KR20230149144A - Reinforced composite membrane for fuel cell, manufacturing method thereof and membrane-electrode assembly for fuel cell comprising the same - Google Patents

Abstract

The present invention is a reinforced composite membrane comprising a porous support and a hydrogen ion conductive polymer, wherein the reinforced composite membrane is impregnated with the hydrogen ion conductive polymer into the porous support, or the hydrogen ion conductive polymer is impregnated on at least one side of the porous support. The present invention relates to a reinforced composite membrane for a fuel cell, including an electrolyte layer containing the hydrogen ion conductive polymer or a crosslinking portion derived from a crosslinking agent, a method for manufacturing the same, and a membrane-electrode assembly including the same.

Description

Reinforced composite membrane for fuel cell, manufacturing method thereof and membrane-electrode assembly for fuel cell comprising the same}

The present invention relates to a reinforced composite membrane for fuel cells, a method of manufacturing the same, and a membrane-electrode assembly for fuel cells including the same.

Recently, due to the rapid spread of portable electronic devices and wireless communication devices, much interest and research is being conducted in the development of fuel cells as batteries as a portable power source, pollution-free fuel cells for automobiles, and fuel cells for power generation as a clean energy source.

Polymer Electrolyte Membrane Fuel Cell (PEMFC), which uses hydrogen as fuel, can operate in a wide temperature range, simplifying cooling devices and sealing parts, minimizing the use of humidifiers because it uses low-humidity hydrogen as fuel, and providing rapid heating. Due to its advantages such as driving, it is attracting attention as a power supply device for vehicles and home use. Additionally, it is a high-output fuel cell with a higher current density than other types of fuel cells. It operates in a wide range of temperatures, has a simple structure, and has fast start-up and response characteristics.

Recently, many efforts have been made to improve the long-term performance of electrolyte membranes, a key component of fuel cells. In order to be price competitive and improve performance at the same time, high ion conduction characteristics at low humidity are a very important factor.

Among various types of electrolyte membranes, perfluorinated electrolyte membranes have excellent mechanical strength and electrochemical properties, but the price of the membrane is very expensive due to the complex manufacturing process, and the low glass transition temperature due to the fluorinated structure acts as a disadvantage.

As an alternative to such perfluorinated electrolyte membranes, hydrocarbon polymers have been actively developed, and in the case of hydrocarbon polymer electrolyte membranes, securing appropriate mechanical strength at the level of perfluorinated electrolyte membranes is an important task.

In addition, the oxidation of the hydrocarbon polymer electrolyte membrane can be accelerated by hydrogen peroxide or hydroxy radicals generated during the operation of the polymer electrolyte fuel cell, and when a single membrane is used, the mechanical durability is greatly reduced, which causes the chemical damage of the polymer electrolyte membrane. , the fact that mechanical stability may be greatly reduced is pointed out as a serious problem. In order to realize high performance, long-term stability, high durability, and low cost, the electrolyte membrane requires high ionic conductivity, physical and chemical stability, high mechanical strength, and high number stability. To satisfy this, the introduction of a reinforced composite membrane can be an alternative.

On the one hand, in the process of commercializing reinforced composite membranes, there were various demands in the industrial field for technologies to improve various performances in addition to high durability. Examples include technology to control the gas permeability of the reinforced composite membrane, technology to improve the stability between the electrolyte and the support, or technology to facilitate impregnation of the electrolyte. In this respect, there are technologies that improve the performance of the reinforced composite membrane. The situation required research on methods.

The purpose of the present invention is to provide a crosslinking portion derived from a crosslinking agent to a polymer electrolyte or porous support containing a hydrogen ion conductive polymer, thereby maintaining the shape of the polymer contained in the polymer electrolyte even when chemical deterioration occurs due to operation of the fuel cell, thereby increasing durability. The aim is to provide a reinforced composite membrane for fuel cells that can maintain the performance of the fuel cell for a long period of time and improve its lifespan by improving and minimizing interfacial separation between the porous support and the polymer electrolyte.

Another object of the present invention is to provide a method for manufacturing the reinforced composite membrane.

Another object of the present invention is to provide a membrane-electrode assembly including the reinforced composite membrane.

Another object of the present invention is to provide a fuel cell including the membrane-electrode assembly.

One embodiment of the present invention is a reinforced composite membrane comprising a porous support and a hydrogen ion-conducting polymer, wherein the reinforced composite membrane is formed by impregnating the porous support with the hydrogen ion-conducting polymer, or on at least one side of the porous support. Provided is a reinforced composite membrane for a fuel cell, including an electrolyte layer containing a hydrogen ion conductive polymer, wherein the hydrogen ion conductive polymer or the porous support includes a crosslinking portion derived from a crosslinking agent.

The crosslinking portion included in the hydrogen ion conductive polymer or the porous support may be a hydroxy group (-OH), a carboxyl group (-COOH), an amine group (-NH ₂ ), a halogen, or a combination thereof. Here, the halogen may be -F, -Cl, -Br, or -I.

The crosslinking portion may be derived from at least one selected from the group consisting of dicarboxylic acid-based compounds, diamine-based compounds, glycol-based compounds, phenols substituted with halogens, benzoic acids substituted with halogens, and phenols substituted with carboxyl groups. .

The crosslinking portion may be introduced into the surface of the porous support.

The hydrogen ion conductive polymer may include a cation exchange group selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphoric acid group, an imide group, a sulfonimide group, a sulfonamide group, and a sulfonic acid fluoride group.

The porous support may be a stretched film or nonwoven web.

The thickness of the porous support may be 1 to 100 ㎛.

According to another embodiment of the present invention, (a) preparing a porous support into which a crosslinking portion is introduced by contacting the porous support with a crosslinking agent; and (b) impregnating the porous support with a hydrogen ion conductive polymer or forming an electrolyte layer containing a hydrogen ion conductive polymer on at least one surface of the porous support including the crosslinking portion. Reinforced composite for fuel cells comprising the step of: A method for manufacturing a membrane is provided.

