Manufacturing method for fuel cell

A manufacturing method for a fuel cell includes the steps of: (a) preparing a stack and separators in a pair arranged in such a manner as to hold the stack therebetween; (b) forming a separator-bonded stack by bonding the separators in a pair and a sealing part to each other; and (c) warping a membrane electrode assembly with the bonded sealing part in a gap by reducing the temperature of the separator-bonded stack to cause thermal shrinkage of the separators in a pair, thereby moving the sealing part with the bonded separators in a pair inward.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese patent application No. 2020-026059 filed on Feb. 19, 2020, the disclosure of which is hereby incorporated in its entirety by reference into this application.

BACKGROUND

Field

This disclosure relates to a fuel cell.

Related Art

According to a technique conventionally known relating to a fuel cell forming a fuel cell device, to reduce the occurrence of a crack in a membrane electrode assembly due to drying shrinkage of the membrane electrode assembly, the membrane electrode assembly is arranged in a state of being warped in normal humidity (Japanese Patent Publication No. 5825238). According to the conventional technique, after formation of a membrane electrode gas diffusion layer assembly, a sealing part and a separator are stacked in relative humidity of 0%, namely, in a drying state. Next, the stacked target is hot-pressed to be formed into a cell and then the membrane electrode assembly is stretched to be warped by setting relative humidity at normal humidity.

The conventional technique requires a step of drying the membrane electrode assembly and requires formation into a cell in the dried state. This causes a risk of complication of control such as humidity control during manufacturing process.

SUMMARY

According to one aspect of this disclosure, a manufacturing method for a fuel cell is provided. The manufacturing method for the fuel cell includes the steps of: (a) preparing a stack and separators in a pair arranged in such a manner as to hold the stack therebetween, the stack including a membrane electrode assembly having a first surface and a second surface on the opposite side of the first surface, a frame-like sealing part bonded to an outer edge of the first surface, a first gas diffusion layer having a smaller outer shape than the membrane electrode assembly in a plan view and arranged at the first surface across the sealing part and a gap, and a second gas diffusion layer arranged at the second surface; (b) forming a separator-bonded stack by heating the separators in a pair to thermally expand the separators in a pair and move the separators in a pair outward relative to the sealing part, and then bonding the separators in a pair and the sealing part to each other; and (c) warping the membrane electrode assembly with the bonded sealing part in the gap by reducing the temperature of the separator-bonded stack to cause thermal shrinkage of the separators in a pair, thereby moving the sealing part with the bonded separators in a pair inward, the step (c) being performed after the step (b).

DETAILED DESCRIPTION

FIG.1is an exploded perspective view briefly showing the configuration of a fuel cell (unit cell)100of a fuel cell device according to a first embodiment of this disclosure.FIG.2is a plan view of the unit cell100.FIG.3is a cross-sectional view taken along3-3inFIG.2.FIGS.1,2, and3, and all the drawings referred to later schematically show parts of the unit cell100of this embodiment. Hence, the sizes of the parts shown in the drawings do not indicate the particular sizes thereof.

The fuel cell device of this embodiment has a stack structure with a plurality of stacked unit cells100each shown inFIG.1. While the fuel cell device of this embodiment is a solid polymer fuel cell device, it may be a different type of fuel cell device such as a solid oxide fuel cell device.

As shown inFIG.3, the unit cell100includes a membrane electrode assembly10(hereinafter also called an MEA10), a first gas diffusion layer15, a second gas diffusion layer17, a sealing part25, and separators40and50in a pair. The direction in which the membrane electrode assembly10, the first gas diffusion layer15, the second gas diffusion layer17, and the separators40and50in a pair are stacked is also called a stacking direction. InFIG.3, the stacking direction is a vertical direction.

