WO2017175890A1 - Composite electrolyte membrane for fuel cell, membrane-electrode assembly comprising same, fuel cell comprising same, and method for manufacturing composite electrolyte membrane for fuel cell, membrane-electrode assembly comprising same, and fuel cell comprising same - Google Patents

Abstract

A composite electrolyte membrane for a fuel cell, and a membrane-electrode assembly and a fuel cell comprising same, according to the present invention, use an electrolyte membrane impregnated with a fluoride-based ionomer solution containing a PTFE porous support which comprises pores having a specific aspect ratio and hollow silica, thereby effectively simplifying the structure of the electrolyte membrane and enhancing performance when applied to the fuel cell.

Description

Composite electrolyte membrane for fuel cell, membrane-electrode assembly comprising same, fuel cell comprising same, and method for manufacturing same

The present invention relates to an electrolyte membrane, and more particularly, to a composite electrolyte membrane for a fuel cell, a membrane-electrode assembly including the same, a fuel cell including the same, and a method of manufacturing the same.

A fuel cell is a power generation system that directly converts chemical energy generated by electrochemical reaction between fuel (hydrogen or methanol) and oxidant (oxygen) to electrical energy.It is an eco-friendly feature with high energy efficiency and low emission of pollutants. Research and development. The fuel cell can be used by selecting a fuel cell for high temperature and low temperature according to the application field, and is generally classified according to the type of electrolyte. For high temperature, a solid oxide fuel cell (SOFC) and molten carbonate are used. Fuel cell (Molten Carbonate Fuel Cell, MCFC) and the like, Alkaline Fuel Cell (AFC) and Polymer Electrolyte Membrane Fuel Cell (PEMFC) are being developed for low temperature.

Subdivided into a double polymer electrolyte fuel cell is a hydrogen ion exchange membrane fuel cell (PEMFC) that uses hydrogen gas as a fuel, and direct methanol that supplies liquid methanol directly to the anode as a fuel. Fuel cell (Direct Methanol Fuel Cell, DMFC). Polymer electrolyte fuel cells have been spotlighted as portable, automotive, and home power supplies for their low operating temperatures of less than 100, elimination of leakage problems due to the use of solid electrolytes, fast startup and response characteristics, and excellent durability. In particular, as a high output fuel cell having a higher current density than other types of fuel cells, it is possible to miniaturize, and thus research into a portable fuel cell continues.

The unit cell structure of the fuel cell has a structure in which an anode (anode, fuel electrode) and a cathode (cathode, oxygen electrode) are coated on both sides of an electrolyte membrane made of a polymer material, which is a membrane-electrode assembly (Membrane). Electrode Assembly (MEA). The membrane-electrode assembly (MEA) is a portion in which an electrochemical reaction between hydrogen and oxygen occurs and is composed of a cathode, an anode, and an electrolyte membrane, that is, an ion conductive electrolyte membrane (eg, a hydrogen ion conductive electrolyte membrane).

In the anode, hydrogen or methanol, which is a fuel, is supplied to generate an oxidation reaction of hydrogen to generate hydrogen ions and electrons. In the cathode, water is generated by a reduction reaction of oxygen by combining hydrogen ions and oxygen that have passed through the polymer electrolyte membrane. .

The membrane-electrode assembly has a form in which the electrode catalyst layers of the anode and the cathode are coated on both sides of the ion conductive electrolyte membrane, and the material forming the electrode catalyst layer is Pt (platinum), Pt-Ru (platinum-ruthenium), or the like. The catalyst substance of is supported on the carbon carrier. Membrane-electrode assembly (MEA), which can be seen as a key component of the electrochemical reaction of fuel cells, is especially used for ion-conducting electrolyte membranes and platinum catalysts, which have a high price ratio, and is directly related to power production efficiency. It is considered as the most important part in improving the performance and increasing the price competitiveness.

Conventional methods for preparing MEAs that are commonly used include preparing a paste by mixing a catalyst material, a hydrogen ion conductive binder, ie, a fluorine-based Nafion ionomer, and water and / or an alcohol solvent, It is coated with a carbon cloth or carbon paper that serves as an electrode support that supports the catalyst layer and at the same time serves as a gas diffusion layer, and then dry and heat-bond the hydrogen ion conductive electrolyte membrane.

Redox reaction of hydrogen and oxygen by the catalyst in the catalyst layer; Transfer of electrons by tightly bonded carbon particles; Securing passages for supplying hydrogen, oxygen and moisture and for discharging excess gas after the reaction; The movement of oxidized hydrogen ions must be carried out at the same time. Furthermore, in order to improve performance, the area of the triple phase boundary where the feed fuel, the catalyst and the ion conductive polymer electrolyte membrane meet must be increased to reduce the activation polarization, and the interface between the catalyst layer and the electrolyte membrane and the catalyst layer The interface between the gas diffusion layer and the gas must be uniformly bonded to reduce ohmic polarization at the interface. Therefore, in order to improve the performance of the fuel cell by reducing the interface resistance between the catalyst layer and the electrolyte membrane as much as possible, not only the bonding force between the catalyst layer and the electrolyte membrane should be provided during MEA production, but also the interface bonding between the catalyst layer and the electrolyte membrane during the fuel cell operation is performed. It must be maintained.

Therefore, in recent years, the development of technology for uniformly bonding the interface between the catalyst layer and the electrolyte membrane and the interface between the catalyst layer and the gas diffusion layer has been actively made, but the interface uniformity still has a disadvantage.

