JP3535942B2 - Proton conductor and electrochemical device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proton conductor having a proton as a conductive ion species, and an electrochemical device such as a fuel cell using the proton conductor.

[0002]

2. Description of the Related Art A substance in which ions move in a solid has been vigorously studied as a material constituting an electrochemical device such as a battery, and currently Li ⁺ , Ag ⁺ , Cu ⁺ , H ⁺ ,
Ionic conductors of various conducting ion species such as F ⁻ have been found. Among them, those using proton (H ⁺ ) as a conductive ion species are expected to be applied to various electrochemical devices such as a fuel cell and an electrochromic display device as shown below. In a fuel cell using hydrogen as a fuel, the reaction of the following formula (1) occurs. The protons generated by this reaction move in the electrolyte and are consumed by the reaction of the formula (2) at the air electrode. That is, by using the proton conductor as the electrolyte, a fuel cell using hydrogen as a fuel can be constructed.

[0003]

[Chemical 1]

Currently, polymer solid oxide fuel cells using an ion exchange membrane as a proton conductor are being actively developed, and they are expected to be applied to stationary power sources, power sources for electric vehicles and the like. There is. In transition metal oxides such as tungsten oxide and molybdenum oxide, color change occurs due to protons entering and leaving the ion sites in the crystal lattice.
For example, tungsten oxide has a light yellow color, but has the formula (3)
By the electrochemical reaction represented by, protons are inserted into the crystal lattice, and a blue color is exhibited. Since this reaction occurs reversibly, it becomes a material for a display element (electrochromic display element) or a light control glass, and in that case, it is necessary to use a proton conductive material as an electrolyte.

[0005]

[Chemical 2]

As described above, various electrochemical devices can be constructed by using the proton conductor as the electrolyte. The proton conductor used for constructing such an electrochemical device is required to exhibit high proton conductivity near room temperature. Examples of such a proton conductor include an inorganic substance such as uranyl phosphate hydrate or molybdophosphoric acid hydrate, or a polymer ion exchange membrane having a side chain containing perfluorosulfonic acid in a vinyl fluoride polymer. Organics are known.

[0007]

The above-mentioned inorganic proton conductor has a problem that the proton in the crystal water contributes to conduction, so that the crystal water is desorbed at a high temperature and the proton conductivity is lowered. . Examples of the electrochemical device obtained by applying the proton conductor include the following fuel cells and electrochromic display devices. BACKGROUND ART Fuel cells are promising applications as a power source for generating a relatively large current for stationary use, electric vehicle use, and the like. For such applications, it is necessary to construct a large area solid electrolyte layer. Further, one of the advantages of the electrochromic display element is the wide viewing angle. Since the electrochromic display element does not use a polarizing plate like a liquid crystal display plate, it can be recognized from a wide angle. Due to this characteristic, the electrochromic device is more effective in displaying a large area than other display devices such as a liquid crystal display device. The large area of the electrolyte layer is an indispensable technology for use in such applications.

As a method for forming an inorganic substance in a thin film form, a vapor deposition method, a casting method and the like can be mentioned. However, in the thin film forming method by the vapor deposition method, the cost is high and it is difficult to obtain a large area thin film. The casting method is a method in which a sol containing a proton conductor is cast on a substrate and gelated to obtain a large-area proton-conducting thin film, but the solvent is evaporated in the thin film obtained by such a method. There are pores formed at that time. As a result, when the proton conductor is applied to a fuel cell, for example, since the active material of the fuel cell is a gas of hydrogen and oxygen, these gases pass through the pores of the proton conductor gel, resulting in power generation. There is a problem of reduced efficiency.

As one method for solving such problems and producing an electrolyte layer having a large area, a method has been proposed in which a plastic resin is added to solid electrolyte powder to form a composite. However, when the above-described compound that causes proton conduction due to water of crystallization is combined with a plastic resin, the hopping motion of protons between water of crystallization is hindered by the plastic resin, so that the proton conductivity is lowered. Alternatively, desorption of water of crystallization at a high temperature has a problem that the proton conductivity is lowered. The ion exchange membrane has an advantage that a large-area membrane excellent in workability can be obtained relatively easily.
However, at present, it is expensive, and there has been a demand for the development of a lower cost proton conductor. Further, the ion exchange resin exhibits high ionic conductivity only in a state where the water content is high (several tens%), and there is a problem that the proton conductivity decreases when dried. An object of the present invention is to solve the above problems and to provide a proton conductor having excellent proton conductivity and having no decrease in proton conductivity even in a dry atmosphere.

[0010]

The proton conductor of the present invention is a binder composed of a compound containing silicon oxide and Bronsted acid as a main component, and a polymer having a sulfone group as a side chain.
Composed of wood . The compound mainly composed of silicon oxide and Bronsted acid is preferably one synthesized by a sol-gel method . As the Bronsted acid, phosphoric acid or its derivative is preferably used. A compound mainly composed of silicon oxide and Bronsted acid is a compound mainly composed of silicon oxide and phosphoric acid, and when this compound is synthesized from a sol containing phosphoric acid and silicon alkoxide, silicon of phosphoric acid contained in the sol. The mixing ratio with respect to the alkoxide is preferably 0.5 or less. Moreover, as the Bronsted acid, it is preferable to use perchloric acid or a derivative thereof . The electrochemical device of the present invention is constituted by using any one of the above proton conductors. The present invention also relates to (A) the sol-gel method.
Is a compound mainly composed of silicon oxide and Bronsted acid.
Obtaining a precursor of the product, (B) heating the precursor
A compound mainly composed of silicon oxide and Bronsted acid.
(C) the silicon oxide and brain stain
Compounds containing sulfonic acid as a side chain
Mixing the polymer with a solution of the polymer in a solvent,
(D) removing the solvent from the resulting mixture to
Of a proton conductor, including the step of obtaining a proton conductor
Regarding the method.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION When a Bronsted acid is added to silicon oxide, the Bronsted acid acts as a proton donor, and the surface of silicon oxide has --OH as an end group.
The structure is such that groups are bound at a high concentration. Since the protons of this —OH group perform hopping motion, they show high proton conductivity. Examples of known proton conductors using silicon oxide include silica gel having sulfuric acid supported on the surface thereof. In the proton conductor obtained by the present invention, the position of the infrared absorption spectrum by the —OH group changes depending on the concentration of Bronsted acid.
From this, the proton conductor according to the present invention is not only one in which an acid is supported on the surface, but one in which silicon oxide and a Bronsted acid form a compound.

Further, when a substance which causes proton conduction due to water of crystallization is used, the water of crystallization is lost in a dry atmosphere, so that the proton conductivity is lowered. On the other hand, in the proton conductor according to the present invention, proton conduction mainly occurs at the —OH group bonded to the silicon oxide surface. Since the —OH group chemically bonded in this way is hard to be desorbed even in a dry atmosphere, the proton conductivity is hardly reduced. However, since the proton conductor obtained from such silicon oxide and Bronsted acid is a hard and brittle solid, and the powder particles when pulverized have poor moldability, they are applied to practical devices. In order to do so, it is necessary to improve the moldability and workability of the proton conductor by combining it with a binder. Here, as the substance used as the binder, it is necessary to use a substance that does not interfere with the proton conductivity. By using a polymer having a sulfone group as a side chain as a binder, the proton of the —OH group bonded to the surface of silicon oxide becomes a —SO of the sulfone group.
₃ ^- can move through, while high moldability maintaining high proton conductivity, it is possible to impart processability. As the polymer having a sulfone group in its side chain used here, for example, a sulfonated polyisoprene represented by the formula (4) is used.

[0013]

[Chemical 3]

Most of the --OH groups bonded to silicon oxide are present on the surface of silicon oxide. The compound mainly composed of silicon oxide and Bronsted acid, which is synthesized by the sol-gel method, has a high surface area and can have a high density of —OH groups. As a result, since the proton conductivity will be excellent, as a method for synthesizing the compound mainly containing silicon oxide and Bronsted acid,
The sol-gel method is preferably used. Further, the compound containing silicon oxide and Bronsted acid as a main component obtained by the sol-gel method has a solution in the micropores, and the Bronsted acid is present in this solution.
For this reason, the composition of the solution changes due to changes in temperature and water vapor pressure in the atmosphere, and the proton conductivity changes, and the characteristics tend to become unstable. By heating at a temperature of 100 ° C. or higher, water present in the micropores is removed, and a structure in which the Bronsted acid is bonded to the amorphous skeleton is formed, and as a result, the characteristics are stabilized. For example, when phosphoric acid is used as the Bronsted acid and a compound mainly containing silicon oxide and phosphoric acid is heat-treated at a temperature lower than 100 ° C., its infrared absorption spectrum shows PO ₄ ^3-
It is considered that the absorption peak attributed to (1) appears, and the aqueous phosphoric acid solution is present in the micropores of the compound. The other hand, if it was heated at a higher heat treatment temperature, PO ₄ intensity of the absorption peak attributed to ³ drops, absorption peak appears to be attributable to the structure of accompanying Si-O-P to it.
This suggests that the phosphoric acid used was bound to the amorphous skeleton. As a result, the structure and characteristics of the compound are stabilized. If the heating temperature exceeds 200 ° C., the compound mainly composed of silicon oxide and Bronsted acid is decomposed by the dehydration reaction and crystallized, so that the proton conductivity is lowered. From the above, in order to stabilize the characteristics of the proton conductor without lowering the proton conductivity, a precursor of a compound mainly composed of silicon oxide and Bronsted acid, which was synthesized by the sol-gel method.
And it is desirable to heat at a temperature of 100 ° C. or higher 200 ° C..

