WO2003044889A1

WO2003044889A1 - Metal structure plate for fuel cell

Info

Publication number: WO2003044889A1
Application number: PCT/KR2001/002273
Authority: WO
Inventors: Jun-Bom Kim; Young-Mo Goo
Original assignee: Kuk Il Inntot Ltd.; Ulsan Industrial Education Foundation
Priority date: 2001-11-21
Filing date: 2001-12-27
Publication date: 2003-05-30
Also published as: AU2002219645A1; KR20030042179A

Abstract

Disclosed is a metal structure plate in which filler is impregnated and that has flow channels. A bipolar plate is manufactured by the steps of: manufacturing a metal structure in a sponge type or a crosslinked type by processing metal material; increasing hardness and density of the metal structure by pressurizing the metal structure; impregnating filler into the metal structure through a brushing method or a rolling method or injection molding and drying the metal structure; and cutting or pressing the dried plate. The metal structure bipolar plate can satisfy various physical properties required in the bipolar plate by changing the composition of the filler to be impregnated.

Description

Metal Structure Plate for Fuel Cell

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a fuel cell capable of directly converting the chemical energy of fuel into electric energy through electrochemical reaction. More particularly, the present invention relates to a bipolar plate capable of providing gas to a membrane and electrode assembly(MEA) formed of a polymer electrolyte membrane and a porous electrode. Background Art

A fuel cell is used for generating direct current power and there are solid oxide fuel cell(SOFC), molten carbonate fuel cell(MCFC), phosphoric acid fuel cell(PAFC), proton exchange membrane fuel cell(PEMFC), and direct methanol fuel cell(DMFC).

The optimal operation temperature for the fuel cells are about 1000°C for solid oxide

fuel cell, about 650 ^°C for the molten carbonate fuel cell, about 200 °C for the

phosphoric acid fuel cell, and about 80 °C for the proton exchange membrane fuel cell.

The proton exchange membrane fuel cell(PEMFC) is also called a polymer electrolyte membrane(PEM) method because it is made of polymer electrolyte.

Because the operation temperature of the PEMFC is about 80 °C, has high energy

density and efficiency, it can promptly start and stop by changing output according to required power, and adopts an environmentally friendly power generating method. In general, the PEMFC consists of a membrane and electrode assembly(MEA) and a supporter of conductive material, which is overlapped on both sides of the MEN, and is used in the form of unit cells piled on one another. In particular, for the fuel cell in which the unit cells are continuously connected and piled, a part that electrically connects between the cells and blocks supplied gas from being mixed with each other inside the cells is called a bipolar plate.

A flow channel is formed inside the plate to allow flow of fluid(material, which can generate electric power through electrochemical reaction, such as hydrogen, methanol, oxygen or air) into the fuel cell. In particular, a plate having flow channels formed on both sides of the plate that allow fuel fluid to flow on a side surface and oxidizer fluid to flow on the other side surface is called a bipolar plate.

The bipolar plate serves as the supporter and a bulkhead for the membrane and electrode assembly and as an electric connector between the unit cells. Furthermore, the bipolar plate provides fluid to an electrode surface uniformly, distributes flow of cooling fluid and reaction gas smoothly, and effectively discharges water generated at a cathode electrode surface together with discharged gas such as air or oxygen. Moreover, the bipolar plate serves to separate fluid between the unit cells electrically connected.

The bipolar plate for the PEMFC must have conductivity, good mechanical strength, thermal stability, high resistance to corrosive substances, and low permeability to gas.

The bipolar plate of the fuel cell has a complex flow channel structure in order to pass fluid and/or by-products. As material for the bipolar plate having the flow channels, graphite, which has excellent corrosion resistance and conductivity, has been used. However, graphite is brittle and it is difficult in mechanical processes to level the surface and to form a gas flow channel which result in increased manufacturing cost. The graphite bipolar plate has been widely used because of the good electrochemical stability and high electric and thermal conductivity of graphite. However, because the graphite bipolar plate requires a CNC(Computer Numerical Control) system using numerical control program for forming the flow channels, the manufacturing cost is increased. Recently, a composite type bipolar plate has been manufactured by a press method resulting in reduced manufacturing cost. However, the composite type bipolar plate has lower conductivity compared with the graphite bipolar plate. The composite type bipolar plate having low conductivity has low power density per unit volume, and thereby, it is difficult to operate at high electric power.

Therefore, a novel bipolar plate, which can overcome the negative effect on conductivity associated with the composite type bipolar plate and high manufacturing cost, is still required.

Applying stainless steel as substitute material for the graphite material for the purpose of reducing the manufacturing cost has been reported. Japanese patent laid- open No. 10-228914 discloses a bipolar plate for fuel cell, which is made of metal materials and directly plated with gold on a surface in contact with the electrode. As metal materials, stainless steel, aluminum and nickel-steel alloy can be used. In Japanese patent laid-open No. 10-228914, SUS 304 was used as stainless steel. The bipolar plate is low in contact resistance between the bipolar plate and the electrode because of the gold plating. Therefore, output power of the fuel cell can be increased, because electric conductivity from the bipolar plate to the electrode is high. However, the prior art has several problems such as increased manufacturing cost due to the gold plating and increased material cost in the case where a plate is manufactured over a prescribed thickness to keep the mechanical strength of the alloy with a strong corrosion resistance. Additionally, U.S. patent Nos. 3,801,374, 4,214,969 and 4,988,583 respectively disclose a bipolar plate, which is compressively molded by mixing with a fluoropolymer bonding agent such as vinylidene fluoride. However, fluoropolymer has a problem in that it has a low conductivity and restriction as an effective bonding agent when being molded, because it has high viscosity compared with other polymer materials.

A portion of this invention was disclosed in "1st European PEFC Forum", Proceedings, p.211, Lucerne, Switzerland published in July 2, 2001, the content of which is incorporated hereinto by reference.

Summary of The Invention

Accordingly, the present invention is directed to a metal structure plate for fuel cell that substantially obviates one or more problems due to limitations and disadvantages of the related art. Therefore, it is an object of the present invention to provide a novel bipolar plate and cooling plate capable of providing a good performance and productivity. The present invention provides a novel bipolar plate and cooling plate by using metal foam as a backbone and an impregnating filler such as a carbon or polymer material into the pores. To achieve the above objects, the present invention provides a metal structure plate in which filler is impregnated and one or more flow channels are formed in a metal structure.

