KR20060097955A - Bipolar plate for fuel cell - Google Patents

Abstract

The present invention relates to a separator for a fuel cell, wherein the main body 101 of the separator 100 includes an active region 110 in which an electrochemical reaction occurs, and a gasket contacting the gasket of the fuel cell outside the active region 110. A non-active region 130 in which an electrochemical reaction does not occur between the contact region 120 and the gasket contact region 120 and the active region 110 is partitioned, and an anticorrosive substance is selectively applied to the surface of each region. Characterized in that. Therefore, even if an expensive corrosion protection material is applied to only a part of the area, it is possible to suppress the occurrence of corrosion, thereby reducing the manufacturing cost due to the reduction of the surface treatment area for corrosion, and excellent corrosion protection effect.

Description

Separation Plate for Fuel Cell {BIPOLAR PLATE FOR FUEL CELL}

1 is a perspective view illustrating components of a unit cell for a fuel cell according to an exemplary embodiment of the present invention;

FIG. 2 is a front view illustrating the graphite separator in FIG. 1;

FIG. 3A illustrates the separator of the metal material in FIG. 1;

3B is an enlarged fragmentary view showing the flow path of FIG. 3 in an enlarged manner;

4 is a front view of a separator for a fuel cell according to the present invention;

5 is a cross-sectional view taken along the line A-A of FIG. 4 according to an embodiment,

6 is a corrosion rate test diagram of the metal separator prepared by the method according to the present invention,

7 is a performance test diagram of the metal separator produced by the method according to the invention,

8 is a photograph showing the surface of the metal separator prepared by the method according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: separator 101: body

110: active area 120: gasket contact area

130: non-active area 140: teflon

150: gold

The present invention relates to a separator used in a fuel cell that generates electricity by converting chemical energy into electrical energy, and more particularly, to improve the surface treatment of corrosion caused in the separator plate of metal due to water and fuel gas. As a result, the present invention relates to a separator for fuel cells, in which corrosion is prevented and manufacturing costs are reduced.

In general, combustion obtains thermal energy as heat of reaction under rapid oxidation, whereas a fuel cell obtains electrical energy directly from fuel by electrochemical ion reaction.

It is a high-efficiency footwear technology that produces electricity and heat at the same time by electrochemically reacting hydrogen contained in natural gas (methane), naphtha, methanol, coal gas and oxygen in the air.

Internal combustion engine power generation is always efficient, but fuel cell power generation can be generated as needed and efficiency does not change significantly. It can be manufactured from the smallest to the smallest, so it can be sized according to demand and installed right where it is needed, thus reducing the transport loss of electricity generated by sending electricity through wires in existing power generation. In addition, the fuel cell has higher conversion efficiency than the current thermal power plant and is expected to be about 50% or more even when considering the loss of converting the chemical energy of the fuel from direct current to alternating current in order to convert the chemical energy of the fuel directly into electrical energy without going through thermal energy. Can be. Fuel cells are classified into phosphoric acid (PAFC), molten carbonate (MCFC), solid oxide (SOFC), and polymer electrolyte (PEMFC) fuel cells according to the type of electrolyte.

The operating temperature of the fuel cell is about 1000 ° C for solid oxide fuel cells, about 650 ° C for molten carbonate fuel cells, about 200 ° C for phosphoric acid fuel cells and about for polymer electrolyte fuel cells. It is 80 degrees C or less.

The polymer electrolyte fuel cell (Polymer Electrolyte Membrane Fuel Cell or Proton Exchange Membrane Fuel Cell, hereinafter referred to as PEMFC) is also called PEM (Polymer Electrolyte Membrane) method because it uses a polymer electrolyte. The PEMFC can operate at the lowest temperature among the four types of fuel cells described above, with an operating temperature of about 80 ° C, high energy density and efficiency, and agile change of output depending on the power demand. It is easy to stop and does not cause environmental pollution.

In general, PEMFC is composed of a membrane electrode assembly and a separator plate of conductive material overlapping both sides of the membrane electrode assembly, and is used in the form of stacking unit cells. Particularly, in a fuel cell having a structure in which unit cells are continuously connected and stacked, a portion that serves to electrically connect the cells and the cells and blocks fuel gases from being mixed with each other inside the cell is called a separator plate. It is called.

