KR20060000460A - Fuel cell system and stack used thereto - Google Patents

Abstract

Fuel cell system according to the present invention, at least one electricity generating unit for generating electrical energy through the electrochemical reaction of hydrogen and oxygen; A fuel supply unit supplying a fuel containing hydrogen to the electricity generation unit; And an oxygen supply unit for supplying oxygen to the electricity generator, wherein the electricity generator comprises an electrode-electrolyte composite (MEA) and separators disposed on both sides of the electrode-electrolyte composite, and the electrode-electrolyte composite; And a gasket interposed at an edge portion between both separators, the gasket being formed to overlap the electrode edge portion of the electrode-electrolyte composite.

Fuel cell, electricity generator, fuel supply, oxygen supply, separator, MEA, electrode, electrolyte membrane, gasket, crack

Description

FUEL CELL SYSTEM AND STACK USED THERETO}

1 is a schematic diagram showing a configuration of a fuel cell system according to an embodiment of the present invention.

2 is an exploded perspective view showing the structure of the stack shown in FIG.

3 is a cross-sectional view of the coupling cross-sectional view of FIG.

4 is an exploded perspective view illustrating a coupling structure of an electrode-electrolyte composite and a gasket according to an embodiment of the present invention.

5 is a cross-sectional view of the coupling cross-sectional view of FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system, and more particularly, to a fuel cell system having improved coupling structure of an electrode-electrolyte composite (MEA) and a gasket of a fuel cell.

As is known, a fuel cell is a power generation system that converts the chemical reaction energy of hydrogen contained in a hydrocarbon-based material such as methanol and oxygen or air containing oxygen directly into electrical energy.

The fuel cell uses hydrogen produced by reforming methanol or ethanol as a fuel, and has a wide range of applications such as mobile power sources such as automobiles, distributed power sources such as houses and public buildings, and small power sources such as electronic devices. Have

The fuel cell is a cell of a unit generating electricity, that is, a cell having a laminated structure by an electrode-electrolyte assembly (MEA) and a separator (also referred to as a bipolar plate) disposed on both sides thereof. The electrode-electrolyte composite is formed of an anode electrode and a cathode electrode positioned on both sides thereof with an electrolyte membrane interposed therebetween. In such an electrode-electrolyte composite, an anode electrode is positioned on one surface of the electrolyte membrane and a cathode electrode is positioned on the other surface of the electrolyte membrane so that a portion around the edge of the electrolyte membrane is exposed. The cell of the above unit is provided with a gasket connected to the edge portion of the electrode-electrolyte composite in order to maintain the airtight between the separators.

Such a gasket forms an opening in a central portion, and the edge of the opening is heat-sealed to the edge of both electrodes by a hot press while the edge of the opening covers both edges of the electrolyte membrane. Has a structure.

However, conventional fuel cells are particularly poly [2,5-benzimidazole] (ABPBI: poly [2,5-benzimidazole]) or poly [which operate at high temperatures of at least 1000 ° C. and whose electrolyte membrane has a tensile strength of approximately 100 Pa or less. 2,2 '-(m-phenylene) -5,5'-bibenzimidazole] (PBI: poly [2,2'-(m-phenylene) -5,5'-bibenzimidazole]) In a high temperature fuel cell, when the electrode-electrolyte composite and the gasket are combined by the hot press method as described above, the hot pressure of the press is concentrated in the gap between the opening edge end of the gasket and the edge end of both electrodes. A crack phenomenon such as the electrolyte membrane being broken due to the hot pressure cannot be overcome. Therefore, there is a problem in that the airtight between the separator and the electrode-electrolyte composite is broken due to the crack of the electrolyte membrane, thereby degrading the performance of the fuel cell.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a fuel cell system having an improved structure of bonding of an electrode-electrolyte composite and a gasket so as not to damage the electrolyte membrane of the electrode-electrolyte membrane (MEA). .

In order to achieve the above object, a fuel cell system according to the present invention includes at least one electricity generating unit for generating electrical energy through an electrochemical reaction between hydrogen and oxygen; A fuel supply unit supplying a fuel containing hydrogen to the electricity generation unit; And an oxygen supply unit for supplying oxygen to the electricity generator, wherein the electricity generator comprises an electrode-electrolyte composite (MEA) and separators disposed on both sides of the electrode-electrolyte composite, and the electrode-electrolyte composite; And a gasket interposed at an edge portion between both separators, the gasket being formed to overlap the electrode edge portion of the electrode-electrolyte composite.                     