In one aspect, the present invention provides a metal structure bipolar plate in which filler is impregnated in a metal structure and one or more flow channels are formed at both sides.

In another aspect, the present invention provides a stack of metal structure plates in which filler is impregnated and one or more flow channels are formed in a metal structure. In a further aspect, the present invention provides a method for manufacturing a metal structure plate including the steps of: forming one or more flow channels on a metal structure through pressing or cutting; and obtaining a metal structure plate by impregnating filler into the metal structure having one or more flow channels.

In another aspect, the present invention provides a method for manufacturing a metal structure plate including the steps of: impregnating filler into a metal structure; and obtaining a metal structure plate by forming one or more flow channels on the metal structure, in which the filler is impregnated, through pressing or cutting or injection molding.

In another aspect, the present invention provides a method for manufacturing a metal structure bipolar plate including the steps of: forming one or more flow channels on both sides of the metal structure through pressing or cutting; and obtaining a metal structure plate by impregnating filler into the metal structure having one or more flow channels.

In another aspect, the present invention provides a method for manufacturing a metal structure bipolar plate including the steps of: impregnating filler into a metal structure; and obtaining a metal structure plate by forming one or more flow channels on both sides of the metal structure, in which the filler is impregnated, through pressing or cutting or injection molding. In another aspect, the present invention provides a method for manufacturing metal structure bipolar plate including the steps of: dividing a metal structure into three parts and compressing the right and left parts of the metal structures; impregnating filler into the right and left parts of the metal structures with the exception of the central part of the metal structure and a reaction area; forming one or more flow channels in the central part of the metal structure through pressing or cutting; and obtaining a metal structure bipolar plate by bonding one of the right and left parts of the metal structures on top of the central part of the metal structure having one or more flow channels and bonding the other of the right and left parts of the metal structures under the central part of the metal structure having one or more flow channels. In another aspect, the present invention provides a method for manufacturing a metal structure cooling plate in which filler is impregnated in a metal structure and which has one or more cooling water channels.

In another aspect, the present invention provides a stack of metal structure cooling plates in which filler is impregnated in a metal structure and which has one or more cooling water channels.

In another aspect, the present invention provides a metal structure cooling bipolar plate, which has a part of a metal structure in which filler is impregnated, and one or more cooling water channels are formed at both sides of the metal structure in which the filler is impregnated, and the other part of the metal structure, in which filler is not impregnated, is exposed to the ambient air.

In a still further aspect, the present invention provides a method for manufacturing a metal structure plate including the steps of: forming one or more flow channels or one or more cooling water channels on a metal structure through pressing or cutting; and obtaining a metal structure plate or a cooling plate by impregnating filler into the metal structure having one or more flow channels or one or more cooling water channels.

Brief Description of the Drawings

Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawing in which: FIG. 1 illustrates a flow chart of a manufacturing process of a metal structure plate according to the present invention;

FIG. 2 illustrates a front view of the metal structure plate manufactured according to the present invention;

FIG. 3 illustrates a front view of a nickel structure plate in which one sheet of nickel structure according to the present invention is applied to a stack;

FIG. 4 illustrates a bipolar plate manufactured according to the present invention;

FIG. 5 illustrates a side view of a unit cell manufactured by using the nickel structure plate; FIG. 6 illustrates a side view of a stack manufactured by using the nickel structure plate used in the stack;

FIG. 7 illustrates a front view of the nickel structure plate for manufacturing a nickel structure bipolar plate; FIG. 8 illustrates a side view of a stack manufactured by using the bipolar plate according to the present invention;

FIG. 9 illustrates a manufacturing process of the nickel structure bipolar plate by using one nickel structure;

FIG. 10 illustrates a front view of nickel structure plates which are applied to a stack requiring low voltage and high current;

FIG. 11 illustrates a view of a structure of the stack manufactured using the nickel structure plate requiring low voltage and high current;

FIG. 12 illustrates a side view of the stack manufactured using the nickel structure plate applied to the stack requiring low voltage and high current; FIG. 13 illustrates a nickel structure cooling plate manufactured by a method according to the present invention;

FIG. 14 illustrates another nickel structure cooling plate manufactured by a method according to the present invention;

FIG. 15 illustrates a side view of a stack consisting of the nickel structure cooling plate manufactured by a method according to the present invention;

FIG. 16 illustrates a nickel structure cooling bipolar plate manufactured by a method according to the present invention;

FIG. 17 illustrates a side view of a stack consisting of the nickel structure cooling bipolar plate manufactured by a method according to the present invention; FIG. 18 illustrates a graph showing potential difference per current density of various types of nickel structure bipolar plates;

FIG. 19 illustrates a comparative graph of the nickel structure plate and the graphite structure plate in operation; and FIG. 20 illustrates a graph showing potential difference according to temperature and current density of a fuel cell.

Detailed Description of the Invention

The present invention will now be described in detail in connection with preferred embodiments with reference to the accompanying drawings.

A unit cell consists of an electrode, an electrolyte layer, a plate/bipolar plate and a current collector. A structure of a stack in which such unit cells are piled up can be mainly divided into a porous plate structure and a non-porous plate structure according to the type of the unit cell. The non-porous plate serves as a flow channel and a separation plate of reactive gas because of its delicate inner structure. The porous plate uses a separation plate, different from the porous plate serving to perform gas distribution.

Porous plates as well as bipolar plates can be used as plates according to the present invention.

A metal structure used as a supporter in the plate of the present invention may be made of metal materials, such as iron, nickel, chrome, silicon, tin, manganese, copper, magnesium or aluminum. Furthermore, the metal structure may be made of alloys of the above metal materials or combination of at least one of the above metal materials with other materials. Preferably, nickel or a nickel alloy can be used. The metal structure of the bipolar plate according to the present invention serves to increase electric and thermal conductivity, and thereby, the stack of the cell using the bipolar plate may also be cooled with air. It is preferable to manufacture the metal structure in a foam type, a crosslinked type, a lattice type, a fiber type or a powder type.

