JPS58166636A - Fuel cell - Google Patents

Abstract

PURPOSE:To hold phosphoric acid in a matrix throughout a long period, by hydrophilically forming plural ribs forming a gas flow path in one surface of a fuel electrode and oxygen electrode further forming both a water repellent layer mutually betwen the ribs faced to the gas path and a hydrophilic layer communicating the ribs. CONSTITUTION:Ribs 11 of both electrodes form gas passages simultaneously are used as the reservoir for storage of phosphoric acid and as the hydrophilic area. Both electrode parts faced to gas passages 3, 4 are partitioned to at least one hydrophilic layer 12a and water repellent layer 12b. While at least a communication passage 14, that is, an electrolyte supplying means is provided to an end part 13 of the both electrodes 1, 2, and an opening part 15, through which phosphoric acid can be supplied from the outside, is provided to at least one place of said passage 14. Further the peripheral side of the both electrodes 1, 2 is wholly formed to a water repellent fine state, and a water repellent finely formed layer 16, used as the layer for preventing infiltration of phosphoric acid and diffusion of gas, is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel cell, and more particularly to a fuel cell using a phosphoric acid storage type electrode of a phosphoric acid type electrolyte.

A conventional fuel cell is constructed as shown in FIG. 1, and fuel scum and air, which is an oxidant gas, flow perpendicularly to each other as shown by the arrows, and electrical energy is extracted by the well-known reaction between hydrogen and oxygen.

The air electrode 1, which has a gas passage 3 on one side, has a catalyst layer treated on the side opposite to the gas passage, and is made of a porous carbon material so that air can quickly reach the catalyst layer. has been done. The fuel electrode 2, which is opposite to the air electrode 1, is
Like the air electrode 1, it has a gas passage 4 and a catalyst layer, and is made of a porous carbon material. These two poles 1.2
A matrix 5 holding an electrolytic solution such as phosphoric acid, which is a good conductor of ions, is disposed in between so as to be impregnated therebetween.

Each -1, -2 and matrix 5 are elements constituting one battery, and this unit battery is alternately stacked with dragon pallets 6 to form a large-capacity power generation facility.

The ninth supply/discharge device 7, which supplies or discharges fuel and air, respectively, is stacked and fixed to the 2g side of the pressure cell body, and supplies fuel H8 and air oI to each unit cell collectively as shown by the arrows. Supplying and discharging is carried out.

In addition, a cooling device 8 is inserted into the stack 41 of several unit cells in the battery body, and cools the battery while keeping the temperature of the battery constant using cooling water or the like.

The fuel cell constructed in this way extracts dynamic electrical energy through the reaction of hydrogen and oxygen, but in reality, the volume of water and oxygen in the air passing through each gas passage is The material diffuses within the electrode substrate and spreads over the catalyst layer. Generally, in the reaction in the catalyst layer, the fuel@2 is separated into hydrogen ions and electrons, and the hydrogen ions are diffused into the electrolyte.1 The degree of this reaction is relatively large. On the other hand, at the air electrode No. 1, oxygen molecules take in electrons, are ionized, and combine with hydrogen ions in the electrolyte to produce water.

This reaction is generally slow compared to the hydrogen side.

This exchange of electrons in the matrix 5 can be extracted as electrical energy, but the efficiency of conversion into electrical energy depends not only on the degree of activation of the catalyst, but also on the behavior of the phosphoric acid in the matrix 5. Become. In other words, current fuel cells use a method to confine phosphoric acid in a fixed amount.If there is insufficient phosphoric acid in the matrix 5, it will inhibit the movement of hydrogen ions and reduce the contact area with the catalyst layer. This also causes an increase in the internal resistance of the battery.

9. Due to the lack of phosphoric acid, pores are generated in the matrix 5.1. This leads to mixing of hydrogen and air, causing direct combustion and reducing performance.

Such a shortage of phosphoric acid is caused by the evaporation of phosphoric acid and the force of leaching into the electrode base material due to thermal expansion and volume change due to the mechanical tightening ring. Several proposals have been made to prevent the loss of phosphoric acid in the matrix layer by applying phosphoric acid to the electrode base material beforehand. As a representative example of this, Japanese Patent Application Laid-open No. 53-32352 and 32353
There is a method disclosed in K. In this method, the catalyst layer side of the thin electrode base material is a water sprinkling layer, and the opposite side is a parent wood layer, and the water sprinkling layer has one area such as a matrix material. 19. The hydrophilic layer is provided with an opening for supplying gas to the water-repellent layer.
The configuration is as follows. However, this method is technically difficult and tends to cause poor gas diffusion, and the biggest drawback is that it is difficult to supply phosphoric acid to the redundant layer, and the lifespan is almost determined by the amount reserved at the beginning. It is.

