the fine porous base material of the porous base material layer. Including arranging a separator having an uneven shape on a surface opposite to the surface on which the coating liquid is applied, in the step (1), the convex portion of the member having an uneven shape is formed on the porous base material layer. The water-repellent coating liquid is applied in a state of being in contact with the surface opposite to the surface on which the water-repellent coating liquid is applied, and the porous group is applied in the step (5). A method for manufacturing a fuel cell, wherein the separator is arranged so that the convex portion of the separator comes into contact with a portion of the material that is in contact with the convex portion of the member having the uneven shape.

<2> The member having the concavo-convex shape used in the step (1) has the concavo-convex phase shifted by half a cycle in the first region and the second region, and the first region is the porous base material. In the plane of the layer, a region ranges from the end of the air introduction portion of the separator to the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion, and the second region is the air. The area from the middle part between the end of the introduction part and the end of the air outlet part to the end part of the air outlet part.
In the step (5), the convex portion of the separator comes into contact with a portion of the second region of the porous base material layer that is in contact with the convex portion of the member having the uneven shape in the step (1). The separator is arranged so as to
The method for manufacturing a fuel cell according to <1>.

<3> A fuel cell cell provided with a gas diffusion layer for a fuel cell having a porous base material layer and a fine porous layer and a separator, which is finely porous in the thickness direction of the porous base material layer. A fuel cell in which the thickness of the quality layer is smaller in the vicinity of a portion where the convex portion of the separator comes into contact with the porous base material layer than in other portions.

<4> The fuel cell has a first region and a second region.
The first region ranges from the end of the air introduction portion of the separator to the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion in the plane of the porous base material layer. It is a region, and the second region is a region in the range from the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion to the end portion of the air outlet portion.
In the first region, the thickness of the microporous layer in the thickness direction of the porous base material layer is larger in the vicinity of the portion where the convex portion of the separator comes into contact with the porous substrate layer than in the other portions. In the second region, the thickness of the fine porous layer in the thickness direction of the porous substrate layer is smaller than the other locations in the vicinity of the portion where the convex portion of the separator contacts the porous substrate layer. The fuel cell according to 3>.

According to the method for producing a fuel cell of the present invention, the coating liquid for forming a fine porous layer is suppressed from penetrating into the porous substrate layer, and the gas diffusivity inside the porous substrate layer is lowered. It is possible to manufacture a fuel cell that can suppress the above. By configuring the fuel cell using the obtained fuel cell, it is possible to suppress the deterioration of the power generation performance of the fuel cell.

It is sectional drawing which shows the structure of a fuel cell. It is a partial sectional view of the fuel cell of this invention. It is explanatory drawing which shows the manufacturing method of the fuel cell of this invention. It is explanatory drawing which shows the coating process of the coating liquid for water repellent treatment. It is explanatory drawing which shows the movement of the water repellent agent after application of the coating liquid for water repellent treatment. It is explanatory drawing which shows the distribution of the water repellent agent in the fuel cell which provided with the gas diffusion layer manufactured by the conventional method. It is explanatory drawing which shows the distribution of the water repellent agent in the coating process of the coating liquid for forming a fine porous layer. It is explanatory drawing which shows the pressing process. It is a schematic diagram which shows the gas flow path in a fuel cell. It is a graph which shows the relationship of the power generation performance with respect to the distance from the air introduction part in a fuel cell. It is a graph which shows the relationship of the water content of an electrolyte membrane with respect to the distance from an air introduction part in a fuel cell. It is a top view of the member which the phase of the unevenness is shifted by half a cycle. It is a perspective view of the member which the phase of the unevenness is shifted by half a cycle. It is a partial sectional view of the 1st region of the fuel cell of this invention.

The method for manufacturing a fuel cell of the present invention is
(1) Applying a water-repellent coating liquid to one surface of the porous base material layer,
(2) The porous base material layer coated with the water-repellent coating liquid is heated and dried.
(3) Applying the coating liquid for forming a fine porous layer to the surface of the porous base material layer opposite to the surface to which the coating liquid for water repellent treatment is applied.
(4) The porous base material layer coated with the coating liquid for forming the fine porous base material is heated and fired, and (5) for forming the fine porous base material of the porous base material layer. Including the arrangement of the separator having an uneven shape on the surface opposite to the surface on which the coating liquid is applied, in the step (1), the convex portion of the member having the uneven shape is formed on the porous base material layer. The water-repellent coating liquid is applied in a state of being in contact with the surface opposite to the surface on which the water-repellent coating liquid is applied, and the porous group is applied in the step (5). The separator is arranged so that the convex portion of the separator comes into contact with the portion of the material facing the convex portion of the member having the uneven shape.

