JPS58161267A - Matrix type fuel cell - Google Patents

Abstract

PURPOSE:To supply an electrolyte in a matrix by forming concave grooves along the substrate surface, apart from reacting gas passing grooves, on the surface faced with an electrode in an electrode substrate and inserting electrolyte supply tubes into these grooves. CONSTITUTION:A fuel electrode 2 is formed in a substrate 1 having fuel passing grooves 11, and an air electrode 4 is formed in a substrate 5 having air passing grooves 51, and a matrix 3 is placed between them to form a unit cell. A plurality of concave grooves 7 are formed along the substrate surface on the surface faced with the fuel electrode 2 in the fuel electrode side substrate 1, therein electrolyte supply tubes 8 having a large number of electrolyte supply holes 81 which open in inner direction of a cell from outside are inserted. After assembling a cell, liquid electrolyte is supplied through tubes 8 into the matrix 4, and penetration of the electrolyte to a gas diffusion layer is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention employs a porous electrode substrate, and through the substrate
For example, a matrix of phosphoric acid electrolyte type that diffuses and supplies a reactive gas to the electrodes 1. Regarding improvements in the liquid electrolyte replenishment structure of fuel cells.

As is well known, a matrix fuel cell is composed of a porous electrode substrate with fuel passage grooves on the fuel electrode side, a fuel electrode, a matrix impregnated with electrolyte, an air electrode, and a porous electrode with air passage grooves on the air electrode side. The substrates are stacked in the above order to form a unit cell, and reactant gases such as fuel and air are diffused and supplied from the outer surface of the substrate to the electrode through the porous electrode substrate. The battery is
fuel.

A N gas chemical reaction occurs at the three-phase interface between the reactive gas of air, the liquid electrolyte, and the electrodes to generate electricity.

In this case, the stability of the three-phase interface where the gas phase and liquid phase contact the solid phase of the electrode catalyst layer greatly influences the power generation efficiency of the battery. In other words, in order to maintain a stable electrochemical reaction (
7+: It is necessary that the electrolyte is sufficiently retained in the matrix or the matrix, that it is in good contact with the electrode, and that the reaction gas is smoothly supplied to the electrode. For this head porous x
In a fuel cell using an i-substrate, it is extremely important to take care not to block the gas diffusion layer of the porous electrode substrate with liquid electrolyte, especially during operation.

- Since impregnating electrolytes into the matrix and the matrix before assembling the fuel cell will cause various problems, it is desirable to simultaneously supply the matrix and the matrix from the outside after the battery is assembled.

By the way, the conventional fuel N4 pond was constructed as shown in Fig. 1. Figure 1.5 shows a single cell battery, and it is well known that in order to form a cell star or a cell block by stacking a large number of single cells, they are stacked through a gas separation plate (not shown). It is. In the figure, 1 indicates a fuel passage groove 11 on the top surface.
2 is a fuel electrode formed by applying a TC catalyst layer on the electrode substrate 1 from carbonaceous powder supporting a platinum catalyst and a small amount of binder;
3 is heat resistant.

A porous material with high liquid electrolyte retention that provides corrosion resistance.
For example, matrix, kusu, 4 made of silicon carbide.
5 is an air electrode formed in the same manner as the fuel electrode 2, and 5 also has an air passage groove 51 on the bottom surface. This is a porous electrode substrate on the air stack side. Furthermore, a layer 6 for replenishing and storing electrolyte, called a so-called reservoir layer, is formed locally on the electrode substrate 1 on the fuel electrode side, spanning between the upper and lower surfaces of the substrate.

This reservoir layer 6 is made by, for example, masking the reservoir layer 60 portion, impregnating other regions with a water-repellent resin such as polytetrafluoroethylene, and applying water-repellent treatment to the reservoir layer 6. It is formed in such a way that it maintains its hydrophilic properties without applying any additives. With this configuration, when the liquid volume of the electrolyte increases due to moisture absorption etc. during operation of the battery, this excess volume is temporarily stored in the reservoir layer, and the liquid electrolyte is unnecessarily removed from the electrodes. It is possible to prevent the gas diffusion layer of the electrode substrate from being blocked.

However, in the conventional structure described above, the reservoir layer is not covered with a separate plate when the battery is assembled, and electrolyte cannot be replenished from the outside through the reservoir. For this purpose, the electrolyte has been replenished from the periphery of the matrix, or a separate electrolyte supply passage has been provided.

In addition, by using the substrate of a porous electrode substrate originally made for gas diffusion, a water-repellent gas diffusion layer and a non-water-repellent reservoir layer are formed in the same substrate by impregnating it with a water-repellent resin. In this case, the electrolyte retention power of the reservoir layer itself is relatively weak, and furthermore, it is difficult to control the water repellent treatment, and the water repellency of the boundary area between the reservoir layer and the gas diffusion layer within the electrode substrate layer is incomplete. It tends to become. As a result, as time passes, the water repellency of the gas diffusion layer around the reservoir layer deteriorates, and as a result, the electrolyte remaining in the reservoir layer oozes out into the surrounding gas diffusion layer. In such a state (5), gas diffusion within the electrode substrate is hindered,
Reactant gas is not supplied to each tonne as scheduled, resulting in a significant drop in power generation efficiency.

The present invention has been made in consideration of the above points, and its purpose is to eliminate the drawbacks of the conventional technology by 11il$, without impairing the gas diffusion function of the electrode substrate. An object of the present invention is to provide a matrix fuel cell in which solutes can be replenished from the outside and stored within the cell.

