KR20160082407A - Seperator of dmfc - Google Patents

Abstract

The present invention relates to a separator for a direct methanol fuel cell, which forms gas channel between electrode layers by being stacked between membrane electrode assemblies (MEA) of a fuel cell, and comprises: a main body of a plate shape;and a current collector having a plurality of protrusions which are elastically connected to the electrode layers by being stacked on the main body and form gas channel, wherein the protrusions comprise: a protrusion unit connected to the electrode layers; and an opened unit formed on a position corresponding to a part which forms the protrusion unit.

Description

Separator for direct methanol fuel cell SEPERATOR OF DMFC

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator plate for a fuel cell, and more particularly, to a separator plate for a direct methanol fuel cell that can improve the performance of a fuel cell stack by employing a porous current collector.

Referring to FIG. 1, the direct methanol fuel cell includes a polymer electrolyte membrane 10 and an anode 12, which is a catalyst layer applied to both sides of the electrolyte membrane so that hydrogen and oxygen can react with each other. A gas diffusion layer (GDL) 16 and a gasket 18 are arranged in the outer portion of the cathode electrode 12 and the fuel electrode 14, And a separation plate 20 having a flow field formed therein for supplying fuel to the outside of the gas diffusion layer and discharging the water generated by the reaction is joined to form a unit cell.

After a plurality of such fuel cell units are stacked, an end plate 30 for fixing the configuration of each cell unit is coupled to the outermost side thereof.

The separator 20 supplies a fuel (hydrogen or reforming gas) and an oxidizing agent (oxygen or air) to the fuel cell electrodes 12 and 14 respectively and a flow path is formed to discharge water from the electrochemical reactant, (MEA) and the gas diffusion layer 16, and an electrical connection function with the adjacent unit cell. The separator plate 20 generally uses graphite material in the past to withstand a strong corrosive environment of the fuel cell. However, in recent years, a metal separator plate using a stainless steel having corrosion resistance has been applied in consideration of manufacturing cost and weight.

As shown in FIG. 2, the metal separator 20 is formed by pressing the channel 24 and the gas diffusion layer 16, through which the fuel or the oxidizer of the metal separator passes, And a land 22 to form a charge shape for smooth supply of reactants and discharge of the product.

In this general fuel cell cell structure, the land portion 22 of the separator plate 20 over-compresses the gas diffusion layer 16 in accordance with surface pressure concentration, and the carbon fibers of the gas diffusion layer 16 adhere to the electrolyte membrane 10 And the contact resistance is increased to generate a large amount of heat, so that the electrolyte membrane 10 can be prevented from being damaged due to the sticking of the electrolyte membrane 10 to the electrolyte membrane 10, And the contact portion between the land portion 22 and the gas diffusion layer becomes a portion where over-compression occurs with respect to the gas diffusion layer, so that the passages of the reaction gas and the generated water are not properly formed. The produced water dischargeability is lowered, and there is a disadvantage that the generated reaction area is reduced and the generated water that has not been discharged is frozen, adversely affecting cold rolling.

In order to solve this problem, US Patent Application Publication No. 2009/0155665 A1 discloses a structure in which a mesh or stepped collector is formed on a separator plate having a flat structure in order to improve the contact resistance of the gas diffusion layer and improve the gas diffusion property and reactivity And WO 03/061042 discloses a structure in which a diffusion layer of a mesh shape is bonded to a flat separator by a sintering process. Korean Patent Laid-Open Publication No. 2011-0062360 discloses a structure for inserting a mesh between a separator and a gas diffusion layer.

However, such conventional techniques have a disadvantage in that they are expensive due to insertion of a simple mesh or the like, and it is difficult to drastically improve electron movement between the separating plates.

US Published Patent US 2009/0155665 A1 (Jun. 18, 2009) WO 03/061042 A2 (Jul. 24, 2003) Korean Published Patent 2011-0062360 (June 10, 2011)

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a method of manufacturing a metal plate by using a porous stainless steel collector without using a separator plate having a linear metal- The present invention is to provide a separator for a fuel cell having a structure for increasing the electrical contact portion to reduce the internal resistance of the cell, to reduce the differential pressure of the fuel cell through prevention of the depression of the gas diffusion layer, and to improve the performance of the fuel cell stack.

