JPS6310469A - Stacked fuel cell - Google Patents

Abstract

PURPOSE:To minimize a gas diffusion obstruction and to obtain the sufficient amount of electrolyte reserve and gas diffusion capability by installing a 0.3-0.5mm thick oxidizing agent electrode substrate to which water repellent treatment is applied and a 0.8-3.2mm thick fuel electrode substrate to which no water repellent treatment is applied, and an external reservoir having porous base material. CONSTITUTION:A 0.3-0.5mm thick oxidizing agent electrode substrate 5 to which water repellent treatment is applied, and a 0.8-3.2mm thick fuel electrode substrate 2 to which no water repellent treatment is applied, and an external reservoir 26 which is mounted to a gas separating plate 10 and is in contact with the fuel electrode substrate 2 and has porous base material are installed. The gas diffusion obstruction within the substrates is minimized, and the sufficient amount of electrolyte reserve and gas diffusion capability are obtained. Since the region where gas sealing is required is slightly larger than a rib- installed separator type but far small compared with a rib-installed electrode type or hybrid type, gas sealing is easy. The reserving function of the fuel electrode substrate 2 is increased and supplement of electrolyte from the outside is made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Industrial Field of Application The present invention relates to stacked fuel cells, and particularly to the construction of cell barrels.

[Conventional technology]

As is well known, a fuel cell is operated by interposing an electrolyte matrix holding an electrolyte between a fuel electrode and an oxidizer electrode arranged opposite each other, and supplying fuel and oxidizer to the fuel electrode and the oxidizer electrode, respectively. It is a type of power generation device.

Fuel cells are: ■ High efficiency can be expected as there is no Carnot cycle restriction; ■ Waste heat can be obtained at a relatively high temperature close to the cell operating temperature and can be easily used effectively; ■ Efficiency does not change much even if the output is changed. , ■It has the advantage of being highly responsive to negative power fluctuations, and can be used in various ways, such as being distributed within or near cities on the scale of distribution substations, or as an alternative power generation device for thermal power plants. It is considered.

Fuel cells are classified into alkaline type, phosphoric acid type, molten carbonate type, etc. depending on the type of electrolyte used. Of these, the phosphoric acid type is called the first generation and is the most developed.
Trial runs on a practical scale have already been carried out.

Here, for example, a phosphoric acid fuel cell will be explained. The most auridox cell configuration among phosphoric acid fuel cells is a type called a lip separator type, which is disclosed in U.S. Patent No. 3,867.
．． 206 specification (Japanese Patent Publication No. 58-152) and US Patent No. 4,276.355 (Japanese Patent Publication No. 59-6
A typical battery configuration is described in Japanese Patent No. 6067). FIG. 8 is a cross-sectional view showing a typical configuration of a separator type with lips. In the figure, +11 is an electrolyte holding matrix, (4) is a fuel electrode, (2) is an electrode base of the fuel electrode, ) is the catalyst layer of the fuel electrode, (7) is the oxidizer electrode,
(5) is the electrode base of the oxidizer electrode, (6) is the catalyst layer of the oxidizer electrode, (8) is the wet gas seal part of the fuel electrode, (9)
is the wet gas seal part of the oxidizer electrode, αΦ is the gas separation plate (
Qll is also called a separator, bipolar plate, interconnector, etc.
is a fuel gas flow path (orthogonal to the oxidant gas flow path), and (24) is an external reservoir. Gas separation plate 01l
It is called a lip separator type because the reaction gas flow paths αυ and 4 are formed in 11 and 11. The wet gas seal parts (8) and (9) may be replaced with gas seals using banking material. 1. indicates the thickness of one cell structure, and generally in the case of a lip separator type, the gas separation plate α1 is approximately 3 mm thick and the base materials (2) and (5) are 0.
．． Since the total thickness of the catalyst layers (3) and (6) and the electrolyte holding matrix layer +11 is about 0.6 mm, the thickness of t is about 4.4 mff1.

While the gas separation plate 001 is unfavorable, the base material (
2) and (5) are porous, so 1. A sufficient gas seal is required within this range. In the case of the separator type with a lip, t is approximately 1.41 mm thick, and the thicker the thickness, the more difficult it is to seal the gas. In addition, while the gas separation plate αl is made of dense carbon and has good thermal conductivity, the base materials (2) and (5) are porous and contain more than 50% gas (air or fuel). In addition, the electrolyte retention matrix layer (11) also has poor thermal conductivity.Therefore, t2 is also a region with poor thermal conductivity.In stacked fuel cells, cooling plates are usually inserted every 5 cells. It absorbs the generated heat and cools the cell to maintain a uniform operating temperature.Therefore, the thicker the t! This causes problems such as corrosion of components due to high temperatures and deterioration of cell characteristics due to low temperatures.

