JPH11204129A - Layer built fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell which is pressurized and held by a compact and inexpensive clamping member and which can be operated without being damaged, even the if receiving a heat cycle generated is received which accompanies the repetition of generating operation. SOLUTION: In this layer built fuel cell, in which clamping plates 1 comprising a metal material are installed at both ends of a cell laminate 4 consisting of stacking single cells 2 together with properly inserted cooling plates 3, and which is clamped, pressurized and held by springs 7 and clamping studs 8, expanding graphite sheets 5, which are conductive lubricating members, are inserted between the cell laminate 4 and the clamping plates 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stacked fuel cell mainly using phosphoric acid as an electrolyte, and more particularly to a fastening structure thereof.

[0002]

2. Description of the Related Art FIG. 3 is a partial sectional view showing a fastening structure of a conventional laminated fuel cell. In the figure, cell 2
In general, a matrix comprising phosphoric acid as an electrolyte is sandwiched between two electrodes, and a separator provided with a reaction gas flow passage is provided on the outer surface thereof. Since the generated voltage obtained by one unit cell 2 is a low voltage of less than 1 V, a method of increasing the generated voltage by stacking a plurality of unit cells 2 and connecting them in series has been adopted for practical use. ing. When the power generation operation is performed, heat is generated due to the electrochemical reaction. Therefore, when a large number of cells 2 are stacked, the cooling plate 3 for removing the heat and maintaining the predetermined temperature is maintained.
Are inserted as needed. For this reason, as shown in the figure, a battery stack 4 is formed by alternately stacking a stacked block in which a plurality of unit cells 2 are stacked with a cooling plate 3 having a built-in cooling pipe 3a for cooling water distribution. Is common.

[0003] In the battery stack 4 configured as described above, the contact resistance between the single battery 2 and the single battery 2 and between the single battery 2 and the cooling plate 3 is reduced to reduce the contact resistance between the single battery 2 and the cooling plate 3. In order to suppress the internal resistance to a low value and maintain the airtightness of the reaction gas supplied to each of the unit cells 2, they are tightened by applying pressure in the stacking direction. In the configuration of FIG. 3, the clamping plates 1 are arranged at both ends in the stacking direction, and the clamping plates 1 are clamped by using the springs 7 and the clamping studs 8, thereby holding the battery laminate 4 in a pressurized state.

In this configuration, the battery stack 4 is
During the power generation operation, the temperature is maintained at about 170 ° C, and when the operation is stopped, the temperature is stored at about 50 ° C. On the other hand, the unit cell 2 and the cooling plate 3 are mainly composed of a carbon member, whereas the fastening plate 1 is made of a steel member having high mechanical strength.
The coefficient of thermal expansion of steel members is about 10 times that of carbon members.
Therefore, if the clamping plates 1 are directly arranged at both ends of the battery stack 4 and tightened, excessive stress is applied by the above-described thermal cycle, and the battery stack 4 will be damaged. To this end, a graphite plate 10 having a sufficient thickness is inserted between the battery stack 4 and the clamping plate 1 as a buffer for stress relaxation. In addition, the sealing member 6 is a fastening plate 1 made of phosphoric acid that is scattered from the cell 2 with the power generation operation.
It is installed to prevent the corrosion of steel.

[0005]

As described above, in the conventional stacked fuel cell, the graphite plate 10 is inserted between the battery stack 4 and the clamping plate 1 and tightened, thereby obtaining the battery stack. 4 is pressurized at a predetermined pressure, and damage due to stress caused by the pressurization is prevented. However, in this method, one surface of the inserted graphite plate 10 is restrained by the battery laminate 4 and the other surface is restrained by the clamping plate 1 having a large thermal expansion. In order to alleviate the stress, the thickness of the graphite plate 10 needs to be sufficiently large. Therefore, there is a problem in that the overall height of the stacked fuel cell is increased, and when the installation height is limited, the number of the unit cells 2 to be stacked must be reduced. There is a disadvantage that the performance must be kept low.

As one of the methods for suppressing the thickness of the member due to the tightening, the tightening plate is made of a metal member having the same coefficient of thermal expansion as the carbon material which is a main constituent member of the battery stack 4, for example, an invar material. Although there is a method of configuring and suppressing the thermal stress caused by the heat cycle, such a member is expensive and a fuel cell using the member is expensive, so that practical use is difficult.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to provide a compact and inexpensive tightening member for effectively holding a battery stack under pressure, thereby reducing a heat cycle accompanying repeated power generation operation. An object of the present invention is to provide a stacked fuel cell which can be safely operated without being damaged even if it is damaged.

[0008]

In order to achieve the above object, the present invention provides a laminated block comprising a plurality of flat unit cells each having an electrolyte layer and two electrodes sandwiching the electrolyte layer. The stacked block is alternately stacked with the cooling plate to form a battery stack.Furthermore, fastening plates made of a metal material are arranged on both end surfaces in the stacking direction of the battery stack, and tightened, and the reaction gas is formed. In a stacked fuel cell that supplies and obtains electric energy by an electrochemical reaction, a lubricating member having conductivity, for example, an expanded graphite sheet, or a fluororesin and graphite powder is provided between the cell stack and the fastening plate. A film or the like formed by mixing is inserted, tightened, and supported by pressure.

