KR101430286B1 - Manufacturing Method of Bipolar plate for fuel cell - Google Patents

Abstract

The present invention relates to a bipolar plate formed on both sides of a membrane / electrode assembly for supplying hydrogen and oxygen gas to electrodes of a membrane / electrode assembly, comprising: a plurality of unit plates made of a conductive material; A separating member of a nonconductive material for electrically separating between the unit plates; And a flow channel formed in communication with the unit plate and the separating member disposed on the same plane to supply and discharge the gas, and a stack structure using the bipolar plate.
According to the present invention, the manufacturing cost and time of the fuel cell stack can be drastically reduced, and the power conversion efficiency can be improved by fabricating the high voltage stack with a small number of stacked cells.

Description

Technical Field [0001] The present invention relates to a bipolar plate for a fuel cell,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bipolar plate of a fuel cell, a stack structure using the bipolar plate, and a manufacturing method thereof. More particularly, the present invention relates to a bipolar plate A plurality of unit plates of a conductive material are separated on the same plane by a separating member made of a nonconductive material so that the manufacturing cost and time of the fuel cell stack can be drastically reduced, To a bipolar plate of a fuel cell, a stack structure using the bipolar plate, and a method of manufacturing the same.

Petroleum energy, which is significantly reduced in production compared to demand, not only causes serious natural environmental problems, but also has a limited reserves. Recently, research on alternative energy has been actively conducted. Among them, fuel cells using hydrogen energy are not only high in thermal efficiency as compared with the current internal combustion engine, but also clean the products, and are being regarded as environment-friendly alternative energy.

The fuel cell is a power generation system that converts chemical energy directly into electrical energy without the combustion process by the electrochemical reaction that takes place when the fuel gas, hydrogen and oxygen (or air) react with each other. Unlike batteries, it is a high efficiency clean energy conversion device that continuously supplies electricity by supplying hydrogen and oxygen from the outside.

As described above, the final product of the fuel cell that generates electricity using hydrogen and oxygen supplied from the outside is a clean high-efficiency power generation system in which the discharge of noxious gases such as NOx and SOx is 1% or less as water, heat and direct current It is not only able to reduce environmental pollution considerably, but also has been extensively studied for practical use as a next generation energy source because it is very high, more than 50%, compared with existing internal combustion engines having an efficiency of less than 25%.

The fuel cell, which is a highly efficient clean power generation system, may be a phosphoric acid type that operates at about 150 to 200 DEG C, a polymer electrolyte type or alkaline type that operates at a temperature ranging from room temperature to 100 DEG C, And a solid oxide fuel cell that operates at a high temperature of about 1000 ° C. Each fuel cell basically operates on the same principle, but the type of fuel, the operating temperature, the catalyst and the electrolyte As described above.

In particular, the polymer electrolyte membrane fuel cell (PEMFC) among various kinds of fuel cells as described above uses a solid polymer as an electrolyte, so that it is easy to manage the electrolyte, and corrosion due to electrolyte and evaporation of the electrolyte It has a high current density per unit area and a high output characteristic compared with other fuel cells. At the same time, it has a low operating temperature and is easy to maintain and repair, and has a quick start and response characteristic. , A distributed power source for houses and public buildings, and a small power source for an electronic device.

The PEMFC typically includes a stack, a reformer, a fuel tank, and a fuel pump for constituting the system. The stack forms the body of the fuel cell, and the fuel pump supplies the fuel in the fuel tank to the reformer. The reformer reforms the fuel to generate hydrogen gas and supplies the hydrogen gas to the stack. Accordingly, the polymer electrolyte fuel cell supplies fuel in a fuel tank to a reformer by operating a fuel pump, reforms the fuel in the reformer, generates hydrogen gas, electrochemically reacts the hydrogen gas and oxygen in the stack, And generates energy.

In the above-described polymer electrolyte fuel cell, the stack which substantially generates electricity includes several to dozens of unit cells made of a membrane / electrode assembly (MEA) and a bipolar plate closely attached to both sides of the membrane / electrode assembly And has a laminated structure. The membrane / electrode assembly has a structure in which an anode electrode and a cathode electrode are attached with a polymer electrolyte membrane interposed therebetween.

