KR101542194B1 - Membrane and electrode assembly for fuel cell manufacturing method and fuel cell using the same - Google Patents

Abstract

A membrane electrode assembly for a fuel cell, a method of manufacturing the same, and a fuel cell including the same. A method of manufacturing a membrane electrode assembly for a fuel cell includes the steps of: (a) forming a first electrode catalyst layer on a first support film; coating an ion conductive material on the first electrode catalyst layer to form a first ion conductive film layer; (B) forming a second ionic conductive coating layer on the second electrode catalyst layer by coating the ionic conductive material on the second electrode catalyst layer, thereby forming a second transfer film And (c) placing the first ion conductive film layer of the first transfer film and the second ion conductive film layer of the second transfer film adjacent to one side and the other side of the electrolyte membrane, respectively, And transferring the second transfer film onto one surface and the other surface of the electrolyte membrane simultaneously or sequentially.

Accordingly, the disclosed membrane electrode assembly, the method of manufacturing the same, and the fuel cell including the membrane electrode assembly reduce the interfacial resistance between the membrane and the electrode and increase the porosity in the electrode catalyst layer, facilitating mass transfer.

Description

[0001] The present invention relates to a membrane electrode assembly for a fuel cell, a method of manufacturing the membrane electrode assembly, and a fuel cell including the membrane electrode assembly,

The present invention relates to a membrane electrode assembly for a fuel cell, a method of manufacturing the same, and a fuel cell including the membrane electrode assembly. More particularly, the present invention provides an ion conductive membrane layer between an electrolyte membrane and an electrode catalyst layer to reduce the interface resistance between the electrolyte membrane and the electrode catalyst layer The present invention relates to a membrane electrode assembly for a fuel cell capable of securing a porosity in an electrode catalyst layer through a post-treatment process after manufacturing a membrane electrode assembly, a method for manufacturing the membrane electrode assembly, and a fuel cell including the membrane electrode assembly.

A fuel cell is a power generation system that converts the energy of a fuel into electrical energy by chemical reaction. Polymer electrolyte fuel cells obtain electrical energy through a chemical reaction that produces water from hydrogen and oxygen. Since such energy conversion is performed in the membrane electrode assembly described later, the membrane electrode assembly is a key component that determines the performance of the fuel cell.

As shown in Fig. 1, the stacked internal structure of the polymer electrolyte fuel cell is composed of a membrane electrode 12 composed of a electrolytic membrane 12 and a pair of electrode catalyst layers 11 and 11 'disposed on both sides of the electrolyte membrane 12 (10).

A pair of gas diffusion layers (GDL) are disposed on both sides of the membrane electrode assembly 10 so as to support the membrane electrode assembly 10, and a gas diffusion layer A pair of separators having a flow field for delivering fuel and air and discharging the generated water are disposed. Therefore, the unit cell comprises a single membrane electrode assembly, two gas diffusion layers, and two separators, and the unit cells are stacked to form a stacked cell.

The membrane electrode assembly can be prepared by two methods, a catalyst coated membrane (CCM) and a catalyst coated GDL (CCG).

In the CCM method, first, a decal film is produced using a transfer paper, and then the transfer film is thermally compressed with the electrolyte membrane to form a membrane electrode assembly. Separately, a gas having fine pores formed on the support layer A diffusion layer is formed, and then the membrane electrode unit and the gas diffusion layer unit are aligned to form a cell.

The method of catalyst-coated gas diffusion layer (CCG) is a method in which a gas diffusion layer having microvoids formed on a support such as carbon paper is formed and an electrode catalyst layer is formed on the gas diffusion layer to prepare a gas diffusion layer- - A method of constructing a cell by thermocompression bonding an electrolyte membrane between electrode unit bodies.

