KR20100020050A - Mixture for manufacturing self-healing fuel cell bipolar plate and fuel cell bipolar plate - Google Patents

Abstract

PURPOSE: A mixture for manufacturing a self-healing fuel cell bipolar plate is provided to exhibit self-healing performance because a film material of microcapsule is dissolved by moisture, wet hydrogen, and methanol aqueous solution infiltrated through micro cracks. CONSTITUTION: A mixture for manufacturing a self-healing fuel cell bipolar plate consisting of highly conductive graphite powder, thermosetting resin, hardener and curing accelerator comprises a solid epoxy resin added with Grubbs catalyst, and microcapsules. The microcapsules comprise at least one kind of a membrane selected from urea resin and melamine resin.

Description

MIXTURE FOR MANUFACTURING SELF-HEALING FUEL CELL BIPOLAR PLATE AND FUEL CELL BIPOLAR PLATE}

The present invention relates to a mixed composition for producing a fuel cell separator and a fuel cell separator exhibiting self-healing performance, and in particular, a solid epoxy resin to which a Grubbs catalyst is added; Membrane is composed of at least one selected from urea resin, melamine resin, the core material is a microcapsule made of a curing agent for curing the solid-state epoxy resin; mixed composition for producing a fuel cell separator and fuel cell separator It is about.

A fuel cell is a power generator that directly converts fuel gas and oxygen into electrical energy by electrochemically reacting, and is a future clean energy source with high energy output density and energy conversion rate.

Among the fuel cell types, polymer electrolyte membrane-based fuel cells are used at relatively low temperatures of less than 150 ° C. Depending on the type of fuel used, proton exchange membrane (PEMFC) and liquid phases using hydrogen gas are used. It is divided into direct methanol fuel cell (DMFC) using methanol (aka methyl alcohol) as a fuel electrode.

PEMFC, which uses hydrogen as a fuel, has high energy density and is considered as a clean energy source for many applications as a future fuel cell for automobiles. Many problems remain with regard to handling. On the other hand, methanol-based fuel cells have a slightly lower energy density, but are easy to store and handle, and do not require additional fuel reforming devices, thereby simplifying and compacting the device process. Application is expected. Applications are being actively researched for information and communication products such as laptops, mobile phones, and small household electrical appliances, mobile and military battery packs such as golf carts, scooters, and wheelchairs, and rechargeable batteries used in secondary batteries.

The main components of such a fuel cell include an anode electrode supplied with reaction fuel, a cathode electrode supplied with oxygen or air, and a separator or bipolar plate for determining the flow of fuel and air. Polymer electrolyte membrane membranes (Nafion 112, 115 or 117, DuPont, USA), which allow only hydrogen ions to pass through, are mainly used. In the anode, a noble metal catalyst such as PtRu or Pt-Metal alloy catalyst is supported on various carbon carriers to form a catalyst layer together with a gas diffusion layer (GDL), where activated hydrogen ions pass through the electrolyte membrane and move to the cathode. In addition, the cathode also combines the activated oxygen and the transferred hydrogen ions in the same type of catalyst layer to generate water, the electricity generated by the electromotive force difference generated at this time.

On the other hand, the fuel cell separator serves to prevent the gas mixing between the unit cells of the fuel in the fuel cell configuration, to connect the electrical circuit, and to remove the reaction product and the residual gas, and the current collector. The fuel cell separator, which is one of the core materials connecting several unit cells, constitutes a stack, which is about 20-30% of the total manufacturing cost of a polymer fuel cell, and it is very important to reduce manufacturing costs. In addition, the graphite-based fuel cell separator has a problem in improving its performance due to its limitation in improving mechanical and electrical properties. However, the graphite-based fuel cell separator has been mainly used until now. I use it. On the other hand, the graphite fuel cell separator is very brittle and needs to be improved because there is a problem that cracks may occur due to impact during stack assembly or operation.

And electrical conductivity in the US Department of Energy (DOE) recommendation criteria for graphite fuel cell separators (FY 2007 reports for the DOE hydrogen program, V. Fuel cells-Bipolar plate p722-731):> 100 S / cm, Hydrogen permeability: <2x10-6 cm 3 / cm 2-sec, Corrosion rate: <1㎂ / ㎠, Raw material cost: ~ $ 4 / mW, manufacturing cost: <$ 6 / mW, among which electrical conductivity, hydrogen permeability, electricity Chemical corrosion is selected as an important item. Although there is no standard on the mechanical properties, previous studies require flexural strength of> 34 MPa or more, but since the graphite composite itself is a brittle material, breakage can be easily propagated due to distortion or cracking during the production of medium and large stacks.

In the meantime, the method of complexing carbon fiber or other reinforcing fiber as a composite material for high temperature and high strength aerospace materials has been announced (J. of the electrochemical society, 147 (11) 4083-4086 (2000)). It is difficult to apply the reinforcement method in the manufacturing process, and it is a situation to replace the brittleness and crack generation without a special repair method to date.

