KR20060081185A - A cabon separator for fuel cell, and a method for manufacturing the same - Google Patents

Abstract

The present invention relates to a carbon separator used in a fuel cell that obtains electrical energy by an electrochemical reaction between oxygen and hydrogen, and a method of manufacturing the same.

The present invention provides at least one epoxy resin selected from the group consisting of bisphenol-type epoxy resins, novolac-type epoxy resins, biphenyl-type epoxy resins and biphenyl ether-type epoxy resins: 7 to 22% by weight, acid anhydride-based curing agents, amines At least one curing agent selected from the group consisting of a curing agent and a phenolic curing agent: 0.3 to 16% by weight and the remaining graphite, the average particle size of the epoxy resin, the curing agent and graphite is 0.2 to 20㎛, the angle of repose is 15 to 30 °, wherein the graphite is a carbon separator raw material containing not more than 0.20% by weight of Fe, and not more than 0.20% by weight of Al, and

At least one filler selected from the group consisting of silica, barium sulfate, alumina, magnesium oxide, calcium carbonate, mica, kaolin, bentonite and aluminum hydroxide, based on 100 parts by weight of the separator raw material: 0.03 to 0.1 parts by weight of fuel A carbon separator for batteries is provided.

In addition, a method of manufacturing a carbon separator for a fuel cell is provided.

The present invention can provide a carbon separator for fuel cells having low elution of metal ions and high battery output by using graphite, epoxy resin, and a hardener mixed powder having little metal impurities in the carbon separator.

Fuel cell, carbon separator, iron, aluminum, epoxy resin, hardener, graphite

Description

Carbon separator for fuel cell and method for manufacturing same {A cabon separator for fuel cell, and a method for manufacturing the same}

The present invention relates to a carbon separator used in a fuel cell that obtains electrical energy by an electrochemical reaction between oxygen and hydrogen. More specifically, the use of graphite, which contains less metal impurities, results in less elution of metal ions and battery output. The present invention relates to a carbon separator for a fuel cell and a manufacturing method thereof.

Fuel cells using carbon separators that obtain electrical energy by electrochemical reactions of oxygen and hydrogen are environmentally friendly and are expected to be used as next-generation energy alternatives to petroleum, since the fuel can be used infinitely. In particular, automotive applications that do not emit exhaust gases to the atmosphere are already in practical use.

Conventional technologies for carbon separators include Japanese Patent Laid-Open Nos. 2001-76737 and 2002-270196. Japanese Laid-Open Patent Publication No. 2001-76737 discloses an integrated surface by exposing one side of a hydrophilic sheet (nonwovens) on the surface of a reaction gas passageway of a molded body containing expanded graphite and a binder and embedding the other side into the molded body. The present invention relates to a carbon separator for fuel cells with low metal ion elution. The metal ions to be tested include silicon (Si) ions and sodium (Na) ions. However, the prior art uses expanded graphite as a carbon separator material, and when the fuel cell of the solid polymer electrolyte is operated, a large amount of hydrogen ions (H ⁺ ) are present in the polymer electrolyte membrane, and the inside of the polymer electrolyte membrane and the electrode Since the periphery becomes strongly acidic, there is a problem that the elution of metal ions cannot be sufficiently prevented, leading to a decrease in battery output.

In addition, the Japanese Laid-Open Patent Publication No. 2002-270196 relates to a stainless steel conductive carbon separator of a passivation film formed with rugged surfaces and formed of chromium (Cr), wherein the metal ions to be tested are iron (Fe) ions and chromium ( Cr) ion and nickel (Ni) ion. However, in the prior art, since the stainless steel conductive carbon separator is used as a passivation film, it is not possible to sufficiently prevent the dissolution of metal ions, resulting in a decrease in battery output.

The present invention is to solve the above-mentioned problems of the prior art, the carbon separation plate for fuel cells with high dissipation of metal ions and high battery output by using a graphite, epoxy resin, hardener powder mixed with a few metal impurities in the carbon separator plate And to provide a method for manufacturing the same, there is a purpose.