Phosphoric acid or its derivative is a trivalent Bronsted acid, and when a proton conductor is synthesized using this acid, the proton concentration becomes high and the proton conductor showing high ionic conductivity. Is obtained. Therefore, phosphoric acid or its derivative is particularly preferably used as the Bronsted acid. In a compound mainly composed of silicon oxide and plainsted acid, the higher the content of Bronsted acid, the higher the -OH concentration in the obtained compound, and high proton conductivity. However, when phosphoric acid is used as the Bronsted acid, if the content of phosphoric acid is too high, the resulting compound exhibits deliquescent and swells in a humid atmosphere, resulting in its processability and moldability. Is reduced. Moreover,
Since the electric characteristics of the proton conductor change, the characteristics of the electrochemical device using the same deteriorate. Therefore, when synthesizing a compound mainly composed of silicon oxide and Bronsted acid from a sol containing phosphoric acid and silicon alkoxide,
It is preferable that the mixing ratio of phosphoric acid contained in the sol to the silicon alkoxide is 0.5 or less so that the resulting compound does not exhibit deliquescent property. Further, since perchloric acid has a strong action as a proton donor, when this Bronsted acid is used as a dopant for silicon oxide, the synthesized proton conductor has high proton conductivity. From this, perchloric acid is particularly preferably used as the Bronsted acid. Further, the proton conductor thus obtained can be formed into a thin film having a large area relatively easily, and is therefore effective as an electrolyte for an electrochemical device.

[0016]

EXAMPLES Examples of the present invention will be described in detail below. Example 1 In this example, silica gel doped with phosphoric acid as a compound mainly containing silicon oxide and Bronsted acid, sulfonated polyisoprene as a polymer having a sulfone group as a side chain were used, and a proton was used. An example of producing a conductor will be described. First, silica gel doped with phosphoric acid was synthesized by the following method.
Tetraethoxysilane (hereinafter referred to as TEOS) was used as a starting material for synthesizing silica gel, and diluted with ethanol. At this time, the mixing ratio of TEOS and ethanol was set to a molar ratio of 1: 4. Add TE to this solution.
Pure water with a molar ratio of 8 to OS, a 3.6 wt% hydrochloric acid aqueous solution with a molar ratio of HCl to TEOS of 0.01, and tetraethylammonium tetrachloride with a molar ratio of 0.01 to TEOS. Fluoroborate was added and stirred for 5 minutes. Then, 85 wt% phosphoric acid aqueous solution was added to TEOS: H ₃ PO ₄
= 1: 0.5, and the mixture was stirred in a closed container for 3 hours. Next, let stand for 5 hours to gel, and then 150 ℃
Heated for 2 hours. Thus, silica gel doped with phosphoric acid was obtained.

As the sulfonated polyisoprene,
Sulfonation rate (in all monomer units in the polymer,
The molar fraction of the sulfonated monomer units) is 5,1
The thing of 0,30,50% was used. For comparison, non-sulfonated polyisoprene was also used. For these sulfonated polyisoprenes, those having a sulfonation rate of 0% have dioxane and sulfonation rates of 5%.
% And 10% were dissolved in toluene, and those having a sulfonation rate of 30% and 50% were dissolved in water. The phosphoric acid-doped silica gel obtained as described above was ground and stirred in a solution of sulfonated isoprene. However, the weight ratio of silica gel to sulfonated isoprene was set to 20: 1. Finally, the solvent was volatilized with stirring to obtain a proton conductor.

