KR101145574B1 - Fuel cell stack having current collector with coolant flow - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell stack having a current collector having a coolant flow path, wherein both sides of a first flow path portion and a first flow path portion formed of a coolant flow path formed on a first surface and a reaction gas flow path formed on a second surface are provided. A separator plate body including a manifold portion formed in each of the plurality of separator plates, a fuel cell separator plate in which two separator plate bodies are bonded to each other, and a membrane-electrode assembly (MEA) disposed between the plurality of fuel cell separator plates. Including, but a plurality of the fuel cell separator plate of the edge of the fuel cell separator plate has a stack having an outermost separator plate body consisting of one piece, the outermost separator plate body has an area corresponding to the outermost shell Current collector and second current collector having a second flow path portion corresponding to the cooling water flow path formed in the separation plate main body The present invention relates to an outer plate and an end plate for protecting the stack.

Description

FUEL CELL STACK HAVING CURRENT COLLECTOR WITH COOLANT FLOW}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell stack having a current collector having a cooling water flow path, wherein a separator and a gas diffusion layer (GDL) formed in an outermost part of a conventional fuel cell stack are removed, and an outermost separator is formed. By forming a current collector corresponding to the main body, a technique for reducing the thickness of the fuel cell stack, the contact resistance and improve the efficiency of the fuel cell.

A fuel cell is a device that produces electricity electrochemically by using hydrogen gas and oxygen gas, and converts fuel (hydrogen) and air (oxygen) continuously supplied from the outside into electrical energy and heat by an electrochemical reaction. to be.

Such a fuel cell generates electric power using an oxidation reaction at an anode and a reduction reaction at a cathode. In this case, a membrane-electrode assembly (MEA) containing platinum or platinum-ruthenium metal or the like is used for the oxidation / reduction electrode as a component for promoting oxidation and reduction reactions.

Currently, the above-described fuel cell has been researched and used for various purposes as an alternative power source, and representative examples thereof include a polymer electrolyte membrane fuel cell (PEMFC). Polymer fuel cells have various advantages, such as high output density and energy conversion efficiency, can operate at low temperature below 80 ℃, and can be miniaturized and sealed. Therefore, it is being used as an alternative power source in various fields such as pollution-free automobiles, household power generation systems, mobile communication equipment, military equipment, and medical equipment.

1 is an exploded cross-sectional view showing a fuel cell stack according to the prior art.

Referring to FIG. 1, a fuel cell stack is formed by first joining two separator plates, that is, a first separator plate 10 and a second separator plate 20, to form a coolant flow path therein, and a membrane electrode on both sides of the outside. The junction 40 includes a basic cell structure that can be coupled to form power.

Here, a gas diffusion layer (GDL) 50 which assists the diffusion of the reaction gas is formed between each of the separators 10 and 20 and the membrane-electrode assembly 40, and the outer region of each of the separators 10 and 20 is formed. The gasket 30 is formed to prevent the leakage of gas.

The basic cell structure is repeatedly coupled to two or more layers to form a fuel cell stack. End plates 70 are disposed at both ends of the fuel cell stack for fastening the stack components. At this time, the end plate 70 includes a current collector (Current Collector, 60) for power transmission, the current collector 60 is a fastening bolt 80 for applying the current passing through the end plate (70) It is provided including.

At this time, the outermost separation plate and the current collector 60 are not completely connected by the gasket 30 and the flow path, and have a separation interval. And, such a spacing has caused a problem that can not properly transfer the current coming from the stack to the current collector (60).

In order to solve this problem, a gas diffusion layer (GDL) 50 is further included between the current collector 60 and the outermost separator, so as to secure a reaction gas flow path for electricity generation. In addition, a method of improving conductivity by manufacturing a gas diffusion layer (GDL) 50 using a carbon material so as to easily transfer electricity generated from the stack to the current collector 60 is also used.

However, the indirect conduction method using carbon does not transfer electricity generated from the stack to the current collector 60 as it is and does not help to improve the performance of the fuel cell.