In a polymer electrolyte fuel cell using hydrogen and air as its main fuel, the catalyst coating method is advantageous in that the interface resistance between the electrolyte membrane and the electrode catalyst layer is lower and the thinner electrode catalyst layer is formed than the catalyst coating gas diffusion layer method, (Journal of Power Sources. 170 (2007), 140).

However, both of the above two methods have a disadvantage in that the bonding state between the electrolyte membrane and the electrode catalyst layer is poor because the bonding process (i.e., the transfer process) is performed under high temperature and high pressure conditions, and voids in the electrode catalyst layer are broken The performance of the membrane electrode assembly is deteriorated.

An object of the present invention is to provide a membrane electrode assembly for a fuel cell capable of reducing the interfacial resistance between an electrolyte membrane and an electrode catalyst layer, and a method for manufacturing the same.

Another object of the present invention is to provide a membrane electrode assembly for a fuel cell capable of improving porosity in an electrode catalyst layer and a method of manufacturing the same.

It is still another object of the present invention to provide a fuel cell having improved cell voltage by including the membrane electrode assembly.

According to an aspect of the present invention,

An electrolyte membrane;

A pair of electrode catalyst layers disposed on both surfaces of the electrolyte membrane; And

And an ion conductive film layer disposed between the electrolyte membrane and each of the electrode catalyst layers.

According to another aspect of the present invention,

(a) fabricating a first transfer film by forming a first electrode catalyst layer on a first support film, and coating a first electrode catalyst layer with an ion conductive material to form a first ion conductive film layer;

(b) fabricating a second transfer film by forming a second electrode catalyst layer on the second support film, and coating the ionic conductive material on the second electrode catalyst layer to form a second ion conductive film layer; And

(c) arranging the first ion conductive film layer of the first transfer film and the second ion conductive film layer of the second transfer film so as to be adjacent to one surface and the other surface of the electrolyte membrane, respectively, And simultaneously transferring the electrolyte membrane on one side and the other side of the electrolyte membrane, respectively.

According to an embodiment of the present invention, the transfer of the first transfer film and the second transfer film is performed by a thermal compression method or a roll-to-roll method.

According to another embodiment of the present invention, the manufacturing method of the membrane electrode assembly for a fuel cell further comprises removing the first support film and the second support film from the first transfer film and the second transfer film, respectively.

According to another embodiment of the present invention, the manufacturing method of the membrane electrode assembly for a fuel cell further includes a step of expanding the voids of the first electrode catalyst layer and the second electrode catalyst layer after the step (c).

According to another embodiment of the present invention, the step of expanding the pores of the first electrode catalyst layer and the second electrode catalyst layer includes an acid treatment, washing and drying.

According to another embodiment of the present invention, the ion conductive film layer is formed of a perfluoro proton conductive polymer film, a sulfonated polysulfone copolymer, a sulfonated poly (ether-ketone) based polymer, a perfluorinated sulfonic acid polymer containing polymer, At least one ion-conducting polymer selected from the group consisting of a polyether ether ketone-based polymer, a polyetheretherketone-based polymer, a polyimide-based polymer, a polystyrene-based polymer, a polysulfone-based polymer, and a clay-sulfonated polysulfone nanocomposite .

According to another embodiment of the present invention, the thickness of the ion conductive film layer is 1 to 5 mu m.

According to another aspect of the present invention,

A fuel cell including the membrane electrode assembly according to any one of the above embodiments is provided.

According to the present invention, it is possible to provide a membrane electrode assembly for a fuel cell capable of reducing the interfacial resistance between the electrolyte membrane and the electrode catalyst layer, and a method of manufacturing the same.

According to the present invention, a membrane electrode assembly for a fuel cell capable of improving the porosity in the electrode catalyst layer and a method of manufacturing the same are provided.

According to the present invention, a fuel cell having improved cell voltage can be provided by including the membrane electrode assembly.

