KR20050075817A - Current collector in fuelcell applications and manufacturing method thereof, and fuelcell current collector manufactured thereby - Google Patents

Abstract

The present invention relates to a fuel cell current collector, a method for manufacturing the same, and a fuel cell having the same, which can be applied to a polymer electrolyte fuel cell stack to increase performance and chemical durability of a fuel cell.

The current collector for fuel cells according to the present invention is divided into a manifold portion in which a plurality of manifolds are formed and a fluid distribution layer corresponding portion corresponding to the fluid distribution layer of the fuel cell, and the manifold portion is made of carbon foil having excellent chemical resistance. The fluid distribution layer counterpart is made of a metal plate. Such a current collector is formed by punching a manifold in a carbon foil, punching an opening in a portion where a fluid distribution layer counterpart is to be formed, and then machining and joining a metal plate to fit it.

According to the current collector according to the present invention, when the fuel cell stack is operated, the manifold portion has chemical durability that can withstand moisture or galvanic corrosion environment, and a very uniform stress distribution can be obtained at the fluid distribution layer counterpart.

Description

CURRENT COLLECTOR IN FUELCELL APPLICATIONS AND MANUFACTURING METHOD THEREOF, AND FUELCELL CURRENT COLLECTOR MANUFACTURED THEREBY}

The present invention relates to a fuel cell, and more particularly, a current collector for a fuel cell and a manufacturing method thereof, and a fuel having the same, which can be applied to a polymer electrolyte fuel cell stack to increase performance and chemical durability of a fuel cell. It relates to a battery.

Polymer Electrolyte Fuel Cells (PEFC) is a fuel cell that uses a polymer membrane with hydrogen ion exchange characteristics as an electrolyte. It generates an electrochemical reaction using fuel gas containing hydrogen and air containing oxygen. Generates electricity and heat The polymer electrolyte fuel cell has an advantage of maintaining a high current density while operating temperature is lower than about 60 ~ 80 ℃ compared to other types of fuel cells. For this reason, the polymer electrolyte fuel cell has a fast starting capability, can be miniaturized, and can be made into a light battery, which can be applied to various fields such as a mobile power source, a car power source, and a home cogeneration plant.

The unit cell of the polymer electrolyte fuel cell includes a membrane electrode assembly (MEA) consisting of a polymer electrolyte membrane, an anode and a cathode, and a fluid distribution layer that delivers a gas used for the reaction to the electrode and discharges the reaction product. And a conductive separator for supplying the reaction gas and cooling water from the outside and separating the anode and the cathode.

The fuel cell stack is constructed by stacking such a membrane electrode assembly, a fluid distribution layer and a separator plate as necessary, and the stacked stack is pressurized by a pair of end plates connected to a pair of current collectors and connecting bars. Each unit cell is integrated without slipping or slipping. At this time, the current collector serves as a current path to the outside.

Reaction gas for electricity generation is supplied to the electrode through a manifold formed in the separation plate from the outer pipe of the stack through a gas flow path formed in the separation plate or fluid distribution layer of each unit cell. Cooling water for removing heat generated by the electrochemical reaction is supplied into the stack through the cooling water flow path formed in the separator plate of each unit cell through the manifold formed on the separator plate from the external pipe of the stack like the reaction gas. .

In addition, a gasket is disposed around the electrode and the manifold to prevent the reaction gas and the cooling water supplied to the stack from leaking out or mixing with each other. As a gasket for sealing a fuel cell, a silicon sheet or a teflon sheet reinforced with silicon, fluorine or olefin rubber or glass fiber is used.

8 is a front view illustrating a current collector of a conventional fuel cell.

Referring to FIG. 8, the current collector 300 includes a manifold of fuel gas inlet / outlets 310 and 360, a manifold of air inlet and outlet 330 and 340, and a manifold of coolant inlet and outlet 320 and 350. The folder is configured to include a tab 370 that serves as a current path to the outside. The current collector 300 typically uses a gold plated surface on a stainless steel surface, and is used by adding a nickel buffer layer to improve adhesion between the stainless surface and the gold plated layer. The current collector 300 is a stainless steel plated gold interface at the contact point of the current collector inlet / outlet manifold area when the fuel cell stack is operated for a long time because of the galvanic corrosion environment and fuel gas containing moisture. Corrosion occurs, and the corrosion product reduces fuel cell performance, such as contaminating the fuel cell stack or lowering the electrical conductivity of the current collector.

