KR20130128493A - Carbon fabric bipolar plate of fuel cell and method for manufacturing the same - Google Patents

Abstract

Disclosed are a carbon fabric bipolar plate for a fuel cell and a manufacturing method thereof for manufacturing a bipolar plate by using carbon fabric. The bipolar plate according to the present invention comprises two or more stacked sheets of carbon fabric composed of carbon fibers; and a polymer matrix applied among the two or more sheets of carbon fabric to expose carbon fibers on the surface of the two or more sheets of carbon fabric. The manufacturing method according to the present invention comprises the steps of: molding the carbon fabric into a preliminary mold for the bipolar plate by consolidating the carbon fabric including the polymer matrix with hot pressing; and trimming the preliminary mold for the bipolar plate into the bipolar plate. Also the polymer matrix can be impregnated into the carbon fabric by resin spray or resin transfer molding. A thin metal plate can be temporarily attached to one surface of the carbon fabric or conductive powder can be mixed with the polymer matrix to increase electric conductivity. The surplus of the polymer matrix on the preliminary mold for the bipolar plate is carbonized with flame or plasma. According to the present invention, power density can be improved by increasing the number of unit cells in the process of lightening the bipolar plate and by increasing a reaction area. Also the efficiency of the bipolar plate can be improved because the contact resistance of the bipolar plate is decreased and current loss is reduced in the stack of a fuel cell.

Description

Carbon Fiber Fabric Separator for Fuel Cell and Manufacturing Method Thereof {CARBON FABRIC BIPOLAR PLATE OF FUEL CELL AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a fuel cell, and more particularly, to a carbon fiber fabric separator for a fuel cell for producing a separator of the fuel cell by a carbon fiber fabric and a method of manufacturing the same.

A fuel cell is an energy converter that directly converts chemical energy generated by oxidation of fuel into electrical energy. Fuel cells have been developed in various forms and structures depending on the type of fuel used in the cell. Polymer Electrolyte Membrane Fuel Cell (PEMFC) uses a polymer membrane with hydrogen ion exchange as an electrolyte. These PEMFCs have high efficiency, high current density and power density, short start-up time, and fast response to load changes. Attempts are being made actively.

PEMFCs are disclosed in the patent documents of US Pat. Nos. 7,862,922 and 7,901,836. The stack of a PEMFC disclosed in these patent documents basically consists of a plurality of unit cells / Single cells and two end plates.

PEMFC consists of anode, cathode, polymer electrolyte membrane, two gas diffusion layers (GDL), a plurality of gaskets and two separators have. The polymer electrolyte membrane acts as a carrier of hydrogen ions between the anode and the cathode, and also serves to prevent contact between oxygen and hydrogen. A membrane-electrode assembly (MEA) in which two electrodes, an anode and a cathode, are bonded to a polymer electrolyte membrane by hot-pressing, is called a membrane-electrode assembly (MEA).

The separator is an electrically conductive plate disposed on both sides of the membrane-electrode assembly and also referred to as a bipolar plate or a flow field plate. An anode side channel is formed on one side of the separator plate, and a cathode side channel is formed on the other side. Endplates are usually bolted using tie rods to reduce contact resistance between components and have connectors for outlet, inlet, coolant circulation, and power output of the reactor. .

On the other hand, in the anode of the PEMFC, hydrogen cations (Proton) and electrons (Electron) are generated by the oxidation reaction of hydrogen. The generated hydrogen cations and electrons move to the cathode through the electrolyte membrane and the separator, respectively. In the cathode, water, that is, water is generated by hydrogen cations and oxygen reduction reactions of electrons and oxygen, and electric power is generated from the flow of electrons.

The separator should have low electrical resistance, high chemical resistance and mechanical properties, and low gas permeability to prevent leakage of hydrogen and oxygen. In addition, the electrical contact resistance between two adjacent separation plates should be low. The material of the separator is composed of graphite, expanded carbon, stainless steel, or a polymer matrix composite in which carbon particles and graphite particles are added to a polymer matrix. Is being used.

In the polymer electrolyte fuel cell as described above, the graphite separator has a low contact resistance and high electrical conductivity, but a thin graphite plate must be formed by machining such as milling, which is expensive in manufacturing, low productivity, and impact. There is a big problem of the possibility of breakage. The expanded carbon separator and the polymer matrix composite are difficult to form fine channels for fluid flow, and have low electrical conductivity compared to graphite. The stainless steel separator has a high productivity, but has a disadvantage of high contact resistance and corrosion. The polymer matrix composite plate has excellent chemical resistance and lower contact resistance than the stainless steel separator, but has a high electrical resistance.