The first advantage of the separator type with lip is that gas sealing is easier because the thickness of t2 is thinner than other types described later, and the second advantage is that it has good heat conduction for the same reason. be.

In the case of the lipped separator type, the base materials (2) and (5) are all subjected to water repellent treatment. This is done to prevent the electrolyte in the electrolyte matrix from flowing out through the catalyst layer to the substrate, blocking the pores of the substrate and inhibiting the permeability of the reactant gas. Regarding methods of water-repellent treatment of base materials, see JP-A-60-220565 and JP-A-604.
It is described in detail in the 33663 publication.

Furthermore, even in the case of the same base material, the edges are often filled with a hydrophilic material such as silicon carbide to retain the electrolyte and serve as a wet gas sealing part. Therefore, in the case of the ribbed separator type, the part occupied by the electrolyte consists of the electrolyte holding matrix (1), the catalyst layer (3), (6) and the wet gas seal part (8).
(9) However, during long-term operation, the electrolyte becomes insufficient due to scattering, evaporation, etc. Therefore, an external reservoir (24) is provided in a part of the gas separation plate Ql, and the wet gas It is brought into contact with the seal parts (8), (9) and the matrix (11), making it possible to replenish electrolyte from the outside to the matrix (1).For external reservoirs, see Japanese Patent Laid-Open No. 58-1
It is described in detail in No. 61269 and Japanese Unexamined Patent Publication No. 59-211969. To form an external reservoir 2~
The gas separation plate α0 is most suitable as a part for forming an external reservoir, and the ribbed separator type is easy to form the external reservoir (24). This is the third advantage.

On the other hand, the disadvantage of the ribbed separator type is that its ability to absorb expansion of the electrolytic solution is insufficient. Since fuel cells generate water during operation, this generated water dilutes the electrolyte and increases the volume of the electrolyte beyond what is contained in the matrix, thereby increasing the operating pressure, operating temperature, current density, and reactant gas utilization rate. The volume of the electrolyte varies greatly depending on the operating conditions. This increased volume moves within the matrix and box and is stored in the wet seal parts (8), (9) and the external reservoir (24), but the size of the cells increases and the distance traveled within the matrix becomes longer. When this happens, the movement of the electrolyte within the matrix becomes slower than the rate of expansion of the volume, and the increased volume enters the catalyst layers (3) and (6), causing flooding, and further tB water treatment. Inside the base material (2), (
5) and could not return to the matrix (which caused an extremely serious situation, such as the next time the volume contracted, the electrolyte in the matrix became insufficient and a crossover occurred).

In order to prevent the electrolyte from flowing out from the matrix to the base material through the catalyst layer, a layer with enhanced TA aqueous properties is provided between the catalyst layer and the base material, as disclosed in JP-A-50-101837 and JP-A-60-60. No. 170168, JP 60-241655
However, the effect is not sufficient, and as the area of the cell increases, in the ribbed separator type, the lack of absorption function against the expansion of the electrolyte becomes fatal. It was defective. As a solution to this defect, attempts have been made for a long time to provide a storage function (reservation function) for the expansion of the electrolytic solution inside or behind the electrode base material. First, Japanese Patent Application Publication No. 47-31137
The publication describes a matrix configuration in which a porous plate is placed behind the fuel electrode and an electrolyte chamber is placed further behind it, and the electrolyte is circulated using "pins" to control the amount of electrolyte in the matrix. It has been described. Also, JP-A-5
0-101836 describes a configuration in which a matrix material is provided through the catalyst layer of the fuel species and the electrode base material to the back surface of the base material to provide a reserve function, Publication No. 32352 (U.S. Characteristics No. 4, 064,
．． 322) and Japanese Unexamined Patent Publication No. 53-32353 (US Pat. No. 4,038,463) describe a structure in which a hydrophilic area and a hydrophobic area are formed inside the base material to provide a reserve function. . However, all of these configurations are extremely complex and require numerous steps to realize these configurations, resulting in high costs.Moreover, these configurations include many elements that inhibit the diffusivity of the reactant gas in the base material. However, the reserve function was not necessarily sufficient.