In order to improve the performance of end plates or current collectors, Korean Patent Publication No. 2002-0084186 discloses coating an end plate or current collector with an active electrocatalyst containing ruthenium oxide and optionally ruthenium oxide and non-fluorinated metal oxide. It discloses a method of using, but there is a problem such as the hassle of having to coat the active electrocatalyst material in a separate process and the resulting manufacturing cost increases.

The present invention was devised to solve the above problems, the object of which is to use a carbon foil and a metal plate as a material to produce a region corresponding to the manifold region and the fluid distribution layer reaction region of different materials, fuel It is possible to prevent interfacial corrosion during battery operation and to reduce the thickness to provide a lightweight and inexpensive current collector for fuel cells and a method of manufacturing the same.

Another object of the present invention is to provide a fuel cell having high performance and high reliability by eliminating interfacial corrosion that may occur in the manifold region of a current collector that induces fuel and reducing gas (air, oxygen).

In order to achieve the above object, a fuel cell according to the present invention comprises a fuel cell stack having at least one unit cell stacked thereon, wherein the unit cell is formed on a polymer electrolyte membrane and both surfaces thereof. A membrane electrode assembly (MEA) including an anode and a cathode formed; A pair of fluid distribution layers disposed on both sides of the membrane electrode assembly so as to be adjacent to the anode and the cathode; The manifold is tightly coupled to the outer surface of each fluid distribution layer, and a plurality of flow paths are formed on a surface corresponding to the fluid distribution layer to form a reaction zone, and a passage of a reaction gas at the periphery of the reaction zone. ) A pair of separator plates in which regions are formed. In addition, a pair of current collectors are disposed to be adjacent to the outside of the separator plates of the unit cells disposed at both outermost sides, and the current collectors correspond to the fluid distribution layer corresponding to the fluid distribution layer with the separator plates therebetween. And a manifold part corresponding to the manifold area of the separator. At this time, the manifold portion of the current collector is made of carbon foil, and the fluid distribution layer counterpart is made of a metal plate.

The current collector has a drawing tab extending from the fluid distribution layer counterpart and drawn out to serve as a current path to the outside, and the draw tab is made of the same metal material as the fluid distribution layer counterpart.

The metal plate forming the fluid distribution layer corresponding part of the current collector may be made of a material selected from the group consisting of stainless steel, brass, aluminum, and aluminum alloy.

On the other hand, the current collector may have a thickness of the carbon foil forming the manifold portion is thicker than the thickness of the metal plate forming the reaction region, the thickness of the carbon foil is in the range of 10 to 100㎛ than the thickness of the metal plate. It can be formed thicker in.

The manifold portion of the current collector may further have a sealing member formed along the outer manifold of each manifold formed therein.

The carbon foil constituting the manifold portion of the current collector is preferably formed so that the bulk density is in the range of 1.5 to 1.8 g / cm 3.

It may further comprise a carbon foil plate having a manifold corresponding to the manifold of the current collector, disposed adjacent to at least one side of both sides of the current collector. At this time, it is preferable that the sealing member is formed along each manifold outer edge formed on the carbon foil plate.

On the other hand, the fuel cell current collector manufacturing method according to an embodiment of the present invention, the fuel cell current collector is applied to the fuel cell stack is laminated with a unit cell including a membrane electrode assembly, a fluid distribution layer and a separator plate. CLAIMS 1. A process for making a process comprising the steps of: preparing a carbon foil having any thickness, bulk density, and size (width x length); Forming a manifold corresponding to the manifolds of the separation plate in the carbon foil; Forming an opening in a portion corresponding to the fluid distribution layer with the separator plate in the carbon foil; Processing the metal plate to fit the opening of the carbon foil, and then bonding the metal plate; And pressing the bonded carbon foil and the metal plate at a predetermined pressure in a press.