The ionic conductivity of the thus obtained proton conductor was measured by the following method. Proton conductor 20
0 mg was pressure-molded into a pellet having a diameter of 10 mm, and gold foil was pressed against both surfaces of the pellet to obtain an electrode for conductivity measurement. The ionic conductivity of these proton conductors at each temperature was measured by the AC impedance method using the electrochemical cell configured in this manner. The result is shown in FIG. From these results, the higher the sulfonation rate of the isoprene used is, the higher the ionic conductivity is, and by using the sulfonated isoprene as the binder, it is possible to obtain a proton conductor having high ionic conductivity. I found that The proton conductor was placed in a desiccator containing diphosphorus pentoxide as a desiccant to obtain 100
When stored at a temperature of ° C for 7 days and then measured for ionic conductivity, almost no decrease in conductivity was observed.
As described above, according to the present invention, it was found that a proton conductor having high ionic conductivity and having no decrease in ionic conductivity even in a dry atmosphere can be obtained.

Example 2 In this example, a proton conductor was prepared in the same manner as in Example 1 except that the heating temperature of the compound mainly containing silicon oxide and Bronsted acid was changed. First, silica gel doped with phosphoric acid was synthesized by the following method. Similar to Example 1,
To a solution of tetraethoxysilane (TEOS) diluted with ethanol, pure water, 3.6 wt% hydrochloric acid aqueous solution and tetraethylammonium tetrafluoroborate were added and stirred, then 85 wt% phosphoric acid aqueous solution was added and stirred in a closed container. did. Then, after leaving for 5 hours to gel, 6
It was heated at a temperature of 0 ° C to 250 ° C for 2 hours. Thus, silica gel doped with phosphoric acid was obtained. For comparison, heat treatment was not performed, and silica gel doped with phosphoric acid was obtained. As the sulfonated polyisoprene, Example 1 was used.
The one having a sulfonation rate of 50% was used.

The silica gel doped with phosphoric acid obtained as described above was ground and stirred in an aqueous solution of sulfonated isoprene. However, the weight ratio of silica gel to sulfonated isoprene was set to 20: 1.
Finally, the solvent was volatilized with stirring to obtain a proton conductor. The ionic conductivity of the thus obtained proton conductor was measured by the same method as in Example 1. The relationship between the resulting ionic conductivity at room temperature and the heating temperature of phosphoric acid-doped silica gel is shown in FIG. However, in FIG. 2, the heat treatment temperature is shown as 25 ° C., which is room temperature, for the results obtained using silica gel that has not been heat-treated. From these results, the ionic conductivity shows a high value exceeding 10 ⁻⁴ S / cm when the heating temperature is 200 ° C. or lower, and by setting the heating temperature to 200 ° C. or lower, protons having high ionic conductivity are obtained. It has been found that a conductor can be obtained. The proton conductor was placed in a desiccator containing diphosphorus pentoxide as a desiccant, and 1
When the sample was stored at 00 ° C. for 7 days and then the ionic conductivity was measured, almost no decrease in conductivity was observed for the sample that was heat-treated at 100 ° C. or higher. On the other hand, a decrease in ionic conductivity of one to two orders of magnitude was observed for those that were not heat-treated and those that were heat-treated at 60 ° C. As described above, according to the present invention in which the heating temperature of the compound mainly composed of silicon oxide and Bronsted acid synthesized by the sol-gel method is 100 ° C. or more and 200 ° C. or less, high ionic conductivity is exhibited and drying is performed. It was found that a proton conductor having no decrease in ionic conductivity can be obtained even in an atmosphere.

Example 3 This example is the same as Example 1 except that the mixing ratio of TEOS and H ₃ PO _{4 at} the time of obtaining a compound mainly containing silicon oxide and Bronsted acid was changed. A proton conductor was produced by the method described in 1. First, silica gel doped with phosphoric acid was synthesized by the following method. As in Example 1, tetraethoxysilane (TEOS)
Pure water, a 3.6 wt% hydrochloric acid aqueous solution, and tetraethylammonium tetrafluoroborate were added to the solution diluted with ethanol and stirred. Thereafter, a 85 wt% phosphoric acid aqueous solution _{TEOS: H 3 PO 4 = 1} : 0.2~1.0 become so, and the mixture was stirred for 3 hours in a closed vessel. Then
After leaving it for 5 hours for gelation, it was heated at a temperature of 150 ° C. for 2 hours to obtain silica gel doped with phosphoric acid. As the sulfonated polyisoprene, one having a sulfonation rate of 50% among those used in Example 1 was used.