The present invention for achieving the above object,

At least one epoxy resin selected from the group consisting of bisphenol type epoxy resins, novolac type epoxy resins, biphenyl type epoxy resins and biphenyl ether type epoxy resins: 7 to 22% by weight, acid anhydride curing agents, amine curing agents and phenols At least one curing agent selected from the group consisting of system-based curing agents: 0.3-16% by weight and the remaining graphite, wherein the average particle size of the epoxy resin, curing agent and graphite is 0.2-20 占 퐉, angle of repose is 15-30 °, Graphite is a carbon separator raw material containing not more than 0.20% by weight of Fe and not more than 0.20% by weight of Al, and

At least one filler selected from the group consisting of silica, barium sulfate, alumina, magnesium oxide, calcium carbonate, mica, kaolin, bentonite and aluminum hydroxide, based on 100 parts by weight of the separator raw material: 0.03 to 0.1 parts by weight of fuel It relates to a battery carbon separator.

The present invention also relates to at least one epoxy resin selected from the group consisting of bisphenol type epoxy resins, novolac type epoxy resins, biphenyl type epoxy resins and biphenyl ether type epoxy resins: 7 to 22% by weight, acid anhydride curing agents, At least one curing agent selected from the group consisting of an amine curing agent and a phenolic curing agent: 0.3 to 16% by weight and the remaining graphite, wherein the average particle size of the epoxy resin, the curing agent and the graphite is 0.2 to 20 µm, and the angle of repose is 15 to 30 ° and the graphite is pulverized a carbon separator raw material containing not more than 0.20% by weight of Fe and not more than 0.20% by weight of Al;

At least one filler selected from the group consisting of silica, barium sulfate, alumina, magnesium oxide, calcium carbonate, mica, kaolin, bentonite and aluminum hydroxide, based on 100 parts by weight of the finely divided carbon separator: 0.03 to 0.1 parts by weight Dry mixing and then pulverizing to prepare a molding material powder;

At least one curing agent selected from the group consisting of an acid anhydride curing agent, an amine curing agent and a phenolic curing agent: 5-20 wt% and the remaining graphite, the graphite having 0.20 wt% or less Fe and 0.20 wt% Al At least one filler selected from the group consisting of silica, barium sulfate, alumina, magnesium oxide, calcium carbonate, mica, kaolin, bentonite and aluminum hydroxide, based on 100 parts by weight of the raw material for molding die containing : Filling the molding material powder in a molding die prepared by adding 0.03 ~ 0.1 parts by weight; And

It relates to a manufacturing method of a carbon separator for a fuel cell comprising a; forming a carbon separator by applying a pressure of 500 ~ 1000kg / ㎠ to a molding die filled with the molding material powder at 130 ~ 200 ℃. .

Hereinafter, the carbon separator of the present invention will be described in detail.

The present inventors have proposed that the present invention is focused on the fact that when Fe and Al contained in graphite, which is the main material of the carbon separator, are small, the amount of metal ions eluted can be reduced to prevent the battery output of the carbon separator from decreasing. First, look at the reasons for limiting the carbon separation plate of the present invention.

Carbon separator of the present invention is made by adding a filler to the carbon separator raw material. The carbon separator raw material is composed of an epoxy resin, a curing agent and graphite.

The carbon separator raw material of the present invention comprises an epoxy resin: 7 to 22% by weight (hereinafter, only referred to as '%').

If the epoxy resin content is less than 7%, the mechanical strength of the carbon separator is lowered, and if the content of the epoxy resin is more than 22%, there is a problem that the conductivity of the carbon separator is reduced, it is preferable to limit the content to 7 ~ 22%. . In addition, the epoxy resin may be bisphenol type, novolak type, biphenyl type and biphenyl ether type and the like, it is preferable that the form is a solid powder.

In addition, the carbon separator raw material of the present invention contains a curing agent: 0.3 ~ 16%.

When the content of the curing agent is less than 0.3%, the curing becomes insufficient, and when the content of the curing agent exceeds 16%, the curing proceeds too quickly, making it difficult to work. Therefore, the content is preferably limited to 0.3 to 16%. In addition, the curing agent may be an acid anhydride type, amine type, phenol type, etc., considering the heat resistance of the molded body, novolak-type phenolic resin is most preferred. Moreover, it is preferable that a form is a solid powder.

The remainder of the carbon separator raw material of the present invention is composed of graphite in addition to the above components. It is preferable to use graphite containing 0.20% or less of Fe and 0.20% or less of Al, because the Fe is more than 0.20% or the Al is more than 0.20%, so that the metal elutes more. This is because ions enter the polymer electrolyte membrane, and thus the ion conductivity of the polymer electrolyte membrane is lowered, resulting in a decrease in battery output. Both natural graphite and artificial graphite can be used in the present invention.