In step (a), the porous support may be surface treated by plasma treatment, UV treatment, or ultrasonic treatment and then contacted with the crosslinking agent.

In step (a), the cross-linking agent may be spray-applied, spin-applied, or inkjet printed on the porous support in solution form to contact the porous support.

According to another embodiment of the present invention, (c) polymerizing at least one type of monomer with a cross-linking agent to produce a polymer into which a cross-linking moiety is introduced; (d) preparing a porous support or hydrogen ion conductive polymer from the polymer; and (e) impregnating a porous support with a hydrogen ion conductive polymer or forming an electrolyte layer containing a hydrogen ion conductive polymer on at least one surface of the porous support. .

In steps (a) and (c) of the method for manufacturing a reinforced composite membrane for fuel cells, the crosslinking portion is a hydroxy group (-OH), a carboxyl group (-COOH), an amine group (-NH ₂ ), halogen, or a combination thereof. You can. Here, the halogen may be -F, -Cl, -Br, or -I.

In step (a) of the method for manufacturing a reinforced composite membrane for a fuel cell, the crosslinking agent may be at least one selected from the group consisting of dicarboxylic acid-based compounds, diamine-based compounds, and glycol-based compounds.

In step (c) of the method for manufacturing a reinforced composite membrane for a fuel cell, the crosslinking agent may be at least one selected from the group consisting of phenol substituted with a halogen, benzoic acid substituted with a halogen, and phenol substituted with a carboxyl group.

Another embodiment of the present invention provides a membrane-electrode assembly including an anode electrode and a cathode electrode positioned opposite to each other, and the reinforced composite membrane for a fuel cell positioned between the anode electrode and the cathode electrode.

Another embodiment of the present invention provides a fuel cell including the membrane-electrode assembly.

According to the present invention, as a cross-linking portion derived from a cross-linking agent is provided to the polymer electrolyte or porous support contained in the reinforced composite membrane for fuel cells, the shape of the polymer contained in the polymer electrolyte is maintained even when chemical deterioration occurs due to fuel cell operation, thereby strengthening the polymer electrolyte. The durability of the composite membrane can be improved.

Accordingly, interfacial detachment between the porous support and the polymer electrolyte is minimized, thereby significantly improving the performance and lifespan of the fuel cell including the reinforced composite membrane.

Figure 1 is a schematic diagram schematically showing a reinforced composite membrane for a fuel cell according to an embodiment of the present invention.
Figure 2 is a cross-sectional view schematically showing a membrane-electrode assembly according to an embodiment of the present invention.
Figure 3 is a schematic diagram showing the overall configuration of a fuel cell according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

In the drawings, the thickness is enlarged to clearly express various layers and regions, and similar reference numerals are given to similar parts throughout the specification. When a part of a layer, membrane, region, plate, etc. is said to be “on” another part, this includes not only cases where it is “directly above” the other part, but also cases where there is another part in between. Conversely, when a part is said to be “right on top” of another part, it means that there is no other part in between.

As used herein, the term “nano” refers to nanoscale and includes sizes of 1 μm or less.

Hereinafter, a reinforced composite membrane for a fuel cell according to an embodiment will be described.

The present invention provides a cross-linking portion derived from a cross-linking agent to a polymer electrolyte or porous support containing a hydrogen ion conductive polymer, and improves durability by maintaining the shape of the polymer contained in the polymer electrolyte even when chemical deterioration occurs during operation of the fuel cell. , relates to a reinforced composite membrane for fuel cells that can maintain the performance of the fuel cell for a long period of time and improve its lifespan by minimizing interfacial separation between the porous support and the polymer electrolyte.

Figure 1 is a schematic diagram showing the schematic configuration of a reinforced composite membrane for a fuel cell according to an embodiment.

Referring to FIG. 1, the reinforced composite membrane 10 for a fuel cell according to one embodiment is a reinforced composite membrane including a porous support 5 and a hydrogen ion conductive polymer, and the reinforced composite membrane includes the hydrogen ion conductive polymer. Impregnated in the porous support 5, or comprising an electrolyte layer (1 and/or 3) containing the hydrogen ion conductive polymer on at least one side of the porous support 5, and comprising the hydrogen ion conductive polymer or the The porous support may include crosslinking portions derived from a crosslinking agent.

In general, a variety of polymer-type fluorine-based/partially fluorine-based/hydrocarbon-based electrolyte materials have been attempted to commercialize fuel cells for automobiles and home use, but ① mechanical/chemical durability ② high mechanical/chemical durability under fuel cell operating conditions (acid conditions, temperature, pressure, radical decomposition, etc.) PFSA pure membrane is currently the only material that satisfies the following requirements: ③ hydrogen and oxygen barrier properties ④ compatibility with electrodes containing fluorine-based binders and stable interface formation characteristics ⑤ electrochemical fuel cell lifespan characteristics.

However, unlike the household fuel cell field where reaction conditions are relatively close to steady state, when applied to the automotive fuel cell field where on/off cycles and temperature and humidity changes occur continuously, the above-mentioned excellent performance characteristics are obtained. Even in the PFSA pure film, as water is repeatedly evaporated and absorbed, delamination of the electrode and degradation due to hydrogen permeation occur, significantly reducing the fuel cell lifespan characteristics.

In contrast, the reinforced composite membrane for fuel cells according to the present invention is provided with a cross-linked portion derived from a cross-linking agent on the surface of the hydrogen ion-conducting polymer or porous support contained in the reinforced composite membrane, especially the porous support, so that the cross-linked portion is formed by, for example, hydrogen ions. By forming a bond (for example, an ionic bond or a hydrogen bond) with the cation exchanger of the conductive polymer membrane, it can include a cross-linked structure, for example, an ionic cross-linked structure or a hydrogen bond cross-linked structure. Thanks to these crosslinks, the shape of the polymer can be maintained even when chemical deterioration occurs during fuel cell operation, improving the durability of the reinforced composite membrane, and interfacial detachment between the porous support and the hydrogen ion conductive polymer or the polymer electrolyte membrane containing it is minimized. This can significantly improve the performance and lifespan of a fuel cell including the reinforced composite membrane.