In the fuel cell system according to the present invention, the electrode-electrolyte composite may be configured such that an anode electrode and a cathode electrode are positioned on both surfaces thereof with an electrolyte membrane interposed therebetween, and an edge portion of the electrolyte membrane is exposed outside the edge of the electrode. have.

In the fuel cell system according to the present invention, the gasket may form an opening in which the electrode-electrolyte composite is located, and the area of the opening may be smaller than the electrode area of the electrode-electrolyte composite.

In the fuel cell system according to the present invention, the gasket may be formed such that an edge portion of the opening covers 1 to 2 mm of an edge portion of the electrode.

In addition, in the fuel cell system according to the present invention, the electricity generating unit is made of a high temperature fuel cell operating at a high temperature of 1000 ℃ or more, the electrolyte membrane is poly [2,2 '-(m-phenylene) -5,5 It is preferable that it consists of "-bibenzimidazole" or poly [2,5-benzimidazole].

And a fuel cell system according to the present invention, wherein the fuel supply unit comprises: a fuel tank for storing fuel containing hydrogen; And a fuel pump connected to the fuel tank. The oxygen supply unit may include an air pump for sucking air.

In the fuel cell system according to the present invention, the fuel supply unit is connected to the electricity generating unit and the fuel tank to receive the fuel from the fuel tank to generate hydrogen gas, and supply the hydrogen gas to the electricity generating unit. It may also include a reformer. In this case, the fuel cell system according to the present invention, the fuel cell system is made of a polymer electrolyte fuel cell (PEMFC) method.

In addition, the stack used in the fuel cell system according to the present invention to achieve the above object, at least one electricity generation consisting of an electrode-electrolyte composite (MEA) and a separator disposed on both sides of the electrode-electrolyte composite And an electricity generating portion having a gasket interposed between the electrode-electrolyte composite and both separators, wherein the electrode-electrolyte composite has an anode electrode and a cathode electrode on both sides thereof with an electrolyte membrane therebetween. And the edge portion of the electrolyte membrane is exposed outside the edge of the electrode, wherein the gasket forms an opening in which the electrode-electrolyte composite is located, and the area of the opening is larger than the electrode area of the electrode-electrolyte composite. Form small.

In the stack used in the fuel cell system according to the present invention, the gasket may be formed such that the edge portion of the opening covers the edge portion of the electrode 1 to 2 mm.

In addition, the stack used in the fuel cell system according to the present invention has a structure in which the gasket and the electrode-electrolyte composite are combined by a hot press method.

In the stack used in the fuel cell system according to the present invention, the electricity generating unit is made of a high temperature fuel cell operating at a high temperature of 1000 ° C. or higher, and the electrolyte membrane is made of poly [2,2 ′-(m-phenylene). -5,5'-bibenzimidazole] or poly [2,5-benzimidazole].

In addition, the stack used in the fuel cell system according to the present invention for achieving the above object is a high-temperature fuel cell by the electrode-electrolyte composite (MEA) and the separator disposed on both sides of the electrode-electrolyte composite And at least one electricity generating portion, wherein the electricity generating portion is provided at an edge portion between the electrode-electrolyte composite and both separators, and has a gasket formed to overlap the electrode edge portion of the electrode-electrolyte composite. .

In the stack used in the fuel cell system according to the present invention, the gasket may be formed to cover the edge portion of the electrode 1 ~ 2mm.

In addition, in the stack used in the fuel cell system according to the present invention, the electrode-electrolyte composite has an anode electrode and a cathode electrode positioned on both surfaces thereof with an electrolyte membrane interposed therebetween, and an edge portion of the electrolyte membrane is exposed outside the edge of the electrode. And the electrolyte membrane is made of poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole] or poly [2,5-benzimidazole].

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.                     

1 is a schematic view showing the configuration of a fuel cell system according to an embodiment of the present invention, Figure 2 is an exploded perspective view showing the structure of the stack shown in Figure 1, Figure 3 is a combined cross-sectional view of Figure 2 .