Hereinafter, a membrane electrode assembly for a fuel cell and a method of manufacturing the same according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 2, the membrane electrode assembly 100 for a fuel cell according to the present embodiment includes an electrolyte membrane 101, electrode catalyst layers 102 and 102 ', and ion conductive films 103 and 103'.

The electrolyte membrane 101 may be a perfluoro proton conducting polymer membrane represented by Nafion (Du Pont), a hydrocarbon-based polymer represented by a sulfonated polysulfone copolymer, a sulfonated poly (ether-ketone) series, a perfluorinated sulfonic acid At least one ionic conductive material selected from the group consisting of a fluorine-containing polymer, a sulfonated polyether ether ketone type, a polyimide type, a polystyrene type, a polysulfone type, and a clay-sulfonated polysulfone nanocomposite And may include a polymer.

The electrode catalyst layers 102 and 102 'may include metal catalysts such as conventional Pt or Pt alloys (such as PtRu) applied to fuel cells or may include supported catalysts in which such metal catalysts are carried on separate carriers. As the carrier, for example, a carbon powder, an activated carbon powder, a graphite powder or a powder that is a carbon powder can be used. Specific examples of the activated carbon powder include Vulcan XC-72, Ketjen black, and the like.

The ion conductive membrane layers 103 and 103 'are disposed between the electrolyte membrane 101 and the electrode catalyst layers 102 and 102' to serve to attach the electrode catalyst layers 102 and 102 'to the electrolyte membrane 101, Hydrogen ions, and / or by-products. The thickness of the ion conductive film layers 103 and 103 'is preferably 1 to 5 mu m. When the thickness is less than 1 탆, the adhesion to the electrolyte membrane 10 is undesirably weakened. If the thickness exceeds 5 탆, the movement of fuel and the like is not smooth. By providing such an ion conductive film layer, it is possible to lower the interface resistance between the electrolyte membrane and the electrode catalyst layer while improving the adhering force as compared with the prior art in which the electrode catalyst layer is directly attached to the electrolyte membrane, thereby preventing the electrode catalyst layer from being peeled off And it is possible to smoothly transfer the fuel and the like to the electrode catalyst layer. The term "coating layer" in the " ion conductive film layer "means a layer formed of a thin film of several μm or less. It is preferable that the ion conductive membrane layers 103 and 103 'are formed of the same or similar material as the above-mentioned ion conductive polymer for forming the electrolyte membrane 101. In addition, in the "ion conductive film layer "," ion conductive "is an essential characteristic that the layer must have in order to prevent it from acting as a resistance of ion transport.

3 is a view for explaining a manufacturing process of a membrane electrode assembly according to one embodiment of the present invention. Like reference numerals in the drawings denote the same elements or portions of the same elements.

Hereinafter, a method of manufacturing the membrane electrode assembly 100 according to a preferred embodiment of the present invention will be described in detail with reference to FIG.

First, a first support film 200, a composition for forming the first electrode catalyst layer 102, and a composition for forming the first ion conductive film layer 103 are prepared. Separately, a composition for forming the second support film 200 ', the second electrode catalyst layer 102', and a composition for forming the second ion conductive film layer 103 'are prepared.

As the first and second support films 200 and 200 ', a polyethylene film (PE film), a Mylar film, a polyethylene terephthalate (PET) film, a Teflon film, a polyimide film, a polytetrafluoroethylene film Etc. may be used.

The composition for forming the first and second electrode catalyst layers 102 and 102 'includes a metal catalyst or a metal supported catalyst, an ionomer and a first solvent. As the ionomer, a sulfonated highly fluorinated polymer having a main chain composed of fluorinated alkylene and a side chain composed of a fluorinated vinyl ether having a sulfonic acid group at the terminal (e.g., Nafion, a trademark of Dupont) is a typical example. All polymeric materials can be used. The ionomer is dispersed in a solvent of water and alcohol, and the content of the ionomer is preferably 5 to 50 parts by weight based on 100 parts by weight of the metal catalyst. As the first solvent, water, ethylene glycol, isopropyl alcohol, polyalcohol, etc. may be used, and the content thereof is preferably 100 to 1,000 parts by weight based on 100 parts by weight of the metal catalyst.

