KR101909709B1 - Membrane-Electrode Assembly with Improved Durability, Manufacturing Method Thereof and Fuel Cell Containing the Same - Google Patents

Abstract

이다.A membrane-electrode assembly for a fuel cell having improved durability, a method of manufacturing the same, and a fuel cell including the same are provided. The membrane-electrode assembly includes an electrolyte membrane, a fuel electrode of a squeeze catalyst layer facing each other with the electrolyte membrane sandwiched therebetween, and an air electrode of a squeeze catalyst layer. The both squeeze catalyst layers are made of an ion conductive material and a metal catalyst, . At this time, the compression ratio R _ano in the thickness direction of the fuel electrode compression catalyst layer and the compression ratio R _cat in the thickness direction of the air electrode compression catalyst layer satisfy the following numerical limitation conditions. And _{0 <R ano ≤ 0.5, 0} <R cat <R ano,

to be.

Description

[0001] The present invention relates to a membrane-electrode assembly for a fuel cell having improved durability, a method for manufacturing the membrane-electrode assembly, and a fuel cell including the membrane-electrode assembly.

The present invention relates to a fuel cell. More specifically, the present invention relates to a membrane-electrode assembly for a polymer electrolyte fuel cell, and a method for manufacturing the membrane-electrode assembly.

A fuel cell is a device that produces electrical energy by electrochemically reacting fuel and oxygen. Depending on the type of electrolyte used, a polymer electrolyte membrane (PEM), a phosphoric acid type, a molten carbonate type, a solid oxide type solid oxide), an alkaline aqueous solution type, and the like. Among them, the polymer electrolyte membrane fuel cell (PEMFC) has lower operating temperature and higher efficiency than the other types of fuel cells, has a large current density and output density, has a short start / stop time, .

Membrane Electrode Assembly (MEA), which generates electricity through the oxidation / reduction reaction of hydrogen and oxygen, is a core component of a polymer electrolyte fuel cell, and includes a catalyst coated membrane (CCM) (catalyst coated GDL: CCG).

In the CCM method, first, a decal film is produced by using a transfer paper, and then the transfer film is thermally compressed with the electrolyte membrane to form a membrane-electrode assembly. Separately, a microvoid is formed on the support layer A gas diffusion layer is formed, and then the membrane-electrode unit and the gas diffusion layer unit are arranged to form a cell. Such a catalyst coating film method is described in detail in, for example, Patent Document 1.

Patent Document 1:

Korean Patent Publication No. 2010-4495

On the other hand, in the catalyst coated gas diffusion layer (CCG) method, a gas diffusion layer having micropores 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- And the electrolyte membrane is thermally pressed between the diffusion layer and the electrode unit to constitute the cell.

In the polymer electrolyte fuel cell using hydrogen and air as the main fuel, since 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), p. 140).

One of the technical problems of the present invention is to improve the durability and reliability of a polymer electrolyte fuel cell by preventing deterioration of characteristics of the fuel cell polymer electrolyte membrane, particularly deterioration in the open circuit voltage environment.

In order to solve the above-mentioned technical problems, one aspect of the present invention provides a membrane-electrode assembly for a fuel cell. The membrane-electrode assembly for a fuel cell of the present invention comprises an electrolyte membrane, a fuel electrode of a squeeze catalyst layer facing each other with the electrolyte membrane sandwiched therebetween, and an air electrode of a squeeze catalyst layer, wherein the both sintered catalyst layers are made of the same or different ion- Respectively. At this time, the fuel electrode compression catalyst layer and the air electrode compression catalyst layer satisfy the following compression rate conditions:

.And _{0 <R ano ≤ 0.5, 0} <R cat <R ano,

.

Where R _ano is the compression ratio in the thickness direction of the fuel electrode compression catalyst layer and R _cat is the compression ratio in the thickness direction of the air electrode compression catalyst layer.

In one embodiment of the present invention, the chemical composition of the compression catalyst layer of the fuel electrode and the air electrode is the same. In one specific embodiment of the present invention, the moisture content of the fuel electrode is higher than that of the air electrode.

The present invention also discloses a fuel cell including such a membrane-electrode assembly for a fuel cell.

In another aspect of the present invention, a method of manufacturing the membrane-electrode assembly described above is disclosed. This manufacturing method comprises the steps of: (a) preparing a fuel electrode transfer film on which an anode catalyst layer comprising a first ion conductive material, a first metal catalyst, and optionally a first solvent is formed on a first support film, Preparing a cathode electrode transfer film on which a cathode catalyst layer is formed, wherein the cathode catalyst layer comprises a first ionomer, a second ionomer, a second metal catalyst, and optionally a second solvent;

(b) compressing the anode electrode transfer film on one side of the polymer electrolyte membrane, wherein the compression ratio R _ano in the thickness direction of the anode catalyst layer obtained in the step (a)

를 만족하도록 압착하는 연료극 전사 단계;

So as to satisfy the following equation:

와

를 만족하도록 압착하는 공기극 전사 단계를 포함한다.(c) The synthesis of the cathode pressed against the transfer film opposite the polymer electrolyte membrane side, wherein (a) the compression ratio R _cat in the thickness direction of the cathode catalyst layer obtained in step relation

Wow

So as to satisfy the following condition: &lt; EMI ID = 1.0 &gt;

In one embodiment of the present invention, the step of transferring the first transfer film and the second transfer film may be performed by a thermocompression method or a roll-to-roll method.