As described above, if a lubricating member such as an expanded graphite sheet or a film formed by mixing a fluororesin and graphite powder is inserted between the battery laminate and the clamping plate, the lubricating member can be obtained. And the battery laminate, and between the lubricating member and the fastening plate, while maintaining good lubricity. Therefore, even if the stacked fuel cell generates a thermal cycle with the repetition of the power generation operation, even if the battery stack and the fastening plate having different coefficients of thermal expansion repeat thermal expansion and thermal contraction, respectively, the friction coefficient therebetween is small. ,
Since they are deformed in the horizontal direction without being substantially restrained by each other, the thermal stress due to the restraint is slightly suppressed. For this reason,
The battery stack operates safely without damage due to thermal stress. Further, the lubricating member may be a member having an extremely small thickness such as a sheet or a film. Therefore, the required thickness is greatly reduced as compared with the graphite plate used in the conventional fuel cell, and the fuel cell can be made compact. Further, in the case of fuel cells having the same height, the number of stacked unit cells can be increased, and it is possible to obtain more excellent characteristics.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <Embodiment 1> FIG. 1 is a partial sectional view showing a fastening structure of a first embodiment of a stacked fuel cell according to the present invention. In this figure, components having the same functions as those of the conventional configuration shown in FIG. 3 are denoted by the same reference numerals, and redundant description will be omitted.

This embodiment is characterized in that an expanded graphite sheet 5 which is a conductive lubricating member is provided between the battery laminate 4 and the clamping plate 1 instead of the graphite plate 10 of the conventional example (FIG. 3). That it is inserted. As in the present configuration, the battery stack 4
Even when the battery stack 4 is fastened and held in the stacking direction by the method of fastening between the fastening plates 1 arranged at both ends by the spring 7 and the fastening stud 8, the expanded graphite sheet 5 having lubricity is inserted. Therefore, the coefficient of friction between the battery stack 4 and the fastening plate 1 is small, and the battery is held without restraining each other with respect to a change in the relative position in the horizontal direction. Therefore, even if the thermal cycle occurs due to the repetition of the operation and the stop, and the horizontal position of the clamping plate 1 and the battery stack 4 changes due to the difference in the coefficient of thermal expansion, the frictional force generated between the two increases. Expanded graphite sheet 5 with lubricity
, Expansion and contraction occur without any horizontal stress between the two, and there is no risk of damage due to thermal stress. The expanded graphite sheet 5 is
It is literally formed in a sheet shape, and a sufficiently small thickness of 1/10 to 1/100 of the thickness of the graphite plate 10 used in the conventional example can sufficiently function. Therefore, the fuel cell using this is compactly configured and the material cost is reduced. For devices with limited space,
Since the unit cells 2 can be added to the reduced space by employing the expanded graphite sheet 5, a stacked fuel cell exhibiting more stable cell characteristics can be obtained.

<Embodiment 2> FIG. 2 is a partial sectional view showing a fastening structure of a second embodiment of the stacked fuel cell according to the present invention. The feature of this embodiment is that a film 9 of a conductive lubricating member formed by mixing a fluororesin and graphite powder is inserted between the battery laminate 4 and the clamping plate 1 so that the battery laminate is tightened. It is being done.

Since the film 9 having this structure also has lubricity, the coefficient of friction between the battery laminate 4 and the clamping plate 1 is small, as in the case of the expanded graphite sheet 5 of the first embodiment. The position change is held without restraining each other. Therefore, even if the battery is subjected to a thermal cycle due to repeated operation and stoppage, no horizontal stress is generated between the battery laminate 4 and the fastening plate 1, so that the battery laminate 4 is not likely to be damaged. In addition, the film 9 having this configuration
Is also very thin like the expanded graphite sheet 5 of the first embodiment, so that the fuel cell using this becomes compact,
Material costs are also reduced.

Since the fluororesin constituting the film 9 has water repellency, as shown in FIG. 2, by continuously arranging the film 9 on the side surface of the clamping plate 1, Corrosion of the fastening plate 1 due to phosphoric acid is prevented. That is, the present film 9 simultaneously fulfills the function of the seal member 6 for preventing corrosion used in the conventional example or the first embodiment.

[0015]

As described above, in the present invention, a laminated block is formed by laminating a plurality of flat unit cells each having an electrolyte layer and two electrodes sandwiching the electrolyte layer, and forming the laminated block. A battery stack is formed by alternately stacking with a cooling plate, and a fastening plate made of a metal material is arranged at both ends in the stacking direction of the battery stack and fastened. In the stacked fuel cell obtained, a lubricating member, for example, an expanded graphite sheet, or a film formed by mixing a fluororesin and graphite, etc. is inserted between the cell stack and the clamping plate, and tightened.
Since it is pressure-supported, it can be effectively held under pressure by a compact and inexpensive tightening member, and can be safely operated without damage even if subjected to thermal cycles accompanying repeated power generation operation. Type fuel cell was obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a fastening structure of a first embodiment of a stacked fuel cell according to the present invention.

FIG. 2 is a partial cross-sectional view showing a fastening configuration of a second embodiment of the stacked fuel cell according to the present invention;

FIG. 3 is a partial cross-sectional view showing a fastening structure of a conventional stacked fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tightening plate 2 Single cell 3 Cooling plate 3a Cooling pipe 4 Battery stack 5 Expanded graphite sheet 6 Sealing material 7 Spring 8 Tightening stud 9 Film

Claims (3)

[Claims] 1. A battery stack comprising a plurality of flat cells each having an electrolyte layer and two electrodes sandwiching the electrolyte layer, forming a laminated block, and laminating the laminated blocks alternately with a cooling plate. A stacked fuel cell in which a body is formed, and furthermore, fastening plates made of a metal material are arranged at both ends in the stacking direction of the battery stack and tightened, and a reaction gas is supplied to obtain electric energy by an electrochemical reaction. A stacked fuel cell, wherein a lubricating member having conductivity is inserted between the body and the fastening plate. 2. The stacked fuel cell according to claim 1, wherein said lubricating member is an expanded graphite sheet. 3. The stacked fuel cell according to claim 1, wherein the lubricating member is a film formed by mixing a fluororesin and graphite powder.