KR20070036500A - Fuel cell system and stack using therefor - Google Patents

Abstract

The present invention provides an electrode film assembly comprising a polymer film, an anode electrode and a cathode electrode provided on both sides of the polymer film, and a bipolar plate positioned at both ends of the electrode film assembly to generate electricity; A current collector plate in electrical contact with the bipolar plate; An end plate in electrical contact with the current collector plate; A stack composed of a conductive adhesive layer interposed between the bipolar plate and the current collector plate, and a fuel cell system having the same, preferably between the outermost plate provided at both ends of the unit cell and the current collector plate for collecting electricity By interposing a conductive adhesive layer on the substrate, the contact resistance between the outermost plate and the current collector plate may be reduced, thereby improving power generation efficiency of the fuel cell system.

Outermost plate, current collector plate, conductive adhesive layer, end plate

Description

FUEL CELL SYSTEM AND STACK USING THEREFOR}

1 shows schematically a fuel cell system according to the invention;

2 is a view showing another example of a fuel supply unit of the fuel cell system shown in FIG. 1;

3 is a view showing a structure of a stack having a conductive adhesive layer interposed according to the present invention;

4 is an exploded perspective view showing components arranged sequentially at one end of a stack.

<Description of Symbols for Major Parts of Drawings>

10: stack

12: electrode film assembly

14 bipolar plate

14a: outermost plate

16: conductive adhesive layer

17: current collector

18: end plate

20: fuel supply unit

22: raw fuel tank

24: reformer

30: air supply

The present invention relates to a fuel cell system that generates electrical energy through an electrochemical reaction between hydrogen and oxygen, and more particularly, between a current collector plate for collecting electricity generated from a unit cell and a bipolar plate positioned at the shortest end of the unit cell. The present invention relates to a stack having a conductive adhesive layer interposed therebetween and a fuel cell system having the same.

In general, a fuel cell system is a power generation device that converts electric energy by a chemical reaction between hydrogen and oxygen, and is being researched and developed as an alternative to solve the difficulty of securing power and increasing global environmental problems caused by the increase in power demand. . Hydrogen is generally an alcohol fuel such as methanol and ethanol; It can be obtained by reforming a hydrogen-containing fuel such as a hydrocarbon-based fuel such as methane, propane, butane or natural gas-based fuel such as liquefied natural gas.

The fuel cell system includes a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), and a solid oxide fuel cell (SOFC) depending on the type of electrolyte used. ), Polymer electrolyte membrane fuel cells (PEMFC), alkaline fuel cells (AFC) and direct methanol fuel cells (DMFC). In addition, the fuel cell system may be applied to various applications such as mobile power supply, transportation, distributed generation, etc. according to the type of fuel used according to the type and the operating temperature, the output range and the like.

Polymer electrolyte fuel cells and direct methanol fuel cells have been widely studied for mobile power sources. These fuel cells basically have a stack in which a plurality of unit cells for generating electricity are stacked. The basic structure of the stack consists of a structure in which a plurality of unit cells stacked between end plates are fastened by bolts and nuts. The unit cell includes an MEA having anode and cathode electrodes provided on both sides of the electrolyte membrane, and a separator, that is, a bipolar plate, each having a channel for fluid flow and formed on both sides of the MEA.

The bipolar plate serves to discharge carbon dioxide and water generated at the anode electrode and the cathode electrode to the outside while supplying hydrogen-containing fuel and oxygen to the anode electrode and the cathode electrode, respectively.

In this case, a current collector plate for collecting electricity generated from the unit cell is provided between the bipolar plate (hereinafter, referred to as the 'outermost plate') and the end plate positioned at both ends of the unit cell. The current collector plate is provided to reinforce the brittleness of the outermost plate when the bolt and nut are fastened as well as the function of collecting current. However, a contact resistance of about 300 mPa exists between the outermost plate and the current collector, which causes a problem of lowering power generation efficiency of the fuel cell system.

The present invention is proposed to solve the conventional problems as described above, the conductive adhesive layer is interposed therebetween so as to reduce the contact resistance between the outermost plate constituting the unit cell and the current collector plate facing it It is an object of the present invention to provide a stack and a fuel cell system having the same.

In order to achieve the above object, according to the present invention, the stack is provided with an electrode membrane assembly consisting of a polymer electrode and an anode electrode and a cathode electrode provided on both sides of the polymer membrane, and a bipolar plate located at both ends of the electrode membrane assembly to provide electricity A unit cell to generate; A current collector plate in electrical contact with the bipolar plate; An end plate in electrical contact with the current collector plate; Characterized in that it consists of a conductive adhesive layer interposed between the bipolar plate and the collector plate.

The conductive adhesive layer is made of a conductive adhesive such as silver paste, carbon paste or gold paste.

According to another embodiment of the present invention, a fuel cell system comprises: a stack having an electric power generation unit for generating electricity through a chemical reaction between hydrogen and oxygen, and a current collector plate in electrical contact with the electric power generation unit; A fuel supply unit supplying hydrogen-containing fuel to the stack; An oxygen supply unit for supplying oxygen to the stack,

It characterized in that it further comprises a conductive adhesive layer interposed between the current collector plate and the electrical power generation portion to enable electrical conduction.

Hereinafter, a stack according to the present invention and a fuel cell system having the same will be described with reference to the accompanying drawings.

Referring to FIG. 1, a fuel cell system according to the present invention includes a stack 10 in which one or more unit cells are stacked, a fuel supply unit 20 supplying hydrogen-containing fuel to the stack 10, and a stack 10. It has an oxygen supply part 30 which supplies oxygen to it.

Here, the hydrogen-containing fuel may be an alcohol fuel such as methanol or ethanol; Hydrocarbon fuels such as methane, propane and butane; It means a raw fuel such as natural gas-based fuel such as liquefied natural gas or a liquid or gaseous fuel such as hydrogen, and the hydrogen can preferably be obtained by modifying the above-described raw fuel.

The fuel supply unit 20 may be configured only with a raw fuel supply tank (not shown) in the direct methanol fuel cell for directly supplying the above-described raw fuel to the stack 10. Meanwhile, as shown in FIG. 2, in the polymer electrolyte fuel cell supplying reformed hydrogen to the stack 10, the fuel supply unit 20 includes a raw fuel storage unit 22 in which raw fuel is stored, and a source. The reformer 24 may be configured to supply the stack 10 with reformed fuel mainly composed of hydrogen obtained through reforming of the raw fuel supplied from the fuel storage unit 22.

Hereinafter, the direct methanol fuel cell will be described.

Referring to FIG. 3, the stack 10 includes a polymer film 12a, an electrode film assembly 12 (MEA; Membrane Electrode Assembly) including anode electrodes and cathode electrodes 12b and 12c provided on both sides of the polymer film 12a. Has

In the electrode membrane assembly 12, an electrode is produced by applying a catalytic material on a porous support such as carbon paper. The anode electrode 12b oxidizes hydrogen gas contained in the hydrogen-containing fuel to generate hydrogen ions (H ⁺ ) and electrons (e ⁻ ), and discharges carbon dioxide generated as a by-product of the oxidation process to the outside. The cathode electrode 12c discharges water generated as a result of this chemical reaction to the outside while a chemical reaction between oxygen and hydrogen ions occurs.

In addition, the stack 10 is interposed in a state facing each other between the adjacent electrode film assembly 12 to supply hydrogen and oxygen to the anode electrode 12b and the cathode electrode 12c of the electrode film assembly 12, respectively. Bipolar plate 14. Reference numeral 11 denotes an electricity generator that generates electricity by stacking a plurality of unit cells 11a to 11n including the electrode membrane assembly 12 and the bipolar plates 14 positioned on both sides thereof.

