JPS6310468A - 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 applying water repellent treatment to an oxidizing agent substrate having a thickness of 0.3-0.5mm, and applying no water repellent treatment to a fuel electrode substrate having a thickness of 0.8-3.2mm. CONSTITUTION:An oxidizing agent electrode substrate 5 having a thickness of 0.3-0.5mm to which water repellent treatment is applied and a fuel electrode substrate 2 having a thickness of 0.8-3.2mm to which no water repellent treatment is applied are used. Water treatment is applied to the substrate 5 and no water treatment is applied to the substrate 2. The thickness of the substrate 5 is 0.4mm and that of the substrate 2 is 1.0mm which is two times or more. Thereby, sufficient gas diffusion capability and the sufficient amount of electrolyte reserve are ensured. The region where gas sealing is required is reduced and gas sealing is made easy, and furthermore, installation of external reservoir is easy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a stacked fuel cell, and particularly to the structure of the cell.

[Conventional technology]

As is well known), a fuel cell consists of a fuel T1. It is a type of power generation device that is operated by supplying fuel and oxidizer to the pole and oxidizer, respectively.

Fuel cells have the following characteristics: ■ 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 even if the output is changed. ■It has advantages such as excellent responsiveness to load fluctuations), and can be used for distributed R9 equipment on the scale of distribution substations in or near cities, or as an alternative power generation equipment for thermal power plants. The form is being 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 conventional type of phosphoric acid fuel cell is the lip separator type, which is disclosed in U.S. Patent No. 3.86Z.
, Specification No. 206 (Special Publication No. 58-152),
U.S. Patent No. 4,276.355
A typical battery configuration is described in Japanese Patent No. 6067). FIG. 8 is a cross-sectional view showing a typical configuration of the attached separator type. In the figure, fi+ is an electrolyte holding matrix, (4) is a fuel vIL electrode, (2) is an electrode base material of a fuel electrode, (3) is the catalyst layer of the fuel ta, (7) is the oxidizer electrode, (5) is the electrode base material of the oxidizer electrode, (6) is the catalyst 1 of the oxidizer electrode, (81 is the wet gas of the fuel gt electrode) The seal part, (9) is the wet gas seal part of the oxidizer electrode, and the symbol is the gas separation plate (also called a T-bar, bipolar plate, interconnector, etc.), (1)) Vi oxidizer gas flow. The path and α line are the fuel gas flow path (orthogonal to the oxidant gas flow path). Reactant gas flow path (+1) on gas separation plate -,
(It is called a separator type with a lip because it is formed with a l.) Wet gas seal part (81, +91 may be replaced with a gas seal made of a nohetsuki material. (tl) is a single lip. Indicates the thickness of the cell structure.In general, in the case of glued separator type, the gas separation plate (IC)
4 is about 31) 1), the base materials f21 and +51 are each about 0.4 am, and the total of the catalyst layers f31 and +61 and the electrolyte holding matrix layer (1) is about 0.61 am, so (tx) The thickness is approximately 4.4*m.

While the gas separation plate is air-impermeable, the base material (21
, [51 are porous, so sufficient gas sealing is required in the range (+2). In the case of the attached separator type (+2), the thickness is approximately 1.4 mm, and the thicker the thickness, the more the gas seal becomes spaced apart. Also,
While the gas separation plate 001 is made of dense carbon and has good thermal conductivity, the base material f21. +51 is porous and more than 50% is occupied by gas (air or fuel), so it has poor thermal conductivity.

In addition, the electrolyte retention matrix Fig (tltl electric heating is poor. Therefore, (+2) is also a region with poor thermal conduction.

Stacked fuel cells typically include cooling plates inserted every fifth cell to absorb the heat generated by the cells and cool them to maintain as uniform an operating temperature as possible. Therefore, the thicker the (+2) thickness, the more difficult it becomes to conduct heat, which causes variations in temperature in the cell stacking direction and in the plane, causing problems such as corrosion of members due to high temperatures and deterioration of cell characteristics due to low temperatures.

The first advantage of the attached separator type is that it is thinner (+2) than other types described later, so gas sealing is easy, and the second advantage is that it has good heat conduction for the same reason. is a good thing.