On the other hand, Japanese Patent Application Publication No. 53-30747 (U.S. Patent No. 4,035
, No. 55mm) The configuration described in the publication is very simple and simply does not provide water repellent treatment to the base material.
According to the example in the above specification, the base material has a thickness of Q, 3 mm = 0
．． 5Ml11 Porosity 75~88χ Average pore size 14~8
3 μm carbon paper is used, and the small pores in this base material have a reserve function for the electrolyte, while the larger pores act as passages for the reactant gas. It states that it must not have holes. Due to this +R configuration, it is possible to add a reserve function to the ribbed separator type without having to treat the base material on the fuel side by 14X, which has the effect of inhibiting gas diffusivity. Yes, but the actual bfF in the above specification.

The reserve function was insufficient within the scope of the example.

In addition, the second disadvantage of the ribbed separator type is that the reaction gas must flow horizontally through the base material to the molten layer directly below the convex portion (rib) of the reaction gas flow path formed on the gas separation plate. Although there is a view that the gas diffusivity is insufficient, the generally used groove width 11 to 1.5 mm is described in Japanese Patent Application Laid-open No. 73852/1983.
, this problem hardly occurs when the thickness of the base material is 0.3a+m -0.4mm. However, JP-A-59-40
Base material thickness 0.4 as described in Publication No. 471
Compared to m+w, this disadvantage is serious in those in which the catalyst layer is penetrated into the inside.

Also, regarding the base material on the fuel 1 side described earlier, which has a reserve function added without T8 water treatment, there is a problem with gas diffusivity when the electrolyte is reserved because the base material is thin. was there.

Next to the ribbed separator type, the most typical battery configuration is the ribbed electrode type. For this type, US Patent 4,11
No. 5,627, No. 4.165.349 and JP-A-58
It is described in detail in JP-A-68881. FIG. 9 is a sectional view showing a typical structure of the ribbed electrode type.

In the ribbed electrode type, the thickness of the base materials (2) and (5) is increased, and the reaction gas flow path Oυ and grooves are formed therein. Therefore, Gas Separate Tei OI is a flat, thin and unfavorable Mutan.

The single greatest advantage of the ribbed electrode type is its ability to absorb expansion of the electrolyte. Japanese Unexamined Patent Publication 1986-1968
According to Publication No. 881, the average bore diameter of the flat seat portion of the ribbed base material is 25 to 45 μm, and the average bore diameter of the rib portion of the ribbed base material is 60 to 75% of the seat portion, that is, 15 to 3 μm.
By setting the thickness to 4 μm, the electrolyte overflowing with Matri-Nox can be selectively stored in the rib portion, which has a large capillary suction force next to Matri-Nox. Furthermore, when the matrix runs out of electrolyte, the electrolyte stored in the rib portion is supplied to the matrix via the sheet portion and the catalyst layer.

The thickness of the ribbed base material is generally about 1.8 mm, the gas separation plate is about 0.8 mm, and the total of the catalyst layer and electrolyte holding matrix layer is about 0.6 m1I, so 1. The thickness is approximately 5.01 mm, which is slightly thicker than the ribbed separator type. This is because the web of the ribbed base material cannot be made thin because the mechanical strength of the ribbed base material is weak. In addition, since the ribbed base material is porous, the area t where gas sealing is required
2 is 4.2mm, which is much larger than the ribbed separator type.
It is three times as thick as it is, so gas sealing is difficult. This is the first disadvantage of the ribbed electrode type. Furthermore, the area with poor heat conduction is also three times thicker than that of the ribbed separator type, which requires a cooler with higher performance, resulting in higher costs.This is the second disadvantage of the knobbed electrode type.

In addition, the ribbed base is porous and has low mechanical strength, and since it has grooves, it tends to break in a direction square to the grooves and is difficult to handle.This is the third disadvantage of the ribbed electrode type.

Furthermore, in the ribbed electrode type, the thickness of the gas impermeable gas separation plate is as thin as 0.81 mm, making it impossible to provide an external reservoir. Further, it is difficult to provide an external reservoir on a porous ribbed base material, and even if it could be provided, the cost would be high. Therefore, external replenishment of electrolyte is difficult. As a method of replenishing electrolyte for the ribbed electrode type, Japanese Patent Application Laid-open No. 61
As described in Japanese Patent No. 47073 and Japanese Patent Application Laid-open No. 61-47074, a method is used in which the electrolytic solution is allowed to flow from the top to the bottom of the stacked fuel cell and the ribbed base material absorbs the electrolytic solution. However, with this method, it is difficult to grasp the amount of electrolyte to be replenished for each cell, and when operating after replenishment, leaf current flows because the edges of the stack from top to bottom are wet due to electrolysis overnight. There is also a risk of damaging the battery.

Therefore, the fourth disadvantage is that it is difficult to provide an external reservoir.