The porous support 5 serves to improve dimensional stability by improving the mechanical strength of the reinforced composite membrane and suppressing volume expansion due to moisture. A general porous support used in the industry can be used, or a porous support for forming a porous support can be used. It can be manufactured by chemically curing nanofibers of a polymer precursor prepared by electrospinning a solution containing a polymer precursor. The porous support may be an expanded film or a nonwoven fibrous web.

The porous support (5) is insoluble in common organic solvents, so it not only exhibits excellent chemical resistance, but also facilitates the process of filling ion conductors in the pores of the porous support, and has hydrophobicity, so there is no risk of shape deformation due to moisture in a high humidity environment. It is preferable that it contains a hydrocarbon-based polymer. The hydrocarbon-based polymers include nylon, polyimide (PI), polybenzoxazole (PBO), polybenzimidazole (PBI), polyamideimide (PAI), and polyethyleneterephthalate. ), polyethylene (PE), polytetrafluoroethylene (PTFE), e-PTFE, polypropylene (PP), polyphenylene sulfide (PPS), copolymers thereof or their Mixtures, etc. can be used, and among these, polyimide, PPS, e-PTFE, or PTFE, which has better heat resistance, chemical resistance, and dimensional stability, is preferable.

In one embodiment, the thickness of the porous support 5 may be 1 to 100 ㎛, preferably 1 to 50 ㎛, for example, 2 to 40 ㎛, or 3 to 30 ㎛. If the thickness of the porous support 5 is less than 1 ㎛, there is a risk that durability and dimensional stability may be reduced because the physical and mechanical properties of the reinforced composite membrane are not sufficiently secured, and if it exceeds 100 ㎛, impregnation with hydrogen ion conductive polymer may occur. It is difficult, and this may result in a decrease in hydrogen ion conductivity and deterioration in membrane performance.

The porosity of the porous support 5 may be 40 to 95%, for example, 50 to 90%, preferably 60 to 85%. If the porosity of the porous support 5 is less than 40%, the impregnation rate of the hydrogen ion conductive polymer may decrease, which may result in a decrease in membrane performance, and if it exceeds 95%, the durability and mechanical rigidity of the reinforced composite membrane may decrease. This may not be sufficiently secured.

The reinforced composite membrane 10 is impregnated with the hydrogen ion conductive polymer into a porous support 5, or an electrolyte layer 1 and/or 3 containing the hydrogen ion conductive polymer on at least one side of the porous support 5. This may have been formed.

In the case where the hydrogen ion conductive polymer is impregnated into the porous support 5, a mixed solution is prepared by dispersing the hydrogen ion conductive polymer in a solvent, and then the porous support 5 is immersed in the mixed solution to form the porous support ( 5) A reinforced composite membrane impregnated with hydrogen ion conductive polymer can be formed. The solvent may be water, a hydrophilic solvent, an organic solvent, or a mixed solvent of two or more thereof.

In the case of a reinforced composite membrane (10) in which an electrolyte layer (1 and/or 3) containing the hydrogen ion conductive polymer is formed on at least one side of the porous support (5), the hydrogen on at least one side of the porous support (5) A process of applying a mixed solution of ion conductive polymers and drying the mixed solution, or casting the mixed solution and drying it to form an electrolyte membrane containing a hydrogen ion conductive polymer, and laminating it with at least one side of the porous support 5. It can be formed through In addition, when forming the electrolyte layer (1 and/or 3) in a multilayer structure, a mixed solution of different concentrations and types of hydrogen ion conductive polymer is sequentially applied and dried or laminated to the porous support (5). It can be rough. At this time, application or casting of the mixed solution may be performed through bar coating, comma coating, slot die, screen printing, spray coating, doctor blade, or laminating.

Alternatively, the reinforced composite membrane 10 is formed by laminating an electrolyte membrane containing a hydrogen ion polymer on at least one surface of the porous support 5 impregnated with the hydrogen ion conductive polymer to form an electrolyte layer (1 and/or 3). may include.

The drying can be performed by applying heat at 60°C to 100°C for about 1 to 30 minutes, or preferably by applying heat at 70°C to 90°C for about 5 to 15 minutes. At this time, if the drying temperature is less than 60 ℃, the liquid retention property of the hydrogen ion conductive polymer solution may be reduced, and if it exceeds 100 ℃, the adhesion to the electrode may be reduced when manufacturing the reinforced composite membrane and/or the membrane-electrode assembly.

The reinforced composite membrane 10 according to one embodiment includes a porous support 5 impregnated with a hydrogen ion conductive polymer, or an electrolyte layer 1 and/ including a hydrogen ion conductive polymer on at least one side of the porous support 5. Or, as 3) is provided, it includes a structure in which hydrogen ion conductive polymers are continuously distributed from the surface of the porous support 5 in the thickness direction of the reinforced composite membrane 10, so that the ionic conductivity of the reinforced composite membrane is improved. there is.

The hydrogen ion conductive polymer can be used without particular restrictions as long as it is commonly used as a hydrogen ion conductor in the electrolyte membrane of a fuel cell. Specifically, it is a fluorine-based polymer that has an excellent hydrogen ion conduction function, is advantageous in terms of price, and is soluble in organic solvents. , hydrocarbon-based polymers, or mixtures thereof can be used.

Specifically, it is recommended to use a polymer having an ion exchange capacity (IEC) of 0.8 meq/g or more as the hydrogen ion conductive polymer. By using a polymer with such a high ion exchange capacity, it is possible to lower the content of hydrogen ion conductive polymer in the composition for forming a porous support, and as a result, it is possible to prevent a decrease in the strength and dimensional stability of the porous support due to the use of hydrogen ion conductive polymer. can do.

