KR102830648B1 - Polymer electrolyte membrane, method for manufacturing the same and electrochemical device comprising the same - Google Patents

Abstract

The present invention relates to a polymer electrolyte membrane including an ion conductor, wherein the polymer electrolyte membrane includes an antioxidant-releasing material.

Description

Polymer electrolyte membrane, method for manufacturing the same and electrochemical device comprising the same {Polymer electrolyte membrane, method for manufacturing the same and electrochemical device comprising the same}

The present invention relates to a polymer electrolyte membrane and an electrochemical device including the same, which comprises an antioxidant-releasing material that releases an antioxidant by a hydrolysis reaction caused by moisture generated during operation of a fuel cell, thereby maintaining an antioxidant effect for a long period of time and preventing performance degradation of a fuel cell.

Fuel cells are cells that directly convert chemical energy generated by fuel oxidation into electrical energy. They are attracting attention as a next-generation energy source due to their high energy efficiency and environmentally friendly characteristics of producing less pollutants.

Fuel cells are generally structured with an anode and a cathode formed on either side of an electrolyte membrane, and this structure is called a membrane electrode assembly (MEA).

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

Representative examples of such polymer electrolyte fuel cells include 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 (H ⁺ ) are transferred to the cathode through the polymer electrolyte membrane, and the generated electrons (e ^- ) are transferred to the cathode through the external circuit. At the cathode, oxygen is supplied, and the oxygen combines with the hydrogen ions (H ⁺ ) and electrons (e ^- ) to generate water through the reduction reaction of oxygen.

Since the polymer electrolyte membrane is a passage through which hydrogen ions (H ⁺ ) generated at the anode are transferred to the cathode, it must have excellent conductivity of hydrogen ions (H ⁺ ). In addition, the polymer electrolyte membrane must have excellent separation ability to separate hydrogen gas supplied to the anode and oxygen supplied to the cathode, and in addition, it must have excellent mechanical strength, dimensional stability, chemical resistance, and other characteristics such as low ohmic loss at high current density.

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 under specific temperature and relative humidity environments, especially under high temperature/low humidity conditions. As a result, polymer electrolyte fuel cells using conventional polymer electrolyte membranes are limited in their scope of use.

Polymer electrolyte membranes have a shortened lifespan due to electrochemical degradation and physical degradation during operation. The main cause of electrochemical degradation is the crossover of hydrogen and oxygen through the polymer electrolyte membrane, generating radicals on the electrode catalyst platinum.

Radicals formed on the electrode catalyst platinum react with the ion conductor of the polymer electrolyte membrane and deteriorate the polymer electrolyte membrane through reactions such as cutting the ion conductor chains.

Meanwhile, during operation of the fuel cell, oxygen is supplied to the reduction electrode, and water is generated by the reduction reaction of oxygen by combining with hydrogen ions (H ⁺ ) and electrons ( ^e- ). Therefore, there is a problem that various additives and other substances added to the polymer electrolyte membrane are easily lost to water or moved by water, resulting in reduced dispersibility.

Accordingly, problems may arise where additives such as antioxidants do not function properly or do not sufficiently exert an antioxidant effect relative to the amount added.

Therefore, there is a need for the development of a technology that can prevent electrochemical deterioration of polymer electrolyte membranes and at the same time maintain the deterioration prevention effect for a long period of time.

(0001) Korean Patent No. 0972525 (2010.07.28) (0002) European Patent No. 2002451 (2014.03.26) (0003) Korean Publication Patent No. 2008-0045421 (May 23, 2008)

The present invention has the effect of preventing deterioration of a polymer electrolyte membrane and improving chemical durability.

The present invention has the effect of maintaining an anti-oxidation effect for a long period of time by gradually releasing an anti-oxidant through a reaction with by-products generated during operation of a fuel cell.

The present invention also has the effect of reducing the amount of additive lost due to moisture generated during fuel cell operation, thereby reducing the manufacturing cost of a polymer electrolyte membrane, and preventing a decrease in fuel cell performance by suppressing an increase in resistance due to the addition of an additive.

According to one aspect of the present invention, a polymer electrolyte membrane including an ion conductor can be provided, wherein the polymer electrolyte membrane includes an antioxidant-releasing material.

The above antioxidant may be at least one selected from the group consisting of salicylic acid, curcumin, folic acid, coumaric acid, caffeic acid, and ferulic acid.