In addition, the addition of the gas diffusion layer (GDL) 50 causes a problem of an increase in cost for manufacturing a fuel cell stack and an unnecessary increase in the thickness of the stack. Therefore, there is a problem in that the efficiency of the fuel cell relative to the cost performance is reduced.

The present invention removes the separator plate body and the gas diffusion layer disposed on both outer sides of the fuel cell stack, allows the current collector to be directly bonded to the fuel cell stack outermost separator plate body, and forms a cooling water flow path in the junction. It is an object of the present invention to provide a fuel cell stack having a current collector having a coolant flow path formed to be capable of minimizing the size of the fuel cell stack and maximizing current collection efficiency.

The fuel cell stack according to the present invention includes a separation plate including a first flow path part including a coolant flow path formed on a first surface and a reaction gas flow path formed on a second surface, and a manifold part formed on both sides of the first flow path. A main body, a separator for fuel cells in which two sheets of the separator main body are bonded to each other, and a membrane-electrode assembly (MEA) disposed between each of the plurality of fuel cell separators, wherein both edges of the plurality of fuel cell separators are included. The fuel cell separator includes a stack having a single outermost separator main body, an area corresponding to the outermost separator main body, and a second flow path corresponding to a coolant flow path formed in the outermost separator main body. It includes a current collector having a portion (Current Collector) and an end plate for protecting the outer portion of the current collector and the stack (End Plate) .

The fuel cell separator may include a gasket formed to be joined to each other so that the cooling water flow paths face each other, and to be formed around a periphery of each of the separator plates and a portion requiring sealing. And a gasket having a shape corresponding to a gasket formed in the outermost separator plate body, wherein the current collector protrudes from the surface of the end plate toward the stack. Is characterized in that it comprises at least one of copper (Cu), nickel (Ni), iron (Fe), titanium (Ti), chromium (Cr), aluminum (Al) and conductive carbon (C), the current collector All are gold (Au), platinum (Pt), metal nitrides A _x B _y N (A: Cr, Ti, Al, B: Cr, Ti, Al, C) and metal carbides A _x C (A: Cr, Ti , Al) characterized in that the surface is coated with a material containing at least And a gas diffusion layer (GDL) disposed in a region between the fuel cell separator and the membrane-electrode assembly (MEA), except for a region between the outermost separator body and the current collector in the stack. It is characterized in that, the current application and collection of the current collector is characterized in that made through the fastening bolt for applying the current passing through the end plate.

The fuel cell stack having a current collector having a coolant flow path according to the present invention forms a current collector having a structure in which a coolant flow path can be formed between the joining surfaces while being directly bonded to the fuel cell separator of the outermost part. The number of gas diffusion layers (GDLs) used in fuel cells can be reduced.

That is, not only the gas diffusion layer (GDL) between the current collector and the fuel cell separator can be omitted, but also the outermost separator body can be reduced. It is possible to improve the performance of fuel cells without increasing the area, volume, and volume, and to increase the production efficiency.

In addition, the current collector provided with the cooling water flow path provided by the present invention is more resistant to space deformation than the conventional current collector, and provides the ability to support the fuel cell stack more efficiently.

Therefore, the fuel cell stack including the current collector having the coolant flow path according to the present invention has an effect of more reliably preventing deformation of the separator and the gasket, and facilitating stacking between the separators.

Hereinafter, a fuel cell stack having a current collector having a cooling water flow path according to the present invention will be described in detail.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent with reference to the embodiments and drawings described in detail below. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, only the embodiments are to make the disclosure of the present invention complete, it is common in the art It is provided to fully inform those skilled in the art of the scope of the invention, which is to be defined only by the scope of the claims.

That is, the following detailed description of the present invention will be described taking a polymer electrolyte membrane (PEMFC) as an example.