An object of the present invention is to provide a fuel cell in which an electrolytic solution is reserved throughout the cell, which is easy to manufacture and has good workability, and which can retain phosphoric acid in the matrix for a long period of time.

The fuel cell of this invention has a plurality of hydrophilic ribs forming gas flow paths on one side of the fuel electrode and the oxygen electrode, and a water-repellent layer is formed between the ribs facing the gas path. In addition, at least one hydrophilic layer is formed to connect the ribs in the length direction of the gas passage, thereby preventing the loss of phosphoric acid in the matrix.

Below is an example of the present invention! This will be explained with reference to FIGS. 2 to 5.

Air electrodes 1. each having a gas passage 3.4. As is well known, the fuel electrode 2 is made of a porous carbon material, and both the electrodes 1 and 2 have catalyst holes 19.4 on the opposite sides of the gas passages 3.4.
10 has been processed and bonded to the substrate.

Matrix 5u, st that holds phosphoric acid as an electrolyte
Powder such as c is converted into polytetrafluoroethylene (hereinafter referred to as PTF).
(referred to as E), etc., and phosphoric acid is held in the gap between these.

The ribs 11 on both poles form a gas path and also serve as a current path when batteries are stacked.Furthermore, the ribs 11 are round reservoirs for storing phosphoric acid, and are made into hydrophilic areas. be.

Both pole portions facing the gas passage 3.4 are divided into at least one hydrophilic layer 121 and a water repellent layer 12b. The water-repellent layer 12b is patterned so that the phosphoric acid of the ribs 11 does not penetrate so that the reaction gas can diffuse into the catalyst layer 9.10. On the other hand, the hydrophilic layer 12m is a layer into which phosphoric acid easily permeates.

Therefore, as shown in Fig. 3, the rib 1 which becomes the reserve layer
1 is not independent, but communicates through the hydrophilic layer 12m, allowing the movement of phosphoric acid as shown by the arrow. Furthermore, the shoulder portion 13 of both electrodes 1.2 has at least one communication passage 14 serving as an electrolyte supply means, and this communication passage 14 has at least one opening 15 through which phosphoric acid can be supplied from the outside. It is equipped. Furthermore, the entire outer periphery of both poles 1.2 is densified and water-repellent layer 16 serves as a layer to prevent penetration of water and phosphoric acid and diffusion of gas.
is formed.

A specific method for forming the water repellent layer 111112b, the hydrophilic layer 12m, and the water repellent densified layer 16 will be described below.

The water-repellent layer 12b can be easily obtained by applying a dispersion liquid in which fine powder of PTFE is dispersed in water using a surfactant, and heating and melting the dispersion liquid. Note that when applying, it is convenient to heat the electrode to a temperature higher than the boiling point of water in advance to prevent the dispersion liquid from spreading to the lip side.

Next, for the hydrophilic layer 12a, the carbon substrate of the electrode may be used as is, but it is better to include some 〇H groups.A liquid prepared by dispersing phenolic resin in water is applied to this rounded layer, and P
It can be easily obtained by carbonizing at a temperature below a temperature at which TFE does not decompose. At this time, it is also advantageous to heat the electrode to a temperature higher than the boiling point of water, as this makes it difficult for the liquid to penetrate into the water-repellent layer beyond the water-spraying effect.

Further, the water-repellent densified layer 16 is made of, for example, SiC powder and the P
It can be easily obtained by impregnating the electrode end with a high viscosity liquid mixed with a TFE dispersion liquid and heating and melting the PTFE.

The ninth opening 12 for supplying phosphoric acid is shown in FIGS.
As shown in the figure, it can be easily obtained by inserting a tube of metal with good phosphoric acid resistance, such as platinum or tantalum, or PTFE, into the electrode. Providing a protrusion or enlarging the electrode-side tip of the tube is effective in preventing the tube from coming off.

With this configuration, when phosphoric acid is injected from the opening 15, the phosphoric acid flows through the communication path 14. It passes through the IN water layer 121 and reaches the rib 11, which serves as a reserve layer, where phosphoric acid can be stored.

Furthermore, by providing the opening 15 inside or outside the battery and connecting it to a non-phosphoric acid storage tank, it is possible to replenish the reserve layer with tetra-phosphoric acid while the battery is in operation.

In this embodiment, the rib 11 serving as a reserve layer for acid/acid is communicated with the communicating path 14 through a hydrophilic layer 12m, and the communicating path 14
By providing an opening outside one electrode, phosphoric acid can be supplied from the outside, which improves workability during battery assembly, and phosphoric acid can be replenished as needed, allowing stable operation of the battery. There is an effect that can be done.