In addition, since the MEA having the above-described structure typically uses a thick electrolyte membrane, the transfer of hydrogen ions may be delayed, thereby degrading performance.

In addition, as the movement and use time of the hydrogen ions become longer during driving of the fuel cell, the interface between the catalyst layer and the electrolyte membrane and the interface bonding between the catalyst layer and the gas diffusion layer become weak and are separated from each other. Thus, when applied to the fuel cell may cause a decrease in the performance of the fuel cell.

The present invention has been made to solve the above problems, and has a simplified structure, a composite electrolyte membrane for a fuel cell that can improve the interfacial properties, a membrane-electrode assembly comprising the same, a fuel cell comprising the same, and their production The purpose is to provide a method.

The present invention also provides a composite electrolyte membrane for a fuel cell, a membrane-electrode assembly including the same, a fuel cell including the same, and the like, which can prevent delivery delay of hydrogen ions and improve mechanical properties to improve fuel cell performance. It is another object to provide a manufacturing method.

Another object of the present invention is to provide a composite electrolyte membrane for a fuel cell, a membrane-electrode assembly including the same, and a method for manufacturing a fuel cell including the same, which can simplify the manufacturing process.

Method for producing a composite electrolyte membrane for a fuel cell of the present invention for solving the above problems is a step of forming a PTFE porous support comprising pores having a predetermined aspect ratio; Impregnating the PTFE porous support with a fluorine-based ionomer solution containing hollow silica; And drying and heat-treating the impregnated PTFE porous support. It includes.

In a preferred embodiment of the present invention, the fuel cell composite electrolyte membrane may have a thickness variation coefficient (CV1) value of the relational expression 1 below 15%, and a weight variation coefficient CV2 value of the relational expression 2 below 170% or more.

[Relationship 1]

Thickness variation coefficient (CV1,%) = (Composite electrolyte membrane thickness for fuel cell-PTFE porous support thickness / PTFE porous support thickness) × 100

[Relationship 2]

Weight variation coefficient (CV2,%) = (Complex electrolyte membrane weight for fuel cell-PTFE porous support weight) / (PTFE porous support weight) × 100

As a preferred embodiment of the present invention, the average pore size of the PTFE porous support of the first step is 0.10 ~ 0.50 ㎛, porosity may be 60 ~ 90%.

In a preferred embodiment of the present invention, the PTFE porous support may be formed by sintering a biaxially stretched PTFE sheet and the uniaxial draw ratio and biaxial draw ratio may be 1: 5 to 15.

As a preferred embodiment of the present invention, the sintering process may be performed at a temperature of 250 ~ 450.

In one preferred embodiment of the present invention, the PTFE sheet, forming a paste containing 10 to 20 parts by weight of lubricant with respect to 100 parts by weight of PTFE fine powder; Aging the paste at a temperature of 50-90 for 10-15 hours; Compressing the aged paste in a compressor to produce a PTFE block; Pressing the PTFE block at 400 to 800 psi pressure and calendering to form a PTFE sheet; Drying the PTFE sheet to remove the lubricant; And stretching the sheet from which the lubricant has been removed.

As a preferred embodiment of the present invention, the hollow silica is spherical, the average particle diameter is 10 ~ 300 nm, the diameter of the hollow may be 5 ~ 100 nm.

In a preferred embodiment of the present invention, the fluorine-based ionomer solution may further include one or more moisture absorbents selected from the group consisting of zeolite, titania, zirconia, and montmorillonite.

As a preferred embodiment of the present invention, the fluorine-based ionomer solution may include 0.05 to 5 wt% of hollow silica.

In a preferred embodiment of the present invention, the fluorine-based ionomer may include one or more selected from the group consisting of Nafion, Flemion, and Aciplex.

As a preferred embodiment of the present invention, the drying of the third step is performed for 1 to 30 minutes at 60 ~ 100 temperature, the heat treatment may be performed for 1 to 5 minutes at 100 ~ 200 temperature.

As a preferred embodiment of the present invention, the PTFE porous support heat-treated in three steps may have a volume of the occluded pores of 90% by volume or more relative to the total pore volume.

Another aspect of the present invention provides a composite electrolyte membrane for a fuel cell. The composite electrolyte membrane for a fuel cell includes a PTFE porous support including pores having a predetermined aspect ratio; And a fluorine ionomer solution containing hollow silica in the surface of the PTFE porous support and the pores of the support.

As a preferred embodiment of the present invention, the weight variation coefficient CV2 value of relation 2 may be 170% or more.

[Relationship 2]

Weight variation coefficient (CV2,%) = (Complex electrolyte membrane weight for fuel cell-PTFE porous support weight) / (PTFE porous support weight) × 100

In a preferred embodiment of the present invention, the volume of the pores occluded in the PTFE porous support may be greater than 90% by volume relative to the total pore volume.

As a preferred embodiment of the present invention, the aspect ratio may be 1: 5 to 15.

In a preferred embodiment of the present invention, the fluorine-based ionomer may include one or more selected from the group consisting of Nafion, Flemion, and Aciplex.

Another aspect of the invention provides a method of manufacturing a membrane-electrode assembly. The method of manufacturing the membrane-electrode assembly may include preparing a composite electrolyte membrane for a fuel cell by the manufacturing method of the composite electrolyte membrane for a fuel cell of the present invention; And a catalyst layer and a gas diffusion layer on both surfaces of the composite electrolyte membrane for a fuel cell.

