Composite electrolyte membrane and electrochemical cell

Abstract

To provide an electrolyte membrane with enhanced proton conductivity.SOLUTION: According to the present invention, there is provided a composite electrolyte membrane including a polymer electrolyte and a hydrophilic additive dispersed in the polymer electrolyte, and the polymer electrolyte is made of a perfluorosulfonic acid polymer, and in a scattering pattern obtained by small-atom X-ray scattering measurement (SAXS), the composite electrolyte membrane has, when d is a structural period, a first peak appearing at 1≤d≤5 nm and a second peak appearing at 8≤d≤20 nm, and a ratio I2 / I1 of a scattering intensity I1 of the first peak to a scattering intensity I2 of the second peak is 0.5 or less at 80°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite electrolyte membrane and an electrochemical cell. [Background technology]

[0002] Given the need for fuel cells to be applied to large vehicles, fuel cells that can output high power in high-temperature, low-humidity environments are required, and the polymer electrolyte membranes used in fuel cells are required to have high proton conductivity. Prior art document 1 discloses a composite electrolyte membrane in which oxide nanoparticles are added to a fluorine-based electrolyte membrane to improve proton conductivity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2010147867A1 Summary of the Invention [Problem to be solved by the invention]

[0004] Prior art aimed to increase the water retention capacity of the membrane by using additives, but the challenge was that it was difficult to ensure proton conductivity in low-humidity environments.

[0005] The present invention has been made in view of the above circumstances, and aims to provide an electrolyte membrane having high proton conductivity. [Means for solving the problem]

[0006] According to the present invention, the following inventions are provided. [1] A composite electrolyte membrane comprising a polymer electrolyte and a hydrophilic additive dispersed in the polymer electrolyte, wherein the polymer electrolyte is made of a perfluorosulfonic acid polymer, and wherein the composite electrolyte membrane has, in a scattering pattern obtained by small-atom X-ray scattering measurement (SAXS), a first peak appearing at 1≦d≦5 nm and a second peak appearing at 8≦d≦20 nm, where d is a structural period, and the ratio I2 / I1 of the scattering intensity I1 of the first peak to the scattering intensity I2 of the second peak is 0.5 or less at 80°C and 80% RH. [2] The composite electrolyte membrane according to [1], wherein the change in the d value when the humidity is changed from 80% to 20% at 80°C is 0.5 nm or less. [3] The composite electrolyte membrane according to [1] or [2], wherein the hydrophilic additive has a network or linear microstructure and further has a water vapor adsorption amount of 1 mg / g or more at 80°C and 20% RH. [4] The composite electrolyte membrane according to any one of [1] to [3], wherein the hydrophilic additive is oxide nanoparticles, and the oxide nanoparticles have a crystallite diameter of 5 nm or more and 100 nm or less as measured by XRD. [5] A composite electrolyte membrane according to [4], wherein the oxide nanoparticles have chain-like portions formed by fusion-bonding a plurality of crystallites in a chain shape. [6] The composite electrolyte membrane according to [4] or [5], wherein the oxide nanoparticles contain at least one selected from the group consisting of TiO2, CeO2, SnO2, SiO2, Nb2O5, Al2O3, ZrO2, MgO, and BaTiO3. [7] The composite electrolyte membrane according to any one of [4] to [6], wherein the mass ratio of the oxide nanoparticles to the composite electrolyte membrane is 0.5% or more and 10% or less. [8] The composite electrolyte membrane according to any one of [4] to [7], wherein the d value at 80° C. and 80% RH is 3.7 nm or less. [9] The composite electrolyte membrane according to any one of [1] to [3], wherein the hydrophilic additive is a cellulose nanofiber, and the cellulose nanofiber is carboxymethylated.

[10] The composite electrolyte membrane according to [9], wherein the d value at 80°C and 80% RH is 4.8 nm or less.

[11] A composite electrolyte membrane comprising a polymer electrolyte and oxide nanoparticles dispersed in the polymer electrolyte, wherein the polymer electrolyte is made of a perfluorosulfonic acid polymer, and the oxide nanoparticles have a crystallite diameter of 5 nm or more and 100 nm or less as measured by XRD.

[12] A composite electrolyte membrane comprising a polymer electrolyte and cellulose nanofibers dispersed in the polymer electrolyte, wherein the polymer electrolyte is made of a perfluorosulfonic acid polymer and the cellulose nanofibers are carboxymethylated.