However, this is for convenience of explanation and understanding, and the technical spirit of the present invention should not be understood as necessarily limited to the polymer fuel cell. In particular, as a fuel cell using a polymer membrane as an electrolyte, SPEFC (Solid Polymer Electrolyte Fuel Cell), SPFC (Solid Polymer Fuel Cell), PEFC (Polymer Electrolyte Fuel Cell) Direct Methanol Fuel Cell (DMFC) and Polymer Electrolyte Membrane Fuel Cell (PEMFC) Since it is also used in terms such as), it should be understood that the present invention is generally applied to the fuel cell field including the current collector.

FIG. 2 is an exploded cross-sectional view illustrating a fuel cell stack according to an exemplary embodiment of the present invention, and is shown with a predetermined space in order to clarify the connection relationship of each component. However, the actual form takes a form in which each of the following components is tightly compressed.

First, as the main configuration of the fuel cell stack 200 according to the present invention, the fuel cell separator 120, the membrane-electrode assembly 140, and the gas diffusion layer 150 are formed. In addition, an end plate 170 for protecting the inside of the fuel cell stack and collecting current is formed at both sides of the outermost separator plate bodies 110a and 110b.

Here, the fuel cell stack according to the present invention has a structure in which electricity generated in the membrane-electrode assembly 140 is collected and output to the current collector 160 formed in the end plate 170. In this case, the current collector 160 is formed to have a structure that is directly bonded to the outermost separator plate bodies 110a and 110b so as to expand the area by the size of the separator plate for fuel cell and form a cooling water flow path. In addition, the current collector 160 according to the present invention can be integrally formed on the inner wall of the end plate 170, and formed in the form protruding from the end plate 170, it is possible to widen the range of application.

According to the present invention, the contact resistance of the current collector 160 can be reduced by using the above structure, and the thickness of the fuel cell stack can be reduced by reducing the number of gas diffusion layers 150.

Hereinafter, the present invention will be described in more detail with reference to FIG. 2.

First, the fuel cell stack includes a plurality of fuel cell separator plates 120. Here, only a part of the fuel cell separator 120 is shown, but in practice, several tens to hundreds are stacked to form a stack.

The material of the separator plate 120 used in the present invention may be a metal separator plate made of stainless steel as a main component, a composite separator plate formed of a mixture of metal and graphite, a carbon separator plate using a carbon composite material, and the like. The present invention is not limited by the material.

In addition, in the present invention, the separator plate 120 for fuel cell uses a form in which two separator plates are combined as one separator plate. That is, the two separation plate main bodies 100 and 110 including the flow path part including the cooling water flow path formed on the first surface and the reaction gas flow path formed on the second surface, and the manifold parts formed on both sides of the flow path part are joined. Has a modified form. At this time, it is preferable that the cooling water flow paths are joined to face each other so that the cooling water flow path is formed at the center of the separation plate 120.

Here, the pleated form formed in the sawtooth shape is shown as a cooling water flow path or a reaction gas flow path, and the manifold portion is omitted since it does not appear in the cross-sectional view.

Next, a gasket 130 is formed at the periphery of each of the separation plate bodies 100 and 110 and other portions requiring sealing. At this time, the gasket 130 is preferably formed of a material capable of maintaining airtightness such as silicon and rubber, and the gaskets of the surfaces (cooling water flow path forming surfaces) to which the separator plates 100 and 110 are bonded to each other are provided between cooling surfaces. It is preferable to form the airtightness of the cooling water while keeping the contact resistance of the low, and the gasket 130 of the surface on which the reaction gas flow path is formed is a membrane-electrode assembly (MEA) or a gas diffusion layer (GDL) bonded to the reaction gas flow path. In consideration of the thickness of the), it is preferable to form the airtightness in the gas diffusion process.

Next, a membrane-electrode assembly (MEA) 140 is disposed between the separator plates 120 for fuel cells. In this case, the membrane-electrode assembly 140 is a device in which the electrolyte and the electrode are integrally bonded to generate electricity. The membrane-electrode assembly 140 may include a platinum or platinum-ruthenium metal electrode in the polymer electrolyte membrane.