Another aspect of the invention provides a method of manufacturing a fuel cell. The fuel cell manufacturing method includes the steps of manufacturing the membrane-electrode assembly through the method of manufacturing the membrane-electrode assembly of the present invention; Forming an electricity generating unit including a membrane-electrode assembly and a separator, the electricity generating unit generating electricity through an electrochemical reaction between a fuel and an oxidant; Forming a stack between the membrane and the electrode assembly through a separator; Forming a fuel supply unit supplying fuel to the electricity generation unit; And forming an oxidant supply unit for supplying an oxidant to the electricity generating unit. It includes.

Another aspect of the invention provides a fuel cell. The fuel cell includes a membrane-electrode assembly and a separator of the present invention, the electricity generating unit for generating electricity through the electrochemical reaction of the fuel and the oxidant; A fuel supply unit supplying fuel to the electricity generation unit; And an oxidant supply unit for supplying an oxidant to the generator. It includes.

According to the present invention, a composite electrolyte membrane for a fuel cell, a membrane-electrode assembly including the same, a fuel cell including the same, and a method for manufacturing the same have a simplified structure and have an effect of improving interface characteristics. In addition, it is possible to improve the performance of the fuel cell by preventing the delay of delivery of hydrogen ions and improving mechanical properties.

According to the composite electrolyte membrane for a fuel cell, a membrane-electrode assembly including the same, and a manufacturing method of a fuel cell including the same, the manufacturing process can be simplified.

1 is a schematic diagram of a membrane-electrode assembly according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to describe the present invention in more detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Like numbers refer to like elements throughout.

The method for manufacturing a composite electrolyte membrane for a fuel cell according to an embodiment of the present invention includes the steps of uniaxially stretching a PTFE sheet, two stages of biaxially stretching the uniaxially stretched PTFE sheet, and sintering the biaxially stretched PTFE sheet. 3 to form a PTFE porous support, 4 steps of impregnating the sintered PTFE porous support with a fluorine-based ionomer solution containing hollow silica, and 5 steps of drying and heat-treating the impregnated PTFE porous support.

In the first step, the polytetrafluoroethylene (PTFE) sheet is uniaxially stretched.

In addition, the PTFE sheet, (1) forming a paste containing a PTFE fine powder and a lubricant, (2) the step of ripening the paste, compressing the aged paste to produce a PTFE block (3) (4) pressing and extruding the PTFE block, (5) removing the lubricant by drying the pressure-extruded PTFE, and stretching (6) the PTFE sheet from which the lubricant is removed.

The average particle diameter of the PTFE powder in step (1) may be 300 ~ 5700 ㎛ but is not limited thereto. The lubricant is a liquid lubricant, in addition to hydrocarbon oils such as liquid paraffin, naphtha, white oil, toluene, xylene, various alcohols, ketones, esters and the like can be used. The lubricant may include 10 to 20 parts by weight of the lubricant, and more preferably 13 to 17 parts by weight, based on 100 parts by weight of the PTFE fine powder. When the lubricant is less than 10 parts by weight based on 100 parts by weight of the PTFE fine powder, the porosity may be lowered when forming the PTFE porous support by the biaxial stretching process described below, and when the amount exceeds 20 parts by weight, the pore size when the PTFE porous support is formed. It may increase the strength of the electrolyte membrane.

In the step (2), the paste may be aged at a temperature of 50 to 90 for 10 to 15 hours, more preferably at 11 to 13 hours at a temperature of 60 to 80. When the aging temperature is less than 50 or the aging time is less than 10 hours, the elongation of the PTFE sheet may be limited during biaxial stretching described below. In addition, when the aging temperature exceeds 90 or the aging time exceeds 15 hours, the size of the pores increases when the PTFE porous support is formed, thereby weakening the strength of the electrolyte membrane.

In step (3), the paste is compressed to produce a PTFE block using a paste.

In the step (4), the PTFE block may be pressurized at 400 to 800 psi pressure, and more preferably at 500 to 700 psi pressure. At this time, when the pressure to extrude the PTFE is less than 400 psi, the size of the pores increases when the PTFE porous support is formed, and thus the strength of the electrolyte membrane may be weakened. When the pressure exceeds 800 psi, the PTFE porous support is formed by a biaxial stretching process described below. Porosity can be lowered during formation.

In the first step, the uniaxial stretching may specifically be carried out in the longitudinal direction by using a speed difference between rollers in which a common PTFE sheet is transferred through a roller. However, the present invention is not limited thereto and may be stretched according to the stretching method used in manufacturing a conventional sheet.

Strain ratio in the longitudinal direction may be 1: 1.1 to 2. If the strain ratio in the longitudinal direction is less than 1: 1.1, the pore size of the PTFE porous support formed by biaxial stretching is small, so that the impregnation amount of the fluorine-based ionomer described later may be limited. In addition, when the strain ratio in the longitudinal direction exceeds 2, the thickness of the uniaxial stretched sheet may be difficult to give a thickness gradient. In addition, the stretching temperature may be 150 ~ 250 ℃ but is not limited thereto.

The uniaxially stretched PTFE sheet is biaxially stretched in two steps. At this time, as described above, the biaxial stretching process is performed at a draw ratio different from the uniaxial stretching. As a result, the pores of the biaxially stretched PTFE porous support have a predetermined aspect ratio. Therefore, when the composite electrolyte membrane for a fuel cell according to an embodiment of the present invention is applied to the membrane-electrode assembly, the direction of the major axis of the pores is arranged to be the direction of the transfer of hydrogen ions, that is, the direction of the current, so that the hydrogen ions in the major axis direction The transmission power is improved. Thus, battery characteristics can be improved.

