WO2014189177A1 - Mesh-type separator for fuel cell and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a mesh-type separator for a fuel cell and a manufacturing method thereof, and more specifically, to a mesh-type separator for a fuel cell, having excellent flexural strength and electric conductivity, comprising, as main components, two types of blends having different mixing ratios of a thermoplastic resin or a thermosetting resin to a conductive carbon material, and a manufacturing method thereof. The present invention provides a mesh-type separator for a fuel cell, with excellent flexural strength and electric conductivity, which can embody a low-weight thin plate at a low cost without using a particular polymeric material and an expensive conductive carbon material.

Description

Mesh type separator for fuel cell and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mesh type separator for fuel cells and a method of manufacturing the same. More specifically, both the bending strength and the electrical conductivity are mainly composed of two kinds of blends having different mixing ratios of thermoplastic resins or thermosetting resins and conductive carbon materials. The present invention relates to a separator for a fuel cell having an excellent mesh structure and a method of manufacturing the same.

A fuel cell is an electrochemical device that directly converts chemical energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol, and natural gas into electrical energy. The energy conversion process of a fuel cell is very efficient and environmentally friendly. Because of this, interest continues to be in recent years.

In general, the fuel cell is a phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid oxide fuel cell (SOFC), polymer electrolyte fuel cell (PEMFC) and alkali type depending on the type of electrolyte used It is classified into a fuel cell (AFC) and the like. Each of these fuel cells operates on essentially the same principle, but differs in the type of fuel used, operating temperature, catalyst, and electrolyte. Among them, the polymer electrolyte fuel cell is known to be most promising not only for small stationary power generation equipment but also for transportation systems, and membrane electrode assemblies and separators including the polymer electrolyte membrane are the core parts. Is actively underway.

In a typical polymer electrolyte fuel cell, a membrane electrode assembly including a polymer electrolyte membrane provided between an anode and a cathode is interposed therebetween, and a separator plate having a hydrogen flow path and a separator plate having an oxygen flow path are disposed on both sides thereof. The unit cell is formed, and the unit cells are formed by stacking dozens or hundreds of unit cells. Among the fuel cell components, the separator plate must have excellent electrical conductivity as well as gas impermeability such as hydrogen and oxygen. When used for transportation, such as fuel cells, it must have high mechanical strength to withstand various shocks and vibrations. In addition, it is also known to realize a low cost process through low weight thinning of the separator, which accounts for about 80% of the weight of the fuel cell.

To this end, conventionally, a polymer electrolyte fuel cell having good moldability, electrical conductivity, and mechanical strength without forming a carbonization process and a cutting process by molding a raw material containing graphite particles having a predetermined average particle diameter in a range and thermosetting resin or non-carbonaceous resin is removed. Although the plate was manufactured, there was a limit in improving the trade-off relationship between electrical conductivity and mechanical strength (bending strength) depending on the mixing ratio of the raw materials (Patent Documents 1 and 2).

In addition, as a prior art related to the thinning of the separator, a content of a fuel cell separator is molded from a conductive curable resin composition composed of a hydrocarbon compound having several carbon-carbon double bonds, an elastomer and a carbonaceous material (Patent Document 3). Excellent contact resistance by using a conductive resin composition in which powder, fiber, or a conductive material mixed with powder and fiber is mixed with a multicomponent polymer resin binder having a number average particle size of 0.1 to 2 μm in a dispersed phase. Although a technique for manufacturing a separator for a battery is also known (Patent Document 4), all of these prior arts not only select a specific polymer resin as a molding material of a thin plate separator, but also carbon fine powder, carbon nanotubes, and usually 10-20. A conductive material in the form of microparticles such as carbon fiber having a length of μm is selected. It is not easy to select the molecular material, and sufficient bending strength cannot be obtained by using only a microm fine conductive material, and when the thin plate is manufactured, the fine powder conductive material itself is expensive, so Due to the rise, there is a problem that it is difficult to realize a low-cost process.