In the case of a t J'l layer strategy, all base materials are treated to be water repellent. This is done in order to prevent the electrolytic solution in the electrolyte matrix from flowing out into the substrate through the catalyst layer and blocking the pores of the substrate, thereby inhibiting the permeability of the reaction gas. Regarding methods of water-repellent treatment of base materials, see JP-A-60-220565 and JP-A-60-1336.
It is described in detail in Publication No. 63.

Even with 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 seal. Therefore, in the case of the attached separator type, nine parts occupied by the electrolyte are the electrolyte holding matrix (1), the catalyst layer (:ll, (81) and the wet gas seal part (1)).
), +9+. However, during long-term operation, the electrolyte accumulates due to scattering and evaporation. Therefore, by providing an external reservoir in a part of the gas separation plate (! (2)) and bringing it into contact with the wet gas seal part (81, (91) or matrix (1), it is possible to replenish the electrolyte from the outside to the matrix +1). Regarding the external reservoir, see Japanese Patent Application Laid-open No. 58-1.
It is described in detail in No. 61269 and Japanese Unexamined Patent Publication No. 59-21)969. 2-3 to form an external reservoir
It is necessary to have an unfavorable part as thick as a dragon, and the gas separation plate [+01 is most suitable as a part for forming an external reservoir, and the third advantage of the separator type with screws is that it is easy to form an external reservoir. It has become.

On the other hand, the disadvantage of the separator type with lips 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 that contained in the matrix. The volume of the electrolyte varies greatly depending on the operating conditions. This increased volume moves within the matrix and is stored in the wet seal section (81, t91 or external reservoir).
As the size of the cell increases and the distance traveled within the matrix becomes longer, the movement of the electrolyte within the matrix becomes slower than the rate of expansion of the volume, and the increased volume is absorbed by the catalyst layer [31, [61] 9)
, Furthermore, the water repellent treatment is applied to the inside of the base material (21, F51, so that it cannot return to the matrix).Then, the volume shrinks, and in case the electrolyte in the matrix is insufficient, a 03-year-old bar occurs, etc. This caused an extremely serious situation.In order to prevent the electrolyte from leaking from the matrix to the base material through 1, a layer with enhanced water repellency should be provided between the catalyst layer and the base material, as disclosed in Japanese Patent Publication No. No. 101837, 1982, JP-A-60-
170168 and Japanese Patent Application Laid-Open No. 60-241655, etc., but the effect is not sufficient, and as the area of the cell increases, the absorption function against the expansion of the electrolyte decreases in the attached separator type. The deficiencies were almost fatal flaws.

As a solution to this defect, attempts have been made for a long time to provide an absorption function (reservation function) for the expansion of the electrolytic solution inside or behind the electrode base material.

First, JP-A-47-31)37 discloses that a porous plate is placed behind the fuel electrode and an electrolyte chamber is placed behind the fuel electrode, and the electrolyte is passed through a pin 1'' to cause electrolysis within the matrix. A configuration for controlling the liquid amount is described.In addition, in JP-A-50-101836, a matrix material is placed through the catalyst layer of the fuel electrode and the tW base material to the back surface of the base material to create a reserve. A structure with a function is described in Japanese Patent Application Laid-open No. 53-32352 (
U.S. Patent No. 4.064.322) and JP-A-53-32
No. 353 (US Pat. No. 4,038,463) describes nine configurations in which a hydrophilic area and a hydrophobic area are formed inside the base material and a reserve function is provided. However, all of these configurations are extremely complex and require numerous steps to realize these configurations, resulting in high costs.Moreover, these configurations include 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. 4.03
5.551) The configuration described in the publication is very simple and simply does not provide water repellent treatment to the base material.
According to the examples in the above publication, the base material has a thickness of 0.3 m to 0.
．． 5 dragons, porosity 75-88%, average pore size 14-83
Micron carbon paper is used, and the small pores in this base material act as a reservoir for the electrolyte, and the remaining large pores act as passages for the reactant gas. It states that it must not have holes. According to this configuration, a reserve function can be added to the lip separator type by simply not applying water repellent treatment to the base material on the fuel electrode side, which has a small effect of inhibiting gas diffusivity. The reserve function was insufficient within the range of the embodiment.

