JPS61253766A - Fuel cell - Google Patents

Abstract

PURPOSE:To produce a fuel cell which has stable performance over a long period by using a cooling plate which is made by superimposing the first plate in which cooling tubes are buried and the second plate upon each other through a fluoride grease and a fluorine-containing resin tape applied to the peripheries of the facing surfaces. CONSTITUTION:A nonpermeable graphite plate 16 with a size of 600X700 is prepared by graphitizing a molded plate, composed of graphite particles and pitch used as a binder, at 2,000 deg.C and then impregnating the graphitized plate with a resin under reduced pressure. Next, after grooves 17 are formed on the plate 16, cooling tubes 13 are buried and fixed in the grooves 17 by the use of a carbonic epoxy conductive adhesive 18. Next, a fluoride grease 19 is applied to the periphery of the upper surface of the plate 16 and a raw PTFE tape 20 used as a fluorine-containing resin tape is placed on the periphery. After that, an over plate 21 is superimposed on the plate 16, thereby making a cooling plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel cell, and more particularly to a fuel cell having an improved structure of plates having current collecting and cooling functions.

[Technical background of the invention]

Conventionally, fuel cells (hereinafter simply referred to as batteries) have been known as devices that directly convert chemical energy contained in fuel into electrical energy.

This battery usually has a pair of porous electrodes with an electrolyte layer in between, and the back of one electrode is contacted with a fuel gas that supplies hydrogen gas, and the back of the other electrode is contacted with a fuel gas that supplies hydrogen gas. By bringing oxidized 1i11J gas into contact and utilizing the electrochemical reaction that occurs at this time, electrical energy can be extracted from between both electrodes with high energy conversion efficiency.

By the way, based on the above principle, especially phosphoric acid (H3PO
A unit cell constituting a battery using 4) as an electrolyte is formed as follows. That is, as shown in FIG. 3, the unit cell is formed of carbon porous material on both sides with an electrolyte layer (hereinafter referred to as matrix) 1 impregnated with an electrolyte as a boundary, and a catalyst layer 2.2a is formed on each side of the matrix 1. An additional pair of electrodes 3.3a is provided. Furthermore, both electrodes 3°3a
A plate 5 (hereinafter referred to as an interconnector) having a rib 4 serving as a groove and a convex portion is disposed on the back side of the matrix 1 . On the surface of the interconnector 5 located on the electrode side, a plurality of parallel grooves are formed by the ribs 4 in directions perpendicular to each other. A groove 7 on one side of the interconnector 5 serves as a flow path for fuel gas, and a groove 8 formed in an orthogonal direction on the other side serves as a flow path for oxidizing gas. A plurality of unit cells are stacked via the interconnector 5 formed in this manner, current collecting plates are arranged at the upper and lower ends thereof, and further, insulating and tightening members are brought into contact and tightened together. A battery stack is formed using j.

Then, as shown in FIG. 4, reaction gas supply containers (hereinafter referred to as manifolds) are arranged on mutually opposing surfaces of this battery stack. One opposing manifold 9,9
8 for supplying and discharging fuel gas, and the other opposed manifold 10.10a supplying and discharging oxidizing gas;
In this way, an interconnector-type battery is constructed in which both gases are made to flow through the respective grooves of the interconnector 5 described above.

There are other batteries with ribbed electrodes. As shown in FIG. 5, the interconnector 5 described above is divided into a separator 11 and a rib 4.

That is, ribbed electrodes 12, 12a having catalyst layers 2.degree. 2a formed thereon are arranged on both sides of the matrix 1 to form a unit cell. Then, grooves 78 and ribs 4 are formed on the opposite side of the one-knob electrode 1212a that is in contact with the matrix 1,
In the direction perpendicular to the grooves 7, 8 and 1 knob 4 of both electrodes, form I1. SatL te 1/'6;-t is similar to the interconnector. When stacking a plurality of unit cells, they are stacked with a plate, that is, a plate-shaped separator 11 interposed therebetween, to prevent mixing of both gases, and a battery stack is formed in the same manner as described above. A manifold is attached to each to form a ribbed electrode type battery.

In the interconnector type and ribbed electrode type batteries configured as described above, performance decreases due to deterioration of the catalyst layer due to temperature rise due to heat generation in the unit cell portion during operation. Therefore, in order to prevent this, in interconnector type batteries, cooling pipes 13 are connected to the interconnector 5 every several unit cells, as shown in FIG.
An interconnector-type cooling plate 14 in which is embedded is provided. In addition, in the case of a ribbed electrode type battery, as shown in FIG.
5 will be placed. In this way, 1. The heat generated inside the unit cell is taken out to the outside to prevent the battery temperature from rising excessively.