The carbon separation plate raw material of the present invention preferably has an average particle size of 0.2 ~ 20㎛, the reason is that if the size is less than 0.2㎛ small particles are difficult to uniformly dispersed, if more than 20㎛ This is because the mechanical strength of the carbon separator may decrease.

In addition, the raw material of the carbon separation plate of the present invention preferably has an angle of repose (flowability) of 15 to 30 °, because it is possible to stably inject the powder into the molding die if the angle of repose is in the above range. Because.

In the present invention, 0.03 to 0.1 parts by weight of the filler is added to 100 parts by weight of the carbon separator raw material prepared as described above. If the addition amount of the filler is less than 0.03 parts by weight based on 100 parts by weight of the carbon separator, the flowability of the powder is not good, and the filling is not good. If the amount is more than 0.1 parts by weight, the conductivity is lowered. It is preferable to limit it to 0.03-0.1 weight part with respect to a part.

In addition, in the present invention, 0.5 to 3 parts by weight of a curing accelerator may be further added to 100 parts by weight of the above-described carbon separator raw material. When the amount of the curing accelerator is less than 0.5 parts by weight based on 100 parts by weight of the carbon separator, the strength of the epoxy resin is insufficient due to the lack of promotion of the polymerization reaction, and when the amount is more than 3 parts by weight, the conductivity is lowered. It is preferable to limit to 0.5-3 weight part with respect to 100 weight part of plate raw materials. As the curing accelerator, imidazole-based, polyamide-based and organophosphorus-based may be used.

Hereinafter, the manufacturing method of the carbon separator for fuel cells of the present invention will be described.

First, a carbon separator raw material composed of an epoxy resin, a curing agent, and graphite (containing 0.02 wt% or less of Fe and 0.02 wt% or less of Al) is pulverized. The pulverization method is not particularly limited, and a method of coarsely pulverizing the epoxy resin, the curing agent, and the graphite powder with a hammer mill to 50 to 300 μm, and then using the jet mill or the like to finely pulverize it to 0.2 to 20 μm is available. .

Thereafter, a filler is added to the finely ground epoxy resin, a curing agent, and graphite powder, followed by dry mixing, and then finely ground to prepare a molding material powder. This process is not particularly limited, but it is mixed in dry Henkel mixer at a speed of 30 to 60 m / s, followed by dry mixing to uniformly disperse epoxy resins, hardeners, and graphite using a biaxial kneader. After cooling by hot kneading, a method of pulverizing to 0.2 to 20 μm with a jet mill or the like is available. The filler is preferably added in an amount of 0.03 to 0.1 parts by weight based on 100 parts by weight of the carbon separator raw material.

Thereafter, the pulverized molding material powder is filled in a molding die. It is preferable that the molding die is added with 0.03 to 0.1 parts by weight of a filler with respect to 100 parts by weight of the raw material for the molding die, to the raw material for the molding die composed of 5 to 20% by weight of the curing agent and the remaining graphite. At this time, the graphite is preferably graphite containing 0.20% by weight or less of Fe and 0.20% by weight or less of Al. When the content of the curing agent is less than 5% by weight, the mechanical strength of the molding die is low, and when the content of the curing agent exceeds 20% by weight, the mechanical strength of the molding die is not only lowered, but the hardening progresses rapidly, so that it is difficult to work. Silver is preferably limited to 5 to 20% by weight. An acid anhydride type, an amine type, and a phenol type may be used as the curing agent, and in view of the heat resistance of the molded body, a novolac phenol resin is most preferable.

In addition, when the content of Fe and Al contained in the graphite exceeds 0.20% by weight, the metal to be incorporated into the carbon separation plate during the forming of the carbon separation plate, the metal ions enter the polymer electrolyte membrane, thereby causing the polymer electrolyte membrane As the ion conductivity is lowered, the battery output is lowered. Since the molding die of the present invention as described above is not made of a metal material, it is possible not only to prevent the metal from being mixed in the carbon separator, but also to remove the air in the carbon separator raw material mixture powder completely.

In addition, when the amount of the filler added is less than 0.03 part by weight based on 100 parts by weight of the raw material for molding die, the fluidity of the powder is not good, and the filling is not good. It is preferable to limit it to 0.03-0.1 weight part with respect to 100 weight part.

Thereafter, while applying a pressure of 500 ~ 1000kg / ㎠ to the molding die filled with the molding material powder as described above is maintained at 130 ~ 200 ℃ is produced as a carbon separator. If the pressure applied to the molding die is less than 500kg / cm 2, the mechanical strength decreases and the density of the tissue is insufficient, which causes gas leakage. If the pressure exceeds 1000kg / cm 2, segregation of epoxy is physically generated. The pressure is preferably limited to 500 to 1000 kg / cm 2.