The composition for forming the ion conductive film layers 103 and 103 'includes the above-mentioned ion conductive polymer and the second solvent. The second solvent may be water, ethylene glycol, isopropyl alcohol, polyalcohol, or a mixture thereof. The content of the second solvent is preferably 1,000 to 10,000 parts by weight based on 100 parts by weight of the ion conductive polymer.

Next, a composition for forming the electrode catalyst layer 102 and a composition for forming the ion conductive film layer 103 are sequentially coated and selectively dried on the first support film 200 to obtain a first transfer film (steps 1 and 2 step). The coating method is not particularly limited, and a doctor blade, a bar coating, a spin coating, a screen printing, or the like may all be used. The drying is carried out at a temperature of 50 to 160 ^° C to control the residual solvent ratio to be 30% by weight or less. By controlling the solvent remaining ratio as described above, it is possible to prevent the electrode catalyst layer 102, the ion conductive film layer 103, and the electrolyte membrane 101 from being contaminated or adhering between these electrodes 101, 102, and 103 being weakened.

The surface of the electrode catalyst layer 102 formed on the first support film 200 is generally smooth and rough and has a predetermined surface roughness. When the composition for forming the ion conductive membrane layer 103 is coated on the surface of the electrode catalyst layer 102, the composition is uniformly penetrated into the gaps between the catalyst particles located on the surface of the electrode catalyst layer 102, 102 and the ion conductive film layer 103 is increased and the adhesion between them increases. In addition, since the ion conductive film layer 103 is formed of a material having the same or similar physical properties as the material of the electrolyte membrane 101 as described above, they can be easily attached to each other through a transfer process described below. By coating the ion conductive membrane layer 103 on the electrode catalyst layer 102 as described above, the electrode catalyst layer 102 is strongly adhered to the electrolyte membrane 101 via the ion conductive membrane layer 103, The contact area between the layers increases and the respective interface resistances decrease, so that the mass transfer through the electrode catalyst layer 102 and the like can be smooth. If the electrode catalyst layer 102 is directly transferred to the electrolyte membrane 101 without such an ion conductive film layer 103, adhesion or attractive force hardly acts between the catalyst particles of the electrode catalyst layer 102 and the electrolyte membrane 101 Therefore, not only is it necessary to squeeze them under very high heat and pressure conditions, but also there is a problem in that the adhesive force is not strong even after pressing.

A protective film (not shown) is covered on the top of the ion conductive film layer 103 of the first transfer film, and the protective film is cut to a desired size. Then, the protective film is removed immediately before use to be placed on one surface of the electrolyte membrane 101 do. Here, the protective film may be a modified polyethylene terephthalate film.

Separately, a composition for forming the electrode catalyst layer 102 'and a composition for forming the ion conductive film layer 103' are sequentially coated on the second support film 200 'and selectively dried to obtain a second transfer film. Here, the ion conductive film layer 103 'may be formed of the same or similar material as the aforementioned ion conductive film layer 103 or may be formed of a different material.

Next, the ion conductive film layer 103 of the first transfer film and the ion conductive film layer 103 'of the second transfer film are disposed adjacent to one surface and the other surface of the electrolyte membrane 101, respectively, The film and the second transfer film are transferred onto one surface and the other surface of the electrolyte membrane 101, respectively (Step 3). Then, the first support film 200 and the second support film 200 'are peeled off from the resultant product (step 3). The transfer of the first transfer film and the second transfer film may be performed simultaneously or separately.