The above antioxidant-releasing material may be one that releases an antioxidant by hydrolysis.

The above antioxidant may be salicylic acid.

The above antioxidant-releasing material may include one selected from the group consisting of an ester group, an acid anhydride group, an amide group, a thioester group, and an ether group.

The above antioxidant releasing material may be salsalate.

The above ion conductor may be at least one selected from the group consisting of a hydrocarbon-based ion conductor, a fluorine-based ion conductor, and an anionic ion conductor.

The polymer electrolyte membrane may include a porous support; and an ion conductor impregnated in the pores of the porous support.

According to another aspect of the present invention, a membrane-electrode assembly including the above-described polymer electrolyte membrane can be provided, the membrane-electrode assembly including an anode electrode and a cathode electrode positioned opposite to each other, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode.

According to another aspect of the present invention, an electrochemical device including the above-described membrane-electrode assembly can be provided.

The polymer electrolyte membrane according to the present invention has an effect of maintaining an anti-oxidation effect for a long period of time.

The polymer electrolyte membrane according to the present invention prevents loss of additives, thereby having an excellent anti-oxidation effect relative to the amount of additives added, while reducing the content of additives relative to the anti-oxidation effect, thereby reducing the manufacturing cost of a fuel cell.

Figure 1 is a vertical cross-sectional view of a polymer electrolyte membrane according to the present invention;
FIG. 2 is a vertical cross-sectional view of a membrane-electrode assembly including a polymer electrolyte membrane according to the present invention;
Figure 3 is a schematic diagram showing the overall configuration of a fuel cell according to one embodiment of the present invention.

Hereinafter, each component of the present invention will be described in more detail so that a person with ordinary skill in the art can easily implement the present invention. However, this is only an example, and the scope of the rights of the present invention is not limited by the following contents.

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.

As used herein, the term "electrochemical device" may include both a power generation device, such as a fuel cell, and an energy storage device, such as a redox flow battery. Preferably, the electrochemical device as used herein may be a fuel cell.

The polymer electrolyte membrane according to the present invention is a polymer electrolyte membrane including an ion conductor, wherein the polymer electrolyte membrane includes an antioxidant-releasing material.

The above antioxidant-releasing substance does not function as an antioxidant by itself, but is a substance that can release a substance that functions as an antioxidant by an additional reaction, for example, by being hydrolyzed by an oxidation reaction.

In particular, the antioxidant-releasing material is characterized by releasing a material that can function as an antioxidant by reacting with moisture or hydrogen ions formed during fuel cell operation.

The above antioxidant-releasing material is not limited to one that does not function as an antioxidant in itself in any form, but can release an antioxidant through an additional reaction.

For example, it may have the form of a material including an antioxidant protecting group, a material that releases an antioxidant by hydrolysis, a core-shell structure having a shell that includes an antioxidant in the core and protects it, or a form in which an antioxidant is supported within a porous structure.

Preferably, it may be a material containing an antioxidant protecting group or a material that releases an antioxidant by hydrolysis reaction.

The above antioxidant can be used without particular limitation as long as it can be used as an antioxidant in the field of fuel cell technology. For example, it can be a substance such as a metal particle, a metal oxide, or an organic acid.

More preferably, the antioxidant may be at least one selected from the group consisting of salicylic acid, curcumin, folic acid, coumaric acid, caffeic acid, and ferulic acid, and most preferably, salicylic acid. The releasable material of the antioxidant may be a material formed by condensation reaction, polymerization, dimerization, or trimerization of salicylic acid, curcumin, folic acid, coumaric acid, caffeic acid, or ferulic acid, and may be a material capable of releasing the antioxidant during operation of the fuel cell. For example, the antioxidant-releasing material may be a salicylic acid dimer, a salicylic acid trimer, a curcumin dimer, a folic acid dimer, a coumarin dimer, a coumarin polymer, a caffeic acid dimer, a caffeic acid trimer, or a ferulic acid dimer, and in particular, may be a material that includes a hydrolyzable group in its molecular structure and can be decomposed into salicylic acid, curcumin, folic acid, coumaric acid, caffeic acid, or ferulic acid by hydrolysis during operation of the electrochemical device.

When the antioxidant is salicylic acid, the antioxidant-releasing material may be composed of a material capable of releasing salicylic acid by hydrolysis.

