KR102720163B1 - Heat treatment stack for fuel cells and manufacturing method thereof - Google Patents

Abstract

The purpose of the heat treatment stack for a fuel cell and the manufacturing method thereof according to an embodiment of the present invention is to perform heat treatment in a new lamination manner on a 7-layer membrane electrode assembly, thereby improving dimensional changes and warping of the product, and enhancing durability and appearance.

Description

Heat treatment stack for fuel cells and manufacturing method thereof {Heat treatment stack for fuel cells and manufacturing method thereof}

The present invention relates to a heat treatment stack for a fuel cell and a manufacturing method thereof for heat treating a 7-layer membrane electrode assembly to improve the quality of the fuel cell stack.

A fuel cell is a device that produces electrical energy through an electrochemical reaction using fuel such as hydrogen and air such as oxygen. The structure consisting of a membrane electrode assembly (MEA) that joins the anode, cathode, and electrolyte where the electrochemical reaction occurs, and a separator for separating and inducing the flow of working fluids is called a fuel cell unit cell, which is the basic energy production unit. A fuel cell stack is made by stacking multiple fuel cell unit cells to obtain the required voltage.

When assembling a fuel cell stack using this unit cell configuration, the combination of the membrane electrode assembly and the gas diffusion layer, which are the main components, is located at the innermost. The membrane electrode assembly has a catalyst electrode layer, i.e., a cathode and an anode, on both sides of a polymer electrolyte membrane to which a catalyst is applied so that hydrogen and oxygen can react, and a gas diffusion layer, a gasket, etc. are laminated on the outer part where the cathode and the anode are located. A separator is located on the outside of the gas diffusion layer in which a reaction gas (hydrogen as a fuel and oxygen or air as an oxidizer) is supplied and a flow field through which cooling water passes is formed.

The separator serves to induce the flow of reaction gases, such as oxygen and fuel gas (hydrogen), and supply them to the membrane electrode assembly (MEA) through the gas diffusion layer (GDL), thereby enabling electricity to be generated through a reaction in the membrane electrode assembly. In order to diffuse the reaction gases through the gas diffusion layer (GDL), the separator includes a porous body having pores through which the gases diffuse, thereby forming a path through which the reaction gases flow.

With this configuration as a unit cell, multiple unit cells are stacked, and then a current collector and an insulating plate are combined on the outermost side, and an end plate to support the stacked cells is connected. By repeatedly stacking and connecting the cells between the end plates, a fuel cell stack is formed.

Meanwhile, Korean Patent Publication No. 10-2012-0063574, "Method for Manufacturing Membrane Electrode Assembly for Polymer Electrolyte Membrane Fuel Cell" is published. When producing a fuel cell stack, a 7-layer membrane electrode assembly structure in which a sub-gasket and a gas diffusion layer are bonded is manufactured, and then this is put into an automated process to be assembled with a separator, end plate, etc., thereby enabling mass production of the stack. That is, a 3-layer membrane electrode assembly in which a catalyst electrode layer is fixed to both sides of a polymer electrolyte membrane is manufactured, and then a sub-gasket is bonded to both sides of the electrolyte membrane so as to expose the active area of the membrane electrode assembly (i.e., the catalyst electrode layer area), thereby forming a 5-layer membrane electrode assembly structure.

After the 5-layer membrane electrode assembly is manufactured as described above, a gas diffusion layer is bonded to each of the catalyst electrode layers on both sides of the reaction area of the membrane electrode assembly exposed through the opening of the sub-gasket, using a hot pressing method, to create a 7-layer membrane electrode assembly structure, which is then put into a stack assembly process using an automatic stacking method such as vacuum adsorption to assemble the stack.