In this case, the forming of the manifold may be formed by punching a portion of the carbon foil corresponding to the manifolds of the separation plate and forming an opening in a corresponding portion of the fluid distribution layer. The step may be formed by punching a portion of the carbon foil corresponding to the fluid distribution layer.

The carbon foils are thicker than the thickness of the metal plate in a range of 0.03 to 0.07 mm, and are bonded to each other, and pressed together in the pressing step.

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

1 is an exploded perspective view showing a fuel cell according to an embodiment of the present invention.

Referring to FIG. 1, a unit cell that forms the basis of a fuel cell stack 100 includes a membrane electrode assembly (MEA) 120, a fluid distribution layer 125, and a separator 130 sequentially stacked. The unit cell constituted by the number of cells stacked in the stack 100 according to the output of the fuel cell, that is, the membrane electrode assembly 120, the fluid distribution layer 125, and the separator 130. The number of is determined. A pair of current collectors 150 and end plates 160 are coupled to both sides of the stack structure of the fuel cell stack 100 on both sides.

The membrane electrode assembly 120 includes two electrodes, an anode 123 and a cathode (located on the opposite side of the anode), separated by the polymer electrolyte membrane 121, and the fluid distribution layer 125 is disposed on these electrodes. These are covered while being disposed adjacent to each other. The fluid distribution layer 125 has a substantially rectangular plane and protects the electrodes and supplies hydrogen and air necessary for the reaction to the electrodes.

The separator 130 is tightly coupled to the outer surface of the fluid distribution layer 125, and a plurality of flow paths 132 are formed on a surface corresponding to the fluid distribution layer 125. The flow path 132 of the separation plate 130 forms a reaction zone by combining with the fluid distribution layer 125 to form a hydrogen flow passage or an air flow passage, and a manifold region forming a passage of a reaction gas at the periphery of the reaction zone. Is formed. The flow path 132 of the reaction region is connected to the manifold 140 of the manifold region to receive the reaction gas from the outside of the stack 100.

The separating plate 130 prevents hydrogen and air from mixing in the fuel cell and electrically connects the membrane electrode assembly 120, and serves as a mechanical support of the stacked unit cells. In addition, the reactor flows evenly to the electrode, prevents the membrane from drying through proper moisture management, and discharges the water generated from the cathode.

2 is a partially exploded perspective view illustrating a portion of a fuel cell according to an embodiment of the present invention.

Referring to FIG. 2, the current collector 150 includes a manifold that communicates with the manifold 140 of the separator 130. Specifically, the fuel gas inlet and outlet manifolds 161 and 166 may be used. , Air inlet and outlet manifolds 163 and 164 and cooling water inlet and outlet manifolds 162 and 165 are formed. Accordingly, the current collector 150 corresponds to the manifold unit 156 including the manifolds 161, 162, 163, 164, 165, and 166 and the fluid distribution layer corresponding to the fluid distribution layer 125. It may be divided into the unit 151, and also includes a withdrawal tab 153 extending from the fluid distribution layer counterpart 151 to be drawn outward to serve as a current path to the outside. Since the fluid distribution layer 125 is combined with the flow path 132 of the separation plate 130 to form a reaction region, the fluid distribution layer counterpart 151 of the current collector 150 eventually becomes a portion of the separation plate 130. Corresponds to the reaction zone.

Meanwhile, in the present embodiment, the manifold portion 156 of the current collector 150 is made of carbon foil, and the fluid distribution layer counterpart 151 is made of a metal plate. The lead tab 153 extending from the fluid distribution layer counterpart 151 is made of a metal plate similarly to the fluid distribution layer counterpart 151.

Carbon foil constituting the manifold portion 156 of the current collector 150 has a bulk density while delivering a uniform pressure when the fuel cell stack 100 is fastened, and should also have excellent electrical conductivity. It is preferable to use those having a density in the range of 1.5 to 1.8 g / cm 3. If the volume density is less than 1.5 g / cm 3, the thickness of the current collector 150 is severely deformed when the fuel cell stack is fastened, which causes problems such as leakage of the reaction gas and an increase in contact resistance. In one case, there is a problem that the manufacturing cost of the carbon foil is increased. Since the carbon foil is excellent in chemical durability, when applied to the manifold portion 156 of the current collector 150, no interfacial corrosion occurs during fuel cell operation.