Biaxial stretching may be performed in a direction perpendicular to the uniaxial stretching. Biaxial stretching, like uniaxial stretching, is also carried through the rollers and can be stretched laterally using the speed difference between the rollers. However, the present invention is not limited thereto and may be stretched according to the stretching method used in manufacturing a conventional sheet. Strain ratio in the transverse direction may be 1: 6 to 30. If the strain ratio in the transverse direction is less than 1: 6, the effect of improving hydrogen ion transfer force may be insignificant as the aspect ratio of the pores of the PTFE porous support decreases. In addition, when the strain ratio in the transverse direction exceeds 30, the fibrils and node structures of the transversely stretched sheet may be destroyed.

As a result, the uniaxial draw ratio: biaxial draw ratio may be 1: 5 to 15, more preferably 1: 8 to 12.

Further, in the present invention, the processes of uniaxially stretching in the longitudinal direction and biaxially stretching in the transverse direction may be performed regardless of the order of each other.

In step 3, the biaxially stretched PTFE sheet is sintered to form a PTFE porous support. As the sintering process is performed, the strength of the PTFE porous support may be improved. In this case, the sintering process may be performed at a temperature of 250 to 450, and more preferably at a temperature of 300 to 400 ℃. When the sintering temperature is less than 250 ° C, the strength of the PTFE porous support may be lowered, and when the sintering temperature is higher than 400 ° C, the sintering effect may be reduced due to the temperature increase.

The average pore size of the PTFE porous support on which the biaxial stretching process is performed may be 0.10 to 0.50 μm, more preferably 0.20 to 0.40 μm, and a porosity of 60 to 90%, more preferably 80 to 85%. When the average pore size of the PTFE porous support is less than 0.10 μm or the porosity is less than 60%, the degree of impregnation of the fluorine ionomer solution into the pores may be limited. In addition, when the average pore size exceeds 0.50 μm or the porosity exceeds 90%, the PTFE porous support structure may be deformed when the fluorine-based ionomer solution is impregnated in the four-step process described later.

In step 4, the sintered PTFE porous support is impregnated with a fluorine-based ionomer solution containing hollow silica. Thus, the fluorine ionomer solution is filled in the pores of the PTFE porous support. At this time, the hollow silica is included in the fluorine-based ionomer solution to improve the absorption of the PTFE liquid. On the contrary, when the fluorine-based ionomer solution does not contain hollow silica, the PTFE has a limited absorption ability to the fluorine-based ionomer solution. Thus, the amount of fluorine-based ionomer solution that can be impregnated is limited, and the liquid retention in the PTFE porous support of the fluorine-based ionomer solution is poor. That is, the inclusion of the hollow silica in the fluorine-based ionomer solution can increase the amount of the fluorine-based ionomer solution that can be impregnated in the PTFE porous support and improve the liquid retention after impregnation.

In addition, in the case of the hollow silica, it is possible to prevent the volume expansion of the PTFE porous support due to the impregnation of the fluorine-based ionomer solution, as well as improving the absorbency. As a result, by including the hollow silica in the fluorine-based ionomer solution it is possible to improve the absorption of the fluorine-yeonomer solution to the PTFE porous support, and to suppress the volume expansion of the PTFE porous support.

The hollow silica is spherical, the average particle diameter may be 10 ~ 300 nm, more preferably 10 ~ 100 nm. Here, the particle diameter means the diameter when the shape of the hollow silica is spherical, and the maximum distance of the linear distance from one point to the other on the hollow silica surface when the shape is not spherical. When the average particle diameter of the hollow silica is less than 10 nm, as the capacity for supporting the fluorine ionomer solution decreases, the absorption capacity of the fluorine ionomer solution may be limited, and when the average diameter exceeds 300 nm, the PTFE porous support The amount of the hollow silica impregnated in the pores may be limited.

The hollow part included in the hollow silica may be a space in which the fluorine-based ionomer solution adsorbed and moved through the shell part may be supported. Preferably, the hollow diameter may be 5 to 100 nm, and more preferably 5 to 50 nm. . If the hollow diameter is less than 5 nm, the amount of the fluorine-based ionomer solution supported may be reduced. If the hollow diameter exceeds 100 nm, the particle size of the hollow silica may be larger than the desired range or may cause the shell to collapse.

The fluorine ionomer solution may further include at least one hygroscopic agent selected from the group consisting of zeolite, titania, zirconia, and montmorillonite. When the moisture absorbent is further included, the amount of fluorine-based ionomer solution impregnation on the PTFE porous support may be further increased.

The fluorine-based ionomer may include one or more selected from the group consisting of Nafion, Flemion, and Aciplex, and more preferably Nafion.

The hollow silica may include 0.05 to 5 parts by weight, and more preferably 1 to 3 parts by weight, based on 100 parts by weight of the fluorine-based ionomer solution. If less than 0.05 part by weight of hollow silica is included with respect to 100 parts by weight of the fluorine-based ionomer solution, the impregnating effect of the fluorine-based ionomer solution may be insignificant. The flow of current can be lowered when applied to electrode assemblies.

In step 5, the PTFE porous support impregnated with the fluorine ionomer solution is dried and heat treated. As the drying and heat treatment processes are performed, the liquid retention property of the impregnated fluorine-based ionomer solution may be improved, and the adhesion to the electrode may be improved when the membrane-electrode assembly is manufactured.

