KR102743229B1 - Electrolyte membrane for fuel cell and fuel cell comprising same - Google Patents

Abstract

The present invention relates to a polymer electrolyte membrane for a fuel cell and a fuel cell comprising the same, and more specifically, the polymer electrolyte membrane comprises a crosslinker having a specific structure and an ion conductor including at least one functional group selected from the group consisting of a carboxyl group and a sulfonic acid group, thereby providing a polymer electrolyte membrane for a fuel cell with improved resistance to chemical deterioration and a fuel cell comprising the same.

Description

Polymer electrolyte membrane for fuel cell and fuel cell comprising the same {ELECTROLYTE MEMBRANE FOR FUEL CELL AND FUEL CELL COMPRISING SAME}

The present invention relates to a polymer electrolyte membrane for a fuel cell and a fuel cell including the same.

A polymer electrolyte membrane fuel cell (PEMFC) is a type of fuel cell that is attracting attention as a next-generation energy source. It is a fuel cell that uses a polymer membrane with hydrogen ion exchange properties as an electrolyte.

A fuel cell is a battery equipped with a power generation system that directly converts chemical reaction energy, such as oxidation/reduction reactions of hydrogen and oxygen contained in hydrocarbon fuels such as methanol, ethanol, and natural gas, into electrical energy. Due to its high energy efficiency and environmentally friendly characteristics of low pollutant emissions, it is attracting attention as a next-generation clean energy source that can replace fossil energy.

These fuel cells have the advantage of being able to produce a wide range of outputs through a stack configuration in which unit cells are laminated, and because they exhibit an energy density that is 4 to 10 times higher than that of small lithium batteries, they are attracting attention as small and portable power sources.

The stack that actually generates electricity in a fuel cell has a structure in which several to several dozen unit cells composed of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate) are stacked, and the membrane-electrode assembly generally has an anode (or fuel electrode) and a cathode (or air electrode) arranged on both sides with an electrolyte membrane in between.

Fuel cells can be classified into alkaline electrolyte fuel cells and polymer electrolyte membrane fuel cells (PEMFC) depending on the state and type of electrolyte. Among them, polymer electrolyte fuel cells are attracting attention as portable, vehicle, and home power supplies due to their advantages such as low operating temperature of less than 100℃, fast starting and response characteristics, and excellent durability.

A representative example of a polymer electrolyte fuel cell is the proton exchange membrane fuel cell (PEMFC), which uses hydrogen gas as fuel.

To summarize the reactions that occur in a polymer electrolyte fuel cell, first, when fuel such as hydrogen gas is supplied to the anode, hydrogen ions (H ⁺ ) and electrons ( ^e- ) are generated at the anode through the oxidation reaction of hydrogen. The generated hydrogen ions are transferred to the cathode through the polymer electrolyte membrane, and the generated electrons are transferred to the cathode through the external circuit. At the cathode, oxygen is supplied, and the oxygen combines with the hydrogen ions and electrons to generate water through the reduction reaction of oxygen.

Meanwhile, there are still many technical barriers to be overcome in order to commercialize polymer electrolyte fuel cells, and essential improvement factors include high performance, long life, and reduced production costs. The component that has the greatest influence on this is the membrane-electrode assembly, and among them, the polymer electrolyte membrane is one of the key elements that has the greatest influence on the performance and price of the membrane-electrode assembly.

The requirements of the polymer electrolyte membrane necessary for the operation of the above polymer electrolyte fuel cell include high hydrogen ion conductivity, chemical stability, low fuel permeability, high mechanical strength, low moisture content, and excellent dimensional stability. Conventional polymer electrolyte membranes tend to have difficulty in normally demonstrating high performance in specific temperature and relative humidity environments, especially in high temperature/low humidity conditions. Due to this, polymer electrolyte fuel cells using conventional polymer electrolyte membranes are limited in their scope of use.

Among the polymer electrolyte membranes currently in use, there is a fluorine-based resin, a perfluorosulfonic acid resin (hereinafter referred to as a "fluorine-based ion conductor"). However, the fluorine-based ion conductor has a weak mechanical strength, and pinholes occur when used for a long time, which causes a decrease in energy conversion efficiency. There are attempts to increase the thickness of the fluorine-based ion conductor membrane to reinforce the mechanical strength, but in this case, there are problems in that the resistance loss increases and the use of expensive materials increases, which reduces economic feasibility.