The MEA10is held between the first gas diffusion layer15and the second gas diffusion layer17. A structure in which the first gas diffusion layer15and the second gas diffusion layer17are stacked on the MEA10is also called a membrane electrode gas diffusion layer assembly (MEGA)18. The sealing part25is bonded to an outer edge of the MEA10. A structure in which the sealing part25is bonded to the MEGA18is also called a MEGA20with seal. In this embodiment, the MEGA20with seal is arranged between the separators40and50in a pair. The surface of the first separator40on the opposite side of the surface thereof contacting the MEGA20with seal is provided with a gasket62(FIG.2). The gasket62is for sealing a fluid flow path between the unit cells100adjacent to each other. The gasket62may be configured using an elastic body. Examples of the elastic body include rubber and thermoplastic elastomer. The gasket62is bonded to the first separator40with an adhesive, for example.

The membrane electrode assembly10has a rectangular outer shape. As shown inFIG.3, the membrane electrode assembly10includes a first surface10faand a second surface10fbon the opposite side of the first surface10fa. The first surface10faand the second surface10fbform two main surfaces of the membrane electrode assembly10. The membrane electrode assembly10includes an electrolyte membrane13, a cathode14, and an anode16. The electrolyte membrane13is an ion-exchange membrane having proton conductivity made of a polymer electrolyte material such as fluororesin, for example, and exhibits favorable proton conductivity in a humid condition. The cathode14is a catalyst electrode layer and is formed on one surface of the electrolyte membrane13. The anode16is a catalyst electrode layer and is formed on the other surface of the electrolyte membrane13on the opposite side of the one surface thereof. The cathode14and the anode16are porous members with pores, and are formed by applying a polymer electrolyte coating having proton conductivity to conductive particles that may be carbon particles, for example, supporting a catalyst that may be platinum or a platinum alloy, for example. The polymer electrolyte forming the cathode14and the anode16may be a polymer of the same type as or a different type from the polymer electrolyte forming the electrolyte membrane13.

As shown inFIG.1, the sealing part25is a frame-like member. The sealing part25is formed using resin such as thermoplastic resin. The sealing part25has an opening area25aformed at the center as an area for holding the MEA10(MEGA18). The sealing part25is provided with a plurality of slit parts39to allow the flow of an oxidizing gas and a fuel gas. The slit parts39will be described later in detail.

The sealing part25is made of a material that may, for example, be modified polyolefin such as modified polypropylene given adhesion properties by introduction of a functional group (ADMER (registered trademark) available from Mitsui Chemicals, Inc., for example). As shown inFIG.3, the sealing part25and the first separator40, and the sealing part25and the second separator50are adhesively bonded to each other by hot-pressing. If resin without particular adhesion properties is used for forming the sealing part25, a layer of an adhesive to exert adhesion properties in response to hot-pressing may be formed on a surface of the sealing part25, for example. In this case, the sealing part25may be made of resin selected from a group consisting of polypropylene (PP), phenolic resin, epoxy resin, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN), for example. The layer of the adhesive formed on the surface of the sealing part25may contain a silane coupling agent, for example. In this embodiment, the adhesive bonding between the sealing part25and each of the separators40and50means that this adhesive bonding is realized as thermal welding by means of hot-pressing. Namely, the adhesive bonding between the sealing part25and each of the separators40and50means that a hydrogen bond or a covalent bond is formed as a result of progress of chemical reaction between the surface of the sealing part25and the surface of each of the separators40and50. As shown inFIG.3, the sealing part25is bonded with an adhesive26to an outer edge of the first surface10fa.

The first gas diffusion layer15and the second gas diffusion layer17are made of a material having gas permeability and electron conductivity. For example, the first gas diffusion layer15and the second gas diffusion layer17may be made of a metallic material such as foam metal or metal mesh, or may be made of a carbon material such as carbon cloth or carbon paper. As shown inFIG.3, the first gas diffusion layer15and the second gas diffusion layer17have different sizes. More specifically, the outer shape of the first gas diffusion layer15is smaller than that of the second gas diffusion layer17in a plan view. The outer shape of the first gas diffusion layer15is smaller than that of the membrane electrode assembly10in a plan view. The outer shape of the second gas diffusion layer17is substantially equal to that of the membrane electrode assembly10in a plan view. In this embodiment, a plan view means a view taken when the unit cell100is seen from a direction vertical to the first surface10fa.