In the plate of the present invention, it is preferable that the metal structure has a porosity over 70% in order to reduce material cost. The porosity may be changed according to an impregnated amount of filler, and more preferably, the porosity may be more than 90%. If the porosity is less than 70%, the impregnated rate of the filler may be lowered and a pressurizing process of the plate may be omitted because of its good mechanical strength. Pores inside the metal structure improve permeability of gas and thermal conductivity. Furthermore, the pores according to the present invention have an influence on the cooling efficiency of the plate. The plates having pores have higher cooling efficiency, compared with other plates, which do not have pores. In consideration of the above parameters, the porosity of the metal structure may be properly changed according to the use of the plate.

To increase the conductivity of the plate used in a fuel cell, it is preferable to lower the porosity of the metal structure or impregnate filler having good conductivity. The filler may be a conductive polymer, a non-conductive polymer, graphite or silicone, and other materials, which can prevent leakage of gas.

As conductive polymers, polyphenylene sulfide(PPS), liquid crystal polymer LCP), polyphenylene oxide and its derivatives can be used. More particularly, conductive polymer composites may be manufactured and used by mixing polyaniline or polyethylene deoxythiophene with a water soluble resin such as polystyrene sulphonate or polyacrylic acid. Moreover, polytetramethylenoxide, polyhexamethylenoxide, n-propyl poly(meta)acrylate, isopropyl poly(meta)acrylate, n- butyl poly(meta)acrylate, isobutyl poly(meta)acrylate, sec-butyl poly(meta)acrylate, tert-butyl poly(meta)acrylate, n-hexyl poly(meta)acrylate, cyclohexyl poly(meta)acrylate, n-octyl poly(meta)acrylate, isooctyl poly(meta)acrylate, 2- ethylhexyl poly(meta)acrylate, decyl poly(meta)acrylate, lauryl poly(meta)acrylate, isononyl poly(meta)acrylate, isoboronyl poly(meta)acrylate, polyacryl such as benzyl poly(meta)acrylate polymetaacrylic acid, polyethylenedioxythiophene, polypyrrole, polyaniline may be used alone, or a copolymer or mixture of them may be used. Meanwhile, it is preferable to consider low cost, convenience in use and chemical and thermal stability in selecting the conductive polymer.

For the non-conductive polymer, silicone may be used.

As graphite, graphite fiber (carbon fiber) and graphite can be used, and also, conductive fiber, metal fiber, metal powder, polymer and metal composite material may be used.

For impregnation of the filler into the metal structure, polymer materials may be mixed to increase heat resistance and corrosion resistance, and the mixing ratio may be adjusted according to the property desired. Any method for preventing leakage of gas such as a brushing method or a rolling method may be used for impregnation of the filler into the metal structure if the impregnated filler has the effect of preventing the leakage of gas.

Referring to FIG. 1, a manufacturing method of the plate according to the present invention includes the steps of: i) processing metal material having high conductivity to manufacture a metal structure of a sponge type, a crosslinked type, a lattice type, a fiber type or a powder type; ii) increasing hardness and density of the metal structure by applying pressure to the metal structure; iii) impregnating the filler into the manufactured metal structure through the brushing method or the rolling method or injection molding method; iv) drying the metal structure, in which the filler is impregnated, at the

temperature of 90-110°C for 20-40 minutes;

v) forming one or more flow channels inducing flow of fuel and gas on channel surface of the metal structure, in which the filler is impregnated, through a cutting method or a pressing method; vi) treating the surface of the metal structure, on which one or more flow channels are formed, with solvent; and vii) assembling a cell using two metal structures which were surface- treated. In the manufacturing method of the plate according to the present invention, steps iii) and iv) may be performed after step v) according to the hardness of the filler. For example, if the impregnated filler is soft, one or more flow channels can be formed on the metal structure after the impregnated filler has been dried. On the other hand, if the filler is hard, the filler is impregnated and dried after step v) of forming one or more flow channels on the metal structure. In step vii), assembly pressure is about 10- 50Kg_f/cm². Organic solvent used in step vi) may be toluene, benzene or acetone, and toluene is preferred.

The formation of one or more flow channels and the cell of the metal structure, bipolar plate, cooling plate and cooling bipolar plate will be described in more details as follows.

FIG. 2 illustrates a front view of the metal structure plate manufactured by a method according to the present invention, and FIG. 3 illustrates a front view of a nickel structure plate that is one nickel structure of the present invention to be applied to a stack. As shown in FIGS. 2 and 3, the metal structure 1 and the metal structure plate 2 according to the present invention respectively have a flow channel 20 providing a fluid flow path formed at a side thereof, an anode side gas inlet 18 for inducing fluid to a side of the contour of the flow channel 20 of the metal structure plate 2 and an anode side gas outlet 12 formed at a lower end of a diagonal side opposed to the anode side gas inlet 18 for discharging gas. Meanwhile, the metal structure plate 2 includes a cathode side gas inlet 10 having a path for inducing fluid to a side of the contour of the flow channel 20 and a cathode side gas outlet 16 formed at a diagonal side opposed to the cathode side gas inlet 10 for discharging gas, which passes the flow channel 20. The metal plate 2 has a cooling water inlet 8 at the side of the upper end of thereof for cooling heat generated by the chemical reaction of hydrogen and oxygen and a cooling water outlet 14 at the other side opposed to the cooling water inlet 8 for discharging the cooling water.

Furthermore, another metal structure 3 having a structure similar to the metal structure 1 and another metal structure plate 4 having the similar structure as the metal structure plate 2 respectively have a wire connector 22 disposed at the side of the upper end thereof to provide a wire which serves as flow path of electricity generated in the unit cell.