The second disadvantage of the lip separator type is that the reaction gas must flow in the direction of the catalyst layer directly under the protrusion (rip) of the reaction gas flow path formed on the gas separation plate. Although there is a view that the diffusibility of the material is insufficient, as described in JP-A No. 59-73852, the generally used groove width of 1 to 1.5 yen and the thickness of the base material are This problem hardly occurs in a configuration with a diameter of 0.3 to 0.41. However, this disadvantage is serious in the case of a substrate having a thickness of 0.41 mm as described in Japanese Patent Application Laid-Open No. 59-40471, in which the catalyst layer is penetrated into the inside. In addition, even with the base material on the fuel electrode side described above that is not treated with water repellent treatment and has a reserve function, there is a problem with gas diffusivity when the electrolyte is reserved due to the thin thickness of the base material. I feel sorry for that.

The second most typical battery configuration is the separator type with a separator and an electrode with a separator. For this type, US patent 4,1)
No. 5,627, No. 4,165.349 and JP-A-58
It is described in detail in JP-A-68881.

FIG. 9 is a cross-sectional view showing a typical configuration of a beveled electrode type.

In the attached electrode type, the thickness of the base material [21, [5] is increased to 4, and a reaction gas flow path (Ill, j+2) is formed therein. Therefore, the gas separation plate (10) is a flat, thin, air-impermeable plate.

The biggest and only advantage of the attached electrode type is that it has the ability to absorb expansion of the electrolyte.

According to Japanese Unexamined Patent Publication No. 58-68881, the average diameter of the flat sheet portion of the attached base material is 25 to 45 μ2n,
The average bore diameter of the mounting part of the base material with lip is 60 to 7 of the seat part.
It is said that by setting the 5% cap to 15 to 34 μm, the electrolyte overflowing from the matrix can be selectively stored in the ridge portion which has a large capillary suction force next to the matrix. Just in case there is a shortage of electrolyte in the matrix, the electrolyte stored in the fitting will be transferred to the seat.

It is said that it is supplied to the matrix via the catalyst layer.

The thickness of the mounting base material is generally about 1.8 ff1m, f5
The total arm strength of the catalyst layer and electrolyte quality matrix layer is approximately 0.6 arm (tl
) is about 5.0 + u, and the pallet type is also slightly thicker. This is because the mechanical strength of the Rip-ft base material is weak, so it is difficult to make the seams of the RIP base material thin. Furthermore, since the base material with a lip is porous, the area where gas sealing is required is much larger than that of the pallet type with a gas seal, and the thickness is 4.2 mm, which is 3 mm. Therefore, gas sealing is difficult. This is the first disadvantage of the attached TTM type. In addition, since the area with poor heat conduction is also three times thicker than that of the glued separator type, a high-performance cooler is required and the cost is high.

This is the second disadvantage of the attached PI pole type.

In addition, the base material of RIP is porous and has weak mechanical strength, and since grooves are formed, it is easy to break in the direction square to the grooves, making it difficult to separate the hand link. 54. This is the third disadvantage of the layered type.

Furthermore, in the case of the electrode type with a magnifying hole, an external reservoir cannot be provided because the thickness of the gas impermeable gas separation plate is as thin as 0.8 mm. Further, it is difficult to provide an external reservoir in a porous substrate, and even if it is possible, the cost is high. Therefore, external replenishment of electrolyte is difficult. As a method of replenishing electrolyte for the attached electrode type, there is a method described in JP-A-61
As described in No. 47073 and No. 61-47074, a method has been adopted in which the electrolytic solution is allowed to flow from the top to the bottom of the stacked fuel cell and the electrolytic solution is absorbed into the base material with lips. There is. However, with this method, it is difficult to grasp the amount of electrolyte to be replenished for each cell, and when operating after t*m candy, the edges of the stack from top to bottom are wet with electrolyte, resulting in leakage current. There is also a risk that the battery may be damaged. Therefore, the fourth disadvantage is that it is difficult to provide an external reservoir.