Furthermore, in the ribbed amount ti type, the diffusivity of the oxidant gas within the oxidizer electrode base is limited. Because the web thickness of the ribbed base material cannot be made as thin as the thickness of the ribbed separator type base material (0.3 to 0.4 mm) from the viewpoint of mechanical strength, we first decided to use the oxidizer electrode base material. When water repellent treatment is applied, the porosity of the base material decreases due to the water repellent, and a film of the water reagent forms between the base fibers, inhibiting the diffusion of oxidant gas to some extent. However, in the case of the ribbed electrode type, the greater the thickness of the web, the greater the degree of diffusivity inhibition than in the ribbed parquet type, and the output voltage of the cell decreases accordingly. Next, if the oxidizer electrode base material is not subjected to T8 water treatment, even if the initial electrolyte is not reserved in the oxidizer electrode base material, the electrolyte in an amount of about 5χ of the pore volume of the electrode base material will be transferred from the matrix to the oxidizer electrode. The oxidizer moves to the electrode base material through the inside of the base material, and the diffusivity of the oxidant gas is inhibited, similar to the In water solution.
The output voltage of the cell decreases accordingly. The reason why the allowable reserve value in the oxidizer electrode base material is smaller than that in the case where the electrolyte and the electrolyte are reserved in the fuel cell Ff1 base material is disclosed in Japanese Patent Application Laid-Open No. 53-307.
This is thought to be due to the difference in diffusivity between hydrogen, which is contained in a large amount in the fuel gas, and oxygen, which is contained in the oxidizing gas, as described in Japanese Patent No. 47. Therefore, the fifth disadvantage of the ribbed electrode type is that the output voltage decreases due to insufficient diffusion of the oxidant gas within the oxidant electrode base material. For this reason, as described in JP-A No. 58-68881, the pore diameter of the web is made as large as possible to prevent the electrolyte from being retained, and JP-A No. 59-2746
As described in Publication No. 6, it was necessary to change the material for the ribbed base material, such as using carbon fiber longer than the ribs for the web, resulting in increased costs.

In addition to the ribbed separator type and the ribbed scraper type, a historical type of these two types is called a hybrid type and is disclosed in Japanese Patent Application Laid-Open No. 58-94768. FIG. 10 is a sectional view showing the configuration of this hybrid type. In the hybrid type, a ribbed separator type structure is used on the oxidizer electrode side, and a ribbed electrode type structure is used on the fuel electrode side. In the hybrid type, the fuel electrode side has a function of absorbing the expansion of the electrolyte, and the oxidizer electrode side has a thin base material, which eliminates the fifth disadvantage of the ribbed electrode type, which is the oxidizer electrode base material. Improves gas diffusivity. Although the gas separation plate is thinner than the ribbed separator type, it is still possible to form an external reservoir. In addition, the region t2 with poor gas sealing and thermal conductivity and the cell thickness t are somewhat improved compared to the ribbed electrode type.

However, in the hybrid type, the grooves are formed only on one side of the gas separation plate, so the gas separation plate is easily distorted and easily cracked.
It has the disadvantage that it is difficult to smooth even when surface pressure is applied, and this is an almost fatal disadvantage. Another disadvantage is that it requires high cost because grooves must be formed on both the gas separation plate and the base material.

As explained above, there are still problems with any of the above three types.

[Problems to be Solved by the Invention] As described above, conventional stacked fuel cells have a number of problems regardless of their configuration.

This invention was made to solve the above-mentioned problems, and it has sufficient gas diffusivity and electrolyte reserve amount, and the area required for gas sealing is small, making gas sealing easy. The objective is to obtain a stacked fuel cell that is comprehensively superior to conventional ones, such as superior thermal conductivity and easy external electrolyte replenishment.

[Means for solving problems]

The stacked fuel cell according to this invention has a thickness of 0.3 mf.
An oxidizer electrode base material that has been subjected to fa water treatment with a thickness of f or more and 0.5 mm or less, a fuel electrode base material that has a thickness of 0.81 or more and 3.21 or less and that has not been subjected to 1B water treatment, and a gas separation plate. and an external reservoir having a porous base material, which is disposed in the fuel electrode base material and comes into contact with the fuel electrode base material.

[Effect]

Since the oxidant electrode base material in this invention has a thickness of 0.3 mm or more and 0.5 mm or less and has been subjected to water repellent treatment, inhibition of gas diffusivity within the base material can be kept to a minimum. In addition, since the fuel electrode base material has a thickness of 0.8 mm or more and 3.21 mm or less and is not water-repellent treated, a sufficient amount of electrolyte reserve and gas diffusivity can be obtained, and the area where gas sealing is required can be sealed using a ribbed separator type. Although it is slightly larger than the ribbed electrode type and hybrid type, it is much smaller than the ribbed electrode type and hybrid type, so it is easy to seal gas and has good thermal conductivity.

