JPS58100369A - Electrolyte matrix for fuel cell - Google Patents

Abstract

PURPOSE:To provide a matrix having large content of phosphoric acid, high bubbling pressure, high hydrogen ion conductivity, and easy handling by using fluorocarbon having a specific chemical formula, highly concentrated phosphoric acid, and polymer affiliated to fluoride as a binder. CONSTITUTION:A various amounts of 95% phosphoric acid are added to 100 pts.wt. white fluorocarbon powder indicated as (CF)n powder and 3pts.wt. polyfluoroethylene used as a binder, and kneaded, then compressed at 3kg/cm<3> to form about a 0.15mm. thick sheet-shape matrix. The bubbling pressure of this matrix is slightly decreased as the amount of phosphoric acid is increased as shown by a solid line 11, and the bubbling pressure of 0.3 atmospheric pressure is indicated at 120% addition. A hydrogen ion conductivity is increased with the amounts of phosphoric acid as shown by line 12. The matrix containing 120% of phosphoric acid is semisolid, and does not break under gravitation when it is held at both ends.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrolyte matrix for fuel cells having phosphoric acid as the electrolyte.

The technical background and problems of phosphoric acid electrolysis*m Fuel cells hold liquid phosphoric acid as an electrolyte between gas diffusion electrodes placed opposite each other.ft! It is used by disposing a gas diffusion electrode and passing it through a hydrogen pipe as a fuel gas containing keratin oxygen, such as an air VTE converting agent gas.

] In fuel cells using AT electrolyte, improvement of cell characteristics,
The electrolyte matrix is one of the most important components in achieving long-term stability.

In order for this electrolyte matrix to operate the fuel cell in an optimal state, the matrix base material must have the following functions.

l) Operating conditions of fuel cell (150°0~zoo'o・,
It is thermally and chemically stable at 95 to 100 degrees H, PO,).

2) It must be warm to the electrolyte and have sufficient hydrogen ion conductivity.

3) Be an electronic insulator.

4) The pond pressure must be sufficiently high to prevent the fuel gas and oxidant gas from diffusing and permeating through the matrix.

5) The kernels are as thin as possible and have a moderate Oam.

One of the conventional matrix substrates used is phenolic resin nonwoven fabric. When phenolic resin is exposed to high-temperature phosphoric acid (over 180°0) for a long period of time, it gradually undergoes an oxidation reaction, which may result in a lack of long-term stability in fuel output. Zirconium oxide (Zr
It has been reported that a cross of 15 oxides (O*) and 15 oxides of 15 oxides are combined together using a polymeric binder to form a sheet.

-However, although these oxides are chemically stable against high-temperature cynic acid, there are gaps in electrolyte retention. Besides,
Since these oxides are expensive, they are not suitable as matrix materials for large-capacity dental electronics that are used in large quantities.

On the other hand, at the operating temperature of the fuel 11a and the open circuit voltage of the electrode, it is electrochemically stable, stable for a long period of time, and is used in large quantities in various fields, so it is inexpensive. I
(8ic)lv) A fuel cell used as a fuel cell is known.

The method for producing a friendly electrolyte matrix using silicon carbide is as follows: granular N is prepared by adding and mixing appropriate amounts of a polymer, an adhesive, and a solution to fibrous silicon carbide, and then mixing the mixture with 4-&IIM, spraying, coating, Added to the electrode surface using thin film pre-7 etc.
The manufacturing method used was to dry it, remove it under strict conditions, and then impregnate it with 9-acid. In addition, as another method, a method has been proposed in which a warmed product of silicon carbide, a fixing agent, and cynic acid is applied to the surface of the electrode.

These electrolyte matrices used in silicon carbide tubes have higher bulk ionic conductivity than the matrix material in these bottles.
It can be said that the matrix has excellent characteristics such as voltage power. However, in order to further improve the cell characteristics as a fuel cell, it is necessary to increase the hydrogen ion conductivity of the matrix, and for this purpose it is necessary to add a large amount of phosphorous iron.

However, when a larger amount of phosphoric acid is added, the hydrogen ion conductivity increases, but the reverse KIllI pressure decreases, which is a good phenomenon. Also, by reducing the thickness of the matrix, the resistance of hydrogen ions can be reduced.%t)0. The voltage force is low, and the mechanical strength is reduced by 11%. Furthermore, since the absolute amount of phosphoric acid decreased, phenomena such as a decrease in the life span of the battery were observed.

The above means that in a matrix made of silicon carbide tm, l1
By improving the 4I power as an LCFK, it shows that the world of eyes is coming.

Book*Iij! Under the above circumstances, the authors searched for various suitable matrix materials to replace silicon carbide, and found 7
The tube found that carbon tsunide has good properties. Vertical fluoride generally has the chemical formula (OFm)” (0≦X≦1)
It is a type of intercalation compound represented by It is used as a matrix.

After investigating this material at various points, it became clear that it has the following functions.9.

l) As shown in FIG. 1, it is extremely stable and chemically stable, with no decomposition occurring up to 40,060 or more.

2) It has good wettability with phosphoric acid and sufficient bulk ionic conductivity.

3) (OFx) In the case of n and x=1, it is white and is an electronic insulator.