At this time, heat treatment is performed for the purpose of improving durability and appearance in the fuel cell process. In the case of heat treatment, simplifying and performing it in the final stage have an excellent effect on improving product quality and appearance. In the past, when heat treatment was performed on a 7-layer membrane electrode assembly in the final stage of the process, lines occurred according to the shape of the gas diffusion layer and the sub-gasket folding phenomenon occurred, making it difficult to apply the process. Therefore, in most fuel cell processes, heat treatment was often performed on a 5-layer membrane electrode assembly in the intermediate stage. In addition, as time passed in the final product stage, warping occurred, resulting in poor quality and appearance.

In particular, in the case of the existing plate method, since it receives heat directly, it can affect the membrane electrode assembly (MEA) and cause line formation in the gas diffusion layer (GDL), which causes issues in the process quality. In this way, the existing process causes the product to warp due to the influence of temperature and humidity when the product is manufactured, which causes issues in the appearance and quality, and development is needed to improve this.

Korean Patent Publication No. 10-2012-0063574 "Method for Manufacturing Membrane Electrode Assembly for Polymer Electrolyte Membrane Fuel Cell"

The present invention has been made to solve the above-described problems, and aims to improve the dimensional change and the wrinkling phenomenon of the product by performing heat treatment in a new lamination manner on a 7-layer membrane electrode assembly, and to improve the durability and appearance. It is not limited to the technical problems described above, and other technical problems may be derived from the following description.

In order to achieve the above object, the present invention relates to a fuel cell stack comprising a plurality of unit cells between end plates at both ends, wherein the unit cells include: a 3-layer membrane electrode assembly having a catalyst electrode layer attached to the upper and lower surfaces of an electrolyte membrane; films arranged on the upper and lower surfaces of the 3-layer membrane electrode assembly; and plates arranged on the upper and lower surfaces of the films; and wherein the unit cells are manufactured by subjecting the outer surface to a vacuum heat treatment in a 7-layer membrane electrode assembly state in which the 3-layer membrane electrode assembly, the film, and the plates are laminated.

In addition, the film is characterized by being made of a fluororesin series.

In addition, the plate is characterized in that it is made of acrylic material and is formed with a thickness of 3 to 4 mm.

In addition, the vacuum heat treatment is characterized in that it is performed under conditions of a temperature of 40 to 50 degrees and a pressure of 9 to 11 kgf/mm.

In addition, the membrane electrode assembly and the film are temporarily bonded by a belt roll, thereby removing a large amount of air bubbles generated on the exterior.

In addition, the present invention for achieving the above object includes a 3-layer forming step (S100) in which a catalyst electrode layer is attached to the upper and lower surfaces of an electrolyte membrane; a 5-layer forming step (S200) in which films are arranged on the upper and lower surfaces of a 3-layer membrane electrode assembly and provisionally bonded to form a 5-layer membrane electrode assembly; a 7-layer forming step (S300) in which plates are arranged on the upper and lower surfaces of the provisionally bonded 5-layer membrane electrode assembly and laminated to form a 7-layer membrane electrode assembly; and a heat treatment step (S400) in which the laminated 7-layer membrane electrode assembly is placed on a heat treatment plate and subjected to a vacuum heat treatment.

In addition, the heat treatment step (S400) is characterized in that it is performed under conditions of a temperature of 40 to 50 degrees and a pressure of 9 to 11 kgf/mm.

In addition, the 5-layer forming step (S200) is characterized in that an opening is formed in the center of the film, and the 7-layer forming step (S300) is characterized in that the plate is bonded to both sides of the 5-layer membrane electrode assembly through the opening of the film while the 3-layer membrane electrode assembly and the film are temporarily bonded.

In addition, it is characterized by further including a final product step (S500) in which a separator is arranged on both sides of the above-mentioned vacuum heat-treated 7-layer membrane electrode assembly to form a unit cell, and a plurality of unit cells are arranged between two end plates to manufacture a final product.

However, the effects obtainable from the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

According to the fuel cell heat treatment stack and its manufacturing method according to the embodiment of the present invention having the above configuration, the following advantages are provided.

By performing heat treatment on the 7-layers arranged in a new lamination method, the product's dimensional changes and warping phenomenon can be improved, and its durability and appearance can be improved.