Further, the external reservoir in contact with the fuel TL electrode base material increases the reserve capacity of the fuel electrode base material and facilitates replenishment of electrolyte from the outside.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a sectional view showing a stacked fuel cell according to an embodiment of the present invention. In the figure, (25) is the oxidant electrode base material (
5) is a gas sealing part made of a backing material provided at the periphery of the cell reaction area; (26) is an external reservoir provided on the gas separation plate ql and having a porous base material; in this example, the fuel electrode base The material (2) has a wet gas seal (9) at the periphery of its cell reaction area and an external reservoir (26).
is the wet gas seal part (9) and this wet gas seal part (9).
) is in contact with both of the inner fuel electrode base materials (2).

The characteristic feature of this example is that the oxidant electrode base material (
5) and the fuel electrode base material (2) are significantly different in specifications. First, the oxidizer electrode base material (5) has been subjected to Sansui treatment, while the fuel electrode base material (2) has not been Sansui treated, and the electrode base material (5) of the oxidizer electrode has a thickness of 0.41 mm. In contrast, the electrode base material (2) for fuel snow shoveling has a value of 1.01, which is more than twice that. Of these two characteristics, thickness in particular has an extremely important meaning for battery performance. The effect will be explained based on the results of several elemental tests conducted by the present inventors.

Experiment 1 Total < ta water shown in the table 5mmffi* without water treatment
One 4 cm x 4 cIl specimen for each substrate.
Approximately 0 sheets were produced, washed with ultrasonic waves in seton, and dried.

The base material A is generally called carbon paper, is flexible like paper, and is generally used as a ribbed separator type electrode base material. Also, base material B
-E are both carbons that are generally used as electrode base materials for ribbed electrodes, and are porous and plate-like and have no flexibility at all. These base materials were prepared by adding a predetermined amount of 105% by weight phosphoric acid and holding at 190°C for a day and night.
An aluminum plate with a hole of φ was attached to a base material using double-sided tape, and gas permeability was measured at room temperature using a B-type Gurley desometer to evaluate gas diffusivity. The purpose of this experiment was to investigate to what extent gas diffusivity is inhibited when electrolyte is retained on each base material. Figure 2 shows the results in a graph. The horizontal axis is phosphoric acid type 1 (sg/c■2) (105W10H3PO4
), the vertical axis is the air permeability (ml/min, cm”, smAg)
shows. When phosphoric acid is not retained, base material A, which is thin and has a high porosity, has an outstandingly high air permeability, indicating that it has extremely good gas diffusivity. However, when phosphoric acid is retained, the air permeability of base material A rapidly decreases with a small amount of retained phosphoric acid compared to other base materials. The air permeability is 20m1/min, cn”, m from another experiment.
If the air permeability is less than 7n+I/min, the air diffusivity at the oxidizer electrode will be insufficient and the cell characteristics will deteriorate.
, cm", mm It is known that when the air permeability is less than Ag, the hydrogen diffusivity at the fuel electrode becomes insufficient and the cell characteristics deteriorate.

In base material A, gas permeability begins to decrease rapidly with a retained amount of phosphoric acid of only 10 g/cs+";
), (6) and the amount of phosphoric acid held in the matrix Tll is about 40 vg/cm'', so the reserve amount is only 25χ. Considering the functionality of replenishing phosphoric acid when it is insufficient in the catalyst layer or matrix, the reserve amount is 2 to 3 times, that is, 80
~120 mg/cm" It may be misleading to say that it is necessary, but considering the expansion rate of phosphoric acid and the disappearance of phosphoric acid, it is about the same amount as the amount of phosphoric acid contained in the catalyst layer and matrix, or 40 mg/cm." degree is necessary, at least 20
A reserve amount of approximately +ag/cm" is considered necessary.

Note that the base material A is considered to be of almost the same standard as the base materials A to D shown in Table 1 of JP-A-53-30747;
A volume of 1011 g/cIlz of phosphoric acid corresponds to a porosity of substrate A of about 25χ.