In another embodiment of the present invention, the thickness of the catalyst layer may be reduced by providing sub-gaskets of different thicknesses on different surfaces of the polymer electrolyte membrane and pressing the fuel electrode and the air electrode transfer film, respectively.

The method may further include removing the first supporting film and the second supporting film from the polyelectrolyte membrane to which the fuel electrode and the air electrode are transferred.

According to the embodiment of the present invention, it is possible to effectively reduce the decrease of the open circuit voltage and the current density, as compared with the fuel cell in which the fuel electrode and the air electrode are simply pressed to the polymer electrolyte membrane.

1 is a schematic view showing a cross-section of a membrane-electrode assembly of a general polymer electrolyte membrane fuel cell in a lateral direction.
2 is a schematic view showing a transverse section of a membrane-electrode assembly according to an embodiment of the present invention.
Fig. 3 is a view for explaining an embodiment of the method for producing the membrane-electrode assembly of the present invention.
4 is a graph showing changes in current density in a fuel cell manufactured according to Example 1 of the present invention and Comparative Examples 1, 2, and 3;
FIG. 5 is a graph showing changes with time of an open-circuit voltage in a fuel cell manufactured according to Example 1 of the present invention and Comparative Examples 1, 2 and 3. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a membrane-electrode assembly for a fuel cell and a method of manufacturing the same according to the present invention will be described in detail with reference to the drawings.

In one aspect of the present invention, a membrane-electrode assembly of a polymer electrolyte fuel cell is disclosed. The membrane-electrode assembly includes an electrolyte membrane, an anode (anode in the cell, anode in the cell) and a cathode (cathode in the battery) of the squeeze catalyst layer of the squeeze catalyst layer facing each other with the electrolyte membrane interposed therebetween, . The fuel electrode squeeze catalyst layer and the air electrode squeeze catalyst layer each contain an ion conductive material and a metal catalyst. The ion conductive material and the metal catalyst may be the same or different from each other in the anode and the cathode. In the membrane-electrode assembly of the present invention, the fuel electrode compression catalyst layer and the air electrode compression catalyst layer satisfy the following conditions at a compression ratio thereof. That is to say, when the compression rate in the thickness direction of the anode catalyst layer R _ano compression, compression rate in the thickness direction of the cathode catalyst layer compression _cat R, R and R _{ano cat} is

이다.And _{0 <R ano ≤ 0.5, 0} <R cat <R ano,

to be.

In the present specification, the compression ratio of the compression catalyst layer is a ratio obtained by dividing the thickness reduction value of the mixture, which occurs when the mixture for forming the compression catalyst layer is pressed onto the electrolyte membrane, by the mixture thickness before compression.

A schematic view showing a cross section of a membrane-electrode assembly of a general polymer electrolyte membrane fuel cell is shown in FIG. The membrane-electrode assembly 10 of FIG. 1 includes an electrolyte membrane 11 and electrode catalyst layers 12 and 12 'facing each other with the electrolyte membrane 11 interposed therebetween.

2 is a schematic view showing a cross section of a membrane-electrode assembly 100 for a fuel cell according to an embodiment of the present invention. The membrane-electrode assembly 100 of FIG. 2 includes an electrolyte membrane 101 and a pair of opposed catalyst layers 102 and 102 'of the anode and the anode facing each other with the electrolyte membrane 101 interposed therebetween, And the compression catalyst layers 102 and 102 'of the air electrode are compressed by the thickness of the marked portions 103 and 103' surrounded by dotted lines, respectively. That is, a mixture of the ion conductive material and the metal catalyst is compressed on the electrolyte membrane 101 to finally form the compression catalyst layers 102 and 102 '. The pre-compression thickness of the mixture is the sum of the thicknesses of the solid and the dotted lines 102 + 103, 102 '+ 103'). At this time, the compression ratio of the compression catalyst layer-the original thickness (102 + 103, 102 '+ 103') before the compression and the difference in thickness between the final compression bonding catalyst layer 102 and 102 ' - is larger at the anode side than at the cathode side. In other words, the anode was compressed more than the cathode.

In the membrane-electrode assembly for a fuel cell of the present invention, an ion conductive polymer membrane can be used as an electrolyte membrane. Some examples of such ionically conductive polymers are represented by perfluoro-based proton conductive polymers, sulfonated polysulfone copolymers, and sulfonated poly (ether-ketone) polymers, including perfluoro sulfonic acid group-containing polymers Sulfonated polyether ether ketone polymers, polyimide polymers, polystyrene polymers, polysulfone polymers, and clay-sulfonated polysulfone nanocomposites.

In the membrane-electrode assembly for a fuel cell of the present invention, the compression catalyst layer of the anode and the cathode includes an ion conductive material and a metal catalyst. As the ion conductive material of the compression catalyst layer, the above-described materials or mixtures thereof can be used for the electrolyte membrane. For example, Nafion and similar polymeric materials supplied by DuPont can be used. The ion conductive material may use the same material in the fuel electrode and the air electrode in the same or different contents, or different materials may be used.