Another problem with the electrode type with lips is the diffusivity of the oxidant gas within the oxidant electrode base material. Since it is not possible to reduce the thickness of the lip-attached base material to the thickness of the lip-attached separator type base material (0.3 to 0.4 sn) from the viewpoint of machine strength, first of all, an oxidizing agent is used. When water repellent treatment is applied to the electrode base material, the porosity of the base material is reduced by the water repellent, and a film of water repellent is formed between the base material fibers, which inhibits the diffusion of oxidant gas to some extent. However, in the case of the lipped electrode type, the greater the thickness of the groove, the greater the degree of diffusion inhibition compared to the lipped separator type, and the output voltage of the cell decreases accordingly. Next, if the oxidizer electrode base material is not subjected to water repellent treatment, even if the initial electrolyte is not reserved in the oxidizer electrode base material, about 5% of the electrolyte of the pore volume of the electrode base material will be removed from the oxidizer from the matrix. The oxidizing agent moves to the electrode base material through the electrode catalyst layer, and like the water repellent, the diffusivity of the oxidizing agent gas is inhibited, and the output voltage of the cell decreases accordingly. The reason why the allowable reserve value of the oxidizer vL electrode base material is smaller than that when the electrolyte is reserved in the fuel electrode base material is because the fuel gas is This is thought to be due to the difference in diffusivity between hydrogen, which is contained in large amounts, and oxygen, which is contained in the oxidant gas. Therefore, the fifth disadvantage of the electric coffin type is that the output voltage decreases due to insufficient diffusion of the oxidant gas within the oxidant electrode base material. For this purpose, the pore diameter of the web should be made as large as possible to prevent the electrolyte from being retained, as described in JP-A-58-68881, and as described in JP-A-59-27466. Adding to the web also requires changing the material within the base material (using long carbon fibers), which is expensive.

Comes with a separator mold and lip! ! In addition to the polar type, there is a hybrid type which is a compromise between these two types and is disclosed in Japanese Patent Laid-Open No. 58-94768. FIG. 10 is a sectional view showing the configuration of this hybrid type. In the hybrid type, there is a strip on the oxidizer electrode side.
A J<rate type configuration is used, and a lipped electrode type configuration 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 is the fifth disadvantage of the oxidizer electrode base material. Improved gas diffusivity.

Also, although it is thinner than the separator type gas separation plate with a beam, it is possible to form an external reservoir. Also, the gas seal and heat conduction eye area t2 and the cell thickness tl
is somewhat improved over the electrode type with lip.

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 cracked, and it does not remain smooth even when surface pressure is applied.This is an almost fatal disadvantage. It becomes. 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 three types mentioned above.

[Problem that the invention seeks to solve]

Conventional stacked fuel cells have a number of problems, as described above, regardless of their configuration.

This invention was made to solve the above-mentioned problems, and it has sufficient gas diffusivity and electrolyte reserve, and the area required for gas sealing is small, making gas sealing easy and heat-resistant. The object of the present invention is to obtain a stacked fuel cell that is superior in terms of overall conductivity compared to conventional methods, such as superior conductivity and the ease of forming an external reservoir on the gas separation plate.

[Means for solving problems]

The stacked fuel cell according to the present invention includes an oxidizer electrode base material having a thickness of 0.3 mm or more and 0.5 wm or less and treated with water repellency, and a thickness of 0.8 sn or more and 3.2 u or less. It has a fuel electrode base material that has not been subjected to water repellent treatment.

[Effect]

Since the oxidizer electrode base material in this invention has a thickness of 0.3 mm or more and 0.5 am or less and is treated with water repellent treatment, gas diffusion t4 within the base material can be minimized. . In addition, the fuel electrode base material has a thickness of 0.8 wm or more and 3.2
Since water-covering treatment is not performed below u, a sufficient amount of electrolyte reserve and gas diffusivity can be obtained, and the region t2 where gas sealing is required is also suitable for use with lip-attached separator types, slightly larger lip-attached electrode types, and hybrid types. Yoshi is also much smaller,
Gas sealing is easy and thermal conductivity is good. Furthermore, since it is a separator type with a mounting plate, there are many advantages such as the ease of forming an external reservoir on the gas separation plate.

〔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.

What is distinctive about this figure is the t-type base material (I) of the oxidizer electrode.
The specifications of the sl and the fuel electrode base material (2) are significantly different. First, oxidizer 1! While the 'gLi base material (5) of the electrode is treated to be water repellent, the fuel electrode base material (2) is not treated to be water repellent. The electrode base material (6) of the peroxidant electrode is 0
．． The thickness of the fuel electrode base material (2) is 1.0 mm, which is more than twice as thick as that of the fuel cell electrode base material (2). Of these two characteristics, the thickness in particular has a very important meaning for the performance of the battery. The effect will be explained based on the results of several elemental tests conducted by the present inventors.

