JPS61148770A - Fuel cell lamination body - Google Patents

Abstract

PURPOSE:To apply even pressure onto many cells of a lamination body even when they are piled in a vertical direction by dividing the lamination body into several blocks in the direction of lamination and making it possible to adjust pressure in the direction to the lamination for each block. CONSTITUTION:Respective lamination body blocks 11 are formed by piling unit cells 21 in multiple layers through the interposition of separators 22. Cylinder-shaped bodies 41 installed for respective lamination blocks of the fuel cell lamination body move up or down when the cylinder-shaped bodies 41 are rotated. Consequently, when coil springs 44 can be pressed or expanded so that clamping force working between clamping plates 12 may become at given values, the coil springs 44 can maintain the surface pressure of the lamination body even in the face of deformation of electrolyte layers 25 due to temperature increases.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a fuel cell stack, and in particular to a fuel cell stack that can apply appropriate surface pressure to all unit cells in the stacking direction. Regarding the body.

(Technical background of the invention and its problems) Fuel cells have been known as a relatively highly efficient energy conversion device. A fuel cell consists of a pair of porous and conductive electrode plates, an anode and a cathode, with an electrolyte layer interposed between them. Fuel gas is supplied to the lower side of the anode, and oxidant gas is supplied to the cathode side. DC power is obtained through an electrochemical process. In a fuel cell that uses an electrolyte in a molten state, the electrolyte layer is composed of an electrolyte that is an ion conductor and a holding material for holding the electrolyte. In such fuel cells, the electrolyte, molten at operating temperatures, enters the pores of the anode and cathode, forming a three-phase interface consisting of electrode, electrolyte and reactant gas. Then, when fuel gas is flowed to the anode side and oxidant gas is flowed to the cathode side, the oxidant gas and fuel gas are diffused through the holes of each electrode and reach the three-phase interface, where an electrode reaction occurs. Served.

The ions generated in this reaction flow through the electrolyte and the electrons flow from the conductive electrode through an external circuit.

The electromotive force per unit battery (single cell) generated in such a process is determined electrochemically, and this voltage is generally about 0.8V at most at rated load.

Therefore, in order to obtain a high voltage, it is necessary to connect a large number of single cells in series. Therefore, a fuel cell is generally constructed by stacking a plurality of single cells with conductive separators in between.

By the way, in order to efficiently extract electric power from a fuel cell configured in this way, it is necessary to effectively form a three-phase interface, which is a site for electromotive reactions, and to reduce the resistance of electron movement between the electrodes and the separator, that is, the contact resistance. It is necessary to aim at reducing the These requirements require that the proper tightening of the laminate be done by force;
This can be achieved by generating appropriate surface pressure throughout the stacking direction.

However, if too much surface pressure is applied at this time, the electrolyte will enter the pores of the electrode too much and an effective three-phase interface will not be formed. Moreover, if too much electrolyte enters the pores of the electrode, the electrolyte will be blown out to the outside as the reaction gas flows through, resulting in thinning of the electrolyte and cross-mixing of the oxidizing gas and fuel gas. Both gases are burned, resulting in a significant drop in cell voltage and abnormal heat generation. Also,
Conversely, if the surface pressure is too low, the electrolyte will not enter the pores of the electrode, and an effective three-phase interface will not be formed, and the contact between the electrode and the separator will not be sufficient. Therefore, the contact resistance increases, which also causes a decrease in cell voltage. Therefore, the surface pressure applied to each unit cell of the laminate must fall within a predetermined appropriate range.

Therefore, in order to meet this requirement, conventionally, as shown in the sixth factor, the top and bottom portions of the laminate 1 are tightened by two roots.
．． For example, a method has been adopted in which a mechanism 4 is used to tighten the plate 2.3, and a mechanism 4 is used to tighten the laminate body containing a spring.

However, the conventional fuel cell stack having such a structure has the following problems. In other words, if we take a practical-sized molten carbonate fuel cell as an example, a single cell, which is a stacked unit, weighs several kilograms, and a practical stack weighs 100 kg.
More than one cell is stacked. Its weight in the lower part therefore amounts to several hundred kiloliters.

Furthermore, since cooling plates for cooling the inside of the laminate are generally stacked every few cells, this weight is also added, and the actual surface pressure at the bottom of the laminate considerably exceeds the surface pressure at the top. In such a laminate, when pressure is applied to the entire laminate as in the past, the surface pressure will be different at the top, middle, and bottom of the laminate, and the pressure on any one surface will be different. If an attempt is made to adjust the pressure to an optimum value, the surface pressure in other parts will inevitably become too large or too small, resulting in a problem that local performance deterioration of the laminate will occur.