Republic of Korea Patent No. 10-0783867 "Separation plate for fuel cells and a method of manufacturing the same" is a composite consisting of 75 ~ 85% by weight graphite of 10 ~ 200㎛ particle size, 13.5 ~ 22.5% by weight phenolic resin, 1.5 ~ 2.5% by weight hardener The material is prepared, mixed, dispersed in a mold, molded into a separator, and heat treated at 100 to 120 ° C. to prepare a separator. However, the Republic of Korea Patent No. 10-0783867 has a problem that the process of compressing the powder (Power) into the mold is difficult, the moldability is lowered, and the heat treatment process takes a long time, the productivity is lowered.

Japanese Patent Laid-Open No. 1999-297338 "Separation Plate for Solid Polymer Fuel Cell and Manufacturing Method Thereof" manufactures a separation plate using carbon / graphite powder and a polymer matrix. Japanese Patent Laid-Open No. 1999-297338 has a problem in that the process of loading and compressing powder into a mold is difficult, and thus moldability is lowered, and the heat treatment process takes a long time, resulting in a decrease in productivity.

Japanese Patent Laid-Open No. 2001-325967 "Fuel Cell Separator and Manufacturing Method Thereof, Fuel Cell Separator and Solid Polymer Fuel Cell" includes a separator plate using a conductor powder having a particle diameter of 60 to 100 µm, a matrix, and a volatile solvent. To manufacture. Japanese Laid-Open Patent Publication No. 2001-325967 has a disadvantage in that the mechanical properties are lowered and the moldability is lowered when the particle content is increased in order to increase the contact between the particles to improve the electric conductivity. In addition, the use of the volatile solvent has a long process time, there is a disadvantage that the work safety and environmental problems are likely to cause.

The present invention is to solve various problems of the prior art as described above. It is an object of the present invention to provide a novel fuel cell carbon fiber fabric separator for producing a fuel cell separator from a carbon fiber fabric composite material and a method of manufacturing the same.

Another object of the present invention is to provide a carbon fiber fabric separator for fuel cells and a method of manufacturing the same, which can improve power density by increasing the number of unit cells and increasing the reaction area by reducing the weight.

It is still another object of the present invention to provide a carbon fiber fabric separator for fuel cells and a method of manufacturing the same, which can improve efficiency by reducing current loss in a stack of fuel cells by reducing contact resistance.

Still another object of the present invention is to improve the sealing property (excellent bending strength, compressive strength and corrosion resistance) due to the fastening load, easy handling (Handling), effectively prevent the damage caused by the load It is to provide a carbon fiber fabric separator for a fuel cell and a method of manufacturing the same.

It is still another object of the present invention to provide a carbon fiber fabric separator for fuel cells and a method of manufacturing the same, which can improve the characteristics of cold start due to small thermal inertia and improve productivity by a continuous process. will be.

According to one aspect of the invention, there is provided a carbon fiber fabric separator for a fuel cell and a method of manufacturing the same. A carbon fiber fabric separator for fuel cells and a method for manufacturing the same according to the present invention include the steps of: molding a carbon fiber fabric containing a polymer matrix by consolidation by hot pressing into a separator preform; Trimming the separator preform with the separator.

In addition, the polymer matrix can be impregnated into the carbon fiber fabric by resin spraying or Resin transfer molding (RTM). The conductive powder may be mixed to temporarily bond a metal thin plate to one side of the carbon fiber fabric or to increase the electrical conductivity to the polymer matrix. The surplus polymer matrix on the surface of the separator preform is carbonized by flame or plasma.

According to another aspect of the present invention, there is provided a carbon fiber fabric separator for fuel cells, comprising at least two carbon fiber fabrics made of carbon fibers and stacked; And a polymeric matrix applied between the at least two carbon fiber fabrics to expose the carbon fiber to the surface of the at least two carbon fiber fabrics.

The carbon fiber fabric separator for fuel cells and the method for manufacturing the same according to the present invention can increase power density by increasing the number of unit cells by increasing the number of unit cells by reducing the weight of the separator. In addition, the contact resistance of the separator may be reduced, thereby reducing current loss in the stack of the fuel cell, thereby improving efficiency. In addition, it is excellent in flexural strength, compressive strength and corrosion resistance due to the fastening load of the separator, which can improve the sealing property, ease of handling, effectively prevent the damage caused by the load, and the thermal inertia of the separator. Since it is small, the characteristic of cold start can be improved. Since a series of processes such as cutting carbon fiber fabrics, impregnating polymer resins, hot pressing, and trimming can be performed continuously, productivity can be improved and production costs can be reduced.