Salicylic acid is a phenol compound with a substituted carboxyl group, and the name salicylic acid is a common name for 2-hydroxybenzoic acid. It is a substance with strong acidity, and since it contains both a carboxyl group and a hydroxyl group, a condensation reaction is possible at the corresponding functional group.

In particular, the present invention is configured to cause a condensation reaction in at least one of two functional groups of an antioxidant, such as salicylic acid or curcumin, to constitute an antioxidant-releasing material, and to be hydrolyzed by an oxidation reaction during operation of an electrochemical device within a polymer electrolyte membrane to release an organic antioxidant, such as salicylic acid or curcumin, which is an antioxidant.

Accordingly, the antioxidant-releasing material comprises a bond formed by the reaction of a carboxyl group and/or a hydroxyl group, which are condensation-reactive functional groups of salicylic acid.

Specifically, the antioxidant-releasing material may include one selected from the group consisting of an ester group, an acid anhydride group, an amide group, a thioester group, and an ether group.

That is, the antioxidant-releasing material may be composed of a condensation reactant.

Preferably, it may contain an ester group, an acid anhydride group, and most preferably, it may contain an ester group.

The above functional groups can react with water to hydrolyze into compounds containing carboxyl groups and/or hydroxyl groups, thereby releasing antioxidants such as salicylic acid.

The antioxidant-releasing material that releases salicylic acid as an antioxidant may be, for example, salsalate.

Salsalate is a common name for 2-[(2-hydroxyphenyl)carbonyloxy]benzoic acid, which can be formed by the esterification condensation reaction of two molecules of salicylic acid.

Thus, in the case where the antioxidant-releasing material in the present invention is salsalate, two molecules of salicylic acid are released by the hydrolysis reaction, so that an even more excellent antioxidant effect can be achieved. Therefore, in the present invention, the most preferable antioxidant-releasing material may be salsalate.

Meanwhile, as described above, the antioxidant-releasing material can be composed of various forms and is not limited to a material obtained by the reaction of a small number of reactants, such as two molecules of salsalate.

For example, a condensation-reactive functional group can be grafted onto the surface of a large structure such as a porous support to undergo a condensation reaction with an antioxidant to form an antioxidant-releasing material.

The present invention is not limited to the shape, size, etc. of the material, and can be composed of various forms, as long as the material can gradually release an antioxidant due to moisture generated during fuel cell operation.

According to one embodiment of the present invention, the antioxidant-releasing material may be used in an amount of 0.05 to 15 wt%, for example, 0.1 to 10 wt%, 0.2 to 5 wt%, or 0.5 to 4 wt%, based on the total weight of the polymer in the polymer electrolyte membrane. By using the antioxidant-releasing material in the above amount, the effect of antioxidant release can be effectively obtained while maintaining the inherent physical properties of the polymer electrolyte membrane.

The polymer electrolyte membrane of the present invention may be in any form, such as a single membrane formed by casting an ion conductor having ion conductivity into a mold, or a reinforced composite membrane including a composite material manufactured by immersing a porous support in a dispersion liquid in which an ion conductor is dispersed.

The reinforced composite membrane has improved dimensional stability and physical and mechanical properties by including a porous support and an ion conductor filled in the pores of the porous support, and even if the resistance of the polymer electrolyte membrane itself increases somewhat, the performance of the cell is prevented from deteriorating, so the performance and lifespan of the fuel cell itself are maintained excellently.

The porous support constituting the reinforced composite membrane is generally made of a polymer material, such as a perfluorinated polymer sheet containing a large number of pores due to the microstructure of polymer fibrils, or a nanoweb containing nanofibers integrated in the form of a nonwoven fabric containing a large number of pores.

In the present invention, as described above, after grafting in a form capable of releasing an antioxidant onto the surface of a porous support, an antioxidant-releasing material can be formed through a reaction such as a condensation reaction, polymerization, dimerization, or trimerization with the antioxidant.

The above porous support is composed of an aggregate of nanofibers that are three-dimensionally irregularly and discontinuously connected, and thus includes a plurality of uniformly distributed pores. The porous support composed of a plurality of uniformly distributed pores has excellent porosity and characteristics (such as dimensional stability) that can complement the properties of an ion conductor.

The pore diameter, which is the diameter of the pores formed in the porous support, can be formed within a range of 0.05 to 30 ㎛ (micrometers). If the pore diameter is formed to be less than 0.05 ㎛, the ionic conductivity of the polymer electrolyte may decrease, and if the pore diameter exceeds 30 ㎛, the mechanical strength of the polymer electrolyte may decrease.