To achieve this purpose, according to the present invention, a concave groove is formed on the surface of the electrode substrate facing one pole along the plate surface, separated from the reaction gas passage groove, and an electrolyte replenishment tube is inserted into the groove from the outside. This is achieved by installing an interposed pipe, and injecting liquid electrolyte through this electrolyte replenishment pipe to soak the matrix and the bath.

Below, this invention will be described in detail based on illustrated embodiments.

First, in FIGS. 2 and 3, a fuel electrode 2 +C
A plurality of grooves 7 (6) along the plate surface are formed on the opposing side. This groove 7 is an electrode substrate]
(It straddles and communicates between the posterior margin of niiT.

Then, an electrolyte replenishment tube 8 is inserted into this groove 7 from the outside.
is inserted and piped. Further, this replenishment tube 8 is provided with a large number of electrolytic gt replenishment holes 81 which are dispersed and opened toward the inside of the battery at the portion inserted into the groove. In addition, fuel electrode 2
It is also notched to match the groove 7. Further, the replenishment tube 8 is sole-shaped with respect to the electrode γ plate 1 at the end of its concave groove 7. Furthermore, the electrode substrate 1 has been sufficiently treated with water throughout its entire layer.

In the above configuration, by supplying liquid electrolyte from the outside through the replenishment tube 8 after the battery is assembled, the electrolyte flows down into the groove through the replenishment hole 81, and from there penetrates into the matrix and gas 4 to impregnate it. In this case, the electrolytic solution is replenished through the replenishment tube 8, so it can be done easily and smoothly, and furthermore, the electrode substrate 1 is hardly wetted with the electrolyte.

In addition, the tube 8 itself functions as an electrolyte reservoir, and the excess amount due to the increase in electrolyte volume generated during operation can be returned to the tube through the gas and stored therein.

Next, FIGS. 4 and 5 show another embodiment. This embodiment differs from the previous embodiment in that the electrolyte replenishment tube 8 is opened at the entrance of the groove 7 formed in the electrode substrate 1 and connected thereto, and almost throughout the entire area inside the groove. is a hydrophilic porous material 9 with a large electrolyte retention capacity, such as the same material as Matori and Gesu 3, or a material that is the same as the electrode base material without water repellent treatment but whose particle size is coarser than the electrode base material. Filled. In contrast, the entire area of the electrode substrate 1 is sufficiently water-repellent.

In this embodiment, as in the previous embodiment, by supplying liquid electrolyte from the outside through the replenishment cheese 8, the electrolyte penetrates into the filler material 9 in the groove 7, and then the matrix,
The groove filling material 9 impregnated with the gas 3 can have an electrolyte holding power sufficiently larger than that of the reservoir layer in FIG. Therefore, the filling material in the concave groove serves as an electrolyte storage area, a reservoir, and a positive mechanism.1 Due to its large electrolyte holding power, even if the water repellency of the electrolyte substrate side deteriorates to some extent, the electrolyte remains on the electrode substrate side. It is possible to prevent the water-repellent treated gas from penetrating into the grooves.In addition, the filling material 9 inside the groove is not exposed at all to the outer surface of the electrode substrate as shown in Fig. 1. Therefore, there is an advantage that there is no fear of electrolyte leaking to the fuel gas passage side.

As described above, according to the present invention, it is possible to replenish and store liquid electrolyte for pinworms and gases by a simple means, while skillfully utilizing the electrode substrate and without impairing the gas diffusion function of the electrode substrate. can be achieved. Moreover, there is no need for the conventional multi-axial treatment to separate and form a water-repellent gas diffusion layer and a hydrophilic reservoir layer inside the substrate of the electrode substrate. Its practical effects are extremely impressive, such as sufficient water repellency and the ability to reliably prevent electrolyte from penetrating into the gas diffusion layer.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a single cell of a conventional matrix type fuel cell, and Fig.
Figure a is a sectional view taken along arrows III--III in Figure 2, Figure 4 is a partially cutaway plan view of a unit cell according to another embodiment of the present invention viewed from the bottom side, and Figure 5 is a sectional view taken along arrows III--III in Figure 4. Visual V-
■It is a sectional view. 1.5... Porous electrode substrate, 2.4... Electrode, 3.
...Matrix, 7. Concave groove, 8. Electrolyte replenishment tube, 81. Electrolyte replenishment hole, 9. Hydrophilic porous material for filling in the groove. (10)

Claims (1)

[Claims] ]) Porous electrode substrate with fuel passage grooves on the fuel electrode side, fuel! ! In a matrix-type fuel cell consisting of a porous electrode substrate with electrodes, a matrix, an air electrode, and nine air passage grooves on the air electrode side stacked in the above order, a reactive gas is placed on the surface of the electrode substrate facing the electrode. A concave groove is cut along the plate surface and separated from the passage groove, and an electrolyte replenishment tube is inserted from the outside into this concave groove, and liquid electrolyte is injected through the electrolyte replenishment tube. A matrix type fuel cell characterized by impregnating it into a gas. 2. In the fuel cell according to claim 1,
A matrix type characterized in that an electrolyte replenishment tube is inserted and piped over the entire length of the recessed groove, and the insertion portion of the tube into the recessed groove has electrolyte replenishment holes distributed openings 11 toward the matrix and the box. Fuel cell. 3) In the fuel cell according to claim 1,
A matrix-type fuel cell, characterized in that an electrolyte replenishment tube opens at the entrance of a groove and is connected to the groove, and the inside of the groove is filled with a hydrophilic porous material having a large electrolyte retention capacity.