Experiment 1 About 10 test pieces of 4 m x 4 cm were made for each of the 5 types of base materials shown in the table that had not been treated with any water repellent treatment.

Clean by ultrasonication in acetone and dry thoroughly. The base material A is generally called carbon paper, which is flexible like paper and is generally used as a seed base material of a glued separator type. Further, both base materials B and I are made of carbon and are generally used as electrode base materials of the attached electrode type, and are porous 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 keeping at 190°C for a while, then attaching an aluminum plate with a hole of 21.5φ to the base material using double-sided tape.
Gas permeability was measured at room temperature using a Gurley densometer, and gas diffusivity was evaluated. The purpose of this experiment was to investigate to what extent gas diffusivity would be inhibited if electrolyte was retained on each base material. Figure 2 shows the results as a club.

The hammer shaft is phosphoric acid weight Ctrq/cd) (iosw//,
H, po, ), the vertical axis is the air permeability (ml/oa in
, crl, mark Age).

In the case where phosphoric acid is not retained, the base material is thin and has a high porosity, and the air permeability is extremely high, indicating extremely good gas diffusivity.

However, in the case where phosphoric acid is retained, the air permeability of base material A rapidly decreases due to a small amount of retained phosphoric acid compared to other base materials. The air permeability is 20 d/m from another experiment.
If the air permeability is below 7 d/min, a/l゛, mmAg, the air diffusivity at the oxidizer electrode will be insufficient and the cell characteristics will deteriorate. It is known that if this happens, hydrogen diffusivity at the fuel electrode becomes insufficient and cell characteristics deteriorate. In base material A, gas permeability begins to decrease rapidly with a phosphoric acid content of only 10 Mq/-; The amount of phosphoric acid retained in +61 and matrix +1) is 40y
Since it is about y/i, the reserve amount is only 25%.
It's nothing more than that. Considering the functionality of collecting phosphoric acid when it overflows from the catalyst layer or matrix and replenishing it when there is insufficient phosphoric acid in the catalyst layer or matrix, JP-A-53
30747 Specification P 230, it seems that it is too much if the reserve amount is required to be 2 to 3 times the amount of 80 to 20 M9/-, but the expansion rate of phosphoric acid and the phosphoric acid Considering the disappearance of phosphoric acid, it is thought that a reserve amount of about 40~/cd is required, which is the same as the amount of phosphoric acid contained in the catalyst layer or matrix, and a reserve amount of at least about 20~/cd is required.

The base material 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;
The volume of 10η/d phosphoric acid is approximately 25% of the porosity of base material A.
corresponds to

Table Experiment 2 In order to investigate the effect of base material thickness on air permeability when impregnated with phosphoric acid, a material of the same material as the base material λ but with a different thickness was impregnated with phosphoric acid equivalent to 12% of the porosity. 9. Gas permeability was evaluated in the same manner as in Experiment 1. The results are shown in Figure 3 using clubs. The axis shows the base material thickness (,,), and the vertical axis shows the air permeability (ml/min, cyl, mmAg). Although the air permeability worsened as the base material thickness increased, no rapid decrease was observed. In terms of an actual battery, this experiment corresponds to evaluating the gas permeability of the reaction gas that passes through the base material directly above the channel recess. Figures 5 and 6 show how the reaction gas reaches the catalyst layer (3) from the reaction gas flow path (■) when the base material is thin and when the base material is thick. Corresponds to a medium-dashed arrow.

However, the reaction also occurs in the catalyst layer (3) directly above the convex part of the reaction gas flow path, 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, the following experiment 3 was conducted to investigate the gas permeability in the direction of fear.

Experiment 3 For the same sample as Experiment 2 conducted earlier, 21.5φ
(Leave the aluminum plate with the holes in it open and then cover the entire back side with aluminum plate.) Check the air permeability by making sure that gas cannot pass through vertically but only horizontally. It is shown in Figure 4.

As a reminder, the horizontal air permeability in this case is treated as a unit in the same way as the vertical air permeability, but the definitions are different, so the absolute values of the numerical values are compared in Figures 3 and 4. I can't. The results showed that when the base material jγ was 0.8 am or less, the air permeability decreased rapidly, and the rapidity of this decrease was unexpected.