The hydrogen ion conductive polymer may further include a cation exchanger to ensure ion conductivity of the electrolyte membrane. Specifically, the cation exchanger may include a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphoric acid group, an imide group, a sulfonimide group, and a sulfonamide group. , and may be selected from the group consisting of a sulfonic acid fluoride group. More specifically, the hydrogen ion conductive polymer according to an embodiment of the present invention may be a hydrogen ion conductive polymer having a sulfonic acid group and/or a carboxyl group as a cation exchange group.

Specific examples of the hydrogen ion conductive polymer include poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, and defluorinated sulfated poly. Fluorinated polymers containing etherketone or mixtures thereof, sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (sulfonated polyetheretherketone, SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyethersulfone ( sulfonated polyether sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide Sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether. nitrile), sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, and mixtures thereof, including hydrocarbon polymers and mixtures thereof. Any one selected from the group can be used.

In one embodiment, the hydrogen ion conductive polymer or the porous support may include a crosslinking portion (hereinafter also referred to as a “crosslinking portion”) derived from a crosslinking agent.

The cross-linked portion may be introduced into a hydrogen ion-conducting polymer or a porous support. Specifically, in the case of the hydrogen ion-conducting polymer, the cross-linked portion may be introduced into the side chain of the polymer, and in the case of a porous support, the cross-linked portion may be introduced to the surface through surface modification. A cross-linked moiety may be introduced through a cross-linking monomer into the side chain of the polymer constituting the porous support, resulting in the cross-linking moiety being introduced to the surface of the porous support.

The crosslinking portion included in the hydrogen ion conductive polymer and the porous support may include, for example, a hydroxy group (-OH), a carboxyl group (-COOH), an amine group (-NH ₂ ), a halogen, or a combination thereof. Here, the halogen may be -F, -Cl, -Br, or -I.

In one embodiment, the reinforced composite membrane for a fuel cell may form a crosslinked structure through a crosslinked portion included in the hydrogen ion conductive polymer or a crosslinked portion included in the porous support.

The crosslinking portion may be derived from at least one selected from the group consisting of dicarboxylic acid-based compounds, diamine-based compounds, glycol-based compounds, phenols substituted with halogens, benzoic acids substituted with halogens, and phenols substituted with carboxyl groups. . That is, the crosslinking agent may be at least one selected from the group consisting of dicarboxylic acid-based compounds, diamine-based compounds, glycol-based compounds, phenols substituted with halogens, benzoic acids substituted with halogens, and phenols substituted with carboxyl groups.

Specifically, the dicarboxylic acid-based compound may be represented by the formula HOOC-R ¹ -COOH, where R ¹ may be an alkylene group having 1 to 20 carbon atoms, a phenyl group, a naphthyl group, or a biphenyl group. For example, the dicarboxylic acid-based compounds may include oxalic acid and tepthalic acid.

Specifically, the diamine-based compound may be represented by the formula H ₂ NR ² -NH ₂ , where R ² may be an alkylene group having 1 to 20 carbon atoms, a phenyl group, a naphthyl group, or a biphenyl group. For example, the diamine-based compound may include hydrazine, ethylene diamine, etc.

Specifically, the glycol-based compound may be represented by the formula HO-R ³ -OH, where R ³ may be an alkylene group, a phenyl group, a naphthyl group, or a biphenyl group having 1 to 20 carbon atoms. For example, the glycol-based compound may include ethylene glycol.

Specifically, in the halogen-substituted phenol and halogen-substituted benzoic acid, the halogen may be fluorine, chlorine, or iodine. Examples of the halogen-substituted phenol and halogen-substituted benzoic acid may include diiodophenol and 2,6-dichlorobenzoic acid.

Specifically, the phenol substituted with the carboxyl group may be a phenol in which the carboxyl group is directly substituted with or without a linker, where the linker is an alkylene group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms. You can. For example, phenols substituted with the carboxyl group may include salicylic acid and coumaric acid.

Specific types of the crosslinking agent may include hydrazine, ethylene diamine, oxalic acid, terephthalic acid, ethylene glycol, diiodophenol, 2,6-dichlorobenzoic acid, salicylic acid, and coumaric acid.

The crosslinking agent may be included in an amount of 0.01 to 10 parts by weight, for example, 0.05 to 8 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the reinforced composite membrane.

Another embodiment of the present invention includes the steps of (a) contacting the porous support with a cross-linking agent to prepare a porous support into which a cross-linking portion is introduced; and (b) impregnating the porous support with a hydrogen ion conductive polymer or forming an electrolyte layer containing a hydrogen ion conductive polymer on at least one surface of the porous support including the crosslinking portion. Reinforced composite for fuel cells, comprising the step of: A method for manufacturing a membrane is provided.

Since the hydrogen ion conductive polymer, porous support, and crosslinking portion have been described in detail previously, repeated descriptions thereof will be omitted.

Looking at each step below, step (a) is a step of introducing a crosslinking portion into the porous support through a crosslinking agent. The porous support may be surface treated by plasma treatment, UV treatment, or ultrasonic treatment and then contacted with the crosslinking agent. Surface treatment by plasma treatment, UV treatment, or ultrasonic treatment allows the crosslinking agent to introduce a crosslinking portion through a reaction on the surface of the porous support.

The crosslinking agent may be in contact with the porous support in the form of a solution dissolved in a solvent such as alcohol. The solution containing the cross-linking agent may be contacted with the porous support by being applied on the porous support by a conventional solution process, such as spray application, spin application, or inkjet printing application.

The crosslinking agent capable of introducing a crosslinking reactive group into the porous support through step (a) may preferably be at least one selected from the group consisting of dicarboxylic acid-based compounds, diamine-based compounds, and glycol-based compounds.

The content of the crosslinking agent in the solution may be 0.1 to 30% by weight, preferably 5 to 20% by weight, based on the weight of the crosslinking agent relative to the porous support in the polymer electrolyte membrane.

If the content of the crosslinking agent is less than 0.1% by weight, there may be a problem in that it is difficult to express the effect of crosslinking throughout the polymer electrolyte membrane, and if it exceeds 30% by weight, the fluidity of the polymer is limited and conductivity and performance are reduced. There may be.