The silica gel doped with phosphoric acid obtained as described above was ground and stirred in an aqueous solution of sulfonated isoprene. However, the weight ratio of silica gel to sulfonated isoprene was set to 20: 1.
Finally, the solvent was volatilized with stirring to obtain a proton conductor. The ionic conductivity of the thus obtained proton conductor was measured by the same method as in Example 1. The resulting ionic conductivity at room temperature and the ratio of TEOS to phosphoric acid (H ₃ P in the sol used in obtaining the silica gel doped with phosphoric acid)
The relationship of O ₄ / TEOS) is shown in FIG. From these results, it was found that the higher the phosphoric acid concentration in the sol, the more proton conductive material having high proton conductivity can be obtained. Next, these proton conductors were heated at 80 ° C and relative humidity of 8
The sample was stored in a 0% constant temperature and humidity chamber, and its change with time was observed. As a result, regarding H ₃ PO ₄ /TEOS≧0.75, the proton conductor swelled and the mechanical strength of the proton conductor was extremely lowered. On the other hand, H ₃ PO ₄ / TE
For OS ≦ 0.5, no change in appearance was observed, and when the ionic conductivity after storage was measured, no significant change was observed in proton conductivity.
As described above, the ratio of TEOS to phosphoric acid in the sol used for obtaining the silica gel doped with phosphoric acid is H ₃ PO ₄ / TEOS ≦
According to the present invention in which the ratio is 0.5, it was found that a proton conductor exhibiting high ionic conductivity and stable to moisture in the atmosphere can be obtained.

Example 4 In this example, an example in which a proton conductor is synthesized by using perchloric acid instead of the phosphoric acid used in Example 1 as the Bronsted acid will be described. As in Example 1, pure water, hydrochloric acid, and perchloric acid were added to TEOS diluted with ethanol. At this time, the mixing ratio of TEOS, ethanol, pure water, and hydrochloric acid was set to a molar ratio of 1: 8: 4: 0.05. To this solution, perchloric acid was added so as to be 20% with respect to the weight of silica gel doped with perchloric acid which is considered to be produced,
Stir at room temperature for 3 hours, then gel for 5 hours and finally 150
It was dried under reduced pressure at ℃ for 2 hours. Thus, silica gel doped with perchloric acid was obtained. As the sulfonated polyisoprene, the one used in Example 1 was used. Sulfonated isoprene was added to the silica gel doped with perchloric acid obtained above in the same manner as in Example 1 to obtain a proton conductor.

As a result of measuring the ionic conductivity of the thus obtained proton conductor by the same method as in Example 1, the ionic conductivity shows a higher value as the sulfonation rate of polyisoprene becomes higher, When polyisoprene having a sulfonation ratio of 50% was used, the ionic conductivity at room temperature showed a value of 3.2 × 10 ⁻⁴ S / cm. In addition, Example 1
Similarly to the above, no decrease in conductivity was observed when stored in a dry atmosphere. As described above, according to the present invention, it was found that a proton conductor having high ionic conductivity and having no decrease in ionic conductivity even in a dry atmosphere can be obtained.

Example 5 In this example, instead of the phosphoric acid used in Example 1 as the Bronsted acid, phosphotungstic acid (H ₃ PW), which is one of the phosphoric acid derivatives, was used.
An example in which a proton conductor is synthesized using ₁₂ O ₄₀ .29H ₂ O) will be described. Silica gel doped with phosphotungstic acid was synthesized by the same method as in Example 4 except that phosphotungstic acid was used instead of perchloric acid. However, when phosphotungstic acid is added to a mixed solution of TEOS, ethanol, pure water, and hydrochloric acid, the weight of phosphotungstic acid becomes 45% with respect to the weight of silica gel doped with phosphomolybdic acid which is considered to be generated. So added. As the sulfonated polyisoprene, the one used in Example 1 was used. Sulfonated isoprene was added to the silica gel doped with phosphotungstic acid obtained above in the same manner as in Example 1 to obtain a proton conductor.

The ionic conductivity of the thus obtained proton conductor was measured by the same method as in Example 1. As a result, the ionic conductivity showed a higher value as the sulfonation ratio of polyisoprene increased. When polyisoprene having a sulfonation rate of 50% was used, the ionic conductivity at room temperature showed a value of 1.1 × 10 ⁻⁴ S / cm. In addition, Example 1
Similarly to the above, no decrease in conductivity was observed when stored in a dry atmosphere. As described above, according to the present invention, it was found that a proton conductor having high ionic conductivity and having no decrease in ionic conductivity even in a dry atmosphere can be obtained.