The bipolar plate functions as a path for separating the membrane / electrode assembly and supplying hydrogen gas and oxygen required for the reaction of the fuel cell to the anode and cathode electrodes of the membrane / electrode assembly, And also acts as a conductor for connecting the anode electrode and the cathode electrode in series.

On the other hand, in the conventional fuel cell, one membrane / electrode assembly is inserted between two bipolar plates to form one cell. Since a voltage of about 1 V is generated in one cell, the system operates in a desired voltage range It is necessary to stack a plurality of cells to form a stack.

On the other hand, in order to reduce the manufacturing cost of the fuel cell stack, it is necessary to reduce the number of cells stacked on the stack and to manufacture the bipolar plate and the membrane / electrode assembly in a large area.

However, when the number of cells is reduced by fabricating a large-area bipolar plate, the cell area increases and the number of cells decreases, resulting in a low voltage / high current stack. In the case of a low voltage / high current stack, the efficiency of the PCS There is a problem.

In addition, in the case of low voltage / high current, the efficiency of the PCS is decreased and the price is increased. Also, there is a limit to the development of a large area due to the minimum voltage limit of the stack due to the conversion efficiency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bipolar plate of a fuel cell and a stack structure using the bipolar plate, which can reduce the manufacturing cost and time of the fuel cell stack by reducing the number of stacked cells. We will do it.

Another object of the present invention is to improve power conversion efficiency by fabricating a high voltage stack with a small number of stacked cells.

As a means for solving the above problems, the bipolar plate of the fuel cell according to the present invention is a bipolar plate formed on both sides of a membrane / electrode assembly and supplying hydrogen and oxygen gas to the electrodes of the membrane / A plurality of unit plates made of a conductive material; A separating member of a nonconductive material for electrically separating between the unit plates; And a flow channel formed in communication with each of the unit plates and the separating member disposed on the same plane to supply and discharge the gas.

The separating member is preferably made of a polymer material.

Further, the unit plate and the separating member are preferably integrally formed.

That is, a powder of a conductive material for forming the unit plate and a powder of a nonconductive material for forming the separating member are separately injected into the mold using a fine powder feeder, .

Alternatively, a conductive material for forming the unit plate and a nonconductive material for forming the separating member may be provisionally molded through a drying process, followed by pressing in a state of being injected into a mold.

A method in which a conductive material for forming the unit plate is first injected into a mold and a nonconductive material for forming the separating member is secondarily injected into a space formed by movement of the mold core and then the mold is pressed May be configured to be manufactured.

Here, the nonconductive material for forming the separating member may be made of a polymer resin and an additive for improving the flow property and thermal expansion coefficient, and the conductive material for forming the unit plate may be conductive It is preferable that the carbon material is composed of a mixed component.

The stack structure of the fuel cell according to the present invention comprises: a membrane / electrode assembly body having an anode electrode and a cathode electrode sandwiched between electrolyte membranes; And a bipolar plate formed on both sides of the membrane / electrode assembly and supplying hydrogen and oxygen gas to the electrodes of the membrane / electrode assembly,

The bipolar plate may include a plurality of unit plates made of a conductive material; A separating member of a nonconductive material for electrically separating between the unit plates; And a flow channel formed in communication with each of the unit plates and the separating member disposed on the same plane to supply and discharge the gas.

The stack structure of the fuel cell according to the present invention is a fuel cell stack structure comprising a membrane / electrode assembly having an anode and a cathode attached to each other with an electrolyte membrane sandwiched therebetween, and a bipolar plate supplying hydrogen and oxygen gas to the membrane / electrode assembly, Respectively,

The bipolar plate may include a plurality of unit plates made of a conductive material; A separating member of a nonconductive material for electrically separating between the unit plates; And a flow channel formed in communication with each of the unit plates and the separating member disposed on the same plane to supply and discharge the gas.

The bipolar plate of the fuel cell according to the present invention and the stack structure using the bipolar plate according to the present invention can remarkably reduce the manufacturing cost and time of the fuel cell stack and improve the power conversion efficiency by fabricating a high voltage stack with a small number of stacked cells .

