JPH0381973A - Fuel cell - Google Patents

Abstract

PURPOSE:To form a bypass current passage easily by stacking a plurality of semi-blocks with an insulating sheet interposed, wherein each semi-block is formed from a certain number of unitary cells piled up between a pair of electro-conductive plates, and coupling the electro-conductive plates sideways. CONSTITUTION:Insulated from each other with an insulating sheet 22 interposed, a plurality of semi-blocks 11 are stacked while pinching a cooling plate 6A in between. Thus a cell stack 20 is formed. Each semi-block is formed from a plurality of unitary cells piled one over another, and above and below it a pair of electro-conductive plates, for ex. 23A, 23B, are furnished, and the electro-conductive plate 23A and cooling plate 6B are insulated with the mentioned insulating sheet 22. In case the unitary cells are free of failure, the electro-conductive plates of adjoining semi-blocks are connected with each other, and normal current collecting operation is made. In case one of the unitary cells is in failure, the electro-conductive plates of the applicable semi-block are removed, and the electro-conductive plates of the semi-blocks before and after it are connected through a connection conductor 31 to form a bypass current passage 31 simply.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel cell comprising a stack of unit cells including a matrix holding an electrolyte, and having cooling plates stacked for each of a plurality of unit cells. When a deteriorated cell battery occurs,
The present invention relates to a fuel cell whose bypass current path can be easily formed.

[Conventional technology]

FIG. 4 is a schematic side view of a cell stack showing a conventional structure. The cell stack 1O is composed of a stack of single cells 1, which are mounted on ribbed electrode base materials with a matrix 2 holding phosphoric acid as an electrolyte sandwiched between them. Cells 1 having oxidizer electrodes 3 and fuel electrodes 4 carrying electrode catalyst layers and gas-impermeable separate plates 5 are stacked alternately, and a cooling plate 6 is interposed between each plurality of cells, Current collector plates 7 are provided at both ends in the stacking direction. A unified cell stack 10 is formed by arranging wA green root plates 8 and clamping plates 9 and applying a clamping load between the pair of upper and lower clamping plates 9.

Note that the PANA lock 11 of a plurality of single cells stacked between cooling plates will be referred to as a semi-block here.

A manifold (not shown) is attached to the side surface of the cell stack 1o configured in this way, and an oxidizer passage 3A defined between the unit cell 1 and the separate plate 5, and an oxidizer passage 3A defined on the fuel electrode 4 side. Power generation operation is performed by supplying oxidizing gas and fuel gas to the fuel gas passages, respectively.

By the way, if even one of the many single cells that make up the cell stack 10 during power generation operation deteriorates due to lifespan or damage, not only will the electrical output of the cell stack as a whole decrease, but also depending on the operating conditions at that time. A so-called potential reversal phenomenon occurs in the deteriorated single cell, and it deviates from the range where it can operate as a battery, causing electrolysis. In this state, oxygen is generated on the fuel electrode 4 side and hydrogen is generated on the oxidizer electrode side. This creates an extremely dangerous situation where oxygen and hydrogen react directly. As a means to prevent such a situation, as shown in FIG. 4, a shorting member 16 made of a conductive material is screwed to the electrode base material of the pair of electrodes 3 and 4 using mounting screws 17 on the end face of the deteriorated cell 1A. A fuel cell in which a short circuit 15 is formed is known (see Utility Model Publication No. 63-31484) [Problem to be solved by the invention] The conventional short circuit structure has an electrode base material made of a carbon plate having gas permeability. The short circuit 15 is formed by using the contact surface between the electrode base material and the mounting screw 17, and the contact surface between the end face of the electrode base material and the short circuit member 16, which are generated by the tightening force of the mounting screw 17, as conductive contact surfaces. Due to the thinness of the material and its low rigidity, it is difficult to obtain sufficient clamping force and conductive contact area. Therefore, when the contact resistance of the conductive contact surface is high and the generated current of the entire stack 10 flows through this contact surface, the potential drop in the short circuit 15 becomes large, and this potential drop is directed against the deteriorated cell IA. Therefore, there is a problem in that it is not possible to sufficiently avoid the phenomenon of reversal of the potential of a deteriorated cell. If power generation operation is continued without sufficiently avoiding the potential reversal phenomenon, the unit cells will be severely damaged due to electrolysis of phosphoric acid and corrosion of the carbon material, and local overheating will occur due to the direct reaction between oxygen and hydrogen, so power generation will be interrupted. The disadvantage is that you cannot continue driving.