The purpose of the present invention is to provide an electrolyte membrane having excellent chemical durability and mechanical durability.

Another object of the present invention is to provide a membrane-electrode assembly comprising the polymer electrolyte membrane.

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

In order to achieve the above object, a polymer electrolyte membrane for a fuel cell according to one embodiment of the present invention is characterized in that the polymer electrolyte membrane includes a polymer electrolyte material, wherein the polymer electrolyte material includes: an ion conductor; and a crosslinking agent represented by the following chemical formula 1.

[Chemical Formula 1]

In the chemical formula 1, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently selected from hydrogen, deuterium, a sulfonic acid group, a carboxyl group, a hydroxyl group, an amine group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryloxy group having 1 to 10 carbon atoms, a and f are integers of 1 to 5, b, c, d and e are integers of 1 to 5, and chemical formula 1 includes two or more amine groups.

The above crosslinking agent may include a structure represented by the following chemical formula 2.

[Chemical formula 2]

The above ion conductor may have at least one functional group selected from a carboxyl group and a sulfonic acid group introduced to the side chain.

The above ion conductor may be a fluorine-based ion conductor, a hydrocarbon-based ion conductor, or a mixture thereof.

The crosslinking agent may be included in an amount of 0.05 to 20 wt% based on the total weight of the polymer electrolyte material.

It may further include a porous support having a plurality of pores filled with the polymer electrolyte material.

The above porous support may be an expanded film or a nonwoven fibrous web.

The ratio of the apparent volume of the porous support to the total volume of the polymer electrolyte membrane may be 5 to 90%.

A membrane-electrode assembly according to another embodiment of the present invention is characterized by including the polymer electrolyte membrane.

A fuel cell according to another embodiment of the present invention is characterized by including the membrane-electrode assembly.

A polymer electrolyte membrane for a fuel cell formed by crosslinking a crosslinking agent having a structure according to the present invention not only has excellent mechanical durability and chemical durability, but also has the effect of having minimal reduction in hydrogen ion permeability due to the crosslinking agent.

FIG. 1 is a cross-sectional view schematically illustrating a membrane electrode assembly according to one embodiment of the present invention.
Figure 2 is a schematic diagram illustrating the overall configuration of a fuel cell according to one embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

The detailed description and specific examples of the invention are intended to illustrate embodiments of the invention and are not intended to limit the scope of the invention. Furthermore, the publication of several embodiments does not exclude other embodiments having different features or other embodiments comprising combinations of the disclosed features.

As used herein, "preferred" or "preferably" refers to an embodiment of the invention that has a particular advantage under certain conditions. However, other embodiments may also be preferred under the same or different conditions. Furthermore, the fact that one or more preferred embodiments is not intended to imply that other embodiments are not useful, nor does it exclude other embodiments that are within the scope of the invention.

The term "including" as used herein is used to list materials, compositions, devices, and methods useful in the present invention, but is not limited to the listed examples.

A polymer electrolyte membrane for a fuel cell according to one aspect of the present invention comprises a polymer electrolyte material including an ion conductor and a cross-linking agent represented by the following chemical formula 1 for improving the durability of the ion conductor.

[Chemical Formula 1]

In the chemical formula 1, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently selected from hydrogen, deuterium, a sulfonic acid group, a carboxyl group, a hydroxyl group, an amine group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryloxy group having 1 to 10 carbon atoms, a and f are integers of 1 to 5, b, c, d and e are integers of 1 to 5, and chemical formula 1 includes two or more amine groups.

The crosslinking agent represented by Chemical Formula 1 contains two amine groups, so that when the ion conductor deteriorates as the fuel cell is operated, the crosslinking functional group binds to the deteriorated ion conductor, thereby inducing crosslinking of the ion conductor and improving the durability of the electrolyte membrane. Specifically, in Chemical Formula 1, R ¹ and R ⁶ are each independently -SO ₃ H, -COOH or -OH, and R ² , R ³ , R 4 and R ⁵ can each independently be -OH, -NH ₂ or -COOH for crosslinking. The crosslinking agent of Chemical Formula 1 has a property of containing moisture in a crosslinking structure in which it is difficult to form an ion cluster based on P having polarity, so as to minimize the decrease in conductivity.

The cross-linking agent exists in the polymer electrolyte membrane in a state where it is not bound to the ion conductor, but when the ion conductor is deteriorated due to long-term use of the fuel cell, it can induce cross-linking of the ion conductor by immediately binding to the deteriorated ion conductor through the cross-linking functional group without a separate temperature-raising process for cross-linking.

The crosslinker may include, for example, a structure represented by the following chemical formula 2.

[Chemical formula 2]

The ion conductor may be a cation conductor having at least one cation (proton 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, a sulfonic acid fluoride group, and combinations thereof. Preferably, the ion conductor according to one embodiment of the present invention may be a cation conductor having at least one functional group of a carboxyl group and a sulfonic acid group introduced into a side chain.

Additionally, the ion conductor may be a fluorine-based ion conductor, a hydrocarbon-based ion conductor, or a mixture thereof.

The fluorine-based ion conductor has a cation exchange group in the side chain and contains fluorine in the main chain, and for example, the fluorine-based polymer can be poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, or a mixture of two or more thereof.

Hydrocarbon ion conductors have cation exchange groups in their side chains, and examples thereof include sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, and sulfonated polyethersulfone. The polymer may include at least one selected from the group consisting of a sulfone, a sulfonated polyether ketone, a sulfonated polyphenylene sulfone, a sulfonated polyphenylene sulfide, a sulfonated polyphenylene sulfide sulfone, a sulfonated polyphenylene sulfide sulfone nitrile, a sulfonated polyarylene ether, a sulfonated polyarylene ether nitrile, a sulfonated polyarylene ether nitrile, and a sulfonated polyarylene ether sulfone ketone, but is not limited to the examples above.

The deterioration mechanism of a general hydrocarbon-based ion conductor is as shown in the following reaction scheme 1, and a fluorine-based ion conductor also deteriorates by a similar mechanism when there is a difference in electron density.

[Reaction Formula 1]

The radical terminal groups (e.g., -COO-, -CO-, etc.) and/or ionic terminal groups (-COO-, -0, -C0 ₂ , etc.) generated by the chemical deterioration of the ion conductor through decomposition of the main chain thereof chemically react with the crosslinkable functional group of the crosslinking agent of the present invention to form an amide group or an ester group, thereby crosslinking the deteriorated ion conductor.

In general, it is difficult for a crosslinking reaction of a fluorine-based or hydrocarbon-based ion conductor used in a polymer electrolyte membrane for a fuel cell to proceed below 100°C. However, when the ion conductor is deteriorated to generate the radical terminal group and/or the ionic terminal group, the radical terminal group and/or the ionic terminal group immediately reacts with the crosslinkable functional group of the crosslinking agent of the present invention, so that crosslinking of the deteriorated ion conductor can be forcibly proceeded without a separate temperature increasing process for crosslinking.

According to one embodiment of the present invention, the polymer electrolyte material may include 0.05 to 20 wt% of the crosslinking agent based on the total weight thereof.

If the content of the cross-linking agent is less than 0.05 wt%, it may be difficult for the cross-linking reaction of the deteriorated ion conductor to occur effectively, and if the content of the cross-linking agent exceeds 20 wt%, the cross-linking agent may cause a problem of interfering with ion transfer within the polymer electrolyte membrane. In this respect, it may be more preferable that the content of the cross-linking agent be 1 to 10 wt%.

The polymer electrolyte membrane of the present invention can be (i) a single membrane formed of the polymer electrolyte material or (ii) a reinforced composite membrane in which the pores of a porous support are filled with the polymer electrolyte material.

That is, the polymer electrolyte membrane of the reinforced composite membrane type according to one embodiment of the present invention further includes a porous support having a plurality of pores filled with the polymer electrolyte material.

Since the ion conductor used in the manufacture of the polymer electrolyte membrane of the present invention is a non-crosslinked ion conductor having superior fluidity compared to a crosslinked ion conductor, the pores of the porous support can be easily filled with the ion conductor. Accordingly, water channels through which hydrogen ions can move are well formed in the through plane of the porous support, so that the reinforced composite electrolyte membrane has relatively superior ion conductivity, while the flow paths through which hydrogen gas can move become complex, so that the reinforced composite electrolyte membrane can have relatively low hydrogen gas permeability.

According to one embodiment of the present invention, the porous support may preferably be an expanded film or a nonwoven fibrous web.

The ratio of the apparent volume of the porous support to the total volume of the polymer electrolyte membrane may be 5 to 90%.

If the ratio is less than 5%, the effects of improving dimensional stability and mechanical durability due to the adoption of the porous support may be minimal, and if the ratio exceeds 90%, the thickness of the ion conductor layer positioned on the upper or lower surface of the porous support may be too thin, which may increase surface resistance. In this regard, it may be more preferable that the ratio of the apparent volume of the porous support to the total volume of the polymer electrolyte membrane be 30 to 60%.

For similar reasons as above, the ratio of the thickness of the porous support to the total thickness of the polymer electrolyte membrane may be 5 to 90%, more preferably 30 to 60%.

A porous support according to one embodiment of the present invention may have a thickness of 1 to 50 μm.

When the thickness of the porous support is less than 1 ㎛, the mechanical strength of the polymer electrolyte membrane may decrease, and when the thickness of the porous support exceeds 50 ㎛, the resistance loss may increase and the weight reduction and integration may decrease. In this respect, the porous support may preferably have a thickness of 2 to 40 ㎛, more preferably 3 to 30 ㎛, and even more preferably 3 to 20 ㎛.

The porosity of the porous support may be 45 to 90%, specifically 60 to 90%. If the porosity of the porous support is less than 45%, the amount of ion conductor within the porous support may be excessively small, which may increase the resistance of the polymer electrolyte membrane and decrease the ion conductivity. If the porosity of the porous support exceeds 90%, the shape stability may be reduced, which may prevent the subsequent process from proceeding smoothly.

The above porosity means the ratio of the air volume within the porous support to the total volume of the porous support. The total volume of the porous support can be obtained by measuring the width, length, and thickness of a rectangular parallelepiped sample and multiplying them, and the air volume within the porous support can be obtained by subtracting the volume of the material obtained by dividing the mass of the sample by the density of the porous support material from the total volume of the porous support.

The above polymer electrolyte membrane may have a thickness of 5 to 200 ㎛ in an unhumidified state.

A membrane-electrode assembly according to one aspect of the present invention may have an anode catalyst layer and a gas diffusion layer sequentially formed on one side of an electrolyte membrane according to the present invention, and a cathode catalyst layer and a gas diffusion layer sequentially laminated on the other side.

Specifically, the membrane-electrode assembly includes an anode electrode and a cathode electrode positioned opposite each other, and the polymer electrolyte membrane positioned between the anode electrode and the cathode electrode.

FIG. 1 is a cross-sectional view schematically showing a membrane electrode assembly according to one embodiment of the present invention. Referring to FIG. 1, the membrane electrode assembly (100) includes a polymer electrolyte membrane (50) and electrodes (20, 20') for a fuel cell arranged on both sides of the polymer electrolyte 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'), and may further include a microporous layer (not shown) including conductive fine particles such as carbon powder or carbon black between the electrode substrate (40, 40') and the catalyst layer (30, 30') to facilitate material diffusion in the electrode substrate (40, 40').

In the membrane electrode assembly (100), an electrode (20) arranged on one side of a polymer electrolyte membrane (50) and causing an oxidation reaction to generate hydrogen ions and electrons from fuel transferred through an electrode substrate (40) to a catalyst layer (30) is called an anode electrode, and an electrode (20') arranged on the other side of a polymer electrolyte membrane (50) and causing a reduction reaction to generate water from hydrogen ions supplied through the polymer electrolyte membrane (50) and an oxidant transferred through an electrode substrate (40') to a catalyst layer (30') is called a cathode electrode.

The catalyst layers (30, 30') of the anode and cathode electrodes (20, 20') contain a catalyst. Any catalyst that participates in the reaction of the cell and can be used as a catalyst for a fuel cell can be used. Specifically, a platinum-based metal can be preferably used.

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

Specifically, the platinum alloy may be selected from the group consisting of 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, and may be used alone or in combination of two or more thereof.

In addition, the non-platinum alloy may be used alone or in combination of two or more selected from the group consisting of 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.

These catalysts can be used as catalysts themselves or supported on a carrier.

The carrier can be selected from carbon-based carriers, porous inorganic oxides such as zirconia, alumina, titania, silica, and ceria, and zeolites. The above carbon-based carrier may be selected from, but is not limited to, graphite, super P, carbon fiber, carbon sheet, carbon black, Ketjen Black, Denka black, acetylene black, carbon nano tube (CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, carbon nanofiber, carbon nanowire, carbon nanoball, carbon nanohorn, carbon nanocage, carbon nanoring, ordered nano-/meso-porous carbon, carbon aerogel, mesoporous carbon, graphene, stabilized carbon, activated carbon, and combinations of one or more thereof, and any carrier usable in the present technical field may be used without limitation.

The catalyst particles may be positioned on the surface of the carrier, or may penetrate into the carrier by filling the internal pores of the carrier.

When using a precious metal supported on a carrier as a catalyst, a commercially available product can be used, or a precious metal supported on a carrier can be manufactured and used. The process of supporting a precious metal on a carrier is widely known in the art, so a detailed description thereof is omitted in this specification, but it is content that can be easily understood by those working in the art.

The catalyst particles may be contained in an amount of 20 wt% to 80 wt% relative to the total weight of the catalyst electrode (30, 30'). If the amount is less than 20 wt%, there may be a problem of reduced activity, and if the amount is more than 80 wt%, the active area may be reduced due to agglomeration of the catalyst particles, which may conversely reduce the catalytic activity.

In addition, the catalyst electrode (30, 30') may include a binder to improve adhesion and transfer 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 that described above, a repeated description is omitted.

However, the ion conductor can be used in the form of a single substance or a mixture, and can also be optionally used together with a non-conductive compound for the purpose of further improving the adhesion to the polymer electrolyte membrane (50). It is preferable to adjust the amount used to suit the intended use.

As the non-conductive compound, at least one selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene/tetrafluoroethylene (ETFE), ethylene chlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dodecylbenzene sulfonic acid, and sorbitol can be used.

The binder may be included in an amount of 20 wt% to 80 wt% based on the total weight of the catalyst electrode (30, 30'). If the binder content is less than 20 wt%, the generated ions may not be transferred well, and if it exceeds 80 wt%, the pores are insufficient, making it difficult to supply hydrogen or oxygen (air) and reducing the active area for reaction.

As the electrode substrate (40, 40'), a porous conductive substrate can be used so that hydrogen or oxygen can be smoothly supplied. Representative examples thereof include, but are not limited to, carbon paper, carbon cloth, carbon felt, or metal cloth (a porous film composed of a fibrous metal cloth or a cloth formed of polymer fibers in which a metal film is formed on the surface of the cloth). In addition, it is preferable to use an electrode substrate (40, 40') that has been water-repellent treated with a fluorine-based resin, so as to prevent a decrease in reactant diffusion efficiency due to water generated when the fuel cell is operated. As the fluorine-based resin, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene, or a copolymer thereof can be used.

In addition, a microporous layer may be further included to enhance the reactant diffusion effect in the electrode substrate (40, 40'). This microporous layer may generally include a conductive powder having a small particle size, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotube, carbon nanowire, carbon nanohorn, or carbon nano ring.

The microporous layer is manufactured by coating a composition including a conductive powder, a binder resin, and a solvent on the electrode substrate (40, 40'). As the binder resin, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate, or a copolymer thereof can be preferably used. At this time, as the solvent, alcohol such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, or the like can be preferably used. The coating process may be 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 manufacturing method for a conventional fuel cell membrane-electrode assembly, except that the polymer electrolyte membrane (50) according to the present invention is used as the polymer electrolyte membrane (50).

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

Figure 2 is a schematic diagram showing the overall configuration of the fuel cell.

Referring to FIG. 2, a fuel cell (200) includes a fuel supply unit (210) that supplies a mixed fuel in which fuel and water are mixed, a reformer (220) that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack (230) that generates electrical energy by causing an electrochemical reaction between the reformed gas containing hydrogen gas supplied from the reformer (220) and an oxidizer, and an oxidizer supply unit (240) that supplies an oxidizer to the reformer (220) and the stack (230).

The stack (230) has a plurality of unit cells that generate electrical energy by inducing an oxidation/reduction reaction of a reforming gas containing hydrogen gas supplied from a reforming unit (220) and an oxidizing agent supplied from an oxidizing agent supply unit (240).

Each unit cell means a unit cell that generates electricity, and includes the membrane electrode assembly that oxidizes/reduces oxygen in a reforming gas containing hydrogen gas and an oxidizing agent, and a separator (also called a bipolar plate, hereinafter referred to as a 'separator') that supplies the reforming gas containing hydrogen gas and the oxidizing agent to the membrane electrode assembly. The separator is arranged on both sides of the membrane electrode assembly with the membrane electrode assembly at the center. At this time, the separator plates each located at the outermost side of the stack are specifically referred to as end plates.

Among the separators, the end plate is provided with a first supply pipe (231) in the shape of a pipe for injecting a reformed gas containing hydrogen gas supplied from a reforming unit (220), and a second supply pipe (232) in the shape of a pipe for injecting oxygen gas, and the other end plate is provided with a first discharge pipe (233) for discharging a reformed gas containing hydrogen gas that is ultimately unreacted and remaining in a plurality of unit cells to the outside, and a second discharge pipe (234) for discharging an oxidizing agent that is ultimately unreacted and remaining in the unit cells to the outside.

In the fuel cell, except that the membrane-electrode assembly (100) according to one embodiment of the present invention is used, the separator, fuel supply unit, and oxidizer supply unit constituting the electricity generating unit are those used in a typical fuel cell, and therefore a detailed description thereof is omitted herein.

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 various different forms and is not limited to the embodiments described herein.

[Experimental Example 1: Durability Evaluation of Polymer Electrolyte Membrane]

An electrolyte membrane according to the following comparative examples and examples was manufactured using the composition shown in Table 1 below. The electrolyte membrane was manufactured by depositing the composition on a glass substrate, and, except for the type and content of the crosslinking agent, the manufacturing method of a typical fuel cell polymer electrolyte membrane was followed.

Examples 1 to 4 are examples in which the content of the crosslinking agent is different from that of Comparative Example 1, and the type and content of the ion conductor are the same as those of Comparative Example 1.

Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Types of ionic conductors S-PES ¹⁾ S-PES S-PES S-PES S-PES Types of crosslinkers Crosslinker 1 ²⁾ Crosslinker 1 Crosslinker 1 Crosslinker 1 Crosslinking agent content - 5 mol% 10 mol% 15 mol% 20 mol%

1) A polymer electrolyte membrane was prepared by dissolving sulfonated poly(ether sulfone) in dimethylacetamide (DMAc) solvent at 15 wt% and forming a film on a glass substrate.

2) Crosslinking agent 1 used a crosslinking agent represented by the following chemical formula 2.

[Chemical formula 2]

In order to evaluate the durability of the polymer electrolyte membrane, a severe degradation test was performed and the weight change rate of the electrolyte membrane before and after the test was measured, which is shown in Table 2 below.

Accelerated degradation experiments were conducted using the Fenton's test, in which the polymer electrolyte membrane was immersed in a solution containing ₂ ppm FeSO4 in 3 wt% hydrogen peroxide, stirred at 80°C for 100 hours, and the weights before and after the reaction were compared.