The metal plate forming the fluid distribution layer counterpart 151 of the current collector 150 may be made of a material such as stainless steel, brass (Cu-Zn Alloy), aluminum, an aluminum alloy, or the like. Gold plating is used to reduce contact resistance.

In the current collector 150, the thickness of the carbon foil is made thicker than the thickness of the metal plate to further increase the sealing safety of the manifold portion 156, which is a passage for the reaction gas, and further improves the fuel cell. Due to the pressure at the time of stack fastening, the current collector 150 having the same thickness as the carbon foil and the metal plate can be easily manufactured.

The thickness of the carbon foil constituting the manifold portion 156 is preferably formed thicker within the range of 10 to 100 μm than the thickness of the metal plate forming the fluid distribution layer counterpart 151, more preferably 10 to 50. The thickness of the carbon foil is formed thicker than the thickness of the metal plate within the range of μm.

Each of the manifolds 161, 162, 163, 164, 165, and 166 constituting the manifold portion 156 of the current collector 150 has a sealing member along each outer edge thereof, as shown in FIG. 3. 157 is disposed. The sealing member 157 may be made of a sealing gasket. By arranging the sealing member 157, it is possible to maintain the airtightness of the reaction gas and the like delivered through the manifolds 161, 162, 163, 164, 165, and 166.

Hereinafter, a method of manufacturing a current collector of a fuel cell according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5.

4 is an exploded perspective view illustrating a current collector of a fuel cell according to an embodiment of the present invention.

In order to manufacture a current collector for a fuel cell, first, a carbon foil having a predetermined thickness, volume density, and size (width × length) is prepared. For example, a carbon foil having a thickness t _c of 1 mm, a volume density of 1.8 g / cm 3, and a size of 140 mm × 250 mm can be prepared.

In the prepared carbon foil, as shown in FIG. 4, manifolds 161, 162, 163, 164, 165, and 166 which are fluid passages are formed, and the fluid distribution layer counterpart 151 and the tab 153 are formed. An opening 168 that can be fitted is formed. The manifolds 161, 162, 163, 164, 165, and 166 and the openings 168 corresponding to the fluid distribution layer counterpart 151 and the tab 153 may be formed by punching. .

Next, a metal plate formed according to the shapes of the fluid distribution layer counterpart 151 and the tab 153 is prepared and bonded to the processed carbon foil. At this time, the side of the metal plate and the corresponding side of the processed carbon foil opening 168 may be bonded with an adhesive.

Wherein the thickness (t _c ) of the carbon foil is adopted in the range of 0.03 to 0.07 mm thicker than the thickness (t _m ) of the metal plate and processed as described above to join each side with an adhesive, then join The obtained carbon foil and the metal plate are pressed at a predetermined pressure to complete the current collector 150. For example, by applying a metal plate having a thickness (t _m ) of 0.95 mm to a carbon foil having a thickness (t _c ) of 1 mm, it may be pressed at a pressure of 100 kg / cm 2. As described above, the thicknesses of the manifold part 156 and the fluid distribution layer counterpart 151 are processed differently and then pressed to manufacture the manufacturing process defect rate according to the thickness variation of the carbon foil and the metal plate in the manufacturing step. It is possible to provide a current collector for a fuel cell having a simple method and excellent reproducibility.

In the current collector 150, which is thus completed, the manifold portion 156 made of carbon foil can be manufactured to have the same thickness as the fluid distribution layer counterpart 151 made of a metal plate, and the manifold portion 156 may be made thicker than the fluid distribution layer counterpart 151 in the range of 10 to 100 μm.

5 is an exploded perspective view illustrating a current collector of a fuel cell according to another embodiment of the present invention.

The current collector according to the present embodiment has a three-layer assembly structure, and a pair of carbon foil plates 257 and 258 are disposed adjacent to both sides of the current collector 150 of the above-described embodiment, and one current collector is provided. Constitute the entire assembly 250.