Additionally, the porosity, which indicates the degree of pore formation of the porous support, can be formed within a range of 50 to 98%.

When the porosity of the above porous support is less than 50%, the ionic conductivity of the polymer electrolyte may decrease, and when the porosity exceeds 98%, the mechanical strength and dimensional stability of the polymer electrolyte may decrease.

The above porosity (%) can be calculated by the ratio of the air volume to the total volume of the porous support, as in the following mathematical expression 1.

[Mathematical Formula 1]

Porosity (%) = (air volume/total volume) χ100

At this time, the total volume of the porous support is calculated by manufacturing a sample of the porous support in a rectangular shape and measuring the width, length, and thickness, and the air volume of the porous support can be obtained by measuring the mass of the porous support sample, then subtracting the polymer volume calculated backwards from the density from the total volume of the porous support.

The average diameter of the nanofibers constituting the porous support may be in the range of 0.005 to 5 μm (micrometers). If the average diameter of the nanofibers is less than 0.005 μm, the mechanical strength of the porous support may be reduced, and if the average diameter of the nanofibers exceeds 5 μm, it may not be easy to control the porosity of the porous support.

The above porous support may be any one selected from the group consisting of nylon, polyimide, polybenzoxazole, polyethylene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene, polyarylene ether sulfone, polyether ether ketone, copolymers thereof, and combinations thereof, but the present invention is not limited thereto.

The porous support may be formed with a thickness of 5 to 30 μm (micrometers). If the thickness of the porous support is less than 5 μm, the mechanical strength and dimensional stability of the polymer electrolyte may deteriorate, and if the thickness of the porous support exceeds 30 μm, the resistance loss of the polymer electrolyte may increase.

The above ion conductors can each independently be cation conductors having cation exchange groups such as protons, or anion conductors having anion exchange groups such as hydroxy ions, carbonates or bicarbonates.

The above cation exchange group may be any one 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, and may generally be a sulfonic acid group or a carboxyl group.

The above cation conductor may include a fluorine-based polymer including the cation exchange group and fluorine in the main chain; a hydrocarbon-based polymer such as benzimidazole, polyamide, polyamideimide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyetherimide, polyester, polyethersulfone, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyarylethersulfone, polyphosphazene or polyphenylquinoxaline; a partially fluorinated polymer such as a polystyrene-graft-ethylenetetrafluoroethylene copolymer or a polystyrene-graft-polytetrafluoroethylene copolymer; and sulfone imide.

More specifically, when the cation conductor is a hydrogen ion cation conductor, the polymers may include a cation exchange group selected from the group consisting of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group and derivatives thereof in the side chain, and specific examples thereof include poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, a defluorinated sulfurized polyether ketone or a fluorinated polymer including a mixture thereof; 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, sulfonated polyether sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone Examples of hydrocarbon polymers include, but are not limited to, polyphenylene sulfone, 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.

The above anion conductor is a polymer capable of transporting anions such as hydroxyl ions, carbonates or bicarbonates. The anion conductor is commercially available in the form of hydroxide or halide (typically chloride), and the anion conductor can be used in industrial water purification, metal separation or catalytic processes.

As the above anion conductor, a polymer doped with metal hydroxide can generally be used, and specifically, poly(ethersulfone), polystyrene, vinyl polymer, poly(vinyl chloride), poly(vinylidene fluoride), poly(tetrafluoroethylene), poly(benzimidazole), or poly(ethylene glycol) doped with metal hydroxide can be used.

Among the above ion conductors, a fluorine-based polymer can be used. The fluorine-based polymer can be, for example, a perfluorosulfonic acid (PFSA)-based polymer or a perfluorocarboxylic acid (PFCA)-based polymer, but is not limited thereto. As the perfluorosulfonic acid-based polymer, Nafion (Dupont Co., Ltd.) can be used, and as the perfluorocarboxylic acid-based polymer, Flemion (Asahi Glass Co., Ltd.) can be used.

The weight average molecular weight of the above ion conductor may be from 240 g/mol to 200,000 g/mol, specifically from 240 g/mol to 100,000 g/mol.

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

However, this is only one example to explain the present invention, and the scope of the rights of the present invention is not limited by the following description.

Figure 1 is a vertical cross-sectional view of a polymer electrolyte membrane according to the present invention.