Patent Document 1. Japanese Patent Application Laid-Open No. 2001-335695

Patent Document 2. Korea Patent Registration No. 10-0485285

Patent Document 3. Korean Patent Publication No. 10-2007-0110531

Patent Document 4. Korean Patent No. 10-0798121

Therefore, the present invention has been devised in view of the above problems, and an object of the present invention is to realize low-cost thin weight thinning without using a specific polymer material and expensive conductive carbon material, and to have excellent flexural strength and electrical conductivity. The present invention is to provide a separator plate for a fuel cell having a mesh structure and a method of manufacturing the same, comprising two kinds of blends having different blending ratios of thermoplastic resins or thermosetting resins and conductive carbon materials.

The present invention for achieving the above object, there is provided a mesh-type separator for fuel cells comprising a thermoplastic resin or a thermosetting resin, and two kinds of blends different in the mixing ratio of the conductive carbon material.

The thermoplastic resin is polyethylene, polypropylene, polymethyl methacrylate, polybutylene terephthalate, polyamide, polyimide, polycarbonate, polyvinylidene fluoride, polyether sulfone, polyether ether ketone, polyphenylene sulfide, And it is characterized in that any one selected from the group consisting of polybenzimidazole.

The thermosetting resin is characterized in that any one selected from the group consisting of phenol resin, epoxy resin, urea resin, melamine resin, unsaturated polyester resin, polycarbodiimide resin, perryl alcohol resin, and alkyd resin.

The conductive carbon material is characterized in any one selected from the group consisting of natural graphite, artificial graphite, expanded graphite, carbon black, carbon fiber, carbon nanotubes, amorphous carbon, and mixtures thereof.

The blending ratio of the thermoplastic resin or the thermosetting resin and the conductive carbon material is characterized in that 10:90 ~ 60:40.

In addition, the present invention comprises the steps of: i) kneading each of the two kinds of raw materials differing in the mixing ratio of the thermoplastic resin or the thermosetting resin and the conductive carbon material; ii) injecting two kinds of raw materials having different mixing ratios in step i) into a mold in a mesh form and pressing to form a sheet; And iii) inserting the sheet formed in step ii) into a mold having a flow path and compressing the sheet.

In the step ii) the process of putting in the mold is characterized in that it is carried out in a width of 5 ~ 20 mm in the form of a mesh using an automatic powder injection device.

The sheet formed in step ii) is characterized in that the thickness of 0.05 ~ 1.5 mm.

The sheet formed in step ii) is characterized in that the laminated structure of 2-3 layers.

The mold of step iii) is characterized in that a wavy flow path having a concave portion and a convex portion is formed by a stamping process.

Compression molding of step iii) is characterized in that it is carried out for 1 to 5 minutes at a pressure of 1,000 ~ 2,000 kgf / cm ² , a temperature of 150 ~ 170 ℃.

According to the present invention, it is possible to provide a fuel cell mesh separation plate for fuel cell, which realizes low-cost low-weight thinning and excellent flexural strength and electrical conductivity without using a specific polymer material and expensive conductive carbon material.

1 is a conceptual diagram of a mesh type separator for fuel cells according to the present invention.

2 is an explanatory diagram of (a) surface direction and (b) vertical direction of a mesh type separator for fuel cell according to the present invention;

Figure 3 is a mesh separator for a fuel cell prepared from Example 1 of the present invention.

Figure 4 is a graph showing the electrical conductivity average value, maximum value, minimum value of the mesh type separator for fuel cells prepared from Example 2 of the present invention and the separators prepared from Comparative Examples 1 and 2 [(a) Comparative Example 1 average value, (b) Example 2 maximum value, (c) Example 2 average value, (d) Example 2 minimum value, (e) Comparative example 2 average value].

Figure 5 is a graph showing the electrical conductivity characteristics of 17 parts of the surface of the separator plate prepared from the fuel cell mesh separator and Comparative Examples 1, 2 prepared from Example 2 of the present invention.

Hereinafter, a mesh type separator for fuel cells comprising two kinds of blends having different blending ratios of thermoplastic resins or thermosetting resins and conductive carbon materials will be described in detail with reference to the accompanying drawings.