In order to move the fuel gas, the separator has a flow channel through which gas can move on the anode side where the oxidation reaction occurs and the cathode side where the reduction reaction occurs. Since it has a flow path on both sides, it is called a bipolar plate. The one-sided flow path is called a monopolar plate and constitutes a unit cell. A plurality of separator plates are stacked to form a stack.

  The separator is used as a support for the membrane electrode junction in addition to the movement of the fuel gas. In order to perform the role of the support, it must have mechanical strength to withstand the fastening pressure required for the stack, and it must be made of a material having excellent chemical resistance because it serves as a conductor for transferring electricity.

Therefore, FIG. 1 is a perspective view illustrating components of a unit cell for a fuel cell according to a conventional embodiment, FIG. 2 is a front view illustrating a graphite separator in FIG. 1, and FIG. 3A shows a separator of a metal material in FIG. 1. It is shown.

In general, a fuel cell is composed of a stack and a unit cell 1 constituting the stack. A portion where hydrogen gas flows is called a cathode side, and a portion where air or oxygen flows is called an anode side.

As shown in FIG. 1, the negative electrode component includes an end plate 2 for fastening a unit cell, an electrical current collector 3 for discharging electricity, and a separator plate 4 for flowing a fuel gas. ), And a gasket (5) for preventing gas leakage, and a gas diffusion layer (6) for moving the fuel gas to an electrode with a catalyst, and a platinum catalyst for separating hydrogen gas into hydrogen ions and a hydrogen ion separated from the gas. It is divided into a membrane electrode assembly 7 formed of an ion conductive electrolyte membrane that moves to the anode side. The anode side component is composed of a gas diffusion layer 6a, a gasket 5a, a separator plate 4a, an electrical current collector 3a, and an end plate 2a for moving air or oxygen gas to an electrode.

In the separator 4 shown in FIG. 2, a guide hole 8 is formed for ease of fabrication of the unit cell 1, and the fuel gas flows through the gas inlet 9 and passes through the flow path 10. It is discharged through the outlet 11.

In addition, the separator 4 having such a structure uses expensive graphite having excellent chemical stability and electrical conductivity, and is generally manufactured by CNC machining.

However, the separator 4 using graphite material has disadvantages of high unit cost and low mechanical strength. Therefore, in recent years, in order to replace graphite materials, metal separator plates based on metal materials such as SUS and Fe-based materials have been developed. In particular, the metal separator has many advantages over the graphite separator, but corrosion occurs due to an electrochemical reaction, and thus a technical approach is difficult.

The separating plate 40 of the metal material in FIG. 3A has a form in which the gas diffusion layer 44 is placed on the main body in which the flow path 42 is formed.

However, in the separation plate 40 of the metallic material, water and fuel gas are present in the flow path, and oxidation and reduction reactions are actively performed at the electrode part. Under such conditions, most metal materials are corroded to melt the metal ions. The molten metal ion becomes a factor that gradually decreases the ion conductivity by poisoning the active point of the electrolyte membrane. Therefore, the surface is treated with a corrosion resistant material to prevent the elution of these metal ions. Currently, gold is used as a corrosion resistant material, and in this case, it is known that it can be operated for a long time. In particular, the surface where the flow path is formed in the separation plate and the part where the separation plate and the gas diffusion layer contact each other should be treated with a corrosion resistant material during surface treatment using gold material. In other words, the surface of all the parts except the part in contact with the gasket in the separator plate has a disadvantage in that a large amount of gold material is consumed, which does not significantly reduce the unit cost compared to expensive graphite. And there was a weakness that the corrosion phenomenon occurs in the area where the valley (42a) and the valley 42b of the flow path 42 shown in Figure 3b and the corner of the valley.

The present invention has been made to solve the above-mentioned drawbacks, and the surface area of the metal separator is partitioned into an area where the electrochemical reaction occurs, an area where the electrochemical reaction does not occur, and a contact area with the gasket, each area By selectively surface-treating a material that can prevent corrosion by water and electrical properties, the manufacturing cost is reduced by reducing the surface treatment area for corrosion, and to provide a fuel cell separator having excellent corrosion protection effect. will be.

