KR20200027626A - Electrolyte Membrane For Fuel Cell And Method Of Manufacturing The Same - Google Patents

Abstract

The present invention relates to an electrolyte membrane for a fuel cell and a manufacturing method thereof. The electrolyte membrane for a fuel cell comprises: a first ionomer coated layer disposed between an anode layer and a cathode layer facing the anode layer and containing a first ionomer; a porous support layer disposed between the first ionomer coated layer and the cathode layer and including a porous support having a plurality of voids; and a second ionomer coated layer disposed between the porous support layer and the cathode layer, and containing a second ionomer and an antioxidant, wherein the equivalent weight (EW) of the second ionomer can be lower than EW of the first ionomer.

Description

Electrolyte membrane for fuel cell and its manufacturing method {Electrolyte Membrane For Fuel Cell And Method Of Manufacturing The Same}

The present invention relates to an electrolyte membrane for a fuel cell and a method for manufacturing the same, and more particularly, to a fuel cell electrolyte membrane including a plurality of different ionomer coating layers and a method for manufacturing the same.

In the fuel cell, an electrochemical reaction of hydrogen or alcohol and oxygen or air as an oxidant proceeds, and accordingly, chemical energy is converted into electrical energy. The fuel cell includes an anode and a cathode separated by an electrolyte.

In particular, a polymer electrolyte fuel cell is usually composed of an anode, a cathode, and a membrane electrode assembly (MEA) comprising a polymer electrolyte membrane as a proton exchange membrane (PEM) disposed between the anode and the cathode. do. It moves hydrogen ions smoothly and prevents electron flow.

The mobility of hydrogen ions (ie, protons) (H ⁺ ) in the electrolyte membrane in a PEM fuel cell is mainly determined by ion exchange capacity (IEC) or equivalent weight (EW) of ionomers forming the electrolyte membrane. It is determined, and generally requires high proton conductivity and mechanical strength, and low gas permeability and water permeability.

Meanwhile, when the PEM fuel cell is driven, hydrooxyl and hydroperoxyl radicals are formed by reaction of oxygen and hydrogen that penetrate through the electrolyte membrane. However, due to these radicals, the electrolyte membrane is subject to a chemical attack, thereby shortening or destroying its life.

Korean Registered Patent No. 1767267 uses an antioxidant placed in a porous reinforcement located in the center of the electrolyte membrane to prevent chemical degradation of the electrolyte membrane, but is not suitable when considering that chemical degradation starts from the surface of the electrolyte membrane.

Therefore, when considering that the antioxidant moves in the cathode direction due to a potential difference, concentration difference, or water flow during fuel cell operation, when the equivalent amount (EW) of the electrolyte membrane between the cathode and the anode is the same, the antioxidant moves in the cathode direction It is expected that some of the ionomers (e.g., sulfonic acid groups) on the cathode side are combined with antioxidants to reduce the migration of hydrogen ions (Andrew M. Baker et al., Cerium ion mobility and diffusivity rates in perfluorosulfonic acid membranes measured via hydrogen pump operation, journal of the electrochemical society 164 (12) (2017) F1272-F1278). Therefore, it is required to solve the problem of increasing the overall resistance of the electrolyte membrane due to the bottleneck of hydrogen ion migration in the ionomer layer on the cathode side.

Korean Registered Patent No. 1767267

The problem to be solved by the present invention is to provide an electrolyte membrane for a fuel cell having a plurality of ionomer layers.

In addition, an object of the present invention is to provide an electrolyte membrane for a fuel cell in which the ionomer equivalent amount (EW) of the cathode-side ionomer layer is lower than the ionomer equivalent amount (EW) of the anode-side ionomer layer.

In addition, an object of the present invention is to provide an electrolyte membrane having an antioxidant content depending on the difference in the equivalent weight (EW) of the cathode and anode-side ionomer layers.

The object of the present invention is not limited to the object mentioned above. Other specific matters of the present invention are included in the detailed description and drawings.

The electrolyte membrane for a fuel cell according to the present invention for achieving the above object,

A first ionomer coating layer disposed between the anode layer and the cathode layer and the cathode layer, the first ionomer coating layer including a first ionomer; A porous support layer disposed between the first ionomer coating layer and the cathode layer and including a porous support having a plurality of voids; And a second ionomer coating layer disposed between the porous support layer and the cathode layer, and including a second ionomer and an antioxidant.

