KR101777214B1 - Fuel cell separator plate fabriation method and the fuel cell separator plate using the same - Google Patents

Abstract

The present invention relates to a process for producing a fuel cell bipolar plate having heat resistance and acid resistance, comprising the steps of mixing a graphite and a fluorocarbon polymer and then producing a plate-form intermediate, said intermediate being heated at a temperature of 280 to 360 ° C for 1 to 60 minutes And then cooling and molding the cooled intermediate to manufacture a flow path.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a fuel cell separator, and a fuel cell separator using the fuel cell separator.

The present invention relates to a method of manufacturing a fuel cell bipolar plate having heat resistance and acid resistance, and a fuel cell bipolar plate manufactured using the same.

BACKGROUND ART A fuel cell is a cell assembled so that the oxidation reaction of fuel (hydrogen, phosphoric acid, methanol, etc.) is caused to occur electrochemically, and the free energy change accompanying the oxidation reaction can be directly taken out as electric energy. Fuel cells can be classified into solid oxide fuel cells (SOFCs), phosphoric acid fuel cells (PAFCs), and phosphoric acid fuel cells depending on the type of fuel and reaction catalyst. A proton exchange membrane fuel cell (PEMFC), and a direct methanol fuel cell (DMFC).

Separating plates separating the electrolyte, fuel electrode and air electrode from each other in the stack parts of the fuel cell are required to have characteristics such as electrical conductivity, gas permeability, strength, corrosion characteristics, and elution characteristics. . The metal separator has disadvantages in corrosion characteristics, and the graphite separator has a disadvantage of high manufacturing cost and large volume. According to such a problem, a method of mixing a thermosetting resin or a thermoplastic resin into a graphite powder and then casting the separator plate by compression molding and injection molding is used.

In particular, phenol resins and epoxy resins are used as thermosetting resins in the production of fuel cell separators for high temperature, and super engineering plastics stable at temperatures of 150 ° C or higher are used as thermoplastic resins.

A prior art document on a method for manufacturing a high-temperature acid resistant fuel cell separator disclosed in U.S. Patent Publication No. 2010-0307681 discloses a three-layered separator having a structure in which a plate is inserted between two plates in which a channel is formed, It requires a molding process of three or more times for manufacturing, takes a long time to manufacture, requires three or more sets of molds, and thus has a very complicated manufacturing process.

U.S. Patent Application Publication No. 2010-0307681

It is an object of the present invention to provide a method for manufacturing a fuel cell separator which is applicable to high temperature and strongly acidic atmospheres and which is simple and efficient in the manufacturing process.

It is still another object of the present invention to provide a fuel cell bipolar plate manufactured using the fuel cell bipolar plate manufacturing method.

In order to solve the above problems, a method for manufacturing a fuel cell bipolar plate according to the present invention comprises the steps of mixing a graphite and a fluorocarbon polymer and then producing a plate-shaped intermediate, heating the intermediate at a temperature of 280 to 360 ° C for 1 to 60 minutes And cooling the cooled intermediate product to form a flow path. The present invention also provides a method for manufacturing a fuel cell bipolar plate, comprising:

The mixing ratio of the graphite and the fluorocarbon polymer may be 60 to 90 wt% of graphite and 10 to 40 wt% of fluorocarbon polymer.

The fluorocarbon polymer may be at least one selected from the group consisting of fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), polytetrafluoroethylene (PTEE) And a combination thereof.

The plate intermediate preparation step may be molding under a pressure of 800 to 5000 psi.

The step of preparing the plate-like intermediate may be carried out at 20 to 26 ° C.

The step of maintaining the intermediate at a temperature of 280 to 360 ° C for 1 to 60 minutes followed by cooling may be a rapid heating and rapid cooling using an induction heating method.

The cooled intermediate may be in a semi-hardened state.

The molding may be a combination of any molding method selected from the group consisting of compression molding, injection molding, extrusion molding, or a combination thereof.

The molding may further comprise adjusting the pressure from 500 psi to 5000 psi.

The molding may be a mold having a channel depth of 0.05 to 1.05 mm.

The mold is formed at a pressure of 500 to 1000 psi and a channel depth of 9.5 to 28.5% relative to the mold depth, a channel depth of 28.5 to 57.1% relative to the mold depth at a pressure of 1000 to 2000 psi, The depth may be formed to be 57.1 to 85.7%, and the channel depth to the mold depth may be formed to be 85.7 to 100% at a pressure of 3000 to 4000 psi.

The present invention also provides a fuel cell bipolar plate manufactured by the manufacturing method according to an embodiment of the present invention.

The fuel cell separator may be applied to any one selected from the group consisting of a direct methanol fuel cell (DMFC), a polymer electrolyte fuel cell (PEMFC), and a phosphoric acid fuel cell (PAFC).

In the fuel cell separator, a plurality of fuel channels through which fuel flows may be formed in one separator plate activation area, and fuel may be introduced into the fuel channels through different inlet manifolds and discharged through a discharge manifold.

The present invention also provides a fuel cell comprising the fuel cell bipolar plate and a fuel electrode (anode) and a cathode (cathode) arranged to face each other with the separator interposed therebetween.

The fuel cell separator according to the present invention and its manufacturing method have the effect of not decreasing the conductivity of the separator even in a high temperature and strong acidic atmosphere.

INDUSTRIAL APPLICABILITY The fuel cell separator and the method of manufacturing the same according to the present invention have a simple manufacturing process and a shortened manufacturing time.

INDUSTRIAL APPLICABILITY The fuel cell separator according to the present invention and its manufacturing method have an effect of high electrical conductivity and airtightness.

Further, the fuel cell separator according to the present invention and its manufacturing method have an excellent injection moldability and an effect that the thickness deviation of the separator plate during compression molding is small.

1 is a flowchart showing a method of manufacturing a fuel cell bipolar plate of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having ", and the like, specify that the presence of stated features, integers, steps, operations, elements, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless expressly defined herein Do not.

In order to solve the above problems, a method for manufacturing a fuel cell bipolar plate according to the present invention comprises the steps of mixing a graphite and a fluorocarbon polymer and then producing a plate-shaped intermediate, heating the intermediate at a temperature of 280 to 360 ° C for 1 to 60 minutes And cooling the cooled intermediate material to form a flow path.

Hereinafter, a method of manufacturing a fuel cell bipolar plate according to an embodiment of the present invention will be described in detail with reference to FIG. 1 is a flowchart showing a method of manufacturing a fuel cell bipolar plate of the present invention.

1) mixing step of graphite and fluorocarbon polymer (S1-1)

A thermosetting resin or a thermoplastic resin can be applied to manufacture a fuel cell separator capable of maintaining a high electrical conductivity even at a high temperature. Examples of the thermoplastic resin include polyacrylate, polysulfone, polyethersulfone, polyphenylenesulfide, polyetherether ketone, and polyimide, which have high temperature stability. Polyetherimide, fluorocarbon polymer, liquid crystal polymer, and the like can be used.

However, it is also possible to use fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), polytetrafluoroethylene (PTFE) , And a combination thereof can be applied to a phosphoric acid type fuel cell (PAFC) which is operated at a high temperature of 200 ° C or higher and a phosphoric acid concentration of at least 90% desirable.

The graphite may be selected from the group consisting of natural graphite, graphite impression, expanded graphite, artificial graphite, carbon black, and graphene, though not limited thereto.

It is possible to solve the corrosion problem of the metal separator by mixing the graphite and the fluorocarbon polymer and solve the disadvantage that the manufacturing cost of the graphite separator is high and the bulky is large.

The mixing ratio of graphite and fluorocarbon polymer may be 60 to 90 wt% of graphite and 10 to 40 wt% of fluorocarbon polymer. Preferably, the mixing ratio of graphite and fluorocarbon polymer is 80 to 90 wt% of graphite, 10 to 10 wt% of fluorocarbon polymer To 20 wt%.

In the present embodiment, it can be advantageous in injection molding and compression molding by containing the graphite in an amount of 60 to 90 wt% and the fluorocarbon polymer in an amount of 10 to 40 wt%, and can be applied to a high temperature fuel cell, and the accuracy, gas permeability, And the like can be improved.

If the graphite is contained in an amount of less than 60 wt%, a problem of a decrease in electrical conductivity (resistance increase) may occur. If the graphite is contained in an amount exceeding 90 wt%, the gas permeability may become poor.

If the content of the fluorocarbon polymer is more than 40 wt%, it is advantageous for molding, but the electrical conductivity is lowered, which causes a deterioration of the fuel cell performance. Conversely, if the polymer content is less than 10 wt%, the electrical conductivity is improved but the gas permeates. When the electric conductivity and the gas permeability are considered, it is preferable that the fluorocarbon polymer is contained in an amount of 10 to 40 wt%.

2) Preparation of plate-shaped graphite-fluorocarbon polymer intermediate (S1-2)

The step of preparing the intermediate plate in the form of plate should maintain a pressure of 3000 psi or more because sufficient pressure is applied to the plate. Preferably, the plate-form intermediate preparation step may be molding under a pressure of 800 to 5000 psi.

It is preferable that the pressure is in the range of 800 to 5000 psi when the automation and the robon transfer are applied, and the pressure is 3000 to 5000 psi when the pressure is manually adjusted. If the pressure is less than 3000 psi by hand, the failure of the intermediate may occur.

The step of preparing the plate-like intermediate may be carried out at a room temperature of 20 to 26 ° C.

3) High temperature treatment and cooling (S2)

The step of maintaining the intermediate at a temperature of 280 to 360 ° C for 1 to 60 minutes and then cooling may be performed by rapid heating and rapid cooling for 1 to 3 minutes using the induction heating method.

When the induction heating is applied as described above, the time of the manufacturing process is shortened and the time and the economical cost can be shortened. However, the present invention is not limited thereto.

The high-temperature processing and cooling steps may be performed by a common high-temperature processing and cooling method, or a rapid-heating cooling method used in an injection molding process. Alternatively, one heating / cooling apparatus may be used or one heating apparatus, The cooling and high temperature treatment steps may be performed separately using equipment.

The graphite-fluorocarbon polymer intermediate subjected to the high temperature treatment and cooling may be a flat plate in a semi-hardened state, and the fluorocarbon polymer flows inside the flat plate to prevent gas (particularly hydrogen) from permeating .

4) Flow forming (S3)

The molding may be a combination of any one molding method selected from the group consisting of compression molding, injection molding, extrusion molding, and a combination thereof. Preferably, the molding can be performed by compression molding using a mold having a channel depth of 0.05 to 1.05 mm Can be used.

The molding may further comprise adjusting the pressure from 500 psi to 5000 psi.

The present invention has the effect of adjusting the depth of the channel of the separator using the pressure condition and the mold. This is because the intermediate is semi-hardened through the high temperature treatment and cooling step (S2), and the fluorocarbon polymer can flow inside the intermediate to prevent gas (especially hydrogen) from permeating.

In detail, the molding is performed at a pressure of 500 to 1000 psi to form a channel depth of 9.5 to 28.5% relative to the mold depth, a channel depth to a mold depth of 28.5 to 57.1% at a pressure of 1000 to 2000 psi, The depth of the channel relative to the depth is formed to be 57.1 to 85.7%, and the depth of the channel to the depth of the mold is formed to be 85.7 to 100% at a pressure of 3000 to 4000 psi.

The above-mentioned molding can be produced by high-temperature compression molding at a temperature of 260 DEG C or less, high-temperature injection molding, high-temperature extrusion molding or the like, and such high-temperature molding is very effective in improving the surface roughness of the fuel cell separator.

According to the present invention, the fuel cell separator can be manufactured by molding as described above, and thus a machining machine, a vacuum adsorption facility, a fixing facility, a dust collecting facility, and the like are not required for the machining process. Therefore, the manufacturing cost of the fuel cell separator can be reduced. Particularly, in order to apply to the PAFC, a large separator plate of 2500 cm 2 or more, which requires high-grade processing equipment, is required. The separator plate can be simply manufactured by the method for manufacturing a fuel cell separator according to the present invention.

5) Fuel cell separation plate

The present invention also provides a fuel cell bipolar plate manufactured by the manufacturing method according to an embodiment of the present invention.

The fuel cell separator has a heat-resistant and acid-resistant property that can be used even under a high-temperature condition of 200 ° C or higher and a phosphoric acid condition of 90% or higher. Therefore, the DMFC, the PEMFC, The present invention can be applied to any one selected from the group consisting of:

In the fuel cell separator, a plurality of fuel channels through which fuel flows may be formed in one separator plate activation area, and fuel may be introduced into the fuel channels through different inlet manifolds and discharged through a discharge manifold.

The present invention also provides a fuel cell comprising the fuel cell bipolar plate and a fuel electrode (anode) and a cathode (cathode) arranged to face each other with the separator interposed therebetween.

Hereinafter, experimental examples for confirming the effect of the fuel cell separator according to the present invention will be described in detail. The following experimental examples are illustrative of the present invention and the present invention is not limited to the conditions of the following experimental examples.

[Production Example 1: Fuel cell separator according to graphite-FEP resin content ratio]

As shown in Table 1 below, the content of graphite and fluorinated ethylene propylene (FEP) resin was varied to manufacture a fuel cell separator.

Example 1 Example 2 Example 3 Graphite: FEP resin (wt%) 80:20 85:15 90:10

[Experimental Example 1: Conductivity, flexural strength and gas tightness]

Conductivity, flexural strength and gas tightness according to the content ratio of graphite and FEP resin were confirmed, and the results are shown in Table 2 below.

Example 1 Example 2 Example 3 Conductivity (S / cm) 94 122 162 Flexural Strength (MPa) 52 47 39 Gas tightness (cc / min) No leak No leak No leak

As shown in Table 2, as the FEP content was decreased, the conductivity was improved and the bending strength was lowered, but it was maintained at a level that can be used as a separator for high temperature corrosion resistant fuel cells. In particular, even when the content of the FEP resin was about 10 wt%, it was confirmed that the gas tightness was maintained by the combination characteristics of the expanded graphite and the FEP resin.

It was confirmed that even when the amount of graphite was about 60% by weight, it had an electric conductivity sufficiently applicable to the fuel cell. Therefore, it was confirmed that the amount of the conductive material can be properly maintained even in the case of the separator of the high-conductivity fuel cell, thereby facilitating the formation of the separator plate.

In particular, although the amount of flowable resin must be large in order to secure the fluidity of the material during injection molding, existing methods have difficulty in securing the injection property while increasing the amount of the conductive filler. Carbon composite material of the present invention can be added up to 30 to 40 wt% of the amount of the FEP resin, which is considered to be greatly advantageous in the use of the injection molding in the production of the fuel cell separator according to the present invention.

In addition, since the carbon composite material produced by the present invention has high fluidity, it has an advantage of reducing the thickness variation of the separator during compression molding.

Since the carbon composite material having the composition shown in Table 1 secures the conductivity, flexural strength and airtightness, the fuel cell separator can be manufactured through a simple process of compression molding at a temperature of 280 to 360 ° C for 1 to 20 minutes.

[Experimental Example 2: Rate of forming a flow path according to pressure]

Example 2 pressure 500 1000 2000 3000 4000 5000 Depth of die in mold (mm) 1.05 1.05 1.05 1.05 1.05 1.05 Depth of flow path of separation plate (mm) 0.1 0.3 0.6 0.9 1.05 1.05 Euro formation rate 9.5% 28.5% 57.1% 85.7% 100% 100%

The graphite-FEP resin intermediate prepared in Example 2 was formed into a channel with different pressures under the conditions shown in Table 3, and the channel depth (channel formation ratio) with respect to the channel depth and the mold depth is shown in Table 3.

As shown in Table 3, the method of manufacturing the fuel cell bipolar plate according to the present invention can easily control the channel depth by adjusting the pressure conditions.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be possible. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (15)

Mixing the graphite and the fluorocarbon polymer to prepare a plate-shaped intermediate,
Maintaining the intermediate at a temperature of 280 to 360 DEG C for 1 to 60 minutes and then cooling; and
And molding the cooled intermediate to manufacture a flow path,
The cooled intermediate is in a semi-hardened state,
The mold is formed at a pressure of 500 to 1000 psi at a depth of 9.5 to 28.5% relative to the mold depth,
The channel depth to the mold depth is formed to 28.5 to 57.1% at a pressure of 1000 to 2000 psi,
The channel depth is formed to be 57.1 to 85.7% with respect to the mold depth at a pressure of 2000 to 3000 psi,
Wherein the channel depth is formed to 85.7 to 100% relative to the mold depth at a pressure of 3000 to 4000 psi. The method according to claim 1,
Wherein a mixing ratio of the graphite and the fluorocarbon polymer is 60 to 90 wt% of graphite and 10 to 40 wt% of a fluorocarbon polymer. The method according to claim 1,
The fluorocarbon polymer may be selected from the group consisting of fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), polytetrafluoroethylene (PTFE) And a combination of any of the foregoing. The method according to claim 1,
Wherein the plate-shaped intermediate production step is performed under a pressure of 800 to 5000 psi. The method according to claim 1,
Wherein the step of preparing the plate-form intermediate is carried out at 20 to 26 占 폚. The method according to claim 1,
Wherein the step of maintaining the intermediate at a temperature of 280 to 360 ° C for 1 to 60 minutes and then cooling is performed by high-speed heating and high-speed cooling using an induction heating method. delete The method according to claim 1,
Wherein the forming is performed by combining any one of molding methods selected from the group consisting of compression molding, injection molding, extrusion molding, and combinations thereof. delete The method according to claim 1,
Wherein the forming uses a mold having a channel depth of 0.05 to 1.05 mm. delete A fuel cell bipolar plate manufactured by the manufacturing method according to any one of claims 1 to 6, 8, and 10. 13. The method of claim 12,
Wherein the fuel cell separator is applied to any one selected from the group consisting of a direct methanol fuel cell (DMFC), a polymer electrolyte fuel cell (PEMFC), and a phosphoric acid fuel cell (PAFC). 13. The method of claim 12,
Wherein the fuel cell separator has a plurality of fuel channels through which fuel flows in one separator plate activation area,
Wherein fuel is introduced into the fuel channel through different inlet manifolds and discharged through a discharge manifold. A fuel cell bipolar plate according to claim 12;
And a fuel electrode (anode) and a cathode (cathode) arranged to face each other with the separator interposed therebetween.

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