As described above, the current collector 150 includes a manifold part 156 made of carbon foil, a metal plate, and a fluid distribution layer counterpart 151 having a lead tab 153, including a plurality of manifolds. ) Are bonded to each other.

The carbon foil plates 257 and 258 disposed adjacent to both sides of the current collector 150 are made of carbon foil as a whole, and the manifolds 260 communicating with the manifolds formed in the current collector 150, respectively. , 270 is also formed. In addition, sealing gaskets 261 and 271 are formed along the periphery of each of the manifolds 260 and 270 to maintain the airtightness of the reaction gas delivered through the manifolds 260 and 270.

In order to manufacture the current collector assembly 250 according to the present embodiment, first, the current collector 150 is prepared. Since the manufacturing method of this current collector 150 has been described above, it is omitted here.

Next, the pair of carbon foil plates 257 and 258 are processed to match the shape of the outer edge of the current collector 150. For example, a carbon foil plate having a thickness of 1 mm and a bulk density of 1.8 g / cm 3 may be used.

The manifolds 260 and 270 are punched into the carbon foil plates 257 and 258 corresponding to the manifolds of the current collector 150, and the outer edges of the manifolds 260 and 270, respectively. The sealing gaskets 261 and 271 are disposed to prevent leakage of the reaction gas along the lines.

Next, the pair of carbon foil plates 257 and 258 thus prepared are adjacently disposed to communicate manifolds on both sides of the current collector 150 to complete the current collector assembly 250 having a three-layer structure. The current collector assembly 250 having a three-layer structure accommodates variations in thicknesses of the carbon foil plates 257 and 258 that may occur in the current collector manufacturing process, thereby stably increasing the yield in mass production. have.

In the above description, the carbon foil plates 257 and 258 disposed adjacent to both sides of the current collector 150 have been described as examples, but the carbon foil plates are disposed adjacent to both sides of the current collector 150 to form the current collector assembly. It may be formed.

Experimental Example

The current collector and the current collector according to the embodiment of the present invention were operated under the same conditions, and the corrosion levels of the manifolds were observed in FIGS. 6 and 7.

In other words, the conventional current collector made only of a gold plated metal plate on brass (Cu-Zn Alloy) was mounted on a fuel cell stack, and the photograph taken after operation for 150 hours at a current density of 300 mA / cm 2 was shown in FIG. 6. 7 shows a photograph taken after 150 hours of operation at a current density of 300 mA / cm 2 by mounting the current collector according to the present invention on a fuel cell stack.

As shown in Figure 6, it can be seen that the corrosion occurs around the manifold which is the passage of the reaction gas in the conventional current collector. On the other hand, as shown in Figure 7, in the current collector according to an embodiment of the present invention, since the manifold portion, which is a passage of the reaction gas, is made of chemically stable carbon foil, corrosion causing material destruction and an increase in contact resistance. It can be seen that the phenomenon does not occur.

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.

As described above, according to the current collector for fuel cell according to the present invention, the manifold portion that serves as a fluid passage such as a reaction gas containing water or cooling water is made of carbon foil, and the fluid distribution layer counterpart is made of a metal plate. By having excellent chemical durability, there is little interfacial resistance with a separator made of graphite or carbon material and excellent electrical conductivity can be obtained.

In addition, by using carbon foil and a metal plate as a material of the current collector for fuel cells, cost reduction and weight reduction can be achieved.

1 is an exploded perspective view showing a fuel cell according to an embodiment of the present invention.

2 is a partially exploded perspective view illustrating a portion of a fuel cell according to an embodiment of the present invention.

3 is a front view illustrating a current collector of a fuel cell according to an embodiment of the present invention.

4 is an exploded perspective view illustrating a current collector of a fuel cell according to an embodiment of the present invention.

5 is an exploded perspective view illustrating a current collector of a fuel cell according to another embodiment of the present invention.

6 is a photograph of a manifold part to check the degree of corrosion after operation of a fuel cell using a conventional current collector.

