KR101364072B1 - Separating plate for fuel cell and the method of manufacturing the same - Google Patents

Abstract

The present invention relates to a separator for a fuel cell which has a sandwich structure formed of a carbon thin film layer, a composite material layer, and another carbon thin film layer. A method of manufacturing the separator comprises the following steps: a first step for forming the composite material layer formed of carbon single fibers and a polymer resin; a second step for removing the polymer resin by processing both sides of the composite material layer with plasma; a third step for forming carbon thin film layers on both sides of the composite material layer without the polymer resin; and a fourth step for forming the sandwich structure formed of the carbon thin film layer, the composite material layer, and another carbon thin film layer using a vacuum bag molding method using an autoclave or a compressing and molding method using a hot-press. [Reference numerals] (AA,DD,GG) Resin; (BB,EE,HH) Carbon fibers; (CC,FF) Plasma process; (II) Carbon film

Description

Separating plate for fuel cell and the method of manufacturing the same

The present invention relates to a separator for a fuel cell and a method of manufacturing the same.

Fuel cells are electrochemical power generation systems that convert the chemical energy of hydrogen and oxygen directly into electrical and thermal energy. Fuel cells are spotlighted as eco-friendly energy sources with high power generation efficiency and no emission of harmful substances.

Fuel cells can be classified into alkali type (AFC), phosphate type (PAGC), molten carbonate type (MCFC), solid electrolyte type (SOFC), and polymer electrolyte type (PEMFC) according to operating temperature and type of main fuel. .

The electrolyte of the dual polymer electrolyte fuel cell is not a liquid but a solid polymer (Membrane) can be distinguished from other fuel cells. The polymer electrolyte membrane fuel cell is composed of a separator and membrane electrode assembly (MEA), which can be operated at a relatively low temperature of about 80 to 120 ° C and has a very high power density. It is used as a power source of such.

The separator has a channel through which fuel and air flow, and serves as an electron conductor for electron movement between membrane electrode assemblies. The separator should have low gas permeability and good electrical conductivity so that fuel and oxygen can be separated. In addition, it must have sufficient thermal conductivity for temperature control of the fuel cell, not only have sufficient mechanical strength to withstand the mechanical force to fasten the fuel cell, but also have corrosion resistance to hydrogen ions. .

As a separator of a conventional polymer electrolyte membrane fuel cell, a graphite plate is mainly used. The graphite separator has an advantage of excellent electrical conductivity and poor corrosion, but the fuel and air flow paths of the graphite separator are mainly formed by machining, and thus have a high processing cost and have brittleness. In addition, the graphite separator is not easy to be processed into a thin thickness because it is easy to break. Therefore, there is a limit in reducing the stack thickness of a fuel cell composed of tens to hundreds of unit cells.

Accordingly, research is being conducted to improve the material of the bipolar plate, which uses a metal or graphite to reduce the weight and size of the polymer electrolyte membrane fuel cell and stabilize performance.

For example, Korean Patent Publication No. 2009-0013420 has a sandwich structure of a composite material layer 12, a metal thin film layer 14, and a composite material layer 12, as shown in FIG. Disclosed is a separator for a fuel cell, wherein the reinforcing material and the polymer matrix are formed of a fiber reinforced composite material.

However, since the above technique uses a metal thin film layer, the metal is easily corroded in an acidic environment inside the fuel cell, and an oxide film having a large electrical resistance is easily formed. Corrosion of the separator not only causes defects of the separator itself, but also causes ion adsorption of the catalyst and electrolyte by diffusion of metal ions into the electrolyte membrane. This also lowers the performance of the fuel cell. In addition, the bond strength due to the heterogeneous bonding between the metal thin film and the composite material is lowered, the strength may be lowered, and the efficiency of the fuel cell may be reduced. In addition, there is room for improvement in terms of electrical conductivity, and in the manufacture of a separator for a fuel cell, there is an inconvenience of using a high specification press and mold in the manufacturing process.

KR 2009-0013420 A KR 2012-0032749 A

In order to solve the problems of the prior art, the present invention is excellent in corrosion resistance, by providing a separation plate for a fuel cell that can improve the performance of the fuel cell by excellent electrical conductivity by reducing the contact resistance between unit cells. There is a purpose.

Another object of the present invention is to provide a method of manufacturing a separator for a fuel cell capable of performing a continuous process through plasma.

In order to achieve the above object, the present invention provides a separator for a fuel cell consisting of a sandwich structure of a carbon thin film layer-composite layer-carbon thin film layer.