In addition, it is possible to shorten the process time, secure the yield, and secure the quality of the product at the same time, thereby improving the quality by overcoming deformation and warping during long-term storage of the product.

In addition, the process conditions are the same as those of the existing high-temperature heat treatment process, and these changes can effectively produce results in dimensional deformation and quality improvement by reducing the appearance of bubbles and strain in a vacuum atmosphere.

In addition, it can greatly contribute to cost reduction by enabling the reuse of existing equipment, and it can greatly improve process efficiency by simplifying the production process and securing production yield, thereby increasing product quality and market competitiveness.

In addition, the low-temperature heat treatment process shows an effect that is 2 to 3 times more effective than the high-temperature heat treatment process and the existing process efficiency, and through a specific film lamination method, electrode damage can be minimized and product appearance and deformation can be prevented.

In addition, since there is no additional process after heat treatment of the 7-layer, the defect rate can be drastically reduced, and the heat treatment time can be reduced by 2.4 times compared to the existing one, so the process yield can be increased.

Figure 1 is a layout diagram of a 7-layer configuration of a conventional heat treatment stack for a fuel cell during heat treatment.
Figure 2 is a 7-layer configuration diagram of a heat treatment stack for a fuel cell according to an embodiment of the present invention and a layout diagram during heat treatment.
Figure 3 is a configuration diagram of a heat treatment stack for a fuel cell according to an embodiment of the present invention.
Figure 4 is a process flow diagram of a method for manufacturing a heat treatment stack for a fuel cell according to an embodiment of the present invention.
Figure 5 is a drawing showing a unit cell produced using a conventional process sequence.
FIG. 6 is a drawing showing a unit cell produced in the process sequence of a method for manufacturing a heat treatment stack for a fuel cell according to an embodiment of the present invention.

Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that a person having ordinary skill in the art to which the present invention pertains can easily implement the present invention. However, since the description of the present invention is merely an embodiment for structural and functional explanation, the scope of the rights of the present invention should not be construed as being limited by the embodiments described in the text. That is, since the embodiments can be variously modified and can have various forms, the scope of the rights of the present invention should be understood to include equivalents that can realize the technical idea. In addition, the purpose or effect presented in the present invention does not mean that a specific embodiment must include all of them or only such effects, and therefore the scope of the rights of the present invention should not be understood as being limited thereby.

The meanings of terms described in the present invention should be understood as follows.

The terms "first", "second", etc. are intended to distinguish one component from another, and the scope of the right should not be limited by these terms. For example, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. When a component is referred to as being "connected" to another component, it should be understood that it may be directly connected to the other component, but there may also be another component in between. On the other hand, when a component is referred to as being "directly connected" to another component, it should be understood that there is no other component in between. Meanwhile, other expressions that describe the relationship between components, such as "between" and "directly between" or "adjacent to" and "directly adjacent to", should be interpreted in the same way.

A singular expression should be understood to include the plural expression unless the context clearly indicates otherwise, and the terms "comprises" or "have" should be understood to specify the presence of a stated feature, number, step, operation, component, part, or combination thereof, but not to exclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

All terms used herein, unless otherwise defined, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the contextual meaning of the relevant art, and shall not be interpreted as having an ideal or overly formal meaning unless explicitly defined in the present invention.

In general, a fuel cell is composed of a membrane electrode assembly (MEA) in which a solid polymer electrolyte membrane through which hydrogen ions move is centered, a catalyst electrode layer on both sides of the membrane where an electrochemical reaction occurs, a gas diffusion layer (GDL) that evenly distributes reaction gases and transfers the generated electrical energy, a gasket and a fastening mechanism to maintain the airtightness and appropriate fastening pressure of the reaction gases and cooling water, and a bipolar plate that moves the reaction gases and cooling water.