As shown in FIG. 4, on the basis of the line A- A, a front surface of a bipolar plate 24 is located at the left side, a rear surface of the bipolar plate 24 is located at the right side, and the front and rear surfaces of the bipolar plates are connected with each other on the basis of the line A- . The front and rear surfaces of the bipolar plate have flow channels 38 respectively, which are symmetric to each other, for providing a path for flow of fluid. Each flow channel 38 has an anode side gas inlet 36 formed at a side of the contour of the flow channel 38 for inducing fluid into the flow channel 38 and an anode side gas outlet 30 formed at a diagonal side opposed to the anode side gas inlet 36. Meanwhile, the flow channel 38 includes a cathode side gas inlet 28 formed at a side of the contour of the flow channel 38 for inducing fluid into the flow channel 38 and a cathode side gas outlet 34 formed at a diagonal side opposed to the cathode side gas inlet 28 for discharging fluid, which passes the flow channel 38. Meanwhile, the front and rear surfaces of the bipolar plate 24 respectively have a cooling water inlet 26 at the side of the upper end thereof for cooling heat generated by chemical reaction of hydrogen and oxygen and a cooling water outlet 32 at the other side opposed to the cooling water inlet 26 for discharging the cooling water. The bipolar plate 24 can have a wire connector 22 disposed at an upper end thereof to provide a wire, which serves as a flow path of electricity generated in the unit cell, by extending the metal structure like plates 2 and 4.

Such metal structure plates 2 and 4 are manufactured as a metal structure cooling plate according to the formation of one or more flow channels or a cooling bipolar plate 64 by adding another metal structure in which the filler is not impregnated into the bipolar plate 24. Therefore, as shown in FIG. 13, the metal structure cooling plate 48 is manufactured in such a manner that a cooling water channel 66 extends from the cooling water inlet 8, which has the same structure as the metal structure plates 2 and 4 and induces cooling water, to the cooling water outlet 14 for discharging cooling water.

Meanwhile, FIG. 16 illustrates an example of the cooling bipolar plate 64. In FIG. 16, on the basis of the line B-B', a front surface of a cooling bipolar plate 64 is located at the left side, a rear surface of the bipolar plate 64 is located at the right side, and the front and rear surfaces of the bipolar plates are connected with each other on the basis of the line B-B'. The cooling bipolar plate 64 has the same fundamental structure as the bipolar plate 24, but has another metal structure, in which the filler is not impregnated, at a side of a lower end thereof Therefore, the metal structure, in which the filler is not impregnated, is contacted with the ambient air, thereby cooling the heat of reaction generated from the cell.

FIG. 17 illustrates a view of a structure of a stack to which the above-described cooling bipolar plate 64 is applied. As shown in the drawing, if the stack is manufactured using the cooling bipolar plate 64, a stack, which does not require the cooling plate 48 of FIG. 8, may be manufactured. Through the above structure, without the cooling plate 48 required for keeping temperature of the stack in a proper level, parts of the metal structure, in which the filler of the cooling bipolar plate 64 is not impregnated, can act as cooling fins.

The unit cell may be formed by one or more of the metal structure plates manufactured as above. If the stack is formed using the metal structure plate, the bipolar plate may be manufactured using the metal structure or the stack may be formed by the bipolar plate manufactured by a method in which two metal structures are bonded and compressed on the right and left sides of the bipolar plate. Another alternative for manufacturing the bipolar plate, the bipolar plate may be manufactured in such a manner that the metal structure is wrapped around the bipolar plate.

Hereinafter, the present invention will be described in more details referring to preferred examples. However, the following examples are only detailed examples of the present invention and do not restrict the scope of the present invention.

Example 1

The manufacture of a nickel structure plate using a soft filler The nickel structure (porosity of 95% or more, 600g/m², thickness of 2mm, Inco Technical Services Limited) was cut into size of 7cm x 7cm and compressed into thickness of 1mm at a pressure lMT(metric ton) to increase surface conductivity. To prevent leakage of gas, the nickel structure was filled with soft filler of 5.4g and the filler was impregnated by a rolling method. Here, the filler used was silicone liquid type gasket manufactured by the VALQUA company. The plate in which the filler was impregnated was dried in an oven at the temperature of 100°C for 30 minutes, and

then, a flow channel was formed on the plate through a pressing method. The manufactured flow channel had a width of 2mm and a depth of 1mm. After that, the surface of the plate having the flow channel was treated with toluene, and thereby, the plate was manufactured. The filler that might have remained on the surface of the plate was removed by brushing the surface of the plate with a brush dipped into toluene. Example 2

The manufacture of a nickel structure plate using a hard filler A nickel structure plate was manufactured in the same way as Example I, except that a flow channel was formed after the nickel structure was compressed. The hard filler, 5.4g of silicone, was impregnated into the nickel structure plate having the flow channel, and then, the nickel structure plate was dried in the oven at 100^°C for 30

minutes. Here, the filler was silicone hardened at high temperature and in a rigid state, which did not have elasticity and softness. Meanwhile, the surface of the dried nickel structure plate was treated with toluene, and thereby the plate was manufactured. The manufactured nickel structure plate 1 was in the same form as FIG. 2(a).

Example 3

The manufacture of a unit cell using nickel structure plate As shown in FIG. 5, a unit cell was manufactured using the nickel structure plate manufactured by Example 1.

As shown in the drawing, in order to prevent leakage of gas between a membrane and electrode assembly 46 and nickel structure plates 1 and 1', gaskets 43 were located at the right and left sides of the membrane and electrode assembly 46. The nickel structure plate 1 having anode polarity was located at a left side of the gasket and the nickel structure plate 1' having cathode polarity was located at the right side of the gasket 43. To prevent leakage of fluid flowing through a flow channel 20 formed inside the nickel structure plates 1 and 1' respectively having anode and cathode polarities, conductive plates 44 manufactured with conductive material were mounted on the right and left sides of the nickel structure plates 1 and 1'. An anode side current collector 42 was located on the left side of the conductive plate 44 and a cathode side current collector 42' was located on the right side of the conductive plate 44'. The above described components were piled up between an anode side end plate 40 and a cathode side end plate 40'.

Example 4

The manufacture of a nickel structure plate with wire connector A nickel structure plate 3 was manufactured in the same way as Example 1, and a wire connector was disposed at an upper end, and thereby current collectors were not needed when a unit cell was manufactured.

The manufactured nickel structure plate 3 had the same form as FIG. 2(b).