Experiment 2 In order to investigate the effect of base material thickness on air permeability when impregnated with phosphoric acid, the same material as base material A but with a different thickness was impregnated with phosphoric acid equivalent to the porosity of 12χ. , Gas permeability was evaluated in the same manner as in Experiment 1. The results are shown graphically in FIG. The horizontal axis shows the base material thickness [■], and the vertical axis shows the air permeability (ml/1llin, cm", msAg). As the base material thickness increases, the air permeability worsens, but no rapid decrease is observed. In terms of actual batteries, this experiment corresponds to the evaluation of the gas permeability of the reaction gas that passes through the base material directly above the channel recess.Figures 5 and 6 show the results when the base material is thin and This figure shows how the reactant gas reaches the catalyst N (3) from the reactant gas flow path (22) in the thick case and in the thick case, and the gas flow in Experiment 2 corresponds to the broken line arrow in the figure.

However, the reaction takes place in the catalyst layer (
3), and in this case, contrary to Experiment 2, it is predicted that the thinner the base material is, the more difficult it is for gas to permeate (solid line arrow in the figure). Therefore, in order to investigate the gas permeability in the lateral direction, the following experiment 3 was conducted.

Experiment 3 For the same sample as Experiment 2 conducted earlier, 21.5φ
With the aluminum foil with the holes still attached, we covered the entire back side with aluminum foil so that gas could only pass through horizontally and not vertically.The air permeability was measured and the results are shown in Figure 4. . However, in this case, the horizontal air permeability is treated as a unit in the same way as the vertical air permeability, but the definition is different, so the absolute value of the numerical value should be compared in Figures 3 and 4. The result is that the base material thickness is 0.8 mm.
Below that, the air permeability decreases rapidly, and the rapidity of this decrease was unexpected. This result is
Even if only 12χ of the porosity of the base material is occupied by phosphoric acid, if the base material thickness is less than 0.8 mm, the gas permeability directly above the channel convex portion (23) will be insufficient, and the overall This suggests that the cell characteristics deteriorate.

From the above elemental tests, definitive suggestions regarding the structure of the battery were obtained. In other words, in order for the base material to have a reserve function, the thickness of the base material must be 0.8 mm or more. This also applies to the ribbed electrode type, which is limited to the ribbed 7' pallet type. In the ribbed electrode type, a flow path is formed in the base material, but if the convex part of the flow path (rib part) of the base material is impregnated with electrolyte, the gas flow at the convex part of the flow path of the base material is also impregnated. Diffusion is the problem. Therefore, JP-A-58-68
As described in the specification of No. 881, complicated structural improvements such as making the bore diameter of the flat seat part larger than the lip part so that the seat part is not impregnated with electrolyte are inevitably required. There is.

In addition, the ribbed separator type with a reserve function added to the base material has not been put into practical use since it was disclosed in JP-A-53-30747, and most research institutes are using the ribbed electrode type. is selected.

This is because in the separator type with ribs, carbon paper of around 0.4-1 is always used, and thicker base materials have not been attempted, so it is impossible to give the base material a reserve function in the separator type with ribs. It is presumed that this was because it was judged to be impossible and insufficient.

However, in the configuration according to the embodiment of the present invention shown in FIG. 1, which uses a separator with lips, it has overall superior performance and reserve function than any of the past types.

That is, in the example shown in Fig. 1, by setting the base material of the fuel electrode to 1.0 mm, sufficient reserve amount and gas diffusivity are obtained, and the disadvantages of using a ribbed separator are eliminated. ing.

Also, the area t2 where gas sealing is required is 2,0+Wffi
It is slightly larger than the 1.4 mm of the ribbed separator type (Figure 8), but the ribbed electrode type (Figure 9) has a length of 4.2 mm.
It is much smaller than the hybrid type (Fig. 10).

If the upper limit of the region t2 where gas sealing is required is 4.2+i+*, which is the same as the ribbed electrode type, the thickness of the fuel electrode base material can be increased to 3.2 mm in the example shown in Figure 1. It is. On the other hand, if the thickness of the base material of the fuel electrode is set to 0.8 mm, which is the limit for gas diffusion, the gas seal area 1. can be lowered to 1.8II1m.

Therefore, the structure of the present invention is considered to be good in terms of gas sealing properties and heat conduction.

On the other hand, the overall thickness is 5.0 mm in Figure 1, which is slightly larger than the 4.411111 of the separator type with lips (Figure 8), but the same as 5.0 mm of the electrode type with lips (Figure 9). .

Furthermore, since the base material is a flat plate, it is easier to handle compared to electrodes with lips, and because it is thick at 0.8 mm or more, it has sufficient strength. Furthermore, since the separator with lip is the same as the conventional one, an external reservoir (26) can also be formed. Furthermore, since there is no need to form irregularities on the base material, the cost is low.