1 is a perspective view showing a structure of a bipolar plate of a fuel cell according to the present invention;
2 is a perspective view showing a structure in which a bipolar plate of a fuel cell according to the present invention is stacked.
3 to 5 are schematic views showing a method of manufacturing a bipolar plate of a fuel cell according to the present invention.
6 and 7 are perspective views showing a stack structure of a fuel cell according to the present invention.

Hereinafter, preferred embodiments of a bipolar plate and a stack structure using the bipolar plate according to the present invention will be described with reference to the accompanying drawings.

The fuel cell stack according to the present invention has a structure in which a membrane / electrode assembly and a bipolar plate closely contacting both surfaces of the membrane / electrode assembly are continuously stacked. Here, the membrane / electrode assembly has a structure in which an anode electrode and a cathode electrode are attached to each other with a polymer electrolyte membrane interposed therebetween.

The bipolar plate serves to separate each of the membrane / electrode assemblies and serve as a passage for supplying hydrogen and oxygen gas necessary for the reaction of the fuel cell to the anode and cathode electrodes of the membrane / electrode assembly, The anode and the cathode are connected to each other in series.

Therefore, hydrogen gas is supplied to the anode electrode through the bipolar plate, while oxygen is supplied to the cathode electrode. In this process, an oxidation reaction of hydrogen gas occurs at the anode electrode, a reduction reaction of oxygen occurs at the cathode electrode, electricity is generated due to the movement of generated electrons, and heat and moisture are generated incidentally.

As described above, the bipolar plate of the fuel cell is formed of a conductive material that can flow electricity because a channel channel for supplying fuel and air is formed and also serves as a movement path for electrons generated in the electrode.

For example, a baffle plate may be formed by forming a flow channel through a machining process on a substrate made of a conductive material such as a graphite plate or a metal plate, or by molding a graphite composite material or a metal plate as a conductor by using a forming mold having a flow channel do.

In addition, the bipolar plate according to the present invention may be manufactured using a conductive metal material such as stainless steel, aluminum, titanium, or copper.

FIG. 1 shows a bipolar plate structure of a fuel cell according to the present invention, and FIG. 2 shows a stacked structure of the bipolar plate.

1 and 2, a bipolar plate 10 of a fuel cell according to the present invention includes a plurality of unit plates 12 made of a conductive material, a plurality of unit plates 12 electrically connected to each unit plate 12, And a channel channel (not shown) communicating with the unit plate 12 and the separating member 14 disposed on the same plane to supply and discharge the gas, .

The plurality of unit plates 12 are disposed on the same plane and electrically separated from each other, but have a structure in which the channel channels communicate with each other. That is, the bipolar plate 10 according to the present invention shares a channel channel for gas movement on the same plane as a general bipolar plate, but is divided into a plurality of unit plates 12 that are electrically separated from a general bipolar plate .

Each of the unit plates 12 separates the membrane / electrode assembly 20 and supplies hydrogen and oxygen gas necessary for the reaction of the fuel cell to the electrodes of the membrane / electrode assembly 20 in the same manner as a conventional general bipolar plate And the electrodes of the membrane / electrode assemblies 20 are connected to each other in series. For this purpose, each of the unit plates 12 is made of a graphite material or a metal plate component of a conductive material.

Meanwhile, each unit plate 12 according to the present invention performs the same operation as a conventional general bipolar plate. Therefore, when the four unit plates 12 are disposed on the same plane by the separating member 14 made of a nonconductive material, the same effect as that of forming four fuel cell unit cells in parallel can be obtained.

The separating member 14 is made of a nonconductive material as an element for electrically separating the unit plate 12 on the same plane, and may be made of a nonconductive polymer material, for example. A channel channel communicating with the adjacent unit plate 12 is formed in the separating member 14.

Therefore, the unit plates 12 are separated from each other by the separating member 14 and are electrically separated from each other. However, the channel channels for supplying and discharging the gas are separated from the unit plate 12 and the separating member 14). Since the separating member 14 for electrically separating the unit plate 12 is electrically insulated, the separating member 14 may be connected to each other.