Example 5

The manufacture of a unit cell using nickel structure plate with wire connector A unit cell was manufactured in the same structure as Example 3 using the nickel structure plate 3 manufactured in Example 4. At this time, the anode side current collector 42 and the cathode side current collector 42' were removed.

Example 6 The manufacture of a nickel structure plate used in a stack using one sheet of nickel structure

A nickel structure plate was manufactured in the same way as Example 1. The nickel structure plate included an anode side gas inlet 18, an anode side gas outlet 12, a cathode side gas inlet 10, a cathode side gas outlet 16, a cooling water inlet 8, a cooling water outlet 14 and a wire connector 22 as well as a flow channel 20.

The manufactured nickel structure plate had the same form as FIG. 3.

Example 7 The manufacture of a stack using nickel structure plates used in the stack

A stack having the structure of FIG. 6 was manufactured using the nickel structure plate manufactured according to Example 6.

To form an exterior form of the stack, an anode side end plate 40 was disposed at a left side end of the stack and a cathode side end plate 40' was disposed at a right side end of the stack. A membrane and electrode assembly 46 was disposed between the anode nickel structure plate 2 and the cathode nickel structure plate 2' inside the stack. On the contour of the nickel structure plates 2 and 2' located at the right and left sides of the membrane and electrode assembly 46, a plate 44 for preventing leakage of gas or a cooling plate 48 for cooling the heat of reaction generated from the membrane and electrode assembly 46 were disposed. Here, the anode nickel structure plate 2 and the cathode nickel structure plate 2' were all manufactured in the same manufacturing method and composition, and the polarity thereof could be changed according to their position. A plurality of unit cells having the above structure were piled up around the membrane electrode assembly 46, thereby forming one stack. A wire connector 22 was disposed at the anode side end and the cathode side end of the piled unit cells, i.e. on the nickel structure plates 4 and 4' adjacent to the end plates 40 and 40', thereby collecting electricity generated from cell.

Example 8 The manufacture of a nickel structure plate used in stacks using two sheets of nickel structures

As shown in FIG. 7, a nickel structure of size of 7cm x 7cm(porosity of 95% or more, 600g/m², thickness of 2mm, Inco Technical Services Limited) was compressed at 3MT In the reaction surface, anode and cathode side gas inlets 10 and 18, anode and cathode side gas outlets 12 and 16 and cooling water inlet and outlet 8 and 14 were formed in the size of 0.5cm x 1cm through a cutting method. After that, except the reaction surface 52, filler was impregnated into all the above components to prevent leakage of gas. The nickel structure in which the filler was impregnated was dried in

the oven at temperature of 100 °C for 30 minutes. The nickel structure was bonded on

the nickel structure plate manufactured according to Example 3, and thereby the nickel structure plate, which will be used when the stack is manufactured, was manufactured

Example 9 The manufacture of a nickel structure bipolar plate

The nickel structure (porosity of 95% or more, 600g/m², thickness of 2mm, Inco Technical Services Limited) was made in the size of 7cm x 7cm and compressed at a pressure of 3MT to increase surface conductivity. To prevent leakage of gas, the nickel structure was filled with 5.4g of filler and impregnated through the rolling method. Here, the filler used was silicone liquid type gasket manufactured by the VALQUA company. The plate in which the filler was impregnated was dried in the oven at a temperature of 100°C for 30 minutes, and then, flow channels were formed

on front and rear surfaces of the plate through the pressing method. At this time, the manufactured flow channels were 2mm in width and 0.8mm in depth. The surface of the bipolar plate having the flow channels was treated with toluene, thereby manufacturing the nickel structure bipolar plate.

The manufactured nickel structure bipolar plate is shown in FIG. 4.

Example 10

The manufacture of a stack using nickel structure bipolar plate A stack was manufactured as shown in FIG. 8 using the nickel structure bipolar plate manufactured according to Example 9.

To form an exterior form of the stack, an anode side end plate 40 was disposed at a left side end of the stack and a cathode side end plate 40' was disposed at a right side end of the stack. Membrane and electrode assemblies 46 were disposed at the right and left of the nickel structure bipolar plate 24 inside the stack. A nickel structure plate 2 was disposed at a side opposed to a side of the membrane and electrode assembly 46, which was adjacent to the nickel structure bipolar plate 24. A cooling plate 48 was located between the nickel structure plate 2, which was adjacent to the membrane and electrode assembly 46, thereby preventing temperature rise of the stack due to the exothermic reaction.

The nickel structure bipolar plate 24 was contacted with the membrane and electrode assemblies 46 at both sides thereof. The nickel structure plate 2 having the flow channel formed at one surface was contacted with the membrane and electrode assembly 46 at the surface on which the flow channel was formed, and contacted with the cooling plate 48 at the other surface. On the contour of the nickel structure plates 2 and 4 located at the right and left of the membrane and electrode assembly 46, the conductive plate 44 for preventing leakage of gas or the cooling plate 48 for cooling the heat of reaction generated from the membrane and electrode assembly 46 were disposed.

Such a stack was similar to the stack manufactured using the nickel structure plate according to Example 7, but did not require the conductive plate 44 for preventing leakage of gas. In Example 7, two nickel structure plates 2 and 4 were required in a single fuel cell to use the nickel structure plates 2 and 4 on the stack. However, the nickel structure bipolar plate 24 according to this example serves the role of two nickel structure plates.

