JP2693636B2 - Fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a fuel cell having a wet seal structure in which an edge portion of an electrode having a catalyst supported on a porous substrate has a high density. .

(Prior Art) As is well known, a fuel cell is a device that directly converts the chemical energy of fuel into electrical energy.
In this fuel cell, a pair of porous electrodes are usually placed across the electrolyte, and a gas fuel such as hydrogen is brought into contact with the back surface of one electrode, and an oxidant such as oxygen is brought into contact with the back surface of the other electrode. The electric energy generated by the electrochemical reaction that occurs at this time is taken out from the pair of electrodes.

As the above-mentioned electrolyte, molten carbonate, alkaline solution,
Although there is an acidic solution or the like, the principle of a fuel cell using phosphoric acid as an electrolyte as a typical fuel cell will be described.

In FIG. 9, 1 is an electrolyte layer (hereinafter referred to as matrix layer) formed by impregnating a fibrous sheet or a mineral powder with phosphoric acid. Reference numeral 2 is an anode, 3 is a cathode, which is a carbonaceous porous electrode, and a platinum catalyst is usually applied to the surface in contact with the matrix layer 1. Reference numeral 4 denotes a space through which a gas containing hydrogen flows, and reference numeral 5 denotes a space through which an oxidizing gas, usually air.

The hydrogen gas flowing into the space 4 diffuses into the pores of the porous anode 2 and reaches the catalyst. Here, the hydrogen gas is dissociated into hydrogen ions and electrons by the action of the catalyst. The reaction formula is H ₂ → 2H ⁺ + 2e. Hydrogen ions enter the matrix layer 1 and migrate toward the cathode 3 due to concentration diffusion and electric field action.
On the other hand, the electrons separated by the dissociation of hydrogen gas flow into the anode 2. At the cathode 3, hydrogen ions that have migrated from the anode 2, oxygen that has been supplied to the space 5 as an oxidant and has diffused through the pores of the cathode 3, and work from the anode 2 through an external power load, The three electrons that have returned to the cathode 3 of the above cause the following reaction on the catalyst surface.

4H ⁺ ＋ 4e ＋ O ₂ → 2H ₂ O In this way, hydrogen is oxidized into water, and the chemical energy at this time becomes electrical energy, which is used as a battery that provides electrical energy in an external power load. The reaction is complete.

Usually, a fuel cell is constructed by stacking a plurality of the above unit cells. When stacking the unit cells in this manner, it is necessary to secure an electrical connection path between the unit cells, supply a reaction gas to each unit cell, and secure a gas passage for removing a reaction product. There is. Further, in the fuel cell, a cell structure is required so that the electrolyte is constantly supplied to the matrix layer 1 in order to allow the cell to operate for a long time.

Conventionally, many combinations of fuel cell such as cell design and structural constitution, electrolyte and other structural materials are known. However, common to all fuel cells is the prevention of leakage and inadvertent mixing of gaseous reactants both inside and outside the cell. If such mixing occurs, there is a risk of causing a catastrophe.

Therefore, regarding the structure of the fuel cell, the first consideration is to effectively and reliably configure the sealing of the reaction gas. Many sealing devices have been devised and used in the past, including the use of gaskets, O-rings, special battery frames, welding and brazing, as well as the liquid electrolyte itself. It has been proposed to construct one wet seal using the wetting effect (Japanese Patent Publication No. 58-
See No. 152).

(Problems to be Solved by the Invention) FIG. 10 shows the configuration of a conventional fuel cell. In the figure, 1 is a matrix layer, 2 and 3 are an anode and a cathode, respectively, which are formed from a porous substrate. Although not shown in the figure, a catalyst layer having an effect of promoting an electrode reaction is formed on the surfaces of the anode 2 and the cathode 3 which are in contact with the matrix layer 1. Reference numeral 6 is a separator that prevents mixing of fuel gas and oxidant gas and also serves as an interconnector that electrically connects the unit cells. Made of Reference numerals 8 and 9 respectively denote gas flow paths through which air, which is a fuel gas and an oxidant gas, flows. next,
Details of the anode 2 and the cathode 3 will be described with reference to FIG. 11 by taking the anode 2 as an example. The anode 2 has a wet seal portion 7 at an electrode end portion parallel to the gas flow passage 8 of the fuel gas. Since the fuel gas flowing through the gas flow path 8 diffuses in the pores of the reaction section 10 and moves to the catalyst layer (not shown) formed at the interface with the matrix layer 1, the reaction section 10 prevents gas diffusion. The density is not so high and the pore size is also large.

On the other hand, the wet seal portion 7 is formed to have a higher density than that of the reaction portion 10 and has a structure having a small pore size. The wet seal portion 7 has a capillary force (phosphoric acid surface tension and porous It absorbs and holds by the affinity of the plate) and has a wet sealing function. Therefore, about 2 of the reaction part 10
It is about twice as dense.

However, in the above conventional structure,
As shown in FIG. 11 and FIG. 11, the wet seal portion 7 has a sealing function on the entire end portion of the electrode. Therefore, the wet seal portion 7 is filled with the electrolyte, and the electrolyte overflows due to a change in the volume of the electrolyte filled in the wet seal portion 7 at the time of a transient state such as a start-stop or a load change. There is a drawback in that the electrolyte in the battery is reduced due to the drainage and the life of the wet seal function is shortened.

Therefore, an object of the present invention is to provide a fuel cell capable of generating stable electric power with a long life without the electrolyte oozing out from the peripheral portion of the cell.

[Configuration of the Invention] (Means for Solving the Problems) The present invention relates to a fuel cell electrode made of a conductive material that is permeable to gas, substantially impermeable to liquid, and forms a gas flow path. A reaction part formed of a catalyst layer provided on the surface of the fuel cell electrode, and a hydrophilic peripheral sealing part configured to hold an electrolyte on an end face of the electrode parallel to the gas flow path of the fuel cell electrode. In the fuel cell configured to provide a wet seal at the peripheral sealing portion, a buffer portion that absorbs and holds the electrolyte and has the same density as the reaction portion is provided in a part of the peripheral sealing portion. It is characterized by that.

(Operation) Since the buffer part is provided at the end of the electrode, the electrolyte overflowing from the peripheral sealing part can be absorbed and retained, and the electrolyte can be replenished to the peripheral sealing part when it becomes necessary again. Also,
This function can absorb and hold not only the electrode ends but also the electrolyte that overflows from the electrolyte layer of the cell, so that the electrolyte can be prevented from overflowing from the cell and the wetting of the cell stack surface by the electrolyte can be prevented. There is no short circuit due to the liquid junction containing the conductive powder, the laminated surface can be always kept dry, and the outflow due to the capillary action of the electrolyte can be prevented.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention.

In the figure, reference numeral 1 is a matrix layer, on both sides of which an anode 20 and a cathode 21 are provided, a separator 6 is provided on the other side of the anode 20, and a separator 6 is also provided on the other side of the cathode 21 to form a fuel cell. There is.

FIG. 2 is a perspective view showing the structure of the anode 20. The anode 20 is formed of a porous substrate similar to the conventional anode 2 described above, and a catalyst layer (not shown) that promotes an electrode reaction is formed on the surface in contact with the matrix layer 1, and a gas flow path for fuel gas is formed. The wet end portions 22a and 22b are provided at the end portions of the electrodes parallel to the electrode 8, and the buffer portions 23a and 23b having the same density as that of the reaction portion 10 are provided on the outer sides thereof. Here, the wet seal part 22a is provided in parallel with the gas flow path 8, and the wet seal part 22b is located at a position close to both ends of the wet seal part 22a along the longitudinal direction and the wet seal part 22a. Is provided in a direction orthogonal to the longitudinal direction of the.