The equivalent weight of the second ionomer may be lower than the equivalent weight of the first ionomer (EW).

In the porous support layer, the first ionomer may be impregnated into the porous support.

The equivalent of the second ionomer (EW) may be 100 to 500 g / mol lower than the equivalent of the first ionomer (EW).

The equivalent of the first ionomer (EW) may be 700 to 1100 g / mol.

The equivalent of the second ionomer (EW) may be 600 to 1000 g / mol.

The first ionomer coating layer may not include an antioxidant.

The content of the antioxidant for 1 g of the second ionomer may be 0.023 to 0.189 mmol.

The first ionomer, the second ionomer, and the antioxidant may have a relationship of Formula 1 below:

[Equation 1]

(In the above formula, A is the content of the antioxidant per 1 g of the second ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), I ₂ is the equivalent of the second ionomer (g / mol), n is a positive number greater than or equal to 1).

The first ionomer, the second ionomer, and the antioxidant may have a relationship of the following Equation 2:

[Equation 2]

(In the above formula, A is the content of the antioxidant per 1 g of the second ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), and I ₂ is the equivalent of the second ionomer (g / mol)) .

Method of manufacturing an electrolyte membrane for a fuel cell according to the present invention,

Forming a first ionomer coating layer by preparing a dispersion containing the first ionomer; Forming a porous support layer by laminating a porous support on the first ionomer coating layer; And forming a second ionomer coating layer by laminating on the porous support layer by preparing a dispersion containing a second ionomer and an antioxidant, wherein the equivalent amount of the second ionomer (EW) is the equivalent of the first ionomer ( EW).

After the step of forming the second ionomer coating layer, the first ionomer coating layer may be disposed close to the anode layer, and the second ionomer coating layer may further include disposing the cathode layer.

After forming the second ionomer coating layer, the method may further include heat treating the electrolyte membrane.

In the step of forming the porous support layer, the porous ion support may be impregnated with the first ionomer.

The first ionomer coating layer and the second ionomer coating layer may be formed by a method selected from spin coating, bar coating, and slot die coating.

The equivalent of the second ionomer (EW) may be 100 to 500 g / mol lower than the equivalent of the first ionomer (EW).

The first ionomer, the second ionomer, and the antioxidant may have a relationship of the following Equation 2:

[Equation 1]

(In the above formula, A is the content of the antioxidant per 1 g of the second ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), I ₂ is the equivalent of the second ionomer (g / mol), n is a positive number greater than or equal to 1).

The first ionomer, the second ionomer, and the antioxidant may have a relationship of the following Equation 2:

[Equation 2]

(In the above formula, A is the content of the antioxidant per 1 g of the second ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), and I ₂ is the equivalent of the second ionomer (g / mol)) .

The equivalent of the second ionomer (EW) may be 100 to 500 g / mol lower than the equivalent of the first ionomer (EW).

The forming of the first ionomer coating layer may include preparing a dispersion having an equivalent weight (EW) of the first ionomer of 700 to 1100 g / mol.

Preparation of the dispersion containing the second ionomer and an antioxidant, after preparing a dispersion having an equivalent weight (EW) of the second ionomer of 600 to 1000 g / mol, the antioxidant of 0.023 to 1 g of the second ionomer And redispersing by adding 0.189 mmol.

Specific details of other embodiments are included in the detailed description and drawings.

According to the electrolyte membrane for a fuel cell and a method of manufacturing the fuel cell according to some embodiments of the present invention, since the ionomer equivalent amount (EW) of the cathode-side ionomer layer is formed lower than the ionomer equivalent amount (EW) of the anode-side ionomer layer, the cathode-side ionomer layer is formed. Despite the presence of antioxidants, the hydrogen ion (ie, proton) mobility of the cathode and anode side ionomer layers remains the same.

In addition, as the hydrogen ion mobility of the cathode side and anode side ionomer layers is maintained equally, a bottle-neck of hydrogen ion migration occurs even though the antioxidant moves in the anode to cathode direction during fuel cell operation. The increase in resistance of the entire electrolyte membrane is prevented.

The effect of this invention is not limited to the effect mentioned above. It should be understood that the effects of the present invention include all effects that can be deduced from the following description.