Next, in the embodiment shown in FIG.
This is derived from the corner of 9, which is different from those shown in Figures 2 to 5. Phosphoric acid can be replenished from outside the gas supply and exhaust system, making it easy to construct and easy to maintain. This has the effect of making it easier.

In each of the above-mentioned embodiments, phosphoric acid is supplied to the various ribs 11 and the hydrophilic layer 12m from the communication passage 514, which is an electrolyte supply means, but the communication passage 14 is omitted and phosphoric acid is supplied to each rib 11. Even just by reserving acid, the battery life can be further extended compared to conventional methods.

Further, in the example of FIG. 7 which is another embodiment of the present invention, the poles 1.2 have ribs 13 on one side for forming gas passages 3.4 and the other side as in FIG. It is made of a porous carbon material with catalyst layers 9 and 10 provided thereon, and the ribs 11 are hydrophilic layers.
In addition, water repellent holes 7#12b between the ribs 11 and hydrophilic holes for communicating between the ribs 11 are formed. And catalyst layer 9
, 10 facing the rib 11 is formed with a hydrophilic communication hole 1117, which connects the rib 11 and the matrix 5.
, and its hydrophilicity allows for the transfer of phosphoric acid. As shown in FIG.
As shown in Figure 19, it is advantageous to have a wide diffusion area. l1m indicates the surface of the rib 13. This communication layer 17
The specific construction method is to apply phenol resin to the part facing the ribs 11 of the catalyst layer 9 treated on the flat surface of the electrode using a method such as a screen seal, and then to the part that will become the communication layer 17. Since it is filled with resin, it can be easily obtained by heating and curing this resin and carbonizing it at a high temperature.

In this translation process, the catalyst layer generally contains fluorine-based polymers, such as PTFE, in order to have water repellency, so that these do not decompose41! ! In the case of PTFE, the temperature is preferably about 350C or less.

With this configuration, the expansion and contraction of phosphoric acid in the matrix 5 can go in and out of the reserve layer of the ribs 11 through the communication layer 17 of the catalyst layer 9. Also, the decrease in phosphoric acid due to evaporation is compensated for by replenishment from the reserve. Moreover, since the matrix 5 can be constructed flat, there is no generation of bubbles and the workability is improved.

According to the present invention, a reserve layer of electrolyte can be easily formed on both electrodes, making it easy to assemble the battery, and since the phosphoric acid in the reserve layer can be controlled at a constant level, the battery can be operated stably for a long period of time. effective.

[Brief explanation of the drawing]

Fig. 1 is an exploded cross-sectional view showing the product structure of a conventional fuel cell, Fig. 2 is a partial cross-sectional view of an electrode of a fuel cell according to an embodiment of the present invention, and Fig. 3 is an A of Fig. 2. -A' perspective view Figure 4 is a partial plan view of Figure 3; Figure 5 is a BB' perspective view of Figure 4; Figure 6 is a partial sectional view showing the structure of the battery corner; The figure is a partial sectional view of an electrode of a fuel cell according to another embodiment of the present invention.
Fig. 8 is a view from c-c' in Fig. 7. Fig. 9 is a view taken from D--C in Fig. 7.
There is a D' view. 1... Air electrode, 2... Fuel electrode, 3, 4... Gas passage, 5... Matrix, 9.・10...catalyst layer,
11...Rip, 12J1...Himesui layer, 12b...
Water repellent layer, 14... Communication path, 15... Opening, 16.
... Water-repellent densified layer, 17... Connection Figure 2 15 Figure 6

Claims (1)

[Claims] 1. A fuel electrode and an air electrode each having a plurality of lips forming gas passages on one surface and having a catalyst layer on the other surface are arranged so that the catalyst layers face each other, Retain electrolyte between layers! In the TRIX arrangement 40, the two poles each have a hydrophilic lip and a gas passageway Kli.
! 9. A fuel cell characterized in that a water-repellent layer is formed between the lips, and at least one or more hydrophilic layer is formed that connects the lips in the length direction of the gas passage. 2. In claim 1, the end of the electrode has an outside 1! 9. A fuel cell comprising at least one electrolyte supply means having an opening at the bottom of the fuel cell. & In claim 1, the catalyst layer includes:
% that a hydrophilic communication layer was formed at the position corresponding to the lip.
Fuel cells that turn into mold. 4. The fuel cell according to claim 2, wherein the hydrophilic layer including the electrolyte supply means is surrounded by a water-repellent densified layer. & %ffm The fuel cell according to item 2, wherein the opening of the electrolyte supply means is provided at a corner of the electrode.