Further, the fuel cell of the present invention is
A gas diffusion layer for a fuel cell having a porous base material layer and a fine porous layer and a separator are provided, and the thickness of the fine porous layer in the thickness direction of the porous base material layer is the thickness of the separator. In the vicinity of the portion where the convex portion contacts the porous base material layer, it is smaller than the other portions.

As described above, in the conventional method for producing a gas diffusion layer, the amount of strike-through of the coating liquid for forming a fine porous layer from the porous substrate layer can be reduced, but the inside of the porous substrate layer can be reduced. It was not possible to sufficiently suppress the infiltration of the coating liquid for forming the fine porous layer, and the coating liquid for forming the fine porous layer that had excessively penetrated into the porous base material layer was porous. By inhibiting the gas diffusivity inside the quality substrate layer, the power generation performance of the fuel cell incorporating the obtained gas diffusing layer is deteriorated.

On the other hand, according to the method of the present invention, the convex portion of the member having an uneven shape is in contact with the surface of the porous base material layer opposite to the surface to which the water-repellent coating liquid is applied. , A water-repellent coating liquid is applied to one surface of the porous base material layer. As a result, the water-repellent agent in the coating liquid for water-repellent treatment is applied to a predetermined portion of the porous base material layer, specifically, a convex portion of a member having an uneven shape in the porous base material layer. The water repellent is unevenly distributed in the porous base material layer after the application of the coating liquid for forming the fine porous layer. The infiltration of the coating liquid for forming the fine porous layer into the portion can be particularly suppressed, and the thickness of the fine porous layer in the thickness direction of the porous base material layer can be reduced. When the obtained gas diffusion layer is incorporated into the fuel cell, the portion where the water repellent is unevenly distributed in the porous base material layer, that is, the portion where the thickness of the fine porous layer is small, is the convexity of the separator in the fuel cell. By aligning the position in contact with the portion, it is possible to suppress a decrease in gas diffusivity in the porous base material layer in the fuel cell, particularly a decrease in gas diffusivity between gas flow paths.

Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist of the present invention.

<Fuel cell configuration>
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell manufactured by the manufacturing method according to the embodiment of the present invention. In FIG. 1, the fuel cell 10 includes a membrane electrode assembly 3, two gas diffusion layers 6, and a pair of separators 7. The membrane electrode assembly 3 includes an electrolyte membrane 1 and two catalyst electrode layers 2 provided on both sides of the electrolyte membrane 1. The electrolyte membrane 1 is a solid polymer thin film that exhibits good proton conductivity in a wet state. The electrolyte membrane 1 is composed of, for example, an ion exchange membrane of a fluorine-based resin such as Nafion (registered trademark). Each of the catalyst electrode layers 2 has a catalyst (not shown) that promotes a chemical reaction between hydrogen and oxygen. Each of the catalyst electrode layers 2 is formed as a dry coating film of a dispersion solution of conductive particles (for example, platinum-supported carbon) carrying a catalyst and a solid electrolyte resin of the same type or similar to the electrolyte membrane 1.

Each of the gas diffusion layers 6 is formed on both sides of the membrane electrode assembly 3. Each of the gas diffusion layers 6 includes a fine porous layer 4 and a porous base material layer 5, the fine porous layer 4 is in contact with the catalyst electrode layer 2, and the porous base material layer 5 is a separator 7. I'm in contact. By compressing the single cell 10 in the stacking direction, each of the gas diffusion layers 6 is pressure-bonded to each catalyst electrode layer 2 and integrated with the membrane electrode assembly 3.

Each of the gas diffusion layers 6 distributes the reaction gas supplied through the gas flow path groove 8 formed in the separator 7 to the entire catalyst electrode layer 2. Further, each of the gas diffusion layers 6 functions as a conductive path between the membrane electrode assembly 3 and the separator 7. During the operation of the fuel cell, the reaction gas supplied to the gas diffusion layer 6 flows through the through pores inside the gas diffusion layer 6 along the plane direction orthogonal to the stacking direction of the gas diffusion layer 6. It reaches the catalyst electrode layer 2 while being diffused.

The microporous layer 4 provided on the surface of the membrane electrode assembly 3 in contact with the catalyst electrode layer 2 is generated by a chemical reaction of the reaction gas because the ultrafine porous structure inhibits the formation of a liquid-water film. It is possible to prevent the generated water from blocking the flow path of the reaction gas, and as a result, secure gas diffusibility and drainage property on the surface in contact with the membrane electrode assembly 3. The porous base material layer 5 provided on the surface in contact with the separator is composed of a conductive porous body, disperses the reaction gas supplied through the gas flow path groove 8, and uniformly supplies the reaction gas to the catalyst layer 2. It has a role of discharging the generated water generated by the oxidation reaction in the catalyst layer 2 to the outside of the single cell.