In order to achieve the above object, the present invention provides a fuel cell separator comprising: an active region in which a main body of the separator plate is subjected to an electrochemical reaction, a gasket contact region in contact with a gasket of the fuel cell outside the active region; A partition plate for a fuel cell is formed between a gasket contact region and an active region, and partitioned into non-active regions where no electrochemical reaction occurs, and selectively applying a corrosion preventing material to the surface of each region.

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a front view of a separator for a fuel cell according to the present invention, FIG. 5 is a cross-sectional view taken along line AA of FIG. 4 according to an embodiment, and FIG. 6 is a corrosion rate test diagram of a metal separator manufactured by the method according to the present invention. 7 is a performance test diagram of a metal separator prepared by the method according to the present invention, and FIG. 8 is a photograph showing the surface of the metal separator manufactured by the method according to the present invention.

As shown in FIG. 4, the fuel cell separator 100 includes an active area 110 in which a main body 101 contacts an gas diffusion layer and undergoes oxidation and reduction, and a gasket (shown in FIG. 1: 5). ) And a non-active area between the active area 110 and the gasket contact area 120, although the gasket contact area 120 in contact with the main body 101 does not occur in oxidation or reduction reaction. Non Active Area: 130).

As shown in FIG. 5, the separating plate 100 is oxidized and reduced to the actuate region 110 and the gasket contact region 120 with the main body 101 made of aluminum, which is a lightweight metal, as a preferred embodiment. Surface treatment was made using Teflon {PTFE (polytetrafluoroethylen): 140}, a corrosion resistant material that is resistant to the reaction, and gold (Au: 150) having strong electrical properties for oxidation and reduction reactions was treated on the non-active region 130. It was. Here, the surface treatment may be performed on conductive and non-conductive materials such as polymers and ceramics.

In the method of applying a corrosive substance to each divided region 110, 120, 130, the surface of the active region 110, the gasket contact region 120, and the non-active region 130 is formed of Teflon 140. Alternatively, the main body 101 of the separator 100 may be made of a conductive material such as gold 150, and may be surface-treated with the Teflon 140 only on the non-active region 130.

In another embodiment, the active material 110, the gasket contact area 120, and the non-active area 130 of the main body 101 made of a metal material are entirely surface treated with a conductive material such as gold 150. The non-active region 130 except for the active region 110 and the gasket contact region 120 may be surface-treated with the Teflon 140.

In addition, the body 101 is made of a material of Teflon 140, and the non-active area 130 is surface-treated with a conductive material such as gold 150.

Referring to the preferred embodiment of the operation of the fuel cell separator according to the present invention configured as described as follows.

The separator plate 100, which should not cause corrosion while maintaining electrical conductivity, has a gasket contact region 120 in which the gasket 5 and the separator plate 100 are in contact with the main body 101 of aluminum material having a thickness of about 2 mm. Surface treated with Teflon 140, and the non-active region 130, which is the portion of electricity generated by the fuel cell, was treated with gold (Au: 150), and the active region 110, the electrochemical reaction, occurred. Bone and acid) was surface-treated with Teflon 140.

In the separation plate 100 of the metal material configured as described above, the surface of the non-active area 130 is surface-treated with the gold 150 material in the form in which the surface of the separation plate is conventionally used by the gold 150. Compared to the surface treatment method, the amount of gold 150 used may be significantly reduced. In the case of the horizontal 7 cm and the vertical 7 cm separation plates 100 having a reaction area of 25 cm 2, the total surface area is 74.4 cm 2, and the surface area of the gasket contact area 120 is 19.84 cm 2 and the surface area of the non-active area 130 is 4.16 cm 2. The surface area of the active region 110 is 50.4 cm 2. That is, the separator 100 of the gold material 150 according to the present invention could reduce the amount of gold used by about 95% from 74.4 cm 2 to 4.16 cm 2 of gold surface treatment area.

  6 is a result of the corrosion test of the non-active area 130 and the surface-treated aluminum of the separator 100 according to the present invention. Corrosion conditions were tested at 70 ° C with 2 ppm HF added to 2 M H2SO4. As shown, the non-active area 130 of the separator 100 is 1.38 μA / superior to the separator corrosion rate of 16 μA / cm 2 or less (2010 target value) published by the Department of Energy (DOE). Cm 2 was obtained.