Further, the cathode 21 is formed of a porous substrate like the above-mentioned conventional cathode 3, and a catalyst layer (not shown) for promoting an electrode reaction on the surface in contact with the matrix layer 1.
Are formed, and wet seal portions 24a, 24b are provided at the electrode end portions parallel to the gas flow path 9 for the oxidant gas, and buffer portions 25a, 25b having the same density as the reaction portion 10 are provided on the outer sides thereof. Here, the wet seal portion 24a is provided in parallel with the gas flow path 9, and the wet seal portion 24b is located at a position close to both end portions along the longitudinal direction of the wet seal portion 24a and the wet seal portion 24a.
Is provided in a direction orthogonal to the longitudinal direction of the.

FIG. 3 is a partially exploded perspective view showing a state in which a plurality of fuel cells configured as described above are stacked. In the figure, reference numeral 26 denotes a fuel cell stack, and a fuel inlet manifold 27 and a fuel outlet manifold 28 are arranged so as to face each other on the side surface of the fuel cell stack 26 directly or via a frame, and The fuel gas is attached to the gas passage 8 so as to be uniformly supplied and discharged, and the air inlet manifold 29 and the air outlet manifold 30 are arranged so as to face each other, and the air is supplied to the gas passage 9 of the cathode 21. Are installed so that they are uniformly supplied and discharged. On the other hand, the fuel inlet manifold 27, the fuel outlet manifold 28,
Air inlet manifold 29 and air outlet manifold 30
In order to prevent the fuel gas and air from leaking out and causing an accident, as shown in the figure for the fuel inlet manifold 27, it is attached via a packing 31, a gasket 32, and a packing 33. Here, the packing 31 is
This is because the side surface does not become a geometrical plane when a plurality of fuel cells are stacked, and this is corrected. Further, the packing 33 is for correcting the flange 27a of the fuel inlet manifold 27, which is not a geometrical plane.

The packings 31, 33 are formed of a soft packing material in a frame shape, and the gasket 32 is formed of a packing material slightly harder than the packings 31, 33 in a frame shape.

Next, the operation of the embodiment configured as described above will be described. The wet seal parts 22a, 22b and 24a, 24b are filled with an electrolyte, but the electrolyte oozing from these is temporarily absorbed and held in the buffer parts 23, 25 without flowing out to the laminated surface. Therefore, the laminated surface is not wetted, and the laminated surface is not moved by the capillary force. After that, when the wet seal portions 22a, 22b and 24a, 24b are again in a state of absorbing the electrolyte, the electrolyte absorbed and held in the buffer portions 23a, 23b and 25a, 25b serves as the supply source.

Similarly, the electrolyte exuding from the peripheral portion of the matrix layer 1 is also absorbed and held by the buffer portions 23a, 23b and 25a, 25b, and the cell stack surface is always kept dry with respect to phosphoric acid as the electrolyte. It is possible to prevent bleeding and liquid junction.

Therefore, with the above structure, loss of the electrolyte from the peripheral portion of the fuel cell can be prevented, and the life of the fuel cell due to the disappearance of the electrolyte can be significantly extended.

The present invention is not limited to the above-described embodiment (hereinafter referred to as the first embodiment), and various modifications can be made.