This result shows that even if only 12% of the porosity of the base material is occupied by phosphoric acid, if the base material thickness is less than 0.81, the gas permeability directly above the channel convex portion 4 will be insufficient. C,
This suggests that the overall cell properties are degraded.

From the above elemental tests, definitive suggestions regarding the structure of the battery were obtained. ) In order for the base material to have a reserve function, the thickness of the base material must be 0.8 am or more. This applies not only to the separator type with grooves but also to the wL pole type with grooves.

In the lip-equipped electrode type, a groove is formed on the base material, but if the convex part of the flow path of the base material is impregnated with electrolyte, the convex part of the flow path of the base material is no longer the same. The problem is gas diffusion.

Therefore, as described in JP-A No. 58-68881, the bore diameter of the flat seat part is made larger than that of the rib part to prevent the seat part from being impregnated with electrolyte. Improvements are inevitably needed.

In addition, the idea of adding a reservoir function to the base material with a separator type has not been put into practical use since it was disclosed in Japanese Patent Application Laid-Open No. 53-30747, and it has not been put to practical use in most research institutes. The tane type has been selected for the dzutsuke. This is because carbon paper of around 0.4 mm is always used in the separator type with adhesive, and no attempt has been made to use thicker base materials, and it is impossible to give the base material a reserve function in the separator with adhesive. It is presumed that this is due to the fact that the film was judged to be sufficient.

However, although the structure according to the embodiment of the present invention shown in FIG. 1 uses a separator with a lip, it has overall superior performance and reserve function compared to any of the past types. That is, in the embodiment shown in FIG. 1, the base material of the fuel electrode is 1. OZW provides a sufficient reserve amount and gas diffusivity, and the disadvantages of using a separator with lips and holes are eliminated. Also, the area t2 that requires gas sealing is 2. The diameter of 1.41 mm for the separator type with a series (Fig. 8) is also a little larger, but it is 4.2 mm for the separator type with a series (Fig. 9) and the hybrid type (1.4 mm).
Figure 0) The diameter is also much smaller. If the upper limit of 2 is the same as W with lip and pole type, the area where gas seal is required is 4.2.
In the case of the embodiment shown in Fig. 1, the thickness of the fuel electrode base material is 3.21 mm.
It is possible to make it thicker. On the other hand, if the thickness of the base material of the fuel electrode is set to 0.8 mm, which is the tolerance value from gas diffusion, the gas seal area t2 can be reduced to 1.8 mm. 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 0.5 mm in Figure 1, and 4.4 am for the Separated Overnight type (Figure 8), which is a little larger. It is the same as 5.0mm in Figure).

The f& base material is easier to link by hand compared to the flat plate with Karadzu-attached poles, and is thick at 0.8 mm or more, so it has sufficient strength. Since the separator with the attached separator is the same as the conventional one, an external reservoir 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, as for the oxidizer electrode, the thickness of the base material is 0.4 am, and by applying water repellent treatment, inhibition of gas diffusivity within the base material is kept to a minimum. Water-repellent treatment is performed by attaching or coating the base fibers with hydrophobic resins such as tetrafluoroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, or water-repellent materials such as fluorinated graphite. It's fine. This is, for example, JP-A-61
This is the same as the case of the conventional glued separator type shown in Japanese Patent No. -99272. Regarding the thickness of the base material of the water-repellent oxidizing agent wL koshi, from the same viewpoint as in the experiments shown in Figs. 3 and 4, the thickness of the base material of the oxidizing agent wL koshi is 0. .3 to 0.5+ym is an acceptable range.

Regarding the fixed electrode type, even if the base material of the oxidizer electrode is water-repellent, the electrolyte is reserved without water-repellent treatment (even if it is not initially reserved, if it is reserved on the fuel electrode side) % o2 gain (difference in output voltage between characteristics when the gas used as an oxidizing agent is oxygen (02) and air). ) will be after 90mv:Q. On the other hand, in the case of the embodiment of the present invention, the 02 gain is around 8Qmv, and lQmv is also improved compared to the output voltage burr poled type.