When assembling a fuel cell stack using this unit cell configuration, the combination of the membrane electrode assembly and the gas diffusion layer, which are the main components, is located at the innermost part. The membrane electrode assembly has a catalyst electrode layer, i.e., a cathode and an anode, on which a catalyst is applied to both sides of the polymer electrolyte membrane so that hydrogen and oxygen can react, and a gas diffusion layer, a sub-gasket, etc. are laminated on the outer part where the cathode and anode are located.

In the process of manufacturing a fuel cell stack, heat treatment is generally performed for the purpose of improving durability and appearance. At this time, in the case of heat treatment, simplifying and performing it in the final stage has a great effect on improving product quality and appearance. In the past, when heat treatment was performed on a 7-layer membrane electrode assembly, lines were generated according to the shape of the gas diffusion layer (GDL) and the sub-gasket was folded, making it difficult to apply the process. Therefore, heat treatment was performed on a 5-layer membrane electrode assembly in most fuel cell processes.

However, if heat treatment is performed on the 5-layer membrane electrode assembly, durability and a clean appearance can be manufactured, but the product size change and crying phenomenon due to the heat can cause defects in the later process. In particular, in the case of the existing process, the heat treatment is performed by arranging it on a plate or by laminating various films, but if the 7-layer is heat treated under the same conditions as the existing process in the final process, lines are generated in the shape of the gas diffusion layer (GDL), causing the appearance and deformation of the membrane electrode assembly.

The present invention develops conditions using a new lamination method to enable heat treatment in a 7-layer membrane electrode assembly. In addition, the present invention improves the phenomenon of crying, shortens the process time, and ensures yield when heat treatment is performed in a 7-layer membrane electrode assembly, in addition to the characteristics of heat treatment in a 5-layer membrane electrode assembly. In addition, by securing heat treatment process conditions in a 7-layer membrane electrode assembly using a new lamination method, the yield and quality of the product can be secured, and it is excellent in improving quality by overcoming deformation and warping phenomena even in long-term storage of the product.

FIG. 1 is a configuration diagram of a 7-layer membrane electrode assembly of a conventional fuel cell stack and a layout diagram during heat treatment, FIG. 2 is a configuration diagram of a 7-layer membrane electrode assembly of a fuel cell stack according to an embodiment of the present invention and a layout diagram during heat treatment, and FIG. 3 is a configuration diagram of a fuel cell stack according to an embodiment of the present invention. The fuel cell stack of the present invention will be described with reference to FIGS. 1 to 3. The fuel cell stack (10) of the present invention is composed of a plurality of unit cells (200) between end plates (100) at both ends.

The end plate (100) is a component used to support and combine stacked unit cells (200). In addition, the end plate (100) is attached to both ends of the stack to prevent gas leakage. In addition, the end plate (100) is an essential element that protects the secondary battery cell from external impact or internal expansion by wrapping it on both sides. At this time, the end plate (100) acts as a Maginot Line that protects the cell located at the innermost part of the secondary battery from external impact applied by collision, etc.

In addition, when the cell expands inside the secondary battery due to various factors, the end plate physically suppresses this and prevents damage from spreading to other modules. In addition, the end plate (100) is used in the final assembly of the process and may affect the quality of the final product. This end plate (100) may be made of aluminum material parts mounted on both ends of a pouch-type and square-type secondary battery module, and one module requires two end plates as a pair.

The unit cell (200) has a structure in which a separator (240), a gas diffusion layer (GDL), and a membrane electrode assembly (MEA) are laminated, and has a sub-gasket interposed between a 3-layer membrane electrode assembly (210) and an edge portion between the two separators (240), and the membrane electrode assembly and the sub-gasket are connected by an adhesive. That is, the unit cell has a structure in which the separator/gas diffusion layer/sub-gasket/membrane electrode assembly/sub-gasket/gas diffusion layer/separator are arranged and laminated in the order of separator/gas diffusion layer/sub-gasket/membrane electrode assembly/sub-gasket/gas diffusion layer/separator.