Referring to the drawings, the system 100 is a polymer electrolyte fuel cell (PEMFC) that generates hydrogen gas by reforming a fuel containing hydrogen and reacting the hydrogen gas with oxygen to generate electrical energy. ) Can be adopted.

In the fuel cell system 100 according to the present invention, the fuel for generating electricity is a broad fuel other than a narrow fuel containing hydrogen such as methanol, ethanol or natural gas. And oxygen further.

In addition, the system 100 may use pure oxygen gas stored in a separate storage means as oxygen fuel reacting with hydrogen contained in the fuel, and may use air containing oxygen as it is. However, the latter example of using air as the oxygen fuel described above will be described below.

The fuel cell system 100 basically generates at least one electricity generating unit 111 that generates electrical energy through an electrochemical reaction between hydrogen and oxygen, and generates hydrogen gas from a fuel containing hydrogen. And a fuel supply unit 120 for supplying gas to the electricity generation unit 111, and an oxygen supply unit 130 for supplying air to the electricity generation unit 111.

The electricity generating unit 111 may employ conventional high temperature fuel cells and non-humidified fuel cells that operate at a high temperature of about 1000 ° C. or higher. The electricity generating unit 111 centers an electrode-electrolyte composite (MEA: hereinafter referred to as 'MEA') 112 and a separator (also referred to as a 'bipolar plate') on both sides thereof. ) To form a single stack, and a plurality of the electricity generating unit 111 is provided to form a stack 110 of the stacked structure as in the present embodiment.

As described above, the MEA 112 interposed between the two separators 116 has a predetermined area and has an active region in which an oxidation / reduction reaction occurs, and both of the anode electrode 112a and the cathode electrode 112b are located on both sides thereof. The electrolyte membrane 112c is provided between the two electrodes 112a and 112b. In this case, the anode electrode 112a is formed on one surface of the electrolyte membrane 112c, and the cathode electrode 112b is provided on the other surface of the electrolyte membrane 112c, so as to expose the edge portion of the electrolyte membrane 112c. Can be formed. Each of the electrodes 112a includes a catalyst layer for oxidizing / reducing hydrogen gas and oxygen diffused through a conventional gas diffusion layer (GDL).

A gasket 119 is provided at the edge portion between the MEA 112 and the separator 116 to maintain the airtight between the MEA 112 and the both separators 116. In this case, the gasket 119 may be formed to cover both edge portions of the electrolyte membrane 112c exposed by both electrodes 112a and 112b.

The separator 116 is closely arranged with the MEA 112 interposed therebetween, and forms the hydrogen passage 116a and the air passage 116b on both sides of the MEA 112, respectively. Here, the hydrogen passage 116a is located on the anode electrode 112a side of the MEA 112, and the air passage 116b is located on the cathode electrode 112b side of the MEA 112. The separator 116 has a function of a conductor that connects the anode electrode 112a and the cathode electrode 112b in series in addition to supplying hydrogen and oxygen to both sides of the MEA 112.

The electrolyte membrane 112c has a thickness of approximately 50 to 200 µm, for example, poly [2,5-benzimidazole] (ABPBI: poly [2,5-benzimidazole]) or poly [2,2'- (m-phenylene) -5,5'-bibenzimidazole] (PBI: poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole]) formed of a solid polymer electrolyte It enables ion exchange to move hydrogen ions generated at the anode electrode 112a to the cathode electrode 112b.

The fuel supply unit 120 is connected to the fuel tank 121 and the fuel tank 121 installed to the fuel tank 121, the fuel tank 121 is connected to the fuel tank 121, and is installed to A reformer 123 is generated to generate hydrogen gas from the fuel of consultation and to supply the hydrogen gas to the electricity generating unit 111. The oxygen supply unit 130 includes an air pump 124 that sucks air and supplies the air to the electricity generating unit 111.

In the fuel supply unit 120, the reformer 123 generates a hydrogen gas from the narrow fuel through a chemical catalytic reaction by thermal energy and reduces the concentration of carbon monoxide contained in the hydrogen gas. Has In detail, the reformer 123 generates hydrogen gas from the above-described fuel through a catalytic reaction such as steam reforming, partial oxidation, or autothermal reaction. As an example, the reformer 123 reduces the concentration of carbon monoxide contained in the hydrogen gas by a method such as a catalytic reaction such as a water gas conversion method, a selective oxidation method, or purification of hydrogen using a separator.