Next, the gas diffusion layer 150 may be further formed in the region between the separator 120 and the membrane-electrode assembly 140. At this time, the gas diffusion layer 150 according to the present invention is preferably formed in the form of a coating layer containing at least any one of carbon black particles, fluoropolymers and graphite particles and carbon particles.

Therefore, the gas diffusion layer 150 is formed in the form of a protective film that protects both sides of the membrane-electrode assembly 140, and the thickness shown in FIG. 2 is exaggerated as an inevitable measure for highlighting the gas diffusion layer 150. It must be understood.

Next, a current collector 160 is formed which is joined to the separator plate bodies 110a and 110b disposed at both outermost sides of the stack. That is, in the present invention, in the structure of the fuel cell separator 120 formed at the center of the stack, the outermost separator body 110a and 110b having a single structure, in which one outermost separator body is omitted, are positioned on both sides of the stack. Then, the current collector 160 is to be able to serve as the remaining separator body.

Therefore, the current collector 160 according to the present invention should have an area corresponding to that of the separator body included in the stack. This generally has an area larger than that of the current collector formed, and as the area of the conductor is increased, the flow of current is improved. Thus, the current collector 160 according to the present invention may also improve current collection efficiency. Can be. In addition, the area of the current collector 160 does not have to exactly match the separator body, and may be formed in a shape having a smaller area. However, it should be formed to be larger than the area that can include all of the gasket regions described below.

In addition, by forming the cooling water flow path 165 on the surface of the current collector 160, the cooling in the end plate 170 can be performed smoothly, it is also possible to improve the cooling efficiency of the fuel cell stack.

In addition, as compared to the fuel cell stack of FIG. 1, two fuel cell stacks and two outermost gas diffusion layers are removed as a result, thereby reducing the thickness of the fuel cell stack. This induces an effect that can save space and reduce the fuel cell stack manufacturing cost, and can also easily change the manufacturing process of the fuel cell by improving the convenience of fastening.

As the material constituting the current collector 160 of the present invention described above, it is preferable to use a material having high electrical conductivity and inert to battery reaction. Preferred examples of the material include metal materials which are not alloyed in the electrochemical reaction.

Specific examples of such metal materials may be copper (Cu), nickel (Ni), iron (Fe), titanium (Ti), chromium (Cr), aluminum (Al), conductive carbon (C), and the like. May be used alone or in the form of an alloy. And other stainless steels may also be used.

In addition, the current collector 160 according to the present invention is gold (Au), platinum (Pt), metal nitride A _x B _y N (A: Cr, Ti, Al, B: Cr, Ti, It is preferable to use a surface coated with a material containing at least one of Al, C) and metal carbide A _x C (A: Cr, Ti, Al). In this case, the coating layer (not shown) may be formed only on one surface bonded to the outermost separator plate bodies 110a and 110b, and may be formed on all surfaces of the current collector 160.

In addition, the current collector 160 according to the present invention may include a gasket having a structure corresponding to the gasket 130 formed on the outermost separation plate main body (110a, 110b) in order to ensure electrical conductivity and airtightness. Here, the gasket 130 formed on the outermost separating plate bodies 110a and 110b and the gasket formed on the current collector 160 may be combined to be represented as one gasket, and may also share one gasket. Can be displayed.

Meanwhile, the end plate 170 compresses the separator 120, the gas diffusion layer 150, and the membrane-electrode assembly 140 so that the airtightness of the stack can be maintained, and the current collector 160 is pressed. Perform the function of fixing. At this time, the current collector 160 is fixed by the fastening bolt 180 for applying through the current end plate 170.

In addition, the current collector 160 according to the present invention may be formed in a form embedded in the inner wall of the end plate 170, may also be formed in a form protruding from the surface of the end plate 170. In such a structure, since the current collector 160 almost covers the inner wall of the end plate 170, the inner wall of the end plate 170 may be corroded in comparison with the structure of FIG. 1. It can be seen that there is little risk.