(Objective of the Invention) This invention was made based on the above-mentioned problem, and its purpose is to ensure that even when a large number of cells are stacked vertically, each layer of the stack is It is an object of the present invention to provide a fuel cell stack that can apply uniform surface pressure to the cells, thereby making it possible to obtain uniform electric energy from each single cell.

[Summary of the invention]

The present invention provides a fuel cell stack in which a plurality of unit cells each having an electrolytic layer interposed between an anode electrode and a cathode electrode are stacked with a conductive separator in between. The present invention is characterized in that it is divided into a plurality of laminate blocks in the stacking direction, and is provided with a laminate surface pressure adjusting means that can adjust the pressure in the stacking direction for each of the laminate blocks.

〔Effect of the invention〕

According to the present invention, the fuel cell stack is divided into a plurality of stack blocks, and each stack block can be tightened with a different force, so that the upper block of the stack blocks is By applying force by tightening the block higher and weakening the force by tightening the block located below, it is possible to equalize the surface pressure of the single cell throughout the fuel cell stack. can. Therefore, according to the present invention, an appropriate three-phase interface can be formed in the entire fuel cell stack, and electric energy can be extracted efficiently.

[Embodiments of the Invention] - Hereinafter, an example gMN of the present invention will be described with reference to the drawings.

Example 1 A fuel cell stack of a molten carbonate fuel cell as shown in FIGS. 1 to 3 was assembled. This fuel cell stack includes the first
As shown in the figure, there are five laminate blocks 11 divided in the stacking direction, 11 of these laminate blocks and the clamps made of conductive material provided at the upper and lower ends are roots 12, and the adjacent clamps are A laminated body surface pressure adjustment mechanism 13 is provided between the plates 12 to adjust the force for mutual tightening.

As shown in FIG. 2, each laminate block 11 is constructed by stacking a plurality of unit batteries 21 with separators 22 in between. The unit battery 21 is constructed by interposing an electrolyte plate 25 between a pair of porous electrode plates made of a nickel alloy, that is, an anode 23 and a cand 24. The electrolyte plate 25 is made by holding a carbonate electrolyte made of a mixture of lithium carbonate and potassium carbonate with a holding material made of lithium aluminate. The separator 22 has a plurality of grooves 26a and 26b extending in directions perpendicular to each other on both sides of a plate-like body formed of a conductive material, and these grooves 268 and 26b are used for oxidizing gas Q and fuel gas P, respectively. This is a flow path.

The tightening base 12 has a rectangular shape as a whole, and has arm portions 21 integrally protruding from the four corners thereof extending in a diagonal direction. A hole 28 is formed at the tip of the arm portion 27 for attaching a layered body surface pressure adjustment mechanism 13, which will be described later.

The laminated body surface pressure adjustment mechanism 13 is interposed in these arm portions 21M, and specifically, a connecting rod 31 configured as shown in FIG. The lower end side from the intermediate bright part 33 is formed into a threaded part.
34. This connecting rod 31 has a threaded portion 34 inserted into the hole 28 of the arm portion 27, and a nut 35 screwed into the threaded portion 34. The arm portion 27 is held between a ring portion 33 and tightened. It is fixed at 12. ,In addition,
"Since the connecting rod 31 is a conductive member, insulating material made of alumina is used between the bright part 33 and the arm part 21 and between the nut 35 and the arm part 27 in order to achieve electrical insulation in the stacking direction." A seat 36."37 is interposed. Then, -
The connecting rods 31 that are in contact with each other are connected by a cylindrical body 41 that adjusts the tensile force between them. This cylindrical body 41 has coaxial holes 42 and 43 at both ends, and a thread is formed in the coaxial hole 42 at the upper end into which the thread 34 of the upper connecting rod 31 can be screwed. On the other hand, the lower connecting rod 3
1 is loosely inserted into the coaxial hole 43 at the bottom of the cylindrical body 41, and the flange 32 at the top thereof is disposed inside the cylindrical body 41. A coil spring 44 is interposed between the flange 32 and the inner surface of the lower end wall of the cylindrical body 41.

In the fuel cell stack constructed in this manner, the cylindrical body 41 is moved up and down in the figure by rotating the cylindrical body 41 provided for each stacked body block.

As a result, the coil spring 44 is compressed or expanded, and the tightening force of the roots 12I11 can be set to an arbitrary value. It acts to maintain constant surface pressure on the body.