In addition, when forming the carbon separator plate is less than 130 ℃ forming temperature is less than the mechanical strength and densification of the tissue is not a cause of gas leakage, if it exceeds 200 ℃ physically eluting and segregation of the epoxy, Molding temperature is preferably limited to 130 ~ 200 ℃.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

EXAMPLE

The raw material of the carbon separator prepared as shown in Table 1 was coarsely ground to an average particle size of 230 to 250 μm using a hammer mill, and then finely ground to an average particle size of 5 to 7 μm using a jet mill. Thereafter, silica powder having an average particle diameter of 0.02 μm was added to the pulverized raw powder, and then mixed in a Henschel mixer at a rotational speed of 31 to 36 m / s to prepare a molding material powder. The molding material powder was hot kneaded with a biaxial kneader and cooled, and then pulverized to an average particle size of 5 탆 with a jet mill. Each raw material powder manufacturing conditions and post-preparation angle of repose are shown in Table 2.

  division Carbon separator raw material composition (% by weight) Filler (part by weight based on 100 parts by weight of raw material) Epoxy resin Hardener black smoke Bisphenol A type Novolac Type Phenolic Resin Natural graphite Artificial graphite Fe content Al content Silica Invention 1 16 5 79 - 0.19 0.12 0.05 Comparative material 16 5 79 - 0.39 0.60 0.08 Invention 2 12 6 - 82 0.18 0.17 0.08

division Average particle size after coarse grinding (㎛) Average particle size after pulverization (㎛) Rotation speed during dry mixing (m / s) Angle of repose (°) Invention 1 250 5 32 20 Comparative material 250 5 31 22 Invention 2 230 7 36 23

Thereafter, a graphite molding die and a conventional stainless metal mold to be used for forming a carbon separator were manufactured. The graphite material forming die was roughly ground to a mean particle size of 250 μm using a hammer mill, and then pulverized each powder to an average particle size of 5 μm using a jet mill. Thereafter, 0.8 parts by weight of silica having an average particle size of 0.02 μm was added to the finely ground material powder, and added to a Henschel mixer in a Henschel mixer to dry mix at a rotational speed of 31 to 36 m / s to prepare a powder for molding die. It was. The powder was hot kneaded with a biaxial kneader and then molded into a flat plate and carbonized at 1000 ° C. under a nitrogen gas atmosphere. Thereafter, plastic cutting was performed to manufacture a molding die. The bending strength of the molding die thus produced was 62-63 MPa.

Molding die raw material composition (% by weight) Filler (part by weight based on 100 parts by weight of raw material) Hardener black smoke Novolac Type Phenolic Resin Natural graphite Fe content Al content Silica 14 84 0.19 0.12 0.08

Thereafter, the molding material powder was filled in the graphite material forming die and the conventional stainless steel mold. Thereafter, the carbon separator for fuel cell was formed by repeating 100 times of maintaining the pressure and molding temperature conditions of Table 4 for 30 seconds or more, and the atmosphere temperature was 400 ° C. The flexural strength of the carbon separator thus prepared was 62 MPa.

division Furtherance Molding die material Pressure (kg / ㎠) Molding temperature (℃) Inventive Example 1 Invention 1 Graphite material 500 150 Comparative Example 1 Comparative material Stainless material 500 150 Inventive Example 2 Invention 2 Graphite material 500 200 Comparative Example 2 Invention 2 Stainless material 500 200

The proton conductive polymer electrolyte (Perfluorosulfonic acid) was inserted into the cathode and the anode, and then the anode-side conductive carbon separator and the cathode-side conductive carbon separator were disposed on the outside of the cathode and the anode (1 cell), and 50 cells were stacked. The stacked cells were fastened with a single plate of a stainless steel plate by sandwiching a current collector plate and an insulation plate to manufacture a fuel cell.

Thereafter, the fuel cell manufactured as described above was maintained at 80 to 90 ° C., and a humid hydrogen gas was supplied to the dew point at the anode side so as to be 75 to 85 ° C., and the humidity at the cathode side to 70 to 80 ° C. One air was supplied. The open-circuit voltage was measured in the case of no load not outputting current to outside, and the results are shown in Table 5 below. In addition, the continuous power generation test was conducted under the conditions of 80% fuel utilization, 40% oxygen utilization, and 0.6A / cm 2 current density, and the time variation of the output characteristics is shown in Table 5 below.

