JP2002216537A - Proton conductive solid electrolyte and proton conductive solid electrolyte sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant solid electrolyte material having high proton conductivity of 10-3-10-1 S/cm over the wide range of temperature from room temperature to 100 deg.C or higher. SOLUTION: The proton conductive solid electrolyte contains a solid acid which carries highly proton-dissociable sulfuric acid on a metal hydroxide and/or a metal oxide. The sulfuric acid-carrying metal oxide holds heat-resistivity by heat treatment through synthesizing and a combination of sulfuric acid and a metal oxide making a superstrong acid is preferable. Preferably, the mole ratio S/M of the sulfur in the sulfuric acid and the metal element (M) is within the range of 0.01 to 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolyte material, and more particularly to a proton conductive solid electrolyte and a proton conductive material which can be used for energy conversion devices such as fuel cells and electric double layer capacitors, electrochromic devices, sensors and the like. The present invention relates to a conductive solid electrolyte sheet.

[0002]

2. Description of the Related Art Compared with a liquid electrolyte, a solid electrolyte plays an important role in forming an electrochemical device, such as simplicity of a process and reduction in size and weight of the device. In particular, solid electrolytes that exhibit proton conduction are being developed as key materials in the production of solid polymer electrolyte fuel cells, electrochromic display elements, sensors, and the like that maintain high energy density at low temperatures.

At present, as proton conductive solid electrolytes, organic polymer ion exchange membranes such as sulfonated polyfluoroolefins (for example, Nafion (trade name, manufactured by DuPont)) and polybenzimidazole doped with alkylphosphoric acid (ex. JP-A-9-110982), and further, a sulfonated polycarbonate (JP-A-2000-23).
No. 5812).

As the inorganic proton-conductive solid electrolyte, composite silica gel doped with perchloric acid and phosphomolybdic acid crystal (Masahir), which is a heteropoly acid, are used.
oTatsusumisago et. al. Am. C
eram. Soc. , Vol. 72, NO. 3,484
486 (1989)), a silica glass of a phosphoric acid composite type (Masayuki Nogami et.
Electrochem. Soc. , Vol 144,
NO. No. 6,2175-2178 (1997)), and studies are being made to apply these to the production of all-solid-state light control elements and all-solid-state capacitors.

[0005]

At present, an organic polymer proton conductive solid electrolyte such as Nafion is used as an electrochemical element. However, when the temperature exceeds 100 ° C., the heat resistance of the material becomes a problem, and the sensor and the When applied to an energy conversion element, it has been pointed out that the performance is degraded when used at a high temperature. For example, when the application to a fuel cell is considered, it means that the use in a range of 100 to 150 ° C. with high power generation efficiency is restricted.

Currently known proton conductive solid electrolytes exhibiting a proton conductivity of the order of 10 ⁻⁵ to 10 ⁻² S / cm in a specific temperature range have been developed. A solid electrolyte that stably exhibits a high proton conductivity of 10 ⁻² S / cm or more in a wide temperature range exceeding the above range has not been developed. In general, inorganic materials have better heat resistance than organic materials, but phosphomolybdic acid is likely to become amorphous at around 100 ° C.
The temperature region showing a high conductivity of 10 ⁻² to 10 ⁻¹ S / cm stays around room temperature. For the phosphoric acid composite type silica glass and the organic proton conductive polymer solid electrolyte, the temperature range from room temperature to around 80 ° C. is 10 ⁻³ to 10.
^Materials exhibiting high conductivity on the order of ^-2 S / cm have been developed.

[0007] Also, there are few research examples on the development of a solid super-proton conductor exhibiting the order of 10 ^-1 S / cm, but if it can be realized, the response speed of the display element can be improved,
It is expected that the process for electrochemical device fabrication, such as fuel cell fabrication without the need for reinforcing materials, will progress.

[0008] The present invention has proton-conducting solid electrolyte as described above has been made to solve the problems faced situation, and its object is 10 ^-3 to a wide temperature range exceeding 100 ° C. from room An object of the present invention is to provide a heat-resistant solid electrolyte material exhibiting a high proton conductivity of 10 ⁻¹ S / cm.

[0009]

In order to provide a material having high proton conductivity, it is necessary to increase the mobility of protons in a solid and to allow molecular water to coexist. In order to increase the mobility, it is necessary that a large amount of protons having a strong hydrogen bond exist in the electrolyte. Therefore, a solid acid in which sulfuric acid having a high degree of proton dissociation is supported on a metal oxide is high. Develop proton conductivity. As a result of conducting research based on this concept, the present inventors have found that a sulfuric acid-supported metal oxide (expressed as SO ₄ / MxOy) exhibits a proton conductivity of a level of 10 ⁻⁵ to 10 ⁻¹ S / cm. By adding heat treatment in the composition control and synthesis process of the sulfuric acid-supported metal oxide,
The present inventors have found that a high proton conductive solid electrolyte having a heat resistance of 10 ⁻³ to 10 ⁻¹ S / cm can be produced, and have completed the present invention.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

According to the present invention, the degree of proton dissociation is large, and the
^Disclosed is a heat-resistant sulfuric acid-supporting metal oxide which maintains a proton conductivity at a level of ^-5 to 10 ^-1 S / cm.