1 is a schematic diagram showing the mobility of antioxidants and the mobility of hydrogen ions according to the driving time during operation in a conventional electrolyte membrane for a fuel cell.
2 is a cross-sectional view of an electrolyte membrane for a fuel cell according to an embodiment of the present invention.
3 is a cross-sectional view of an electrolyte membrane for a fuel cell according to an embodiment of the present invention.
Figure 4 is a schematic diagram showing the mobility of hydrogen ions in the fuel cell electrolyte membrane according to an embodiment of the present invention.
5 is a flowchart schematically showing a method of manufacturing an electrolyte membrane for a fuel cell according to an embodiment of the present invention.
6 is a flowchart schematically showing a method of manufacturing an electrolyte membrane for a fuel cell according to another embodiment of the present invention.
7 is a flowchart schematically showing a method of manufacturing an electrolyte membrane for a fuel cell according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be embodied in various different forms, and the present embodiments merely make the disclosure of the present invention complete, and those of ordinary skill in the art to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by those skilled in the art to which the present invention pertains. In addition, terms defined in the commonly used dictionary are not ideally or excessively interpreted unless specifically defined.

In addition, the terminology used herein is for describing the embodiments and is not intended to limit the present invention. In this specification, the singular form also includes the plural form unless otherwise specified in the phrase. As used herein, “comprises” and / or “includes” one or more other components, features, numbers, steps and / or actions other than the components, features, numbers, steps and / or actions mentioned It is used in a sense that does not exclude the presence or addition of an action. And “and / or” includes each and all combinations of one or more of the items mentioned.

In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case "directly above" the other part but also another part in the middle. Conversely, when a portion of a layer, film, region, plate, or the like is said to be “under” another portion, this includes not only the case “underneath” the other portion but also another portion in the middle.

Unless otherwise specified, all numbers, values, and / or expressions expressing the amounts of ingredients, reaction conditions, polymer compositions and formulations used herein are those numbers that occur in obtaining these values, among other things. As these are approximations that reflect the various uncertainties of the measurement, it should be understood that in all cases they are modified by the term "about". In addition, when numerical ranges are disclosed in this description, these ranges are continuous, and include all values from the minimum value in this range to the maximum value including the maximum value, unless otherwise indicated. Further, when such a range refers to an integer, all integers including the minimum value to the maximum value including the maximum value are included unless otherwise indicated.

In the present specification, when a range is described for a variable, it will be understood that the variable includes all values within the described range including the described endpoints of the range. For example, a range of “5 to 10” includes values of 5, 6, 7, 8, 9, and 10, as well as any subrange of 6 to 10, 7 to 10, 6 to 9, 7 to 9, and the like. It will be understood to include, and include any value between integers pertinent to the stated range of ranges such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9, and the like. Also, for example, the range of “10% to 30%” is 10% to 15%, 12% to 10%, 11%, 12%, 13%, etc., and all integers including up to 30%. It will be understood that it includes any subranges such as 18%, 20% to 30%, etc., and also includes any value between valid integers within the scope of the stated range, such as 10.5%, 15.5%, 25.5%, and the like.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a schematic view showing a conventional electrolyte membrane for a fuel cell. 2 to 4 are cross-sectional views of an electrolyte membrane for a fuel cell according to an embodiment of the present invention.

First, referring to FIG. 1, since the conventional electrolyte membrane for fuel cell 100 'has the same ionomer equivalent weight (EW) and uniform antioxidant 105 distribution, the antioxidant 105 according to the driving time during fuel cell operation Is moved from the anode 210 to the cathode 220. The movement of the antioxidant 105 may be derived from a potential difference, a concentration difference, or a water flow according to driving. Accordingly, the concentration of the antioxidant 105 is increased in the electrolyte membrane 100 ′ of the cathode 220 side than the anode 210 according to the driving time, and as a result, the antioxidant 105 is generally an ionomer (for example, , And a sulfonic acid group (ionomer containing -SO ₃ ). As a result, as shown in FIG. 1, the movement of hydrogen ions may be reduced according to the combination of the ionomer and the antioxidant 105, and the resistance of the electrolyte membrane according to the bottle-neck of the hydrogen ion movement (ie, Ion resistance).