In order to achieve the above object, a separator for a direct methanol fuel cell according to an embodiment of the present invention is a separator plate which is laminated between membrane electrode assemblies (MEAs) of fuel cells to form gas flow paths between electrode layers And a current collector laminated on the main body and having a plurality of protrusions elastically contacting the electrode layer and forming a gas flow path, wherein the protrusions have protrusions contacting the electrode layers and protrusions formed on the protrusions And an opening portion formed at a position corresponding to the portion.

The protrusion may be in the form of a circular or prismatic shape.

The separator may be laminated with a current collector-main body-collector and a thickness of 0.05 to 0.15 mm.

Wherein the current collector has a composition of C: 0.02 or less, C: not more than 0.02, Si: not more than 0.4, Mn: not more than 0.2, P: not more than 0.04, S: not more than 0.02, Cr: 25.0 to 32.0, Of not more than 0.5%, W: not more than 2.0%, La: not more than 1.0%, Zr: not more than 1.0%, B: 0.1% or less, and the balance of Fe and inevitably contained impurities. % Or less of a ferritic stainless steel containing at least one element selected from the group consisting of ferritic stainless steels.

According to the separator for a fuel cell according to the present invention, by using a porous stainless steel current collector without using a conventional separator having a channel portion and a land portion, the electrical contact portion is increased to reduce the internal resistance of the cell, It is possible to manufacture a separator for a fuel cell having a structure capable of reducing the fuel cell differential pressure through prevention of depression and improving the performance of the fuel cell stack.

Further, according to the embodiment of the present invention, by using a current collector made of a porous stainless steel having a plurality of contacts formed in place of the straight-line separator by the conventional press-molding method, the flow of electrons is improved to remarkably reduce the contact resistance There is an effect that can be done.

1 is a cross-sectional view showing a stacked unit cell of a general direct methanol fuel cell.
2 is a cross-sectional view of a unit cell of a conventional fuel cell to which a separator for a direct methanol fuel cell is applied.
3 is a cross-sectional view of a unit cell of a fuel cell to which a separator for a direct methanol fuel cell according to an embodiment of the present invention is applied.
4 is a photograph showing a current collector according to an embodiment of the present invention.
5 is a graph showing a change in contact pressure according to the contact pressure.
6 is a graph showing the performance test results of the fuel cell.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Hereinafter, a separator for a fuel cell according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

3 is a partial cross-sectional view of a fuel cell stack employing a separator for a fuel cell according to an embodiment of the present invention. 4 is a photograph showing a current collector of a separator plate for a fuel cell according to an embodiment of the present invention.

A separator plate 100 for a fuel cell according to an embodiment of the present invention is stacked between membrane electrode assemblies (MEAs) of a fuel cell to form a gas flow path between the electrode layers 12 and 14. [ This separator plate includes a plate-like main body 120 and a current collector 110.

The plate-shaped body 120 separates the reaction air electrode 12 and the fuel electrode 14, and it is preferable to use a material having a thickness of 0.1 mm or less and ensuring high corrosion resistance and high conductivity in a fuel cell environment. Generally, it can be manufactured as a metal thin plate, and it is particularly preferable to use a thin stainless steel plate. As the thin metal plate, it is possible to adopt a waterproof steel plate such as gold plating or the like, and it is also possible to use a non-metallic material having conductivity such as carbon instead of a thin plate made of metal.

The plate-shaped body 120 is formed in a substantially flat plate-like shape, and two gas inlet ports (not shown) and two gas outlet ports (not shown) are formed at corner portions thereof to provide a gas passage . The gas inlet can introduce the fuel gas or oxidant gas supplied from the outside of the fuel cell stack into the single cell while allowing the fuel gas or oxidant gas to flow to the other single cells stacked. The unreacted gas is discharged from the MEA to the outside and the unreacted gas is discharged from the other single cells stacked.