At this time, the membrane electrode assembly is a core component of the fuel cell stack, and is classified into a 3-layer membrane electrode assembly, a 5-layer membrane electrode assembly, and a 7-layer membrane electrode assembly depending on the assembly configuration. The 3-layer membrane electrode assembly is composed of a polymer electrolyte membrane and catalyst electrode layers on both sides (anode and cathode), and hydrogen injected into the anode, which is the oxidation electrode, reacts with the catalyst and is decomposed into protons and electrons. The decomposed protons pass through the electrolyte membrane to the cathode, which is the reduction electrode, and combine with oxygen, and the electrons that do not pass through the electrolyte membrane are used as electrical energy.

That is, a 3-layer membrane electrode assembly is called a 3-layer membrane electrode assembly in which a fuel electrode and an air electrode, which contain a catalyst on both sides, are respectively bonded to a polymer electrolyte membrane in the center. And a 5-layer membrane electrode assembly includes a sub-gasket having an opening with an area slightly smaller than the area of the electrode in the boundary area on both sides of the 3-layer membrane electrode assembly. A 7-layer membrane electrode assembly means that a gas diffusion layer is further laminated on the outer part of the electrode containing the catalyst.

The fuel cell stack (10) of the present invention has a new lamination method so as to perform heat treatment on a 7-layer membrane electrode assembly. Conventionally, as shown in FIG. 1, heat treatment is performed by arranging plates or by having a structure in which various films are laminated. At this time, conventionally, X-substrate/film/film/membrane electrode assembly/film/film/sponge/acrylic plates are laminated on a heat treatment plate to perform heat treatment. When heat treatment is performed on a 7-layer membrane electrode assembly in this way, lines are generated in the shape of a gas diffusion layer, which causes a change in the appearance and deformation of the membrane electrode assembly.

In order to solve this problem, as shown in FIG. 2, the present invention laminates a plate (230)/film (220)/3-layer membrane electrode assembly (210)/film (220)/plate (230) on a heat treatment plate (20) so that it can be heat treated using a low-temperature heat treatment process. At this time, the 3-layer membrane electrode assembly (210), film (220), and plate (230) are heat treated in a laminated state, and a separator (240) is installed on both sides to form one unit cell.

The 3-layer membrane electrode assembly (210) is configured such that a catalyst layer (212) is attached to the upper and lower surfaces of a polymer electrolyte membrane (211). At this time, the polymer electrolyte membrane is mainly a perfluorosulfonate ionomer membrane such as Nafion (trade name manufactured by DuPont), Flemion (trade name manufactured by Asahi Glass), Asiplex (trade name manufactured by Asahi Chemical), and Dow XUS (trade name manufactured by Dow Chemical), but has the disadvantage of being expensive.

To solve this problem, research is actively being conducted on hydrocarbon polymers such as polyetheretherketone, polysulfone, and polyimide, which are relatively inexpensive and have a variety of commercial applications. The above polymers are manufactured into ion-conducting polymers through a sulfonation reaction and then cast into an electrolyte membrane, which is then applied as a fuel cell electrolyte membrane.

The 3-layer membrane electrode assembly (210) is also called a CCM (Catalyst coated membrane), and an integrated membrane electrode assembly can be manufactured by using the Decal method or the Roll to Roll method. In the case of the Decal method, catalyst ink is poured onto the transfer film of the coater in the direction of blade movement, the catalyst ink is coated on the transfer film at a constant speed, and then the cathode and anode catalysts coated on the transfer film are hot pressed with the membrane in between, and the transfer film is removed to manufacture the assembly. In the case of the Roll to Roll method, the catalyst is hot pressed to be transferred to the transfer film coated with the catalyst, the transfer film is removed after the hot press, and the membrane onto which the catalyst is transferred is sheared to manufacture the assembly.

The film (220) is arranged to be placed on the upper and lower surfaces of the 3-layer membrane electrode assembly (210). At this time, the film (220) is preferably made of a fluororesin series, and may include PTFE, PFA, FEP, ETFE, PVDF, PCTFE, ECTFE, etc. Among them, it can be formed as a PTFE film, and has high heat resistance among resins with a continuous use temperature of about 260 degrees. In addition, PTFE has high chemical resistance, so it does not deteriorate even when exposed to chemicals, and has high wear resistance, high electric resistance, and excellent insulation.