On the other hand, for the acid and other agent electrodes, the thickness of the base material is 0.4ffi+
*By applying water repellent treatment, inhibition of gas diffusion within the base material is kept to a minimum. ! Ω water treatment is 4
This may be carried out by attaching or coating a water-repellent material such as a hydrophobic resin such as a fluorinated ethylene resin or a 4-fluorinated ethylene-67 fluorinated propylene copolymer resin, or fluorinated graphite to the base fiber. This is the same as in the case of the conventional lip separator type disclosed in, for example, Japanese Unexamined Patent Publication No. 61-99272. The thickness of the base material of the oxidizing agent electrode treated with ta water is as shown in Figs.
From the same viewpoint as the experiment shown in the figure, the allowable range is 0.3 to 0.5 mm.

Regarding the electrode type with lip, even if the base material of the oxidizer electrode is treated with T8 water, the electrolyte is reserved without water repellent treatment (even if it is not initially reserved, if it is reserved on the fuel electrode side, it can be moved). Even in the case where the gas is balanced by 0, the diffusivity of the gas in the base material is inhibited and 0□gain (difference in output voltage between the characteristics when the gas used as the other agent is oxygen (0,) and the characteristic when air is used) is around 90 mv. On the other hand, in the case of the embodiment of the present invention, the 02 gain is around 80 sv, and the output voltage is improved by 10 mV compared to the lipped electrode type.

Now, the characteristics of the embodiment of this invention shown in FIG. It is characterized in that the reservoir (26) is in contact with a base material that has not been treated with TA water, and that it straddles the wet seal portion (9) and the base material (2). In the conventional separator type with lip, the 8th
As shown in the figure, electrolyte is supplied to the matrix fl+ from an external reservoir (24) through a wet seal (9). Therefore, in order to supply the electrolyte near the center of the battery, it had to travel a long distance through the matrix, and an extremely long time was required to replenish the electrolyte. However, according to the battery configuration of the present invention, for example, when the external reservoir (24) is brought into contact only with the wet seal part (9), the electrolyte that has moved from the external reservoir to the wet seal part (9) is larger than the electrolyte in the matrix. It moves to the non-18 water base material (2) with a high movement speed. Since the electrolytic solution moves quickly within the base material (2), the electrolytic solution moves in the direction of the battery surface, and the electrolytic solution moves to the matrix via the catalyst layer.

Therefore, the electrolyte replenishment speed is dramatically improved compared to the conventional method. Conventionally, an external reservoir was not installed when the base material had a reserve function, but it can be used to reduce the concentration of the electrolyte in the entire battery by adding water to prevent the electrolyte from freezing. It is also effective to use an external reservoir mechanism that has a fast replenishment speed. 1! To replenish the electrolyte, the electrolyte is dripped from the top to the bottom of a stacked fuel cell as described in JP-A No. 61-47074, which uses a ribbed electrode type in which the base material has a reserve function. Using an external reservoir mechanism as in the embodiment of the present invention is easier and more reliable in determining the amount of electrolyte to be replenished than the method of absorbing the electrolyte into the electrode base material with a lip.

Furthermore, the external reservoir also has the role of preventing the electrolyte in the wet gas seal from running out, and the external reservoir that is in contact with the wet gas seal fully fulfills this role. However, when the electrolytic solution moves to the base material through the wet seal part, the moving speed in the warm seal part is relatively slow, so that it is slower than the original moving speed in the base material. However, if an external reservoir (26) is provided that spans both sides as in the embodiment shown in FIG. Since the electrolytic solution can be moved to the base material (2) without going through it, there is an effect that the moving speed can be further increased. In FIG. 1, the gas seal on the oxidizer electrode side is a seal made of a backing material (25), but it may be a wet gas seal.

FIG. 7 is a sectional view showing a stacked fuel cell according to another embodiment of the present invention. In this example, the wet gas seal part (
In addition to the first external reservoir (27) in contact with the base material (2), there is another second external reservoir (28) in direct contact with the base material (2).
has been set up. That is, the first external reservoir (27
) is used exclusively for maintaining the gas sealing property in the wet seal part (9), and the second external reservoir (28) is used to supply electrolyte to the base material (2), to dilute the electrolyte to replenish water, and to dilute the electrolyte to the base material. (2)
It can be used as an extension of the reserve function, etc., and the functionality can be further enhanced by the culture of the function.