The current collector 110 includes protrusions that elastically contact the electrode layer and form gas flow paths. The protrusions include protrusions 111 that are in contact with the electrode layer and openings (not shown) that are formed at positions corresponding to the protrusions. 112).

The protruding portion 111 is formed by punching a hole in the form of a slot in the first planar current collector so that gas can be smoothly supplied to the channel channel. The structure in which the current collector 110 and the gas diffusion layer 16 are in contact with each other by the projections 111 formed on the plurality of projections ensures a low contact resistance at the time of fastening the fuel cell including the current collector 110 And it is possible to prevent the gas diffusion layer 16 from sinking. The open portion 112 is formed so that the gas flow path can be formed in the punched portion.

In addition, as the number of slot-shaped protrusions formed in the current collector is increased, the number of protrusions is increased, so that the electron flow can be improved and the contact resistance can be drastically reduced. The protrusions may be arranged at regular intervals on the surface of the current collector, and the protrusions 111 may be formed by zigzag for each column. The separator for a fuel cell according to an embodiment of the present invention may be arranged in the order of the collector 110, the main body 120, and the collector 110, and may be applied to the unit cell.

The thickness of the current collector 110 and the separator 120 should be 0.2 mm or less in order to reduce the weight of the stack, and preferably 0.05 mm to 0.15 mm in consideration of breakage occurring in forming the material. The current collector 110 has a protrusion 111 of a slot shape in the present invention and it is preferable that the size of the protrusion 111 is small and the interval is narrow for electrical contact and uniform gas diffusion.

In the separator for a fuel cell according to an embodiment of the present invention, the current collector or the flat plate-like body may contain not more than 0.02% C, not more than 0.02% N, not more than 0.4% Si, not more than 0.2% Mn, , Cu: not more than 0.04%, P: not more than 0.04%, S: not more than 0.02%, Cr: 25.0 to 32.0%, Cu: not more than 2.0%, Ni: not more than 0.8%, Ti: not more than 0.5% At least one element selected from the group consisting of V: not more than 1.5%, W: not more than 2.0%, La: not more than 1.0%, Zr: not more than 1.0%, and B: not more than 0.1% Ferritic stainless steels may be used. When a ferritic stainless steel having such a composition is used as a current collector, the corrosion resistance is excellent and the contact resistance can be lowered.

Hereinafter, the reason for limiting the component system of the ferritic stainless steel used for the collector of the separator or the flat plate-like body will be described in detail.

C and N form Cr carbonitride in the steel, and as a result, the corrosion resistance of the layer lacking Cr is lowered, so that the lower both elements are, the better. Therefore, in the present invention, the composition ratio of C is limited to 0.02% or less and N is limited to 0.02% or less.

Since Si inhibits elements effective in deoxidation, toughness and formability, the composition ratio of Si is limited to 0.4% or less in the present invention.

Mn is an element that increases deoxidation, but MnS, which is an inclusion, decreases the corrosion resistance. Therefore, the composition ratio of Mn is limited to 0.2% or less in the present invention.

P reduces not only the corrosion resistance but also the toughness, so that the composition ratio of P is limited to 0.04% or less in the present invention.

S forms MnS. Since MnS is a starting point of corrosion and reduces corrosion resistance, in the present invention, the composition ratio of S is limited to 0.02% or less.

Cr increases the corrosion resistance in the acidic atmosphere in which the fuel cell operates, but decreases the toughness. Therefore, in the present invention, the composition ratio of Cr is limited to 25.0 to 32.0%.

Mo plays a role in increasing the corrosion resistance in the operating environmental atmosphere, but is inferior in the effect of reducing the toughness and the economical efficiency in the case of excessive addition. Therefore, Mo is basically not added in the present invention. Thus, even when Mo is not added, the desired effect of the present invention can be obtained. However, it is also possible to add Mo additionally when corrosion resistance improvement is particularly required. In this case, the content thereof is preferably limited to a range of 5% or less.