The pair of separators 7 are plate-like members having conductivity and gas impermeableness, and are composed of, for example, a metal plate. Each of the separators 7 is laminated and arranged on the respective surfaces of the gas diffusion layer 6. Each of the separators 7 is formed with a gas flow path groove 8 through which hydrogen or oxygen as a reaction gas flows.

Although illustration and detailed description are omitted, an insulating seal for preventing fluid leakage such as reaction gas and short circuit between separators 7 is provided on the outside of the membrane electrode assembly 3 and the gas diffusion layer 6 of each single cell 10. A part is provided. Further, a manifold for supplying the reaction gas to the single cell 10 is provided on the outside of the membrane electrode assembly 3 and the gas diffusion layer 6 of the single cell 10.

FIG. 2 shows a partial cross-sectional view of the fuel cell of the present invention. In the gas diffusion layer 6 of the fuel cell of the present invention, the water repellent 23 is unevenly distributed in the porous base material layer 5, and the fine porous layer 4 permeates. The portion 14 in which the water repellent 23 is unevenly distributed and more present corresponds to a portion facing the portion in contact with the rib 9 between the gas flow path grooves 8 of the separator 7 in the fuel cell. Since a large amount of the water repellent 23 is unevenly distributed in this portion, as shown in FIG. 2, the thickness of the fine porous layer 4 in the thickness direction of the porous base material layer 5 is reduced to the convex portion 9 of the separator 7. Is smaller than the other parts in the vicinity of the part in contact with the 5 layers of the porous base material, and passes through the porous base material layer 5 and between the gas flow path grooves 8 of the separator 7 as shown by the arrow. The movement of the gas moving in the gas is not hindered, and the decrease in gas permeability can be suppressed.

<Manufacturing method of fuel cell>
The method for manufacturing a fuel cell of the present invention is, for example, as shown in FIG. 3, a first coating device 20, a first heating device 30, a second coating device 40, and a second heating. It is executed by the manufacturing apparatus 100 including the apparatus 50. In this manufacturing apparatus 100, the long sheet-like porous substrate layer 11 used for forming the porous substrate layer of the gas diffusion layer is conveyed by the conveying roller 12, and the first coating apparatus 20, the first coating apparatus 100, The water-repellent coating liquid coating step (step 1) and the drying step (step 1) corresponding to each device are sent in order to the heating device 30, the second coating device 40, and the second heating device 50. 2), the coating liquid coating step for forming a fine porous layer (step 3), and the firing step (step 4) are executed in this order. Therefore, the first coating device 20, the first heating device 30, the second coating device 40, and the second heating device 50 are sequentially arranged in the transport path in which the base material 11 is conveyed. .. Hereinafter, each step of the method for producing the gas diffusion layer of the present invention will be described.

<Water repellent coating liquid application process (process 1)>
In the water-repellent treatment coating liquid application step, the water-repellent treatment coating liquid is applied to one surface of the porous base material layer. Then, in a state where the convex portion of the member having the uneven shape is in contact with the surface of the porous base material layer opposite to the surface to which the water repellent treatment coating liquid is applied, the water repellent treatment coating liquid is brought into contact with the surface. Is applied.

For example, as shown in FIG. 3, the first coating device 20 corresponding to the coating liquid coating step for water repellent treatment may be composed of a die-type coater. The first coating device 20 may include a die head 21. The die head 21 may be filled with a water-repellent coating liquid. In the water-repellent treatment coating liquid application step, the water-repellent treatment coating liquid is applied to one surface of the porous base material layer 11 by the die head 21. The coating basis weight is, for example, 0.1 to 1 mg / cm ² .

The applied water-repellent coating liquid permeates into the porous base material layer 11 from the coated surface. This makes it possible to apply a water-repellent treatment for imparting water repellency by distributing a water-repellent agent to the surface and the inside of the porous base material layer 11.

The details of the coating liquid coating process for water repellent treatment are shown in FIG. As described above, in the water-repellent treatment coating liquid coating step, the water-repellent treatment coating liquid 22 is applied from the die head 21 to one surface of the porous base material layer 11. Here, the porous base material layer 11 is transported to the first coating device 20 in a state of being in contact with the transport belt 13, and the transport belt 13 has an uneven shape that imitates the shape of the separator 7 constituting the single cell. (That is, it is a member having an uneven shape). Then, in a state where the convex portion of the transport belt 13 is in contact with the surface of the porous base material layer opposite to the surface on which the water-repellent coating liquid is applied, the water-repellent coating liquid 22 is applied. It is applied.