As the metal catalyst of the squeeze catalyst layer, metal which is often used as a catalyst in this field can be used and there is no particular limitation. For example, platinum or a platinum-ruthenium alloy or a mixture may be used as the anode catalyst. As the cathode catalyst, for example, metals such as platinum, platinum-cobalt, platinum-nickel, alloys or metal mixtures can be used.

In one embodiment of the present invention, the metal catalyst is a metal particle. In another embodiment of the present invention, the metal catalyst is in the form of a carrier carrying a catalyst metal, that is, a metal-supported catalyst. In a specific embodiment of the present invention, in such a metal-supported catalyst, solid particles such as carbon powder, which have conductivity and have micropore capable of supporting catalyst metal particles, can be used. In a more specific embodiment of the present invention, the carrier is a carbon-based carrier. Examples of the carbon-based carrier of the present invention include carbon powder, activated carbon powder, graphite powder or carbon molecular weight powder, and the like. Specific examples of the activated carbon powder include Vulcan XC-72, Ketjen black, and the like. Examples of the carbon-based carrier in powder form that can be used to form the metal catalyst in the present invention include carbon black, acetylene black, carbon nanofiber powder, or a mixture thereof.

The specific gravity of the carbon-based support in such a metal-supported catalyst is suitably 30% by weight to 70% by weight based on the total weight of the metal-supported catalyst.

In a preferred embodiment of the present invention, the fuel electrode-pressed catalyst layer and the air electrode compression catalyst layer use the same metal catalyst as the same ion conductive material. In a further preferred embodiment of the present invention, the chemical composition of the anode-squeeze catalyst layer and the cathode-sintered catalyst layer is the same.

In one embodiment of the membrane-electrode assembly for a fuel cell of the present invention, the ion conductive material content of the fuel electrode sintered catalyst layer is 25 to 35% by weight based on the weight of the anode. When the content of the ion conductive material is within this range, the ion transport effect of the fuel electrode is excellent and the movement of the fuel, the hydrogen ion, or the byproduct can be smoothly maintained. On the other hand, if the content of the ion conductive material is less than 25 wt% of the weight of the anode, the ion transfer effect is not sufficient. Also, if the content exceeds 35 wt% of the weight of the anode, the flow paths of fuel, hydrogen ions and byproducts may become clogged or narrowed.

In one embodiment of the membrane-electrode assembly for a fuel cell of the present invention, the ion conductive material content of the air electrode sintered catalyst layer is 20 to 33 wt% based on the weight of the air electrode. All. More preferably not less than 25% by weight, and not more than 33% by weight. When the content of the ion conductive material is within this range, the oxygen in the air reacts with the proton to produce water at a high rate and maintains the water content of the air electrode at an appropriate level, so that the fuel is smoothly moved. On the other hand, if the content of the ion conductive material is less than 20 wt% of the weight of the air electrode, it is impossible to sufficiently provide a site where air can react, and if the content exceeds 33 wt% It is undesirable because the water content becomes excessive and the movement of the fuel can be slowed down.

In the membrane-electrode assembly of the present invention, the compression catalyst layer does not contain a solvent or contains a solvent, and the solvent remaining ratio is 30% by weight or less based on the weight of the compression catalyst layer. When the residual solvent ratio is 30% by weight or less, it is possible to prevent the fouling catalyst layer and the electrolyte membrane from being contaminated or the adhesion between them being weakened.

In one embodiment of the present invention, the thickness of the compression catalyst layer is 5 to 20 占 퐉. If the compression catalyst layer is thicker, water management and water discharge are not easy, which causes a decrease in durability.

In the membrane-electrode assembly for a fuel cell of the present invention, the fuel electrode squeeze catalyst layer and the air electrode squeeze catalyst layer are squeezed for bonding with the electrolyte membrane. In the membrane-electrode assembly for a fuel cell of the present invention, the compression ratio R _ano (reduction rate of the thickness in the direction of the fuel electrode-electrolyte membrane-air electrode) of the fuel electrode compression catalyst layer is 50% or less. More preferably, the compression ratio R _cat of the fuel electrode compression catalyst layer is 30% to 50% or less. A fuel cell membrane of the invention the compression ratio of the air electrode squeezed catalyst layer in the electrode assembly R _cat (fuel electrode-electrolyte membrane of the air electrode direction thickness reduction ratio) of R is less than _ano, ratio R _cat / R _ano of R _cat for R _ano 0.4 Or more. More preferably, the compression ratio R _cat / R _ano is 0.45 to 0.8.

When the compression ratio of the fuel electrode squeeze catalyst layer is within the above-mentioned range, the pore volume of the fuel electrode can be reduced to enhance the water-containing property, so that the fuel electrode is maintained in a high humidity state and the electrolyte membrane deterioration rate can be reduced. If the compression ratio of the anode catalyst layer exceeds 50%, the pore structure of the electrode layer may be destroyed, which may adversely affect performance and durability. Compressing the air electrode compression catalyst layer under the above-described conditions produces an electrode pore structure that can facilitate water management of the air electrode.