The transfer of the first transfer film and the second transfer film may be performed by a thermal compression method or a roll-to-roll method. The thermocompression method is a method of compressing two or more objects at high temperature under high temperature. When the transfer is carried out by such a thermocompression method, the transfer conditions include a temperature of 100 to 160 ° C, a pressure of 1 to 300 kgf / cm ² , A 20 minute time period is preferred. The roll-to-roll method is a method in which two or more objects are successively passed through the rollers to adhere them to each other.

A catalyst coating film (CCM) having a pair of ion conductive films 103 and 103 'and a pair of electrode catalyst layers 102 and 102' is formed on one side and the other side of the electrolyte membrane 101 through the transfer process (Step 3 of FIG. 3).

However, since the above-described transfer process is performed at a relatively high temperature and a high pressure, the pores in the electrode catalyst layers 102 and 102 'are partly destroyed and the porosity thereof decreases during the transfer process. This makes it difficult to remove hydrogen ions, fuel transfer, and / or by-products through the electrode catalyst layers 102 and 102 'transferred to the electrolyte membrane 101.

In order to solve the above problems, it is preferable to further perform a post-treatment for expanding the pores of the electrode catalyst layers 102 and 102 'with respect to the membrane electrode assembly 100 manufactured. Such post-treatment may include acid treatment, washing and drying of the acid used. Specifically, after the membrane electrode assembly 100 is immersed in an acid aqueous solution such as sulfuric acid or nitric acid, the membrane electrode assembly 100 is heated at a predetermined temperature for a predetermined time, washed with pure water or the like, and then dried in a vacuum oven . ≪ / RTI >

The membrane electrode assembly according to the present invention has an ion conductive membrane layer formed between the electrolyte membrane and the electrode catalyst layer to reduce the interface resistance between the electrolyte membrane and the electrode catalyst layer and the porosity of the electrode catalyst layer is good, An improved fuel cell can be manufactured.

Hereinafter, the present invention will be described with reference to the following examples, but the present invention is not limited thereto.

Example 1

5 g of a catalyst (70 wt% PtCo / C, self-produced catalyst) and 10 g of a solution containing 10 g of a 10 wt% Nafion dispersion (Dupont, Nafion Dispersion, DE 1021) in a solvent composed of 14 g of water and 5 g of 1-propanol, to g by mixing with an ultrasonic (Bransonic, Branson 8510) and grinder (Daihan Scienticfic. WiseMix ^TM) to prepare a catalyst slurry.

The catalyst slurry prepared above was applied to a transfer paper (SCK, SKC ^Skyrol® SG31) at a ^{dose of} 0.4 mgPt / cm 2 on the basis of a platinum catalyst using a slit die coater (self-designing, manufactured by Nara Nanotek) Thereby forming an electrode catalyst layer.

Separately, a diluted Nafion solution was obtained by mixing 1 g of a 10 wt% Nafion dispersion (Dupont, Nafion Dispersion, DE 1021) in a solvent composed of 9.5 g of water and 0.5 g of isopropyl alcohol.

The diluted Nafion solution was coated on the prepared electrode catalyst layer with a slit die coater (self-designing, manufactured by Nara NanoTech Co., Ltd.) at a solid or Nafion standard of 0.5 mg / cm2 / cm2 to prepare a Nafion coating layer (I.e., ion conductive film layer) was formed. As a result, a first transferred film was obtained.

Next, a second transfer film was produced in the same manner as in the above-mentioned first transfer film.

Subsequently, the first and second transfer films prepared above were disposed adjacent to each other on one side and the other side of the NRE 211 (25 μm thick, Dupont) membrane, which was a polymer electrolyte membrane, and transferred under high temperature and high pressure conditions to prepare a membrane electrode assembly . The transferring conditions were 120 占 폚 and 120 kgf / cm2 for 2 minutes.

The prepared membrane electrode assembly was immersed in a 0.5M sulfuric acid aqueous solution, heated at 90 to 95 ° C. for 60 minutes, washed with pure water at 80 ° C. for 2 hours, and dried in a vacuum oven at 40 ° C. for 4 hours (Post-treatment process).