The applied water-repellent coating liquid permeates into the porous base material layer, but as shown in FIG. 5, the water in the water-repellent treatment coating liquid penetrates into the porous base material layer 11. Is moved toward the contact portion between the porous base material layer 11 and the convex portion of the transport belt 13 by the capillary force. At that time, the water repellent 23 in the water repellent coating liquid 22 also moves, and is unevenly distributed in the contact portion between the porous base material layer 11 and the convex portion of the transport belt 13.

Here, the porous base material layer 11 is a sheet-like material having conductivity and porosity that is generally used as a base material of a gas diffusion layer of a fuel cell, for example, carbon paper, carbon cloth, or carbon. A porous sheet material made of carbon fiber such as a non-woven fabric can be used.

The coating liquid for water repellent treatment is a dispersion liquid of a water repellent agent. As the water repellent, a fluorine-based polymer material such as PTFE, PVDF, polyhexafluoropropylene, or tetrafluoroethylene-hexafluoropropylene copolymer, polypropylene, polyethylene or the like can be used. Among these materials, a fluorine-based polymer material, particularly PTFE, is preferably used. For example, by using PTFE as a water repellent and diluting the dispersion of PTFE (particle size: 100 to 400 nm) (concentration: 3 to 5% by mass), the viscosity of the water repellent coating liquid becomes a shear rate of 50 s. It can be adjusted to be ^{1 to} 100 mPa · s at ^-1 .

<Drying process (process 2)>
In the drying step, the porous base material layer coated with the water-repellent coating liquid is heated and dried.

As shown again with reference to FIG. 3, the first heating device 30 corresponding to the drying step may be configured by a general heating furnace. In the drying step, the coated porous base material layer 11 of the water-repellent coating liquid 22 is sequentially fed from the first coating device 20 and moves in the device in order until it is sent out to the outside. In addition, the water-repellent coating liquid 22 is dried by heating the coated porous base material layer 11 with the heater 31. As a result, the water-repellent agent 23 contained in the water-repellent coating liquid 22 imparts water repellency to the porous base material layer 11.

The heating time (drying time) for drying in the first heating device 30 corresponds to the time until the coated porous base material layer 11 sent to the first heating device 30 is sent out to the outside. .. This time is determined by the speed and length of movement of the coated porous substrate layer 11 in the heating device 30. The heating temperature (drying temperature) in the first heating device 30 is a temperature for drying the water-repellent coating liquid 22, and the drying temperature is preferably 50 ° C. to 90 ° C. The heating time (drying time) is set to an appropriate time, for example, about 1 minute to 120 minutes, depending on the coating amount of the coating liquid, the heating temperature, and the like. The upper limit of the heating time is not particularly limited.

<Coating liquid coating process for forming a fine porous layer (process 3)>
In the process of applying the coating liquid for forming the fine porous layer, the coating liquid for forming the fine porous layer is applied to the surface of the porous base material layer opposite to the surface to which the water-repellent coating liquid is applied.

As shown in FIG. 3, the second coating apparatus 40 corresponding to the coating liquid coating step for forming a fine porous layer is composed of, for example, a die-type coater. The second coating device 40 may include a die head 41. The die head 41 may be filled with a coating liquid 42 for forming a fine porous layer for forming a fine porous layer on one surface of the porous base material layer 11. The fine porous layer has a pore diameter smaller than that of the porous base material layer 11. The coating basis weight is, for example, ² to 6 mg / cm ² . The thickness of the coating film of the applied coating liquid 42 for forming a fine porous layer is the speed at which the porous base material layer 11 passes under the die head 41 and the coating for forming a fine porous layer discharged from the die head 41. It is determined by the discharge rate of the working liquid 42.

When the surface of the porous base material layer 11 opposite to the surface to which the fine porous layer forming coating liquid 42 is applied is made water-repellent as in the conventional method, the fine porous layer forming coating liquid is used. When 42 is applied to the porous base material layer 11, as shown in FIG. 6, the coating liquid 42 for forming the fine porous layer has (1) discharge pressure from the die head 41 and (2) porous base material. Three forces, the capillary force inside the layer 11 and (3) the weight of the coating liquid 42 for forming the fine porous layer 42, act to cause an excess in the physical space inside the porous substrate layer 11. Penetration occurs.

The infiltration of the coating liquid 42 for forming the fine porous layer into the inside of the porous base material layer 11 causes the space inside the porous base material layer 11 to be blocked, and causes a decrease in gas permeability. In particular, as shown in FIG. 6, in the vicinity of the contact portion of the porous base material layer 11 with the rib (convex portion) 9 of the separator 7, it passes through the porous base material layer 11 as shown by the arrow. Since the movement of the gas moving between the gas flow path grooves 8 of the separator 7 is hindered, the decrease in gas permeability becomes remarkable. As a result, the gas supply shortage is caused in the vicinity of the contact point of the separator 7 with the rib 9 of the porous base material layer 11, which leads to a decrease in power generation performance.

