KR102000274B1 - Bipolar plate of fuel cell and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a fuel cell bipolar plate and a method of manufacturing the fuel cell bipolar plate, wherein a thickness of the weft yarn is different from a thickness of the warp yarn, wherein the weft-woven carbon fiber is impregnated with a thermoplastic resin.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a fuel cell separator,

The present invention relates to a fuel cell separator and a method of manufacturing the same.

A fuel cell stack (Stack) is a power generation component that generates electrical energy by electrochemically reacting hydrogen and oxygen among various components of a fuel cell system. Such a fuel cell stack has a unit cell as a minimum unit for generating electric energy, and has a configuration in which several or several such unit cells are stacked in series.

The unit cells are composed of a membrane electrode assembly (MEA) and fuel cell separators which are in contact with both surfaces of the membrane electrode assembly. The membrane electrode assembly has a polymer electrolyte membrane selectively passing only hydrogen ions, and an anode electrode and a cathode electrode are bonded to both sides of the polymer electrolyte membrane.

The fuel cell separator plays a role of collecting the current generated in the unit cell, serves as a separator for maintaining insulation, and discharges water generated by supplying gas (hydrogen, oxygen) to the gas diffusion layer. Such a fuel cell separator plate should be stable in the oxidizing and reducing atmosphere of the anode electrode and the cathode electrode, be capable of preventing gas mixing, and have sufficient electric conductivity.

In addition, the fuel cell separator is provided with a reaction gas flow path for discharging the surplus gas and the reaction product to the outside, while supplying the fuel gas or the oxidizing gas as the reaction gas to the corresponding surface of the membrane electrode assembly. Such a reaction gas flow path may be formed as a separate component and then attached to the fuel cell separator, but is generally formed as a groove-like channel on one surface of the fuel cell separator. That is, in the cathode separator plate, an oxidant gas flow path is formed on the surface facing the membrane electrode assembly, and an oxidant gas containing oxygen flows into the oxidant gas flow path. In the anode separation plate, a fuel gas flow path is formed on the surface facing the membrane electrode assembly, and the fuel gas containing hydrogen flows into the fuel gas flow path.

The present invention relates to a fuel cell comprising a carbon fiber fabricated by crossing a weft yarn and a warp yarn in which a reaction gas flow path is formed without a separate additional process and a thermoplastic resin impregnated with the weft yarn, And a fuel cell separator formed by thermocompression bonding a prepreg for a plate.

However, the technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention provides a prepreg for a fuel cell bipolar plate characterized in that a carbon fiber woven to cross each other with a weft and a slope is impregnated with a thermoplastic resin and the thickness of the weft is different from the thickness of the inclination.

As a ratio of the thickness, the ratio of the diameter of one set of thin yarns to the diameter of one thick yarn can be 0.1 to 0.9.

Wherein the warp yarns and the warp yarns are composed of a plurality of combined yarns and the number of yarns per unit length of the yarns is different from the number of yarns per unit length of the warp yarns.

The carbon fibers may be formed from one or more precursors selected from the group consisting of polyacrylonitrile (PAN), polybenzylimidazole (PBI), cellulose, phenol, and pitch.

The thermoplastic resin may be selected from the group consisting of polyethylene, polyprooylene, polyurethane, polyethyleneterephthalate, polyurea, polyvinylchloride, polyvinylacetate, ethylene vinyl And may include one or more materials selected from the group consisting of ethylenevinylacetate and acryl.

50 to 95 parts by weight of the carbon fiber and 5 to 50 parts by weight of the thermoplastic resin may be included in 100 parts by weight of the prepreg.

According to an embodiment of the present invention, there is provided a fuel cell separator formed by thermally pressing the prepreg.

At least one side of the separator plate may include an area formed with a plurality of first bends and a plurality of second bends gently curved than the first bends.

The ratio of the height of the second bent portion to the height of the first bent portion may be 0.1 to 0.9.

A reaction gas flow path may be formed in a region where the first bent portion is not formed.

The total thickness of the separator plate may be between 0.1 mm and 2 mm.

The bending strength of the separator may be 250 MPa or more.

The electrical conductivity of the separator may be between 10 < ² > S / cm and 10 < ³ > S / cm.

The contact resistance of the separator is 10 m < ≪ / RTI >

According to another embodiment of the present invention, there is provided a method of manufacturing a prepreg, comprising the steps of: impregnating a thermoplastic resin into a carbon fiber woven by crossing weft yarns and warp yarns to produce a prepreg; And thermally compressing and molding the prepreg, wherein the thickness of the weft yarn is different from the thickness of the warp yarn.