In addition, the present invention, the first step of molding a composite material layer consisting of short carbon fibers and a polymer resin;

Performing a plasma treatment on both surfaces of the composite material layer to remove the polymer resin;

Forming a carbon thin film layer on both surfaces of the composite material layer from which the polymer resin is removed; And

Provided is a method of manufacturing a separator for a fuel cell, comprising a fourth step of forming a sandwich structure of a carbon thin film layer-composite layer-carbon thin film layer by a vacuum bag molding method using an autoclave or a compression molding method using a hot press.

In the fuel cell separator of the present invention, the resin layer is removed through plasma treatment and the carbon thin film layer is formed by carbon deposition, thereby providing excellent corrosion resistance and reducing contact resistance between unit cells.

The manufacturing method of the fuel cell separator of the present invention has the advantage that the continuous process through the plasma treatment is possible, the surface may not be constant after forming the flow path.

1 shows a conventional separator for fuel cells.
FIG. 2 schematically shows a manufacturing process of a separator for fuel cells of Example 1. FIG.
3 is a view illustrating the surface state of the separator of the first step of Example 1 with an optical microscope.
4 is a view illustrating the surface state of the separator of the second step of Example 1 with an optical microscope.
FIG. 5 shows the surface state of the separator of the third step of Example 1 under an optical microscope.
6 is an observation of the surface state of the separator of Comparative Example 1 with an optical microscope.

Hereinafter, the present invention will be described in detail.

The present invention provides a separator for a fuel cell having a sandwich structure of a carbon thin film layer-composite layer-carbon thin film layer.

The composite material layer may be formed of a carbon fiber reinforced composite material, and may be formed by stacking prepregs impregnated with short carbon fibers and a polymer resin, or may be molded by mixing short carbon fibers and a polymer resin.

The short carbon fiber is preferably a short fiber of polyacrylonitrile-based carbon fiber, but is not necessarily limited thereto. The short carbon fiber has a diameter of 5 to 15 µm, and preferably has a volume resistivity in the longitudinal direction of 200 µΩ · m or less.

The polymer resin is one or a mixture of two or more selected from the group consisting of epoxy resins, polyester resins and phenol resins.

Based on the total weight of the composite material layer, the content of the short carbon fibers is preferably 50 to 70% by weight, and the content of the polymer resin is preferably 30 to 50% by weight. The thickness of the composite material layer is preferably 20 ~ 30 μm.

The separator for fuel cells of the present invention has a sandwich structure in which a carbon thin film layer is formed on both surfaces of the composite material layer.

To this end, both surfaces of the composite material layer are plasma treated to remove the polymer resin, and a carbon thin film layer is formed on both surfaces of the composite material layer.

The carbon thin film layer is deposited on both sides of the composite material layer by the principle of atmospheric plasma coating, it is possible to improve the electrical conductivity of the separator for fuel cell. The carbon thin film layer preferably has a thickness of 100 μm to 140 μm.

The separator for a fuel cell of the present invention has a sandwich structure of a carbon thin film layer, a composite material layer, and a carbon thin film layer. The polymer resin has a superior corrosion resistance compared to a metal thin film by using a polymer resin, and the carbon fiber has an excellent strength. . In addition, the excellent conductivity of the carbon fiber has the advantage of reducing the contact resistance between the unit cells.

In addition, the present invention, the first step of molding a composite material layer consisting of short carbon fibers and a polymer resin;

Performing a plasma treatment on both surfaces of the composite material layer to remove the polymer resin;

Forming a carbon thin film layer on both surfaces of the composite material layer from which the polymer resin is removed; And

Provided is a method of manufacturing a separator for a fuel cell, comprising a fourth step of forming a sandwich structure of a carbon thin film layer-composite layer-carbon thin film layer by a vacuum bag molding method using an autoclave or a compression molding method using a hot press.

The first step is a step of forming a composite material layer made of a carbon fiber reinforced composite material, by forming a composite material layer by laminating a prepreg impregnated with a short carbon fiber and a polymer resin, or by forming a short carbon fiber and a polymer resin Step of forming a composite material layer by mixing.

In the second step, the electrical conductivity of the composite material layer is improved by plasma treatment of both surfaces of the composite material layer.

At this time, the plasma treatment conditions are performed by irradiating forward and backward for 5 to 40 minutes at a power of 150W to 300W using an atmospheric pressure plasma irradiation equipment.

In the third step, to form a carbon thin film layer on both sides of the composite material layer from which the polymer resin is removed, an atmospheric pressure plasma carbon deposition apparatus may be used. Atmospheric plasma carbon deposition apparatus is a device for surface deposition of carbon by the principle of atmospheric plasma coating. As described above, since the carbon thin film layers are formed on both surfaces of the composite material layer, electrical conductivity of the composite material layer may be further improved.

The fourth step is a step of forming a sandwich structure of the composite material-carbon thin film layer by vacuum bag molding using an autoclave or compression molding using a hot press. Vacuum bag molding using an autoclave and compression molding using a hot press were carried out according to a known method.