An object of the present invention is to provide a fuel cell that can easily form a bypass current path that bypasses the degraded cell without disassembling the cell stack when a degraded cell occurs, thereby preventing the decomposition reaction of the degraded cell. There is a particular thing.

[Means to solve the problem]

According to the present invention, the above-mentioned object has a semi-block, a cooling plate, a pair of conductive plates, and an electrically insulating sheet, the semi-block is a stack of a plurality of single cells, and the cooling plate is an electrically insulating sheet. It is sandwiched between a pair of conductive plates through an insulating sheet, and the pair of conductive plates are laminated alternately with semi-blocks, and the current in the semi-block is transmitted to the other semi-blocks. They are directly connected to each other through conductive connection parts provided in the parts, or one of the conductive plates is indirectly connected to the other conductive plate of the ground pair using a connecting conductor. This is achieved by assuming that

[Effect]

In the above means, a pair of conductive plates made of metal plates sandwiching a cooling plate are stacked in advance on the cell stack with an insulating sheet interposed between them and one surface of the cooling plate, and the pair of conductive plates from 1 to 1 are always stacked. Low electrical resistance that connects conductively to each other on the sides of the cooling plate to form a current path, allowing it to bypass the cooling plate without any effect on the power generation performance of the cell stack when no degraded cells are included. A fuel cell is obtained in which the generated current flows through the current path. In addition, if a deteriorated single cell occurs, the conductive connection between each pair of conductive plates sandwiching all five blocks including the cell is canceled, and the two conductive plates sandwiching the semi-block with an electrically insulating sheet are connected conductively. However, by forming a bypass current path with low electrical resistance that is electrically insulated from the semi-block, the electric current generated by the cell stack is blocked by the electrical insulating sheet from flowing into the semi-block containing the deteriorated cells, and is bypassed. Since it flows through the electrical path without causing a large potential drop, it is possible to completely prevent the potential reversal phenomenon of the deteriorated cell. Furthermore, since the bypass current path can be easily formed simply by changing the connection of the current path, a function that saves labor and time in repair work can be obtained.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a schematic side view of a fuel cell that does not include a deteriorated cell according to an embodiment of the present invention, FIG. 2 is an exploded enlarged view of the main parts of FIG. 1, and FIG. FIG. 2 is a schematic side view of an example device showing an example of application to a fuel cell including a conventional device, and detailed explanation will be omitted by using the same reference numerals for the same parts as in the conventional device. In Figures 1 and 2,
On one side of the cooling plates 6^, 6B, etc. that sandwich the semi-block 11 consisting of only healthy single cells, one conductive plate 23A is attached via a heat-resistant electrical insulating sheet 22 such as a polyamide film. A conductive plate 23 is in contact with the other surface of the cooling plate.
B is laminated in advance when the cell stack 20 is assembled. The conductive plates 23A and 23B are made of metal plates such as anti-corrosion treated copper plates, and both ends thereof are pulled out to the sides of the cooling plate and tightened with tightening members 24 such as bolts and nuts, and the pair of conductive plates 23A .

The ends of 23B are conductively coupled to each other to form a conductive connection portion 25 with low contact resistance.

A pair of current collector plates 7.7 of the cell stack 20, each of which has a current path 21 configured in this manner for each cooling plate, is connected to an external load circuit, and during power generation operation in which the cell stack 20 supplies a load current, The generated current (load current) of the cell stack is collected through the separate plate 5 to a plate 23B, for example, which is in full contact with the unit cell 1, and is then collected again from the conductive plate 23A via the conductive connection part 25 with a large conductive contact area. Since the current flows distributed over the single cells, a current path 21 with low electrical resistance can be easily obtained.

On the other hand, when a degraded cell 1A occurs in the cell stack 20, as shown in FIG.
The tightening bolt 24 is removed, and the conductive plate 23A on the current path 21A side and the conductive plate 23B on the current path 21B side are electrically connected via the connecting conductor 32 using the tightening member 24.

In this state, the semi-block IIA including the cooling plate 6A and two conductive plates has two electrically insulating sheets (22) on both sides.
The semi-block IIA is electrically insulated from the adjacent semi-blocks by A and 22B, and the semi-block IIA is in an electrically open state (loaded state).
, 22B, a bypass current path 31 is formed by the plates 23A, 23B and the connecting conductor 32, and similarly to the current path 21, a low electrical resistance is obtained.