Step (b) is a step of impregnating a porous support including a crosslinking portion with a hydrogen ion conductive polymer, or forming an electrolyte layer including a hydrogen ion conducting polymer on at least one side of the porous support including the crosslinking portion.

The hydrogen ion conductive polymer can be impregnated in the form of a solution, and the method of impregnating the porous support is not limited to a specific method, and various methods known in the art, such as a spray process, screen printing process, and doctor blade process, can be used. there is. When using the impregnation process, it is preferable to perform the impregnation process 1 to 5 times for 5 to 30 minutes at room temperature.

As a method of forming an electrolyte layer containing the hydrogen ion conductive polymer on at least one surface of the porous support including the crosslinking portion, a solution of the hydrogen ion conductive polymer is cast and dried to form an electrolyte membrane, and the electrolyte is formed. It may include combining the membrane with the porous support.

It is preferable that the hydrogen ion conductive polymer is appropriately determined considering the content of the hydrogen ion conductive polymer contained in the reinforced composite membrane. Specifically, it may be included in an amount of 5 to 40% by weight in the solution containing the hydrogen ion conductive polymer. When the hydrogen ion conductive polymer is contained in an amount of less than 5% by weight in a solution containing the hydrogen ion conductive polymer, the hydrogen ion conductive polymer may not sufficiently fill the pores of the porous support and form empty spaces, and the hydrogen ion conductive polymer may be 40% by weight. If the weight percent is exceeded, the viscosity of the solution containing the hydrogen ion conductive polymer may be too high to fill the pores of the porous support.

After filling the solution containing the hydrogen ion conductive polymer, the organic solvent in the solution containing the hydrogen ion conductive polymer is removed so that the pores of the porous support are filled with the hydrogen ion conductive polymer. Therefore, the method of manufacturing a reinforced composite membrane for a fuel cell according to the present invention may further include a process of removing the organic solvent after filling with the hydrogen ion conductive polymer, and the organic solvent removal process is performed in a vacuum oven at 60 to 150 ° C. for 2 to 15 minutes. It can be done through a drying process for a period of time.

Another embodiment of the present invention includes the step of (c) polymerizing at least one type of monomer with a cross-linking agent to produce a polymer into which a cross-linking moiety is introduced; (d) preparing a porous support or hydrogen ion conductive polymer from the polymer; and (e) impregnating the porous support with a hydrogen ion conductive polymer or forming an electrolyte layer containing the hydrogen ion conductive polymer on at least one surface of the porous support. .

In step (c), the type of monomer and the type of polymerization reaction are not particularly limited and can be appropriately selected depending on the type of the desired hydrogen ion conductive polymer or porous support. The cross-linking agent polymerized together with the monomer is not particularly limited as long as it is a compound capable of introducing a cross-linking moiety into the side chain of the polymer through a polymerization reaction, for example, at least one selected from halogen-substituted phenol and halogen-substituted benzoic acid. can be used.

In step (d), the step of preparing the porous support or hydrogen ion conductive polymer may be performed using a conventional method. For example, the porous support may be a stretched film or a non-woven web. In the case of a non-woven web, fibers may be formed through melt spinning and then manufactured as a non-woven fabric through a sheet forming machine.

Since step (e) is the same as step (b) described above, repetitive description will be omitted.

The reinforced composite membrane manufactured by the above manufacturing method has excellent hydrogen ion conductivity and can exhibit improved hydrogen ion conductivity when used as a polymer electrolyte membrane in a membrane-electrode assembly for fuel cells.

According to another embodiment of the present invention, a membrane-electrode assembly and a fuel cell including the reinforced composite membrane are provided.

Specifically, the membrane-electrode assembly includes an anode electrode and a cathode electrode positioned opposite to each other, and the reinforced composite membrane positioned between the anode electrode and the cathode electrode.

Figure 2 is a cross-sectional view schematically showing a membrane-electrode assembly according to an embodiment of the present invention. 2, the membrane-electrode assembly 100 includes the reinforced composite membrane 50 and the fuel cell electrodes 20 and 20' disposed on both sides of the reinforced composite membrane 50, respectively. . The electrodes 20, 20' include an electrode substrate 40, 40' and a catalyst layer 30, 30' formed on the surface of the electrode substrate 40, 40'. A fine pore layer (not shown) containing conductive fine particles such as carbon powder and carbon black is provided between the catalyst layers 30 and 30' to facilitate diffusion of materials from the electrode substrates 40 and 40'. It may include more.

In the membrane-electrode assembly 100, an oxidation reaction that generates hydrogen ions and electrons from fuel disposed on one side of the reinforced composite membrane 50 and transferred to the catalyst layer 30 through the electrode substrate 40 The electrode 20 that causes this is called an anode electrode, and is disposed on the other side of the reinforced composite film 50, where hydrogen ions supplied through the reinforced composite film 50 pass through the electrode base 40' and the catalyst layer ( The electrode 20' that causes a reduction reaction to generate water from the oxidant delivered to 30' is called a cathode electrode.

The catalyst layers 30 and 30' of the anode and cathode electrodes 20 and 20' contain a catalyst. As the catalyst, any catalyst that participates in the reaction of the battery and can be used as a catalyst for a normal fuel cell can be used. Specifically, platinum-based metals can be preferably used.

The platinum-based metals include platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), and platinum-M alloy (where M is palladium (Pd), ruthenium (Ru), and iridium ( Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper ( Any one selected from the group consisting of Cu), silver (Ag), gold (Au), zinc (Zn), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La), and rhodium (Rh) or more), non-platinum alloys, and combinations thereof, and more preferably a combination of two or more metals selected from the platinum-based catalyst metal group, but is limited thereto. This does not mean that any platinum-based catalyst metal available in the present technical field can be used without limitation.