[Problems with background technology]

By the way, both the interconnector type and separator type cooling plates described above have excellent thermal conductivity and electrical conductivity in the stacking direction of the unit cells, and are also required to have phosphoric acid resistance, heat resistance, and dimensional stability. be done. For this reason, cooling pipes are generally made of a material with high heat conductivity by machining a plate made of a mixture of thermosetting resin and graphite particles, or a graphite plate impregnated with resin to make it impermeable to gas. It is formed by embedding, and then bonding the entire surface of a laminated board made of the same material with a highly conductive adhesive.

However, since battery operation involves repeated startup and shutdown cycles, this inevitably causes the adhesive used for bonding to peel off, resulting in a decrease in electrical conductivity and
Localization of electrically conductive parts, and leakage and mixing of reaction gases from the separation space may cause heat generation in the battery, which may result in a decrease in efficiency and life of the battery.

[Purpose of the invention]

The present invention was made to solve the above-mentioned problems, and its purpose is to provide a long-term, long-term, stable performance that is unaffected by the start-stop cycle of operation. Our goal is to provide long-lasting batteries.

[Summary of the invention]

In order to achieve the above object, the present invention disposes a pair of electrodes with an electrolyte layer in between, and flows fuel gas to the back surface of one electrode and oxidant gas to the back surface of the other electrode to generate electrical energy. A plurality of unit cells are stacked together via a plate having a function of preventing mixing of the fuel gas and the oxidant gas and electrically connecting the unit cells, and cooling the unit cells. In a fuel cell in which a cooling plate with embedded tubes is arranged for each of the predetermined number of unit cells, the cooling plates include a first plate and a second plate with embedded cooling tubes,
It is characterized in that the periphery of the overlapping surfaces is formed by overlapping them with fluorine grease and fluororesin tape interposed therebetween.

[Embodiments of the invention]

First, the characteristics of the present invention are that the above-mentioned cooling plate is made of a graphite resin plate obtained by mixing a thermosetting resin and graphite particles and molding it, or a graphite resin plate obtained by mixing graphite and a binder, molding it, and treating it at high temperature. The impermeable graphite plate is impregnated with resin to make it impermeable to gas, and grooves are cut for cooling management, and cooling pipes are embedded in a material with high heat conductivity, and the area around the overlapping surfaces is By placing a fluorine-based grease whose main ingredients are fluorine-based oil and fluororesin particles and a fluorine-based resin tape on the part, and forming a plate of the same quality on top of it, the start/stop cycle of battery operation can be easily controlled. The present invention is designed to prevent a decrease in electrical conductivity due to peeling of the adhesive and to prevent leakage and mixing of reactive gases from the peeled interface. In particular, for interconnector type cooling plates,
A cooling plate is formed by processing a plate with reactive gas flow passages formed thereon in the same manner as described above, and overlapping a plate of the same quality on which a reaction gas flow passage is formed.

The present invention will be described below based on a specific embodiment shown in the drawings. FIG. 1 is an exploded perspective view showing an example of the configuration of a cooling plate according to the present invention. In the figure, the graphite particles molded using pitch as a binder are 2000
600X graphitized with 'C and impregnated with resin under reduced pressure
Grooves 17 for embedding cooling pipes are formed in a 700-hole impermeable graphite plate 16. Next, the cooling pipe 13 is embedded in the cooling immediate management groove 17 using a carbon epoxy conductive adhesive 18 and hardened and fixed. Then, as shown in the figure, a fluorine-based grease 19 having the composition shown in the table below is applied to the surrounding area, and a raw PTFE (7) tape (
12 (width - 0, 1 length) 20 are arranged, and an upper plate 21 is superimposed thereon to form a cooling plate.

FIG. 2 shows a cross-sectional view of such a cooling plate.

〔table〕

Next, the cooling plate according to this example was used for starting battery operation.
Simulating a shutdown, a heat cycle test was conducted from room temperature to 180'C to examine changes in the electrical conductivity of the cooling plate. In this case, the tightening pressure is 2, OKg/ci
I did it. For reference, test results of a conventional cooling plate bonded with silver epoxy are also shown in FIG. 6s in the figure, the horizontal axis shows the number of heat cycles, and the vertical axis shows the respective ratios when the initial electrical resistance of the cooling plate according to this embodiment is set to 1. From the figure, it can be seen that the electrical resistance A of the cooling plate according to this embodiment hardly changes due to heat cycles, whereas the electrical resistance of the conventional adhesive cooling plate increases.