Example 6 In this example, instead of the phosphotungstic acid used in Example 5 as the Bronsted acid, phosphomolybdic acid (H ₃ PMo ₁₂ O _{4 0.} 29H ₂ O) was used, and a proton conductor was synthesized in the same manner as in Example 5, and its ionic conductivity was examined. As a result, the ionic conductivity shows a higher value as the sulfonation rate of polyisoprene becomes higher, and the ionic conductivity at room temperature when polyisoprene having a sulfonation rate of 50% is used is 8.6 × 10. ^-5 S / c
The value of m is shown. Also, when the sample was stored in a dry atmosphere as in Example 1, no decrease in conductivity was observed. As described above, according to the present invention, high ionic conductivity is exhibited,
It was found that a proton conductor having no decrease in ionic conductivity can be obtained even in a dry atmosphere.

Example 7 In this example, a proton was prepared in the same manner as in Example 1 except that silicon isopropoxide was used as the raw material for producing silicon oxide instead of TEOS used in Example 1. A conductor was synthesized. The ionic conductivity of the thus obtained proton conductor was measured by the same method as in Example 1. As a result, the ionic conductivity showed a higher value as the sulfonation rate of polyisoprene was higher, and the sulfonation rate was higher. Ionic conductivity at room temperature is 1.4 × 10 ^-4 S / cm when 50% polyisoprene is used.
The value of was shown. Also, when the sample was stored in a dry atmosphere as in Example 1, no decrease in conductivity was observed. As described above, according to the present invention, it was found that a proton conductor having high ionic conductivity and having no decrease in ionic conductivity even in a dry atmosphere can be obtained.

Example 8 In this example, a proton conductor was prepared in the same manner as in Example 1 except that the amount of sulfonated polyisoprene, which is a polymer having a sulfone group in its side chain, was changed. Obtained. The phosphoric acid-doped silica gel was synthesized in the same manner as in Example 1. A solution of sulfonated polyisoprene was added to this silica gel so that the weight ratio of sulfonated isoprene and silica gel was 1:50, and the solvent was volatilized while stirring to obtain a proton conductor. The ionic conductivity of the thus obtained proton conductor was measured by the same method as in Example 1. As a result, the ionic conductivity showed a higher value as the sulfonation rate of polyisoprene was higher, and the sulfonation rate was higher. When using 50% of polyisoprene, the ionic conductivity at room temperature is 1.
The value was 8 × 10 ⁻⁴ S / cm. Also, when the sample was stored in a dry atmosphere as in Example 1, no decrease in conductivity was observed. As described above, according to the present invention, it was found that a proton conductor having high ionic conductivity and having no decrease in ionic conductivity even in a dry atmosphere can be obtained.

Example 9 In this example, as the polymer having a sulfone group in its side chain, the sulfonated polyisoprene used in Example 1 was replaced with a sulfone having a sulfonation rate of 0 to 50%. A proton conductor was obtained in the same manner as in Example 1 except that the modified styrene-ethylene-butylene-styrene block copolymer was used. The ionic conductivity of the thus-obtained proton conductor was measured by the same method as in Example 1, and as a result, the ionic conductivity was that the styrene-ethylene-butylene-styrene block copolymer had a high sulfonation ratio. The ionic conductivity at room temperature was 2.1 × 10 ⁻⁴ S / cm when a sulfonation rate of 50% was used. Also, when the sample was stored in a dry atmosphere as in Example 1, no decrease in conductivity was observed. According to the present invention as described above,
It was found that a proton conductor having high ionic conductivity and having no decrease in ionic conductivity even in a dry atmosphere can be obtained.

Example 10 In this example, as the polymer having a sulfone group in the side chain, the sulfonated polyisoprene used in Example 1 was replaced with a sulfone having a sulfonation rate of 0 to 50%. A proton conductor was obtained in the same manner as in Example 1 except that the modified isoprene-styrene random copolymer was used. The ionic conductivity of the thus-obtained proton conductor was measured by the same method as in Example 1. As a result, the ionic conductivity increased as the sulfonation rate of the isoprene-styrene random copolymer increased. The ionic conductivity at room temperature when the sulfonation rate was 50% was 1.7 × 10 ⁻⁴ S / cm. Also, when the sample was stored in a dry atmosphere as in Example 1, no decrease in conductivity was observed. As described above, according to the present invention, it was found that a proton conductor having high ionic conductivity and having no decrease in ionic conductivity even in a dry atmosphere can be obtained.

Example 11 In this example, an example in which an electrochromic display device is constructed by using the proton conductor obtained in Example 1 will be described. The display electrode 4 of the electrochromic display element has tungsten oxide (W
O ₃ ) thin film was used. As shown in FIG. 4, a tungsten oxide thin film 3 was formed by electron beam evaporation on a glass substrate 1 on the surface of which an ITO layer 2 was formed as a transparent electrode by sputtering evaporation. Further, the counter electrode 8 has a proton-doped tungsten oxide (H _x W) obtained by the following method.
O ₃ ) thin film was used. First, as with the display pole above, IT
A tungsten oxide thin film 7 was formed on the glass substrate 5 on which the O electrode 6 was formed. This glass substrate is treated with chloroplatinic acid (H ₂
The tungsten oxide was converted into tungsten bronze (H _x WO ₃ ) by immersing it in an aqueous solution of PtCl ₆ ) and drying it in a hydrogen stream.