In this case, the drying may be performed for 1 to 30 minutes at a temperature of 60 to 100, and the heat treatment may be performed for 1 to 5 minutes at a temperature of 100 to 200. When the temperature of the drying process is less than 60 ℃ the liquid-retaining property of the fluorine-based ionomer solution impregnated in the PTFE porous support may be lowered, and if it exceeds 100 ℃ may be reduced adhesion to the electrode when manufacturing the membrane-electrode assembly have. In addition, when the heat treatment temperature is less than 100 ℃ or less than 1 minute in the heat treatment process, the liquid-retaining property of the fluorine-based ionomer solution impregnated in the PTFE porous support may be lowered, the temperature exceeds 200 or the time exceeds 5 minutes In this case, adhesion to the electrode may be reduced when the membrane-electrode assembly is manufactured.

After step 5, the volume of pores occluded in the PTFE porous support may be greater than 90% by volume relative to the total pore volume.

The composite electrolyte membrane for a fuel cell may have a thickness variation coefficient (CV1) value of the relational expression 1 below 15%, and a weight variation coefficient CV2 value of the relational expression 2 below 170% or more.

[Relationship 1]

Thickness variation coefficient (CV1,%) = (Composite electrolyte membrane thickness for fuel cell-PTFE porous support thickness / PTFE porous support thickness) × 100

[Relationship 2]

Weight variation coefficient (CV2,%) = (Complex electrolyte membrane weight for fuel cell-PTFE porous support weight) / (PTFE porous support weight) × 100

The thickness variation coefficient is one of the indexes for estimating the volume expansion of the PTFE porous support before and after impregnating the PTFE porous support with a fluorine-based ionomer solution. Able to know.

In addition, the weight variation coefficient is one of the indicators for measuring the weight change of the PTFE porous support before and after the impregnation of the fluorine-based ionomer solution in the PTFE porous support, the larger the value of the fluorine ionomer impregnated in the PTFE porous support It can be seen that the impregnation amount is increased.

In the composite electrolyte membrane for a fuel cell according to the present invention, the thickness variation coefficient satisfies 15% or less, indicating that the volume expansion degree is low even after the fluorine-based ionomer is impregnated in the PTFE porous support.

In addition, the composite electrolyte membrane for a fuel cell according to the present invention can be seen that the impregnation amount of the fluorine-based ionomer solution impregnated in the PTFE porous support by satisfying the weight variation coefficient of 170% or more.

Therefore, it can be seen that the composite electrolyte membrane for a fuel cell according to the present invention has a low volume expansion degree and a high impregnation amount of the fluorine-based ionomer solution.

Therefore, the composite electrolyte membrane for a fuel cell according to an embodiment of the present invention is a fluorine-based ionomer solution comprising a PTFE porous support including pores having a predetermined aspect ratio, and hollow silica impregnated in the pores and the surface of the PTFE porous support. Include. Therefore, compared with the conventional electrolyte membrane for fuel cells, the structure is simplified, and the interface characteristics can be improved when bonded to the electrode. In addition, as the thickness of the electrolyte membrane becomes thin, hydrogen ion transfer delay can be prevented, and since the fluorine-based ionomer solution is impregnated into the PTFE porous support, the mechanical properties are excellent, thereby improving the performance of the fuel cell.

The aspect ratio may be 1: 5 to 15, more preferably 1: 7 to 12. When the aspect ratio is less than 1: 5, the current flowability may be decreased, and when the aspect ratio is greater than 1: 15, the strength of the electrolyte membrane may be lowered.

On the other hand, the membrane-electrode assembly according to an embodiment of the present invention includes the steps of preparing the composite electrolyte membrane for a fuel cell, and bonding the electrode including a catalyst layer and a gas diffusion layer on both sides of the fuel cell composite electrolyte membrane. .

1 is a schematic diagram of a membrane-electrode assembly according to an embodiment of the present invention.

Referring to FIG. 1, the membrane-electrode assembly according to an exemplary embodiment of the present invention includes an oxide electrode 20 and a reduction electrode 20 ′ positioned to face each other with a composite electrolyte membrane 10 for a fuel cell interposed therebetween. . In this case, the oxidation electrode 20 and the reduction electrode 20 'include gas diffusion layers 21 and 21', catalyst layers 22 and 22 ', and electrode substrates 23 and 23', respectively.

Detailed description of the composite electrolyte membrane for a fuel cell will be referred to the above description.

The anode 20 may include a gas diffusion layer 21 and an oxidation catalyst layer 22. The gas diffusion layer 21 may be provided to prevent rapid diffusion of fuel injected into the fuel cell and to prevent a decrease in ion conductivity. The gas diffusion layer 21 may control the diffusion rate of the fuel through heat treatment or electrochemical treatment. The gas diffusion layer 21 may be carbon fiber or carbon paper. Here, the fuel may be a liquid fuel such as formic acid solution, methanol, formaldehyde, or ethanol.

The oxidation catalyst layer 22 is a layer into which the catalyst is introduced, and may include a conductive support and an ion conductive binder (not shown). In addition, the oxidation catalyst layer 22 may include a main catalyst attached to the conductive support. The conductive support may be carbon black and the ion conductive binder may be a Nafion ionomer or a sulfonated polymer. In addition, the main catalyst may be a metal catalyst, for example, may be platinum (Pt).

