JPH0129028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a matrix fuel cell using phosphoric acid as an electrolyte, and particularly to improvements in the electrolyte supply structure thereof.

In this type of fuel cell, a single cell is constructed by sandwiching a matrix impregnated with an electrolyte between two electrodes, a fuel electrode and an air electrode. On the other hand, the intake of reactant gases such as fuel and air into the layers of each electrode is carried out by a gas diffusion method, and as a method of supplying reactant gases to single cells, bipolar plates are installed at both the upper and lower ends of the above-mentioned single cells. A method in which fuel gas or air is sent to each electrode through gas passage grooves partitioned by bipolar plates stacked one on top of the other, and a porous electrode substrate in which an electrode substrate is used instead of a bipolar plate to partition a reaction gas passage. There is a method in which the reaction gas is sent to the electrode through the gas passage of the electrode substrate. In either method, in order to form a stable three-phase interface within the electrode layer and conduct the electrode reaction efficiently,
Unnecessary penetration of the liquid electrolyte into the gas diffusion electrode must be avoided.

On the other hand, it is necessary to supply the electrolyte to the matrix at least after forming the single cells, and it is also desirable to be able to supply the electrolyte with the cell stack assembled in consideration of replenishment during operation. In this case, for the reasons mentioned above, it is not suitable to supply the electrolyte to the matrix through the electrode layer, so that it is necessary to be able to supply the electrolyte directly to the matrix. Incidentally, in order to provide heat resistance and corrosion resistance, the matrix layer is generally made in the form of a thin film made of fine particles of silicon carbide bonded with polytetrafluoroethylene. However, since the polytetrafluoroethylene used as the binder here has water repellency, it is difficult for the liquid electrolyte to penetrate into the matrix layer.
For these reasons, in conventional cells, it is extremely difficult to provide an electrolyte replenishment mechanism directly in the cell body due to its structural and functional limitations, and it is also extremely difficult to provide an electrolyte supply mechanism directly into the cell body from one end to the matrix under large liquid pressure. Even if it is supplied without adding it, there are drawbacks such as difficulty in uniformly impregnating the entire area of the matrix.

This invention was made in consideration of the above points, and its purpose is to provide a matrix-type fuel that allows electrolyte to be easily replenished into the matrix from the outside, and that allows the electrolyte to be uniformly impregnated throughout the matrix layer. The goal is to provide batteries.

The present invention will be described in detail below based on illustrated embodiments.

The embodiments shown in FIGS. 1 to 4 are examples of fuel cells of a type in which unit cells are stacked via bipolar plates to form a cell stack. In each figure, 1 is a single cell, and 2 is a bipolar plate laminated above and below the single cell. Among these, the unit cell 1 is a laminate of two upper and lower fuel electrodes 3 and an air electrode 4, and a matrix 5 sandwiched between the electrodes 3 and 4, and this laminate assembly has a water-repellent outer periphery. It is covered with a sealing material 6. By the way, with this invention,
As clearly shown in FIG. 2, the matrix 5 is divided into two divided matrix layers 5A and 5B which are bonded to the surfaces of the electrodes 3 and 4, respectively, and between the divided matrix layers 5A and 5B. An intermediate layer 7 serving as an electrolyte supply passage is formed in the middle layer 7 . This intermediate layer 7 is formed by interposing, for example, carbon vapor made of carbon-based fibers having excellent hydrophilic properties or silicon carbide fibers between the divided matrix layers 5A and 5B. Ru. In this intermediate layer 7, the electrolyte flows much more easily than when the electrolyte permeates through the matrix layer 5 in the planar direction. Further, on the upper surface side of the unit cell 1, a large number of electrolyte replenishment holes 8 are provided along the side edges of the unit cell 1, penetrating the electrode 3 and the divided matrix layer 5A and reaching the intermediate layer 7 at both left and right end areas.