The thermocompression bonding can be performed by hot press at a temperature of 50 to 300 DEG C and a pressure of 500 to 30,000 kg / cm < 2 >.

The fuel cell separator according to the present invention uses carbon fiber woven to cross weft yarns and warp yarns having different thicknesses from each other. The carbon fiber yarns have excellent mechanical properties and electrical properties, and at least one side of the separator plate The reaction gas flow path can be formed in a region where a bent portion due to a thick thread is not formed.

1 schematically shows a fuel cell separator according to an embodiment of the present invention.
Figure 2 is a simplified representation of a carbon fiber according to one embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

The drawings are enlarged to clearly illustrate the layers and regions in the drawings. In the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggerated.

The formation of an arbitrary structure on the " one side " of the description means not only that an arbitrary structure is formed in contact with the upper surface (or lower surface) of the substrate, but also an arbitrary structure formed on the substrate and the upper surface The present invention is not limited to this configuration.

Fuel cell separator plate

The present invention provides a prepreg for a fuel cell bipolar plate characterized in that a carbon fiber woven to cross each other with a weft and a slope is impregnated with a thermoplastic resin and the thickness of the weft is different from the thickness of the inclination.

The present invention also provides a fuel cell separator formed by thermally pressing the prepreg.

1 schematically shows a fuel cell separator according to an embodiment of the present invention.

1, the fuel cell bipolar plate 1 according to the embodiment of the present invention is formed by thermally pressing a prepreg impregnated with a thermoplastic resin into carbon fibers woven between weft yarns and warp yarns, And carbon fiber 10 and thermoplastic resin molded body 20 which are woven so as to intersect with each other with inclined faces 100 and 200.

2 schematically shows a carbon fiber 10 according to an embodiment of the present invention.

As shown in FIG. 2, the carbon fiber 10 according to an embodiment of the present invention is formed by weaving the weft yarns to cross the weft yarns 100 and 200, wherein the thickness of the weft yarn is different from the thickness of the warp yarns T ₁ > T ₂ ).

Conventionally, a graphite material is mainly used as a base material of a fuel cell separator. Specifically, the fuel cell separator was manufactured by milling graphite in the form of a flow path. In this case, the mechanical properties of the fuel cell separator were low, and the entire fuel cell stack cost 50% or more and 80% There is a problem that it occupies a specific weight.

As an alternative to such a graphite material, a material obtained by mixing a conductive powder with a polymer material can be used as a base material of a fuel cell separator. However, in this case, it is difficult to ensure the dispersibility of the conductive powder and there is a limitation in improvement of electrical properties.

In addition, since the environment inside the fuel cell is an environment in which hydrogen ion concentration is high and corrosion is easy at high temperature, when the metal material is used as the base material of the fuel cell separator, the surface must have sufficient corrosion resistance. Therefore, a method of coating a metal such as gold, platinum, or tungsten, which has excellent corrosion resistance, on the surface of a base material is indispensable. However, such a coating is not easy to process and has a problem in cost due to expensive metal.

Accordingly, the present invention is characterized in that a carbon fiber is impregnated with a thermoplastic resin and used as a base material of a fuel cell separator.

Hereinafter, the carbon fiber woven to cross the weft yarns and the warp yarns will be described first.

The carbon fibers are for imparting conductivity to the fuel cell separation membrane in X-Y-axis (longitudinal and lateral) directions and Z-axis (height) directions.

The term "carbon fiber" in this specification refers to a fibrous carbon material composed of at least 92% of carbon, and is produced by a method of carbonizing a precursor by heat treatment at about 1000-3000 占 폚. The carbon fiber is characterized by high non-elasticity ratio among non-elasticity and non-elasticity.

Carbon fibers are mainly composed of hexagonal planes of carbon atoms, but these planes are arranged in close parallel to the fiber axis (high orientation, anisotropy) and in a disjointed set (isotropic). Highly oriented carbon fiber has high tensile strength and elasticity, and is treated as high-performance (high grade) carbon fiber and has low coefficient of linear expansion.

Specifically, the carbon fiber is formed from at least one precursor selected from the group consisting of polyacrylonitrile (PAN), polybenzimidazole (PBI), cellulose, phenol, and pitch But is not limited thereto.

In addition, the carbon fibers may be surface-treated to enhance adhesion to the thermoplastic resin. Specifically, the surface treatment of the carbon fibers may be an acid treatment, a plasma treatment, a whiskerization treatment, or a coupling agent treatment.

The carbon fiber is woven so as to cross the weft and the warp.

One thread in this specification is referred to as a " one thread ", and a chunk of threads is referred to as a "one thread ". In other words, one set is a lump of threads consisting of many bones. In this case, one diameter is usually about 7 占 퐉 to about 8 占 퐉, and one set of threads is a lump of an elongated thread made up of a plurality of bones and having a certain thickness and a predetermined width.

When woven fabrics, one set of yarns is pulled in parallel and pulled long, and the other set of yarns is sandwiched between long and parallel pulled yarns to form a yarn in this long and parallel pulled direction as " ) ", And another yarn is called" weft (or weft) ".

And the thickness of the weft yarn is different from the thickness of the warp yarn. Specifically, when the warp yarn is a thick yarn, the warp yarn is a thin yarn, and when the warp yarn is a thick yarn, the yarn is a thin yarn. More specifically, a thick single yarn may be thick or large in number, and a thin yarn may be thin or small in number.

As described above, by manufacturing the fuel cell separator plate using the carbon fibers woven with the wefts and the warp yarns intersecting at different thicknesses, at least one side surface of the separator plate without any additional process is not formed with a bending part due to a thick thread A reaction gas flow path can be formed in the region.

As the ratio of the thickness, it is preferable that the ratio of the diameter of one set of thin yarns to the diameter of one thick yarn is 0.1 to 0.9, more preferably 0.1 to 0.5, but is not limited thereto. At this time, if the ratio of the diameter of one set of thin yarns to the diameter of one thick yarn is less than the above range, there is a problem that weaving is difficult, and the ratio of the diameter of one set of yarns to the diameter of one thick yarn There is a problem that it is difficult to effectively form a reaction gas flow path.

Wherein the warp yarns and the warp yarns are composed of a plurality of combined yarns and the number of yarns per unit length of the yarns is different from the number of yarns per unit length of the warp yarns. Specifically, when the weft yarn is a thick yarn, the number of yarns per unit length of the yarn is smaller than the number of yarns per unit length of the yarn, and when the warp yarn is a single yarn, It can be larger than the number per unit.

In the present invention, a thick yarn is divided into a carbon fiber yarn (12K / thickness: 0.23 mm, width: 0.45 mm) composed of twelve yarns per unit length or a carbon fiber yarn (3K / thickness: 0.11mm, width: 0.15mm) made of a composite yarn with a number of bones per unit length of 3,000 pieces was used as a thin yarn in a single yarn (12K / thickness: 0.28mm, width: Respectively.

The carbon fiber is thermally compressed and formed together with the thermoplastic resin to form a fuel cell separator.

The thermoplastic resin may be a polyamide, a polyethylene, a polyprooylene, a polyurethane, a polyethyleneterephthalate, a polyurea, a polyvinylchloride, But are not limited to, one or more materials selected from the group consisting of polyvinylacetate, ethylenevinylacetate and acryl. Specific polyamides include nylon 6 and nylon 66.

It is preferable that 50 to 95 parts by weight of the carbon fiber and 5 to 50 parts by weight of the thermoplastic resin are contained in 100 parts by weight of the prepreg and 70 to 95 parts by weight of the carbon fiber and the thermoplastic resin More preferably 5 parts by weight to 30 parts by weight, but is not limited thereto. When the carbon fiber is less than the above range, the carbon fiber is completely impregnated with the thermoplastic resin, so that the electrical conductivity of the carbon fiber can not be sufficiently manifested. When the carbon fiber exceeds the above range, the carbon fiber is thermoplastic There is a problem that the impregnation of the carbon fiber is difficult and the gas permeability is lowered because sufficient impregnation can not be performed by the resin. On the other hand, when the thermoplastic resin is less than the above range, the carbon fiber is not sufficiently impregnated with the thermoplastic resin, so that it is difficult to fix the carbon fiber and the gas permeability is lowered. When the thermoplastic resin exceeds the above range, The fibers are completely impregnated with the thermoplastic resin and the electric conductivity of the carbon fibers can not be sufficiently expressed.

The thermoplastic resin is thermo-pressed to be molded to form a thermoplastic resin molded product, whereby the fuel cell separator can be finally formed.

At least one side of the separator plate may include an area formed with a plurality of first bends and a plurality of second bends gently curved than the first bends. A plurality of first bent portions are formed by exposing a part of a thick yarn in a carbon fiber at an intersection of a weft yarn and a warp yarn to an upper portion of the thermoplastic resin molded body without voids and a plurality of second bent yarns are formed at intersections of weft yarns and warp yarns A part of a thin yarn in a carbon fiber is formed by being exposed to the top of the thermoplastic resin molded article without voids, and the height of the bent portion is determined by the thickness of the yarn in one set.

A reaction gas flow path may be formed in a region where the first bent portion is not formed.

That is, the region where the first bent portion is formed due to a thick thread in at least one side of the separator plate can not form the reaction gas flow channel due to high bending, but the region where the second bent portion is formed due to a thin thread, The etching effect can be exerted to form a reaction gas flow path in the form of a channel like a groove.

As the fuel cell separator, an oxidant gas flow path is formed on a surface of the cathode separation plate facing the membrane electrode assembly, and an oxidant gas containing oxygen flows into the oxidant gas flow path. As the fuel cell separation plate, a fuel gas flow path is formed in the anode separation plate on the surface facing the membrane electrode assembly, and the fuel gas containing hydrogen flows into the fuel gas flow path.

The total thickness of the separator plate is preferably from 0.1 mm to 2 mm, but is not limited thereto. In this case, when the total thickness of the separator is less than the above range, there is a problem that the separator does not function properly as a separator. When the total thickness of the separator exceeds the above range, There is a problem that the weight and size of the plate can not be achieved.

The bending strength of the separator may be 250 MPa or more, which is excellent in mechanical properties.

The electrical conductivity of the separator may be 10 < ² > S / cm to 10 < ³ > S / cm, and the contact resistance of the separator may be 10 m &

Manufacturing method of fuel cell separator

The present invention also provides a method of manufacturing a prepreg, comprising: preparing a prepreg by impregnating a carbon fiber woven into a weft and a warp to form a thermoplastic resin; And thermally compressing and molding the prepreg, wherein the thickness of the weft yarn is different from the thickness of the warp yarn.

First, a prepreg is prepared by impregnating thermoplastic resin into carbon fiber woven to cross weft and ramp (S10).

The carbon fiber is impregnated with the thermoplastic resin to form a semi-cured state, thereby preparing a prepreg with an intermediate substrate for forming a fuel cell separator.

The carbon fibers and the thermoplastic resin are as described above.

Next, the prepreg is thermo-compressed and molded.

The prepreg is thermo-compressed and molded to produce a fuel cell separator as a final molded body.

The thermocompression bonding can be performed by hot press at a temperature of 50 to 300 DEG C and a pressure of 500 to 30,000 kg / cm < 2 >. By thermocompression by hot pressing under the above-mentioned temperature and pressure conditions, the carbon fibers can be formed without being completely impregnated with the thermoplastic resin, and the carbon fibers can be formed without internal voids or cracks, thereby fully expressing the electrical conductivity of the carbon fibers There is an advantage to be able to.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the following examples.

[ Example ]

Example  One

A carbon fiber yarn (12K / thickness: 0.23 mm, width: 0.45 mm) having a total number of yarns per unit length of 12,000 was prepared and a carbon fiber yarn (3K / 0.11 mm, width: 0.15 mm). The prepared carbon fiber yarn (12K) and the prepared carbon fiber yarn (3K) were cross-woven to prepare carbon fibers.

85 parts by weight of the prepared carbon fiber was impregnated with 15 parts by weight of a polypropylene thermoplastic resin film to prepare a prepreg.

The produced prepreg was hot-pressed by hot pressing at a pressure of about 10 tons and at a temperature of about 220 DEG C to form a fuel cell separator (200 mm x 200 mm x 1 mm) having a reaction gas flow path.

Example  2

Except that prepared carbon fiber yarn (24K / thickness: 0.28mm, width: 10mm) and prepared carbon fiber yarn (3K / thickness: 0.11mm, width: 0.15mm) A fuel cell separator having a reaction gas flow path was prepared in the same manner as in Example 1.

Example  3

A fuel cell separator having a reaction gas flow path was prepared in the same manner as in Example 1, except that 90 parts by weight of the prepared carbon fiber was impregnated with 10 parts by weight of a polypropylene thermoplastic resin film to prepare a prepreg.

Comparative Example  One

A fuel cell separator (200 mm x 200 mm x 1 mm) in which a reaction gas flow path made of graphite was formed was prepared.

Comparative Example  2

A fuel cell separator (200 mm x 200 mm x 1 mm) having a reaction channel made of polypropylene containing conductive powder of nickel (Ni) was prepared.

Experimental Example

One. Flexural strength  Measure

The bending strengths of the fuel cell separators prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured according to ASTM D 790.

2. Electrical conductivity and contact resistance measurement

The electrical conductivity and contact resistance of the fuel cell bipolar plates prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by a 4-probe method using a Keithley / 6220 / 2182A, USA instrument Lt; / RTI >

The bending strength, electrical conductivity and contact resistance measurement results as described above are summarized in Table 1 below.

Flexural Strength (MPa) Electrical Conductivity (S / cm) Contact resistance (mΩ · ㎠) Example 1 350 210 8.7 Example 2 350 340 8.6 Example 3 300 250 8.3 Comparative Example 1 94 1333 9.3 Comparative Example 2 40 20 200

As shown in Table 1, it was confirmed that the fuel cell bipolar plates manufactured in Examples 1 to 3 were excellent in bending strength, electrical conductivity and contact resistance.

On the other hand, it was confirmed that the fuel cell bipolar plate manufactured in Comparative Example 1 had an excellent electrical conductivity and a contact resistance, but the bending strength was significantly lowered. The fuel cell bipolar plate manufactured in Comparative Example 2 had a flexural strength It is confirmed that there is a problem that the electrical conductivity is greatly lowered and the contact resistance is greatly increased.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (16)

A prepreg for a fuel cell bipolar plate impregnated with a thermoplastic resin in a carbon fiber woven to cross each other with weft and slope,
Wherein the thickness of the weft yarn differs from the thickness of the warp yarn,
Wherein a ratio of the thickness to a thickness of a pair of thin yarns is 0.1 to 0.5,
Wherein the thermoplastic resin is polyprooylene,
Wherein 70 to 95 parts by weight of the carbon fiber and 5 to 30 parts by weight of the thermoplastic resin are mixed with 100 parts by weight of the prepreg,
Prepreg for fuel cell separator.
delete The method according to claim 1,
Wherein the weft yarn and the warp yarns are composed of a plurality of combined yarns,
Wherein the number of slopes per unit length is different from the number of slits per unit length of the weft yarn
Prepreg for fuel cell separator.
The method according to claim 1,
The carbon fibers are formed from at least one precursor selected from the group consisting of polyacrylonitrile (PAN), polybenzylimidazole (PBI), cellulose, phenol and pitch.
Prepreg for fuel cell separator.
delete delete A prepreg according to any one of claims 1, 3, and 4,
Fuel cell separator.
8. The method of claim 7,
Wherein at least one side surface of the separating plate includes a plurality of first bent portions and a region formed with a plurality of second bent portions which are gently curved than the first bent portion
Fuel cell separator.
9. The method of claim 8,
Wherein a ratio of a height of the second bent portion to a height of the first bent portion is 0.1 to 0.5
Fuel cell separator.
9. The method of claim 8,
And a reaction gas flow path is formed in a region where the first bent portion is not formed
Fuel cell separator.
8. The method of claim 7,
The total thickness of the separator plate is 0.1 mm to 2 mm
Fuel cell separator.
8. The method of claim 7,
The bending strength of the separator plate is preferably 250 MPa or more
Fuel cell separator.
8. The method of claim 7,
The electrical conductivity of the separator is 10 < ² > S / cm to 10 < ³ &
Fuel cell separator.
8. The method of claim 7,
The contact resistance of the separator is 10 m < Subordinate
Fuel cell separator.
Preparing a prepreg by impregnating thermoplastic resin into carbon fiber woven to cross weft and slope; And
And thermo-compression bonding the prepreg,
Wherein the thickness of the weft yarn differs from the thickness of the warp yarn,
Wherein a ratio of the thickness to a thickness of a pair of thin yarns is 0.1 to 0.5,
Wherein the thermoplastic resin is polyprooylene,
Wherein 70 to 95 parts by weight of the carbon fiber and 5 to 30 parts by weight of the thermoplastic resin are mixed with 100 parts by weight of the prepreg,
A method for manufacturing a fuel cell separator.
16. The method of claim 15,
The thermocompression bonding is performed by a hot press at a temperature of 50 캜 to 300 캜 at a pressure of 500 kg / cm 2 to 30,000 kg / cm 2
A method for manufacturing a fuel cell separator.

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