complex electrolytes

Abstract

To provide a composite electrolyte having a relatively small content of a deterioration inhibitor and exhibiting a high deterioration inhibiting action.SOLUTION: A composite electrolyte comprises a solid polymer electrolyte and a tungsten oxide dispersed in the solid polymer electrolyte. The tungsten oxide includes one or more selected from the group consisting of WO2 and WOx nH2O (2<x≤3, 0≤n<3, and x and n each include a non-integer). The tungsten oxide has an average primary particle diameter of 10 nm to 2000 nm. The composite electrolyte preferably satisfies 0.0001≤W' / A<0.25, where W' / A is a ratio of the number of moles of tungsten (W') contained in the tungsten oxide to the number of moles of acid groups (A) contained in the solid polymer electrolyte.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a composite electrolyte, and more particularly to a composite electrolyte containing an additive having an effect of suppressing deterioration of a solid polymer electrolyte.

Background Art

[0002] In a soda electrolyzer, a water electrolyzer, a fuel cell, etc., a membrane electrode assembly (MEA) is used at a site where an electrochemical reaction occurs. It is said that the electrolyte is attacked and deteriorated by radicals directly generated by the direct reaction or electrochemical reaction of oxygen and hydrogen, or radicals generated via hydrogen peroxide. For example, in a fuel cell, it is known that an increase in the resistance of the electrolyte membrane, an increase in cross leakage, a shortening of the life due to thinning, etc. occur due to radical attack. Furthermore, there is a risk that catalyst poisoning may occur due to deterioration products generated by radical attack, resulting in a decrease in electrolysis performance and battery performance.

[0003] Therefore, various proposals have been made conventionally to solve this problem. For example, in Patent Document 1, (a) a catalyst ink obtained by adding 0.25-fold mole of H2WO4 and 0.05-fold mole of Ce(NO3)3 with respect to the number of moles of sulfonic acid groups in Nafion (registered trademark), or (b) a catalyst ink obtained by adding 0.25-fold mole of H2WO4 and 0.05-fold mole of Mn(NO3)3 with respect to the number of moles of sulfonic acid groups in Nafion (registered trademark) An MEA produced using is disclosed. The same document describes that an MEA produced using a catalyst ink containing a deterioration inhibitor (H2WO4, Ce(NO3)3, Mn(NO3)3) has a higher molecular weight retention rate of the solid polymer electrolyte than an MEA produced using a catalyst ink not containing a deterioration inhibitor.

[0004] Patent Document 2 discloses a polymer electrolyte membrane comprising a perfluorosulfonic acid resin and zirconia having a primary particle size of 10 nm, wherein the ratio of the mass of the perfluorosulfonic acid resin (A) to the mass of the zirconia (B) (= A / B ratio) is 99 / 1. The document states: (A) When zirconia that catalytically decomposes hydrogen peroxide is added to a perfluorosulfonic acid resin, adjusting the primary particle size of the zirconia to 1 nm to 50 nm increases the specific surface area of ​​the zirconia and dramatically increases the hydrogen peroxide decomposition reaction site, and (B) This suppresses the degradation of the polymer electrolyte membrane. It is stated.

[0005] Furthermore, Patent Document 3 contains, (a) An electrolyte membrane made of Nafion® is immersed in a 0.1 M sodium tungstate aqueous solution at 90°C for 30 minutes. (b) Next, remove the electrolyte membrane from the aqueous solution and wash it with water. (c) Furthermore, the electrolyte membrane is immersed in 0.5 M sulfuric acid at 90°C for 30 minutes. A transition metal oxide-containing solid polymer electrolyte membrane obtained by this method is disclosed. The document states: (A) By this method, a transition metal oxide-containing solid polymer electrolyte membrane containing 2 wt% tungsten oxide hydrate can be obtained, and (B) Electrolyte membranes containing tungsten oxide hydrate have a lower fluorine elution rate compared to electrolyte membranes that do not contain tungsten oxide hydrate. It is stated.

[0006] As described in Patent Documents 1 to 3, adding certain degradation inhibitors to solid polymer electrolytes improves their durability. Generally, the greater the amount of degradation inhibitor added, the greater the durability of the solid polymer electrolyte. However, when adding a solid degradation inhibitor to a solid polymer electrolyte, if the type and / or average particle size of the degradation inhibitor are inappropriate, a sufficient degradation inhibition effect may not be obtained. This is presumably because if the type of the degradation inhibitor is inappropriate, the degradation inhibitor is oxidized to a stable state, and the reaction with hydrogen peroxide becomes insufficient. Also, if the average particle size of the degradation inhibitor is inappropriate, it is considered that the degradation inhibitor aggregates in the solid polymer electrolyte, and the decomposition of hydrogen peroxide becomes localized. On the other hand, in order to avoid these problems, simply reducing the addition amount of the degradation inhibitor often results in insufficient durability.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem to be solved by the present invention is to provide a composite electrolyte having a relatively low content of a degradation inhibitor and showing a high degradation inhibition effect.

Means for Solving the Problems

[0009] In order to solve the above problems, the composite electrolyte according to the present invention is a solid polymer electrolyte and tungsten oxide dispersed in the solid polymer electrolyte and is provided with The tungsten oxide contains any one or more selected from the group consisting of WO2 and WO x ·nH2O (2 < x ≦ 3, 0 ≦ n < 3, x and n each include non-integers), The tungsten oxide has an average primary particle diameter of 10 nm or more and 2000 nm or less.

Advantages of the Invention

[0010] When a tungsten oxide (including hydrates) having a predetermined composition is added to a solid polymer electrolyte and the average primary particle diameter of the tungsten oxide is limited to a predetermined range, high durability can be obtained even if the amount of the tungsten oxide added is relatively small. This is (a) The tungsten oxide has an action of decomposing hydrogen peroxide into harmless substances, and even if the added amount is small, it exhibits a high hydrogen peroxide decomposition effect, and (b) When the average primary particle diameter of the tungsten oxide is within a predetermined range, the tungsten oxide is uniformly dispersed in the solid polymer electrolyte, and even if the added amount is small, it exhibits a high hydrogen peroxide decomposition effect, which is considered to be the case.

Brief Description of the Drawings

[0011] [Figure 1] It is the cumulative F elution amount in the cell durability test of the cells using the cast films of Examples 1 to 7 and Comparative Examples 1 to 3. [Figure 2] It is a diagram showing the relationship between the average primary particle diameter of WO2 and the cumulative F elution amount.

Modes for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the present invention will be described in detail. [1. Composite Electrolyte] The composite electrolyte according to the present invention has the following configuration.

[0013] [Configuration 1] A solid polymer electrolyte, tungsten oxide dispersed in the solid polymer electrolyte, and are provided, the tungsten oxide is WO2 and WO x·nH2O (2 < x ≤ 3, 0 ≤ n < 3, where x and n each include non-integers), and includes any one or more selected from the group consisting of The tungsten oxide has an average primary particle diameter of 10 nm or more and 2000 nm or less Composite electrolyte.

[0014] [Configuration 2] The tungsten oxide is the composite electrolyte according to Configuration 1, having an average primary particle diameter of 10 nm or more and 1000 nm or less.

[0015] [Configuration 3] The tungsten oxide is the composite electrolyte according to Configuration 1 or 2, having an average primary particle diameter of 50 nm or more and 500 nm or less.

[0016] [Configuration 4] The composite electrolyte according to any one of Configurations 1 to 3 that satisfies the following formula (1). 0.0001 ≤ W' / A < 0.25 …(1) However, W' / A is the ratio of the number of moles of tungsten (W') contained in the tungsten oxide to the number of moles of acid groups (A) contained in the solid polymer electrolyte.

[0017] [Configuration 5] (a) A compound containing a metal element, dispersed in the solid polymer electrolyte, (b) Ions of the metal element that are ion-exchanged with protons of the acid groups contained in the solid polymer electrolyte, and / or (c) Ions containing the metal element that are ion-exchanged with protons of the acid groups contained in the solid polymer electrolyte The composite electrolyte according to any one of Configurations 1 to 4, further comprising

[0018] [Configuration 6] The composite electrolyte according to Configuration 5 that satisfies the following formula (2). 0.0005 ≤ M / A ≤ 0.15 …(2) However, M / A is the ratio of the number of moles of the metal element (M) to the number of moles of the acid groups (A).