The first gas diffusion layer15is arranged at the first surface10faacross the sealing part25and a gap70. Namely, the first gas diffusion layer15is arranged in the opening area25aof the sealing part25. The second gas diffusion layer17is arranged at the second surface10fb. The gap70has a size that preferably allows accommodation of a warped part12of the membrane electrode assembly10. An interval between the sealing part25and the first gas diffusion layer15, which corresponds to the dimension of the gap70, is 0.5 mm, for example. The membrane electrode assembly10includes the warped part12arranged in the gap70at least in normal humidity. Normal humidity means a state in which relative humidity is 65% plus or minus 20% (the JIS standard, JIS Z 8703). An area of the unit cell100in which the anode16and the cathode14, which are electrodes, are arranged, functions as a power generator27contributing to power generation. In this embodiment, the power generator27is an area inward from the gap70in a plan view of the unit cell100.

As shown inFIG.1, the first separator40and the second separator50are rectangular plate-like members. The first separator40and the second separator50are arranged in such a manner as to hold the MEGA20with seal therebetween. The first separator40and the second separator50have a coefficient of linear expansion higher than that of each of the membrane electrode assembly10, the first gas diffusion layer15, and the second gas diffusion layer17. As shown inFIG.3, the first separator40is located on the first surface10faside and is arranged in such a manner as to contact the first gas diffusion layer15and the sealing part25. The second separator50is located on the second surface10fbside and is arranged in such a manner as to contact the second gas diffusion layer17and the sealing part25. The first separator40and the second separator50are made of a gas-impermeable and conductive material that may be a carbon material such as gas-impermeable dense carbon prepared by compressing carbon, or may be a metallic material such as pressed stainless steel or titanium, for example. In this embodiment, the first separator40and the second separator50are formed by pressing titanium. The surface of the first separator40and the second separator50facing the MEGA18is provided with a flow path groove for flow of a reactive gas used for electrochemical reaction. This flow path groove is defined by a recess and a projection formed at the surface of the first separator40and the second separator50. These recess and projection are omitted fromFIG.1. As shown inFIG.3, a part of the first separator40in contact with the sealing part25is also called an outer peripheral part43, and a part of the first separator40inward from the outer peripheral part43, namely, closer to the center than the outer peripheral part43of the first separator40in a plan view is also called a center part44.

As shown inFIG.1, each of the first separator40, the second separator50, and the sealing part25is provided with manifold holes31to36for forming manifolds at positions differing from each other in the stacking direction. Each of the manifolds is a flow path penetrating the fuel cell device with the stacked unit cells100in the stacking direction, communicating with an in-cell gas flow path formed in the unit cell100or with a cell-to-cell coolant flow path formed between the unit cells100adjacent to each other, and used for the flow of a reactive gas or a coolant. More specifically, the manifold holes31and36form an oxidizing gas manifold for supply and discharge of the oxidizing gas to and from an in-cell oxidizing gas flow path. The manifold holes33and34form a fuel gas manifold for supply and discharge of the fuel gas to and from an in-cell fuel gas flow path. The manifold holes32and35form a coolant manifold for supply and discharge of the coolant to and from the cell-to-cell coolant flow path. The slit parts39include slits that are a plurality of elongated holes extending from outer peripheries and their vicinities of the manifold holes31,33,34, and36toward an outer periphery and its vicinity of the MEGA18. The slits form communication flow paths for communicating the manifold holes31,33,34, and36with the corresponding in-cell gas flow paths within the unit cell100when the sealing part25is caught between the separators40and50in a pair. Specifically, the manifold holes33and34are communicated with the in-cell fuel gas flow path, and the manifold holes31and36are communicated with the in-cell oxidizing gas flow path.

FIG.4is a view for explaining a manufacturing device200for the unit cell100. The manufacturing device200is a device for bonding the sealing part25and the first separator40to each other and bonding the sealing part25and the second separator50to each other by hot-pressing a unit cell100A before bonding. The unit cell100A before bonding is a unit cell in a state before the bonding between the sealing part25and the first separator40and before the bonding between the sealing part25and the second separator50.