Subsequently, referring to FIG. 2, the electrolyte membrane 100 for a fuel cell according to the present invention includes a first ionomer coating layer 110 including a first ionomer, a second ionomer coating layer 120 including a second ionomer and an antioxidant. , And a porous support layer 115 having a porous support in which a plurality of pores are formed. In particular, the porous support layer 115 in the present invention may be disposed between the first ionomer coating layer 110 and the second ionomer coating layer 120. Meanwhile, in the present invention, the first and second ionomers may be, for example, ionomers containing sulfonic acid groups (SO ₃ ⁻ ), but are not limited thereto. In addition, the antioxidant in the present invention may be, for example, cerium-based ions (for example, Ce ³⁺ or Ce ⁴⁺ ), but is not limited thereto.

On the other hand, the pores of the porous support layer 115 may include a first ionomer filled. For example, the first ionomer may be included in the porous support impregnation, but is not limited thereto.

Subsequently, referring to FIG. 3 in more detail, the electrolyte membrane 100 for a fuel cell of the present invention includes a first ionomer coating layer disposed between the anode layer 210 and the anode layer 210 and the opposite cathode layer 220. (110); A porous support layer 115 disposed between the first ionomer coating layer 110 and the cathode layer 220; And a second ionomer coating layer 120 disposed between the porous support layer 115 and the cathode layer 220.

In particular, in the electrolyte membrane 100 of the present invention, the equivalent weight (EW) of the second ionomer of the second ionomer coating layer 120 is lower than the equivalent weight (EW) of the first ionomer of the first ionomer coating layer 110. You can. Preferably, in the present invention, the equivalent of the second ionomer (EW) may be 100 to 500 g / mol lower than the equivalent of the first ionomer (EW). For example, when the first and second ionomers are ionomers containing a sulfonic acid group (SO ₃ ⁻ ), the equivalent of the ionomer (EW) may be an index indicating the number of sulfonic acid groups (SO ₃ ⁻ ). Therefore, the second ionomer having a lower equivalent weight (EW) than the first ionomer may have a larger number of sulfonic acid groups (SO ₃ ⁻ ).

The equivalent of the first ionomer (EW) in the electrolyte membrane 100 for a fuel cell according to the present invention may be, for example, 700 to 1100 g / mol. In addition, the equivalent (EW) of the second ionomer may be 600 to 1000 g / mol, but is not limited thereto. That is, the second ionomer coating layer 120 may use a second ionomer having an equivalent weight (EW) lower than 600.

On the other hand, in order to secure uniform hydrogen ion conductivity of the first and second ionomer coating layers 120 despite driving time during operation (that is, to prevent the resistance of the electrolyte membrane 100 (ie, ion resistance) from increasing) ), The appropriate content of the antioxidant in the fuel cell electrolyte membrane 100 according to the present invention can be derived by using the equivalent of the first ionomer and the second ionomer (EW). More specifically, in the present invention, the content of the first ionomer, the second ionomer, and the antioxidant may have a relationship of Equation 1 below.

[Equation 1]

In the above formula 1, A is the content of the antioxidant per 1 g of ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), I ₂ is the equivalent of the second ionomer (g / mol), n Is a positive number greater than or equal to 1.

Preferably, in Formula 1 of the present invention, n is 4, and may have a relationship of Formula 2 below.

[Equation 2]

On the other hand, as described above, the equivalent of the first ionomer and the second ionomer (EW) preferred in the present invention may be 700 to 1100 g / mol and 600 to 1000 g / mol, respectively, and the equivalent of the second ionomer (EW) Since it may be 100 to 500 g / mol lower than the equivalent (EW) of the first ionomer, the antioxidant in the second ionomer coating layer 120 of the present invention is 0.023 to 0.189 mmol of 1 g of ionomer (particularly, second ionomer). Content.

On the other hand, the first ionomer coating layer 110 in the electrolyte membrane 100 for a fuel cell according to the present invention may include less antioxidant than the second ionomer coating layer 120, or preferably not include an antioxidant. That is, since the chemical deterioration of the electrolyte membrane 100 of the fuel cell during operation occurs more in the region closer to the cathode layer 220 than the anode layer 210, the second ionomer coating layer 120 contains more antioxidants, Preferably, it may be included only in the second ionomer coating layer 120.

Subsequently, referring to FIG. 4, the electrolyte membrane 100 for a fuel cell according to the present invention may have improved mobility of hydrogen ions compared to a conventional electrolyte membrane (see FIG. 1).