In the power generation operation of the fuel cell according to the embodiment, the generated current flows through the bypass current path 31 with low electrical resistance, and the semi-block LIA is electrically disconnected from the cell stack 20 by two insulating sheets. Since it is insulated from the semi-block IIA, it is possible to completely prevent the generation current from flowing into the semi-block IIA and the potential drop of the bypass current path 31 from being applied to the semi-block IIA. It is possible to almost completely prevent the potential reversal phenomenon, and avoid adverse effects such as characteristic deterioration due to the reversal phenomenon and direct reaction of the reactant gas. Further, when the cell stack 20 is in power generation operation, the reaction gas is also supplied to the semi-block 11^ to cause an electromotive reaction, so the single cells included in the semi-block IIA generate voltage, but the electric insulation sheet (22A) , 22B are in an open state, so no short-circuit current is generated. Note that the generated voltage can be reduced by blocking the reaction gas passage of each cell with a sealant and suppressing the electromotive reaction of the cell. I can do it.

In this way, in the example fuel cell, a bypass that bypasses the semi-block containing the deteriorated single cells can be created by simply reconnecting the ends of the metal conductive plates stacked in advance on the side of the cell stack. Since the current path can be formed easily and firmly, there is no need for large-scale repairs such as disassembling the cell stack and replacing the deteriorated cells with new cells when a deteriorated cell occurs, thus reducing the idle period of the fuel cell. In addition to being able to significantly shorten the time, it is possible to continue operation safely and stably for a long period of time after repair by preventing the potential reversal phenomenon of the deteriorated cell.

〔Effect of the invention〕

As mentioned above, in this invention, a pair of metal conductive plates sandwiching a cooling plate on one side with an electrically insulating sheet interposed between them are laminated in advance in a cell stack, and when all cells are in normal condition, the pair of conductive plates are removably conductively connected at their ends to form a current path, and when a deteriorated cell occurs, the two pairs of current paths arranged on both sides of the semi-block containing it are separated, and the semi-block and the above-mentioned semi-block are connected. was configured to form an electrically isolated bypass current path. As a result, the semi-block containing the deteriorated cell is electrically insulated from the cell stack and the bypass current path, and the current generated by the cell stack flows through the bypass current path with low electrical resistance, which eliminates short circuits that were a problem with conventional technology. This makes it possible to almost completely avoid the phenomenon in which a part of the generated current flows to the deteriorated cell due to the high contact resistance of the cell, and the potential of the deteriorated cell is reversed due to the voltage drop of the short circuit being applied. Therefore, the risk of electrolysis of battery constituent materials and direct reaction between fuel gas and oxidizer due to reversal phenomenon is eliminated, and the deterioration of cell characteristics due to these is also prevented. Therefore, it is possible to stabilize cells without removing deteriorated cells. It is possible to provide a fuel cell that can stably continue power generation operation for a long period of time. In addition, a bypass current path with excellent conductivity and mechanical properties can be formed simply by changing the connection of the conductive plates that have been laminated in a predetermined manner, which provides the advantage of saving labor in repairs and shortening downtime.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing an embodiment of the present invention applied to a fuel cell that does not include a deteriorated cell, FIG. 2 is an enlarged view showing the main parts of FIG. 1, and FIG. FIG. 4 is a schematic side view showing a state in which an embodiment of the present invention is applied to a fuel cell including a deteriorated cell, and FIG. 4 is a schematic side view showing a conventional structure. 1: Cell, IA: Deteriorated cell, 2: Matrix, 3
．． 4: Electrode, 5: Separate plate, 6, 6A, 6B:
Cooling plate, 10, 20: Cell stack, 11. IIA
: Semi block, 15: Short circuit, 21: Current path,
22.22A. 22B: Electrical insulation sheet, 23A, 23B: Conductive plate, 25: Conductive connection part, 31: Bypass current path, 32:
Connection 4 Group 1 Figure 2 Figure 3

Claims (1)

[Claims] 1) It has a semi-block, a cooling plate, a pair of conductive plates, and an electrically insulating sheet, where the semi-block is made by stacking a plurality of cells, and the cooling plate is an electrically insulating sheet. The pair of conductive plates are sandwiched between a pair of conductive plates via a semi-block, and the pair of conductive plates are laminated alternately with semi-blocks to transmit the current of the semi-block to the other semi-blocks. The conductive plates are directly connected to each other through conductive connecting parts, or one of the conductive plates is indirectly connected to the other conductive plate, which is one half of the other pair, using a connecting conductor. A fuel cell characterized by: