CN100346501C - Sealing structure of fuel battery - Google Patents

Abstract

The invention relates to a sealing structure of a fuel cell, which includes a membrane electrode, a deflector, and a sealing ring. The membrane electrode is arranged in the middle, and the deflector is pressed on both sides of the membrane electrode. The ring is arranged on the surface where the guide plate and the membrane electrode are pressed together, and the membrane electrode includes an active area and a sealing area, wherein the sealing area is arranged around the active area, and the active area includes a proton exchange membrane, a porous support Material, catalyst, the catalyst is attached to the porous support material and pressed on both sides of the proton exchange membrane, the sealing area is extended from the porous support material in the active area and filled with permeable hot melt plastic or thermosetting rubber, resin Composition, the thickness of the sealing area is the same as the thickness of the active area. Compared with the prior art, the invention has the advantages of high sealing reliability, good manufacturability, and favorable mass production.

Description

Sealing structure of a fuel cell

technical field

The invention relates to key components of a fuel cell, in particular to a fuel cell sealing structure.

Background technique

An electrochemical fuel cell is a device that converts hydrogen fuel and oxidant into electrical energy and reaction products. The internal core component of the device is the membrane electrode (Membrane Electrode Assembly, referred to as MEA). The membrane electrode (MEA) is composed of a proton exchange membrane and two porous conductive materials, such as carbon paper, sandwiched between the two sides of the membrane. On the two boundary surfaces of the membrane and the carbon paper, there are even and finely dispersed catalysts for initiating electrochemical reactions, such as metal platinum catalysts. Conductive objects can be used on both sides of the membrane electrode to draw the electrons generated during the electrochemical reaction through an external circuit to form a current loop.

At the anode end of the membrane electrode, the fuel can permeate through the porous diffusion material (carbon paper), and an electrochemical reaction occurs on the surface of the catalyst, losing electrons and forming positive ions, which can migrate through the proton exchange membrane, Reach the cathode end of the other end of the membrane electrode. At the cathode end of the membrane electrode, a gas containing an oxidant (such as oxygen), such as air, penetrates through the porous diffusion material (carbon paper), and electrochemically reacts on the surface of the catalyst to obtain electrons to form negative ions. Anions formed at the cathode end react with positive ions migrating from the anode end to form reaction products.

In a proton exchange membrane fuel cell that uses hydrogen as fuel and air containing oxygen as the oxidant (or pure oxygen as the oxidant), the catalytic electrochemical reaction of fuel hydrogen in the anode region produces positive hydride ions (or protons). The proton exchange membrane facilitates the migration of positive hydride ions from the anode region to the cathode region. In addition, the proton exchange membrane separates the hydrogen-containing fuel gas stream from the oxygen-containing gas stream so that they do not mix with each other and cause an explosive reaction.

In the cathode area, oxygen gets electrons on the surface of the catalyst to form negative ions, and reacts with positive hydrogen ions migrated from the anode area to generate water as a reaction product. In a proton exchange membrane fuel cell using hydrogen and air (oxygen), the anode reaction and cathode reaction can be expressed by the following equation:

Anode reaction: H ₂ → 2H ⁺ +2e

Cathode reaction: 1/2O ₂ +2H ⁺ +2e→H2O

In a typical proton exchange membrane fuel cell, the membrane electrode (MEA) is generally placed between two conductive plates, and the surface of each guide electrode plate in contact with the membrane electrode is formed by die casting, stamping or mechanical milling to form More than one diversion groove. These current-guiding electrode plates can be pole plates of metal material or graphite material. The diversion channels and diversion grooves on these diversion electrode plates guide the fuel and oxidant into the anode region and the cathode region on both sides of the membrane electrode respectively. In the structure of a single proton exchange membrane fuel cell, there is only one membrane electrode, and the two sides of the membrane electrode are respectively the guide plate of the anode fuel and the guide plate of the cathode oxidant. These guide plates not only serve as the current collector mother plate, but also serve as the mechanical support on both sides of the membrane electrode. The guide grooves on the guide plate serve as channels for fuel and oxidant to enter the surface of the anode and cathode, and serve as a way to take away the fuel cell. Channels for water generated during operation.

In order to increase the total power of the entire proton exchange membrane fuel cell, two or more single cells can usually be stacked in series to form a battery pack or connected in a tiled manner to form a battery pack. In direct-stacked and series-connected battery packs, there can be diversion grooves on both sides of a pole plate, one of which can be used as the anode diversion surface of one membrane electrode, and the other side can be used as the cathode of another adjacent membrane electrode. The diversion surface, this kind of plate is called a bipolar plate. A series of cells are connected together in a certain way to form a battery pack. The battery pack is usually fastened together by the front end plate, the rear end plate and the tie rods to form a whole.

A typical battery pack usually includes: (1) diversion inlet and diversion channel of fuel and oxidant gas, fuel (such as hydrogen, methanol or hydrogen-rich gas obtained by reforming methanol, natural gas, gasoline) and oxidant ( (mainly oxygen or air) is evenly distributed into the diversion grooves of each anode and cathode surface; (2) the inlet and outlet and diversion channels of the cooling fluid (such as water), and the cooling fluid is evenly distributed into the cooling channels in each battery pack , absorb the heat generated by the electrochemical exothermic reaction of hydrogen and oxygen in the fuel cell and take it out of the battery pack to dissipate heat; (3) The outlet of the fuel and oxidant gas and the corresponding guide channel, when the fuel gas and oxidant gas are discharged , can carry out the liquid and vapor state water generated in the fuel cell. Usually, the inlets and outlets of all fuels, oxidants, and cooling fluids are opened on one or both end plates of the fuel cell stack.

Proton exchange membrane fuel cells can be used as the power system of all vehicles, ships and other vehicles, and can also be used as portable, mobile and fixed power generation devices. In order to ensure that the fuel and oxidant gases in the proton exchange membrane fuel cell can be distributed to the entire surface of the membrane electrode on both sides without mixing, the sealing technology is very critical. If the seal is not good, two situations may occur: one situation is that the fuel gas and the oxidant gas are mixed inside the fuel cell. In a fuel cell running with hydrogen and oxygen, this mixture is very fatal. Once an explosion occurs, The destructive power is very large; another situation is that the fuel gas or oxidant gas leaks to the outside of the fuel cell. explode. Therefore, great attention should be paid to fuel cell sealing technology. The current fuel cell sealing technology mainly has the following three methods:

Method 1: The area of the proton exchange membrane is much larger than that of the porous support material in the membrane electrode, such as carbon paper, for the preparation of the membrane electrode. The membrane beyond the area of the carbon paper is not the active area of the electrochemical reaction, but Two sheets of carbon paper (with a catalyst layer pressed in the middle) are pressed together on both sides of the membrane in the electrochemical active area. In this method, the membrane electrode is placed between the two guide plates, and the membrane with greater electrochemical activity is directly used as the base material of the sealing material, and it prevents the two adjacent guide plates from directly contacting and short circuiting. Function, as shown in Fig. 1, it is the structural schematic diagram of existing membrane electrode, comprises air inlet 1, cooling water inlet 2, hydrogen gas inlet 3, proton exchange membrane 4, the activated part 5 that is coated with catalyst among the figure, Fig. 2 is a structural schematic diagram of a deflector and a sealing ring, which includes an air inlet 1, a cooling water inlet 2, a hydrogen gas inlet 3, a deflector 6, a flow guide groove 7, and a sealing ring 8.

The second method: the sealing device adopted in European patent EP00604683A1 is shown in Figure 3, and the device includes an air inlet 1, a sealing ring 8, and a membrane electrode 10, and Figure 4 is a sectional view of Figure 3, including an air inlet Gas port 1, proton exchange membrane 4, sealing ring 8, and carbon paper 9, which are characterized in that the porous support materials on both sides of the membrane electrode, such as two sheets of carbon paper 9, are greatly extended from the active area of the membrane electrode, and the sealing material 8 is placed on the proton exchange membrane 4 of the membrane electrode, so that the two guide plates clamping the membrane electrode do not need to place sealing materials again.