The electrolyte layer 9 of the electrochromic display element was formed by the following method. First, the silica gel doped with phosphorus acid obtained in Example 1 was added an aqueous solution of sulfonated ratio 50% sulfonated polyisoprene. Further, since this electrolyte layer also serves as a reflection plate of the electrochromic display element, alumina powder was added to the silica gel in a weight ratio of 5% in order to color it white. This mixture was kneaded until it became a slurry, and 50 μm was applied to the surface of the display electrode 4 obtained above by a doctor blade method.
It was applied to a thickness of m to form an electrolyte layer. The counter electrode 8 obtained above was covered so as to cover the electrolyte layer 9, and the solvent was volatilized under reduced pressure. The sectional view is shown in FIG. Further, the end face was adhesively sealed with an ultraviolet curable resin 10 to obtain an electrochromic display element. 11 and 12 are lead terminals.

A voltage of -1 V is applied to the display electrode of the electrochromic display device thus obtained for 2 seconds with respect to the counter electrode to color the display electrode, and then a voltage of +1 V is applied for 2 seconds to erase the color. A working cycle test was performed. as a result,
Even after the lapse of 10,000 cycles, color development / decolorization could be performed without deterioration in performance. As described above, it was found that an electrochromic display device can be obtained by using the proton conductor according to the present invention.

Example 12 In this example, the proton conductor obtained in Example 1 is used,
An example of constructing an oxyhydrogen fuel cell having the structure shown in FIG. 6 will be described. First, the phosphoric acid-doped silica gel obtained in Example 1 was mixed with an aqueous solution of sulfonated polyisoprene having a sulfonation rate of 50% and kneaded to form a slurry, and polytetrafluoride was added. It was applied on an ethylene plate by a doctor blade method to a thickness of 50 μm. Further, after toluene was volatilized under reduced pressure, it was peeled off from the polytetrafluoroethylene plate to obtain an electrolyte layer for a fuel cell. As the gas diffusion electrode, a gas diffusion electrode manufactured by E-Tech (platinum supported amount: 0.35 mg / cm ² ) was used. Spraying an aqueous solution of the gas diffusion electrode above the sulfonation rate of 50% with the same silica gel is dispersed as the formation of the electrolyte layer sulfonated poly isoprene <br/> Ren and the electrode was dried under reduced pressure .
The electrodes 20 and 21 sandwich the electrolyte layer 22 and 1
A fuel cell element was constructed by hot pressing at a temperature of 50 ° C.

The fuel cell device thus obtained, as shown in FIG. 6, has a stainless steel block 29 having an H ₂ gas introduction hole 23, a fuel chamber 24 and an H ₂ gas discharge hole 25, and an O ₂ gas.
It is sandwiched between a gas introduction hole 26, an oxygen chamber 27, and a stainless steel block 30 having an O ₂ gas discharge hole 28, and the whole is made up of electrically insulating fiber-reinforced plastic fastening rods 31, 3
It fastened with 2, and it was set as the fuel cell for a test. In FIG. 6, 33
Is a drain of H ₂ O, 34 is a negative electrode terminal, and 35 is a positive electrode terminal. In the cell test, hydrogen pressurized to 3 atm was passed through the fuel electrode, and air pressurized to 5 atm was passed through the air electrode.
The relationship between the output current and the battery voltage was investigated. The voltage-current curve obtained as a result is shown in FIG. Even when a current of 400 mA / cm ² was taken out, the cell voltage was maintained at 0.7 V or higher, and it was found that the fuel cell obtained in this example exhibited excellent high output characteristics. As described above, it was found that a fuel cell having excellent characteristics can be obtained by using the proton conductor according to the present invention.