As described above, in the present invention, the first ionomer coating layer 110 is disposed on the anode layer 210, the second ionomer coating layer 120 is disposed close to the cathode layer 220, and the second ionomer equivalent weight (EW) is It is formed lower than 1 ionomer equivalent (EW) (i.e., when the first and second ionomers are ionomers containing sulfonic acid groups (SO ₃ ⁻ ), the sulfonic acid groups of the second ionomers (SO ₃ ⁻ ) the so than many), an antioxidant, which is located in the second ionomer coating layer 120 according to the running time when operating a sulfonic acid group (sO ₃ of the second ionomer ^- even though combined with), and the first and second ionomer coating ( At 110, 120), the mobility of hydrogen ions (ie, proton conductivity) can be maintained equal or similar. Therefore, although the antioxidant 105 moves in the direction of the cathode layer 220 during fuel cell operation, unlike the conventional electrolyte membrane (see FIG. 1), a bottleneck of hydrogen ion migration is not generated. Therefore, the electrolyte membrane 100 for a fuel cell of the present invention is prevented from increasing the ion resistance as a whole.

On the other hand, as described above, in order to secure the equivalent hydrogen ion mobility of the first and second ionomer coating layers 110 and 120, the preferred content of the antioxidant 105 depends on the equivalent weight of the first and second ionomers (EW) Relationship (see equation 1 or equation 2).

Hereinafter, a method of manufacturing an electrolyte membrane for a fuel cell according to some embodiments of the present invention will be described with reference to flowcharts of FIGS. 5 to 7. For convenience of description, differences from those described with reference to FIGS. 1 to 4 will be mainly described.

First, referring to FIG. 5, a method of manufacturing an electrolyte membrane for a fuel cell (see 100 in FIG. 4) according to the present invention includes a first ionomer coating layer (see 110 in FIG. 4) and a second ionomer coating layer (see 120 in FIG. 4). And forming an electrolyte membrane 100 including a porous support layer (see 115 of FIG. 4) (S100); And the first ionomer coating layer 110 is disposed close to the anode layer (see 210 in FIG. 4), and the second ionomer coating layer 120 is disposed close to the cathode layer (see 220 in FIG. 4) (S200). can do.

Subsequently, referring to FIG. 6, the step of forming the electrolyte membrane 100 for a fuel cell (S100) is specifically, a step of forming a first ionomer coating layer (S110); Forming a porous support layer 115 (S115); And forming a second ionomer coating layer (S120).

Referring to FIG. 7, the step of forming the electrolyte membrane 100 for a fuel cell (S100) is more specifically, preparing a dispersion containing the first ionomer (S111) and coating the first ionomer coating layer 110 ( S113); Forming a porous support layer 115 by laminating a porous support on the first ionomer coating layer 110 (S115); And preparing a dispersion comprising a second ionomer and an antioxidant (see 105 in FIG. 4) (S121), coating the second ionomer coating layer 120 by laminating on the porous support layer 115 (S123). can do. At this time, as described above, in the present invention, the equivalent of the second ionomer (EW) may be lower than the equivalent of the first ionomer (EW). Preferably, the equivalent of the second ionomer (EW) may be, for example, 100 to 500 g / mol lower than the equivalent of the first ionomer (EW), but is not limited thereto.

In addition, in the present invention, the preparation of the dispersion containing the second ionomer and the antioxidant 105 (S121) includes first preparing the dispersion of the second ionomer and then adding the antioxidant 105 to redisperse it. can do.

On the other hand, as described above, the equivalent of the first ionomer (EW) to prepare a dispersion to be 700 to 1100 g / mol (S111), the equivalent of the second ionomer (EW) is a dispersion to be 600 to 1000 g / mol It can be manufactured (S121). In particular, according to Formula 2 described above in the present invention, a dispersion may be prepared by adding and redispersing 0.023 to 0.189 mmol of the antioxidant (105) with respect to 1 g of the second ionomer to the dispersion of the second ionomer (S121). Therefore, when using a cerium ion (for example, Ce ³⁺ or Ce ⁴⁺ ) having a molar mass of 140,000 mg / mol as the antioxidant 105, preferably 3.2 to 1 per ionomer (ie, second ionomer) 26.5mg can be added.

Meanwhile, the steps of coating the first and second ionomer coating layers (S113 and S123) may be formed by a method selected from spin coating, bar coating, and slot die coating, but are not limited thereto.

In addition, in the steps of coating the first and second ionomer coating layers (S113 and S123), a process of drying after coating each prepared dispersion may be further performed. In the case of such a drying process, it may be dried at a temperature and time depending on the solution used in preparing the ionomer dispersion (S111, S121). For example, when used as a solution containing a solvent selected from the group consisting of propanol, isopropanol, ethanol, and combinations thereof, preferably at 80 to 100 ° C. for about 1 hour While drying.