On the other hand, as shown in FIGS. 3 and 4, the bipolar plate 2 is made of a gas-impermeable conductive material and has air passages 9 and fuel gas passage grooves 10 orthogonal to each other formed on its upper and lower surfaces. It is something.
According to the present invention, an electrolyte storage tank 11 is provided on the lower surface side of both left and right end regions of the bipolar plate 2 as a concave groove whose lower surface is open and closed at both ends, facing the row of electrolyte replenishment holes 8 of the cell 1 described above. It is defined parallel to the fuel gas passage groove 10. Further, an electrolyte replenishment port 12 is provided in series with the tank 11 and opens on the outer surface of the bipolar plate 2.

In the above arrangement, the electrolyte storage tank 11 communicates with the intermediate layer 7 in the cell via the electrode 3 and the hole 8 passing through the split matrix layer 5A. Therefore, there are two electrolyte supply ports 12.
When electrolyte is injected from the outside through either one of the two, the electrolyte flows into the intermediate layer 7 through the storage tank 11 and the supply hole 8, and from there permeates into the divided matrix layers 5A and 5B. In addition, as this electrolyte flows in, the other supply port 12
The gas remaining in the matrix layer 5 and intermediate layer 7 escapes. In this way, even after the cell stack is assembled, it is possible to connect the pipe to the replenishment port 12 and inject electrolyte from the outside, thereby allowing smooth replenishment and impregnation into the matrix 5.

Moreover, since an intermediate layer 7 with low flow path resistance and no water repellency is formed between the divided matrix layers 5A and 5B, the electrolyte flows without resistance from this intermediate layer 7 to the upper and lower divided matrix layers 5A, The entire area of 5B will be uniformly impregnated. Furthermore, the storage tank 11 serves as a reservoir during operation of the battery, and even if the volume of the electrolyte impregnated and held in the matrix 5 increases or decreases as the operating conditions change, the tank 11 ensures that there is no excess or deficiency. can be absorbed. In addition, middle layer 7
By providing this, it is possible to penetrate the entire surface area even from the edges of the matrix, and the gas diffusion area of the electrode can be utilized more widely, which can also contribute to improving the performance of the battery.

It should be noted that, in place of the bipolar plate in the illustrated embodiment, a type of fuel cell using a porous electrode substrate can be used in the same manner. In this case an electrolyte storage tank is defined within the electrode substrate.

As described above, the present invention divides the matrix layer of a single cell into two layers, forms an intermediate layer between them that serves as an electrolyte passage, and a bipolar plate or porous electrode that is laminated in combination with this single cell. An electrolyte storage tank is defined inside the substrate, and the tank and the intermediate layer are communicated through the electrodes, so that electrolyte replenishment to the matrix can be carried out externally. This can be done smoothly and evenly over the entire matrix, and the practical benefits are extremely large.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway plan view showing the structure of a unit cell according to an embodiment of the present invention, Fig. 2 is a sectional view taken in the direction of the arrow in Fig. 1, and Fig. 3 is an embodiment in which a unit cell is combined with a bipolar plate. A partially cutaway plan view of an example,
FIG. 4 is a cross-sectional view taken in the direction of the arrows in FIG. 3. 1...Single cell, 2...Bipolar plate, 3,4
...electrode, 5...matrix, 5A, 5B...divided matrix layer, 7...intermediate layer, 8...hole, 11...electrolyte storage tank, 12...electrolyte supply port.

Claims (1)

[Scope of Claims] 1. In a matrix type fuel cell in which a single cell is constructed by sandwiching a matrix impregnated with and holding an electrolyte between two upper and lower electrodes, the matrix is divided into two layers, and a layer is formed between the divided layers. An intermediate layer serving as an electrolyte supply passage is provided in the electrode, and an electrolyte storage tank is defined inside a bipolar plate or a porous electrode substrate having a reactive gas supply passage laminated on the upper electrode side of the upper and lower electrodes. , and a matrix fuel cell characterized in that the tank and the intermediate layer are communicated vertically through electrodes. 2. The fuel cell according to claim 1, characterized in that the bipolar plate or porous electrode substrate is provided with an electrolyte replenishment port opening on the outer surface leading to an electrolyte storage tank defined inside the bipolar plate or porous electrode substrate. A matrix type fuel cell.