Referring to FIG. 4 in detail, the stack 10 includes a current collector plate 17 sequentially provided on the outer surface of the bipolar plate 14a, ie, the outermost plate 14a, located at both ends of the electricity generating unit 11. It further comprises an end plate 18.

According to the present invention, the conductive adhesive layer 16 is provided between the outermost plate 14a and the current collector plate 17 to lower the contact resistance between the outermost plate 14a and the current collector plate 17. The conductive adhesive layer 16 may be provided by, for example, applying a conductive adhesive such as silver paste, carbon paste or gold paste to the outer surface of the outermost plate 14a. Alternatively, the conductive adhesive layer 16 may be formed by applying the above-mentioned conductive adhesive on the opposite surface opposite to the outer surface of the outermost plate 14a.

For example, when silver paste or carbon paste is used as the conductive adhesive, the contact resistance between the outermost plate 14a and the current collector plate 17 can be reduced to about 70 mPa. In addition, when gold paste is used as the conductive adhesive, the contact resistance between the outermost plate 14a and the current collector plate 17 can be reduced to about 20 mPa. As such, by lowering the contact resistance between the outermost plate 14a and the current collector plate 17, the electricity generation efficiency of the fuel cell system can be improved by effectively collecting electricity generated by the electricity generation unit 11.

Referring again to FIG. 3, bipolar plates 14 for supplying hydrogen-containing fuel and oxygen are provided on the outer surfaces of the anode electrode 12b and the cathode electrode 12c, respectively. A fuel supply passage (not shown) through which hydrogen-containing fuel flows is formed on one surface of the bipolar plate 14 facing the anode electrode 12b, while oxygen in the air is provided on the other surface facing the cathode electrode 12c. An inflow oxygen supply passage (not shown) is formed.

The anode electrode 12b provided to face one surface of the bipolar plate 14 includes a catalyst layer for converting hydrogen-containing fuel supplied through a fuel supply passage formed on one surface into hydrogen ions and electrons by an oxidation reaction, and It has a gas diffusion layer (GDL) for discharging carbon dioxide to the outside while acting to distribute the hydrogen-containing fuel uniformly in the catalyst layer. Similarly, the cathode electrode 12c provided to face the other surface of the bipolar plate 14 includes a catalyst layer for chemically reacting oxygen and hydrogen ions supplied through an oxygen supply passage formed on the other surface, and the oxygen being the catalyst layer. It is composed of a gas diffusion layer that discharges the water generated through the chemical reaction to the outside while acting to be uniformly dispersed in.

In addition, the polymer membrane 12a has a function of ion exchange for transferring hydrogen ions generated in the catalyst layer of the anode electrode 12b to the catalyst layer of the cathode electrode 12c, and a conductive polymer electrolyte having a function of preventing permeation of hydrogen-containing fuel. As a film | membrane, it has a thickness about 50-200 micrometers. As the polymer membrane 12a, for example, a resin solution such as perfluorinated sulfonic acid is coated on a perfluorofluorinated resin film made of a perfluoroselfonate resin (Nafion), a porous polytetrafluoroethylene thin film support, and the like. And membranes in which cation exchange resins and inorganic silicates are coated on porous membranes and porous non-conductive polymer supports.

The stack 10 composed of the components as described above constitutes the electricity generating portion 11 to prevent leakage of hydrogen-containing fuel and air supplied to the electricity generating portion 11 and to form a structure as a battery. It has a fastening member (not shown) for pressing the unit cells to a predetermined pressure to fasten one.

For example, the fastening member may be screwed into a plurality of through bars (not shown) respectively penetrating through a plurality of through holes (not shown) formed in the edge portion of the end plate 18, and screw portions formed at both ends of the through bar. It has a nut (not shown). Therefore, the electricity generating unit 11 is held in a crimped state by the end plate 18 by screwing a nut to the threaded portion formed at the end of the through rod while the through rods penetrate the through hole.

Hereinafter, the operation of the fuel cell system according to the present invention will be described.

Hydrogen-containing fuel supplied from the fuel supply unit 20 is supplied to the electricity generating unit 11, in particular the anode electrode 12b of the electrode membrane assembly 12, through the fuel supply passage of the bipolar plate 14 in the stack 10. . Oxygen supplied from the oxygen supply unit 30 is supplied to the electricity generating unit 11, in particular the cathode electrode 12c of the electrode film assembly 12, through the oxygen supply passage of the bipolar plate 14 in the stack 10.

Hydrogen ions and carbon dioxide are produced by the hydrogen oxidation reaction at the anode electrode 12b. At this time, the hydrogen ions move to the cathode electrode 12c through the electrolyte membrane 12a, and the carbon dioxide moves the fuel supply flow path of the bipolar plate 14. Through the outside. Water generated by the oxygen reduction reaction at the cathode electrode 12c is easily moved from the cathode electrode 12c to the bipolar plate 14 side and then discharged to the outside through the oxygen supply passage. On the other hand, electricity is generated by electrons generated at the anode electrode 12b moving to the cathode electrode 12c. At this time, the electricity generated in the individual unit cells (11a ~ 11n) is collected in the current collector plate 17 via the bipolar plate 14 is connected to each other so that the electrical current is supplied to the output terminal provided to the end plate 18 Through the external load.

In this case, the contact resistance between the outermost plate 14a and the current collector plate 17 is lowered by the conductive adhesive layer 16 provided between the outermost plate 14a and the current collector plate 17. It can improve the power generation efficiency.

According to the present invention, the unit cell preferably reduces the contact resistance between the outermost plate and the current collector plate by interposing a conductive adhesive layer between the outermost plate provided at both ends of the electricity generating unit and the current collector plate for collecting electricity. Improve the power generation efficiency of the system.

Claims (11)

A unit cell including a polymer film, an electrode film assembly including an anode electrode and a cathode electrode provided at both sides of the polymer film, and a bipolar plate positioned at both ends of the electrode film assembly; A current collector plate in electrical contact with the bipolar plate; An end plate in electrical contact with the current collector plate; And a conductive adhesive layer interposed between the bipolar plate and the current collector plate. The method of claim 1, The conductive adhesive layer is a stack, characterized in that made of silver paste or carbon paste. The method of claim 1, The conductive adhesive layer is a stack, characterized in that made of gold paste. A stack having an electricity generation unit generating electricity through a chemical reaction between hydrogen and oxygen, and a current collector plate in electrical contact with the electricity generation unit; A fuel supply unit supplying hydrogen-containing fuel to the stack; An oxygen supply unit for supplying oxygen to the stack, The fuel cell system further comprises a conductive adhesive layer interposed between the current collector plate and the electrical power generation unit to enable electrical conduction. The method of claim 4, wherein And the current collector plate is in electrical contact with an outermost plate provided at both ends of the electric power generation unit. The method of claim 4, wherein The conductive adhesive layer is a fuel cell system, characterized in that made of silver paste or carbon paste. The method of claim 4, wherein The conductive adhesive layer is a fuel cell system, characterized in that made of gold paste. The method of claim 4, wherein The hydrogen-containing fuel is a fuel cell system, characterized in that consisting of at least one raw fuel selected from alcohol fuel, hydrocarbon fuel or natural gas fuel. The method of claim 4, wherein The hydrogen-containing fuel is a fuel cell system, characterized in that consisting of hydrogen. The method of claim 9, And the hydrogen is obtained by reforming at least one raw fuel selected from alcohol fuel, hydrocarbon fuel or natural gas fuel. The method of claim 10, The fuel supply unit is a fuel cell system, characterized in that consisting of a raw fuel storage unit for storing the raw fuel and a reformer for reforming the raw fuel with hydrogen.

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