In addition, the manufacturing method of the electrolyte membrane 100 for a fuel cell according to the present invention, preferably after the step of forming the second ionomer coating layer 120 (S120), may further include the step of heat-treating the electrolyte membrane 100 have. Through this heat treatment process, residual solvents contained in the ionomer coating layers 110 and 120 may be sufficiently removed, and bonding between the ionomer coating layers 110 and 120 and the porous support layer 115 may be strengthened. In addition, in the case of the electrolyte membrane 100 in which an ion conductive polymer is used, sufficient heat curing may be achieved through a heat treatment process.

Such a heat treatment process can be heated at a temperature and time depending on the properties of the ionomer used. For example, when using the first and second ionomers containing sulfonic acid groups (SO ₃ ⁻ ), heating may be preferably performed at 140 to 200 ° C. for 3 to 60 minutes. More preferably, heating may be performed at 140 to 200 ° C. for 3 to 10 minutes.

In addition, the step (S115) of forming the porous support layer 115 in the method of manufacturing the electrolyte membrane 100 according to the present invention is such that the first ionomer is porous, such that the first ionomer is filled in the pores of the porous support. And impregnating on the support. For example, the first ionomer of the already formed first ionomer coating layer 110 is subjected to physical pressure to allow it to permeate the porous support well, or by stacking the porous support on the first ionomer coating layer 110 for a certain period of time to remove the first ionomer. 1 The ionomer can be filled into a porous support. Particularly, when the first ionomer is first filled in the porous support layer 115, the second ionomer and the antioxidant 105 derived from the second ionomer coating layer 120 are relatively less filled in the porous support layer 115. Can be.

Meanwhile, in the electrolyte membrane 100 for a fuel cell of the present invention, the first and second ionomer coating layers 110 and 120 may have a thickness of, for example, 10 to 100 μm, but are not limited thereto. That is, the thickness of the first and second ionomer coating layers 110 and 120 may vary depending on the thickness of the electrolyte membrane 100 to be manufactured.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are for illustrative purposes only, and the scope of the present invention is not limited to these examples. In addition, Table 1 shows the equivalents (EW) and ion exchange capacity (IEC) of the first and second ionomers used and the appropriate antioxidant content.

Example 1

Preparation of electrolyte membrane for fuel cells

A first ionomer dispersion having a sulfonic acid group (-SO ₃ ) and an equivalent weight (EW) of 700 g / mol was prepared. The prepared first ionomer dispersion was coated with a thickness of 10 to 100 μm on the top of the glass plate (preparation of the first ionomer coating layer). At this time, the coating method was selected from spin coating, casting using a doctor blade, bar coating, and slot die coating.

A porous support having a plurality of pores was laminated on the coated first ionomer coating layer (preparation of porous support layer). At this time, physical pressure was applied to allow the already coated first ionomer dispersion to permeate well (or may be left for a certain period of time). Then, it was dried at 80 to 100 ° C. for 1 hour.

After preparing a second ionomer dispersion having a sulfonic acid group (-SO ₃ ) and having an equivalent weight (EW) of 600 g / mol, cerium (Ce) as an antioxidant in the second ionomer dispersion is ionomer (i.e., a second Ionomer) 8.33 mg per 1 g was added and redispersed. The redispersion solution thus prepared was coated on the first ionomer coating layer to a thickness of 10 to 100 μm (preparation of the second ionomer coating layer). At this time, as for the coating method, one of spin coating, casting using a doctor blade, bar coating, and slot die coating was selected as in the first ionomer coating layer. Then, it was dried at 80 to 100 ° C. for 1 hour.

Then, sequentially, the first ionomer coating layer, the porous support layer, and the second ionomer coating layer were laminated, and the prepared electrolyte membrane was heat treated at 140 to 200 ° C. for 3 to 10 minutes.

Among the prepared electrolyte membranes, the first ionomer coating layer having a high equivalent weight (EW) and having no antioxidant is positioned to face the anode layer, and conversely, the second ionomer coating layer having a low equivalent weight (EW) and an antioxidant exists in the cathode layer. Positioned to face each other.