Specifically, if the microcracks of the fuel cell separator in the stack are produced during the fuel cell manufacturing and the stack operation at 60-120 ° C, the fuel cell performance may be reduced and the explosion of the stack may occur. When the stack is dismantled, the sealing gasket and the electrode-integrated electrolyte membrane (MEA) are damaged, so it is difficult to repair and replace the stack with a new one.

The present invention for solving such a conventional problem is that when the microcracks of the fuel cell separator in the stack occurs, the microcracks are freely healed, and there is no hassle of replacing the new stack with a huge cost. Mixed composition and fuel cell for manufacturing self-healing fuel cell separator that can be dissolved by water, wet hydrogen, wet air or methanol aqueous solution that can penetrate through microcracks even if the membrane of microcapsules for self-healing is not broken. The purpose is to provide a separator plate.

In the present invention for achieving the above object in the mixed composition for manufacturing a fuel cell separator comprising a highly conductive graphite powder, a thermosetting resin, a curing agent and a curing accelerator,

Solid epoxy resin to which Grubbs catalyst is added;

Membrane is made of at least one selected from urea resin, melamine resin, the core material is a microcapsule consisting of a curing agent for curing a solid epoxy resin; provides a mixed composition for producing a self-healing fuel cell separator. .

In particular, the curing agent contained in the microcapsules is preferably made of at least one selected from liquid amines and liquid dicyclopentadiene.

And the microcapsules are preferably mixed 0.1 to 10% by weight of the total weight.

In addition, the present invention provides a self-healing fuel cell separator, characterized in that manufactured using the mixed composition.

Hereinafter, the mixed composition for producing a self-healing fuel cell separator of the present invention will be described in detail.

The mixed composition for preparing a self-healing fuel cell separator of the present invention further includes a solid epoxy resin in which a Grubbs catalyst is added to a highly conductive graphite powder, a thermosetting resin, a curing agent, and a curing accelerator, and microcapsules. Since the highly conductive graphite powder, the thermosetting resin, the curing agent, and the curing accelerator in the above mixture composition are widely used to manufacture a fuel cell separator in the related art, a detailed description thereof will be omitted.

The microcapsules are made of at least one selected from urea resin and melamine resin, and the core material is composed of a curing agent for curing a solid epoxy resin.

The membrane of the microcapsule is made of at least one selected from urea resin and melamine resin, which are easily dissolved by water, wet hydrogen, wet air, or methanol aqueous solution infiltrated by the microcracks of the fuel cell separator. Since the membrane is made of urea resin or melamine resin, even though the membrane of the microcapsule is not broken by the microcracks of the fuel cell separator, the membrane dissolves in moisture, wet hydrogen, and the like, thereby exhibiting more significant self-healing performance. In addition, there is an advantage that does not need to use a water-deactivation agent as in the prior art.

The thickness of the film of the microcapsules is not easily broken by a weak impact, and may be a thickness that can be dissolved in a short time by moisture, wet hydrogen, or the like.

In addition, the core material of the microcapsules is composed of a curing agent in which a crosslinking reaction occurs by causing a ring-opening substitution polymerization reaction with a solid epoxy resin to which a Grubbs catalyst is added. It is preferable that a hardening | curing agent consists of 1 or more types chosen from liquid amine type and liquid type dicyclopentadiene.

The microcapsules are preferably mixed 0.1 to 10% by weight of the total weight. When the microcapsules are mixed at less than 0.1% by weight, self-healing does not occur smoothly. When the amount of the microcapsules is mixed at 10% by weight, high self-healing performance may be exhibited, but electrical characteristics such as electrical conductivity and strength may be deteriorated.

In addition, the solid epoxy resin to which the Grubbs catalyst is added may be used by mixing 5% excessively with respect to the curing agent equivalent ratio for sufficient reaction of the curing agent of the microcapsules.

Such a mixed composition of the present invention may be homogeneously mixed and then injected into a molding mold, and then compression molded to a molding pressure of 200 to 700 kg / cm 2 at a molding temperature of 160 to 190 ° C. to manufacture a fuel cell separator.

In the mixed composition for manufacturing a self-healing fuel cell separator of the present invention, microcracks are generated in the fuel cell separator due to impact or abnormal operation under a fuel cell operating temperature of 60-120 ° C., even if the membrane material of the microcapsules is not broken. Since the membrane material of the microcapsules is dissolved by the water, wet hydrogen, and methanol aqueous solution penetrated through, there is an effect that can exhibit a more significant self-healing performance.

In particular, in the case of fuel cells, when the microcracks occur in the separator, performance of the stack may be degraded. However, the stack may be difficult to repair by disassembling the stack. The development of mixed compositions containing microcapsules with properties is very important in terms of economics as well as technical aspects.

Hereinafter, the present invention will be described in more detail with reference to Examples. The scope of the present invention is not limited to the following Examples.