Example 11

The manufacture of a bipolar plate using two sheets of nickel structures Two sheets of nickel structures having a size of 7cm x 7cm(porosity of 95% or more, 600g/m², thickness of 2mm, Inco Technical Services Limited) were compressed at a pressure of 3MT respectively. In the reaction surface, anode and cathode gas inlets, anode and cathode gas outlets, and cooling water inlet and outlet were formed in the size of 0.5m x 1cm through the cutting method. After that, to prevent leakage of gas, filler was impregnated into the portion excluding the reaction surface in which inflow gas was reacted with the membrane and electrode assembly, i.e. the portion where the membrane and electrode assembly was in contact with inflowing fluid. The plate, in

which the filler was impregnated, was dried in the oven at a temperature of 100°C for

30 minutes. The dried plate was bonded on the front and rear surfaces of the nickel structure bipolar plate manufactured according to Example 9, thereby manufacturing the nickel structure bipolar plate. Example 12

The manufacture of a nickel structure bipolar plate in which nickel structure is wrapped with bipolar plate

A nickel structure of size of 7cm x 16cm (porosity of 95% or more, 600g/m², thickness of 2mm, Inco Technical Services Limited) was compressed into a pressure of

3MT, and manufactured into the plate in the form of "T^" (7cm x 7cm). The nickel

structure bipolar plate manufactured according to Example 9 was inserted and bonded

into an inner space of the plate manufactured in the form of "^ ". To prevent leakage

of gas of the bonded nickel structure bipolar plate, filler was impregnated into the remaining portions except the reaction surface, i.e., the portion where inflow gas and the membrane and electrode assembly were in contact with each other. After that, the bipolar plate in which the filler was impregnated was dried in the oven at a temperature of 100 °C for 30 minutes, thereby reducing contact resistance simultaneously at the

front and rear surfaces of the bipolar plate.

Example 13

The manufacture of nickel structure bipolar plate using one sheet of nickel structure

As shown in FIG. 9, a nickel structure of size of 7cm x 21cm(porosity of 95% or more, 600g/m², thickness of 2mm, Inco Technical Services Limited) was divided into three parts in the size of 7cm x 7cm. On the basis of a central nickel structure 54 located at the center of the three parts of nickel structures, the right and left nickel structures 56 and 58 were compressed at a pressure of 3MT and manufactured in the form of plates 56' and 58'. After that, silicone was impregnated as a filler into the remaining portions except a reaction surface 52 of a prescribed size where the actual chemical reaction was taking place, and at the same time, the same silicone was impregnated also into the central nickel structure 54. Flow channels were formed in the front and rear surfaces of the central nickel structure 54, which the filler was impregnated, through the pressing method, thereby forming the exterior form of the bipolar plate. The bipolar plate 54' having the flow channel, the left plate 56' and the right plate 58' were dried in the oven at a temperature of 100°C for 30 minutes.

Finally, the left plate 56' and the right plate 58' centering the bipolar plate 54' were folded in opposite directions, so that the left plate 56' and the right plate 58' were bonded on the bipolar plate 54' having the flow channel, and thereby the nickel structure bipolar plate was manufactured.

Though the nickel structure bipolar plate manufactured according to the above method had the same effect as the nickel structure bipolar plate manufactured according to Example 12, it can improve productivity in case of mass production.

Example 14

The manufacture of a stacked nickel structure plates requiring low voltage and high current As shown in FIG. 10, a nickel structure 60 was manufactured in such a manner that a nickel structure of the size 7cm x 7cm (porosity of 95% or more, 600g/m², thickness of 2mm, Inco Technical Services Limited) 60' did have another nickel structure 60" of the size 2cm x 2cm on an upper end thereof After that, to increase surface conductivity, only the nickel structure 60' having the size of 7cm x 7cm was compressed at a pressure of 3MT. To prevent leakage of gas, 5.4g of filler was impregnated into the nickel structure 60' through the rolling method. Here, the used filler was the silicone liquid type gasket manufactured by the VALQUA company. The plate in which the filler was impregnated was dried in the oven at a temperature of 100 °C for 30 minutes, and then, a flow channel was formed on the nickel structure

plate through the pressing method. A wire connector hole 22 was formed on the nickel structure 60" of size of 2cm x 2cm, in which the filler was not impregnated, to connect the wire. At this time, the manufactured flow channel 20 was 1mm in width and 2mm in depth, and the wire connector hole was 1cm in diameter. The sizes of anode and cathode gas inlets 10 and 18, anode and cathode gas outlets 12 and 16 and cooling water inlet and outlet 8 and 14 were 0.5cm x 1cm. After that, the surface of the nickel structure plate on which the flow channel 20 was formed was treated with toluene, and thereby a nickel structure plate 62 was manufactured.

Example 15

The manufacture of a stack requiring low voltage and high current using nickel structure plates

A stack was manufactured as shown in FIGS. 11 and 12 using the nickel structure plate 62 manufactured according to Example 14. Here, FIG. 11 illustrates a perspective view of a piled state of the nickel structure plates, and FIG. 12 illustrates a side view of a structure of the piled nickel structure plates.

As shown in the drawings, the stack did have an anode side end plate 40 at a left end and a cathode end plate 40' at a right end to form an exterior form of the stack. The stack consisted of a plurality of nickel structure plates 62 piled up inside the stack, thereby, having anode polarity when fuel fluid flowed along the flow channel 20 of the nickel structure plate 62 and cathode polarity when oxidant fluid flowed along the other flow channel 20 of the other nickel structure plate 62 according to the type of gases. Meanwhile, a membrane and electrode assembly 46 was disposed between the nickel structure plates 62. A conductive plate 44 for preventing leakage of gas or the cooling plate 48 for cooling the heat of reaction generated from the membrane and electrode assembly 46 was disposed on the contour of the nickel structure plate 62 adjacent to the membrane and electrode assembly 46. Here, all nickel structure plates 62 where fluid flows were manufactured according to the same manufacturing method and composition. Each nickel structure plate 62 had a round type wire connector hole 22 at an upper end thereof, so that the nickel structure plates 62 having the same polarity were connected with the wire, thereby collecting electricity.

Example 16

The manufacture of a nickel structure plate of a stack using non-conductive plates

A bipolar plate of the size 7cm x 7cm was manufactured according to Example 9 using the silicon liquid type gasket manufactured by the VALQUA company. After that, a nickel structure of the size 7cm x 14cm(porosity of 95% or more, 600g/m², thickness of 2mm, Inco Technical Services Limited) was compressed at 3MT and manufactured into a plate in the form of "t= " (7cm x 7cm). The bipolar plate made of

the non-conductive material was inserted and bonded into an inner space of the plate manufactured in the form of "t ". To prevent leakage of gas of the bonded nickel structure bipolar plate, filler was impregnated into the remaining portions except the reaction surface, i.e. a portion where inflow fluid and the membrane and electrode assembly were in contact with each other. After that, the bipolar plate in which the

filler was impregnated was dried in the oven at a temperature of 100°C for 30 minutes,

and thereby a multi-bipolar plate capable of reducing contact resistance simultaneously at the front and rear surfaces of the bipolar plate was manufactured.