Examples 2 to 15

In Example 1, except for using the first ionomer equivalent weight (EW), the second ionomer equivalent weight (EW), and the contents of the antioxidants in numerical values shown in Table 1, an electrolyte membrane for a fuel cell was prepared in the same manner as in Example 1. Did.

Ionomer EW
(I)
[g / mol] Ionomer IEC
(i = 1000 / I)
[mmol / g] IEC difference values of the 1st and 2nd ionomer coating layer
(Difference in mmol number of sulfonic acid groups)
(C = i ₂ -i ₁ )
[mmol / g] Optimum amount of antioxidant
(D = C / 4)
[mmol / g] Cerium antioxidant amount
(E = D × molar mass)
[mg / g-ionomer] Second ionomer
Coating layer
(I ₂ ) First ionomer
Coating layer
(I ₁ ) Second ionomer
Coating layer
(i ₂ ) 1st ionomer
Coating layer
(i ₁ ) Example 1 600 700 1.67 1.43 0.238 0.060 8.33 Example 2 800 1.25 0.417 0.104 14.58 Example 3 900 1.11 0.556 0.139 19.44 Example 4 1000 1.00 0.667 0.167 23.33 Example 5 1100 0.91 0.758 0.189 26.52 Example 6 700 800 1.43 1.25 0.179 0.045 6.25 Example 7 900 1.11 0.317 0.079 11.11 Example 8 1000 1.00 0.429 0.107 15.00 Example 9 1100 0.91 0.519 0.130 18.18 Example 10 800 900 1.25 1.11 0.139 0.035 4.86 Example 11 1000 1.00 0.250 0.063 8.75 Example 12 1100 0.91 0.341 0.085 11.93 Example 13 900 1000 1.11 1.00 0.111 0.028 3.89 Example 14 1100 0.91 0.202 0.051 7.07 Example 15 1000 1100 1.00 0.91 0.091 0.023 3.18 * As cerium-based antioxidant, cerium (Ce) with a molar mass of 140 mg / mmol is used.

Evaluation example

In Table 1, when the first and second ionomer equivalents (EW) of each example and the calculated antioxidant content were used, the highest hydrogen ion (ie, proton) conductivity in the electrolyte membrane was observed, and the oxidation described in Table 1 It was observed that the farther from the content of the inhibitor, the lower the hydrogen ion conductivity of the electrolyte membrane. That is, when the first and second ionomer equivalents (EW) of the numerical values given in Table 1 and the calculated antioxidant content are used, the hydrogen ion conductivity of the first and second ionomer coating layers in the electrolyte membrane is almost the same. It can be seen that the resistance value of the electrolyte membrane is the lowest.

Through this, the second while being ionomer and an antioxidant where the coating chemical degradation prevention agents, antioxidants, and the sulfonic acid groups of the second ionomer (SO ₃ ^-) that are placed close to the cathode layer despite the coupling, and disposed close to the anode layer the so one ionomer coating layer than low ionomer equivalent weight (EW) is (i.e., the second sulfonic acid group (sO ₃ of the ionomer coating ^- since there will be times more)), as a result, the first and second mobility of the hydrogen ions in the ionomer coating layer It was found that (ie, proton conductivity) remained equal or similar. Therefore, despite the fact that the antioxidant moves in the direction of the cathode layer 220 during operation, a bottle-neck of hydrogen ion movement is not generated, thereby increasing the ion resistance of the electrolyte membrane 100. Able to know.

In the above, although the preferred embodiments of the present invention have been illustrated and described, the present invention is not limited to the specific embodiments described above, and the technical field to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical idea or prospect of the present invention.

100: electrolyte membrane 100 ': conventional electrolyte membrane
105: antioxidant 110: first ionomer coating layer
115: porous support layer 120: second ionomer coating layer
210: anode, anode layer 220: cathode, cathode layer

Claims (20)