In this way, the film (220) can be combined with the 3-layer membrane electrode assembly (210) to form a 5-layer membrane electrode assembly. In addition, the film (220) can be connected to the 3-layer membrane electrode assembly (210) as a sub-gasket by an adhesive. In this way, the film (220) serves to block gases from mixing between the anode and the cathode.

In particular, the film (220) can remove a large amount of air bubbles generated on the exterior by being bonded to the 3-layer membrane electrode assembly (210) by a belt roll. In addition, the film (220) can prevent fatigue destruction of the polymer electrolyte membrane (211) by having a set thickness, and can prevent the electrolyte membrane from being damaged due to the fastening pressure. That is, the film (220) can prevent leakage of the supplied gas and prevent the porosity in the gas diffusion layer from being reduced due to excessive fastening pressure.

The plate (230) is arranged to be placed on the upper and lower surfaces of the film (220). The plate (230) is made of an acrylic material and can be formed to have a thickness of 3 to 4 mm. The plate (230) can be joined to both sides of a 5-layer membrane electrode assembly to form a 7-layer membrane electrode assembly. In addition, the plate (230) is positioned as a gas diffusion layer on the outer part of the membrane electrode assembly, that is, on the outer part where the cathode and the anode are located, and a separator (240) is positioned on the outer side of the plate (230) in which a flow field is formed to supply fuel and discharge water generated by the reaction.

The plate (230) is a core component of a hydrogen fuel cell, which provides a smooth supply of reaction gas and a passage for the reaction gas to travel from the flow field channel to the catalyst layer, and conducts heat generated by the electrochemical reaction to the separator (240) to remove the heat. In this way, in the state of a 7-layer membrane electrode assembly laminated with a 3-layer membrane electrode assembly (210), a film (220), and a plate (230), the outer surface is vacuum-heat-treated using a low-temperature heat treatment process, so that the process efficiency can be 2 to 3 times more effective than the existing high-temperature heat treatment process.

In detail, while a heat treatment process was performed at a high temperature of 100 degrees or higher in the past, the present invention can improve process efficiency and reduce dimensional deformation and defects of products by performing a low-temperature heat treatment process of 40 to 50 degrees. In this way, the existing process method can affect the electrode because it directly receives heat, and can cause line formation of the gas diffusion layer, thereby causing issues in the process quality. On the other hand, the process method of the present invention can minimize electrode damage and prevent appearance and deformation of the product through a specific film lamination method.

The separator (240) is provided to make an electrical connection between the unit cells (200) and the unit cells (200). The separator (240) is a conductive plate that separates each cell in the fuel cell stack, and functions as a fuel electrode plate in one cell and as an air electrode plate in the other cell among two adjacent cells. In addition to its role of blocking fuel gas and air, the separator (240) also serves to secure a flow path for fuel gas and air and transmit current to an external circuit, and therefore requires high electrical conductivity, corrosion resistance, thermal conductivity, and low gas permeability.

The separator (240) is mainly manufactured from a resin-impregnated graphite plate, a carbon composite plate, a metal plate, etc., and has a flow path formed to help the flow of fluid. In addition, the separator (240) also plays a role in distributing the heat generated from the cell to the entire fuel cell stack, and excessive heat generated is recovered or recycled through air-cooling or water-cooling heat exchange. The types of separators developed so far can be classified into resin-impregnated graphite plates, carbon composite separator plates, and metal separator plates. Among these, the resin-impregnated graphite plate is a fuel cell separator that forms a gas flow path by impregnating a graphite plate with resin and mechanically processing it.