When the compression ratio R _cat / R _ano of the compression catalyst layer of the anode and the cathode is within the above range, the durability of the membrane-electrode assembly can be improved. If the compression ratio of the compressed catalyst layer is maintained within this range, the rate at which the cell performance such as the OCV and the current density decreases over time can be slower than the fuel cell produced by compressing the catalyst layers of the both electrodes at the same ratio .

Polymer membrane deterioration is caused by pollution, heat, electrochemical deterioration, and pressure. Transport fuel cells are prone to deterioration due to extreme operating conditions. In the fuel cell for transportation, the polymer chains of the electrolyte membrane break down due to electrochemical causes. During the durability test of a typical fuel cell, when the OCV state and the low voltage state are repeated during the voltage cycle operation, the high humidification state and the low humidification state occur and the mechanical property is deteriorated and the membrane tears. Also, the deterioration of the electrolyte membrane of the oxygen radical / hydrogen peroxide accelerates under the OCV / low humidification condition, and the degradation rate of the polymer increases when the fuel electrode catalyst layer is maintained in a low humidity state for a long time.

The compressibility of the electrode catalyst layer varies depending on the degree of pressurization of the membrane-electrode assembly, such as hot pressing or hot rolling, and as the compression ratio increases, the pores of the electrode catalyst layer become dense and the water content can be improved. However, if the compression ratio is excessively high, the pores of the electrode catalyst layer become too dense or destroyed and the water discharge is not smooth, resulting in durability. The present inventors have found that if the electrode catalyst layer is pressed onto the electrolyte membrane under the conditions as described above, the electrode layer of the fuel electrode is kept in a more humidified state, and the durability of the fuel cell can be improved by delaying the acceleration of the membrane deterioration.

In the above-described specific embodiment of the present invention in which the chemical composition of the anode and the cathode catalyst layer is the same, the compression ratio of the compression catalyst layer directly leads to the ratio of the density of the compression catalyst layer. That is, in this specific embodiment, the ratio of the density of the air electrode compression catalyst layer divided by the density of the fuel electrode compression catalyst layer is 0.4 or more and less than 1. More preferably, the density ratio is 0.45 to 0.8.

In one embodiment of the present invention, the water content of the anode is higher than that of the cathode.

In one aspect of the present invention, a method for producing a membrane-electrode assembly of the above-described polymer electrolyte fuel cell is disclosed.

In the manufacturing method of the present invention, the membrane-electrode assembly is manufactured by a catalyst coating film (CCM) method using a wet process. In the method of the catalyst coating film (CCM), the thickness of the electrode catalyst layer is controlled by adjusting the pressure of the electrolyte membrane against the anode and the cathode.

The above-mentioned manufacturing method comprises the steps of: (a) preparing a fuel electrode transfer film on which an anode catalyst layer comprising a first ion conductive material, a first metal catalyst and optionally a first solvent is formed on a first support film, Preparing a cathode electrode transfer film on which a cathode catalyst layer comprising a second ion conductive material, a second metal catalyst and optionally a second solvent is formed,

(b) compressing the anode electrode transfer film on one side of the polymer electrolyte membrane, wherein the compression ratio R _ano in the thickness direction of the anode catalyst layer obtained in the step (a)

를 만족하도록 압착하는 연료극 전사 단계,

So as to satisfy the following equation:

와

를 만족하도록 압착하는 공기극 전사 단계를 포함한다.(c) The synthesis of the cathode pressed against the transfer film opposite the polymer electrolyte membrane side, wherein (a) the compression ratio R _cat in the thickness direction of the cathode catalyst layer obtained in step relation

Wow

So as to satisfy the following condition: &lt; EMI ID = 1.0 &gt;

3 is a view for explaining a method of manufacturing a membrane-electrode assembly according to an embodiment of the present invention. Like reference numerals in the drawings denote the same elements or portions of the same elements. Hereinafter, one embodiment of the membrane-electrode assembly manufacturing method of the present invention will be described in detail with reference to FIG.

First, a first support film 200 and a composition for forming a fuel electrode are prepared for the production of a transfer film of step (a). Also, a second support film 200 'and a composition for forming an air electrode are prepared.

As the first and second support films 200 and 200 ', a polyethylene film, a polyethylene terephthalate (PET) film, a Teflon film, a polyimide film (for example, Kepton film), a polytetrafluoroethylene film, But are not limited to these.

The composition for forming an anode includes a first solvent, a first metal catalyst, and a first ion conductive material. The composition for forming an air electrode comprises a second solvent second metal catalyst, and a second ion conductive material.

The ion conductive material used in the composition for forming the anode or the air electrode is the same as the ion conductive material in the above-described membrane-electrode junction body compression catalyst layer. The first ion conductive material and the second ion conductive material are independent of each other, but the same materials may be used in the same amount. In the above-mentioned composition for forming an electrode, the ion conductive material is dispersed in a solvent. Like the ion conductive material, both the first solvent and the second solvent may be the same or different. As the first and second solvents, water, ethylene glycol, isopropyl alcohol, polyalcohol, N-butyl alcohol, N-butyl acetate, or a mixture thereof may be used independently. In one specific embodiment of the present invention, a detergent may be added to the composition for forming the anode or the air electrode so that the ion conductive material is easily dispersed. An example of such a detergent is Triton X-10. The amount of the first solvent and the second solvent can be appropriately adjusted by a person skilled in the art according to the specific volume of the metal catalyst. In most cases, if the amount is 100 to 1,700 parts by weight based on 100 parts by weight of the metal catalyst It is suitable.

In a preferred embodiment of the present invention, the composition for anode electrode and the composition for forming the air electrode use the same metal catalyst (with the same content or different content) as the same ion conductive material. In a more preferred embodiment of the present invention, the chemical composition of the anode-forming composition and the cathode-forming composition are the same.

Next, to form a transfer film of step (a), a composition for forming the fuel electrode 102 is coated on the first support film 200 and dried to obtain a first transfer film having a fuel electrode catalyst layer (layer of a composition for forming a fuel electrode) The same process is repeated on the second support film 200 'to obtain a second transfer film having a cathode catalyst layer (a layer of a composition for forming an air electrode) formed thereon. Of course, it is also possible to change the coating of the fuel electrode and the air electrode at the same time, or to perform the drying at the same time. Depending on whether the solvent remains or not, a solvent may be further included in the both electrode catalyst layers.

The above-mentioned coating method is not particularly limited. In various embodiments of the manufacturing method of the present invention, a doctor blade, a bar coating, a spin coating, a screen printing, or the like may all be used.

In one specific embodiment of the method of the present invention, drying of the electrode forming composition applied to the support film is carried out at a temperature of 30 to 150 캜 to control the solvent remaining ratio to be 30% or less. By controlling the solvent remaining ratio as described above, it is possible to prevent the electrode catalyst layer and the electrolyte membrane from being contaminated or the adhesion between them being weakened.

가 0 초과 0.5 이하가 되도록 한다.In the fuel electrode transfer step (b) of the above-described manufacturing method, the untouched fuel electrode 102 of the first transfer film is disposed adjacently to one surface of the electrolyte membrane 101 and is compressed. At this time, the compression is performed such that the anode catalyst layer coated on the first support film (200) of the first transfer film is converted into a fuel electrode sintered catalyst layer after compression, and the thickness reduction rate (compression ratio) is 50% or less. That is, the compression ratio of the anode catalyst layer in the thickness direction

Is greater than 0 and less than 0.5.

가 0 초과 R_ano 미만이 되도록 한다. 아울러 관계식

를 만족하도록 공기극에 압력을 가한다. 더 바람직하게는 상기 압축률의 비 R_cat/R_ano가 0.45에서 0.8이 되도록 압착한다.In the air electrode transfer step (c) of the above-described manufacturing method, the air electrode 102 'on the second transfer film is disposed adjacent to the opposite surface of the electrolyte membrane 101 without removing the first transfer film, do. At this time, the air electrode catalyst layer coated on the second support film 200 'of the second transfer film is pressed, and the air electrode catalyst layer is compressed so that the thickness reduction rate (compression ratio) is less than the compression ratio of the anode. That is, the compression ratio of the anode catalyst layer in the thickness direction

Is greater than 0 R _ano . Furthermore,

The pressure is applied to the air electrode. More preferably, the compression ratio R _cat / R _ano is 0.45 to 0.8.

In one embodiment of the production method of the present invention, when the first transfer film is first pressed against the electrolyte membrane and the second transfer film is compressed by the means for obtaining the compression ratio of the electrode catalyst layer as described above, Squeeze with pressure. For example, in a more specific embodiment of the present invention, the pressing temperature is 80 ° C to 140 ° C, and the pressing pressure P ₁ of the first transfer film and the pressing pressure P ₂ of the second transfer film satisfy the following conditions have.

&Quot; (1) &quot;

30 kg / cm ² ? P ₁ ? 270 kg / cm ²

&Quot; (2) &quot;

1 kg / cm ² ? P ₂ ? 120 kg / cm ²

&Quot; (3) &quot;

P ₁ > P ₂

In another embodiment of the production method of the present invention, the compression ratio can be adjusted by providing a sub gasket having a different thickness for each surface of the electrolyte membrane as a means for obtaining the compression ratio of the electrode catalyst layer as described above. For example, in a more specific embodiment of the present invention, the fuel electrode sub gasket is thinner than the air electrode sub gasket. A case where the sub gaskets having different thicknesses are provided on both surfaces of the electrolyte membrane is illustrated in Fig.

In FIG. 3, the sub gaskets 300 and 300 'are provided in the edge regions on both sides of the electrolyte membrane 101. The sub gaskets 300 and 300 'are provided for maintenance of the surface pressure of the membrane-electrode assembly, airtightness, and convenience of handling, and are preferably thicker than the electrode catalyst layer. 3, a sub gasket 300 is provided on the rim of the surface of the electrolyte membrane 101 on which the fuel electrode squeeze catalyst layer is to be formed. The sub gasket 300 is thicker than the fuel electrode catalyst layer. On the surface of the electrolyte membrane 101 surrounded by the sub- The first transfer film including the first support film 200 and the anode catalyst layer 102 is squeezed. A sub gasket 300 'which is thicker than the air electrode catalyst layer is provided at the edge of the electrolyte membrane 101 opposite to the electrolyte membrane 101 so that the second gas barrier layer 200' and the air electrode catalyst layer 102 ' 2 Squeeze the transfer film. In the embodiment shown in FIG. 3, the sub-gasket 300 of the fuel electrode is thinner than the sub-gasket 300 'of the air electrode.

In a specific embodiment of the present invention, when the second transfer film is squeezed as a means for obtaining the compression ratio of the electrode catalyst layer as described above, it is compressed at a pressure lower than that of the first transfer film, and the fuel electrode sub- Thinner.

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. A method of thermo-compression bonding method is pressed together at least two objects at a high temperature, if made of a transfer by such thermal compression bonding method, a transfer condition as at 80 to a temperature of 140 ℃, 1 to 270 kg pressure in the / cm ^2, and A time period of 1 to 10 minutes is preferable. The roll-to-roll method is a method in which two or more objects are attached by continuously passing between rollers. Such a thermocompression method or a roll-to-roll method may be used in a manner well known in the art, and therefore, it is not described herein.

Then, the first supporting film 200 and the second supporting film 200 'are peeled and removed from the resultant product. The transfer of the first transfer film and the second transfer film may be performed simultaneously or separately.

A CCM membrane-electrode assembly can be obtained in which a pair of electrode catalyst layers 102 and 102 'are formed on both surfaces of the electrolyte membrane through the transfer process.

In another aspect of the present invention, there is provided a polymer electrolyte fuel cell comprising such a membrane-electrode assembly. The membrane-electrode assembly according to the present invention facilitates water management and mass transfer in the electrode layer, thereby making it possible to manufacture a fuel cell having high durability.

After the membrane-electrode assembly is manufactured as described above, a step of providing a gas diffusion layer may be performed according to a known technique, and then one separator plate having flow paths may be laminated to form one unit cell. When a plurality of such unit cells are stacked, a fuel cell stack having a desired size can be obtained. This is well known in the art and is not described here.

[ Example ]

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are intended to illustrate the present invention, but the scope of the present invention is not limited thereto.

In order to compare the performance of the membrane-electrode assembly according to the present invention and the membrane-electrode assembly of the prior art, the membrane-electrode assemblies of Examples and Comparative Examples were prepared and evaluated for their performance.

(G / eq) of 1000, an ionic conductivity of 0.09 S / cm and a water content of 25 wt% was added to a mixed solvent of 37 g of water and 19 g of 1-propanol in an amount of 10 g / 8.5 g of a 20 wt% solution (Dupont, Nafion Dispersion, DE 2020), 5 g of platinum-supported Ketjenblack (platinum 45 wt%) as a metal catalyst, and 5 g of a Triton X-100 solution %) Was added. This mixture was uniformly dispersed by using an ultrasonic wave and a pulverizer to obtain a composition for electrode formation. As the first supporting film and the second supporting film, a transfer paper (Skyrol SM30 (registered trademark), PET film made by SKC) was used. The composition for electrode formation was applied to the first support membrane for fuel electrode at a dose of 0.2 mg Pt / cm 2 on the basis of a platinum catalyst using a slit die coater, and the composition for electrode formation was applied to the air electrode at 0.4 mg Pt / The composition for electrode formation was applied to a second support film to obtain first and second transfer films, respectively. Each transfer film was then dried in a drying oven at 80 DEG C for 4 minutes.

After the transfer film was obtained, a sub gasket made of ePTFE (HP-010-30 from Sumitomo Corporation) having a thickness of 30 탆 was provided on the side of the anode of the NRE 211 (Dupont, thickness 25 탆) film as the polymer electrolyte membrane. Subsequently, the first transfer film was thermally compressed and transferred to the electrolyte membrane surface supported with the sub gasket at a rate of 120 kg / cm ² for 2 minutes. Next, a sub gasket made of ePTFE (HP-010-50 made by Sumitomo Corporation) having a thickness of 50 탆 was provided on the opposite surface of the electrolyte membrane on the air electrode side. Subsequently, the second transfer film was thermally compressed and transferred to the air electrode side at 60 kg / cm ² for 2 minutes.

The thicknesses of the anode and air electrode, which were 9 ㎛ and 18 ㎛ after squeezing, respectively, decreased to 6 ㎛ and 14 ㎛ after squeezing. Compression ratios of the anode and the air electrode according to this value were 0.33 and 0.22, respectively, and the compression ratio was (4/18) / (3/9)? 0.67.

[Comparative Example 1]

The same first transfer film as in Example 1 was thermally bonded and transferred to the surface of the electrolyte membrane of Example 1 at 200 kg / cm ² for 2 minutes. On the opposite side of the electrolyte membrane to the air electrode side, 200 kg / cm 2 ² for 2 minutes, and the same second transfer film as in Example 1 was thermally compressed and transferred.

The thicknesses of the anode and air electrode, which were 9 ㎛ and 18 ㎛ after squeezing, respectively, decreased to 4.4 ㎛ and 8.8 ㎛ after squeezing. The compression ratio of the anode and the cathode according to this value was 0.51, which was more than 50%, and the compression ratio was 1.

[Comparative Example 2]

The same first transfer film as in Example 1 was thermally compressed and transferred to the surface of the electrolyte membrane of Example 1 at 60 kg / cm ² / cm ² , and then transferred to a surface of the electrolyte membrane opposite to the air electrode at a rate of 60 kg / ² for 2 minutes, and the same second transfer film as in Example 1 was thermally compressed and transferred.

The thickness of the anode and air electrode, which were 9 ㎛ and 18 ㎛ after squeezing, respectively, decreased to 7.2 ㎛ and 14.4 ㎛ after squeezing. The compression ratio of the anode and the cathode according to this value was 0.2, which was less than 50%, but the compression ratio was 1.

[Comparative Example 3]

The same first transfer film as in Example 1 was thermally bonded and transferred at 200 kg / cm ² on the surface of the electrolyte membrane of the same electrolyte membrane as that of Example 1 for 2 minutes, and 60 kg / cm 2 of the electrolyte membrane ² for 2 minutes, and the same second transfer film as in Example 1 was thermally compressed and transferred.

The thicknesses of anode and cathode, which were 9 ㎛ and 18 ㎛, respectively, before compression, decreased to 4.3 ㎛ and 13.3 ㎛ after compression, respectively. Compression ratios of the anode and the cathode according to this value were 0.52 and 0.26, respectively, and the fuel electrode compression ratio exceeded 50% and the compression ratio was 0.5.

Assessment Methods

In order to test the performance of the unit cell including the membrane-electrode assembly manufactured in Example 1 and Comparative Examples 1, 2 and 3, a gas diffusion layer (SGL 10BC, commercial GDL , SGL Carbon Group) were disposed adjacent to each other to assemble the unit cells. The unit cell was operated at a ratio of hydrogen: air = 1.5: 2.0 on the basis of the chemical equivalent, while maintaining the temperature of the inlet of the anode / inlet of the anode / cathode at 65/65/65 ° C and the pressure of 0 psig.

The durability acceleration evaluation was performed by continuously repeating the unit cell thus obtained for 120 hours in a cycle of OCV (60 seconds) -0.6 V (60 seconds) -0.4 V (60 seconds) to monitor the change of the current density and the OCV voltage in real time .

Table 1 is a table summarizing the current density reduction rate and the OCV reduction rate in the fuel cell manufactured according to Example 1 of the present invention and Comparative Examples 1, 2 and 3.

division Current Decay Rate at 0.6 V (%) OCV reduction rate (%) Example 1 -0.3 -0.2 Comparative Example 1 -8.2 -1.4 Comparative Example 2 -1.6 -1.1 Comparative Example 3 -4.0 -0.8

It can be seen from the data of Table 1 that the current and OCV holding characteristics of Example 1 according to the present invention are at least 5 times or more and at least 4 times better than Comparative Examples 1 to 3, respectively. This demonstrates the durability of the fuel cell having the membrane-electrode assembly of the present invention.

4 is a graph showing current densities measured by durability tests of the unit cells including the membrane-electrode assembly of Example 1 and Comparative Examples 1, 2 and 3 under the above-described conditions. Referring to FIG. 4, it can be seen that the characteristics of the current density of the cells in the unit cells of Example 1 and Comparative Example 2 are constant compared with those of Comparative Examples 1 and 3.

FIG. 5 shows the OCV voltage measured in the durability test of the unit cell according to Example 1 and Comparative Examples 1, 2, and 3. Referring to FIG. 5, it can be seen that the OCV voltage characteristic of the cell of Example 1 is constant as compared with the cells of Comparative Examples 1, 2 and 3.

Comparative Example 1 shows a tendency that both the current density and the OCV voltage are reduced due to a too high thickness reduction rate.

In Comparative Example 2, although the current density characteristics are constant, the OCV voltage tends to decrease.

In Comparative Example 3, the current density and the OCV voltage reduction rate are smaller than those of Comparative Example 1, but the performance fluctuation is significant.

From the graphs of FIGS. 3 and 4 and the data of Table 1, it can be seen that using the membrane-electrode assembly for a fuel cell of the present invention satisfying a compression ratio of 50% or less of the anode electrode compression catalyst layer and a compression ratio of 0.4 to 1 It is possible to maintain the voltage and current density more stably than the fuel cell of the related art. On the other hand, in the comparative membrane-electrode assembly manufactured by using the air electrode and the fuel electrode squeeze catalyst side at the same compression ratio, durability of the membrane with decreasing OCV was lowered in a degradation accelerated environment such as a voltage cycle.

While the present invention has been particularly shown and described with reference to certain exemplary embodiments thereof, it should be understood that the same is by way of illustration and example only and is not to be taken by way of limitation. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. .

Therefore, it is to be understood that the present invention is not limited to the above-described embodiments and the appended claims, and all equivalents and equivalent modifications of the claims are also within the scope of the present invention.