7 is a photograph of a manifold part to check the corrosion degree after operation of a fuel cell to which a current collector according to an embodiment of the present invention is applied.

8 is a front view illustrating a current collector of a conventional fuel cell.

Claims (16)

In a fuel cell stack having at least one unit cell, The unit cell, A membrane electrode assembly (MEA) comprising a polymer electrolyte membrane and an anode and a cathode formed on both surfaces thereof; A pair of fluid distribution layers disposed adjacent to the anode and the cathode on both sides of the membrane electrode assembly; The manifold is tightly coupled to the outer surface of each fluid distribution layer, and a plurality of flow paths are formed on a surface corresponding to the fluid distribution layer to form a reaction zone, and a passage of a reaction gas at the periphery of the reaction zone. ) A pair of separator plates in which the region is formed, A pair is disposed to be adjacent to an outer side of the separator plate of the unit cell disposed at both outermost sides, and corresponding to the fluid distribution layer corresponding to the fluid distribution layer with the separation plate therebetween and corresponding to the manifold area of the separator plate. Including a current collector including a manifold portion, A fuel cell, characterized in that the manifold portion of the current collector is made of carbon foil. The method of claim 1, A fuel cell, characterized in that the fluid distribution layer corresponding portion of the current collector is made of a metal plate. The method of claim 2, The current collector extends from the fluid distribution layer counterpart and is drawn outward to have a drawing tab serving as a current path to the outside. The draw tab is a fuel cell, characterized in that made of the same metal material as the fluid distribution layer counterpart. The method of claim 2, The metal plate is a fuel cell, characterized in that made of a material selected from the group consisting of stainless steel, brass, aluminum, aluminum alloy. The method of claim 2, The current collector is a fuel cell, characterized in that the thickness of the carbon foil constituting the manifold portion is formed thicker than the thickness of the metal plate constituting the reaction region portion. The method of claim 5, The thickness of the carbon foil is a fuel cell that is formed thicker in the range of 10 to 100㎛ than the thickness of the metal plate. The method of claim 6, The thickness of the carbon foil is a fuel cell that is formed thicker than the thickness of the metal plate in the range of 10 to 50㎛. The method of claim 1, The manifold portion of the current collector, characterized in that the fuel cell characterized in that made of a carbon foil further formed with a sealing member along the outer manifold formed on each manifold. The method of claim 1, The carbon foil forming the manifold portion of the current collector is formed so that the bulk density is in the range of 1.5 to 1.8 g / cm 3. The method of claim 1, And a carbon foil plate disposed adjacent to at least one of both surfaces of the current collector while having a manifold corresponding to the manifold of the current collector. The method of claim 10, A fuel cell, characterized in that the sealing member is formed along the outer periphery of each manifold formed on the carbon foil plate. A method of manufacturing a current collector for a fuel cell applied to a fuel cell stack in which a unit cell including a membrane electrode assembly, a fluid distribution layer, and a separator is stacked, Preparing a carbon foil having any thickness, bulk density and size (horizontal × vertical); Forming a manifold corresponding to the manifolds of the separation plate in the carbon foil; Forming an opening in a portion corresponding to the fluid distribution layer with the separator plate in the carbon foil; Processing the metal plate to fit the opening of the carbon foil, and then bonding the metal plate; Pressing the bonded carbon foil and the metal plate at a predetermined pressure in a press; A current collector manufacturing method for a fuel cell comprising a. The method of claim 12, Forming the manifold and forming an opening in the fluid distribution layer counterpart, respectively, Punching a portion of the carbon foil corresponding to the manifolds of the separator plate, and punching the portion of the carbon foil corresponding to the fluid distribution layer is formed by the current collector manufacturing method for a fuel cell. . The method of claim 12, The carbon foil is thicker than the thickness of the metal plate is provided in the range of 0.03 to 0.07 mm thicker is bonded to each other, the current collector manufacturing method for a fuel cell, characterized in that pressed together in the pressing step. A current collector for a fuel cell, which is manufactured according to the method according to any one of claims 12 to 14. A fuel cell comprising a current collector for a fuel cell manufactured according to the method according to any one of claims 12 to 14.