As an alternative, the fuel cell system 100 according to the present invention uses a direct methanol fuel cell (DMFC) method capable of producing electricity by supplying the fuel of the consultation directly to the electricity generating unit 111. It is also possible to employ. Such a direct methanol fuel cell fuel cell, unlike the polymer electrolyte fuel cell, does not require the reformer 123 described above.

In the fuel cell system 100 according to the embodiment of the present invention configured as described above, the coupling structure of the MEA 112 and the gasket 119 constituting the electricity generating unit 111 will be described with reference to FIGS. 4 and 5. do.

4 is an exploded perspective view illustrating a coupling structure of an electrode-electrolyte composite and a gasket according to an exemplary embodiment of the present invention, and FIG. 5 is a cross-sectional view of the coupling cross-sectional view of FIG. 4.

Referring to the drawings, as described above, the gasket 119 interposed between the edge portions between the separators 116 is made of a rubber material such as a silicone material, a fluorine material, or an olefin rubber material. The gasket 119 may include a first gasket pad 119b formed to cover an edge portion of one surface of the electrolyte membrane 112c exposed by the anode electrode 112a, and an electrolyte membrane exposed by the cathode electrode 112b. It may include a second gasket pad 119c formed to cover the other one side edge portion of 112c. In this case, an opening 119a having a predetermined area in which the MEA 112 can be located is formed in the substantially center portion of the gasket pads 119b and 119c.

In addition, the gasket 119 preferably forms the area of the opening 119a relatively smaller than the area of both electrodes 112a and 112b. That is, the edge portions of the positive electrodes 112a and 112b may be formed so as to overlap the edge portions of the opening portion 119a shown in FIG. At this time, the gasket 119 can be configured such that the edge portion of the opening 119a overlaps the edge portions of both electrodes 112a and 112b by about 1 to 2 mm.

According to the present embodiment, such a gasket 119 and the MEA 112 have an edge portion of the opening 119a of the gasket 119, which is shown in phantom in the drawing, with the corresponding edges of the positive electrodes 112a and 112b. A portion and an edge portion of the electrolyte membrane 112c exposed by the electrodes 112a and 112b are thermally compressed and bonded by a hot press method (also referred to as a 'hot press').

Specifically, the first gasket pad such that the edge portion of the opening 119a of the first gasket pad 119b covers the edge portion of the anode electrode 112a and the edge portion of the electrolyte membrane 112c exposed by the electrode. 119b is positioned on the side of the anode electrode 112a. The second gasket pad 119c may cover an edge portion of the opening 119a of the second gasket pad 119c to cover an edge portion of the cathode electrode 112b and an edge portion of the electrolyte membrane 112c exposed by the electrode. ) Is positioned on the cathode electrode 112b side. At this time, the edge portion of the opening 119a is overlapped by about 1 to 2 mm from the edge ends of both electrodes 112a and 112b, which is a hot press method for coupling the gasket 119 and the MEA 112. This is to prevent the above-mentioned hot pressure from concentrating on the edges of both electrodes 112a and 112b. In other words, when the overlapping interval is 1 mm or less, hot pressure is concentrated at the edges of both electrodes 112a and 112b, which may damage the electrolyte membrane 112c. In addition, when the overlapping interval exceeds 2 mm, the catalyst layer areas of both electrodes 112a and 112b may be substantially reduced, resulting in catalyst layer loss. In this state, when the MEA 112 and the gasket 119 are pressed by a hot press method, the edge portion of the opening 119a is thermally fused to the edge portion of the MEA 112. Here, a portion shown as an imaginary line in FIG. 5 means a gas diffusion layer formed on the anode electrode 112a and the cathode electrode 112b, respectively.

Thus, according to the embodiment of the present invention, since the edge portion of the opening portion 119a of the gasket 119 overlaps the edge portions of the positive electrodes 112a and 112b and has a heat-sealed structure by a hot press method, unlike the conventional art, It is possible to suppress the hot pressure from being concentrated at the edges of the positive electrodes 112a and 112b and the edges of the opening 119a, so that the electrolyte membrane 112c at the portion extending outside the edges of the positive electrodes 112a and 112b. Closed ends, such as being broken by hot pressure, can be prevented.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

According to the fuel cell system according to the present invention, an electrolyte membrane extending outside the edge end of both electrodes, as in the prior art, by improving the coupling structure of the gasket and the MEA so as to disperse the hot pressure concentrated at the edge end of both electrodes. It is possible to prevent the occurrence of cracks such as cracking of the site by hot pressure. Thus, the airtightness of the MEA and the separator can be improved, and ultimately, the performance of the fuel cell can be further improved.