In general, a separator for a fuel cell is formed by mixing a polymer resin and graphite particles. When a polymer resin is mixed to reinforce flexural strength, the flexural strength is excellent, but electrical conductivity and thermal conductivity tend to be inferior. When operating a fuel cell with a plate, it sometimes happens that it can't beat the heat. On the other hand, when a large amount of conductive carbon materials such as black string particles are mixed, the electric conductivity and the thermal conductivity are excellent, but the flexural strength is reduced, so that when the external shock or vibration is broken or cracks are generated, hydrogen or oxygen leaks.

However, in the present invention, unlike the conventional molding of a fuel cell separator using only one type of raw material which differs only in the mixing ratio of polymer resin and graphite particles, two kinds of thermoplastic resin or thermosetting resin and conductive carbon material have different mixing ratios. The above problem, that is, the trade-off relationship between bending strength and electrical conductivity, was solved by forming a separator using a blend of as a raw material and having the mesh structure.

1 is a conceptual diagram of a mesh type separator for fuel cells according to the present invention, and two kinds of raw materials A having different mixing ratios (higher carbon materials than B) and B (lower carbon contents than A) ), And the blend is capable of forming a mesh-type separator plate in which A and B mesh structures are combined by inputting A and B raw materials in a mesh form into a mold prepared in advance.

Accordingly, the present invention provides a mesh type separator for fuel cell comprising a thermoplastic resin or a thermosetting resin and two blends having different blending ratios of conductive carbon materials. In the present invention, either a thermoplastic resin or a thermosetting resin can be used as the polymer resin that is the main raw material of the separator for fuel cell.

Examples of the thermoplastic resin include polyethylene, polypropylene, polymethyl methacrylate, polybutylene terephthalate, polyamide, polyimide, polycarbonate, polyvinylidene fluoride, polyether sulfone, polyether ether ketone, polyphenylene sulfide, And polybenzimidazole, any one selected from the group consisting of can be used without limitation.

The thermosetting resin may be any one selected from the group consisting of phenol resins, epoxy resins, urea resins, melamine resins, unsaturated polyester resins, polycarbodiimide resins, perperyl alcohol resins, and alkyd resins. The phenol resin usually used in the production of separator plates for fuel cells can be used more preferably.

In addition, the conductive carbon material may be used without particular limitation as long as the carbon material exhibits conductivity. Among them, graphite is easily available and inexpensive, and may be used regardless of the type of graphite. Any one of graphite or expanded graphite may be used, and any one selected from the group consisting of carbon black, carbon fiber, carbon nanotubes, amorphous carbon, and mixtures thereof may be used.

When the blending ratio of the thermoplastic resin or the thermosetting resin and the conductive carbon material is 10:90 to 60:40, when the two kinds of blends having different blending ratios within the range are used as raw materials, both the electrical conductivity and the flexural strength are used. It is preferable to obtain an excellent separator, and the mixing ratio can be adjusted in consideration of the characteristics of the separator within the above range.

Figure 2 is a diagram illustrating the electrical flow in the (a) surface direction and (b) vertical direction of the mesh type separator for fuel cell according to the present invention, the content of the carbon material compared to the two kinds of raw materials A (B) different in the mixing ratio High), B (lower carbon content than A) into mesh form, and then into the mold to form a mesh-type separating plate in which A and B mesh structures are combined. It shows that the electrical conductivity is high in the part with the raw material A, and also excellent in the conductivity with the raw material A in the vertical direction.

In addition, the present invention comprises the steps of: i) kneading each of the two kinds of raw materials differing in the mixing ratio of the thermoplastic resin or the thermosetting resin and the conductive carbon material; ii) injecting two kinds of raw materials having different mixing ratios in step i) into a mold in a mesh form and pressing to form a sheet; And iii) inserting the sheet formed in step ii) into a mold having a flow path and compressing the sheet.

The thermoplastic resin or thermosetting resin, the conductive carbon material, and the blending ratio of step i) are as described above, and as the raw material of the separator, other than the thermoplastic resin or the thermosetting resin, and the conductive carbon material, glass fibers, etc. Reinforcing materials and release agents may also be added.