The manufacturing device200includes a first manufacturing device201for heating the first separator40and a second manufacturing device202for heating the second separator50.

The first manufacturing device201includes a first heater unit210, a first member213, a second member214, a shaft240, a support member219, and an elastic body212. An actuator not shown in the drawings allows the first manufacturing device201to move up and down. The first heater unit210includes a body211made of metal such as iron or stainless steel, and a heating part218arranged in the body211. The body211has a shape like a rectangular solid. The heating part218is used for heating the body211. For example, the heating part218can utilize a heating wire or a heat pipe.

The first member213is formed integrally with the first heater unit210. The first member213is increased in temperature by heat transferred from the first heater unit210. The first member213presses and heats the first separator40. More specifically, the first member213contacts the outer peripheral part43of the first separator40in contact with the sealing part25to heat the outer peripheral part43by heat transfer. The first member213is attached to a surface215of the first heater unit210facing the second manufacturing device202. More specifically, the first member213is arranged in a frame-like pattern at an edge portion of the rectangular surface215. The first member213is made of metal such as iron or stainless steel.

The second member214is a member separate from the first member213. The second member214is supported by the first heater unit210in such a manner as to be movable up and down independently of the first heater unit210. The second member214is inward from the first member213arranged in a frame-like pattern, namely, arranged in the frame of the first member213. The second member214has a rectangular solid shape. The second member214is increased in temperature by heat transferred from the first heater unit210. The second member214contacts the center part44of the first separator40to heat the center part44by heat transfer. The center part44is a part mainly overlapping the power generator27. The second member214is made of metal such as iron or stainless steel.

The shaft240is passed through the first heater unit210. The shaft240has a lower end arranged in the second member214. The support member219is attached to the lower end of the shaft240to support the second member214. More specifically, the support member219regulates the motion of the second member214in such a manner as to prevent the second member214from moving farther from the first heater unit210by a predetermined distance or more. In this embodiment, the support member219is a bolt and the motion of the second member214is regulated with the head of the bolt.

The elastic body212biases the second member214toward the first separator40. Namely, the elastic body212biases the second member214in a direction of moving farther from the first heater unit210. The elastic body212is a compression coil spring, for example. The elastic body212is arranged between the first heater unit210and the second member214. The second member214presses the first separator40using the force of the elastic body212. Pressing the first separator40with the second member214using the force of the elastic body212allows application of force within a predetermined range to the first separator40. This achieves more efficient transfer of heat from the second member214to the first separator40. At this point, the second member214presses the center part44of the first separator40. The center part44is a part where the membrane electrode assembly10, the first gas diffusion layer15, and the second gas diffusion layer17overlap each other. Using the elastic body212reduces the probability of application of excessive pressing force to the first separator40, thereby preventing damage to the membrane electrode assembly10, the first gas diffusion layer15, or the second gas diffusion layer17.

The second manufacturing device202is arranged on the opposite side of the first manufacturing device201across an area for arrangement of the unit cell100A before bonding. The second manufacturing device202is arranged below the first manufacturing device201. The second manufacturing device202includes a second heater unit230and a third member232.

The second heater unit230includes a body231made of metal such as iron or stainless steel, and a heating part238arranged in the body231. The body231has a shape like a rectangular solid. The heating part238is used for heating the body231. For example, the heating part238can utilize a heating wire or a heat pipe.

The third member232is formed integrally with the second heater unit230. The third member232is increased in temperature by heat transferred from the second heater unit230. The third member232has a shape like a rectangular solid. The third member232is larger in size than the cell100A before bonding in a plan view.

The manufacturing device200further includes a stopper member250for maintaining an interval between the first member213and the third member232at a predetermined value or more. The stopper member250includes a first protruding member255protruding from the first member213toward the third member232, and a second protruding member256protruding from the third member232toward the first member213. When the first manufacturing device201moves toward the second manufacturing device202to make the interval between the first member213and the third member232reach the predetermined value, the first protruding member255and the second protruding member256come into abutting contact with each other. By doing so, the interval between the first member213and the third member232is maintained at the predetermined value or more. This reduces the probability of application of excessive load from the manufacturing device200to the unit cell100A before bonding, thereby preventing damage to the unit cell100A before bonding.