On the other hand, we investigated gas leaks from the surface where the cooling plates were attached. In this case, pressure is applied to the two opposing end surfaces at the same time, and the amount of leakage from the two orthogonal end surfaces is determined and the result is
Shown in the figure. In the figure, the horizontal axis shows the number of heat cycles, and the vertical axis shows the leakage amount (-) per unit orthogonal surface length (ym) per hour when the differential pressure is 100 mlA. A in the figure shows the results of the cooling plate according to this example, and the leakage amount was 0.025 to 0.030 m1'/hrs+100 shoes A7, and almost no change was observed due to the heat cycle. In contrast, the conventional cooling plate 8 in the figure
Even at the initial stage, it shows a value of 0.08 ae/hrgloosA9, which is higher than that of the cooling plate of this example, and it can be seen that the amount of leakage further increases with heat cycling.

Thus, according to the battery incorporating the cooling plate of this example, the electrical conductivity decreases less than that of the conventional cooling plate bonded using an adhesive, so that the bonding interface of the cooling plate due to operation does not deteriorate. There is no increase in ohmic loss,
Furthermore, there is no decrease in cooling efficiency due to an increase in thermal resistance, and as a result, a high and constant power generation efficiency can be obtained. In addition, there is less leakage and mixing of reactant gas from the overlapping surfaces of the cooling plates, less heat generation due to combustion on the battery catalyst, and as a result less scattering of the electrolyte due to overheating, resulting in stable operation over a long period of time. be able to.

In the above embodiment, a mixture of fluorinated oil and perfluoroalkoxy resin (PFA) particles was described as the fluorinated grease, but the mixed particles may be PTFE particles or mixed particles of PTFE and PFA. Furthermore, the same effect as described above can be obtained with a mixture of phosphoric acid-resistant particles such as silicon carbide and the above-mentioned fluorine-based particles.

In addition, the present invention can be modified and implemented in various ways without changing the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, a pair of electrodes are arranged with an electrolyte layer in between, and a fuel gas is supplied to the back surface of one electrode, and an oxidizing gas is supplied to the rear surface of the other electrode. A plurality of unit cells are connected through a plate having a function of forming a unit cell that outputs electrical energy by circulating each unit cell, preventing mixing of the fuel gas and the oxidizing gas, and electrically connecting the unit cells. In a fuel cell in which cooling plates are individually stacked and have cooling pipes buried in each of the predetermined unit cells, the cooling plates include a first plate and a second plate in which cooling pipes are buried. of,
The grooves are formed around the overlapping surfaces using fluorine-based grease and fluororesin tape, which are overlapped to form a groove, so it is stable over a long period of time without being affected by the start-stop cycle of operation. It is possible to provide a long-life, extremely reliable battery that can achieve high performance.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing a cooling plate according to an embodiment of the present invention, FIG. 2 is a sectional view showing a cooling plate according to the same embodiment, FIG. 3 is an exploded perspective view showing a unit cell of a battery, and FIG. The figure is a perspective view showing a battery incorporating the same unit cell.
Figure 6 is an exploded perspective view showing the unit cell of the battery, Figure 6 is an exploded perspective view showing the cooling plate and unit cell, Figure 7 is an exploded perspective view showing the cooling plate and unit cell, Figures 8 and 9 are FIG. 3 is a characteristic diagram for explaining the present invention in detail. 14... Interconnector type cooling plate, 15...
・Separator type cooling plate, 16...Graphite plate, 19
... Fluorine grease, 20... PTFE raw tape, 21... Upper plate. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3; Figure 4 A Figure 5 Figure 6 V Figure 7 Figure 8 Number of heat tests □ Figure 9

Claims (7)

[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 to the back surface of one electrode and an oxidant gas to the back surface of the other electrode, thereby preventing mixing of the fuel gas and the oxidizing gas, and preventing the mixing of the fuel gas and the oxidizing gas. A fuel cell in which a plurality of unit cells are stacked via plates 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 formed by overlapping a first plate and a second plate in which cooling pipes are embedded with fluorine-based grease and fluorine-based resin tape interposed in the periphery of the overlapping surfaces. A fuel cell characterized by: (2) The fuel cell according to claim (1), wherein the fluorinated grease uses fluorinated oil as a solvent. (3) The fuel cell according to claim (1), wherein the fluorine-based grease contains at least one of tetrafluoroethylene and perfluoroalkoxy resin particles as a thickener. (4) The fluorine-based grease contains, as a thickener, at least one of tetrafluoroethylene particles or perfluoroalkoxy resin particles, and at least one of silicon servite, titanium oxide, or zirconium oxide particles. Claim No. 1 characterized in that (
The fuel cell described in section 1). (5) The fuel cell according to claim (1), wherein the cooling plate is an interconnector-type cooling plate in which grooves are formed to serve as flow paths for fuel gas and oxidizing gas. (6) The fuel cell according to claim (1), wherein the cooling plate is a separator type cooling plate. (7) The fuel cell according to claim (1), wherein the fluororesin tape is made of tetrafluoroethylene or perfluoroalkoxy resin.