In step ii), two kinds of raw materials kneaded in step i) are added in a mesh form using an automatic powder input device, and the width of the powder is preferably 5-20 mm. If the width is less than 5 mm, it is difficult to maintain the mesh form made of two kinds of raw materials in which the raw materials are mixed with each other and the mixing ratio is different. If the width exceeds 20 mm, the compatibility is inferior.

In addition, it is preferable that the sheet formed in step ii) has a thickness of 0.05 to 1.5 mm, and whether or not the final object can be formed into a thin plate-shaped separation plate is determined by the thickness of the sheet formed in step ii). Because it is determined according to the thickness can be adjusted well to reduce the thickness variation, it is possible to obtain a mesh-shaped separator plate. If the thickness of the sheet is less than 0.05 mm, there is a disadvantage that the mechanical strength is lowered, and if the thickness exceeds 1.5 mm, it is impossible to manufacture a mesh-type separation plate into a thin plate.

In addition, although the sheet of step ii) has a multilayer structure, it is advantageous in terms of improving the performance and precision of the separator, but a sheet having a multilayer structure of more than three layers becomes so thick that the separator, which is the final object, is thinned. Since it becomes difficult to manufacture, it is preferable to have a laminated structure of 2-3 layers.

And the mold of step iii) can be used to produce a separation plate of better performance by using a wavy channel having a concave portion and a convex portion formed by the stamping process.

Finally, in order to avoid the disadvantage of partial thickness variation due to the density difference, the pressure of 1,000 to 2,000 kgf / cm ^{2 and} the pressure of 150 to 170 are used in the compression molding of step iii). By performing compression and warming for 1 to 5 minutes at a temperature of ℃ it is possible to manufacture a mesh separator of the thin plate for fuel cells.

Hereinafter, specific embodiments will be described in detail.

Example 1 Manufacture of Mesh Type Separator for Fuel Cell

A raw material consisting of 15 parts by weight of phenol resin and 85 parts by weight of graphite having an average particle diameter of 20 μm was kneaded, and B raw material consisting of 40 parts by weight of phenol resin and 60 parts by weight of graphite having an average particle diameter of 20 μm was kneaded, and then kneaded A, B The raw material was fed into a mold in the form of a mesh of 10 mm in width using an automatic powder feeding device, and the sheet was formed by simply pressing without heating. The molded sheet was introduced into a mold having a flow path and compression molded at 170 ° C. for 2 minutes and 30 seconds at a pressure of 1,000 kgf / cm ² to prepare a mesh separator plate for a fuel cell having a thickness of 1.2 mm.

Example 2 Fabrication of Mesh Type Separator for Fuel Cell

A thin-walled fuel cell mesh separator of 1.2 mm in thickness was manufactured in the same manner as in Example 1, except that 25 parts by weight of a phenol resin and 75 parts by weight of graphite having an average particle diameter of 20 m were used as B materials.

Comparative Example 1 Production of Separator Plate for Fuel Cell

A separator for a conventional fuel cell was manufactured in the same manner as in Example 1, except that only A was added to a mold.

Comparative Example 2 Production of Separator Plate for Fuel Cell

A separator for a conventional fuel cell was manufactured in the same manner as in Example 1, except that only B was added to a mold.

Figure 3 shows a real picture of the fuel cell mesh separator prepared from Example 1 of the present invention, the following Table 1 is a fuel cell mesh separator prepared according to Examples 1, 2 of the present invention and Electrical conductivity and flexural strength of conventional fuel cell separators prepared according to Comparative Examples 1 and 2 are shown.

Table 1

Properties	Example 1	Example 2	Comparative Example 1	Comparative Example 2
Electrical Conductivity (S / cm)	13.76-85.06	36 ~ 83	75-83	16-19
Flexural Strength (Mpa)	40	35	20	50

As shown in Table 1, the conventional fuel cell separators prepared according to Comparative Examples 1 and 2 use only one raw material A or one raw material B as raw materials. Therefore, electrical conductivity and flexural strength are typical according to the mixing ratio of phenol resin and graphite. While it can be seen that there is a trade-off relationship, the mesh type separator for fuel cells of thin plates manufactured according to Examples 1 and 2 of the present invention has the electrical conductivity and flexural strength without having a typical trade-off relationship. It can be confirmed that the eggplant properties are all excellent.