Specifically, the platinum alloy is Pt-Pd, Pt-Sn, Pt-Mo, Pt-Cr, Pt-W, Pt-Ru, Pt-Ru-W, Pt-Ru-Mo, Pt-Ru-Rh-Ni, Pt-Ru-Sn-W, Pt-Co, Pt-Co-Ni, Pt-Co-Fe, Pt-Co-Ir, Pt-Co-S, Pt-Co-P, Pt-Fe, Pt-Fe- Ir, Pt-Fe-S, Pt-Fe-P, Pt-Au-Co, Pt-Au-Fe, Pt-Au-Ni, Pt-Ni, Pt-Ni-Ir, Pt-Cr, Pt-Cr- Ir and combinations thereof can be used alone or in combination of two or more.

In addition, the non-platinum alloys include Ir-Fe, Ir-Ru, Ir-Os, Co-Fe, Co-Ru, Co-Os, Rh-Fe, Rh-Ru, Rh-Os, Ir-Ru-Fe, Ir -Ru-Os, Rh-Ru-Fe, Rh-Ru-Os, and combinations thereof can be used alone or in combination of two or more.

This catalyst can be used as the catalyst itself (black) or can be used by supporting it on a carrier.

The carrier may be selected from carbon-based carriers, porous inorganic oxides such as zirconia, alumina, titania, silica, and ceria, and zeolites. The carbon-based carrier includes graphite, super P, carbon fiber, carbon sheet, carbon black, Ketjen Black, Denka black, and acetylene. acetylene black, carbon nano tube (CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, carbon nanofiber, carbon nanowire, carbon nanoball , carbon nano horn, carbon nano cage, carbon nano ring, ordered nano-/meso-porous carbon, carbon airgel, mesoporous carbon, graphene, stabilized carbon, activated carbon, and It may be selected from one or more combinations of these, but is not limited thereto, and any carrier available in the present technical field may be used without limitation.

The catalyst particles may be located on the surface of the carrier or may penetrate into the carrier while filling the internal pores of the carrier.

When using the noble metal supported on the carrier as a catalyst, a commercially available catalyst can be used, or it can also be prepared and used by supporting the noble metal on the carrier. The process of supporting precious metals on the carrier is widely known in the field, so detailed description is omitted in this specification, but it can be easily understood by those working in the field.

The catalyst particles may be contained in an amount of 20% to 80% by weight relative to the total weight of the catalyst electrodes 30, 30', and if contained in less than 20% by weight, there may be a problem of reduced activity, and 80% by weight. If it exceeds %, the active area may decrease due to agglomeration of the catalyst particles, and the catalyst activity may conversely decrease.

Additionally, the catalyst electrodes 30, 30' may include a binder to improve the adhesion of the catalyst electrodes 30, 30' and to transmit hydrogen ions. It is preferable to use an ion conductor having ion conductivity as the binder, and since the description of the ion conductor is the same as above, repeated descriptions will be omitted.

However, the ion conductor can be used singly or in the form of a mixture, and may optionally be used together with a non-conductive compound to further improve adhesion to the reinforced composite film 50. It is desirable to adjust the amount used to suit the purpose of use.

The non-conductive compounds include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl ether copolymer (PFA), and ethylene/tetrafluoroethylene. Roethylene (ethylene/tetrafluoroethylene (ETFE)), ethylene chlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dode One or more types selected from the group consisting of silbenzenesulfonic acid and sorbitol may be used.

The binder may be included in an amount of 20% to 80% by weight based on the total weight of the catalyst electrodes 30 and 30'. If the binder content is less than 20% by weight, the generated ions may not be transmitted well, and if it exceeds 80% by weight, it is difficult to supply hydrogen or oxygen (air) due to insufficient pores, and the active area that can react This may decrease.

A porous conductive substrate may be used as the electrode substrate 40, 40' to ensure smooth supply of hydrogen or oxygen. Representative examples include carbon paper, carbon cloth, carbon felt, or metal cloth (a porous film made of fibrous metal cloth or a metal film formed on the surface of a cloth made of polymer fibers). can be used, but is not limited to this. In addition, it is preferable to use the electrode substrates 40 and 40' treated with water-repellent fluorine-based resin to prevent reactant diffusion efficiency from being reduced by water generated during operation of the fuel cell. The fluorine-based resins include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxyvinyl ether, and fluorinated ethylene propylene ( Fluorinated ethylene propylene), polychlorotrifluoroethylene, or their copolymers can be used.

In addition, a microporous layer may be further included to enhance the diffusion effect of reactants in the electrode substrates 40 and 40'. This microporous layer is generally made of conductive powders with small particle sizes, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotubes, carbon nanowires, and carbon nanohorns. -horn) or carbon nano ring (carbon nano ring).

The microporous layer is manufactured by coating the electrode substrates 40 and 40' with a composition containing conductive powder, binder resin, and solvent. The binder resin includes polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxyvinyl ether, polyvinyl alcohol, and cellulose acetate. Or their copolymers, etc. may be preferably used. As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, etc. may be preferably used. The coating process may use a screen printing method, a spray coating method, or a coating method using a doctor blade, depending on the viscosity of the composition, but is not limited thereto.

The membrane-electrode assembly 100 can be manufactured according to a conventional manufacturing method of a membrane-electrode assembly for a fuel cell, except that the reinforced composite membrane 50 according to the present invention is used as the reinforced composite membrane 50. there is.

A fuel cell according to another embodiment of the present invention may include the membrane-electrode assembly 100.

Figure 3 is a schematic diagram showing the overall configuration of the fuel cell.

Referring to FIG. 3, the fuel cell 200 includes a fuel supply unit 210 that supplies a mixed fuel containing fuel and water, and a reforming unit that reforms the mixed fuel to generate a reformed gas containing hydrogen gas ( 220), a stack 230 in which a reformed gas containing hydrogen gas supplied from the reforming unit 220 undergoes an electrochemical reaction with an oxidant to generate electrical energy, and the oxidizing agent is supplied to the reforming unit 220 and the stack. It includes an oxidizing agent supply unit 240 supplied to 230.