Regarding the porous member installed in the external reservoir,
It is desirable that the average pore diameter of the porous member is greater than or equal to the average pore diameter of the electrode base material of the fuel electrode due to its role of supplying electrolyte to the base material, but it is important to maintain gas sealing properties in the wet gas sealing part (9). Regarding the dedicated first external reservoir (27), it is preferable that the average pore diameter of the porous member is smaller than the average pore diameter of the electrode base material so that the electrolyte is sufficiently retained. Regarding the external reservoir (28) of the second option, the electrolytic solution does not necessarily need to be held there, and the average pore diameter of the porous member disposed here may be even larger.

In the above embodiment, the oxidant electrode and the fuel electrode are positioned with the oxidant electrode facing upward, but the same effect may be obtained even if the position is reversed.

〔Effect of the invention〕

As described above, according to the present invention, the oxidizing agent electrode base material has a thickness of 0.31 or more and 0.5suw or less and has been subjected to tθ water treatment, and a thickness of 0.81 or more and 3.21 or less and that has undergone water repellent treatment. Since the oxidizer electrode includes a fuel electrode base material that is not coated, and an external reservoir that is disposed on the gas separation plate and abuts the fuel electrode base material and has a porous base material, the oxidant electrode has a Gas diffusivity inhibition is kept to a minimum, sufficient electrolyte reserve amount and gas diffusivity are obtained at the fuel electrode, and the area required for gas sealing is slightly larger than that of the ribbed separator type. Because it is much smaller than the hybrid type, gas sealing is easy and it has excellent thermal conductivity.Furthermore, the external reservoir further enhances the electrolyte reserve function of the fuel electrode base material and makes it easy to replenish electrolyte from the outside. This has the effect of providing a stacked fuel cell with overall excellent performance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a stacked fuel cell according to an embodiment of the present invention, FIGS. 2 to 4 are characteristic diagrams showing the results of element tests according to an embodiment of the present invention, and FIGS. 6 is an explanatory diagram illustrating an element test according to one embodiment of the present invention, FIG. 7 is a sectional view showing a stacked fuel cell according to another embodiment of the present invention, and FIGS. FIG. 2 is a cross-sectional view showing a stacked fuel cell. In the figure, (1) is the electrolyte retention matrix, (2)
, (5) is an electrode base material, (3), (6) is a catalyst layer, (4)
is the fuel electrode, (7) is the oxidizing agent electrode, (9) is the wet gas seal, α is the gas separation plate, αυ is the oxidizing gas flow path, and is the fuel gas flow path, (24), (26) , (27)
, (28) is an external reservoir. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (9)

[Claims] (1) A unit cell in which an oxidizer electrode and a fuel electrode each having a porous electrode base material and a catalyst layer provided thereon are arranged with the catalyst layers facing each other with an electrolyte retention matrix interposed therebetween; In a stacked fuel cell in which a plurality of oxidant gas flow channels facing the oxidizing agent electrode and gas separation plates each having a fuel gas flow path facing the fuel electrode are alternately laminated to form a laminate, the oxidizing The thickness of the electrode base material is 0.3m.
m or more and 0.5 mm or less, and the fuel electrode base material has a thickness of 0.8 m or more and 3.2 mm or less and has not been subjected to water repellent treatment, and A stacked fuel cell characterized in that the gas separation plate has a porous material and an external reservoir is disposed in contact with the fuel electrode base material. (2) The stacked fuel cell according to claim 1, wherein the fuel electrode base material has a gas seal portion at the periphery of the cell reaction area. (3) The stacked fuel cell according to claim 2, wherein the external reservoir is provided in contact with the fuel electrode base material inside the gas seal portion. (4) The stacked fuel cell according to claim 2, wherein the gas seal portion is a wet gas seal portion, and the external reservoir is provided in contact with the wet gas seal portion. (5) The stacked fuel cell according to claim 2, wherein the external reservoir is in contact with both the wet gas seal portion and the fuel electrode base material inside the wet gas seal portion. (6) The external reservoir includes a first external reservoir that comes into contact with the wet gas seal and a second external reservoir that is provided separately from the first external reservoir and comes into contact with the fuel electrode base material inside the wet gas seal. Claim 2: A small-sized stacked fuel cell. (7) The laminated type according to any one of claims 1 to 6, wherein the average pore diameter of the polymorphic material of the external reserve is greater than or equal to the average pore diameter of the fuel electrode base material. Fuel cell. (8) The stacked fuel cell according to claim 6, wherein the average pore diameter of the polymorphous material of the first external reservoir is smaller than the average pore diameter of the electrode base material. (9) The stacked fuel cell according to claim 8, wherein the average pore diameter of the porous base material of the second external reservoir is larger than the average pore diameter of the porous base material of the first external reservoir.