JPS63128562A - Fuel cell - Google Patents

Abstract

PURPOSE:To increase the thermal conductivity of a cooling plate, and to improve the cooling performance and efficiency, by composing the cooling plate in laminating a plate which consists of a plate with a groove processed, mainly of graphite, a cooling pipe buried in the groove, and a conductive adhesive filled in the gap between the cooling pipe and the groove; an expansion graphite sheet; and a glassy carbon. CONSTITUTION:Two sets of a pair of electrodes 2 and 3 are furnished at both sides of an electrolyte layer 1, and a fuel gas is permeated at the rear side of an electrode while an oxidizer gas is permeated at the rear side of the other electrode, to form a unit cell to output the electric energy. And plural unit cells are laminated through plates, cooling plates 30 are furnished at every specific numbers of unit cells, to form this fuel cell. In this case, as the cooling plate 30, first a plate mainly of graphite, in which a cooling pipe 31 with no anticorrosive treatment is buried fully in a groove 42 by using a conductive adhesive, and the outlet and the inlet of the cooling water are set and buried at the position to pick up freely at the outside of a manifold, is formed. Then this plate and a glassy carbon 45 are superposed through a sheet formed with an expansion graphite 46, to make up a cooling plate for this purpose. In such a composition, the cooling performance and efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Object of the Invention) (Industrial Application Field) The present invention relates to a fuel cell, and more particularly to a fuel cell having an improved configuration of a cooling plate having current collection and cooling functions.

(Prior Art) Fuel cells are conventionally known as devices that directly convert chemical energy contained in fuel into electrical energy. This fuel cell usually has a pair of porous electrodes placed with an electrolyte store in between, and a fuel gas such as hydrogen gas is brought into contact with the back surface of one electrode, and an oxidizing gas such as oxygen gas is brought into contact with the back surface of the other electrode. Electrical energy can be extracted from between the two electrodes with high energy conversion efficiency by bringing the agent gas into contact and utilizing the electrochemical reaction that occurs at this time.

By the way, the unit cell of a fuel cell based on the above principle, especially using phosphoric acid as an electrolyte, is constructed as shown in FIG. The entire fuel cell is configured as shown in the figure.

That is, in FIG. 6, the unit cell has ribbed electrodes 2.3 (usually made of carbon material) formed of a porous material and provided with a catalyst on both sides of a matrix 1 impregnated with an electrolyte. Further, the ribbed electrodes 2, 3 have flow passages 4, 5 for fluid fuel or fluid oxidant, respectively, on the opposite side of the catalyst application surface. Furthermore, both ribbed electrodes 2 and 3
A separator 6 is disposed on the back surface opposite to the matrix 1. In this way, matrix 1,
The ribbed electrodes 2 and 3 and the separator 6 are stacked, and in this state, only the openings at both ends of the fluid fuel flow passage and the fluid oxidant flow passage of the ribbed electrodes 2 and 3 are left open, and the end faces of each stack are hermetically sealed. constitute a unit cell.

A plurality of unit cells configured as shown in FIG. 6 are stacked,
As shown in FIG. 7, after being tightened with a predetermined pressure by a fastener 10 in order to obtain electrical continuity between the unit cells, a fuel supply port 11 is inserted into one of the opposing end faces of the stack.
A manifold 12 having a fuel outlet 13 and a manifold 14 having a fuel discharge port 13 on the other side, and a manifold 16 having an oxidizer supply port 15 on one of the opposite end faces and an oxidizer discharge port 15 on the other side. A manifold 18 with an outlet 17 is applied, these manifolds 12.14.16.18
are tightened with bolts or the like to maintain airtightness, thereby configuring the fuel cell device 19. Therefore, according to this fuel cell device 19, when fluid fuel is supplied from the fuel supply port 11, this fuel branches through the flow path 4 of each unit cell and flows while contacting the back surface of the porous ribbed electrode 2, and then the fuel It is discharged from the discharge port 13. Also, oxidant supply port 1
When a fluid oxidizing agent is supplied from 5, this oxidizing agent divides the flow path 5 of each unit cell, flows while corroding the back surface of the porous rear electrode 3, and is then discharged from the oxidizing agent outlet 17. At that time, the fluid fuel and the fluid oxidant are supplied into the porous ribbed electrodes 2 and 3 by diffusion, respectively, to generate electrical energy as a fuel cell. Note that the output terminal is omitted in the figure.

By the way, in the above-mentioned fuel cell, due to the temperature rise due to heat generation in the unit cell part during operation,
Performance decreases due to deterioration of the catalyst layer, increased scattering of electrolyte, etc. For this reason, normally every few unit cells, the 8th
As shown in the figure, a cooling plate 30 is provided to extract heat generated inside the unit cell to the outside, thereby preventing an excessive rise in battery temperature.