The stack 230 includes a plurality of unit cells that generate electrical energy by inducing an oxidation/reduction reaction between the reformed gas containing hydrogen gas supplied from the reforming unit 220 and the oxidizing agent supplied from the oxidizing agent supply unit 240. Equipped with

Each unit cell refers to a unit cell that generates electricity, and includes the membrane-electrode assembly that oxidizes/reduces oxygen in the reformed gas containing hydrogen gas and the oxidant, and the reformed gas containing hydrogen gas and the oxidizing agent. It includes a separator plate (also called a bipolar plate, hereinafter referred to as a 'separator plate') for supply to the membrane-electrode assembly. The separator is placed on both sides of the membrane-electrode assembly with the membrane at the center. At this time, the separator plates located on the outermost side of the stack are sometimes called end plates.

Among the separation plates, the end plate includes a first pipe-shaped supply pipe 231 for injecting reformed gas containing hydrogen gas supplied from the reforming unit 220, and a second pipe-shaped supply pipe 231 for injecting oxygen gas. A supply pipe 232 is provided, and the other end plate includes a first discharge pipe 233 for discharging to the outside the reformed gas containing the hydrogen gas that is ultimately unreacted and remaining in the plurality of unit cells, and the unit cell A second discharge pipe 234 is provided to discharge the unreacted and remaining oxidant to the outside.

In the fuel cell, except that the membrane-electrode assembly 100 according to an embodiment of the present invention is used, the separator, fuel supply unit, and oxidant supply unit constituting the electricity generation unit are used in a typical fuel cell. , detailed description is omitted in this specification.

Below, specific embodiments of the present invention are presented. However, the examples described below are only for illustrating or explaining the present invention in detail, and do not limit the present invention. In addition, any content not described herein can be sufficiently inferred technically by a person skilled in the art, so description thereof will be omitted.

Manufacturing Example 1

The surface of e-PTFE (thickness: 10㎛, basis weight: 10g/ ^m2 ) used as a support is modified using atmospheric pressure plasma, and then ethanol containing 20% by weight of oxalic acid dissolved is sprayed on the surface. The above process is carried out through the R2R process, the process speed is 1 m/min, and the amount of oxalic acid applied to the completely processed PTFE surface per area is 0.5 g/m ² .

Production example 2

One polymer was synthesized using a mixture of pDIB and sulfur, and another polymer was synthesized using a mixture of pDIB, sulfur, and 2,6-Dichlorobenzoic acid. The above mixtures were heated from 230°C to 300°C, and the pressure was gradually reduced from 170 torr to 1 torr or less, and polymerization was performed for a total of 8 hours to prepare a PPS copolymer containing PPS and a repeating unit having a hydroxyl group. Fibers were obtained by spinning two types of polymers in a melt spinning device, and chopping them to a length of about 5 mm. After dispersing the chopped fibers in water at high speed, nonwoven fabric was manufactured using a sheet former. Among the nonwoven fabrics prepared above, the nonwoven fabrics were placed in the order of PPS copolymer, pure PPS, and PPS copolymer, dried, and then calendared to prepare a PPS copolymer nonwoven web with a crosslinking agent introduced only on the surface.

Example 1

A 20 wt% dispersion of Nafion (Chemours) as a hydrogen ion conductive polymer was soaked in the porous film of polytetrafluoroethylene (PTFE) prepared in Preparation Example 1, dried in an oven at 90°C for 12 hours, and then dried at 150°C. A reinforced composite membrane was manufactured by heat treatment at ℃ for 20 minutes.

Example 2

A reinforced composite membrane was prepared in the same manner as in Example 1, except that the PTFE material of Preparation Example 1 was chemically modified to introduce a hydroxyl group into the porous film using ethylene glycol instead of oxalic acid.

Example 3

A dispersion was prepared by dissolving 15% by weight of sulfonated poly(ether sulfone), a hydrocarbon-based ion conductor, in DMAc solvent as a hydrogen ion conductive polymer.

The prepared mixed solution was soaked in a porous film made of polyphenylene sulfide (PPS) with a thickness of 10 μm in Preparation Example 2, dried in an oven at 90°C for 24 hours, and then heat treated at 120°C for 30 minutes to prepare a reinforced composite membrane. .

Example 4

A reinforced composite membrane was manufactured in the same manner as in Example 3, except that a nonwoven fabric prepared using Diiodophenol instead of 2,6-Dichlorobenzoic acid was used to introduce hydroxyl groups into the porous film made of PPS.

Comparative Example 1

A 20 wt% dispersion of Nafion (Chemours) was prepared as a hydrogen ion conductive polymer.

A 10 ㎛ thick porous film made of polytetrafluoroethylene (PTFE) sprayed on the surface with an oxalic acid/ethanol solution was soaked with the prepared mixture, dried in an oven at 90°C for 12 hours, and then heat treated at 150°C for 20 minutes. A reinforced composite membrane was manufactured. All ethanol applied to the PTFE surface is removed during the coating and drying process, and the amount applied to the PTFE surface is 0.5 g/m ² .

Comparative Example 2

A dispersion was prepared by dissolving 15% by weight of sulfonated poly(ether sulfone), a hydrocarbon-based ion conductor, in DMAc solvent as a hydrogen ion conductive polymer.

The prepared mixed solution was soaked in a 10 ㎛ thick porous film made of polyphenylene sulfide (PPS), dried in an oven at 90°C for 24 hours, and then heat treated at 120°C for 30 minutes to prepare a reinforced composite membrane.

Membrane-electrode assembly Preparation Examples 1 to 4 and Comparative Preparation Examples 1 to 2

A membrane-electrode assembly was manufactured by forming an electrode layer on the polymer electrolyte membrane prepared in Examples 1 to 4 and Comparative Examples 1 to 2 using a decal method. At this time, the catalyst layer of the electrode is formed by applying a catalyst layer-forming composition containing a Pt/carbon catalyst to a release film and then drying it to form a catalyst layer, and the catalyst layer-coated release film is placed on both sides of the reinforced composite membrane so that the catalyst layer and the reinforced composite membrane face each other. After positioning, hot pressing was performed at a pressure of 5 kg/cm ² and a temperature of 100° C. to transfer the catalyst layer to both sides of the polymer electrolyte membrane. Next, a gas diffusion layer (GDL) was fastened to both sides of the polymer electrolyte membrane to which the catalyst layer was bonded to manufacture a membrane-electrode assembly.