In addition, Figure 7 is the result of the performance analysis using the separator 100 according to the present invention. A power density of 0.421 W / cm 2 was obtained under a unit cell operating temperature of 70 ° C. and 0.6V.

8 shows the surface of the active region 110 and the non-active region 130 after the performance analysis of the separator 100 with an optical microscope, and no corrosion phenomenon appeared on the surface after the performance test.

Meanwhile, in the gasket contact region 120 and the active region 110, the surface treatment may be performed using a non-conductive polymer, a conductive polymer, a conductive ceramic, a non-conductive ceramic, etc., as well as a Teflon 140. Accordingly, the manufacturing cost can be reduced and the characteristics of the separator 100 can be adjusted.

 And the basic concept of the separator plate 100 of the present invention can be applied to all of the base metal, such as Cu, Ni, Ti, SUS, etc. The conductive plate can be selectively manufactured according to the scope and environment.

In addition, since the manufacturing cost of the metal separator plate 100 is about $ 30 / kW, it is possible to replace graphite of about $ 3000 / kW, and the manufacturing cost may be further reduced when using a Fe-based low-cost unit.

Furthermore, the separator 100 of the present invention can be applied to fuel cells for mobile, home and power generation as well as automobile fuel cells, and when using a polymer material which is a non-conductive material as a base material, a portable fuel cell can be minimized by minimizing unit cost and volume. Can also be used.

As described above, the present invention is designed as a separator plate 100 of a lightweight corrosion-resistant metal material in order to replace an expensive graphite substrate separator plate used in a conventional fuel cell, and in particular, corrosion generated in a metal separator plate. In order to prevent the phenomenon, the area where the separation plate and the gas diffusion layer contact each other is designed as the active region 110 and the non-active area 130, and the area where the separation plate and the gasket abuts as the gasket contact region 120 is designed to generate an existing corrosion. By reducing the possible area to 1/17 or less to reduce the manufacturing cost and to produce a separator excellent in corrosion resistance.

In the above description, it should be understood that those skilled in the art can make modifications and changes to the present invention without changing the gist of the present invention as merely illustrative of a preferred embodiment of the present invention.

As described above, in the fuel cell separator according to the present invention, the surface area is partitioned into an area where an electrochemical reaction occurs, an area where an electrochemical reaction does not occur, and a gasket and a contact area, and electrical characteristics of each region are shown. By selectively surface-treating the material that can prevent corrosion by water and water, the manufacturing cost is reduced by reducing the surface treatment area for corrosion, and the corrosion protection effect is very excellent.

Claims (7)

In the separator for fuel cell, The main body of the separating plate, An active region in which an electrochemical reaction occurs, A gasket contact region which contacts the gasket of the fuel cell outside of the active region; A partition is formed between the gasket contact region and the active region into a non-active region in which no electrochemical reaction occurs, Separation plate for a fuel cell to selectively apply a corrosion protection material to the surface of each area. The method of claim 1, The separator plate, Surface treatment of the active region with a conductive material such as gold, Surface treatment of the gasket contact region with a conductive material such as gold, Separation plate for a fuel cell surface-treated with a conductive material such as gold in the non-active area. The method of claim 1, The separator plate, Surface treatment of the active region with a conductive material such as gold, Surface treatment of the gasket contact region with a conductive material such as gold, Separation plate for a fuel cell surface-treated in the non-active region with a Teflon corrosion resistant material resistant to oxidation and reduction. The method of claim 1, The main body of the separator plate made of Teflon material, the non-active area for the fuel cell separator plate surface treatment with a conductive material such as gold. The method of claim 1, The separator plate, Surface treatment with Teflon on the active region, Surface treatment with Teflon on the gasket contact area, Separation plate for a fuel cell surface-treated with Teflon in the non-active area. The method of claim 1, The separator plate, Surface treatment with Teflon on the active region, Surface treatment with Teflon on the gasket contact area, Separation plate for a fuel cell surface-treated with a conductive material such as gold in the non-active area. The method of claim 1, A separator for a fuel cell, which is made of a conductive material such as gold and the surface of the separator is made of Teflon on the non-active region.

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