FIG.5is a schematic view showing the position of the manufacturing device200and that of the unit cell100A before bonding relative to each other. As shown inFIG.5, the first member213and the second member214of the manufacturing device200overlap with the entire first separator40in a plan view. Namely, the first separator40is heated entirely using the first member213and the second member214. While not shown inFIG.5, the third member232overlaps with the entire second separator50in a plan view. Namely, the second separator50is heated entirely using the third member232.

FIG.6is a flowchart showing process of manufacturing the unit cell100.FIG.7is a first view for explaining the manufacturing process.FIG.8is a second view for explaining the manufacturing process.FIG.9is a third view for explaining the manufacturing process.

First, in step S10and step S20, the unit cell100A before bonding is prepared. As shown inFIG.7, the unit cell100A before bonding includes a stack20A, and the separators40and50in a pair. The stack20A includes the membrane electrode assembly10, the frame-like sealing part25bonded with the adhesive26to the outer edge of the first surface10faof the membrane electrode assembly10, the first gas diffusion layer15, and the second gas diffusion layer17. In the stack20A, the membrane electrode assembly10extends straight without being warped in the gap70.

In step S10, the membrane electrode assembly10and the sealing part25are bonded to each other to form a seal-integrated MEA. More specifically, the sealing part25is adhesively bonded with the adhesive26to the outer edge of the first surface10faof the membrane electrode assembly10. In step S20performed after step S10, the seal-integrated MEA, the first gas diffusion layer15, the second gas diffusion layer17, and the separators40and50in a pair are stacked. More specifically, as shown inFIG.7, the first gas diffusion layer15is arranged at the first surface10faacross the sealing part25and the gap70. The second gas diffusion layer17is arranged at the second surface10fb. Further, the separators40and50in a pair are arranged in such a manner as to hold the stack20A therebetween. At this point, an area of each of the separators40and50in a pair overlapping the sealing part25in a plan view is called a first area FA. An area of each of the separators40and50in a pair overlapping an area in the stack20A inward from the sealing part25and inside the frame of the sealing part25in a plan view is called a second area SA.

Next, in step S30, the separators40and50in a pair and the sealing part25are bonded to each other to form a separator-bonded stack100B. More specifically, as shown inFIG.8, the separators40and50in a pair are heated using the manufacturing device100, thereby thermally expanding the separators40and50in a pair to move the separators40and50in a pair outward relative to the sealing part25. Then, the separators40and50in a pair and the sealing part25are bonded to each other. In step S30, the prepared unit cell100A before bonding is installed on the manufacturing device200, and the separators40and50in a pair and the sealing part25are bonded to each other by hot-pressing. Namely, the separators40and50in a pair are heated under pressure to be bonded to the sealing part25. A condition for the hot-pressing is settable in a range allowing bonding of the sealing part25to the separators40and50in a pair. For example, the hot-pressing is performed under conditions of 160° C. (in Celsius) and 30 seconds. The temperature as a condition for hot-pressing is the temperature of each of the separators40and50in a pair, for example. Humidity is not particularly limited as a condition for the hot-pressing. The hot-pressing may be performed in normal humidity.

As shown inFIG.4, the first heater unit210and the second heater unit230are arranged in such a manner as to overlap the entire first separator40in a plan view. Thus, the first separator40is heated entirely in step S30. More specifically, the first area FA of the first separator40is heated by the first member213, and the second area SA of the first separator40is heated by the second member214. The third member232is arranged in such a manner as to overlap the entire second separator50in a plan view. Thus, the second separator50is heated entirely in step S30. The heating step is performed while the unit cell100A before bonding is pressed by the manufacturing device200. More specifically, during implementation of the heating step, the second member214presses the first separator40using the force of the elastic body212and the first member213presses the first separator40. During implementation of the heating step, the third member232presses the second separator50.