Claims (16)

At least one electricity generating unit generating electrical energy through an electrochemical reaction between hydrogen and oxygen; A fuel supply unit supplying a fuel containing hydrogen to the electricity generation unit; And Oxygen supply unit for supplying oxygen to the electricity generation unit Including; The electricity generating unit includes an electrode-electrolyte composite (MEA) and separators disposed on both sides of the electrode-electrolyte composite, and includes a gasket interposed at an edge portion between the electrode-electrolyte composite and both separators, And the gasket overlaps an electrode edge portion of the electrode-electrolyte composite. The method of claim 1, The electrode-electrolyte composite has an anode electrode and a cathode electrode positioned on both surfaces thereof with an electrolyte membrane interposed therebetween, and configured to expose an edge portion of the electrolyte membrane outside the edge of the electrode. The method of claim 2, The gasket forms an opening in which the electrode-electrolyte composite is located, and forms an area of the opening smaller than an electrode area of the electrode-electrolyte composite. The method according to any one of claims 1 to 3, And the gasket is formed such that the edge portion of the opening covers the edge portion of the electrode by 1-2 mm. The method of claim 1, The electricity generator is made of a high temperature fuel cell operating at a high temperature of 1000 ℃ or more, A fuel cell system in which the electrolyte membrane is made of poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole] or poly [2,5-benzimidazole]. The method of claim 1, The fuel supply unit: A fuel tank for storing fuel containing hydrogen; And A fuel cell system comprising a fuel pump connected to the fuel tank. The method of claim 1, And the oxygen supply includes an air pump to suck air. The method of claim 6, The fuel supply unit includes a reformer connected to the electricity generating unit and the fuel tank to receive fuel from the fuel tank to generate hydrogen gas, and supply the hydrogen gas to the electricity generating unit. The method of claim 8, The fuel cell system is a fuel cell system comprising a polymer electrolyte fuel cell (PEMFC) method. At least one electricity generating portion comprising an electrode-electrolyte composite (MEA) and separators disposed on both sides of the electrode-electrolyte composite, The electricity generating unit includes a gasket interposed between an edge portion between the electrode-electrolyte composite and both separators, The electrode-electrolyte composite is configured such that an anode electrode and a cathode electrode are positioned on both surfaces thereof with an electrolyte membrane interposed therebetween, and an edge portion of the electrolyte membrane is exposed outside the edge of the electrode. The gasket, A stack for use in a fuel cell system that forms an opening in which the electrode-electrolyte composite is located and forms an area of the opening smaller than an electrode area of the electrode-electrolyte composite. The method of claim 10, And said gasket is a stack for use in a fuel cell system in which an edge portion of an opening thereof is formed so as to cover an edge portion of the electrode. The method of claim 10, And a gasket and an electrode-electrolyte composite formed by a hot press method. The method of claim 10, The electricity generator is made of a high temperature fuel cell operating at a high temperature of 1000 ℃ or more, A stack for use in a fuel cell system in which the electrolyte membrane is made of poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole] or poly [2,5-benzimidazole]. At least one electricity generating unit comprising an electrode-electrolyte composite (MEA) and a high-temperature fuel cell by separators disposed on both sides of the electrode-electrolyte composite, And wherein the electricity generating portion has a gasket interposed at an edge portion between the electrode-electrolyte composite and both separators and overlapping an electrode edge portion of the electrode-electrolyte composite. The method of claim 14, The gasket is a stack for use in a fuel cell system is formed to cover the edge portion of the electrode 1-2mm. The method of claim 14, The electrode-electrolyte composite is configured such that an anode electrode and a cathode electrode are positioned on both surfaces thereof with an electrolyte membrane interposed therebetween, and an edge portion of the electrolyte membrane is exposed outside the edge of the electrode. A stack for use in a fuel cell system in which the electrolyte membrane is made of poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole] or poly [2,5-benzimidazole].

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