FIG. 4 is a perspective view showing a second embodiment of the present invention. The second embodiment is disclosed in JP-A-62-20255 and JP-A-62-5.
It is applied to an improved cell structure of those disclosed in JP-A-5872, JP-A-61-116760, JP-A-61-227367 and the like. That is, in the figure, 1 is a matrix layer, and 6
Is a separator, 31 is an anode, 32 is a cathode, and 33 is a first
And 34 denotes a second laminated element. The second stacking element 34 has wet seal portions 35a, 35b substantially similar to the wet seal portions 22a, 22b of the anode 20 in the first embodiment, and buffer portions 36a, 36b substantially similar to the buffer portions 25a, 25b. And the cathode 32 is also provided with wet seal portions 37a, 37b and buffer portions 38a, 38b at the same positions as the second stacking element 34. In the first stacking element 33, the wet seal parts 39a, 39b substantially similar to the wet seal parts 24a, 24b of the cathode 21 in the first embodiment, and the buffer parts 40a, 40b substantially similar to the buffer parts 25a, 25b. , Respectively, and also for the anode 31,
Wet seal parts 41a and 41b are provided at the same positions as the first laminated element 33.
And buffer portions 42a and 42b, respectively. Also in the second embodiment configured as described above, the same effect can be obtained by the same operation as that of the first embodiment.

FIG. 5 is a perspective view showing an anode in the third embodiment of the present invention. The anode 42 in this example is
The structure of the wet seal part and the buffer part is different from that of the anode 20 in the first embodiment described above. That is, the wet seal portions 43a and 43b are provided at the electrode end portions that are parallel to the gas flow path 8 and at positions that are parallel to the gas flow path 8 and are apart from each other. In addition, the buffer portions 44a and 44b are the wet seal portion 4
It is provided between 3a and 43b and outside the wet seal portion 43b. Although not shown in the drawing, a cathode is also provided with a wet seal portion and a buffer portion at the electrode end portion parallel to the gas flow path 9 with the same configuration as the anode 42. The third embodiment having the anode 42 and the cathode configured as above can also obtain the same effect by the same operation as the first embodiment.

FIG. 6 is a perspective view showing an anode according to the fourth embodiment of the present invention. Anode in this fourth embodiment
Reference numeral 45 denotes a structure in which a wet seal portion is further added to the anode 42 in the above-mentioned third embodiment,
Along with this, a buffer section is additionally provided. That is, the wet seal portions 46a and 46b are provided at the electrode end portions that are parallel to the gas flow passage 8 at positions parallel to and apart from the gas flow passage 8, respectively.
Is provided in a direction orthogonal to the wet seal portions 46a, 46b and at a position close to the ends of the wet seal portions 46a, 46b along the longitudinal direction. Therefore, the buffer unit is also the buffer unit 44a,
44b is divided, and buffer sections 48a, 48b, 48c, 48d are provided. The fourth embodiment having the anode 45 and the cathode configured as above can also obtain the same effect by the same operation as the first embodiment.

FIG. 7 is a perspective view showing a fifth embodiment of the present invention. The fifth embodiment is a modification of the second embodiment described above and is applied to a stack having an internal manifold structure. That is, in the figure, 50 is a matrix layer and 51
Is an anode, 52 is a cathode, 53 is a first laminated element, 54
Is a second laminated element, and 55 is a separator. In the second stacking element 54, the gas flow passage 9 provided in the central portion, the air inlet manifold 56 and the air outlet manifold 57 provided so as to communicate with each other at the end portion of the gas flow passage 9, and the gas flow A fuel inlet manifold 58 and a fuel outlet manifold 59 are provided in parallel with the passage 9 and so as not to communicate with each other. In the second stacking element 54, the gas flow passage 9, the air inlet manifold 56, the air outlet manifold 57, the fuel inlet manifold 58, and the fuel outlet manifold 59 are appropriately separated from the edges, and the outer edge is appropriately separated from the inside. A wet seal portion 60 is provided in the space between the wet seal portion 60 and the outer peripheral edge, and the buffer portion 61a, the wet seal portion 60 and the gas flow path 9,
A buffer portion 61b between the air inlet manifold 56 and the air outlet manifold 59, a buffer portion 61c between the wet seal portion 60 and the fuel inlet manifold 58, and a buffer portion 61d between the wet seal portion 60 and the fuel outlet manifold 59. To provide. In the first stacking element 53, a fuel flow path (not shown) provided in the central portion in a direction orthogonal to the gas flow path 9 described above is connected to a fuel flow path (not shown) so as to communicate with an end portion of the gas flow path. The inlet manifold and the fuel inlet manifold are provided with an air inlet manifold and an air outlet manifold (not shown) that are parallel to the gas passage and are not in communication with each other. These gas passage, fuel inlet manifold, fuel outlet manifold, air inlet A wet seal part and a buffer part are provided between the manifold and the air outlet manifold and the outer peripheral edge in the same arrangement relationship as the wet seal part and the buffer part provided in the first stacking element 53 described above.
The anode 51 has an air inlet manifold (not shown), an air outlet manifold 62, and a fuel inlet at positions corresponding to the air inlet manifold 56, the air outlet manifold 57, the fuel inlet manifold 58, and the fuel outlet manifold 59, respectively. A manifold 63 and a fuel outlet manifold (not shown) are provided. This anode
51, an outer side that is appropriately separated from the edge of the plane corresponding to the plane of the gas flow path (not shown) provided in the first stacking element 53 described above, and an air inlet manifold, an air outlet manifold, and an air outlet manifold that are not shown. 62, fuel inlet manifold 63 and fuel outlet manifold (not shown)
A wet seal portion 64 is provided in the space between the inner periphery and the inner periphery that is appropriately separated from the outer peripheral edge. The matrix layer 50 also has an air inlet manifold (not shown), an air outlet manifold 65, and a fuel inlet manifold at positions corresponding to the air inlet manifold 56, the air outlet manifold 62, the fuel inlet manifold 63, and the fuel outlet manifold 59, respectively. 6
6, a fuel outlet manifold (not shown) is provided. Also in the fifth embodiment configured as described above, the same effect as the first embodiment can be obtained by the same operation.

[Effects of the Invention] As described above, according to the present invention, a part of the electrode end portion, which is a peripheral sealing portion forming a wet seal, has a function of absorbing and holding an electrolyte and has the same density as the battery reaction portion. Since the buffer part which is provided is also provided, the peripheral sealing part does not impair the original wet sealing function, and the electrolyte does not overflow even when the volume of the filled electrolyte increases. In particular, it is possible to provide a fuel cell capable of preventing loss of the electrolyte from the end portion of the cell even at the time of starting and stopping and enabling stable operation for a long time.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of an embodiment of the present invention, FIG. 2 is a perspective view of an anode using the embodiment of the present invention, and FIG. FIG. 4 is an exploded perspective view, FIG. 4 is a perspective view showing the configuration of another embodiment of the present invention, FIG. 5 is a perspective view of an anode used in still another embodiment of the present invention, and FIG. FIG. 7 is a perspective view of an anode used in still another embodiment of the present invention, FIG. 7 is a perspective view showing the structure of yet another embodiment of the present invention, and FIG. 8 is an enlarged view of “A” part in FIG. 7. FIG. 9 is an explanatory view of the principle of the present invention, FIG. 10 is a perspective view showing the structure of a conventional fuel cell, and FIG.
The figure is a perspective view of an anode used in the conventional fuel cell shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Electrolyte layer 6 ... Separator 8 ... Fuel gas flow path 9 ... Oxidant gas flow path 20 ... Anode 21 ... Cathode 22a, 22b, 24a, 24b ... Wet seal part 23a, 23b, 25a, 25b ... Buffer part

Claims (1)

(57) [Claims] 1. A fuel cell electrode comprising a conductive material that is permeable to gas, substantially impermeable to liquid, and forms a gas flow path, and a catalyst layer provided on the surface of the fuel cell electrode. And a hydrophilic peripheral sealing portion configured to hold an electrolyte on an end surface of the electrode parallel to the gas flow path of the fuel cell electrode, and the peripheral sealing portion provides a wet seal. In the fuel cell configured as described above, a buffer part that absorbs and holds the electrolyte and has the same density as the reaction part is provided in a part of the peripheral sealing part.