Now, according to the cell configuration according to an embodiment of the present invention shown in FIG. 1, a single cell of a phosphoric acid fuel cell with an effective area of 100 d is made and operated under normal pressure conditions of 190°C, and during operation, fuel Check the performance of the pole side and the amount of phosphoric acid reserved in the base material 100
%H3P041 Occupancy rate of phosphoric acid on the substrate at 90°C (initial impregnation amount) [V/. ] and the degree of inhibition of combustion gas diffusion. The performance of the fuel electrode side is f(2 gain (difference in output voltage between the following case using hydrogen (H2) as the fuel gas and the case using 80 volume percent hydrogen and 20 volume percent carbon dioxide) (evaluated in mV:l) The results are shown in Figure 7.The base material on the fuel electrode side had the same composition as E in the table, and the base material on the oxidizer electrode side had the same composition as the human body.H2 The larger the gain, the greater the degree of inhibition of gas diffusivity in the base material.
3 of the porosity of the base material in both wx and 1.8+u
It has become clear that even when reserved to 0%, there is almost no inhibition of js diffusivity in the base material on the fuel electrode side. In contrast to Figure 2, this reserve amount is equivalent to a thickness of 1
) 35■/su in the case of Tomi, 60η/- in the case of 1.8 dragon
This corresponds to the amount of phosphoric acid (105 weight) I3po, ), which is a sufficient amount as a reservoir.

The electrode base material constituting the fuel cell has a pore volume of 20
Preferably, ~30% of the volume of electrolyte is impregnated during operation.

〔Effect of the invention〕

As described above, according to the present invention, an oxidizing agent electrode and a fuel electrode each having a porous electrode base material and nine electrodes 71 arranged thereon are interposed with an electrolyte holding matrix,
X, a plurality of unit cells in which FfJs are arranged facing each other, and gas separation plates each having an oxidizing gas flow path opposite to the oxidizer electrode and a fuel gas flow path opposite to the fuel electrode are alternately arranged. In a stacked fuel cell in which layers are stacked to form a laminate, the oxidant electrode base material has a thickness of 0.3 m or more and 0.5 m.
The fuel electrode base material has a thickness of 0.81 to 3.2 mm and is not treated to be water repellent. The gas diffusivity inhibition within the base material is kept to a minimum, and sufficient electrolyte reserve and gas diffusivity are obtained in the fuel electrode, and the area where gas sealing is required is slightly larger than the separator type. However, it is much smaller than the fixed electrode type and high-density type, so it is easy to seal with gas and has excellent thermal conductivity. Furthermore, it is possible to easily form an external reservoir on the gas separation plate, and as a result, a stacked fuel cell having excellent overall performance can be obtained.

[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, and 7 are characteristic diagrams showing the results of element tests according to an embodiment of the present invention. FIGS. 5 and 6 are explanatory views for explaining element tests according to an embodiment of the present invention, and FIGS. 8 to 10 are cross-sectional views showing conventional stacked fuel cells, respectively. In the figure, m is the electrolytic retention matrix (2). (5) is an electrode base material, [31, [61 is a catalyst layer, (4) is a fuel electrode, (7) is an oxidizer electrode, +101 Vi gas separation plate, (1)) is an oxidant gas flow path, 0 '4 is a fuel gas flow path. Note that the same reference numerals in each figure indicate corresponding parts.

Claims (4)

[Claims] (1) A unit cell in which an oxidant 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 holding matrix interposed therebetween; In a stacked fuel cell in which a plurality of oxidant gas flow paths facing the electrodes and gas separation plates having fuel gas flow paths facing the fuel electrodes are alternately laminated to form a laminate, the oxidizer The electrode base material has a thickness of 0.3mm
It has been treated to be water repellent to a depth of 0.5 mm or less,
A stacked fuel cell characterized in that the fuel electrode base material has a thickness of 0.8 mm or more and 3.2 mm or less and is not subjected to water repellent treatment. (2) The oxidizer electrode base material is water repellent to the electrolyte,
The stacked fuel cell according to claim 1, wherein the fuel electrode base material is hydrophilic to the electrolyte. (3) The oxidizer electrode base material has its pores impregnated with a hydrophobic resin, and the hydrophobic resin is melted and solidified to cover the base fibers. Stacked fuel cell. (4) The stacked fuel cell according to claim 3, wherein the hydrophobic resin is at least one of a tetrafluoroethylene resin and a tetrafluoroethylene-hexafluoropropylene copolymer resin.