The oxidation catalyst layer 22 may be formed using an electroplating method, a spray method, a painting method, a doctor blade method, or a transfer method.

The reduction electrode 20 ′ may include a gas diffusion layer 21 ′ and a reduction catalyst layer 22 ′. The gas diffusion layer 21 ′ may be provided to prevent sudden diffusion of the gas injected into the reduction electrode 20 ′ and to uniformly disperse the gas injected into the reduction electrode 20 ′. The gas diffusion layer 21 may be carbon paper or carbon fiber.

The reduction catalyst layer 22 ′ is a layer into which the catalyst is introduced, and may include a conductive support and an ion conductive binder (not shown). In addition, the reduction catalyst layer 22 ′ may include a main catalyst attached to the conductive support. The conductive support may be carbon black and the ion conductive binder may be a Nafion ionomer or a sulfonated polymer. In addition, the main catalyst may be a metal catalyst, for example, may be platinum (Pt).

The reduction catalyst layer 22 ′ may be formed using an electroplating method, a spray method, a painting method, a doctor blade method, or a transfer method.

The membrane-electrode assembly may be formed by placing and then fastening each of the anode electrode 20, the composite electrolyte membrane for fuel cell 10, and the cathode 20 ′, or may be formed by pressing them at high temperature and high pressure.

Bonding the electrodes 20 and 20 'to both surfaces of the composite electrolyte membrane 10 for a fuel cell may first apply a gas diffusion layer forming material to one surface of the composite electrolyte membrane 10 for a fuel cell, thereby forming a gas diffusion layer 21. 21 ').

The gas diffusion layers 21 and 21 ′ serve as current conductors between the composite electrolyte membrane 10 for fuel cells and the catalyst layers 22 and 22 ′, and serve as passages of reactant gases and water as products. Therefore, the gas diffusion layers 21 and 21 ′ may have a porous structure having a porosity of 20 to 90% to allow gas to pass therethrough. The thicknesses of the gas diffusion layers 21 and 21 'may be appropriately adopted as necessary, and may be, for example, 100 to 400 µm. When the thickness of the gas diffusion layers 21 and 21 'is 100 µm or less, the electrical contact resistance increases between the catalyst layer and the electrode substrate, and the structure may become unstable by compression. In addition, when the thickness of the gas diffusion layers 21 and 21 'exceeds 400 μm, it may be difficult to move the reactant gas.

The gas diffusion layers 21 and 21 ′ may be formed of a carbonaceous material and a fluorine resin. Carbonaceous materials include graphite, carbon black, acetylene black, denka black, kecheon black, activated carbon, mesoporous carbon, carbon nanotubes, carbon nanofibers, carbon nanohorns, carbon nanorings, carbon nanowires, and fullerenes (C60). And super P may include one or more selected from the group consisting of, but is not limited thereto. In addition, as a fluorine-type resin, the copolymer of polytetrafluoroethylene, polyvinylidene fluoride (PVdF), polyvinyl alcohol, cellulose acetate, polyvinylidene fluoride-hexafluoropropylene, or styrene-butadiene high part (SBR) It may include one or more selected from the group consisting of.

Next, catalyst layers 22 and 22 'are formed on the gas diffusion layers 21 and 21'. The catalyst layers 22, 22 '

The catalyst layers 22 and 22 'may be formed by applying a catalyst layer forming material on the gas diffusion layers 21 and 21'.

The catalyst layer forming material may be a metal catalyst or a metal catalyst supported on a carbon-based support. As the metal catalyst, at least one selected from the group consisting of platinum, ruthenium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, and platinum-transition metal alloy may be used. In addition, the carbon-based support, graphite (graphite), carbon black, acetylene black, denka black, kecheon black, activated carbon, mesoporous carbon, carbon nanotubes, carbon nanofibers, carbon nanohorn, carbon nano ring, carbon nano And at least one selected from the group consisting of wire, fullerene, and superP.

The electrode substrates 23 and 23 'may be a conductive substrate selected from the group consisting of carbon paper, carbon cloth, and carbon felt, but are not limited thereto, and may be a cathode electrode material or an anode electrode material applicable to a polymer electrolyte fuel cell. Are all available. The electrode substrate may be formed through a conventional deposition method, and after forming the catalyst layers 22 and 22 'on the electrode substrates 23 and 23', the catalyst layers on the gas diffusion layers 21 and 21 'are formed. 22 and 22 'and the gas diffusion layers 21 and 21' may be disposed to be in contact with each other.

On the other hand, the fuel cell according to an embodiment of the present invention is at least one electricity generating unit for generating electrical energy through the oxidation reaction of the fuel and the reduction reaction of the oxidant, and the fuel for supplying the above-described fuel to the electricity generating unit It comprises a supply part and an oxidant space | gap part which supplies an oxidant to the said electricity generating part.

The membrane-electrode assembly may include one or more, and separators for supplying fuel and an oxidant are disposed at both ends of the membrane-electrode assembly to constitute an electricity generator. At least one of the electricity generating units may be assembled to form a stack.

At this time, the arrangement or manufacturing method of the fuel cell can be formed without limitation as long as it is applicable to the polymer electrolyte fuel cell, it can be variously applied with reference to the prior art.

Hereinafter, preferred examples will be presented to aid in understanding the present invention. However, the following examples are only for the understanding of the present invention, and the present invention is not limited to the following experimental examples.

Preparation Example-Preparation of PTFE Sheet

After mixing and blending 15 parts by weight of the liquid lubricant with respect to 100 parts by weight of PTFE fine powder and aged at 70 for 12 hours, a block was prepared using a molding jig.

After the block was put in an extrusion mold, pressure extrusion was carried out under a pressure of 600 psi, the sheet was rolled to a thickness of 0.3t through a rolling roll, and a lubricant was removed through a drying process to prepare a PTFE sheet.

<Example 1>

The PTFE sheet prepared in the preparation example was biaxially stretched with a longitudinal stretch ratio: transverse stretch ratio = 1: 10, and then sintered at 360 to prepare a PTFE porous support. The PTFE porous support prepared by the above method had a maximum pore size of 0.51 μm, an average pore size of 0.35 μm, and a porosity of 82%.

Next, the PTFE porous support was fixed on the PET film, and 1 part by weight of a spherical hollow silica with an average particle diameter of 50 nm was applied to 100 parts by weight of Nafion, a fluorine ionomer, by applying a Nafion solution at a temperature of 80 minutes for 10 minutes. Was dried in a vacuum oven, and heat treated for 3 minutes at a temperature of 160 to prepare a transparent electrolyte membrane for a fuel cell having a thickness of 20 μm.

<Examples 2 to 5>

Prepared under the same conditions as in Example 1, the composite electrolyte membrane for a fuel cell was prepared by varying the longitudinal axis draw ratio: transverse axis draw ratio, the average particle diameter of the hollow silica, and the content of the hollow silica as shown in Table 1 below.

Comparative Example 1

The composite electrolyte membrane for a fuel cell was manufactured under the same conditions as in Example 1, but using a Nafion solution containing no hollow silica in the fluorine ionomer solution.

Comparative Example 2

Prepared under the same conditions as in Example 1, in the fluorine-based ionomer solution, a composite electrolyte membrane for a fuel cell was prepared by including silica in the Nafion solution in the same content as the hollow silica.

Experimental Example 1-Tensile Strength

The tensile strengths in the longitudinal and transverse directions of Preparation Examples 1 to 5 and Comparative Examples 1 and 2 are shown in Table 1 below.

Experimental Example 2-Thickness variation coefficient

Ten thicknesses were measured in the biaxial directions of the PTFE porous support prepared in Preparation Examples 1 to 5 and Comparative Examples 1 and 2 and the composite electrolyte membrane for the fuel cell, and the average value of the thickness values of the ten points was measured at the following thickness variation coefficient. It was calculated by the following relational formula 1 by applying as a value.

Thickness variation coefficient (CV1,%) = (Composite electrolyte membrane thickness for fuel cell-porous PTFE support thickness / porous PTFE support thickness) × 100

Experimental Example 3-Weight Variation Factor

The weight of the PTFE porous support prepared in Preparation Examples 1 to 5, Comparative Examples 1 and 2 and the composite electrolyte membrane for a fuel cell was measured and calculated through the following Equation 2.

Weight variation coefficient (CV2,%) = (Compound electrolyte membrane weight for fuel cell-weight of porous PTFE support) / (porous PTFE support weight) × 100

division	Whether hollow silica is included	Longitudinal Drawing Ratio: Horizontal Drawing Ratio	Hollow Silica Average Particle Size (nm)	Hollow silica content (parts by weight) with respect to 100 parts by weight of ionomer solution	The tensile strength		Thickness variation coefficient (CV1)	Weight variation coefficient (CV2)
					Longitudinal direction	Transverse
Example 1	○	1: 10	50	One	◎	◎	5	265
Example 2	○	1: 10	50	3	◎	◎	4	268
Example 3	○	1: 7	50	One	◎	◎	5	271
Example 4	○	1: 11	50	One	◎	⊙	6	282
Example 5	○	1: 5	50	One	◎	○	10	200
Example 6	○	1: 14	50	One	○	○	14	220
Example 7	○	1: 10	350	One	○	◎	15	171
Comparative Example 1	×	1: 10	50	One	◎	○	50	130
Comparative Example 2	×	1: 10	50	One	◎	○	28	160
◎: Very good,: Excellent,: Good,: Bad,: Very bad

Referring to Table 1, it can be seen that Examples 1 to 5 including hollow silica as an adsorbent show high weight variation coefficient characteristics compared to Comparative Examples 1 to 2. Therefore, it can be seen that the composite electrolyte membrane for a fuel cell according to an embodiment of the present invention can retain a larger amount of electrolyte as it includes hollow silica.

As mentioned above, although the present invention has been described in detail with reference to preferred examples and experimental examples, the present invention is not limited to the above examples and experimental examples, and has ordinary knowledge in the art within the spirit and scope of the present invention. Many modifications and variations are possible.

Claims (22)

1. A step of forming a PTFE porous support comprising pores having a predetermined aspect ratio;

   Impregnating the PTFE porous support with a fluorine-based ionomer solution containing hollow silica; And

   Drying and heat-treating the impregnated PTFE porous support; Method for producing a composite electrolyte membrane for a fuel cell comprising a.
2. The method of claim 1,

   The composite electrolyte membrane for a fuel cell has a thickness variation coefficient (CV1) value of 15% or less in the following relation 1, and a weight variation coefficient (CV2) value of the following formula 2 has a 170% or more composite electrolyte membrane for a fuel cell.

   [Relationship 1]

   Thickness variation coefficient (CV1,%) = (Composite electrolyte membrane thickness for fuel cell-PTFE porous support thickness / PTFE porous support thickness) × 100

   [Relationship 2]

   Weight variation coefficient (CV2,%) = (Complex electrolyte membrane weight for fuel cell-PTFE porous support weight) / (PTFE porous support weight) × 100
3. The method of claim 1,

   The average pore size of the PTFE porous support of the first step is 0.10 ~ 0.50 ㎛, porosity of 60 ~ 90% of the manufacturing method of a composite electrolyte membrane for a fuel cell.
4. The method of claim 1,

   The PTFE porous support is formed by sintering a biaxially stretched PTFE sheet,

   In the biaxial stretching, the uniaxial stretching ratio and the biaxial stretching ratio is 1: 5 to 15 manufacturing method of a composite electrolyte membrane for a fuel cell.
5. The method of claim 4, wherein

   The sintering process of the first step is a method of manufacturing a composite electrolyte membrane for a fuel cell is carried out at a temperature of 250 ~ 450 ℃.
6. The method of claim 4, wherein

   The PTFE sheet,

   Forming a paste including 10 to 20 parts by weight of lubricant based on 100 parts by weight of PTFE fine powder;

   Aging the paste at a temperature of 50-90 ° C. for 10-15 hours;

   Compressing the aged paste in a compressor to produce a PTFE block;

   Pressing and extruding the PTFE block at a pressure of 400 to 800 psi to form a PTFE sheet by calendering; And

   Drying the PTFE sheet to remove the lubricant; And

   A method of manufacturing a composite electrolyte membrane for a fuel cell comprising the step of stretching the sheet from which the lubricant is removed.
7. The method of claim 1,

   The hollow silica is spherical, the average particle diameter is 10 ~ 300 nm, the diameter of the hollow 5 ~ 100 nm manufacturing method of a composite electrolyte membrane for a fuel cell.
8. The method of claim 1,

   The fluorine-based ionomer solution is a method for producing a composite electrolyte membrane for a fuel cell containing 0.05 to 5 wt% hollow silica.
9. The method of claim 1,

   The fluorine-based ionomer is a method for producing a composite electrolyte membrane for a fuel cell comprising at least one selected from the group consisting of Nafion, Flemion, and Aciplex.
10. The method of claim 1,

    The fluorine-based ionomer solution further comprises at least one moisture absorbent selected from the group consisting of zeolite, titania, zirconia, and montmorillonite.
11. The method of claim 1,

    The drying of the third step is performed for 1 to 30 minutes at 60 to 100 temperature, the heat treatment is carried out for 1 to 5 minutes at 100 to 200 temperature method of manufacturing a composite electrolyte membrane for a fuel cell.
12. The method of claim 1,

    The PTFE porous support subjected to the heat treatment in three steps has a volume of the occluded pores of 90% by volume or more based on the total pore volume of the composite electrolyte membrane for a fuel cell.
13. A PTFE porous support comprising pores having a predetermined aspect ratio; And

    And a fluorine-based ionomer solution containing hollow silica in the pores of the support and the surface of the PTFE porous support.
14. The method of claim 13,

    A composite electrolyte membrane for a fuel cell having a weight variation coefficient (CV2) value of the relation 2 below.

    [Relationship 2]

    Weight variation coefficient (CV2,%) = (Complex electrolyte membrane weight for fuel cell-PTFE porous support weight) / (PTFE porous support weight) × 100
15. The method of claim 13,

    The volume of pores occluded in the PTFE porous support is 90% by volume or more based on the total pore volume of the composite electrolyte membrane for a fuel cell.
16. The method of claim 13,

    The aspect ratio is 1: 5 to 15 composite electrolyte membrane for a fuel cell.
17. The method of claim 13,

    The fluorine-based ionomer is a method for producing a composite electrolyte membrane for a fuel cell comprising at least one selected from the group consisting of Nafion, Flemion, and Aciplex.
18. A method of manufacturing a composite electrolyte membrane for a fuel cell according to any one of claims 1 to 12, the method comprising: preparing a composite electrolyte membrane for a fuel cell; And

    Bonding electrodes including a catalyst layer and a gas diffusion layer to both surfaces of the fuel cell composite electrolyte membrane; Method of producing a membrane-electrode assembly comprising a.
19. Manufacturing a membrane-electrode assembly through the method of manufacturing the membrane-electrode assembly of claim 18;

    Forming an electricity generating unit including a membrane-electrode assembly and a separator, the electricity generating unit generating electricity through an electrochemical reaction between a fuel and an oxidant;

    Forming a stack between the membrane and the electrode assembly through a separator;

    Forming a fuel supply unit supplying fuel to the electricity generation unit; And

    Forming an oxidant supply unit for supplying an oxidant to the electricity generating unit; Fuel cell manufacturing method comprising a.
20. The composite electrolyte membrane for a fuel cell according to claim 13; And

    Electrodes bonded to both surfaces of the composite electrolyte membrane for a fuel cell and including a catalyst layer and a gas diffusion layer; Membrane-electrode assembly comprising a.
21. The method of claim 20,

    The PTFE porous support is a membrane-electrode assembly disposed so that the major axis of the pores toward the direction of the current flowing between the electrodes.
22. 22. An electric generator comprising the membrane-electrode assembly and the separator of any one of claims 20 to 21, the electric generator generating electricity through an electrochemical reaction between a fuel and an oxidant;

    A fuel supply unit supplying fuel to the electricity generation unit; And

    An oxidant supply unit for supplying an oxidant to the generator; Fuel cell comprising a.

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