[Production of Microcapsules]

A small amount of alkali hydrolyzate of styrene maleic anhydride was first added to a 300 ml beaker as a surfactant, and 10 g of a dicyclopentadiene (DCPD) monomer for self-healing low viscosity was added little by little, followed by stirring with a high energy source ultrasonic mixer.

In the method of preparing a microcapsule membrane, an in situ polymerization method was selected among methods using an acid catalyst at a low temperature of 100 ° C. or lower. Here, In situ polymerization method is a prepolymer of methyl melamine was prepared by addition reaction of formaldehyde to melamine, wherein 3 mol of formaldehyde ratio was polymerized to 1 mol of melamine.

500 ml of distilled water was added to a 2,000 ml beaker with a high speed (2000 rpm) stirrer and emulsified by adding oil. After adding a low viscosity dicyclopentadiene monomer to a high speed rotating beaker, methylmelamine prepolymer was added, and the temperature was heated to 90 ° C. to prepare a microcapsules of dicyclopentadiene as a core material of melamine capsule membrane.

The particle size of the prepared microcapsules was 50 ~ 200㎛, the film thickness was 5 ~ 10㎛.

[Production of Mixed Composition for Manufacturing Fuel Cell Separator]

75 wt% of the highly conductive graphite powder, 4.85 wt% of the carbon nanotube, 15 wt% of the thermosetting epoxy resin, 5 wt% of the curing agent, and 0.15 wt% of TPP (Triphenyl phosphine) as the curing accelerator were mixed to obtain a graphite mixed powder. At this time, the high-conductive graphite powder was used a high-conductive graphite powder having an average particle size of 27 ~ 50㎛ size of Timcal Co., Switzerland, and CM-95 of ILJIN Nanotech Co., Ltd. was used as the carbon nanotube. -80XY, ARAKAWA Chemical, AMANOL 758 as a curing agent, and TPP of HOKKO Chemical were used as a curing accelerator.

The graphite mixed powder, the microcapsules prepared above, and the epoxy resin to which the Grubbs catalyst was added were mixed to prepare a mixed composition for preparing a fuel cell separator. At this time, the epoxy resin to which the Grubbs catalyst was added was excessively mixed with 5% of the equivalent ratio of dicyclopentadiene, the core material of the microcapsules.

In addition, the microcapsules were mixed with 0.1 wt%, 1.0 wt%, 5.0 wt%, and 10.0 wt%, respectively, based on the total weight, to prepare the mixed compositions of Examples 1 to 4.

Hot press equipment after adding the mixed composition of Examples 1 to 4 and the graphite mixed powder, in which the epoxy resin content to which the microcapsule and Grubbs catalyst was added, were mixed into the molding mold having the cavity portion of 50 × 50 × 2mm, respectively. (Carver 25ton, manual) was molded for 40 minutes under the conditions of molding temperature 170 ~ 190 ℃, molding pressure 300 ~ 500kg / ㎠ to obtain a separator for a fuel cell.

Three-point flexural strength was measured by the test method of ASTM D790 for the fuel cell separators of Examples 1-4 and Comparative Example, and the fuel cells of Examples 1-4 and Comparative Example were used to determine the self-healing characteristics after the 3-point flexural strength measurement. The separators were immersed in an aqueous solution of 1 mol of 80 ° C. MeOH for 2 days, and then dried to measure the 3-point flexural strength, and the results are shown in Table 1 below.

[Table 1] Bending strength measurement results of separator plates for fuel cells of Examples 1 to 4 and Comparative Examples

Example 1 Example 2 Example 3 Example 4 Comparative example Microcapsule Combination Ratio (wt%) 0.1 1.0 5.0 10.0 0.0 Initial strength (MPa) 51.7 51.6 51.5 50.8 52.0 MeOH strength after immersion (MPa) 7.0 10.4 13.5 13.1 2.3

As shown in Table 1, the bending sensitivity measured after immersion in a 1 mole aqueous solution of MeOH was 2.3 MPa in the comparative example, whereas in Examples 1 to 4, 7.0 MPa or more, and the flexural strength was more than three times higher than the comparative example. , As a result, in the case of Examples 1 to 4 it was confirmed that the flexural strength is restored.

Claims (4)

In the mixed composition for manufacturing a fuel cell separator comprising a high conductive graphite powder, a thermosetting resin, a curing agent and a curing accelerator, Solid epoxy resin to which Grubbs catalyst is added; Membrane is composed of at least one selected from urea resin, melamine resin, the core material is a microcapsule consisting of a curing agent for curing a solid epoxy resin; Self-healing fuel cell separator manufacturing composition comprising a. The method of claim 1, wherein the curing agent as the core material of the microcapsules is a mixed composition for producing a self-healing fuel cell separator, characterized in that consisting of at least one selected from liquid amine-based, liquid dicyclopentadiene. According to claim 1, wherein the microcapsules are mixed composition for producing a self-healing fuel cell separator, characterized in that 0.1 to 10% by weight of the total weight is mixed. Self-healing fuel cell separator, characterized in that prepared using the mixed composition of any one of claims 1 to 3.