In addition, Figure 4 is a graph showing the electrical conductivity average value, maximum value, minimum value of the fuel cell mesh separator of the thin plate prepared from Example 2 of the present invention and the conventional fuel cell separator prepared from Comparative Examples 1, 2 [ (a) Comparative Example 1 average value, (b) Example 2 maximum value, (c) Example 2 average value, (d) Example 2 minimum value, (e) Comparative example 2 average value]. In the case of the average value of the conductivity of 75 S / cm, Comparative Example 2, the average value of the electrical conductivity was measured as 40 S / cm, while in the case of Example 2 the average value of the electrical conductivity is slightly lower, 57 S / cm, The maximum value was 83 S / cm and the minimum value was 36 S / cm, and it was confirmed that all of the electrical conductivity properties of the separator manufactured using only the raw material A or B were obtained.

And Figure 5 shows the results of the random measurement of the electrical conductivity of 17 parts of the surface of the separator plate in order to more reliably confirm the electrical conductivity characteristics of the mesh type separator for fuel cell thin plate prepared from Example 2 of the present invention As a graph, it can be seen that the thin plate fuel cell separator prepared from Example 2 of the present invention has a mesh-like structure, and thus, two kinds of A and B raw materials having different blending ratios exhibit blended electrical conductivity characteristics.

Therefore, the mesh separator of the thin plate manufactured according to the present invention has excellent electrical conductivity and flexural strength, and can be applied as a separator of a fuel cell.

Claims (11)

1. A mesh type separator for fuel cell comprising a thermoplastic resin or a thermosetting resin and two blends having different mixing ratios of conductive carbon materials.
2. The method of claim 1, wherein the thermoplastic resin is polyethylene, polypropylene, polymethyl methacrylate, polybutylene terephthalate, polyamide, polyimide, polycarbonate, polyvinylidene fluoride, polyether sulfone, polyether ether ketone A mesh type separator for fuel cell, characterized in that any one selected from the group consisting of polyphenylene sulfide, and polybenzimidazole.
3. The method of claim 1, wherein the thermosetting resin is any one selected from the group consisting of phenol resin, epoxy resin, urea resin, melamine resin, unsaturated polyester resin, polycarbodiimide resin, perryl alcohol resin, and alkyd resin A mesh type separator for fuel cell.
4. The fuel according to claim 1, wherein the conductive carbon material is any one selected from the group consisting of natural graphite, artificial graphite, expanded graphite, carbon black, carbon fiber, carbon nanotubes, amorphous carbon, and mixtures thereof. Mesh separator for battery.
5. The fuel cell mesh separation plate according to claim 1, wherein a blending ratio of the thermoplastic resin or the thermosetting resin and the conductive carbon material is 10:90 to 60:40.
6. i) kneading the two kinds of raw materials having different mixing ratios of the thermoplastic resin or the thermosetting resin and the conductive carbon material;

   ii) injecting two kinds of raw materials having different mixing ratios in step i) into a mold in a mesh form and pressing to form a sheet; And

   iii) inserting the sheet formed in the step ii) into a mold in which a flow path is formed and compressing the molded sheet.
7. The method of claim 6, wherein the step of adding the mold to the mold in the step ii) is performed in a width of 5 to 20 mm in a mesh form using an automatic powder input device. .
8. The method of claim 6, wherein the sheet formed in step ii) has a thickness of 0.05 to 1.5 mm.
9. The method of claim 6, wherein the sheet formed in step ii) has a laminated structure of two to three layers.
10. 7. The method of claim 6, wherein the mold of step iii) has a wavy flow path having a concave portion and a convex portion formed by a stamping process.
11. The method of claim 6, wherein the compression molding of step iii) is prepared for the fuel cell mesh separator for 1-5 minutes at a pressure of 1,000 ~ 2,000 kgf / cm ² , a temperature of 150 ~ 170 ℃. Way.

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