[0019] [1.1. Solid polymer electrolyte] In the present invention, the material of the solid polymer electrolyte is not particularly limited. The solid polymer electrolyte may be either a fluorine-based electrolyte or a hydrocarbon-based electrolyte. The composite electrolyte may contain one of these solid polymer electrolytes, or two or more. Furthermore, there are no particular limitations on the type of acid group in the solid polymer electrolyte. Examples of acid groups include sulfonic acid groups, carboxylic acid groups, phosphonic acid groups, and sulfonimide groups. The solid polymer electrolyte may contain only one of these acid groups, or it may contain two or more.

[0020] Examples of fluorine-based electrolytes include Nafion®, Flemion®, Aquivion®, and Aciplex®. Fluorine-based electrolytes include not only fully fluorinated electrolytes, which do not contain CH bonds in the polymer structure, but also partially fluorinated electrolytes, which contain both CH and CF bonds in the polymer structure.

[0021] Examples of hydrocarbon electrolytes include, (a) All aromatic hydrocarbon electrolytes consisting of polyether ether ketones, polysulfones, polyethersulfones, polyimides, polyphenylenes, polyamides, polyamideimides, or derivatives thereof, into which acidic groups such as sulfonic acid groups have been introduced. (b) Partially aromatic hydrocarbon electrolytes having an aromatic ring in part of the polymer chain of an aliphatic hydrocarbon electrolyte, These are some examples.

[0022] [1.2. Tungsten Oxide] [1.2.1. Materials] Tungsten oxide is dispersed within a solid polymer electrolyte. "Dispersion" means, (a) A state in which primary particles of tungsten oxide, or higher-order particles such as secondary particles, are surrounded by a solid polymer electrolyte, or (b) A state where a solid polymer electrolyte exists around primary particles of tungsten oxide or higher-order particles such as secondary particles is referred to as Tungsten oxide mainly has the effect of decomposing hydrogen peroxide into harmless substances. Therefore, when an appropriate amount of tungsten oxide is added to the solid polymer electrolyte, deterioration of the solid polymer electrolyte can be suppressed.

[0023] In the present invention, "tungsten oxide" refers to WO2 or WO x ·nH2O (2 < x ≤ 3, 0 ≤ n < 3, where x and n each include non-integers). The composite electrolyte may contain any one of these tungsten oxides, or may contain two or more of them. In particular, WO2 exhibits a higher hydrogen peroxide decomposition ability compared to other tungsten oxides.

[0024] [1.2.2. Average primary particle diameter] The "average primary particle diameter" refers to the average value of the primary particle diameters measured for 100 or more randomly selected primary particles under microscopic observation. The "primary particle diameter" refers to the length (major axis) in the direction where the length of the primary particle is maximum.

[0025] Generally, the smaller the average primary particle diameter of tungsten oxide, the higher the hydrogen peroxide decomposition effect can be obtained with a small amount of addition. However, if the average primary particle diameter of tungsten oxide becomes too small, tungsten oxide may aggregate in the solid polymer electrolyte, and it may become impossible to efficiently decompose hydrogen peroxide. Therefore, the average primary particle diameter of tungsten oxide needs to be 10 nm or more. The average primary particle diameter is preferably 20 nm or more, 50 nm or more, 70 nm or more, 100 nm or more, or 150 nm or more. On the other hand, if the average primary particle diameter of tungsten oxide becomes too large, it can lead to a decrease in the mechanical strength of the composite electrolyte, cracking, and gas leakage. Therefore, the average primary particle diameter of tungsten oxide needs to be 2000 nm or less. Preferably, the average primary particle diameter is 1300 nm or less, 1000 nm or less, 500 nm or less, or 300 nm or less.

[0026] [1.3. Compounds and / or ions containing metallic elements] The composite electrolyte according to the present invention, in addition to tungsten oxide, (a) Compounds containing a specified metal element (hereinafter also referred to as "metal compounds") (b) Ions of a specified metal element, and / or (c) Ions containing a specified metal element It may also include the following: Certain metal compounds and ions primarily have the effect of scavenging radicals. Therefore, adding an appropriate amount of metal compounds, metal element ions, and / or ions containing metal elements to a solid polymer electrolyte can suppress the degradation of the solid polymer electrolyte.

[0027] Examples of metallic elements include Ce, Ag, W, Cs, Sn, Mn, Ti, Co, Ni, Zn, Zr, Ru, Rh, Pd, Pt, and Pr. The composite electrolyte may contain one of these metallic elements, or two or more. The metal element is preferably one or more elements selected from the group consisting of Ce, Ag, Cs, Sn, Mn, and W. This is because all of these elements have a strong effect in suppressing or scavenging radicals.

[0028] The metal compound may be water-soluble or sparingly soluble. When a water-soluble metal compound is used, the metal compound dissociates within the complex electrolyte, and some of the protons of the acid groups of the solid polymer electrolyte are replaced by ions of the metal element or ions containing the metal element. On the other hand, when a sparingly soluble metal compound is used, the metal compound remains dispersed within the solid polymer electrolyte. Examples of metal compounds include nitrates, sulfates, oxides, carbonates, formates, acetates, citrates, perchlorates, phosphates, chlorides, fluorides, hydroxides, and acetylacetonate compounds.

[0029] "Metal element ions" refer to ions composed solely of metal elements. An "ion containing a metallic element" refers to an ion that contains both a metallic element and a nonmetallic element. An example of an ion containing a metallic element is Ce(CH3COO)3. + Ce(CF3COCOOCH3)3 + WO2 2+ These are some examples.

[0030] [1.4. Composition] The composite electrolyte according to the present invention is preferably one that satisfies the following relationship between formula (1) and / or formula (2). 0.0001 ≤ W' / A < 0.25 …(1) 0.0005 ≤ M / A ≤ 0.15 …(2) however, W' / A is the ratio of the number of moles of tungsten (W') contained in the tungsten oxide to the number of moles of acid groups (A) contained in the solid polymer electrolyte. M / A is the ratio of the number of moles (M) of the metal element to the number of moles (A) of the acid group contained in the solid polymer electrolyte.

[0031] [1.4.1. Formula (1)] Equation (1) represents the range of the W' / A ratio. If the W' / A ratio becomes too small, the effect of suppressing the degradation of the solid polymer electrolyte decreases. Therefore, a W' / A ratio of 0.0001 or higher is preferred. More preferably, the W' / A ratio is 0.0002 or higher, and even more preferably, 0.0004 or higher.

[0032] On the other hand, if the W' / A ratio becomes too large, the conductivity of the solid polymer electrolyte decreases, which can cause tungsten oxide to aggregate or the film to crack. Therefore, a W' / A ratio of less than 0.25 is preferable. More preferably, the W' / A ratio is 0.10 or less, and even more preferably, 0.05 or less.

[0033] Composite electrolytes that satisfy the following relationship (1') are particularly preferred. 0.0002 ≤ W' / A ≤ 0.10 …(1')

[0034] [1.4.2. Formula (2)] Even when only tungsten oxide is added to a solid polymer electrolyte, the degradation of the solid polymer electrolyte can be effectively suppressed. However, if certain metal compounds, ions of metal elements, and / or ions containing metal elements are further added in addition to tungsten oxide, the degradation of the solid polymer electrolyte is further suppressed due to their synergistic effect. To obtain such an effect, an M / A ratio of 0.0005 or higher is preferable. More preferably, the M / A ratio is 0.001 or higher, and even more preferably, 0.005 or higher.

[0035] On the other hand, if the M / A ratio becomes too high, the conductivity of the solid polymer electrolyte may decrease. Therefore, an M / A ratio of 0.15 or less is preferred. More preferably, the M / A ratio is 0.10 or less, even more preferably 0.05 or less, even more preferably 0.04 or less, and even more preferably 0.03 or less.

[0036] The composite electrolyte is preferably one that satisfies the following relationship (2'). 0.001 ≤ M / A ≤ 0.10 …(2')

[0037] [2. Method for producing composite electrolytes] The composite electrolyte according to the present invention is (a) Prepare a solution (A) in which a solid polymer electrolyte is dissolved or dispersed in a solvent, (b) To solution (A), further dissolve or disperse tungsten oxide, and optionally metal compounds, ions of metal elements, and / or ions containing metal elements, to form solution (B). (c) Remove the solvent from solution (B) It can be manufactured by doing so.

[0038] Furthermore, various components containing the composite electrolyte according to the present invention can be manufactured by various methods. For example, an electrolyte membrane made of the composite electrolyte can be manufactured by casting solution (B) onto a suitable substrate surface and removing the solvent. Alternatively, the electrolyte membrane may be immersed in an aqueous solution of tungstate to introduce tungstate into the electrolyte membrane, and then treated with acid to immobilize tungsten oxide within the electrolyte membrane. Alternatively, the electrolyte membrane may be immersed in a solution of tungsten alkoxide to introduce tungsten alkoxide into the electrolyte membrane, and then condensed within the electrolyte membrane. Alternatively, tungsten alkoxide may be added to an electrolyte solution, followed by solvent removal and tungsten alkoxide condensation.

[0039] Furthermore, when an electrolyte membrane is fabricated using the composite electrolyte according to the present invention, the electrolyte membrane may consist solely of the composite electrolyte according to the present invention, or it may be a composite of the composite electrolyte and a reinforcing material. In this case, the type of reinforcing material is not particularly limited. For example, as a reinforcing material, (a) Porous membranes and nonwoven fabrics of fluororesins such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkanes (PFA), perfluoroethylenepropene copolymer (FEP), and ethylenetetrafluoroethylene copolymer (ETFE), (b) Porous membranes and nonwoven fabrics of hydrocarbon resins such as polyethylene (PE) and polypropylene (PP), These are some examples.

[0040] A catalyst layer containing a composite electrolyte can be manufactured by further dispersing an electrode catalyst in solution (B) to form solution (C), casting solution (C) onto a suitable substrate surface, and removing the solvent. Alternatively, a catalyst layer may be formed by coating or spraying solution (C) onto the surface of the electrolyte membrane and then removing the solvent.

[0041] [3. Effect] Tungsten oxide has the effect of suppressing the degradation of solid polymer electrolytes. However, when it is added to a solid polymer electrolyte, if the average primary particle size of the tungsten oxide is inappropriate, a sufficient degradation suppression effect may not be obtained.

[0042] In contrast, by adding tungsten oxide (including hydrate) having a predetermined composition to the solid polymer electrolyte, and limiting the average primary particle size of the tungsten oxide to a predetermined range, high durability can be obtained even with a relatively small amount of added tungsten oxide. This is because (a) Tungsten oxide has the effect of decomposing hydrogen peroxide and rendering it harmless, and even a small amount of it shows a high hydrogen peroxide decomposition effect, and, (b) When the average primary particle size of tungsten oxide is set within a predetermined range, the tungsten oxide is uniformly dispersed within the solid polymer electrolyte, and even with a small amount added, it exhibits a high hydrogen peroxide decomposition effect. It is thought that...

[0043] Furthermore, adding a specific metal compound, ion of a metal element, and / or ions containing a metal element to the solid polymer electrolyte in addition to tungsten oxide further improves the durability of the solid polymer electrolyte. This is thought to be because even if radicals are generated from hydrogen peroxide that the tungsten oxide has not completely decomposed, the metal compound, ion of a metal element, and / or ions containing a metal element will scavenge the radicals. [Examples]

[0044] (Examples 1-7, Comparative Examples 1-3) [1. Sample Preparation] [1.1. Example 1] WO2 (manufactured by Kojun Chemical Laboratory Co., Ltd., average primary particle size: 9.0 μm) was pulverized in a beesmill under specified conditions to obtain a WO2 dispersion. Water was used as the solvent for the WO2 dispersion. The average primary particle size of the WO2 after pulverization was 1.7 μm. The WO2 dispersion was added to an electrolyte solution (D2020, Nafion® dispersion solution, 1000EW, 20 wt%, manufactured by Chemours K.K.) and mixed to obtain the first mixture. The amounts of electrolyte solution and WO2 dispersion were set so that W' / A = 0.047.

[0045] Next, 1-propanol, ultrapure water, and an aqueous FeSO4 solution were added to the first mixture and mixed to obtain a cast solution. The aqueous FeSO4 solution is a degradation accelerator for accelerated testing, and the electrolyte acid group Fe 2+ The ion exchange rate was adjusted to be equivalent to 1%. The proportions of 1-propanol, ultrapure water, and FeSO4 aqueous solution were set to be: electrolyte solution:1-propanol (excluding the 1-propanol contained in the electrolyte solution):water (total amount of water contained in ultrapure water, WO2 dispersion, and FeSO4 aqueous solution) = 10:8:2 (mass ratio).

[0046] Casting solution: 4.7 g was placed in a φ100 mm flat petri dish and left to dry for several days in a constant temperature atmosphere (25°C) to obtain a cast film. Next, the cast film was annealed (140°C, 15 minutes). Furthermore, the cast film was removed from the flat petri dish and immersed in ultrapure water and heated (80°C, 20 hours). After that, the cast film was removed and air-dried between filter paper.

[0047] [1.2. Examples 2 and 3] A WO2 dispersion was obtained in the same manner as in Example 1, except that the grinding conditions and the solvent of the dispersion were changed to 1-propanol. The average primary particle size of the WO2 after grinding was 0.76 μm (Example 2) or 0.21 μm (Example 3). A cast film was then prepared in the same manner as in Example 1.

[0048] [1.3. Example 4] A WO2 dispersion was obtained in the same manner as in Example 1, except that the grinding conditions and the solvent of the dispersion were changed to 1-propanol. The average primary particle size of the WO2 after grinding was 0.21 μm. A first mixed solution was then obtained in the same manner as in Example 1. Next, a cast solution was prepared in the same manner as in Example 1, except that 1-propanol, ultrapure water, FeSO4 aqueous solution, and Ce(NO3)3 aqueous solution were added to the first mixture. The amount of Ce(NO3)3 aqueous solution was set to an amount such that M / A = 0.015. The proportions of 1-propanol, ultrapure water, Ce(NO3)3 aqueous solution, and FeSO4 aqueous solution were set to an amount such that electrolyte solution:1-propanol (excluding the 1-propanol contained in the electrolyte solution):water (total amount of water contained in ultrapure water, Ce(NO3)3 aqueous solution, and FeSO4 aqueous solution) = 10:8:2 (mass ratio). A cast film was then prepared in the same manner as in Example 1.

[0049] [1.4. Example 5] A WO2 dispersion was obtained in the same manner as in Example 1, except that the grinding conditions and the solvent of the dispersion were changed to 1-propanol. The average primary particle size of the WO2 after grinding was 0.13 μm. A cast film was then prepared in the same manner as in Example 1.

[0050] [1.5. Example 6] A 5 w / v% W(OEt)6 ethanol solution was added to the electrolyte solution and mixed to obtain the first mixture. The amounts of the electrolyte solution and W(OEt)6 were adjusted so that W' / A = 0.022. Next, 1-propanol, ultrapure water, and FeSO4 aqueous solution were added to the first mixture and mixed to obtain a cast solution. The proportions of 1-propanol, ultrapure water, and FeSO4 aqueous solution were such that electrolyte solution:alcohol (excluding 1-propanol in the electrolyte solution):water (total amount of water in the ultrapure water and FeSO4 aqueous solution) = 10:8:2 (mass ratio). A cast film was then prepared in the same manner as in Example 1, and W(OEt)6 was condensed in the electrolyte film. The average primary particle size of WO3 produced in the cast film was 0.18 μm.

[0051] [1.6. Example 7] A cast film was prepared in the same manner as in Example 6, except that an aqueous Ce(NO3)3 solution was added to the casting solution. The amount of aqueous Ce(NO3)3 solution added was the same as in Example 4, resulting in an M / A ratio of 0.015. The average primary particle size of WO3 generated in the cast film was 0.18 μm.

[0052] [1.7. Comparative Example 1] A cast film was prepared in the same manner as in Example 1, except that WO2 was not added.

[0053] [1.8. Comparative Example 2] A cast film was prepared in the same manner as in Example 1, except that the WO2 was not ground using a bead mill, and unground WO2 particles, 1-propanol, ultrapure water, and an aqueous FeSO4 solution were added to an electrolyte solution, mixed, and then ultrasonically irradiated.

[0054] [1.9. Comparative Example 3] Instead of a WO2 dispersion, WO3 particles with an average primary particle size of 8 nm were used, and the WO3 particles were added to the electrolyte solution so that W' / A = 0.043 to prepare the first mixture. Subsequently, a cast film was fabricated in the same manner as in Example 1, except that the cast solution was prepared and then irradiated with ultrasound.

[0055] [2. Test Method] Cells were fabricated using the prepared cast membranes. Furthermore, cell durability tests (OCV durability tests) were conducted using the obtained cells. The test conditions for the cell durability test were: temperature: 95°C, humidity: 40%RH, anode gas / cathode gas: H2 / Air, test time: 90 hours. Water discharged from the fuel cell during the durability test was collected, and the amount of fluoride ions contained in the collected water was measured to calculate the amount of fluoride eluted.