Comparative Example 1

A membrane electrode assembly was prepared in the same manner as in Example 1, except that the Nafion coating layer and the post-treatment process were omitted.

Evaluation example

In order to test the unit cell performance of the membrane electrode assembly prepared in Example 1 and Comparative Example 1, a gas diffusion layer (SGL 10BC, commercial GDL, SGL Carbon Group) was disposed adjacent to both sides of the membrane electrode assembly prepared above Thereby assembling the unit cell. The unit cell was operated at a temperature of the anode inlet / cell / cathode inlet of 65/65/65 ° C and a pressure of 0 psig at a ratio of hydrogen: air = 1.5: 2.0 on a chemical equivalent basis.

The cell voltage according to the current density was examined by operating the unit cell according to Example 1 and Comparative Example 1, and the result is shown in FIG.

Referring to FIG. 4, it can be seen that the cell voltage characteristics of the unit cell of Example 1 are improved compared to the cell of Comparative Example 1.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, . Accordingly, the scope of protection of the present invention should be determined by the appended claims.

1 is a cross-sectional view showing an example of a conventional membrane electrode assembly.

2 is a cross-sectional view illustrating a membrane electrode assembly according to an embodiment of the present invention.

3 is a view for explaining a manufacturing process of a membrane electrode assembly according to one embodiment of the present invention.

4 is a graph showing changes in cell voltage according to current density in a fuel cell manufactured according to Example 1 and Comparative Example 1 of the present invention.

Description of the Related Art

10, 100: membrane electrode assembly 11, 101: polymer electrolyte membrane

12, 12 ', 102, 102': electrode catalyst layer 13, 103 ': ion conductive film layer

Claims (11)

delete delete delete (a) coating and drying a composition for forming a first electrode catalyst layer on a first support film to form a first electrode catalyst layer, coating and drying a composition for forming a first ion conductive layer on the first electrode catalyst layer, 1 < / RTI > ion conductive film layer to form a first transfer film; (b) coating and drying a composition for forming a second electrode catalyst layer on the second support film to form a second electrode catalyst layer, coating and drying the composition for forming a second ion conductive layer on the second electrode catalyst layer, 2 ion conductive film layer to form a second transfer film; And (c) arranging the first ion conductive film layer of the first transfer film and the second ion conductive film layer of the second transfer film so as to be adjacent to one surface and the other surface of the electrolyte membrane, respectively, Onto the one surface and the other surface of the electrolyte membrane, respectively, Wherein each of said compositions comprises a solvent and each of said drying is carried out at a temperature of 50 to 160 DEG C so that the solvent remaining ratio in each composition is controlled to be 30% Wherein each of the ion conductive membrane layers has a thickness of 1 to 5 占 퐉. 5. The method of claim 4, Wherein the transfer of the first transfer film and the second transfer film is performed by a thermal compression method or a roll-to-roll method. 5. The method of claim 4, And removing the first support film and the second support film from the first transfer film and the second transfer film, respectively. 5. The method of claim 4, Further comprising the step of expanding the voids of the first electrode catalyst layer and the second electrode catalyst layer after the step (c). 8. The method of claim 7, Wherein the step of expanding the pores of the first electrode catalyst layer and the second electrode catalyst layer comprises an acid treatment, washing and drying. 5. The method of claim 4, Wherein the ion conductive film layer is at least one selected from the group consisting of a perfluoro proton conductive polymer film, a sulfonated polysulfone copolymer, a sulfonated poly (ether-ketone) based polymer, a perfluorinated sulfonic acid polymer containing group, a sulfonated polyether ether ketone based polymer, The present invention relates to a membrane electrode assembly for fuel cells, which comprises at least one ion-conducting polymer selected from the group consisting of polystyrene-based, polysulfone-based, and clay-sulfonated polysulfone nanocomposites Way. delete delete

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