10, 100: membrane-electrode assembly 11, 101: polymer electrolyte membrane
12, 12 ', 102, 102': electrode catalyst layers 103 and 103 '
200, 200 'Support film of transfer film 300, 300' Sub gasket

Claims (17)

An electrolyte membrane;
A membrane electrode assembly comprising a fuel electrode of a squeeze catalyst layer facing each other with the electrolyte membrane interposed therebetween and a cathode of a sintered catalyst layer,
Wherein the both-squeeze catalyst layer contains an ion conductive material and a metal catalyst which may be the same or different from each other,
_Wherein the compression ratio R _ano in the thickness direction of the fuel electrode compression catalyst layer and the compression ratio R _cat in the thickness direction of the air electrode compression catalyst layer satisfy the following numerical limitations:
And _{0 <R ano ≤ 0.5, 0} <R cat <R ano,

to be. The membrane-electrode assembly for a fuel cell according to claim 1, wherein the numerical value limiting condition further includes the following conditions:

The membrane-electrode assembly for a fuel cell as claimed in claim 1, wherein the compression catalyst layer of the fuel electrode and the air electrode uses the same metal catalyst as the same ion conductive material. 4. The membrane-electrode assembly for a fuel cell according to claim 3, wherein the fuel electrode and the compressed catalyst layer of the air electrode have the same chemical composition. 5. The membrane-electrode assembly for a fuel cell according to claim 4, wherein a ratio of the density of the air electrode compression catalyst layer divided by the density of the fuel electrode compression catalyst layer is 0.4 or more and less than 1. The method according to claim 1, wherein the ion conductive material of the fuel electrode and the air electrode is selected from the group consisting of a perfluoro sulfonic acid group-containing polymer, a perfluoro proton conducting polymer, a sulfonated polysulfone copolymer, a sulfonated poly (ether- Wherein the polymer is selected from the group consisting of a polymer, a sulfonated polyether ether ketone polymer, a polyimide polymer, a polystyrene polymer, a polysulfone polymer, and a clay-sulfonated polysulfone nanocomposite and a mixture thereof Wherein the membrane-electrode assembly is a membrane-electrode assembly for a fuel cell. The membrane-electrode assembly for a fuel cell according to claim 1, wherein the metal catalyst is a metal-based or metal-supported carbon-based support. The fuel cell according to claim 1, wherein the content of the ion conductive material in the anode is 25 wt% or more and 35 wt% or less based on the total weight of the anode, and the content of the ion conductive material in the anode is Based on the total weight of the air electrode, and is 20 wt% or more and 33 wt% or less based on the total weight of the air electrode. [Claim 7] The method according to claim 7, wherein the metal catalyst is a carbon-based carrier on which the metal particles are supported, and the specific gravity of the metal particles in the carbon-based carrier is 30 wt% to 70 wt% Wherein the membrane-electrode assembly is a membrane-electrode assembly for a fuel cell. The membrane-electrode assembly for a fuel cell according to claim 1, wherein the moisture content of the fuel electrode is higher than that of the air electrode. 11. A fuel cell comprising the membrane-electrode assembly of any one of claims 1 to 10. (a) preparing a fuel electrode transfer film on which a fuel electrode catalyst layer comprising a first ion conductive material, a first metal catalyst and optionally a first solvent is formed on a first support film, and a second ion conductive material Preparing a cathode electrode transfer film on which a cathode catalyst layer comprising a second metal catalyst and optionally a second solvent is formed;
(b) compressing the anode electrode transfer film on one side of the polymer electrolyte membrane, wherein the compression ratio R _ano in the thickness direction of the anode catalyst layer obtained in the step (a)

So as to satisfy the following equation:
(c) The synthesis of the cathode pressed against the transfer film opposite the polymer electrolyte membrane side, wherein (a) the compression ratio R _cat in the thickness direction of the cathode catalyst layer obtained in step relation

Wow

Wherein the step (c) comprises the steps of: 13. The method of claim 12, wherein (b) and (c) compression bonding temperature of the step is 80 ℃ to 140 ℃, contact pressure of the step (b) is 30 kg of / cm ² Or more, of 270 kg / cm ² or less, and the contact pressure of the step (c) is natdoe, of 1 kg / cm ² than the contact pressure of the step (b) Or more and 120 kg / cm &lt; ² &gt; or less, based on the total mass of the membrane-electrode assembly. [12] The method of claim 12, wherein the step (b) comprises: providing a fuel electrode sub gasket thicker than the anode electrode transfer film on the same surface as the anode electrode transfer film in the polymer electrolyte membrane, Wherein a gas electrode sub gasket having a thickness larger than that of the air electrode transfer film is provided on the same surface as the air electrode transfer film and is compressed. 15. The method according to claim 14, wherein the fuel electrode sub gasket is thinner than the air electrode sub gasket. 13. The membrane-electrode assembly for a fuel cell according to claim 12, wherein the step (b) or the step (c) is carried out by a thermocompression bonding method or a roll-to-roll method. Way. 13. The method of claim 12, further comprising removing a first support film and a second support film from the polymer electrolyte membrane onto which the fuel electrode and the air electrode are transferred.

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