On the other hand, in the present invention, as shown in FIG. 7, when the coating liquid 42 for forming a fine porous layer is applied, the coating liquid for water repellent treatment is inside the porous base material layer 11. The water repellent 23 permeated by the coating process is unevenly distributed. The portion 14 where the water repellent 23 is unevenly distributed and more present is a member having an uneven shape such as a convex portion of the transport belt 13 in the porous base material layer 11 in the water repellent treatment coating liquid application step. Corresponds to the part that was in contact with the convex part of. This uneven shape imitates the shape of the separator 7 constituting the single cell, and therefore, the portion 14 in which the water repellent 23 is unevenly distributed is a rib between the gas flow path grooves 8 of the separator 7 in the fuel cell. Convex portion) Corresponds to the portion in contact with 9. By unevenly distributing a large amount of the water repellent 23 in this portion, as shown in FIG. 7, when the coating liquid 42 for forming a fine porous layer is applied, the coating liquid 42 for forming a fine porous layer is porous. Although it penetrates into the base material layer 11, the water repellent 23 suppresses the infiltration of the coating liquid 42 for forming the fine porous layer into the portion 14 where the water repellent 23 is unevenly distributed. Will be done. As a result, as shown by the arrow in FIG. 2, the movement of the gas passing through the porous base material layer 11 and moving between the gas flow path grooves 8 of the separator 7 is not hindered, and the gas permeability is lowered. Can be suppressed.

Here, the coating liquid 42 for forming a fine porous layer may be in the form of a paste or a slurry in which conductive particles, a binder and a solvent are mainly mixed and dispersed. Additives such as a dispersant can be added to the coating liquid 42 for forming a fine porous layer, if necessary, but it is preferable that the coating liquid 42 does not contain a metal in order to avoid contamination.

As the conductive particles, carbon particles, particularly carbon particles having an average particle diameter of 20 to 150 nm, for example, carbon black having excellent conductivity and a large specific surface area can be used, and acetylene black having high conductivity is particularly preferable. .. As the binder, fluorine-based polymer materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer, polypropylene, polyethylene, and the like are used. be able to. Among these materials, a fluorine-based polymer material, particularly PTFE, is preferably used. The solvent is not particularly limited, and various liquid agents such as water, methanol, and ethanol can be used. The surfactant as a dispersant is also not particularly limited, and various surfactants such as various nonionic surfactants such as ester type, ether type and ester ether type can be used.

The composition of the coating liquid 42 for forming the fine porous layer is, for example, 70 to 90% by mass of the conductive particles and 15 to 25% by mass of the binder, where the total solid content of the conductive particles, the binder and the dispersant is 100% by mass. %, The dispersant is adjusted to 5 to 15% by mass. The physical properties of the coating liquid 42 for forming a fine porous layer are as follows: a solid content ratio of 15 to 25% by mass, a viscosity of 500 to 2500 mPa · s (50 / s) at a shear rate of 50 s ^-1 , and storage elasticity. The rate may be set to be 500 to 5500 Pa.

The porous base material layer 11 to which the coating liquid 42 for forming the fine porous layer has been applied is conveyed to the second heating device 50.

<Baking step (step 4)>
In the firing step, the porous base material layer coated with the coating liquid for forming a fine porous layer is heated and fired.

As shown again with reference to FIG. 3, the second heating device 50 corresponding to the firing step may be configured by a general heating furnace. In the firing step, the coated porous base material layer 11 of the coating liquid 42 for forming a fine porous layer is sequentially fed from the second coating apparatus 40, moves in order in the apparatus, and is sent out to the outside. By heating the coated base material 11 with the heater 51, the coating film is fired with the coating liquid 42 for forming the fine porous layer. As a result, the coating film of the coating liquid 42 for forming the fine porous layer is fixed on the porous base material layer 11 as a fine porous layer, and the porous base material layer and the fine porous layer are laminated. A sheet-like gas diffusion layer is formed.

The heating time (firing time) for firing in the heating device 50 corresponds to the time until the coated porous base material layer 11 sent to the firing device 50 is sent out to the outside. This time is determined by the speed and length of movement of the coated porous substrate layer 11 in the heating device 50. The heating temperature (firing temperature) in the heating device 50 is a temperature for heat-sealing the conductive particles and the binder in the coating liquid 42 for forming a fine porous layer, preferably 250 ° C. or higher. The temperature is preferably set to 400 ° C. or higher. The upper limit of the heating temperature is not particularly limited. The heating time (baking time) is set to an appropriate time, for example, about 1 minute to 120 minutes, depending on the coating amount of the coating liquid for forming the fine porous layer, the heating temperature, and the like. The upper limit of the heating time is not particularly limited.