Referring to FIG. 1, a polymer electrolyte membrane according to one embodiment of the present invention is a vertical cross-section of a porous support (21) including a plurality of pores and a reinforced composite membrane in which an ion conductor (not shown) is impregnated in the pores of the porous support, and may have a structure in which an ion conductor layer (31, 32) is further included on one side and the other side of the porous support impregnated with the ion conductor, respectively.

As described above, the ion conductor layers (31, 32) positioned on one side and the other side of the porous support may be configured to be thin, so that the ion conductor layer positioned on the surface of the porous support is adjacent to the electrode where radicals are formed, in order to configure the porous support to function better as a radical scavenger.

FIG. 2 is a cross-sectional view schematically showing a membrane-electrode assembly including a polymer electrolyte membrane according to the present invention. Referring to FIG. 2, the membrane-electrode assembly (100) includes the polymer electrolyte membrane (50) and electrodes (20, 20') respectively disposed on both sides of the polymer electrolyte membrane (50). 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), the electrode (20) that is arranged on one side of the polymer electrolyte membrane (50) and causes an oxidation reaction to generate hydrogen ions and electrons from the fuel transferred through the electrode substrate (40) to the catalyst layer (30) is called an anode electrode, and the electrode (20') that is arranged on the other side of the polymer electrolyte membrane (50) and causes a reduction reaction to generate water from the hydrogen ions supplied through the polymer electrolyte membrane (50) and the oxidant transferred through the electrode substrate (40') to the catalyst layer (30') is called a cathode electrode.

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. The fluorine-based resin can be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene, or a copolymer thereof.

A fuel cell according to one embodiment of the present invention includes the membrane-electrode assembly, and may be, for example, a fuel cell that uses hydrogen gas as fuel.

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

Referring to the above FIG. 3, the fuel cell (200) includes a fuel supply unit (210) that supplies a mixed fuel in which fuel and water are mixed, a reforming unit (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 reforming unit (220) and an oxidizer, and an oxidizer supply unit (240) that supplies an oxidizer to the reforming unit (220) and the stack (230).

The above 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 the reforming unit (220) and an oxidizing agent supplied from the 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') for supplying the reforming gas containing hydrogen gas and the oxidizing agent to the membrane electrode assembly. The separator is positioned on both sides of the membrane electrode assembly with the membrane electrode assembly at the center. At this time, the separator plates each positioned at the outermost side of the stack are specifically referred to as end plates.

Among the above 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 the 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.

Hereinafter, the present invention will be described in more detail based on examples, but this is only an exemplary description for understanding the present invention, and the scope of the present invention is not limited or restricted to the following examples.

[Manufacturing example]

<Example 1> - Nafion single membrane

Salsalate (in an amount such that the polymer content in the dispersion is 20 wt%) was added to a Nafion D2021 dispersion (20 wt% of the polymer content in the dispersion), and the mixture was formed into a film on a glass substrate to produce a single film having a thickness of 20 μm.

<Example 2> - Hydrocarbon-based ion conductor single film

Sulfonated poly(ether sulfone) (15 wt% SPES) was dissolved in DMAc, and salsalate (in an amount of 2 wt% of the total weight of the polymer in the dispersion) was added to form a film on a glass substrate to produce a single film with a thickness of 20 μm.

<Example 3> - Nafion reinforced composite membrane

A reinforced composite membrane was manufactured in the same manner as in Example 1, except that the PTFE support was impregnated into the dispersion solution in Example 1 to manufacture the membrane.

<Example 4> - Hydrocarbon-based ion conductor reinforced composite membrane

The method of Example 1 was the same as that of Example 2, except that the PPS support was impregnated into the dispersion to form a reinforced composite membrane.

<Comparative Example 1> - Nafion single membrane, compared to Example 1

It was prepared in the same manner as Example 1, except that the same amount of salicylic acid was added to the dispersion instead of salsalate in Example 1.

<Comparative Example 2> - Hydrocarbon-based ion conductor single film, compared to Example 2

It was prepared in the same manner as Example 2, except that the same amount of salicylic acid was added to the dispersion instead of salsalate in Example 2.

<Comparative Example 3> - Nafion reinforced composite membrane, compared to Example 3

A dispersion was prepared in the same manner as in Example 3, except that the same amount of salicylic acid was added to the dispersion instead of salsalate.

<Comparative Example 4> - Hydrocarbon-based ion conductor reinforced composite membrane, compared to Example 4

A dispersion was prepared in the same manner as in Example 4, except that the same amount of salicylic acid was added to the dispersion instead of salsalate.