Example 17

The manufacture of a cooling plate used in a stack using one sheet of nickel structure

A cooling plate was manufactured according to Example 1 except that a cooling water path 66 extended from the cooling water inlet 8 to the cooling water outlet 14, so that cooling water flowing into the cooling plate could cool the heat of the unit cell.

The manufactured nickel structure cooling plate had the form as FIG. 13.

Example 18

The manufacture of another cooling plate used in a stack using one sheet of nickel structure

A cooling plate was manufactured according to Example 1 except that a nickel structure of the size 7cm x 10cm was used and the filler was impregnated to the extent of 7cm x 7cm from an upper end of the nickel structure and was not impregnated further in the remaining part of the nickel structure of the size 7cm x 3 cm. Furthermore, a cooling water channel 66 extended from the cooling water inlet 8 to the cooling water outlet 14, so that cooling water flowing into the cooling plate 48 cooled the heat of the unit cell. The part of the nickel structure(size of 7cm x 3cm) where the filler was not impregnated was exposed to the ambient air, thereby discharging the heat of the unit cell to the ambient air.

The manufactured nickel structure cooling plate had the form as FIG. 14.

Example 19

The manufacture of a stack using cooling plate and bipolar plate made by the nickel structure

A stack was manufactured as shown in FIG. 8 using the nickel structure cooling plate 48 according to Example 17. The stack had the same form as the stack manufactured according to Example 10. However, the stack according to this example is light in weight compared with other cooling plates made of metal or graphite.

Example 20

A stack was manufactured as shown in FIG. 15 using the nickel structure cooling plate 48 according to Example 18. The stack had a form similar to the stack manufactured according to Example 10. However, because a portion of the cooling plate 48 was exposed to the extent of 3 cm to the ambient air to allow cooling of the unit cell using air or cooling fluid, the stack had improved cooling efficiency compared with other stacks, which used only inside cooling water as a cooling system. Example 21

The manufacture of a cooling bipolar plate

A cooling bipolar plate was manufactured according to Example 9 with the exception that a nickel structure of the size 7cm x 10cm was used. The filler was impregnated to the extent of 7cm x 7cm from an upper end of the nickel structure and was not further impregnated in the remaining part of the nickel structure of the size 7cm x 3 cm. Therefore, the cooling bipolar plate according to this example performed the same function as the nickel structure bipolar plate 24 manufactured according to Example 9. However, the cooling bipolar plate of this example showed higher efficiency in cooling than the nickel structure bipolar plate 24 manufactured according to Example 9, because a part of the cooling bipolar plate was exposed to the ambient air.

The manufactured cooling bipolar plate is shown in FIG. 16.

Example 22 The manufacture of a stack including cooling bipolar plate

A stack was manufactured as shown in FIG. 17 using the cooling bipolar plate 64 manufactured according to Example 21.

The stack had an anode side end plate 40 at a left end and a cathode side end plate 40' at a right end to form an exterior form of the stack. The stack had a cooling bipolar plate 64 therein and membrane and electrode assemblies 46 located at the right and left sides. Therefore membrane and electrode assemblies 46 and the cooling bipolar plate 64 were located in series. Meanwhile, at the right and left ends of the membrane and electrode assemblies 46 and the cooling bipolar plate 64 located in series, the stack consisted of the following: the membrane electrode assembly 46, the metal structure plate 4, the conductive plate 44 and the end plate 40 and 40' at the left and right ends thereof.

The stack of this embodiment had improved cooling efficiency compared with the stack manufactured according to Example 10. Hereinafter, a performance test of the metal structure plate and metal structure bipolar plate according to the present invention was carried out.

Experiment

1. The fuel cell system The test was carried out in a single cell test station. The test station was integrated in such a manner that temperature(cell, anode and cathode gas humidifier) and fluid speed(anode and cathode gas) could be controlled. A personal computer(PC) was connected to a HP6050A electronic load main frame through an interface board, and thereby the load could be adjusted by the PC and data was collected. An automatic testing system was equipped and current-potential test was performed 50 times in average weekly using the automatic testing system.

Instead of a graphite bipolar plate, a hybrid type bipolar plate according to the present invention was used in the cell. By heating-pressing an E-tek electrode of 2mgPt/cm² on Nafion 115 membrane at temperature of 135 °C and at a pressure of 3MT,

a membrane and electrode assembly was manufactured.

2. Hybrid type bipolar plate according to the present invention

A hybrid type bipolar plate according to the present invention was manufactured using the existing nickel structure (porosity > 90%) and silicone type filler.

Results

As shown in FIG. 18, various nickel structure bipolar plates were tested with

hydrogen and oxygen at atmospheric pressure and a cell temperature of 50 ^°C. In all

cases where an activated area was covered with the nickel structure in which the filler was not impregnated, the cell performance could not reach high current density. Because a straight area between the gas inlet and outlet was low in resistance to gas passage, most of the gas passed this low resistance area. The remaining area covered with the nickel structure was filled with water, and it was difficult to remove water due to capillary force. As shown in FIG. 3(a), cut nickel structures having gas channels were tested. As a result, the cut nickel structure showed a slightly improved performance but it was lower than the nickel structure having both of the channel and filler. In the case of a porous structure bipolar plate, which was filled with water, water overflowed to the electrode and reduce gas diffusivity, and finally, performance of the fuel cell deteriorated.

The graphite bipolar plate and the nickel structure bipolar plate were compared with each other in their performance, and the compared result is shown in FIG. 19. The performance of the fuel cell including the nickel structure plate was similar to that of the graphite plate, and did not have any problem in reaching a relatively high current

density of lA/cm² at the temperature of 70 °C. Nickel, which was less in porosity, or

metal, which was stronger in corrosion resistance, might be appropriate to reduce ohmic resistance, and could improve energy efficiency and density per volume in reaching current densities over 1 A/cm². FIG. 20 illustrates cell potential at various current densities and cell temperatures.

The cell potential showed an increase until the temperature of 70 °C and for

further increase of the temperature until 80 °C was negligible. To overcome the above

phenomenon, another filler was used and tested. As a result, the bipolar plate, slightly transformed by the filler, showed good cooling function in cooling of the fuel cell and the stack.

Industrial Applicability The bipolar plate according to the present invention, which is manufactured by impregnating the filler on the metal structure plate, satisfies various physical properties required in the bipolar plate by changing composition of the filler impregnated. Additionally, the bipolar plate reduces the manufacturing time by making the manufacturing process simple. Furthermore, the bipolar plate has a good cooling and electric performance in the high temperature stack, and reduces manufacturing cost by not using graphite and steel but using the metal structure plate, which has prescribed pores.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope of the present invention.

Claims

We Claim:

1. A metal structure plate in which filler is impregnated in a metal structure and one or more flow channels are formed.

2. A metal structure plate of claim 1, wherein the metal structure is made of material selected from the following group: iron, nickel, chrome, silicon, tin, manganese, copper, magnesium, aluminum and other metal materials or a combination thereof.

3. ^'A metal structure plate of claim 1, wherein the filler is a conductive polymer, a non-conductive polymer, graphite or other materials capable of preventing leakage of gas.

4. A unit cell which comprises of a metal structure plate of claim 1 to 3.

5. A unit cell of claim 4, wherein the metal structure is made of material selected from the following group: iron, nickel, chrome, silicon, tin, manganese, copper, magnesium, aluminum and other metal materials or a combination thereof.

6. A unit cell of claim 4, wherein the filler is a conductive polymer, a non- conductive polymer, graphite or other materials capable of preventing leakage of gas.

7. A metal structure bipolar plate in which filler is impregnated in a metal structure and one or more flow channels are formed at both sides.

8. A metal structure bipolar plate of claim 7, wherein the metal structure is made of material selected from the following group: iron, nickel, chrome, silicon, tin, manganese, copper, magnesium, aluminum and other metal materials or a combination thereof.

9. A metal structure bipolar plate of claim 7, wherein the filler is a conductive polymer, a non-conductive polymer, graphite or other materials capable of preventing leakage of gas.

10. A stack which comprises of a metal structure plate in which filler is impregnated in a metal structure and one or more flow channels are formed.

11. A stack of claim 10, wherein the metal structure is made of material selected from the following group: iron, nickel, chrome, silicon, tin, manganese, copper, magnesium, aluminum and other metal materials or a combination thereof.

12. A stack of claim 10, wherein the filler is a conductive polymer, a non- conductive polymer, graphite or other materials capable of preventing leakage of gas.

13. A stack of claim 10, wherein the metal structure plate has an upper portion where the filler is not impregnated, the upper portion being capable of wire connecting.

14. A stack of claim 10, further includes additional bipolar plate.

15. A stack of claim 14, wherein the bipolar plate is a metal structure bipolar plate having both sides on which metal structures are bonded.

16. A stack of claim 14, wherein the bipolar plate is a metal structure bipolar

plate wrapped and bonded with a metal structure being in the form of "t ".

17. A stack of claim 16, wherein the bipolar plate is a conductive or non- conductive bipolar plate.

18. A method for manufacturing a metal structure plate comprising the steps of: forming one or more flow channels on a metal structure through pressing or cutting; and obtaining a metal structure plate by impregnating filler into the metal structure having one or more flow channels.

19. A method for manufacturing a metal structure plate comprising the steps of: impregnating filler into a metal structure; and obtaining a metal structure plate by forming one or more flow channels on the metal structure, in which the filler is impregnated, through pressing or cutting or injection molding.

20. A method for manufacturing a metal structure bipolar plate comprising the steps of: forming one or more flow channels on both sides of a metal structure through pressing or cutting; and obtaining a metal structure plate by impregnating filler into the metal structure having one or more flow channels.

21. A method for manufacturing a metal structure bipolar plate comprising the steps of: impregnating filler into a metal structure; and obtaining a metal structure plate by forming one or more flow channels on both sides of the metal structure, in which the filler is impregnated, through pressing or cutting or injection molding.

22. A method for manufacturing a metal structure bipolar plate comprising the steps of: dividing a metal structure into three parts and compressing the right and left parts of the metal structures; impregnating filler into the right and left parts of the metal structures with the exception of the central part of the metal structure and the reaction area; forming one or more flow channels on the central metal structure through pressing or cutting; and obtaining a metal structure bipolar plate by bonding one of the right or left part of the metal structures on the central part of the metal structure having one or more flow channels and bonding the other of the right or left part of the metal structures under the central part of the metal structure having one or more flow channels.

23. A metal structure cooling plate used for the purpose of cooling unit cells or stacks using the metal structure plate of claims 1 to 6.

24. A metal structure cooling plate of claim 23, wherein one or more cooling water channels extends from a cooling water inlet to a cooling water outlet to allow cooling water to flow in the cooling plate and to cool heat of the unit cells.

25. A metal structure cooling bipolar plate used for the purpose of cooling unit cells or stacks using the metal structure bipolar plate of claims 7 to 9.

26. A metal structure cooling bipolar plate of claim 25, further includes a metal structure in which filler is not impregnated disposed at a lower end of the bipolar plate.

27. A method for manufacturing a metal structure cooling plate comprising the steps of: forming one or more cooling water channels on a metal structure through pressing or cutting; and obtaining a metal structure plate by impregnating filler into the metal structure having one or more cooling water channels.

28. A method for manufacturing a metal structure cooling plate comprising the steps of: impregnating filler into a metal structure; and obtaining a metal structure plate by forming one or more cooling water channels on the metal structure, in which the filler is impregnated, through pressing or cutting or injection molding.

29. A method for manufacturing a cooling bipolar plate comprising the steps of: forming one or more cooling water channels on both sides of a metal structure through pressing or cutting; and obtaining a metal structure plate by impregnating filler into the metal structure having one or more cooling water channels.

30. A method for manufacturing a cooling bipolar plate comprising the steps of: impregnating filler into a metal structure; and obtaining a metal structure plate by forming one or more cooling water channels on both sides of the metal structure, in which the filler is impregnated, through pressing or cutting or injection molding.