The separator (240) is involved in the movement of electrons inside the fuel cell, so the most important characteristic is the electrical conductivity penetrating the plate (230). In addition, as a gas diffusion layer, there must be a path for distributing gas, and it must be impermeable to reactive gases or ions and chemically stable. In addition, considering the characteristics of the automobile and portable product markets, which are expected to be the main application fields of polymer electrolyte fuel cells, it must be light and capable of mass production.

FIG. 4 is a process flow diagram of a method for manufacturing a heat treatment stack for a fuel cell according to an embodiment of the present invention. The process flow diagram of a method for manufacturing a heat treatment stack for a fuel cell will be described with reference to FIG. 4.

The 3-layer formation step (S100) is prepared by attaching a catalyst layer (212) to the upper and lower surfaces of the electrolyte membrane (211).

In the 5-layer formation step (S200), a fluororesin series film (220) is placed on the upper and lower surfaces of a 3-layer membrane electrode assembly (210) and is temporarily bonded to a 5-layer membrane electrode assembly by a belt roll. At this time, an opening (221) is formed in the center of the film (220).

In the 7-layer formation step (S300), an acrylic plate (230) is placed on the upper and lower surfaces of the 5-layer membrane electrode assembly that has been provisionally bonded, and the 7-layer membrane electrode assembly is laminated. At this time, in the 7-layer formation step (S300), the plate (230) is bonded to both surfaces of the 5-layer membrane electrode assembly through the opening (221) of the film (220) while the 3-layer membrane electrode assembly (210) and the film (220) are provisionally bonded.

The heat treatment step (S400) is performed under vacuum heat treatment while the 7-layer membrane electrode assembly is placed on the heat treatment plate (20). At this time, the heat treatment step (S400) is performed under the conditions of a temperature of 40 to 50 degrees and a pressure of 9 to 11 kgf/mm.

In the final product stage (S500), a separator (240) is placed on both sides of a vacuum-heat-treated 7-layer membrane electrode assembly to form a unit cell, and a plurality of unit cells (200) are arranged between two end plates (100) to manufacture a final product.

FIG. 5 is a drawing showing a unit cell produced in a conventional process sequence, and FIG. 6 is a drawing showing a unit cell produced in a process sequence of a method for manufacturing a heat treatment stack for a fuel cell according to an embodiment of the present invention.

As shown in Fig. 5, the results of heat treatment after forming a 7-layer membrane electrode assembly are shown, and it can be confirmed that lines are generated in the shape of a gas diffusion layer. In contrast, as shown in Fig. 6, the results of heat treatment on a 7-layer membrane electrode assembly of a new lamination method are shown, and it can be confirmed that lines are not generated without a crying phenomenon.

In this way, when heat treatment is performed on a 7-layer membrane electrode assembly, it is possible to improve the heat treatment characteristics of a 5-layer membrane electrode assembly, as well as the crying phenomenon, shorten the process time, and secure the yield. The present invention secures the heat treatment process conditions of a 7-layer membrane electrode assembly, thereby securing the yield and quality of the product, and also overcomes deformation and warping phenomena during long-term storage of the product, thereby improving the quality excellently.

In addition, it is the same as the process conditions that show the same characteristics as the existing high-temperature heat treatment process, and due to this change, it can produce effective results in dimensional deformation and quality improvement by reducing the appearance of bubbles and deformation rate in a vacuum atmosphere. In addition, the process time is reduced, so the yield is increased, and it prevents product deformation over time and has a great effect on quality improvement.

When heat treatment is performed on a conventional 5-layer membrane electrode assembly, product distortion occurs, resulting in dimensional deformation and defects in the subsequent process. However, since there is no post-heat treatment process for a 7-layer membrane electrode assembly, the defect rate can be drastically reduced, and the heat treatment time can be reduced by 2.4 times compared to the previous process, thereby increasing the process yield.

In the existing process, the product warps due to temperature and humidity when manufacturing the product, causing issues with its appearance and quality. However, when the process of the present invention is applied, the product does not warp due to temperature and humidity even when stored for a long period of time, which can lead to significant improvements in storage and quality.