4) It has extremely excellent voltage power. 05) It can be processed thinly and is suitable for WJA II! have.

Moreover, it has been found that the above-mentioned functions are superior in various respects compared to cases where silicon carbide is used as a matrix material. This provides a matrix material that is impregnated with a large amount of phosphoric acid and has high hydrogen ion conductivity without reducing the pond pressure.

Examples of the invention Hereinafter, the present invention will be described as an example).

Example 1 100 parts of white t)fll*7 fluoride tablet expressed as (OF)n in weight ratio, polytetrafluoroethylene yago* agent as a fixing agent, and varying amounts of 95-concentrated phosphoric acid. Knead with a pressure of 3#/al" to a thickness of about 0.15
A simple sheet matrix was produced. The voltage force of this matrix and the ionic conduction at 150° C. are shown by solid lines 11.12 in FIGS. 1 and 2, respectively. Further, as a comparative example, the voltage force and the ionic conductivity t of a sheet-like matrix made of silicon carbide under the same conditions are shown in Fig. 1 and Fig. 2, respectively, with a line of 21.22.

In the matrix of the present invention, the voltage force slightly decreased as the amount of phosphoric acid increased as shown by #IIWJK, but even when 120- was added, the voltage force was 0.3 atm. On the other hand, in the matrix of the comparative example, a remarkable decrease in voltage force was observed when phosphoric acid of 100- or more was added, and in 1201G, the voltage force was 0.03 atm, which was 1/1/2 that of the matrix of the present invention.
1g KNatsu9.

In addition, the hydrogen ion conduction f is as shown in FIG.
In both comparative examples, the conduction f increases as the amount of phosphoric acid increases, but
This indicates that the real value is high.

In addition, in the present invention, even if 120 m of phosphoric acid tII is added, if the matrix is semi-solid and held at both ends, it will not break under its own weight, whereas in the comparative example, 120 m of phosphoric acid tII was added. When it was added, free phosphoric acid with fluidity stood out on the surface, and when it was held at both ends, it broke under its own weight.

As shown above, it was found that the matrix of the present invention has a higher retention amount of phosphoric acid, higher hydrogen ion conductivity, and superior mechanical strength fK than the conventional silicon carbide matrix @Example 2 Implementation At the weight ratio shown in Example 1, fluorocarbon 10011 degrees polytetrotetraethylene 311,951111 degrees 97
9110 parts of the mixture t3#/fi'' was pressure-molded into a receipt, and assembling the fuel cell stack shown in Figure 3 (main parts shown).In Figure 3, (1
) is the fuel electrode catalyst layer, and (2) is the support supporting the catalyst layer, and the commonly used carmen paper was used. For (3), Carmen paper, which is commonly used in the air electrode catalyst layer (4) mineral O support, was used. (5) is an electrolyte retention matrix according to the present invention. (6) is a bipolar separator, and 0#1 (7) is used to supply fuel gas and oxidizer gas such as air.
(8) Since the batteries are placed in the orthogonal direction one after the other, adjacent unit batteries are stacked through this.

An example of the operating characteristics of the nine fuel cells constructed as above tj
141i0. The figure shows a discharge of 11 mK per unit area.
The number p1-I shows the characteristics of the present invention, showing the voltage change of the unit battery. Also, as a comparative example, silicon carbide 1
lt- as a matrix under the same conditions as in the present invention,
As is clear from Figure 90, which shows an example of the characteristics of a similarly configured fuel cell, the voltage of the unit cell decreases as the current value increases, but the voltage decrease of the fuel cell using the matrix of the present invention is , smaller than that of the comparative example '75
Vh 6, i.e., the water volume of the matrix of the present invention 4m
Since the fuel cell was 1116%fh, it was possible to reduce the voltage decrease due to hydrogen ion resistance, and as a result, it was possible to obtain a fuel cell with a high operating voltage.

More than the effect of Yamei, (OF)n shows 1 carbon heptide and 9
The matrix using phosphoric acid of 5 or higher and fluorine-based polymer as a fixing agent has a high content of phosphoric acid,
The matrix has high pressure force, high water bulk ion conductivity, and is easy to handle. By using this matrix, it is possible to manufacture large-capacity fuel cells with excellent long-term stability.

[Brief explanation of the drawing]

Figures 1 and 2 show JblIK versus phosphoric acid amount in an example of the electrolyte matrix for fuel wi1Mk according to the present invention.
Characteristic diagram showing pressure and conductivity, Figure #I3 is a cutaway perspective view of the fuel cell using the electrolyte matrix of the present invention, and Figure 11N4 is a characteristic diagram showing the operating state of the fuel cell shown in No. 35g. I'll come. 1... Fuel electrode catalyst layer 3... Air electrode catalyst layer 6... Electrolyte holding matrix 6... Bipolar separator agent Patent attorney Noriyuki Chika (1 person) Figure 1 11 ) Shout (ru) Figure 8 Figure 4

Claims (1)

[Claims] Carbon heptide consisting of the chemical formula (OF) n, phosphoric acid with high vorticity, and fluorine-based poly as a fixing agent! - An electrolyte matrix for a fuel cell, comprising a mixture comprising: