JPH10270066A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end plate with electric improved insulation. SOLUTION: For end plates 3, 4 used for a fuel cell, metal plates 31, 41 formed of aluminum with a preset thickness and sufficient strength are coated with insulating film sheet structures 32, 42 formed of fluorine based resin including polytertrafluoroethylene(PTEE) and polyphenylenesulfide(PPS). Coating with the insulating films is applied at least to an area opposed to a cell stack of the plate and to an area opposed to a manifold and so no pin hole is formed in the insulating layers of the end plates 3, 4, resulating in excellent electric insulation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a fuel cell,
In particular, the present invention relates to improvement of end plates provided above and below in a stacking direction of a battery stack.

[0002]

2. Description of the Related Art In general, a fuel cell has a predetermined number of unit cells each having an anode and a cathode disposed via an electrolyte matrix, and a predetermined number of separators, and both ends of the stacked body are sandwiched by end plates. Tightened, and
The anode gas supply / discharge manifold and the cathode gas supply / discharge manifold are each mounted.

[0003]

The end plate used to hold the battery stack is coated by a vapor deposition method in which a robust metal plate is sprayed with a resin. Under recent circumstances where pinholes are generated due to resin particles and air bubbles, etc., and there is a strong demand for higher performance, a fuel cell using an end plate formed by vapor deposition is sufficient in terms of insulation. I couldn't say.

Accordingly, the present invention has been made in view of these problems, and has been made to provide a fuel cell using an end plate improved in terms of insulation. .

[0005]

According to the present invention, in order to achieve the above object, a substantially rectangular parallelepiped battery stack in which a plurality of unit cells are stacked is tightened from above and below in a stacking direction via an end plate. In a fuel cell in which a reaction gas supply / discharge manifold is arranged on a side surface of a battery stack, the end plate is formed by coating a metal plate with an insulating film, and coating the metal plate with the insulating film. Is applied to at least a portion of the plate body facing the battery stack and a portion facing the manifold.

[0006] In the end plate having such a configuration, since there is no pinhole caused by the vapor deposition method, the end plate is excellent in electric insulation. As the insulating film, a film prepared by rolling a molten material having no foaming property so as not to generate pinholes is used.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A phosphoric acid type fuel cell 1 (hereinafter referred to as "fuel cell 1") which is an example of a fuel cell according to the present invention will be described with reference to FIGS. FIG. 3 is a perspective view showing the entire configuration of the fuel cell 1, and FIG. 4 is an assembly view of a main part (in FIG. 4, a manifold is not shown for convenience).

The fuel cell 1 includes a battery stack 2 in which unit cells are stacked in a vertical direction, and an end plate 3 in which the battery stack 2 is vertically arranged via current collectors 13 and 14 (see FIG. 2). , 4, a pair of manifolds 5, 6 for supplying and discharging hydrogen, a pair of manifolds 7, 8 for supplying and discharging air,
It is composed of various mounting members 9, 10, 11a, 11b and 12.

The end plates 3 and 4 have a pair of cross beams 9 and 10 connected at their four ends by long screws 11a as connecting rods having a length substantially equal to that of the battery stack. Thereby, the battery stack 2 is tightened. Long screw 1
1a are fixed by nuts 11b at the ends of the beam members 9 and 10 in parallel with the stacking direction of the battery stack 2 to connect the end pools 3 and 4.

The manifolds 5 to 8 are pressed and fixed to the battery stack on the side surfaces thereof by using a band 12 such as a metal belt which can be tightened with a predetermined tightening force. In addition, between the battery stack 2 and insulating members 5a to 8a (not shown, see FIG. 2). As shown in FIG. 5, the battery stack 2 includes a single cell 200 in which an anode 203 and a cathode 202 are arranged via an electrolyte matrix 201, and a porous substrate 212 and a porous substrate 213 on both surfaces of a separator plate 211. Are laminated alternately with the composite separator 210 formed by laminating.