Sample name Weight change rate (%) Comparative Example 1 68 Example 1 20 Example 2 16 Example 3 12 Example 4 9.7

Referring to Table 2 above, in the case of Comparative Example 1, the weight change rate was very high at 68%, but in the case of the example of the present invention, the weight change rate was greatly reduced to 20% or less, 9.7%, showing excellent durability. This shows that even if the main chain of the ion conductor polymer is chemically deteriorated in the above-mentioned degradation experiment, the outflow of the deteriorated polymer is minimized due to the crosslinking structure caused by the crosslinking agent of the present invention, resulting in a decrease in the weight change of the polymer electrolyte membrane.

[Experimental Example 2: Evaluation of ionic conductivity of polymer electrolyte membrane (80℃, RH50%)]

For the comparative examples and examples in Table 1 above, the degree of swelling was measured using the following method and is shown in Table 3.

For the polymer electrolyte membranes according to the comparative examples and examples, ionic conductivity was measured at a measurement temperature of 80°C using a measuring device (Solatron-1280Impedance/Gain-Phase analyzer from Solartron). Specifically, ohmic resistance or bulk resistance was measured using the four point probe AC impedance spectroscopic method, and then ionic conductivity was calculated using the following mathematical equation 1.

In the above mathematical expression 1, σ represents ionic conductivity (S/cm), R represents the ohmic resistance (Ω) of the electrolyte membrane, L represents the distance between electrodes (cm), and A represents the area (cm ² ) within the electrolyte through which a constant current flows.

Sample name Conductivity (S/cm) Comparative Example 1 0.023 Example 1 0.025 Example 2 0.027 Example 3 0.026 Example 4 0.028

Referring to Table 3 above, it can be confirmed that the ionic conductivity of Examples 1 to 4 of the present invention is significantly higher than that of Comparative Example 1, and in particular, it can be confirmed that the ionic conductivity of Example 4 shows a value that is 0.005 S/cm higher than that of Comparative Example 1. Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

20, 20': Electrode
30, 30': Catalyst layer
40, 40': Electrode substrate
50: Polymer electrolyte membrane
100: Membrane-electrode assembly
200: Fuel Cell
210: Fuel supply section 220: Reforming section
230: Stack 231: 1st supply pipe
232: Second supply pipe 233: First discharge pipe
234: Second discharge pipe 240: Oxidizer supply section

Claims (10)

In a polymer electrolyte membrane containing a polymer electrolyte material,
The above polymer electrolyte material is,
ionic conductor; and
A polymer electrolyte membrane for a fuel cell, comprising a crosslinking agent represented by the following chemical formula 1:
[Chemical Formula 1]

In the chemical formula 1, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently selected from hydrogen, deuterium, a sulfonic acid group, a carboxyl group, a hydroxyl group, an amine group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryloxy group having 1 to 10 carbon atoms, a and f are integers of 1 to 5, b, c, d and e are integers of 1 to 5, and chemical formula 1 includes two or more amine groups.
In the first paragraph,
The above crosslinking agent comprises a polymer electrolyte membrane for a fuel cell, which comprises a structure represented by the following chemical formula 2:
[Chemical formula 2]

In the first paragraph,
The above ion conductor is a polymer electrolyte membrane for a fuel cell, wherein at least one functional group selected from a carboxyl group and a sulfonic acid group is introduced into a side chain.
In the first paragraph,
A polymer electrolyte membrane for a fuel cell, wherein the ion conductor is a fluorine-based ion conductor, a hydrocarbon-based ion conductor, or a mixture thereof.
In the first paragraph,
A polymer electrolyte membrane for a fuel cell, wherein the cross-linking agent is contained in an amount of 0.05 to 20 wt% based on the total weight of the polymer electrolyte material.
In the first paragraph,
A polymer electrolyte membrane for a fuel cell, further comprising a porous support having a plurality of pores filled with the polymer electrolyte material.
In Article 6,
A polymer electrolyte membrane for a fuel cell, wherein the porous support is an expanded film or a nonwoven fibrous web.
In Article 6,
A polymer electrolyte membrane for a fuel cell, wherein the ratio of the apparent volume of the porous support to the total volume of the polymer electrolyte membrane is 5 to 90%.
A membrane-electrode assembly comprising a polymer electrolyte membrane according to any one of claims 1 to 8.
A fuel cell comprising a membrane electrode assembly of claim 9.