Experimental Example 1: Ion conductivity (experiment conditions: 80℃/50% RH)

For the membrane-electrode assembly including the reinforced composite membrane according to the above manufacturing example, ion conductivity was measured using a measuring device (Solatron-1280Impedance/Gain-Phase analyzer from Solatron) at a measurement temperature of 80°C. Specifically, ohmic resistance or bulk resistance was measured using the four point probe AC impedance spectroscopic method, and then ion conductivity was calculated using Equation 4 below.

[Equation 4]

In Equation 4, σ is the ionic conductivity (S/cm), R is the ohmic resistance of the electrolyte membrane (Ω), L is the distance between electrodes (cm), and S is the area within the electrolyte through which a constant current flows (cm2). .

Experimental Example 2: Dimensional stability evaluation

The polymer electrolyte membrane was dried in a vacuum oven at 80°C for 12 hours and its dimensions were measured. After being immersed in distilled water at room temperature for 24 hours, the dimensions were measured and the dimensional ratio before and after moisture absorption was compared. The lower the dimensional change rate, the higher the stability.

Sample name Crosslinking degree (%) Conductivity (S/cm) Dimensional change rate (%) Comparative Example 1 2 0.037 8 Comparative Example 2 2 0.024 12 Example 1 2 0.040 4 Example 2 2 0.042 5 Example 3 2 0.030 6 Example 4 2 0.031 7

Although the preferred embodiments of the present invention have been described in detail above, the above-described embodiments are presented as specific examples of the present invention, and the present invention is not limited thereto, and the scope of the present invention is defined by the claims described later. Various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in also fall within the scope of the present invention.

10, 50: Reinforced composite membrane
1,3: electrolyte layer 5: porous support
20, 20': electrode
30, 30': Catalyst layer
40, 40': electrode substrate
100: Membrane-electrode assembly
200: Fuel cell
210: fuel supply unit 220: reforming unit
230: stack 231: first supply pipe
232: second supply pipe 233: first discharge pipe
234: second discharge pipe 240: oxidizing agent supply unit

Claims (16)

A reinforced composite membrane comprising a porous support and a hydrogen ion conductive polymer,
The reinforced composite membrane is impregnated with the hydrogen ion conductive polymer into the porous support, or includes an electrolyte layer containing the hydrogen ion conductive polymer on at least one surface of the porous support,
The hydrogen ion conductive polymer or the porous support includes a crosslinking portion derived from a crosslinking agent,
Reinforced composite membrane for fuel cells. In paragraph 1:
The crosslinking portion contained in the hydrogen ion conductive polymer or the porous support is a hydroxy group (-OH), a carboxyl group (-COOH), an amine group (-NH ₂ ), a halogen, or a combination thereof, a reinforced composite membrane for a fuel cell. In paragraph 1:
The crosslinking portion is derived from at least one selected from the group consisting of dicarboxylic acid-based compounds, diamine-based compounds, glycol-based compounds, phenols substituted with halogens, benzoic acids substituted with halogens, and phenols substituted with carboxyl groups. Reinforced composite membrane for fuel cells. In paragraph 1:
A reinforced composite membrane for a fuel cell, wherein the crosslinking portion is introduced into the surface of the porous support. In paragraph 1:
The hydrogen ion conductive polymer is a reinforced composite for a fuel cell comprising a cation exchanger selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphoric acid group, an imide group, a sulfonimide group, a sulfonamide group, and a sulfonic acid fluoride group. membrane. In paragraph 1:
The porous support is a stretched film or non-woven web, a reinforced composite membrane for a fuel cell. In paragraph 1:
A reinforced composite membrane for a fuel cell, wherein the porous support has a thickness of 1 to 100 ㎛. (a) preparing a porous support into which a crosslinking portion is introduced by contacting the porous support with a crosslinking agent; and
(b) impregnating the porous support with a hydrogen ion conductive polymer or forming an electrolyte layer containing a hydrogen ion conductive polymer on at least one side of the porous support including the crosslinking portion.
Method for manufacturing reinforced composite membrane for fuel cell. In paragraph 8:
In step (a), the porous support is surface treated by plasma treatment, UV treatment, or ultrasonic treatment and then contacted with the crosslinking agent. In paragraph 8:
In step (a), the cross-linking agent is applied in solution form on the porous support by spraying, spin coating, or inkjet printing to contact the porous support. (c) polymerizing at least one type of monomer with a cross-linking agent to produce a polymer into which a cross-linking moiety is introduced;
(d) preparing a porous support or hydrogen ion conductive polymer from the polymer; and
(e) impregnating the porous support with a hydrogen ion-conducting polymer or forming an electrolyte layer containing the hydrogen ion-conducting polymer on at least one side of the porous support,
Method for manufacturing reinforced composite membrane for fuel cell. In paragraph 8 or 11:
The crosslinking portion is a hydroxyl group (-OH), a carboxyl group (-COOH), an amine group (-NH ₂ ), a halogen, or a combination thereof. A method of manufacturing a reinforced composite membrane for a fuel cell. In paragraph 8:
A method of producing a reinforced composite membrane for a fuel cell, wherein the crosslinking agent is at least one selected from the group consisting of dicarboxylic acid-based compounds, diamine-based compounds, and glycol-based compounds. In paragraph 11:
The cross-linking agent is at least one selected from the group consisting of phenol substituted with a halogen, benzoic acid substituted with a halogen, and phenol substituted with a carboxyl group. an anode electrode and a cathode electrode positioned opposite each other,
Reinforced composite membrane for a fuel cell according to claim 1 located between the anode electrode and the cathode electrode.
A membrane-electrode assembly comprising a. A fuel cell comprising the membrane-electrode assembly according to claim 15.