In addition, 100 g of the carbon separator of the 100th time was taken as a test piece and immersed in 2 L of water at pH 2 for 10 days at a temperature of 80 ℃, the concentration of ions in water was measured by the absorbance method. same.

division Open circuit voltage (V) Battery output of carbon separator according to driving time (KW) Metal Elution (wt%) 0 hours 1000 hours 2000 hours 3000 hours 4000 hours 5000 hours Fe Al Inventive Example 1 40 15.1 15.0 15.0 14.9 14.8 14.8 0.09 0.05 Comparative Example 1 33 15.2 14.7 14.1 13.6 12.9 12.2 0.27 0.43 Inventive Example 2 45 16.9 16.9 16.8 16.8 16.7 16.6 0.07 0.06 Comparative Example 2 38 16.9 16.4 15.9 15.4 14.7 14.1 0.22 0.07

In Table 5, the invention examples (1 to 2) satisfying the scope of the present invention maintained only about 14.8 KW (40 V x 370 A) and about 16.6 KW (45 V x 370 A) over 5000 hours. But the amount of metal eluted was also very small.

However, in the case of Comparative Example 1 in which the content of Fe and Al in the molding material powder was out of the range of the present invention, after 20 hours, about 20% of the original battery output was decreased, and the amount of metal eluted was also very high. Many.

In addition, in the case of Comparative Example 2 using a stainless mold, the battery output was reduced by about 17% of the initial battery output after 5000 hours, and the amount of metal eluted was also very high.

As described above, according to the present invention, a carbon separator for fuel cells having a low elution of metal ions and a high battery output can be provided by using a graphite, epoxy resin, and a hardener mixed powder having few metal impurities in the carbon separator.

Claims (2)

At least one epoxy resin selected from the group consisting of bisphenol type epoxy resins, novolac type epoxy resins, biphenyl type epoxy resins and biphenyl ether type epoxy resins: 7 to 22% by weight, acid anhydride curing agents, amine curing agents and phenols At least one curing agent selected from the group consisting of system-based curing agents: 0.3-16% by weight and the remaining graphite, wherein the average particle size of the epoxy resin, curing agent and graphite is 0.2-20 占 퐉, angle of repose is 15-30 °, Graphite is a carbon separator raw material containing not more than 0.20% by weight of Fe and not more than 0.20% by weight of Al, and At least one filler selected from the group consisting of silica, barium sulfate, alumina, magnesium oxide, calcium carbonate, mica, kaolin, bentonite and aluminum hydroxide, based on 100 parts by weight of the separator raw material: 0.03 to 0.1 parts by weight of fuel Carbon separator for battery. At least one epoxy resin selected from the group consisting of bisphenol type epoxy resins, novolac type epoxy resins, biphenyl type epoxy resins and biphenyl ether type epoxy resins: 7 to 22% by weight, acid anhydride curing agents, amine curing agents and phenols At least one curing agent selected from the group consisting of system-based curing agents: 0.3-16% by weight and the remaining graphite, wherein the average particle size of the epoxy resin, curing agent and graphite is 0.2-20 占 퐉, angle of repose is 15-30 °, Graphite is pulverized a carbon separator raw material containing not more than 0.20% by weight of Fe and not more than 0.20% by weight of Al; At least one filler selected from the group consisting of silica, barium sulfate, alumina, magnesium oxide, calcium carbonate, mica, kaolin, bentonite and aluminum hydroxide, based on 100 parts by weight of the finely divided carbon separator: 0.03 to 0.1 parts by weight Dry mixing and then pulverizing to prepare a molding material powder; At least one curing agent selected from the group consisting of an acid anhydride curing agent, an amine curing agent and a phenolic curing agent: 5-20 wt% and the remaining graphite, the graphite having 0.20 wt% or less Fe and 0.20 wt% Al At least one filler selected from the group consisting of silica, barium sulfate, alumina, magnesium oxide, calcium carbonate, mica, kaolin, bentonite and aluminum hydroxide, based on 100 parts by weight of the raw material for molding die containing : Filling the molding material powder in a molding die prepared by adding 0.03 ~ 0.1 parts by weight; And And manufacturing a carbon separator by applying a pressure of 500 to 1000 kg / cm 2 to a molding die filled with the molding material powder and maintaining the same at a temperature of 130 to 200 ° C. 2.