On the other hand, this type of cooling plate is required to have high thermal conductivity and electrical conductivity in the stacking direction of the unit cells, as well as phosphoric acid resistance, heat resistance, and dimensional stability. For this reason, mechanical processing is generally performed on graphite resin plates obtained by mixing and molding thermosetting resin and graphite particles, or impermeable graphite plates obtained by impregnating graphite plates with resin to make them impermeable to gas. A cooling plate is formed by embedding and fixing a cooling pipe with a heat conductive adhesive, and then bonding a laminated plate of the same material with a highly conductive adhesive. (For example, JP-A-58-1
66661 > However, in such conventionally used cooling plates that include cooling management, as shown in FIG.
A cooling water main pipe 32 that supplies cooling water to the cooling pipe 31 is provided within a manifold 33. For this reason, the cooling water main tube 32 and the cooling pipe 31 are provided with corrosion-resistant tubes or coatings in order to prevent corrosion caused by the surrounding air inside the battery.

Regarding cooling pipes, in addition to the parts exposed inside the manifold, corrosion-resistant treatment is also applied to the cooling pipes inside the cooling plate to prevent corrosion due to penetration of corrosive substances through the cooling pipe interface. .

This corrosion-resistant treatment layer increases heat transfer resistance and causes a decrease in thermal efficiency of the cooling plate.

In addition, since graphite plates of the same material are used for the laminated plates,
There is a limit to the reduction in the thickness of the laminated plate, and only thick cooling plates can be obtained.

From the above points of view, there has been a desire for a more compact cooling plate with excellent cooling performance.

(Problems to be Solved by the Invention) The present invention was made to solve the above problems, and its purpose is to improve cooling performance and efficiency by increasing the heat conductivity of the cooling plate. The object of the present invention is to provide a fuel cell that is highly reliable and compact by reducing the thickness of the cooling plate.

(Structure of the Invention) (Means for Solving the Problems) In order to achieve the above object, the present invention arranges a pair of electrodes with an electrolyte layer in between, and also injects fuel gas onto the back side of one electrode. Forming a unit cell that outputs electrical energy by flowing an oxidizing gas to the back side of the other electrode,
A plurality of the unit cells are stacked via a plate having a function of preventing mixing of the fuel gas and the oxidizing gas and electrically connecting the unit cells, and a cooling plate is provided for each predetermined number of unit cells. In the fuel cell arranged in the fuel cell, as the cooling plate, a cooling pipe which is not treated with anti-corrosion treatment is buried entirely in the groove using a conductive adhesive,
In addition, a plate mainly made of graphite is installed and buried at a position where the cooling water inlet and outlet can be taken out outside the manifold, and a plate made of graphite is used, which is combined with a sheet obtained by molding expanded graphite from glassy carbon. It is characterized by the following.

(Function) The feature of the invention is that the above-mentioned cooling plate is
Gas impermeability is achieved by impregnating a graphite resin plate obtained by mixing and molding thermosetting resin and graphite particles, or a graphite plate obtained by mixing graphite and a binder, molding, and high temperature treatment. In order to prevent the cooling tube from being substantially exposed to the battery atmosphere gas, the cooling tube is made of a plate mainly made of graphite with grooves for embedding the entire surface of the cooling tube, and the cooling tube does not have a corrosion-resistant layer with high heat transfer resistance. A graphite plate is embedded on the entire inside surface with a highly conductive adhesive, and the inlet and outlet of the cooling pipe is embedded in a position outside the manifold so as not to be exposed to the battery atmosphere gas. By forming a glassy carbon sheet that can be made small in thickness with a sheet made of expanded graphite that can be made small in thickness, the heat transfer resistance of the cooling plate can be made small and the heat transfer resistance can be reduced. The reason is that the thickness in the thermal direction is made smaller. Embodiment Hereinafter, the present invention will be described based on a specific embodiment shown in the drawings.

FIG. 1 is a perspective view showing an example of the configuration of a cooling plate according to the present invention. FIG. 2 is a schematic diagram showing one example of the cooling pipe arrangement of the cooling plate according to the present invention.

In the figure, graphite particles formed using pitch as a binder are graphitized at 2000°C, and then a cooling pipe embedding groove 42 is formed in an impermeable graphite plate 41 of 600 x 700 size impregnated with resin by reducing the pressure. . Next, the cooling pipe is embedded with carbon phenol conductive adhesive 43 to form a plate.

The surface of the embedded surface 44 of this first plate is roughly polished, and a glassy carbon plate 45 of 600 m x 700 seconds and 0.6 mm thick is placed and cooled via an expanded graphite sheet 46 of the same shape and 0.4 m thick. Form a plate. FIG. 3 shows a sectional view of such a cooling plate, and FIG. 4 shows a sectional view of a conventional cooling plate.

Next, the cooling effect, that is, the thermal conductivity, of the cooling plate formed in this manner was examined.

In this case, an insulated container was filled with water with a constant area in the direction of the laminated surface, a cooling plate was immersed in the container, hot water at a constant temperature was flowed through the cooling pipe, and the temperature rise of the water was measured. FIG. 3A shows the case of this embodiment, and FIG. 3B shows the conventional case. It is clear from the figure that the temperature rise in this example is higher than that in the conventional example, indicating that it has high thermal conductivity.