1 is a process chart shown to explain a method for manufacturing a carbon fiber fabric separator for a fuel cell according to the present invention.
Figure 2 is a perspective view showing an example of a carbon fiber fabric composite material for the production of a carbon fiber fabric separator for fuel cells according to the present invention.
3 is a cross-sectional view showing another example of a carbon fiber fabric composite material for the production of a carbon fiber fabric separator for fuel cells according to the present invention.
Figure 4 is a cross-sectional view of the mold assembly shown to explain the resin transfer molding in the method of manufacturing a carbon fiber fabric separator for fuel cells according to the present invention.
5 is a cross-sectional view of a mold assembly for explaining a process of applying a non-metal conductive powder in the method of manufacturing a carbon fiber fabric separator for fuel cells according to the present invention.
6 is a cross-sectional view of a mold assembly for explaining a process for providing a non-metal conductive thin film in the method of manufacturing a carbon fiber fabric separator for fuel cells according to the present invention.
Figure 7 is a process chart for explaining the surface treatment of the separator preform in the manufacturing method of the carbon fiber fabric separator for fuel cells according to the present invention.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments with reference to the accompanying drawings.

Hereinafter, preferred embodiments of a carbon fiber fabric separator for a fuel cell and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to Figure 1, the separator according to the present invention hot-press carbon fiber fabric composite material consisting of a carbon fiber fabric 10, and a polymer base 20 is applied to one side of the carbon fiber fabric (10) It is molded by (Hot press) method.

Carbon fiber fabric 10 is used in various forms. The carbon fiber fabric 10 may be woven into plain weave, twill weave, or hand weave by carbon fiber having a diameter of about 7 μm. In addition, the carbon fiber fabric 10 may be configured in the form of a fabric in which one-way carbon fibers are cross-laminated 0 to 90 degrees, or in the form of a fabric in which carbon fibers of 1 mm or more in length are randomly arranged. The carbon fiber fabric 10 may be formed by temporarily joining two sheets with a polymer matrix, for example, a phenol resin, an epoxy resin, a polyester resin, or the like.

As shown in FIG. 2, as an example of the carbon fiber fabric composite material 30, the carbon fiber fabric 20 is woven into plain weave. The polymer matrix 20 is impregnated on one surface of the carbon fiber fabric 10. Such a carbon fiber fabric composite material 30 can increase the number of unit cells by reducing the weight of the separator plate to increase the reaction area, it is possible to improve the power density. In addition, the contact resistance of the separator may be reduced, thereby reducing current loss in the stack of the fuel cell, thereby improving efficiency. In addition, the flexural strength, the compressive strength and the corrosion resistance due to the fastening load of the separator plate can be improved to improve the sealing characteristics, easy handling, and can effectively prevent damage due to the load. Since the thermal inertia of the separator is small, it is possible to improve the characteristics of cold start.

On the other hand, in order to increase the electrical conductivity of the carbon fiber fabric composite material 30, the non-metal conductive powder 40 is further mixed in the polymer base (20). The nonmetal conductive powder 40 may be composed of carbon black, carbon powder, carbon nanotube, graphite powder, carbon carbon fiber, or the like. .

Referring to FIG. 3, the carbon fiber fabric composite material 30 has a metal thin plate 50 interposed therebetween so as to lower gas permeability between two carbon fiber fabrics 10 stacked thereon. The carbon fiber fabrics 10 are temporarily bonded to both sides of the metal thin plate 50 by the polymer matrix 20. The metal thin plate 50 is made of aluminum, stainless steel, copper, or the like. On the other hand, when the two carbon fiber fabrics 10 are temporarily bonded to both sides of the metal thin plate 50, after the production of the separator plate carbon fiber that is not impregnated with the polymer base is exposed to the outside to reduce the electrical contact resistance do. In this embodiment, the number of carbon fiber fabrics 10 to be laminated may be increased as needed.

As shown in Figure 1 (a), the carbon fiber fabric 10 is made in the form of a roll (Roll) having a continuous length. Roll-shaped carbon fiber fabric 10 is mounted to the supply reel (Supply reel: 100) to be released. The roll feed 110 is composed of a cutting roller 112 and an idle roller 114. A cutter 116 is mounted on the outer circumferential surface of the cutting roller 112. The tip of the carbon fiber fabric 10 is interposed between the cutting roller 112 and the idle roller 114, the supply reel (Rolling friction) of the rotating cutting roller 112 and the idle roller 114 (rolling friction) It is conveyed as it is released from 100). The cutter 116 cuts the carbon fiber fabric 10 to the length required for the manufacture of the separator plate every revolution of the cutting roller 112. In this embodiment, the carbon fiber fabric 10 can be cut to the required length by a separate cutter or cutter.