[0056] [3. Results] Figure 1 shows the cumulative amount of F eluted in cell durability tests of cells using cast membranes for Examples 1-7 and Comparative Examples 1-3. Figure 2 shows the relationship between the average primary particle size of WO2 and the cumulative amount of F eluted. From Figures 1 and 2, the following can be seen.

[0057] (1) When only WO2 was present in the electrolyte membrane, the cumulative amount of F eluted depended on the average primary particle size of WO2. To reduce the cumulative amount of F eluted, it was found that the average primary particle size of WO2 should be 10 nm or larger, 20 nm or larger, 50 nm or larger, 70 nm or larger, 100 nm or larger, or 150 nm or larger. Furthermore, it was found that the average primary particle size of WO2 should be 2000 nm or smaller, 1300 nm or smaller, 1000 nm or smaller, 500 nm or smaller, or 300 nm or smaller. (2) In Example 4, where both WO2 and Ce were added to the electrolyte membrane, the cumulative amount of F eluted was even lower compared to Example 3, where only WO2 was added. This is because Ce 3+ This is thought to be because it eliminated the radicals.

[0058] (3) Comparative Example 3, in which only WO3 was added to the electrolyte membrane, had a higher cumulative amount of F eluted compared to Examples 1-5. This is thought to be because as the average primary particle size decreases, aggregation progresses, reducing the surface area that can react with hydrogen peroxide, and furthermore, the aggregation becomes unevenly distributed, making it difficult to effectively decompose hydrogen peroxide. (4) Example 6, which contains alkoxide-derived WO3, had a W' / A ratio of 0.022, which was about half that of Comparative Example 3. However, the cumulative amount of F eluted was reduced to about 60% compared to that of Comparative Example 3, which used WO3 particles with an average primary particle diameter of 8 nm. Furthermore, the cumulative amount of F eluted in Example 7, which contains alkoxide-derived WO3 and Ce ions, was reduced to about 60% compared to that of Example 6, which does not contain Ce ions.

[0059] Although embodiments of the present invention have been described in detail above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. [Industrial applicability]

[0060] The composite electrolyte according to the present invention can be used in electrolyte membranes, catalyst layers, and ionomers of polymer electrolyte fuel cells and polymer electrolyte water electrolyzers.

Claims

1. Solid polymer electrolytes, Tungsten oxide dispersed in the aforementioned solid polymer electrolyte and Equipped with, The tungsten oxide is WO 2 , and WO x nH 2 It includes one or more selected from the group O (where 2 < x ≤ 3, 0 ≤ n < 3, and x and n each include non-integers), The tungsten oxide has an average primary particle diameter of 10 nm or more and 2000 nm or less. Complex electrolytes. however, The aforementioned "average primary particle diameter" refers to the average value of the primary particle diameter measured for 100 or more randomly selected primary particles under microscopic observation. The aforementioned "primary particle diameter" refers to the length (major axis) in the direction in which the length of the primary particle is maximized.

2. The composite electrolyte according to claim 1, wherein the tungsten oxide has an average primary particle diameter of 10 nm or more and 1000 nm or less.

3. The composite electrolyte according to claim 1, wherein the tungsten oxide has an average primary particle diameter of 50 nm or more and 500 nm or less.

4. The composite electrolyte according to claim 1, satisfying the following formula (1). 0.0001≦W' / A<0.25...(1) However, W' / A is the ratio of the number of moles of tungsten (W') contained in the tungsten oxide to the number of moles of acid groups (A) contained in the solid polymer electrolyte.

5. (a) A compound containing a metal element dispersed in the solid polymer electrolyte, (b) Ions of the metal element that are ion-exchanging with protons of acid groups contained in the solid polymer electrolyte, and / or (c) Ions containing the metal element that are ion-exchanging with the protons of the acid groups contained in the solid polymer electrolyte. The composite electrolyte according to claim 1, further comprising:

6. The composite electrolyte according to claim 5, satisfying the following formula (2). 0.0005 ≤ M / A ≤ 0.15 …(2) However, M / A is the ratio of the number of moles of the metal element (M) to the number of moles of the acid group (A).

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