In this example, 20 unit batteries were used as the laminate block 11, resulting in a laminate of 100 cells in total.

Since the weight of 20 cells was approximately 10 lj, the tightening force by the laminate surface pressure adjustment mechanism 13 was 1 in order from the top in the figure.
The pressure was set to decrease by approximately 25 lf for each laminate surface pressure adjustment mechanism.

Example 2 A fuel cell stack of a molten carbonate fuel cell as shown in FIG. 4 was assembled. This fuel cell stack includes a split block 51 configured by arranging clamping roots 12 on each end face of the stack block 11, and tightening both clamping plates 12 with a stack surface pressure regulator 41113. They are constructed by laminating them with conductive plates 52 in between. Each divided block 51 has a block connecting mechanism 5 inserted between the arm portions 21 of the plate 12 for tightening adjacent blocks.
Connected by 3.

This block connection mechanism 53 also has substantially the same structure as the laminate surface pressure adjustment mechanism 13 described above.

In this case, the weight of one block is approximately 100Kg.
Therefore, the tightening pressure by the laminate surface pressure adjustment mechanism 13 is 60 kg from the top so that the pressure decreases by about 25 kg per adjustment mechanism from the upper divided block 51.
A power generation test was performed by tightening with a force of 0.500.400.300.200 Kg. As a result, the variation in single cell voltage was 4%.

On the other hand, for comparison, a 570-layer molten carbonate fuel cell stack having the adjustment mechanism of Example 2 was used, and 8oo Ky (each When a power generation test was conducted with a tightening force of 20 (Ig) per mechanism, the variation in single cell voltage of the laminate was 7%.

From the above results, it was confirmed that the fuel cell stack of Example 2 was able to extract electrical energy more uniformly and efficiently in the stacking direction than the conventional fuel cell stack.

The above is an example in which the present invention is applied to a molten carbonate fuel cell, but the present invention can also be applied to other fuel cells, such as a phosphoric acid type, that have a structure in which a plurality of single cells are vertically stacked. Needless to say. In addition to being able to adjust the tightening force for each stacked block, the stacked body surface pressure adjustment mechanism may be configured to be able to adjust the tightening force for the entire stack.

Further, as shown in FIG. 5, for example, a coil spring 60 housed inside the case 41 is configured to apply a predetermined spring force in the compression direction and the tension direction to the connecting rods 31 connected to each other. Also good. With such a configuration, it is less susceptible to thermal deformation of adjacent blocks. In addition, the configuration of the layered body surface pressure adjustment mechanism can be modified and implemented in various ways without departing from the gist of the present invention. ”

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a molten carbonate fuel cell stack according to a first embodiment of the present invention, FIG. 2 is a perspective view showing the structure of a part of a stack block of the same stack, and FIG. 4 is a perspective view of a molten carbonate fuel cell stack according to a second embodiment of the present invention, and FIG. 5 is a sectional view showing a stack adjustment mechanism of the same stack. FIG. Partial sectional view showing a modification, No. 6
The figure is a perspective view of a conventional fuel cell stack. 1... Laminated body, 2, 3, 12... Tightening is a plate, 4, 1
3゜53... Laminated body surface pressure adjustment mechanism, 11... Laminated body block, 21... Unit battery, 22 Separator, 23
... Anode, 24... Cathode, 25... Electrolyte plate, 21... Arm portion, 31... Connection rod, 41...
...Cylindrical body, 44. Go...Coil spring, 5
1...Divided block, P...fuel gas, Q...oxidizer gas. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 6

Claims (4)

[Claims] (1) In a fuel cell stack in which a plurality of unit cells each having an electrolyte layer interposed between an anode and a cathode are stacked with conductive separators in between, the fuel cell stack is stacked in the stacking direction. 1. A fuel cell stack which is divided into a plurality of stacked blocks and further comprises a stacked body surface pressure adjusting means capable of adjusting the pressure in the stacking direction for each of the stacked blocks. (2) The fuel cell stack according to claim 1, wherein the stack surface pressure adjusting means is also capable of adjusting the surface pressure of the entire fuel cell stack. (3) The laminate surface pressure adjusting means applies a higher pressure to a laminate block located at an upper position in the stacking direction of the fuel cell laminate among the laminate blocks. 2. The fuel cell laminate according to item 1. (4) The fuel cell stack according to claim 1, wherein the stack surface pressure adjusting means applies pressure by the elastic force of a spring.