<Comparative Example 5> - Nafion single membrane, compared to Example 1

It was manufactured in the same manner as in Example 1 above, except that additives such as salsalate were excluded.

<Comparative Example 6> - Hydrocarbon-based ion conductor single film, compared to Example 2

It was manufactured in the same manner as Example 2, except that additives such as salsalate were not used.

<Comparative Example 7> - Nafion reinforced composite membrane, compared to Example 3

It was manufactured in the same manner as Example 3, except that additives such as salsalate were not used.

<Comparative Example 8> - Hydrocarbon-based ion conductor reinforced composite membrane, compared to Example 4

It was manufactured in the same manner as Example 4, except that additives such as salsalate were not used.

[Experimental method]

1) Battery performance evaluation:

A membrane-electrode assembly was manufactured and evaluated by forming a cathode and an anode respectively by the decal transfer method using a Pt/C catalyst and bonding them to a polymer electrolyte membrane. The output performance was evaluated through I-V measurements of the membrane-electrode assembly. Specifically, in order to confirm the output performance under actual fuel cell operating conditions, the membrane-electrode assembly was fastened to a fuel cell unit cell evaluation device and the temperature was maintained at 65°C. Hydrogen (100 % RH) and air (100 % RH) were supplied to the anode and cathode in amounts appropriate for Stoichiometry 1.2/2.0, respectively. The current density was measured at 0.6 V, and a higher value indicates better output performance.

2) Chemical durability evaluation:

The evaluation cell is placed in the OCV state, and the cell voltage is measured at regular time intervals to calculate the decrease rate compared to the initial OCV. The measurement was performed using the Scribner 850 fuel cell test system (evaluated under the conditions of 90℃, 30%RH, and 50kPa). Specifically, the OCV(V)/initial OCV(V) over time (hr) was measured every 24 hours. When this ratio was 0.8 or less, the evaluation was terminated, and the measurement time was used as the standard for durability.

A membrane-electrode assembly was manufactured using the polymer electrolyte membranes of the above examples and comparative examples, and the battery performance evaluation, battery life evaluation, and chemical durability evaluation were performed, as shown in Table 1 below.

Battery performance evaluation (mA/cm ² ) Chemical durability (hr) Example 1 1013 552 Example 2 1028 528 Example 3 1003 576 Example 4 1006 552 Comparative Example 1 1014 504 Comparative Example 2 1027 480 Comparative Example 3 1000 504 Comparative Example 4 1009 504 Comparative Example 5 1007 312 Comparative Example 6 1013 288 Comparative Example 7 997 336 Comparative Example 8 1001 312

Referring to Table 1 above, although they have similar battery performances, they show differences in chemical durability. This is because, while salicylic acid functions as an antioxidant and is consumed, salsalate functions as an antioxidant and then decomposes into salicylic acid, thereby showing an additional function as an antioxidant.

Claims (10)

A polymer electrolyte membrane containing an ion conductor,
The above polymer electrolyte membrane contains an antioxidant-releasing material,
The above antioxidant releasing material comprises one selected from the group consisting of an ester group, an acid anhydride group, an amide group, a thioester group and an ether group,
A polymer electrolyte membrane wherein the antioxidant-releasing material releases an antioxidant by hydrolysis. In the first paragraph,
A polymer electrolyte membrane wherein the antioxidant is at least one selected from the group consisting of salicylic acid, curcumin, folic acid, coumaric acid, caffeic acid, and ferulic acid. delete In the second paragraph,
A polymer electrolyte membrane in which the antioxidant is salicylic acid. delete In the first paragraph,
A polymer electrolyte membrane wherein the antioxidant-releasing substance is salsalate. In paragraph 1,
A polymer electrolyte membrane wherein the ion conductor is at least one selected from the group consisting of a hydrocarbon-based ion conductor, a fluorine-based ion conductor, and an anionic ion conductor. In the first paragraph,
The above polymer electrolyte membrane is,
porous support; and
A polymer electrolyte membrane comprising an ion conductor impregnated in the pores of the porous support. A membrane-electrode assembly comprising a polymer electrolyte membrane according to claim 1,
An anode electrode and a cathode electrode positioned opposite each other, and
A membrane-electrode assembly comprising a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode. An electrochemical device comprising a membrane-electrode assembly according to claim 9.