For example, as shown in Figs. 1 and 2, the bipolar plate 10 according to the present invention has a cross-shaped separating member 14 on the same plane, Wherein the unit plates 12 are separated from each other electrically and the flow channel is communicated with the unit plates 12 and the separating member 14, .

On the other hand, in the conventional fuel cell stack, one membrane / electrode assembly is inserted between two bipolar plates to form one cell, and since a voltage of about 1 V is generated in one cell, In order to operate, a plurality of cells must be stacked to fabricate a stack, resulting in an increase in manufacturing cost and inefficiency of space utilization.

However, according to the present invention, it is possible to obtain a fuel cell with a higher voltage than conventional ones even with a small number of stacked cells. For example, when the fuel cell is manufactured using the bipolar plate 10 divided into four unit plates 12 as shown in FIG. 1, a voltage four times as high as the conventional cell stack can be obtained.

Therefore, when the fuel cell stack is constructed using the bipolar plate 10 composed of a plurality of unit plates 12 on the same plane as in the present invention, the manufacturing cost of the fuel cell stack is reduced and the number of stacked cells is reduced Therefore, it is possible to realize a high voltage stack, so that the efficiency of the PCS (power converter) can be increased.

Meanwhile, the bipolar plate 10 according to the present invention is preferably configured such that the unit plate 12 and the separating member 14 are integrally formed.

3 to 5 schematically show a method of manufacturing a bipolar plate of a fuel cell according to the present invention.

Referring to FIG. 3, the bipolar plate manufacturing method according to the first embodiment of the present invention divides the powder of the unit plate 12 and the separating member 14 into molds 30 by using a fine- Followed by compression.

More specifically, a powder of a conductive material for forming the unit plate 12 and a powder of a nonconductive material for forming the separating member 14 are molded using a fine powder supply device (not shown) 30). That is, the powder of the conductive material and the powder of the nonconductive material are separately injected into the mold 30 so as not to be mixed with each other. Thereafter, when the powder in the mold 30 is compressed in the thermal atmosphere of the furnace, the interfaces of the powders are fused to each other by heat to form the bipolar plate 10 composed of the unit plate 12 and the separating member 14 .

Referring to FIG. 4, the bipolar plate manufacturing method according to the second embodiment of the present invention is a method of manufacturing a bipolar plate by molding a unit plate 12 and a separating member material 14 in a mold 40 .

More specifically, after the conductive material for forming the unit plate 12 and the nonconductive material for forming the separating member 14 are dried, the solvent is evaporated and the conductive material and the viscous A pseudomorphic process is performed in which the conductive material is temporarily bonded. Thereafter, the bipolar plate according to the present invention is formed by pressing the material of the hypothetical bipolar plate 10 in a state of being injected into the mold 40.

5, the bipolar plate manufacturing method according to the third embodiment of the present invention is manufactured by sequentially injecting the unit plate 12 and the separating member 14 to the mold 50, followed by pressing .

More specifically, the conductive material for forming the unit plate 12 is first injected into the mold 50. At this time, the core 56 is positioned at the center portion, so that the conductive material is not filled. The bipolar plate according to the present invention is formed by secondarily injecting a nonconductive material for forming the separating member 14 in a hollow space formed by moving the core 56 backward and then pressing the mold 50 do.

Since the conductive material generally has a significantly lower fluidity than the nonconductive material, the conductive material having low fluidity is primarily injected into the mold 50 through the first injection cylinder 52 first. Thereafter, the nonconductive material having high fluidity is secondarily injected through the second injection cylinder 54 into the empty space in the center portion formed by moving the core 56 of the mold.

The conductive material is a mixture of a conductive carbon material (carbon black, graphite, CNT, etc.) with a nonconductive material, and a polymer resin such as a nonconductive material may be mixed with an adhesive. As the nonconductive material, only the polymer resin may be used. However, in order to improve the flowability and the thermal expansion coefficient, additives such as a lubricant or silica may be mixed and used.

Next, a structure of a fuel cell stack manufactured using the bipolar plate constructed as above will be described.

6 and 7 show the stack structure of the fuel cell according to the present invention, respectively.

Referring to FIG. 6, the fuel cell stack structure according to the first embodiment of the present invention includes a unit cell structure including a membrane / electrode assembly 20 and a pair of bipolar plates 10.

Here, the membrane / electrode assembly 20 has a conventional structure in which an anode electrode and a cathode electrode are attached to each other with an electrolyte membrane interposed therebetween.

The bipolar plate 10 is formed on both surfaces of the membrane / electrode assembly 20 and supplies hydrogen and oxygen gas to the electrodes of the membrane / electrode assembly 20, so that the bipolar plate 10 is made of a conductive material A plurality of unit plates 12 and a separating member 14 for electrically separating the unit plates 12 from each other and a unit plate 12 and a separating member 14 disposed on the same plane, And a channel channel through which gas is supplied and discharged.

7, the fuel cell stack structure according to the second embodiment of the present invention has a structure in which the membrane / electrode assembly 20 and the bipolar plate 10 are stacked alternately with each other, that is, Stacked structure.

Here, the membrane / electrode assembly 20 has a conventional structure in which an anode electrode and a cathode electrode are attached to each other with an electrolyte membrane interposed therebetween.

The bipolar plate 10 is formed on both surfaces of the membrane / electrode assembly 20 and supplies hydrogen and oxygen gas to the electrodes of the membrane / electrode assembly 20, so that the bipolar plate 10 is made of a conductive material A plurality of unit plates 12 and a separating member 14 for electrically separating the unit plates 12 from each other and a unit plate 12 and a separating member 14 disposed on the same plane, And a channel channel through which gas is supplied and discharged.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

10: bipolar plate 12: unit plate
14: separating member 20: membrane / electrode assembly

Claims (9)

A membrane electrode assembly (MEMS) is formed on both sides of the membrane electrode assembly to supply hydrogen and oxygen gas to the electrodes of the membrane / electrode assembly,
A plurality of unit plates made of a conductive material; And a separation member for electrically separating the unit plates from each other, wherein the plurality of unit plates share one manifold and a flow path is connected, all the conduction parts share one manifold, Wherein the bipolar plate includes a plurality of bipolar plates,
Dividing and injecting a powder of a conductive material for forming the unit plate and a powder of a nonconductive material for forming the separating member in a mold; And
The process of forming the bipolar plate comprising the unit plate and the separating member while compressing the powder in the mold in a thermal atmosphere of the furnace and fusing the interfaces of the powders to each other by heat
Wherein the bipolar plate is made of a metal.
A membrane electrode assembly (MEMS) is formed on both sides of the membrane electrode assembly to supply hydrogen and oxygen gas to the electrodes of the membrane / electrode assembly,
A plurality of unit plates made of a conductive material; And a separating member for electrically separating between each unit plate,
A method of manufacturing a bipolar plate in which all conduction parts share a manifold and flow paths are all connected,
A step of provisionally shaping the unit plate and the separating member material; And
A process of pressing the provisionally molded material while injecting the material into a mold
Wherein the bipolar plate is made of a metal.
delete delete 3. The method of claim 2,
In the step of shaping, after the conductive material for forming the unit plate and the nonconductive material for forming the separating member are dried, the conductive material and the nonconductive material are temporarily Wherein the bipolar plate is formed by a pseudomorphic process.
A membrane electrode assembly (MEMS) is formed on both sides of the membrane electrode assembly to supply hydrogen and oxygen gas to the electrodes of the membrane / electrode assembly,
A plurality of unit plates made of a conductive material; And a separating member for electrically separating the unit plates from each other, wherein all of the conducting portions share one manifold and the flow paths are all connected,
A first step of injecting a conductive material for forming the unit plate into a mold having a core at a center thereof;
Conducting a secondary injection of a nonconductive material to form the separating member in a hollow space formed by moving the core backward; And
The process of pressing the mold
Wherein the bipolar plate is made of a metal.
The method according to any one of claims 1, 2, 5, and 6,
Wherein the nonconductive material comprises a polymer resin and an additive for improving the flowability and thermal expansion coefficient,
Wherein the conductive material comprises a component in which the conductive carbon material is mixed with the nonconductive material.
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