In the sulfuric acid-supporting metal oxide of the present invention, the metal hydroxide and / or metal oxide serving as a carrier becomes a solid acid by supporting sulfuric acid. It is particularly desirable to use zirconium, titanium, iron, tin, silicon, aluminum, molybdenum, and tungsten oxides each having a high acid strength of the oxide SO ₄ / MxOy.

The degree of proton dissociation can be expressed as an acid strength, and the acid strength of a solid acid is expressed as Hammett's acidity function H _{0. In} the case of sulfuric acid, H ₀ is −11.93.
In the present invention, the solid superacidity refers to a material having a property that satisfies a range of H ₀ <-11.93. As a sulfuric acid-supporting metal oxide exhibiting high proton conductivity, a combination of a metal element exhibiting solid superacidity and sulfuric acid is preferred, and a sulfuric acid-supporting metal selected from zirconium, titanium, iron, tin, silicon, and aluminum is preferred. Oxides correspond to this (K. Ar
ata et al. J. Am. Chem. So
c. , VOL 1016439- (1979)).

The sulfuric acid-supporting metal oxide can be synthesized by the reaction of a metal oxide or metal hydroxide with sulfuric acid, but the synthesis method is not limited to this. Further, heat treatment is performed at a temperature of 300 ° C. or more, preferably 500 ° C. or more, in order to advance the reaction with sulfuric acid. Further, by performing the heat treatment, the heat resistance is improved up to the heat treatment temperature, and the operating temperature range of the solid electrolyte is widened.

[0015] In the sulfuric acid-supporting metal oxide according to the present invention, the molar ratio S / of the sulfuric acid (S) and the metal element (M) constituting the metal hydroxide and / or metal oxide serving as a carrier. M is preferably 0.0001 to 1.5,
0.001-1 is more preferable, and the range of 0.01-1 is still more preferable. If it is less than 0.01, the effect of the loading may be reduced. If it exceeds 1, the proton conductivity may not be improved, probably because the acidity is reduced.

The proton conductive solid electrolyte may be a sulfuric acid-supported metal oxide composed of two or more elements. In this case, a mixed metal oxide supporting sulfuric acid or a mixture of sulfuric acid supporting metal oxide may be used.

The proton conductive solid electrolyte sheet of the present invention can be manufactured by supporting sulfuric acid on a metal oxide sheet (ceramic sheet). For example, by subjecting a ceramic sheet prepared by adding CaO, Y ₂ O _3, or the like to zirconium oxide ZrO ₂ to sulfuric acid treatment, a proton conductive solid electrolyte sheet excellent in toughness can be manufactured.

[0018]

EXAMPLES Examples of the present invention will now be described and specifically described, but the present invention is not limited to these examples.

Example 1 Distilled water was added to 0.5 g of concentrated sulfuric acid (96%) to prepare an aqueous sulfuric acid solution having a total weight of 100 g. Zirconium oxide ZrO ₂ was added to this aqueous sulfuric acid solution for 20 minutes.
g was added and stirred for 3 hours to prepare a slurry. The slurry was heated from room temperature to 100 ° C. at a rate of 5 ° C./min and kept at 100 ° C. for 3 hours to remove water. Thereafter, the powder was further heated to 200 ° C. at a rate of 1 ° C./min and maintained at 200 ° C. for 3 hours to obtain a white powder. Most of the weight loss at this stage was due to water volatilization. The white powder is further heated to 500 ° C. at a rate of 1 ° C./min and maintained at 500 ° C. for 3 hours, so that sulfur (S) in the sulfuric acid content and the hydroxide and / or oxide Metal Elements (M) Constituting
A white powder of sulfuric acid-supported zirconia SO ₄ / ZrO ₂ having a molar ratio S / M of 0.03 was obtained.

Example 2 The same operation as in Example 1 was carried out except that 1 g of concentrated sulfuric acid (96%) was used to form sulfur (S) of sulfuric acid and hydroxide and / or oxide as a carrier. A white powder of sulfuric acid-supported zirconia SO ₄ / ZrO ₂ having a molar ratio S / M to the metallic element (M) of 0.06 was obtained.

Example 3 The same operation as in Example 1 was carried out except that 4 g of concentrated sulfuric acid (96%) was used to form sulfur (S) of sulfuric acid and a hydroxide and / or oxide as a carrier. A white powder of sulfuric acid-supported zirconia SO ₄ / ZrO ₂ having a molar ratio S / M to the metal element (M) to be obtained of 0.25 was obtained.