The third method: the sealing device adopted by the patent of Shanghai Shenli Company (Patent No. 01238847.5), as shown in Figure 5, is characterized in that the membrane electrode is divided into two parts, and the 10th part in Figure 5 is the membrane electrode, which is the reaction The active part, part 11 in Fig. 5 is the frame of the membrane electrode (only the part other than the dotted line). Part 10 and Part 11 are two completely different materials, and the boundary between Parts 10 and 11 is very clear. Part 11 is generally composed of plastic or elastic rubber or resin, and is connected with Part 10 by bonding. The seal between the electrode as a whole and the deflector can also be placed on the frame or on the deflector by using a sealing ring.

Although the above-mentioned sealing technology can achieve the purpose of sealing the fuel cell, it has the following defects:

1. The defect corresponding to the first method is that the proton exchange membrane is generally a relatively expensive material. After a large amount of exposure, it is not fully utilized and the waste is serious; the proton exchange membrane is a kind of material that is easy to age and break. Direct contact with the sealing material under pressure is more likely to break, resulting in sealing failure; the proton exchange membrane is a corrosive material with strong acid, and it is in long-term contact with the sealing material on the deflector, which is easy to denature the sealing material and cause sealing failure.

2. The defect corresponding to the second method is that the sealing ring material is placed on the diffusion layer material (carbon paper) of the membrane electrode, especially it is very difficult to set the sealing ring material on the diffusion layer material (carbon paper) on both sides of the membrane electrode. big. Because the diffusion layer material (carbon paper) is often very thin, mainly to enhance the rapid diffusion of fuel gas and oxidant air, so when placing a sealing ring on such a thin material, the thickness of the sealing ring must be very thin, and the thin sealing ring It is easily deformed. In addition, both sides of the electrode are provided with sealing rings. The proton exchange membrane under the sealing rings is subject to huge concentrated pressure, which is easily deformed by compression. It is easy to break under long-term pressure and cause sealing failure.

3. The defect corresponding to the third method is that the membrane electrode is divided into two parts 10 and 11. Since the materials of the two parts 10 and 11 are different, the technical requirements for mutual bonding are very high, and the bonding of the two parts 10 and 11 The thickness of the final transfer zone is almost the same as that of the original two parts 10 and 11, which increases the difficulty of bonding, and this difficult bonding technology is not conducive to large-scale production of membrane electrodes.

Contents of the invention

The object of the present invention is to provide a fuel cell sealing structure with high sealing reliability, good manufacturability, and favorable mass production in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions: a fuel cell sealing structure, including membrane electrodes, deflectors, and sealing rings, the membrane electrodes are arranged in the middle, and the deflectors are press-fitted on the On both sides of the membrane electrode, the sealing ring is arranged on the surface where the guide plate and the membrane electrode are pressed together, and it is characterized in that the membrane electrode includes an active area and a sealing area, wherein the sealing area is arranged around the active area, The active area includes a proton exchange membrane, a porous support material, and a catalyst. The catalyst is attached to the porous support material and pressed on both sides of the proton exchange membrane. The sealing area is outwardly from the porous support material of the active area. Extended and filled with permeable hot-melt plastic or thermosetting rubber or resin, the thickness of the sealing area is the same as that of the active area; the porous support material extends outward to the outer frame edge of the sealing area, and the hot-melt There are three layers of rubber plastic or thermosetting rubber and resin, in which the middle layer is set in the middle of the extended porous support material, and the other two layers are set on both sides of the extended porous support material, and the two layers are hot-melted by hot pressing Rubber plastic or thermosetting rubber and resin penetrate into the porous support material, and the three layers of sealing material are integrated.