Ni plays a role to reduce some contact resistance, but Ni addition and formability may be deteriorated when added excessively. In the present invention, the composition ratio of Ni is limited to 0.8% or less in consideration of this.

Since Ti and Nb lower the elements and toughness which are effective for forming C and N in the steel as carbonitride, Ti and Nb are limited to 0.5% or less in consideration of this.

V increases the corrosion resistance in the acidic atmosphere in which the fuel cell operates, but when the excess is added,

Can be degraded. Therefore, in the present invention, the composition ratio of V is limited to 1.5% or less.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

A current collector and a plate-like main body were manufactured using a stainless steel sheet having a thickness of 0.1 mm in the composition shown in the following Table 1. At this time, the current collector was formed in the shape as shown in FIG. 4 and an electrode effective area of 100 cm 2 was manufactured.

division C Si Mn P S Al Cr Ni Cu Ti Nb Mo Other N ingredient
(wt%) 0.004 0.124 0.121 <0.003 <0.003 0.037 30.10 0.12 - 0.051 0.24 - 0.4V 0.008

As a comparative example, the characteristics of the fuel cell were measured using a separator formed of a conventional channel and land.

5 is a graph showing a change in contact pressure according to the contact pressure. In the comparative example, the conventional separator was laminated twice, and the inventive example was a laminate of two current collectors and one separator. As a result of comparing the measured change in contact resistance, it was confirmed that the contact resistance of the separator according to the present invention is lowered due to an increase in electrical contact.

6 is a graph showing the performance test results of the direct methanol fuel cell. Pt / Cu (HISPEC 12100, Johnson Matthey) and Pt / C (HISPEC 13100, Johnson Matthey) were used as the catalysts for the anode and the cathode, respectively. The GDL of the anode and the cathode was prepared by using 5 wt% of PTFE treated with Toray TGP 060 (Toray Co., Japan) and 25BC (SGL, Germany) of carbon paper, respectively. The amount of Pt supported was 1.8 mg cm -2 for the anode and 1.6 mg cm -2 for the cathode, respectively. The performance of the unit cell was evaluated at 60 캜 by supplying 1 M aqueous methanol solution and air. The anode polarization was measured in a 1 M methanol aqueous solution and an atmosphere at 60 캜 as in the case of measuring the performance of a unit cell. As shown in FIG. 6, it can be confirmed from the slope of the voltage / current that the effect of reducing the internal resistance of the cell due to the reduction of the contact resistance of the separator due to the increase of the electrical contact part of the present invention.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

10: electrolyte membrane 12: air electrode
14: fuel electrode 16: gas diffusion layer
100: separator plate 110: collector
120: main body 111:
112:

Claims (4)

A separator plate which is laminated between membrane electrode assemblies (MEAs) of fuel cells and forms gas flow paths between electrode layers,
And a current collector laminated on the main body and having a plurality of protrusions elastically contacting the electrode layer and forming a gas flow path,
Wherein the projection includes a protrusion contacting the electrode layer and an opening formed at a position corresponding to a portion where the protrusion is formed.
The method according to claim 1,
Wherein the protrusions are circular or rectangular in shape.
The method according to claim 1,
Wherein the separator is laminated with a current collector, a main body and a current collector and has a thickness of 0.05 to 0.15 mm.
The method according to any one of claims 1 to 3,
Wherein the current collector has a composition of C: 0.02 or less, C: not more than 0.02, Si: not more than 0.4, Mn: not more than 0.2, P: not more than 0.04, S: not more than 0.02, Cr: 25.0 to 32.0, Or less, Ti: 0.5 or less, Nb: 0.5 or less, the balance Fe and inevitably contained impurities
At least one element selected from the group consisting of V: not more than 1.5%, W: not more than 2.0%, La: not more than 1.0%, Zr: not more than 1.0%, and B: not more than 0.1% &Lt; / RTI &gt; separator for a direct methanol fuel cell.

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