That is, referring to the structure of FIG. 1, while the reaction gases containing water are injected into the region between the outermost fuel cell separator and the end plate through the gas diffusion layer, a part of the current collector or the end plate is galvanic in water. Problems with galvanic corrosion may occur.

When the fuel cell stack is operated for a long time in this state, corrosion products due to corrosion are circulated in the fuel cell stack. In this case, the corrosion product contaminates the fuel cell stack (for example, the catalyst in the stack), which severely affects the durability of the fuel cell stack. However, the fuel cell stack having the current collector 160 having the coolant flow path 165 according to the present invention can prevent the corrosion problem as described above.

Accordingly, the current collector 160 according to the present invention is preferably formed in a structure capable of completely sealing the reaction gas flow paths of the outermost separator plate bodies 110a and 110b.

As described above, the current collector according to the present invention has an area that extends as much as the size of the separator plate body and is formed to include a cooling water flow path, so that when the fuel cell stack is fastened, the current collector of the separator plate body corresponds to the outermost separator plate body. At the same time it is formed into a structure that can improve the current collection efficiency.

As such, when the current collector having the cooling water flow path is used, since the corrosion problem is not limited, durability can be improved, and electrical conductivity can be significantly increased, thereby maximizing the efficiency of the fuel cell.

In addition, since the current collector according to the present invention has a structure capable of omitting the outermost fuel cell separator and the gas diffusion layer in addition to the current collector efficiency improving function, it is possible to reduce the thickness of the fuel cell stack. Therefore, according to the present invention, fuel cell stack manufacturing time and manufacturing cost can be saved, and the convenience of stack fastening can be improved, thereby simplifying the manufacturing process.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above embodiments and can be modified in various forms, and having ordinary skill in the art to which the present invention pertains. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1 is an exploded cross-sectional view showing a fuel cell stack according to the prior art.

Figure 2 is an exploded cross-sectional view showing a fuel cell stack according to an embodiment of the present invention.

Claims (8)

The separator plate main body and the separator plate main body each including a first flow path part including a cooling water flow path formed on the first surface and a reaction gas flow path formed on the second surface, and a manifold part formed on both sides of the first flow path. A fuel cell separator plate which is bonded to each other, and a membrane-electrode assembly (MEA) disposed between each of the plurality of fuel cell separator plates, wherein the fuel cell separator plate at each edge of the plurality of fuel cell separator plates is one sheet. A stack having an outermost separation plate body made up of; A current collector electrically contacting the outermost separator body of the stack and having a second flow path part corresponding to the cooling water flow path formed in the outermost separator plate body; An end plate protecting an outer portion of the current collector and the stack; A gas diffusion layer (GDL) disposed in an area between the fuel cell separator and the membrane-electrode assembly (MEA), except for an area between the outermost separator plate body and the current collector in the stack; And The fuel cell separator includes a gasket formed to be bonded to each other so that the cooling water flow paths face each other, and formed on the periphery of each of the separator plates and a portion requiring sealing. The current collector has an area corresponding to each of the plurality of separator plates for fuel cells, and a portion of the current collector is embedded in an inner wall of the end plate, and the remaining portion except the portion protrudes from the surface of the end plate in the stack direction. Become, Current application and collection of the current collector is made through a fastening bolt for applying the current passing through the end plate, The current collector is formed of one or more of copper (Cu), chromium (Cr) and conductive carbon (C), and the current collector is platinum (Pt), metal nitride A _x B _y N (A: Cr, Al , B: Cr, Al, C) and the surface is coated with a material containing at least one of the metal carbide A _x C (A: Cr, Ti, Al), The current collector seals the reaction gas flow path of the outermost separator plate body, thereby preventing galvanic corrosion by the cooling water circulated to the second flow path part of the current collector. delete The method of claim 1, The current collector includes a gasket of a shape corresponding to the gasket formed in the outermost separator plate body. delete delete delete delete delete

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