As shown in FIG. 1B, the hot press machine 120 includes a table 122, a ram 124 and a mold assembly 130. The mold assembly 130 is composed of an upper mold 132 and a lower mold 134. The upper mold 132 is mounted on the lower surface of the ram 124, and the lower mold 134 is mounted on the upper surface of the table 124. Each of the upper mold 132 and the lower mold 134 has cavities 132a and 134a for forming the carbon fiber fabric 10 as a separator. Channel patterns 132b and 134b are formed in the cavities 132a and 134a to form channels for the flow of fuel, water and air.

The worker charges the carbon fiber fabric 10 into the cavity 134a of the lower mold 134. The polymer base 20 is impregnated into the carbon fiber fabric 10 by resin spraying of the injection hole 140. By impregnating the polymer matrix 20 into the carbon fiber fabric 10 by the resin injection of the polymer matrix 20, the time required for the process can be shortened to improve productivity. In this embodiment, the carbon fiber fabric 10 in which the polymer matrix 20 is impregnated may be made of prepreg. The prepreg is made of a laminate or sheet after carbon fiber is impregnated into the polymer matrix and then cured into a B-stage.

As shown in FIG. 1C, after the impregnation of the polymer matrix 20 is completed, the carbon fiber fabric 10 is consolidated and cured by the operation of the hot press machine 120 to preform the separator. Molded by (60). Consolidation of the carbon fiber fabric 10 is the upper mold 132 and the lower mold 134 by the pressing of the upper mold 132 by the lowering of the ram 124 or by the lowering of the ram 124 and the raising of the table 122. By simultaneous pressurization). The molding temperature of the hot press machine 120 is controlled in accordance with the curing temperature of the polymer matrix 20. When the consolidation and curing of the carbon fiber fabric 10 is completed, the operator opens the upper mold 132 and the lower mold 134 to take out the separator preform 60.

On the other hand, the curing of the polymer matrix 20, for example, a thermosetting resin raises the ambient temperature to about 80 ~ 400 ℃ to impart thermal energy, so that the monomer-type resin cross-linking or non- The resin of the stage is melted once and then changed from a liquid to a solid by a crosslinking reaction. Curing of the thermoplastic resin is achieved by melting the resin completely by applying heat energy and filling it at the interface of the carbon fiber fabric, and when the temperature is lowered, it is converted into a solid again.

As shown in FIG. 1 (d), the separator preform 60 is trimmed to form a separator 70. The trimming machine 150 is composed of a table 152, a ram 154 and a trimming mold assembly 160. Trimming mold assembly 160 is composed of an upper mold 162 and a lower mold (164). The lower mold 164 has a cavity 164a formed for trimming the separator preform 60. The upper mold 162 is mounted on the lower surface of the ram 154, and is lifted by the operation of the ram 154. The lower mold 164 is mounted on the upper surface of the table 152. The lower mold 164 may be elevated by the operation of the table 152.

The operator loads the separator preform 60 into the cavity 164a of the lower mold 164, and then molds the upper mold 162 and the lower mold 164 to close the separator preform 60. Punching (punching), cutting and the like to produce a separator (70). The worker mold-opens the upper mold 162 and the lower mold 164, and then removes the separating plate 70 from the cavity 164a of the lower mold 164.

As shown in FIG. 4, the impregnation of the polymer base 20 molds the upper mold 162 and the lower mold 164 and then the polymer matrix through the injection hole 170 connected to the upper mold 162. It can be performed by resin transfer molding which injects and injects (20). By impregnating the polymer matrix 20 into the carbon fiber fabric 10 by the resin transfer molding, it is possible to shorten the time required for the process to improve productivity.

Referring to FIG. 5, the non-metal conductive powder 80 is further applied to the inner surfaces of the cavities 132a and 134a in the opened state of the upper mold 132 and the lower mold 134 before hot pressing. The non-metal conductive powder 80 is sprayed through the nozzle 182 to the injection hole 180 and applied to the inner surfaces of the cavities 132a and 134a. The non-metal conductive powder 80 may be composed of carbon black, carbon powder, carbon nanotube, graphite powder, chopped carbon fiber, and the like. . The non-metal conductive powder 80 acts as a release agent to allow the separator 70 to be easily separated when taken out from the cavities 132a and 134a.