As shown inFIG.8, in the step of bonding the separators40and50in a pair and the sealing part25to each other in step S30, the separators40and50in a pair are heated entirely to be thermally expanded. Namely, the separators40and50in a pair extend in an in-plane direction to move outward relative to the sealing part25indicated by arrow directions. When the separators40and50in a pair and the sealing part25are increased in temperature to be placed at a predetermined temperature or more, the separators40and50in a pair and the sealing part25are bonded to each other. Namely, as the separators40and50in a pair are increased in temperature to be thermally expanded, the separators40and50in a pair move outward relative to the sealing part25. Then, as the temperatures of the separators40and50in a pair and the sealing part25are increased further, the separators40and50in a pair and the sealing part25are bonded to each other.

As shown inFIG.6, after implementation of step S30, the membrane electrode assembly with the bonded sealing part is warped in the gap in step S40. More specifically, the separator-bonded stack100B is cooled to reduce the temperature of the separator-bonded stack100B. This temperature reduction causes thermal shrinkage of the separators40and50in a pair, thereby moving the sealing part25inward as shown inFIG.9while the separators40and50in a pair are bonded to the sealing part25. As a result, the membrane electrode assembly10with the bonded sealing part25is warped in the gap70. The thermal shrinkage of the separators40and50in a pair reduces the size of the sealing part25bonded to the separators40and50in a pair compared to the size of the sealing part25in the unit cell100A before bonding. This also reduces the size of the gap70compared to a size thereof immediately after implementation of step S30. By contrast, the first gas diffusion layer15, the second gas diffusion layer17, and the membrane electrode assembly10are changed in size to lesser degrees than the separators40and50in a pair and the sealing part25for the low coefficients of linear expansion of the first gas diffusion layer15, the second gas diffusion layer17, and the membrane electrode assembly10. In this embodiment, the first gas diffusion layer15, the second gas diffusion layer17, and the membrane electrode assembly10show little changes in size in step S30or in step S40. As a result, the warped part12is formed in the gap70in response to change in the shape of the sealing part25.

The separators40and50in a pair are cooled, for example, by cooling the separator-bonded stack100B in normal humidity to a temperature of equal to or less than 100° C., for example, to about 25° C. In step S40, the separator-bonded stack100B may be detached from the manufacturing device200and may be cooled by natural cooling. If the manufacturing device200includes a cooling mechanism, the separator-bonded stack100B may be cooled by stopping the operations of the heating parts218and238and operating the cooling mechanism. The cooling mechanism may be realized by providing the first heater unit210or the second heater unit230with a pipe for the flow of cooling water.

According to the foregoing embodiment, the warped part12is formed in the gap70by taking advantage of a difference in coefficient of linear expansion between the separators40and50in a pair and the electrolyte membrane13. This eliminates a need for drying the membrane electrode assembly10in advance for warping the membrane electrode assembly10to avoid complication of control of the process of manufacturing the unit cell100, thereby preventing reduction in the productivity of the unit cell100. According to the foregoing embodiment, the separators40and50in a pair are heated entirely to allow the separators40and50in a pair to be thermally expanded further. This allows the membrane electrode assembly10to be warped more largely in the cooling step. According to the foregoing embodiment, in the heating step, the first area FA of the first separator40is hot-pressed by the first member213and the second area SA of the first separator40is hot-pressed by the second member214. Namely, the first area FA and the second area SA can be hot-pressed in ways responsive to the first area FA and the second area SA. Additionally, as the first member213and the second member214are separate from each other, the manufacturing device200is made available as a device for hot-pressing using only the first member213by removing the second member214from the manufacturing device200. According to the foregoing embodiment, the second member214presses the first separator400using the elastic body212to allow more efficient transfer of heat from the second member214to the first separator40.

B. Other Embodiments

B-1. First Other Embodiment

According to the foregoing first embodiment, the separators40and50in a pair are heated entirely in step S30. However, this is not the only configuration. What is required in step S30is to heat the second area SA in addition to the first area FA, and the second area SA may be an area of the separators40and50in a pair overlapping with at least a part of an area in the stack20A inward from the sealing part25in a plan view. Even in this configuration, heating the second area SA in addition to the first area FA of the first separator40in step S30still makes it possible to cause thermal expansion.