Example 4 The same operation as in Example 1 was carried out except that 6 g of concentrated sulfuric acid (96%) was used to form sulfur (S) of sulfuric acid and a hydroxide and / or oxide as a carrier. A white powder of sulfuric acid-supported zirconia SO ₄ / ZrO ₂ having a molar ratio S / M to the metallic element (M) to be obtained of 0.38 was obtained.

Example 5 The same operation as in Example 1 was carried out except that 8 g of concentrated sulfuric acid (96%) was used to form sulfur (S) of sulfuric acid and hydroxide and / or oxide as a carrier. A white powder of sulfuric acid-supported zirconia SO ₄ / ZrO ₂ having a molar ratio S / M to the metal element (M) to be produced of 0.50 was obtained.

Example 6 The same operation as in Example 1 was carried out except that 16 g of concentrated sulfuric acid (96%) was used to constitute sulfuric acid (S) of sulfuric acid and a hydroxide and / or oxide as a carrier. A white powder of sulfuric acid-supported zirconia SO ₄ / ZrO ₂ having a molar ratio S / M to the metal element (M) of 0.93 was obtained.

Example 7 The same operation as in Example 1 was carried out except that 25 g of concentrated sulfuric acid (96%) was used to form sulfur (S) of sulfuric acid and hydroxide and / or oxide as a carrier. A white powder of sulfuric acid-supported zirconia SO ₄ / ZrO ₂ having a molar ratio S / M to the metal element (M) of 1.4 was obtained.

Comparative Example 1 Zirconium oxide ZrO ₂ was prepared in the same manner as in Example 1 in place of sulfuric acid-supported zirconia.

After pulverizing the sulfuric acid-carrying zirconia of Examples 1 to 7, it was molded into a disc-shaped pellet having a diameter of 13 mm and a thickness of 0.5 mm at a pressure of 5 tons. 0.1m thickness on both sides
m of platinum electrodes was pressed against each other to prepare an electrochemical cell for measuring electric conductivity. The cell was allowed to stand at 100% relative humidity for 12 hours, and then subjected to AC impedance method using an impedance analyzer IM6 manufactured by ZAHNER.
The proton conductivity at 3 ° C. and 90 ° C. was determined. The results are shown in Table 1. For zirconium oxide ZrO ₂ obtained in Comparative Example 1, pellets were prepared in the same manner as described above, and the proton conductivity was measured. 4. At 23 ° C.
2 × 10 ⁻⁶ S / cm, 9.2 × 10 ⁻⁶ S / cm at 90 ° C.
cm. 1 × 10 ⁻³ S / c at 23 ° C. in a molar ratio of S / Zr, that is, S / M in the range of 0.25 to 0.5.
m and higher proton conductivity was obtained, and the conductivity was improved by two to three orders of magnitude compared to the raw material zirconia ZrO ₂ shown in Comparative Example 1. When the acidity function was examined using p-nitrofluorobenzene (New Experimental Chemistry Course 16 Maruzen) as an acidity indicator, the S / M molar ratio was 0.06, 0.25,
The one with 0.38 was a super strong acid with HO <-12.44. The supporting ratio of sulfuric acid was determined from the weight loss from the powder at 200 ° C. for 3 hours, and the amount of sulfuric acid charged was 0.5 g to 8 g.
No significant weight loss was observed, but the sulfuric acid charge amount of 16 g and 25 g had a weight loss of 10% or more.

[0028]

[Table 1]

[Embodiment 8] Embodiments 3, 4, and 5, respectively,
The S / M molar ratio prepared in the same manner as in Example 1 was 0.25, and the S / M molar ratio was 0.2.
Temperature dependence of the proton conductivity of sulfuric acid-supported zirconia of 38, 0.50 was measured. The electrochemical cell and the measuring method were the same as in Example 1. The relative humidity is 100% when the measurement environment is 100 ° C. or lower, but the relative humidity cannot be specified in a temperature range exceeding 100 ° C., but the measurement was performed while humidifying. The impedance was measured after each temperature was held for 15 minutes. FIG. 1 is a graph showing the relationship between proton conductivity and temperature of sulfuric acid-supported zirconia synthesized in Examples 3, 4, and 5. As a result, each sample was 0.1 S / c.
A region having a superproton conductivity exceeding m was confirmed in a temperature region around 100 ° C. At a S / M molar ratio of 0.38, 1
A conductivity of 0.19 S / cm at 15 ° C. was obtained. This has a proton conductivity about 10 times that of the currently known organic polymer type proton conductive solid electrolyte such as Nafion. These results are summarized in FIG.