The long sheet-like gas diffusion layer in which the porous base material layer and the fine porous layer are laminated, which is produced in the firing step, is cut into a desired shape by a general cutting machine (not shown). A gas diffusion layer having a desired shape is formed.

<Separator placement process (process 5)>
In the separator placement step, the separator is placed on the gas diffusion layer obtained in step 4.

As shown in FIG. 2, the separator 7 is a plate-like member having conductivity and gas impermeableness, and is composed of, for example, a metal plate. The separator 7 has an uneven shape in its cross section, the concave portion corresponds to the gas flow path groove 8 through which hydrogen or oxygen of the reaction gas flows, and the convex portion corresponds to the rib 9 in contact with the porous base material layer 5. The separator 7 is arranged so that the convex portion 9 of the separator comes into contact with the portion 14 of the porous base material 5 that is in contact with the convex portion of the member having an uneven shape.

By arranging the separator 7 in this way, the thickness of the microporous layer 4 in the thickness direction of the porous base material layer 5 is increased in the vicinity of the portion where the convex portion 9 of the separator 7 comes into contact with the porous base material 5 layer. Since it is smaller than the other parts, the movement of the gas that passes through the porous base material layer 5 and moves between the gas flow path grooves 8 of the separator 7 as shown by the arrow is not hindered, and the gas is not hindered. It is possible to suppress a decrease in permeability.

In the present invention, it is preferable to perform the pressing step in the pressing apparatus 60 after the drying step and before the coating liquid coating step for forming the fine porous layer. In this pressing step, for example, as shown in FIG. 8, the porous base material layer 11 dried in the drying device 30 in the drying step is sent to the pressing device 60 in contact with the transport belt 13 and at a predetermined position. Is pressed by two press plates 61. At this time, the transport belt 13 is provided with a protrusion 15 for positioning at a predetermined position, and a recess can be formed at a predetermined position on the porous base material layer by pressing.

As described above, in the water repellent treatment coating liquid application step, the water repellent treatment coating liquid is applied to the porous base material layer 11 in contact with the transport belt 13, and as a result, the porous base material layer is applied. A large amount of the water repellent 23 is unevenly distributed in the contact portion of the transport belt 13 with the convex portion of the transport belt 13. The uneven shape of the transport belt 13 imitates the uneven shape constituting the gas flow path groove 8 of the separator, and the contact portion of the porous base material layer 11 with the convex portion of the transport belt 13, that is, water repellency. It is necessary to arrange the convex portion 9 of the rib forming the gas flow path groove 8 of the separator at a portion facing the portion 14 where a large amount of the agent is unevenly distributed.

As described above, by forming a recess at a predetermined position on the porous base material layer in the pressing process, accurate positioning with the separator can be performed by using this recess as a mark in the subsequent stage of forming the fuel cell. It will be possible.

By the way, in the fuel cell, as shown in FIG. 9, a fuel agent gas or an oxidant gas is introduced into one of the manifolds 91, and this gas passes through the gas flow path 8 and is discharged from the manifold 92.

When gas, for example, air is introduced into the manifold 91, the introduced air diffuses in the gas diffusion layer. In the fuel cell of the present invention, as shown in FIG. 2, the water repellent 23 is unevenly distributed in the porous base material layer 5 constituting the gas diffusion layer 6, and the fine porous layer 4 permeates. .. The portion 14 in which the water repellent 23 is unevenly distributed and more present corresponds to a portion facing the portion in contact with the rib 9 between the gas flow path grooves 8 of the separator 7 in the fuel cell. Since a large amount of the water repellent 23 is unevenly distributed in this portion, the thickness of the fine porous layer 4 in the thickness direction of the porous base material layer 5 is such that the convex portion 9 of the separator 7 is the porous base material 5. In the vicinity of the part in contact with the layer, it is smaller than the other parts, and as shown by the arrow, the movement of gas passing through the porous base material layer 5 and moving between the gas flow path grooves 8 of the separator 7 It is unimpeded and has improved gas diffusivity.

However, when this gas diffusivity is high, particularly in the region near the inlet of the gas flow path, specifically, in the plane of the porous base material layer, from the end portion on the manifold 91 side, which is the air introduction portion of the separator, It has been found that the performance of the fuel cell may deteriorate in the region up to the intermediate portion between the end portion of the air introduction portion and the end portion on the manifold 92 side which is the air outlet portion.

Specifically, the fuel cell of the present invention, which suppresses the infiltration of the coating liquid for forming a fine porous layer into a predetermined portion of the porous base material, and the formation of the fine porous layer on the porous base material. For a conventional fuel cell that does not suppress the infiltration of the coating liquid, the relationship of power generation performance with respect to the distance from the air introduction portion is expected as shown in FIG.