B-2. Second Other Embodiment

While the first member213and the second member214are separate from each other (FIG.4) according to the foregoing embodiment, this is not the only configuration and the first member213and the second member214may be integrated with each other. While the second member214is biased by the elastic body212according to the foregoing embodiment, the elastic body212is omissible. The elastic body212may be provided on the side of the third member232. More specifically, the third member232may be divided into a first area portion facing the first area FA and a second area portion facing the second area SA. Then, an elastic body for biasing the second area portion toward the second separator50may be provided.

This disclosure is not limited to the foregoing embodiments but is feasible in various configurations within a range not deviating from the substance of this disclosure. For example, technical features in the embodiments corresponding to those in each of the aspects described in SUMMARY may be replaced or combined, where appropriate, with the intention of solving some or all of the aforementioned problems or achieving some or all of the aforementioned effects. Unless being described as absolute necessities in this specification, these technical features may be deleted, where appropriate. The present disclosure may be implemented by aspects described below.

(1) According to one aspect of this disclosure, a manufacturing method for a fuel cell is provided. The manufacturing method for the fuel cell includes the steps of: (a) preparing a stack and separators in a pair arranged in such a manner as to hold the stack therebetween, the stack including a membrane electrode assembly having a first surface and a second surface on the opposite side of the first surface, a frame-like sealing part bonded to an outer edge of the first surface, a first gas diffusion layer having a smaller outer shape than the membrane electrode assembly in a plan view and arranged at the first surface across the sealing part and a gap, and a second gas diffusion layer arranged at the second surface; (b) forming a separator-bonded stack by heating the separators in a pair to thermally expand the separators in a pair and move the separators in a pair outward relative to the sealing part, and then bonding the separators in a pair and the sealing part to each other; and (c) warping the membrane electrode assembly with the bonded sealing part in the gap by reducing the temperature of the separator-bonded stack to cause thermal shrinkage of the separators in a pair, thereby moving the sealing part with the bonded separators in a pair inward, the step (c) being performed after the step (b).

This aspect eliminates a need for drying the membrane electrode assembly in advance for warping the membrane electrode assembly to avoid complication of control of the process of manufacturing the fuel cell. As a result, reduction in the productivity of the fuel cell is prevented.

(2) According to the foregoing aspect, the step (b) may include a step of causing thermal expansion of the separators in a pair by heating a first area of each of the separators in a pair overlapping the sealing part in a plan view and a second area of each of the separators in a pair overlapping at least a part of an area in the stack inward from the sealing part in a plan view.

This aspect achieves thermal expansion of the separators in a pair through heating of the first area and the second area.

(3) According to the foregoing aspect, in the step of causing the thermal expansion, the separators in a pair may be heated entirely.

According to this aspect, heating the separators in a pair entirely allows the separators in a pair to be thermally expanded further. This allows the membrane electrode assembly to be warped more largely in the step (c).

(4) According to the foregoing aspect, in the step (b), the separators in a pair may be heated using a manufacturing device, the manufacturing device may include a first manufacturing device for heating a first separator forming the separators in a pair and arranged on the first surface side, the first manufacturing device may include a first member facing the first area of the first separator and used for heating the first area, and a second member separate from the first member and used for heating the second area of the first separator, and in the step (b), the first area of the first separator may be heated by the first member and the second area of the first separator may be heated by the second member.

This aspect allows heating of the first separator using the first member and the second member.

(5) According to the foregoing aspect, the manufacturing device may include an elastic body for pressing the second member toward the first separator, and the step (b) may be performed while the second member presses the first separator using the force of the elastic body.

According to this aspect, causing the second member to press the first separator using the force of the elastic body allows heat to be transferred more efficiently from the second member to the first separator.

This disclosure is feasible in various aspects such as a manufacturing device for a fuel cell, a fuel cell, a fuel cell device with a fuel cell, and a manufacturing method for a fuel cell device, for example, in addition to the manufacturing method for the fuel cell described above.