The detailed description of the preferred embodiments of the present invention disclosed above has been provided to enable those skilled in the art to implement and practice the present invention. While the above has been described with reference to preferred embodiments of the present invention, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of the present invention. For example, those skilled in the art can utilize each of the configurations described in the above-described embodiments in a manner that combines them. Accordingly, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The present invention may be embodied in other specific forms without departing from the spirit and essential characteristics of the present invention. Accordingly, the above detailed description should not be construed in all aspects as restrictive but rather as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all changes coming within the equivalent scope of the present invention are intended to be embraced therein. The present invention is not intended to be limited to the embodiments set forth herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. In addition, claims that do not have an explicit citation relationship in the claims may be combined to constitute an embodiment or may be included as a new claim by post-application amendment.

10: Stack for fuel cell
20 : Heat treatment plate
100 : Endplate
200 : Unit cell
210: 3-layer membrane electrode assembly
211 : Electrolyte membrane
212 : Catalyst layer
220 : Film
221 : Aperture
230 : Plate
240 : Separator
S100: 3-layer formation stage
S200: 5-layer formation stage
S300: 7-layer formation stage
S400: Heat treatment stage
S500: Final product stage

Claims (9)

In a fuel cell stack comprising a plurality of unit cells between end plates at both ends,
The above unit cell is,
A three-layer membrane electrode assembly having a catalyst electrode layer attached to the upper and lower surfaces of an electrolyte membrane;
A film disposed on the upper and lower surfaces of the above 3-layer membrane electrode assembly; and
A plate disposed on the upper and lower surfaces of the above film;
The above unit cell is manufactured by vacuum heat-treating the outer surface in a 7-layer membrane electrode assembly state in which the above 3-layer membrane electrode assembly, film, and plate are laminated,

The above vacuum heat treatment is,
A heat treatment stack for a fuel cell, characterized in that it is performed under conditions of a temperature of 40 to 50 degrees and a pressure of 9 to 11 kgf/mm.
In the first paragraph,
The above film,
A heat treatment stack for a fuel cell characterized by being composed of a fluororesin series. In the first paragraph,
The above plate,
A heat treatment stack for a fuel cell, characterized in that it is made of acrylic material and formed to a thickness of 3 to 4 mm. delete In the first paragraph,
A heat treatment stack for a fuel cell, characterized in that the three-layer membrane electrode assembly and the film are bonded by a belt roll to remove a large amount of air bubbles generated on the exterior. 3-layer formation step (S100) in which a catalyst electrode layer is attached to the upper and lower surfaces of the electrolyte membrane;
A 5-layer forming step (S200) in which films are placed on the upper and lower surfaces of the above 3-layer membrane electrode assembly and bonded to form a 5-layer membrane electrode assembly;
A 7-layer forming step (S300) in which plates are placed on the upper and lower surfaces of the above-mentioned 5-layer membrane electrode assembly and laminated into a 7-layer membrane electrode assembly; and
A heat treatment step (S400) in which the laminated 7-layer membrane electrode assembly is placed on a heat treatment plate and subjected to vacuum heat treatment;

The above heat treatment step (S400) is
A method for manufacturing a heat treatment stack for a fuel cell, characterized in that it is performed under conditions of a temperature of 40 to 50 degrees and a pressure of 9 to 11 kg _f /mm.
delete In Article 6,
The above 5-layer formation step (S200) is
An opening is formed and provided in the center of the above film,
The above 7-layer formation step (S300) is
A method for manufacturing a heat treatment stack for a fuel cell, characterized in that the plate is bonded to both sides of the 5-layer membrane electrode assembly through the opening of the film while the 3-layer membrane electrode assembly and the film are bonded together. In Article 6,
A method for manufacturing a heat treatment stack for a fuel cell, characterized in that it further includes a final product step (S500) in which a separator is arranged on both sides of the above-mentioned vacuum heat-treated 7-layer membrane electrode assembly to form a unit cell, and a plurality of unit cells are arranged between two end plates to manufacture a final product.

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