In the above examples, only the examples using sulfonated polyisoprene, sulfonated styrene-ethylene-butylene-styrene block copolymer, etc. as the polymer having a sulfone group in the side chain are used. Although described, it is needless to say that the same effect can be obtained when a sulfonated product of other polymer, which is not described in the examples such as butadiene-styrene copolymer, is used. The polymer having a group in the side chain is not limited to those listed in these examples.
Further, in the examples, only those using phosphoric acid, perchloric acid or the like as the Bronsted acid, but other boric acid, silicic acid or the same effect when using a plurality of these Bronsted acid Needless to say, the present invention is not limited only to the Bronsted acids listed in these examples as Bronsted acids. Further, in the examples, the electrochromic display element and the fuel cell were described as the electrochemical element using the proton conductor.
Needless to say, an electrochemical element such as a pH sensor or an electric double layer capacitor, which has not been described in the examples, can be constructed, and the present invention is limited to the electrochemical elements described in these examples. Not a thing.

[0038]

As described above, according to the present invention, it is possible to obtain a proton conductor which is excellent in proton conductivity and does not deteriorate in a dry atmosphere. By using the proton conductor of the present invention, an electrochemical device having excellent characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing the ionic conductivity of proton conductors in Examples and Comparative Examples of the present invention.

FIG. 2 is a diagram showing the ionic conductivity of proton conductors in Examples and Comparative Examples of the present invention.

FIG. 3 is a diagram showing the ionic conductivity of proton conductors in Examples and Comparative Examples of the present invention.

FIG. 4 is a cross-sectional view showing an electrode structure of an electrochromic display element in an example of the present invention.

FIG. 5 is a vertical sectional view of an electrochromic display element according to an example of the present invention.

FIG. 6 is a vertical cross-sectional view of an oxyhydrogen fuel cell element according to an example of the present invention.

FIG. 7 is a current-voltage curve showing the characteristics of the oxyhydrogen fuel cell in the example of the present invention.

[Explanation of symbols]

1, 5 Glass substrate 2, 6 Transparent electrode layer (ITO layer) 3, 7 Tungsten oxide thin film 4 Display electrode 8 Counter electrode 9 Electrolyte layer 10 Sealing resin 11, 12 Lead terminal 20 Fuel electrode 21 Oxygen electrode 22 Electrolyte layer 23 H ₂ Gas inlet hole 24 Fuel chamber 25 H ₂ gas outlet hole 26 O ₂ gas inlet hole 27 Oxygen chamber 28 O ₂ gas outlet holes 31, 32 Tightening rod 33 H ₂ O drain 34 Negative electrode terminal 35 Positive electrode terminal

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI H01M 8/10 H01M 8/10 (72) Inventor Tsutomu Minami 2-7-1 Onodai, Osaka Sayama City, Osaka Prefecture (72) Inventor Masahiro Tatsusuna 445-31, Josoku, Sakai-shi, Osaka (72) Inventor Yasumasa Takeuchi 2-11-24 Tsukiji, Chuo-ku, Tokyo Tokyo Incorporated (72) Inventor, Keiichi, Tokyo 2-chome Tsukiji, Chuo-ku, Tokyo 11-24 No. 24 within Japan Synthetic Rubber Co., Ltd. (56) Reference JP-A-1-192742 (JP, A) JP-A-61-181078 (JP, A) JP-A-62-200258 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) H01B 1/06 G02F 1/15 H01M 8 / 02,8 / 10

Claims (8)

(57) [Claims] 1. A compound mainly containing silicon oxide and Bronsted acid, and a polymer having a sulfone group in a side chain.
A proton conductor characterized by comprising a binder made of. 2. A polymer having the sulfone group as a side chain
The proton conductor according to claim 1 , wherein the binder made of sulfonated polyisoprene . 3. The proton conductor according to claim 1, wherein the compound mainly containing silicon oxide and Bronsted acid is synthesized by a sol-gel method. 4. The proton conductor according to claim 1, wherein the Bronsted acid is phosphoric acid or a derivative thereof. 5. The compound mainly composed of silicon oxide and Bronsted acid is synthesized from a sol containing phosphoric acid and silicon alkoxide, and the mixing ratio of phosphoric acid contained in the sol to silicon alkoxide is mol. The proton conductor according to claim 1, which has a ratio of 0.5 or less. 6. The proton conductor according to claim 1, wherein the Bronsted acid is perchloric acid or a derivative thereof. 7. An electrochemical device using the proton conductor according to claim 1. 8. (A) Silicon oxide by sol-gel method
And a precursor of a compound mainly composed of Bronsted acid
Process, (B) The precursor is heated to give silicon oxide and branes.
A step of obtaining a compound mainly composed of Sted acid, (C) Mainly composed of silicon oxide and Bronsted acid
A compound having a sulfone group as a side chain
Mixing with a solution dissolved in (D) removing the solvent from the resulting mixture to
Of a proton conductor, including the step of obtaining a proton conductor
Method.