The electrolyte matrix 201 is formed by impregnating phosphoric acid into a rectangular sheet obtained by binding silicon carbide with a fluorine resin. The anode 203 and the cathode 202 are obtained by pressing a sheet prepared by binding carbon particles carrying a platinum catalyst or a platinum alloy catalyst with a fluororesin to carbon paper made of carbon fiber subjected to a water-repellent treatment. It is. However, since the reactivity of hydrogen to the catalyst is higher than that of air, the amount of the catalyst is set slightly smaller for the anode 203 than for the cathode 202.

A separator plate 211 is a flat plate having the same size as the electrolyte matrix 201, and has a band-shaped edge seal portion along one pair of opposing sides on one side (a bottom view in FIG. 5). A strip-shaped edge seal portion 211b is provided on the back side (upper side in FIG. 5) along a pair of opposing sides orthogonal to this, and the whole is formed of dense glassy carbon. I have.

The porous substrate 212 is a rectangular plate having a large number of channels 212a and ribs 212b formed on the surface thereof, and is fitted between the edge seal portions 211a. On the other hand, the porous substrate 213 is a rectangular plate having a large number of channels 213a and ribs 213b formed on the surface, and is fitted between the edge seal portions 211b. Channel 212a... And channel 2
13a are orthogonal to each other.

The porous substrates 212 and 213 have the same size as the anode 203 and the cathode 202, and are formed by impregnating porous carbon (for example, having an average particle diameter of 40 μm and a porosity of 70%) with phosphoric acid. ing. The upper and lower ends of the battery stack 2 are provided with half plates 220 and 230, respectively. The half plates 220 and 230 are the same as the composite separator 210, but have porous substrates 212 and 213 on only one side.

When the fuel cell 1 configured as described above receives the supply of hydrogen gas and air, it starts generating power by an electrochemical reaction. Next, the end plates 3 and 4 will be described in detail with reference to FIGS. FIG. 1 is an assembly view showing a configuration of an end plate, and FIG. 2 is a sectional view of the fuel cell 1. In FIG. 2, for the sake of simplicity, only the main parts are shown.

As shown in FIG. 1, the end plates 3 and 4 are made of a metal plate 31 or 41 having a predetermined thickness and sufficient strength, such as an aluminum plate, and an insulating material such as PTFE (polytetrafluoroethylene) or PPS. (Polyphenylene sulfide) and other film-based structures 32 and 42 having a thickness of about 200 μm. The film sheet structures 32 and 42 are connected to the bottom plate 321 (42).
Side plates 322 to 325 (422 to 425) from around 1)
Is a top-open-type box body that stands up at a predetermined height. The bottom plate 321 (421) has substantially the same vertical and horizontal dimensions as the metal plates 31, 41, and the side plates 322 to 325 (422 to 425).
The height A of each of the seal members 5a to
8a is sized sufficiently to contact the side plates 322 to 325 (422 to 425).

As shown in FIG. 2, the film sheet structures 32 and 42 have metal plates 31 and 41 as bottom plates 321 and 421, respectively.
Is provided so as to cover the surface facing the battery stack 2. In such end plates 3 and 4, since the insulating layer is formed by a film sheet in which pinholes do not originally exist, the insulating properties are excellent. Normally, during operation of the fuel cell, excess phosphoric acid that has overflowed from the unit cell may accumulate in each manifold mounting portion of the end plate. If there is a pinhole on the side of the end plate that comes into contact with the phosphoric acid, phosphoric acid penetrates into the inside of the end plate from the pinhole, causing a decrease in electrical insulation. In addition, although the metal plate is oxidized, the mechanical strength of the end plate may be impaired,
In the present fuel cell 1, since the insulating layer made of the film sheet covered with the metal plates 31 and 41 has no pinholes, phosphoric acid does not enter the inside, and the electrical insulation is significantly improved. The phenomenon of plate oxidation is also prevented.

Furthermore, since the end plate is usually a rectangular parallelepiped, the resin film once coated on each ridge may be brittlely peeled off in the conventional vapor deposition method. However, the end plate covering the film sheet structures 32 and 42 may be fragile. In the plates 3 and 4, the strength of the resin film at the ridges is high, and the insulation at each ridge is maintained well. In addition, in the conventional vapor deposition method, an end plate is manufactured through a step of heating and spraying an insulating resin and then a step of drying, and the manufacturing process is relatively complicated. Plates 3, 4
Simply attaches the film sheet structures 32 and 42 to the metal plate 3.
Since it can be produced simply by covering it with 1, 41, it is effective in production.

In the fuel cell 1, the electrical insulation is remarkably improved by eliminating factors in the cell frame structure which are considered to be a cause of the decrease in insulation. That is, in the present fuel cell 1, the end plates 3,
4 is a long screw 11 on the outside of the battery stack 2
a ... so that the end plates are completely electrically isolated from each other,
The possibility of short-circuit between them is avoided, and the manifolds 5 to 8 are pressed and fixed by the band 12, so that they are also electrically isolated, so that the possibility of short-circuit between the manifolds is completely eliminated. Be avoided.

The reason why the insulating layer is formed on a part of the end plate as described above is that there is usually the highest possibility that the battery stack and the manifold are short-circuited by using the end plate as a bypass. (Other Matters) (1) The end plate formed by covering the film sheet with the plate body is not limited to the fuel cell having the cell framework structure as described above. The present invention can be similarly implemented even with another frame structure in which each manifold is fixed by screws. In this case, the effect of improving the electrical insulation by the end plate is obtained in the same manner, but other electrical insulation is more remarkable than the fuel cell 1, such as the possibility that the manifolds may be electrically short-circuited. It cannot be expected that such an effect can be expected.

(2) The end plates 3 and 4 cover the film sheet structures 32 and 42. However, the present invention is not limited to this. The configuration may be as follows. In addition,
The film sheet can be pressed against the metal plates 31 and 41 by a hot press method or the like. (3) In the above description, the fuel cell is provided with a manifold for supplying and discharging both air and hydrogen. However, it is a matter of course that the present invention can be applied to a fuel cell having only a manifold for supplying and discharging hydrogen. .

(4) Further, although the description has been made by taking the phosphoric acid type fuel cell as an example, it is needless to say that the present invention is not limited to this, and the present invention is similarly applied to other fuel cells such as a polymer electrolyte fuel cell. Can be implemented.

[0023]

As described above, in the fuel cell of the present invention, a substantially rectangular parallelepiped cell stack in which a plurality of unit cells are stacked is tightened from above and below in the stacking direction via an end plate. In a fuel cell in which a reaction gas supply / discharge manifold is arranged on a side surface of a stack, the end plate is formed by coating a metal plate with an insulating film. Since at least a portion of the plate body facing the battery stack and a portion facing the manifold are formed, no pinholes are formed in the insulating layer of the end plate, and the electrical insulation is excellent.

[Brief description of the drawings]

FIG. 1 is an assembly diagram of an end plate in a phosphoric acid fuel cell according to an embodiment.

FIG. 2 is a sectional view in the stacking direction of the phosphoric acid type fuel cell according to the embodiment.

FIG. 3 is a perspective view showing the appearance of the phosphoric acid type fuel cell according to the embodiment.

FIG. 4 is an assembly view of the phosphoric acid type fuel cell.

FIG. 5 is an assembly view showing a configuration of a cell stack in the phosphoric acid type fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Phosphoric acid type fuel cell 2 Battery stack 3, 4 End plate 5-8 Manifold 9, 10 Beam material 11a Long screw 11b Nut 31,41 Metal plate 32,42 Film sheet structure

Claims (1)

[Claims] 1. A substantially rectangular parallelepiped battery stack in which a plurality of single cells are stacked is fastened from above and below in the stacking direction via an end plate, and a reaction gas supply / discharge manifold is arranged on a side surface of the battery stack. In the fuel cell, the end plate is formed by coating a metal plate with an insulating film, and the coating with the insulating film includes at least a portion of the plate that faces the cell stack and a manifold. Characterized in that the fuel cell is formed on a portion facing the fuel cell.