Examples 9 to 15 Titanium oxide (TiO ₂ ), ferric oxide (Fe ₂ O ₃ ), and tin oxide (S
nO ₂ ), silica (SiO ₂ ), aluminum oxide (A
1 ₂ O ₃ ), molybdenum oxide (MoO ₃ ), and sulfuric acid-supporting metal oxides of tungsten oxide (WO ₃ ) were synthesized in the same manner as in Example 1 using each metal oxide as a raw material. S /
The molar ratio of M was 0.38 for all samples. The proton conductivity was determined by an AC impedance method under the environment of 23 ° C. and 100% relative humidity by preparing an electrochemical cell similar to that in Example 1. As a result, the proton conductivity showed a value of 10 ^{−4 to} 10 ⁻² S / cm, the proton conductivity was improved by two to three orders as compared with the oxide of the raw material, and the effect of supporting sulfuric acid was clearly confirmed. . The results are shown in Table 2.

[0031]

[Table 2]

Example 16 A 3 cm square thickness of 200 μm
The partially stabilized zirconia sheet was completely immersed in 96% concentrated sulfuric acid, and vacuum suction was performed with a rotary pump at 60 ° C. for 12 hours to allow sulfuric acid to soak into the sheet. The original sheet was white and opaque, but the one treated with sulfuric acid exhibited some transparency. 5 ° C /
After heating to 100 ° C. at a heating rate of 1 minute and holding at 100 ° C. for 3 hours, heating to 200 ° C. at a heating rate of 1 ° C./minute and holding at 200 ° C. for 3 hours. Further, the sample was heated to 500 ° C. at a rate of 1 ° C./min and maintained at 500 ° C. for 3 hours to produce a zirconia sheet carrying sulfuric acid.
The S / Zr molar ratio was 0.12 by fluorescent X-ray analysis.

A platinum electrode having a thickness of 0.1 mm was pressed against both sides of the above-mentioned zirconia sheet carrying sulfuric acid to prepare an electrochemical cell for measuring electric conductivity. Using this cell, the temperature dependence of the proton conductivity was measured in the same manner as in Example 2. As a result, the proton conductivity showed a level of 10 ⁻³ S / cm in a wide temperature range of 23 ° C. to 140 ° C. FIG. 2 is a graph showing the relationship between the proton conductivity and the temperature of the zirconia sheet carrying sulfuric acid. The zirconia sheet before carrying sulfuric acid, which was measured in the same manner, showed an insulator and had a conductivity of 10 ⁻⁹ S / cm or less. Therefore, a significant improvement in proton conductivity was confirmed by carrying sulfuric acid.

[0034]

According to the present invention, it is possible to provide a proton conductive solid electrolyte having high conductivity in a wide temperature range from room temperature to over 100 ° C. In addition, a solid electrolyte sheet provided with proton conductivity by supporting sulfuric acid on a ceramic sheet can be produced.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the proton conductivity and temperature of sulfuric acid-supported zirconia.

FIG. 2 is a graph showing the relationship between the proton conductivity of a sulfuric acid-supported zirconia sheet and temperature.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 1/08 H01M 8/02 K H01G 9/025 G01N 27/58 Z H01M 8/02 H01G 9/00 301G (72) Inventor Yuichi Ishikawa 17 Kandoji Minamicho, Shimogyo-ku, Kyoto, Kyoto Prefecture Inside the Kansai New Technology Research Institute (72) Inventor Atsushi Kamachi 1-4-1, Chuo, Wako-shi, Saitama Japan Honda R & D Co., Ltd. In-house F term (reference) 2G004 ZA01 2G060 AA08 AF03 AF08 AG05 AG11 GA01 HA02 4G048 AA02 AB02 AC06 AD03 AD06 5G301 CA02 CA12 CA23 CA25 CA28 CD01 CD10 5H026 AA06 EE11 HH05

Claims (5)

[Claims] 1. A proton-conductive solid electrolyte having a sulfuric acid-supported metal oxide as a solid acid. 2. A molar ratio S / of the sulfuric acid (S) in the sulfuric acid-supporting metal oxide and the metal element (M) constituting the metal hydroxide and / or metal oxide as a carrier.
2. The proton conductive solid electrolyte according to claim 1, wherein M is in the range of 0.0001 to 1.5. 3. The sulfuric acid-supporting metal oxide is zirconium,
The proton conductive solid electrolyte according to claim 2, wherein the solid electrolyte contains one or more elements selected from titanium, iron, tin, silicon, aluminum, molybdenum, and tungsten. 4. The proton conductive solid electrolyte according to claim 2, wherein the sulfuric acid-supporting metal oxide exhibits a solid superacidity. 5. A proton conductive solid, characterized by supporting sulfuric acid on a ceramic sheet containing at least one oxide of zirconium, titanium, iron, tin, silicon, aluminum, molybdenum and tungsten. Electrolyte sheet.