The present invention utilizes a kind of hot-melt polymer engineering plastics or thermosetting rubber and resin, such as polyester engineering plastics. The characteristics of this engineering polymer plastics or rubber and resin are similar to those under the hot-pressing conditions for membrane electrode production ( Under a certain temperature and pressure), the proton exchange membrane can be covered and bonded protectively when melting, so that the outer frame of the membrane electrode extending outward can be a variety of situations listed in the following embodiments. Compared with the prior art, the invention has high sealing reliability and good manufacturability, and is beneficial to mass production.

Description of drawings

Fig. 1 is the structural representation of existing membrane electrode;

Fig. 2 is the structural representation of existing deflector and sealing ring;

Fig. 3 is the structural representation of the membrane electrode of existing European patent;

Fig. 4 is A-A sectional view of Fig. 3;

Fig. 5 is the structural representation of another kind of existing membrane electrode;

Fig. 6 is a structural representation of the present invention;

Fig. 7 is a schematic diagram of the membrane electrode structure of Example 1 of the present invention;

Fig. 8 is a schematic diagram of the membrane electrode structure of Example 2 of the present invention;

Fig. 9 is a schematic structural view of the membrane electrode of Example 3 of the present invention before thermocompression forming;

Fig. 10 is a schematic structural view of the membrane electrode of Example 3 of the present invention after thermocompression molding;

Fig. 11 is a schematic diagram of the overall structure of the membrane electrode in Example 3 of the present invention;

Fig. 12 is a B-B sectional view of Fig. 11 .

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Fig. 6 and Fig. 7, a sealing structure of a fuel cell includes a membrane electrode 14, a deflector 6, and a sealing ring 8, the membrane electrode 14 is arranged in the middle, and the deflector 6 is provided with The guide groove 7, the guide plate 6 is pressed on both sides of the membrane electrode 14, the sealing ring 8 is arranged on the surface where the guide plate 6 and the membrane electrode 14 are pressed, and the membrane electrode 14 includes the active area 5 And sealing area 13, wherein, sealing area 13 is arranged on the periphery of active area 5, described active area 5 comprises proton exchange membrane 4, the carbon paper 9 that adheres to catalyst, described sealing area 13 upper and lower two ends are provided with air inlet Gas port 1, cooling water inlet (not shown), hydrogen gas inlet (not shown), the sealing area 13 is extended outwards by the proton exchange membrane 4 or carbon paper 9 in the active area 5 and filled with permeable hot melt The thickness of the sealing area 13 is the same as that of the active area 5 .

In this embodiment, a kind of proton exchange membrane 4 only extends slightly outward than the membrane electrode active area 5, and the outer frame extending outward of the membrane electrode is composed of three layers of hot-melt adhesive plastic layers 12, which are heated once when the membrane electrode is hot-pressed. Press molding, so that the proton exchange membrane extending slightly outwards is connected to the liner layer 121 on the upper and lower ends, and the two sides of the liner layer 121 are attached with two layers of hot-melt adhesive plastic layers 122. The thickness of these three layers of plastic layers after hot pressing is the same as Membrane electrode thickness is exactly the same.

Example 2

As shown in Fig. 6 and Fig. 8, a sealing structure of a fuel cell includes a membrane electrode 14, a deflector 6, and a sealing ring 8, the membrane electrode 14 is arranged in the middle, and the deflector 6 is provided with The guide groove 7, the guide plate 6 is pressed on both sides of the membrane electrode 14, the sealing ring 8 is arranged on the surface where the guide plate 6 and the membrane electrode 14 are pressed, and the membrane electrode 14 includes the active area 5 And sealing area 13, wherein, sealing area 13 is arranged on the periphery of active area 5, described active area 5 comprises proton exchange membrane 4, the carbon paper 9 that adheres to catalyst, described sealing area 13 upper and lower two ends are provided with air inlet Gas port 1, cooling water inlet (not shown), hydrogen gas inlet (not shown), the sealing area 13 is extended outwards by the proton exchange membrane 4 or carbon paper 9 in the active area 5 and filled with permeable hot melt The thickness of the sealing area 13 is the same as that of the active area 5 .

In this embodiment, a proton exchange membrane 4 is completely extended from the active area of the membrane electrode to the edge of the outer frame, and the upper and lower layers of hot melt adhesive plastic layers 12 are covered on the proton membrane by hot pressing when the membrane electrode is hot pressed. , and its thickness is exactly the same as that of the membrane electrode.

Example 3

As shown in Fig. 6, Fig. 9, Fig. 10, Fig. 11 and Fig. 12, a sealing structure of a fuel cell includes a membrane electrode 14, a deflector 6, and a sealing ring 8, and the membrane electrode 14 is arranged in the middle, The deflector 6 is provided with a diversion groove 7, and the deflector 6 is pressed on both sides of the membrane electrode 14, and the sealing ring 8 is arranged on the surface where the deflector 6 and the membrane electrode 14 are pressed together. The membrane electrode 14 includes an active area 5 and a sealing area 13, wherein the sealing area 13 is arranged around the active area 5, and the active area 5 includes a proton exchange membrane 4 and a carbon paper 9 with a catalyst attached. The upper and lower ends of the zone 13 are provided with an air inlet 1, a cooling water inlet (not shown), and a hydrogen gas inlet (not shown), and the sealed zone 13 is formed by the proton exchange membrane 4 or carbon paper 9 extends outward and is filled with permeable hot-melt adhesive plastic 12. The thickness of the sealing area 13 is the same as that of the active area 5.

Present embodiment is a kind of very different method, and it is that outside membrane electrode active zone 5, continue to extend outwards a small part by two-side diffusion layer material (carbon paper 9), and its interlayer multi-layer hot-melt adhesive plastic layer 12, Wherein the outermost two layers cover the proton membrane, as shown in Figure 9, when hot pressing under the membrane electrode hot pressing condition, the multilayer hot melt adhesive plastic 12 is forced to squeeze into the porous diffusion layer material (carbon paper 9) after melting, The two outermost layers cover a small portion of the extended proton exchange membrane. In this way, the hot-pressed film electrode and the hot-pressed epitaxial frame are completed together, and the thickness of the multi-layer hot-melt adhesive plastic is just melted and squeezed into the porous diffusion layer material (carbon paper 9) under the hot-pressed condition, and the diffusion layer material (carbon paper 9 ) surface is also plasticized, so that the thickness of the membrane electrode is the same as the thickness of the epitaxial frame, as shown in Figure 10, Figure 11, and Figure 12.

All the above-mentioned methods use hot-melt adhesive plastics to complete the membrane electrode and its frame at one time when the electrode is hot-pressed. The thickness of the frame is equal to that of the membrane electrode, and the surface of the frame is a flat polymer elastic body. When the deflector 6 and the membrane electrode 14 are assembled into a fuel cell, a sealing ring 8 (rigid or stretchable elastic body) can be provided on the deflector 6 to achieve the purpose of sealing.

Claims (1)

1. A sealing structure for a fuel cell, comprising a membrane electrode, a deflector, and a sealing ring. The membrane electrode is arranged in the middle, and the deflector is pressed on both sides of the membrane electrode. The sealing ring It is arranged on the surface where the guide plate and the membrane electrode are pressed, and it is characterized in that the membrane electrode includes an active area and a sealing area, wherein the sealing area is arranged around the active area, and the active area includes a proton exchange membrane, Porous support material and catalyst, the catalyst is attached to the porous support material and pressed on both sides of the proton exchange membrane, the sealing area is extended outward from the porous support material in the active area and filled with permeable hot melt plastic or thermosetting Composed of rubber and resin, the thickness of the sealing area is the same as that of the active area; the porous support material extends outward to the edge of the outer frame of the sealing area, and the hot melt plastic or thermosetting rubber and resin are three layers , wherein the middle layer is set in the middle of the extended porous support material, and the other two layers are set on both sides of the extended porous support material, and the two layers of hot melt plastic or thermosetting rubber or resin are infiltrated into the porous Inside the support material, three layers of sealing material are integrated.

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