The method of manufacturing a separator for a fuel cell of the present invention is capable of a continuous process through plasma treatment, and the surface of the fuel cell can be treated uniformly even after forming a complicated flow path to prevent performance degradation of the fuel cell and can be applied to a separator of various materials. There is this.

Hereinafter, exemplary embodiments of a fuel cell separator and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

Example 1 Manufacture of Separator for Fuel Cell

2 illustrates a method of manufacturing a separator for a fuel cell according to an embodiment of the present invention. Referring to FIG. 2, the resin-impregnated carbon fiber prepreg was stacked and a separator having a constant thickness was formed by using a hot press (first step). Subsequently, the surface treatment was performed for 5 to 40 minutes using a plasma apparatus to remove the polymer resin present on both sides of the composite material layer to improve electrical conductivity (second step). Subsequently, a carbon thin film layer was formed on both surfaces of the composite material layer from which the polymer resin was removed using an atmospheric pressure plasma carbon deposition device to improve electrical conductivity (third step). Subsequently, a separator for a fuel cell having a sandwich structure of a carbon thin film layer, a composite material layer, and a carbon thin film layer was obtained by a compression molding method using a press (fourth step).

≪ Comparative Example 1 &

A separator for a fuel cell was manufactured in the same manner as in Example 1 except that the plasma treatment of the second step of Example 1 was not performed.

<Characteristic evaluation>

Surface resistance and contact resistance of the first, second and third steps of Example 1, and the separator of Comparative Example 1 were measured and shown in Table 1 below. Was observed and the results are shown in FIGS.

division Example 1 First Step Example 1
2nd step Example 1
Step 3 Comparative Example 1 Surface resistance (Ωcm) 2.93E-02 8.56E-03 2.31E-03
5.18E-03
Contact resistance (㏁ / ㎝ ² ) 766.21 300.74 256.27 653.53

As shown in Table 1, it can be seen that the separator of Comparative Example 1, which was not subjected to plasma treatment, had much higher surface resistance and contact resistance than the separator prepared in Example 1.

Therefore, it can be seen that the separator for the fuel cell of the present invention has improved electrical conductivity by removing the resin layer through plasma treatment and forming a carbon thin film layer through carbon deposition.

In addition, referring to FIGS. 3 to 6, it can be seen that the polymer of FIG. 4 is removed from the surface of the separation plate of FIG. As a result, the nonconducting polymer is removed, leading to carbon fibers having high conductivity, which can be expected to increase conductivity. In addition, it can be seen from FIG. 5 and FIG. 6 that the carbon layer represented by black dots is deposited on the surface through carbon deposition, and the conductivity increases due to the carbon layer.

Claims (11)

A separator for a fuel cell, comprising a sandwich structure of a carbon thin film layer, a composite material layer, and a carbon thin film layer. The separator of claim 1, wherein the composite material layer is formed by stacking prepreg impregnated with short carbon fibers and a polymer resin, or is formed by mixing short carbon fibers and a polymer resin. . The separator of claim 2, wherein the short carbon fibers are short fibers of polyacrylonitrile-based carbon fibers. The separator of claim 2, wherein the polymer resin is one or a mixture of two or more selected from the group consisting of an epoxy resin, a polyester resin, and a phenol resin. The separator of claim 2, wherein the short carbon fiber has a diameter of 5 to 15 µm and a volume resistivity in the longitudinal direction of 200 µΩ · m or less. The separator of claim 2, wherein the content of the short carbon fibers is 50 to 70% by weight, and the content of the polymer resin is 30 to 50% by weight based on the total weight of the composite material layer. The separator of claim 1, wherein the composite material layer has a thickness of 20 to 30 µm. The separator of claim 1, wherein the carbon thin film layer has a thickness of 100 μm to 140 μm. A first step of forming a composite material layer composed of short carbon fibers and a polymer resin;
Performing a plasma treatment on both surfaces of the composite material layer to remove the polymer resin;
Forming a carbon thin film layer on both surfaces of the composite material layer from which the polymer resin is removed; And
A method of manufacturing a separator for a fuel cell, comprising a fourth step of molding a carbon thin film layer-composite layer-carbon thin film layer sandwich structure by a vacuum bag molding method using an autoclave or a compression molding method using a hot press. The method of claim 9, wherein the first step is to form a composite material layer by stacking prepregs impregnated with short carbon fibers and a polymer resin, or to form a composite material layer by mixing short carbon fibers and a polymer resin. A method of manufacturing a separator for a fuel cell, characterized in that. The method of claim 9, wherein the third step is a step of forming a carbon thin film layer on both sides of the composite material layer from which the polymer resin is removed by using an atmospheric pressure plasma carbon deposition device.

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