Referring to FIG. 6, a non-metal conductive thin film 90 is further provided as a release agent on the inner surfaces of the cavities 132a and 134a in the opened state of the upper mold 132 and the lower mold 134 before hot pressing. The non-metal conductive thin film 90 may be made of graphite foil, carbon paper, graphite felt, carbon felt, or the like. By the non-metal conductive thin film 90, the separator 70 may be easily separated from the cavities 132a and 134a and taken out.

Referring to FIG. 7, the method of manufacturing the separator according to the present invention further performs a surface treatment for carbonizing the surface of the separator preform 60 to increase the contact resistance of the separator 70. The surface treatment of the separator preform 60 carbonizes the excess polymer matrix 20 from the surface of the separator preform 60 by hot flame treatment 190 or high temperature plasma. In the surface treatment of the separator preform 60, the polymer matrix is composed of a thermosetting resin such as a phenol resin, an epoxy resin, a vinyl ester, and a polyester. Flame 190 may be emitted to the surface of the separator preform 60 by a torch lamp (192). The plasma may be generated by a plasma generator and radiated to the surface of the separator preform 60.

The embodiments described above are merely illustrative of the preferred embodiments of the present invention, the scope of the present invention is not limited to the described embodiments, those skilled in the art within the spirit and claims of the present invention It will be understood that various changes, modifications, or substitutions may be made thereto, and such embodiments are to be understood as being within the scope of the present invention.

10: carbon fiber fabric 20: polymer base
30: carbon fiber fabric composite 40, 80: nonmetal conductive powder
50: metal thin plate 60: separator plate preform
70: separator 100: supply reel
110: roll feed 116: cutter
120: hot pressing machine 130: mold assembly
132: upper mold 134: lower mold
140, 170: inlet 150: trimming machine
160: trimming mold assembly 162: upper mold
164: lower mold 180: injection hole
190: flame 192: torch lamp

Claims (13)

At least two carbon fiber fabrics made of carbon fibers and laminated;
And a polymer matrix coated between the at least two sheets of carbon fiber fabrics such that the carbon fibers are exposed on the surfaces of the at least two sheets of carbon fiber fabrics. The method of claim 1,
A carbon fiber fabric separator for fuel cells, wherein a metal thin plate is bonded between the at least two carbon fiber fabrics. 3. The method according to claim 1 or 2,
A carbon fiber fabric separator for fuel cell, in which the conductive resin is mixed with the polymer resin to increase the electrical conductivity. Consolidating and curing the carbon fiber fabric including the polymer matrix by hot pressing into a separator preform;
A method of manufacturing a carbon fiber fabric separator for fuel cell comprising trimming the separator preform with a separator. 5. The method of claim 4,
The polymer base is a method for producing a carbon fiber fabric separator for fuel cells is applied only on one side of the carbon fiber fabric. The method of claim 5,
The polymer base is a method of producing a carbon fiber fabric separator plate for fuel cells impregnated in the carbon fiber fabric by resin spraying. 42. The method of claim 41,
The polymer base is a method of producing a carbon fiber fabric separator plate for fuel cells impregnated in the carbon fiber fabric by resin transfer molding. 5. The method of claim 4,
The method of manufacturing a carbon fiber fabric separator for fuel cells further comprising the step of temporarily bonding a metal thin plate on one side of the carbon fiber fabric. 9. The method according to any one of claims 4 to 8,
The method of manufacturing a carbon fiber fabric separator for fuel cells further comprising the step of mixing the conductive powder to increase the electrical conductivity to the polymer base. 9. The method according to any one of claims 4 to 8,
An upper mold and a lower mold for hot pressing of the carbon fiber fabric, each of the upper mold and the lower mold having a channel pattern for forming a channel in the cavity and the separating plate, and a surface of the cavity. The method of manufacturing a carbon fiber fabric separator for fuel cell further comprising the step of applying a non-metal conductive powder for separation of the separator preform. 9. The method according to any one of claims 4 to 8,
An upper mold and a lower mold for hot pressing of the carbon fiber fabric, each of the upper mold and the lower mold having a channel pattern for forming a channel in the cavity and the separating plate, and a surface of the cavity. The method for manufacturing a carbon fiber fabric separator for fuel cell further comprising the step of providing a non-metal conductive thin film for the separation of the separator preform. 5. The method of claim 4,
And carbonizing the polymer matrix surplus on the surface of the separator preform using a flame or plasma. 5. The method of claim 4,
The carbon fiber fabric is wound in a roll form, the method of manufacturing a carbon fiber fabric separator plate for a fuel cell is cut to the length required for the production of the separator plate while releasing the roll-shaped carbon fiber fabric from the supply reel.

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