That is, in the region from the end of the air introduction portion of the separator to the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion, the porous substrate is microporous to a predetermined portion. When a gas diffusion layer that suppresses the penetration of the coating liquid for forming a layer is used, a gas diffusion layer that does not suppress the penetration of the coating liquid for forming a fine porous layer into the porous substrate was used. The power generation performance is lower than in the case, while as the distance from the air introduction part increases, from the middle part between the end part of the air introduction part and the end part of the air outlet part, the end part of the air outlet part. In the range up to, when a gas diffusion layer that does not suppress the infiltration of the coating liquid for forming the microporous layer into the porous substrate is used, the porous substrate is microporous to a predetermined location. It is expected that the power generation performance will be lower than when a gas diffusion layer that suppresses the penetration of the coating liquid for forming the layer is used.

Therefore, the fuel cell of the present invention, which suppresses the infiltration of the coating liquid for forming a fine porous layer into a predetermined portion of the porous base material, and the coating for forming a fine porous layer on the porous base material The water content of the electrolyte membrane was predicted when power was generated in a conventional fuel cell that does not suppress the infiltration of liquid. Then, as shown in FIG. 11, the relationship of the water content of the electrolyte membrane with respect to the distance from the air introduction portion is predicted.

That is, in the region from the end of the air introduction portion of the separator to the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion, the porous substrate is microporous to a predetermined portion. When a gas diffusion layer that suppresses the infiltration of the coating liquid for forming the quality layer was used, a gas diffusion layer that did not suppress the penetration of the coating liquid for forming the fine porous layer into the porous substrate was used. The water content of the electrolyte membrane decreased as compared with the case. On the other hand, as the distance from the air introduction portion increases, the porous group is formed in the region from the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion to the end portion of the air outlet portion. When a gas diffusion layer that does not suppress the infiltration of the coating liquid for forming the fine porous layer into the material is used, and when the coating liquid for forming the fine porous layer is infiltrated into a predetermined portion of the porous base material. It was predicted that no decrease in the water content of the electrolyte membrane was observed when the gas diffusion layer with suppressed pouring was used.

From the above results, in the region from the end of the air introduction portion of the separator to the intermediate portion between the end of the air introduction portion and the end of the air outlet portion, the gas diffusivity is too high and the electrolyte It is considered that the film dries and the proton conductivity decreases, resulting in a decrease in power generation performance.

Therefore, in another aspect of the present invention, as a member having a concavo-convex shape used in the step of applying the water-repellent coating liquid to one surface of the porous base material layer, the first region and the second A member whose unevenness is out of phase by half a cycle is used in the region. Here, the first region is a range from the end of the air introduction portion of the separator to the intermediate portion between the end of the air introduction portion and the end of the air outlet portion in the plane of the porous base material layer. The second region is a region in the range from the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion to the end portion of the air outlet portion. Specifically, as shown in FIGS. 12 and 13, the member having such an uneven shape includes a groove (recess) 16 and a rib (recessed portion) 16 in a first region which is a region on the left side of the member 13 having an uneven shape. The groove (concave portion) 16 and the rib (convex portion) 17 in the second region, which is the left region of the member 13 having the concave-convex shape, are the end portion of the air introduction portion and the end portion of the air outlet portion. The phase of the unevenness is shifted by half a cycle in the middle part between the two.

In the step (1), the convex portion of the porous base material layer is applied by applying the water-repellent treatment coating liquid in a state where the convex portion of the member having the uneven shape is in contact with the porous base material layer. The water repellent is unevenly distributed in the place facing the place in contact with. Therefore, by using a member whose unevenness is out of phase by half a cycle in the first region and the second region, the portion where the water repellent is unevenly distributed in the first region and the second region is also half a cycle. It will shift.

When the coating liquid for forming a fine porous film is applied to the porous film in which the portion where the water repellent is unevenly distributed is shifted by half a cycle, the coating liquid for forming the fine porous film is applied to the portion where the water repellent is unevenly distributed. Penetration is suppressed and the thickness of the fine porous membrane is reduced. However, in the first region and the second region, the locations where the water repellent is unevenly distributed are deviated by half a cycle, so that the locations where the fine porous membrane is thin are also in the first region and the second region. It will be off by half a cycle.