A first ionomer coating layer disposed between the anode layer and the cathode layer and the cathode layer, the first ionomer coating layer including a first ionomer;
A porous support layer disposed between the first ionomer coating layer and the cathode layer and including a porous support having a plurality of voids; And
It is disposed between the porous support layer and the cathode layer, and includes a second ionomer coating layer comprising a second ionomer and an antioxidant,
The electrolyte membrane for a fuel cell in which the equivalent weight of the second ionomer is lower than the equivalent weight of the first ionomer (EW). According to claim 1,
The porous support layer is an electrolyte membrane for a fuel cell in which the first ionomer is impregnated into the porous support. According to claim 1,
The electrolyte membrane for a fuel cell in which the equivalent weight (EW) of the second ionomer is 100 to 500 g / mol lower than the equivalent weight (EW) of the first ionomer. According to claim 1,
The equivalent of the first ionomer (EW) is 700 to 1100 g / mol of electrolyte membrane for fuel cells. According to claim 1,
The equivalent of the second ionomer (EW) is an electrolyte membrane for a fuel cell of 600 to 1000 g / mol. According to claim 1,
The first ionomer coating layer is an electrolyte membrane for a fuel cell that does not contain an antioxidant. According to claim 1,
The electrolyte membrane for a fuel cell having a content of the antioxidant of 0.023 to 0.189 mmol per 1 g of the second ionomer. According to claim 1,
The first ionomer, the second ionomer, and the antioxidant electrolyte membrane for a fuel cell having a relationship of the following formula 1:
[Equation 1]

(In the above formula, A is the content of the antioxidant per 1 g of the second ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), I ₂ is the equivalent of the second ionomer (g / mol), n is a positive number greater than or equal to 1). According to claim 1,
The first ionomer, the second ionomer and the antioxidant electrolyte membrane for a fuel cell having a relationship of the following formula (2):
[Equation 2]

(In the above formula, A is the content of the antioxidant per 1 g of the second ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), and I ₂ is the equivalent of the second ionomer (g / mol)) . Forming a first ionomer coating layer by preparing a dispersion containing the first ionomer;
Forming a porous support layer by laminating a porous support on the first ionomer coating layer; And
Comprising the steps of forming a second ionomer coating layer by preparing a dispersion containing a second ionomer and antioxidant and stacking on the porous support layer,
A method of manufacturing an electrolyte membrane for a fuel cell, wherein the equivalent of the second ionomer (EW) is lower than the equivalent of the first ionomer (EW). The method of claim 10,
After the step of forming the second ionomer coating layer,
The first ionomer coating layer is disposed close to the anode layer, and the second ionomer coating layer is disposed closer to the cathode layer. The method of claim 10,
After the step of forming the second ionomer coating layer,
Method of manufacturing an electrolyte membrane for a fuel cell further comprising the step of heat-treating the electrolyte membrane. The method of claim 10,
The step of forming the porous support layer,
A method of manufacturing an electrolyte membrane for a fuel cell to impregnate the porous support with the first ionomer. The method of claim 10,
The first ionomer coating layer and the second ionomer coating layer,
Method of manufacturing an electrolyte membrane for a fuel cell formed by a method selected from spin coating, bar coating, and slot die coating. The method of claim 10,
A method of manufacturing an electrolyte membrane for a fuel cell in which the equivalent weight (EW) of the second ionomer is 100 to 500 g / mol lower than the equivalent weight (EW) of the first ionomer. The method of claim 10,
The first ionomer, the second ionomer and the antioxidant is a method of manufacturing an electrolyte membrane for a fuel cell having the relationship of the following formula (1):
[Equation 1]

(In the above formula, A is the content of the antioxidant per 1 g of the second ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), I ₂ is the equivalent of the second ionomer (g / mol), n is a positive number greater than or equal to 1). The method of claim 10,
The first ionomer, the second ionomer and the antioxidant is a method of manufacturing an electrolyte membrane for a fuel cell having a relationship of the following formula (2):
[Equation 2]

(In the above formula, A is the content of the antioxidant per 1 g of the second ionomer (mol), I ₁ is the equivalent of the first ionomer (g / mol), and I ₂ is the equivalent of the second ionomer (g / mol)) . The method of claim 10,
A method of manufacturing an electrolyte membrane for a fuel cell in which the equivalent weight (EW) of the second ionomer is 100 to 500 g / mol lower than the equivalent weight (EW) of the first ionomer. The method of claim 10,
Forming the first ionomer coating layer,
A method for producing an electrolyte membrane for a fuel cell, comprising the step of preparing a dispersion in which the equivalent (EW) of the first ionomer is 700 to 1100 g / mol. The method of claim 10,
Preparation of the dispersion containing the second ionomer and antioxidant,
After preparing a dispersion in which the equivalent of the second ionomer (EW) is 600 to 1000 g / mol, adding the antioxidant to 0.023 to 0.189 mmol to 1 g of the second ionomer and redispersing the electrolyte for a fuel cell, Method of manufacturing a membrane.

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