In addition, the sealability of the interface between the embedded part and the mating part was investigated. In this case, when we applied pressure from one side of the cooling pipe piping and measured the convexity of leakage to the opposite side, we found that
Almost no leakage was observed near 00'C, and it was confirmed that the seal had sufficient sealing performance.

Next, Table 1 shows the shape and dimensions of the cooling plate according to this embodiment, and also shows the conventional cooling plate.

[Table 1] As is clear from Table 1, according to this embodiment, the thickness of one cooling plate can be made thinner by about 2 m than the conventional one. This means that in the case of a large-capacity 400-cell stacked battery, if one cooling plate is provided for every 5 cells, the layer height can be reduced by about 160 m compared to the conventional one. It means that it is possible.

On the other hand, Table 2 shows the results of an investigation into the weight reduction of the cooling plate, with respect to the weights of the laminated plate according to the present example, the single-port expanded graphite sheet, and the conventional laminated plate, respectively.

[Table 2] As is clear from Table 2, according to this example, 600X
Approximately 1.69Kf per 700m shaped cooling plate
It is possible to reduce the weight of f. This is explained in 4 above.
This means that in the case of a battery with 00 cell stack, it is possible to reduce the weight by about 136 kg.

Roughly speaking, as a result of conducting a battery power generation test by incorporating one cooling plate of this example into every five unit cells, it was possible to lower the maximum temperature of the cell by 3 to 5°C under the same cooling conditions. It was shown that this cooling effect is significant under higher temperature and higher load operating conditions.

Thus, according to the fuel cell incorporating the cooling plate of this embodiment, unlike the conventional case, the cooling pipe and the cooling water main pipe are not directly exposed to the corrosive atmosphere of the fuel cell, which is the main cause of the increase in their thermal resistance. Since the corroded mortar layer can be omitted, the thermal resistance as a cooling plate can be reduced, and as a result, heat transfer is improved, cooling performance is improved, and high and constant power generation efficiency can be obtained.

Furthermore, since the thickness of the cooling plate can be reduced, the height per certain number of stacked layers in the battery body can be lowered, thereby making it possible to downsize the battery. In general, because the weight of the cooling plate can be made smaller for the above-mentioned reasons, it is possible to reduce the weight of the battery body as a result.

In each of the above embodiments, carbon phenol adhesive was used as the conductive adhesive, but other adhesives other than those mentioned above may be used as long as the adhesive has an adhesive function and a conductive function, such as It may be made of adhesive resin such as epoxy resin.

Further, in each of the above embodiments, an impermeable graphite plate is used as the first plate, but the present invention is not limited to this, and a graphite resin plate as described above may be used.

In addition, the present invention can be implemented with various modifications without changing the gist thereof.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to improve cooling performance and efficiency by increasing the heat conductivity of the cooling plate, and it is extremely reliable, and the device can be made smaller and lighter. We can provide fuel cells.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a cooling plate showing an embodiment of the present invention, FIG. 2 is a schematic diagram of a cooling plate according to the same embodiment,
FIG. 3 is a sectional view of a cooling plate according to the same embodiment, FIG. 4 is a sectional view of a conventional cooling plate, FIG. 5 is a characteristic diagram for explaining the effects of an embodiment of the present invention, and FIG. FIG. 7 is an exploded perspective view showing a unit cell of a fuel cell. 30...Cooling plate 31...Cooling pipe 41...Impermeable graphite plate 42...Groove including cooling management 43...Conductive adhesive 45...Glassy carbon plate 46...Expanded graphite sheet Fig. 2 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8

Claims (5)

[Claims] (1) Arranging a pair of electrodes with an electrolyte layer in between,
A unit cell that outputs electrical energy is formed by flowing a fuel gas on the back surface of one electrode and an oxidizing gas on the back surface of the other electrode, and preventing mixing of the fuel gas and the oxidizing gas. In a fuel cell, a plurality of unit cells are stacked together via a plate having a function of electrically connecting the unit cells, and a cooling plate in which a cooling pipe is embedded is arranged for each predetermined number of unit cells. , the cooling plate is composed of a plate mainly made of graphite with grooves processed, a cooling pipe embedded in the groove, a conductive adhesive filled in the gap between the cooling pipe and the groove, and an expanded graphite sheet. and classy carbon. (2) The fuel cell according to claim (1), wherein the cooling pipe does not include a corrosion-resistant layer in the main heat exchange section. (3) The fuel cell according to claim (1), wherein the conductive adhesive contains one of carbon and silver, or a mixture thereof, as a filler. (4) The fuel cell according to claim (1), wherein the conductive adhesive is made of an adhesive resin such as a phenolic resin or an epoxy resin. (5) The fuel cell according to claim (1), wherein the plate mainly composed of graphite is made of any one of a graphite resin binder, a graphite plate, and resin-impregnated impermeable graphite.