It was obtained by arranging the separator in the second region of the gas diffusion layer thus obtained so that the convex portion of the separator contacts the portion facing the convex portion of the member having the uneven shape. In the fuel cell, in the second region, as shown in FIG. 2, the portion 14 in which the water repellent 23 is unevenly distributed and more is present is a rib between the gas flow path grooves 8 of the separator 7 in the fuel cell. Corresponding to the portion facing the portion in contact with 9, the thickness of the microporous layer 4 in the thickness direction of the porous substrate layer 5 is in the vicinity of the portion where the convex portion 9 of the separator 7 contacts the porous substrate 5 layer. , It is smaller than other parts, and as shown by the arrow, the movement of gas that passes through the porous base material layer 5 and moves between the gas flow path grooves 8 of the separator 7 is not hindered, and the gas is not hindered. It is possible to suppress a decrease in permeability.

On the other hand, in the first region, as shown in FIG. 14, the portion 14 in which the water repellent 23 is unevenly distributed and more present corresponds to the portion facing the gas flow path groove 8 of the separator 7 in the fuel cell. However, the thickness of the microporous layer 4 in the thickness direction of the porous substrate layer 5 is thicker in the vicinity of the portion where the convex portion 9 of the separator 7 comes into contact with the porous substrate 5 layer than in other portions. , The movement of the gas passing through the porous base material layer 5 and moving between the gas flow path grooves 8 of the separator 7 is partially hindered, and the gas diffusivity is suppressed, thereby suppressing the drying of the electrolyte membrane. it can.

1 Solid polymer electrolyte membrane 2 Catalytic electrode layer 3 Membrane electrode assembly 4 Fine porous layer 5 Porous base material layer 6 Gas diffusion layer 7 Separator 8 Gas flow path groove 10 Fuel cell cell 11 Porous base material layer 12 Conveyor roller 13 Conveyance belt (or uneven member)
15 Protrusions 16 Convex 17 Concave 20 Water repellent coating device 21 Die head 22 Water repellent coating liquid 23 Water repellent 30 First heating device 31 Heater 40 Second coating device 41 Die head 42 Microporous Coating liquid for layer formation 50 Second heating device 51 Heater 60 Press device 61 Press plate

Claims (4)

A method for manufacturing a fuel cell cell including a gas diffusion layer for a fuel cell having a porous base material layer and a fine porous layer and a separator. The following steps (1) The porous base material layer Applying a water-repellent coating solution to one surface,
(2) The porous base material layer coated with the water-repellent coating liquid is heated and dried.
(3) Applying the coating liquid for forming a fine porous layer to the surface of the porous base material layer opposite to the surface to which the coating liquid for water repellent treatment is applied.
(4) The porous base material layer coated with the coating liquid for forming the fine porous base material is heated and fired, and (5) for forming the fine porous base material of the porous base material layer. Including arranging a separator having an uneven shape on a surface opposite to the surface on which the coating liquid is applied, in the step (1), the convex portion of the member having an uneven shape is formed on the porous base material layer. The water-repellent coating liquid is applied in a state of being in contact with the surface opposite to the surface on which the water-repellent coating liquid is applied, and the porous group is applied in the step (5). A method for manufacturing a fuel cell, wherein the separator is arranged so that the convex portion of the separator comes into contact with a portion of the material that is in contact with the convex portion of the member having the uneven shape. The member having the concave-convex shape used in the step (1) is out of phase with the unevenness by half a cycle in the first region and the second region, and the first region is the surface of the porous base material layer. Within, the region ranges from the end of the air introduction portion of the separator to the intermediate portion between the end of the air introduction portion and the end of the air outlet portion, and the second region is the air introduction portion of the air introduction portion. The area from the middle part between the end part and the end part of the air outlet part to the end part of the air outlet part.
In the step (5), the convex portion of the separator comes into contact with a portion of the second region of the porous base material layer that is in contact with the convex portion of the member having the uneven shape in the step (1). The separator is arranged so as to
The method for manufacturing a fuel cell according to claim 1. A fuel cell cell provided with a gas diffusion layer for a fuel cell having a porous base material layer and a fine porous layer and a separator, which is a fine porous layer in the thickness direction of the porous base material layer. A fuel cell whose thickness is smaller in the vicinity of a portion where the convex portion of the separator contacts the porous base material layer than in other portions. The fuel cell has a first region and a second region.
The first region ranges from the end of the air introduction portion of the separator to the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion in the plane of the porous base material layer. It is a region, and the second region is a region in the range from the intermediate portion between the end portion of the air introduction portion and the end portion of the air outlet portion to the end portion of the air outlet portion.
In the first region, the thickness of the microporous layer in the thickness direction of the porous base material layer is larger in the vicinity of the portion where the convex portion of the separator comes into contact with the porous substrate layer than in the other portions. In the second region, the thickness of the microporous layer in the thickness direction of the porous base material layer is smaller than the other parts in the vicinity of the portion where the convex portion of the separator contacts the porous base material layer. Item 3. The fuel cell according to Item 3.

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