[13] An electrochemical cell comprising a cathode, an anode, and a polymer electrolyte membrane disposed therebetween, wherein the polymer electrolyte membrane is the composite electrolyte membrane according to any one of [1] to

[12] . [Effects of the Invention]

[0007] In the composite electrolyte membrane of the present invention, the crystallinity of the membrane is inhibited, and the water clusters in the membrane are finely divided and highly dispersed, which reduces the distance between the water clusters in the membrane and reduces the resistance when protons move between the water clusters, resulting in excellent proton conductivity. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a model diagram of the structure of an electrolyte membrane of the present invention. [Figure 2] FIG. 1 is a model diagram of the bead-and-loop structure of oxide nanoparticles 150. [Figure 3] FIG. 3 is a diagram showing the state of branches 160 of the oxide nanoparticles 150 in FIG. 2. [Figure 4]1 is a cross-sectional view of a manufacturing apparatus 1 for manufacturing oxide nanoparticles, passing through the center of a burner 2. FIG. [Figure 5] FIG. 5 is an enlarged view of an area X in FIG. [Figure 6] 5 is a cross-sectional view taken along the line AA in FIG. 4. [Figure 7] FIG. 7 is an enlarged view of an area Y in FIG. [Figure 8] 1A is a small-angle X-ray scattering profile obtained using the electrolyte membranes of Example 1 and Comparative Example 1. FIG. 1B is a graph showing the correlation between the d value and humidity in Example 1 and Comparative Example 1. [Figure 9] 1 shows small-angle X-ray scattering profiles obtained using the electrolyte membranes of Example 2 and Comparative Example 2. [Figure 10] 1 shows a small-angle X-ray scattering profile obtained using the electrolyte membrane of Example 3. [Figure 11] FIG. 1 is a diagram showing a method for calculating SAXS peak intensities I1 and I2. [Figure 12] 1 is a graph showing the results of proton conductivity measurements using the electrolyte membranes of Example 1 and Comparative Example 1. [Figure 13] 1 is a graph showing the results of proton conductivity measurements using the electrolyte membranes of Example 2, Example 4, and Comparative Example 2. [Figure 14] 1 is a graph showing the results of proton conductivity measurements using the electrolyte membranes of Example 3 and Comparative Example 2. [Figure 15] 1 is a graph showing the correlation between the amount of oxide nanoparticles and the amount of water absorption of the composite electrolyte membrane of Example 1. [Figure 16] FIG. 1 is a configuration diagram showing an electrochemical cell 100 in a power generating operation. [Figure 17] FIG. 1 is a configuration diagram showing a state in which an electrochemical cell 100 is performing a water electrolysis operation. [Figure 18] 1 is a graph showing the results of an evaluation of the power generation performance of unit cells using the electrolyte membranes of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently.

[0010] 1.Composite electrolyte membrane The composite electrolyte membrane of the present invention comprises a polymer electrolyte and a hydrophilic additive, and the hydrophilic additive is dispersed in the polymer electrolyte.

[0011] 1-1.Polymer electrolyte The polymer electrolyte of the present invention is made of a perfluorosulfonic acid polymer, which is a polymer containing sulfonic acid groups in the main chain or side chain and further made of perfluorocarbon.

[0012] Examples of perfluorosulfonic acid polymers include Nafion (registered trademark), Flemion (registered trademark), Aquivion (registered trademark), and Aciplex (registered trademark).

[0013] The perfluorosulfonic acid polymer may be a fully fluorinated electrolyte that does not contain a C—H bond in the polymer structure, or may be a partially fluorinated electrolyte that contains a C—H bond and a C—F bond in the polymer structure.

[0014] 1-2. Hydrophilic additives Hydrophilic additives are added to polymer electrolytes to improve proton conductivity. Hydrophilic additives have a network or linear microstructure. When the hydrophilic additive is highly dispersed in the electrolyte and inhibits the crystallization of the electrolyte, the water clusters in the electrolyte become finer and more dispersed, as shown in Figure 1.

[0015] Furthermore, since the effect of inhibiting the crystallization of the electrolyte is achieved by the interaction between the electrolytic polymer and the hydrophilic additive, the more hydrophilic the hydrophilic additive, the better. The water vapor adsorption capacity of the hydrophilic additive is 1 mg / g or more, preferably 4 mg / g or more, at 80°C and 20% RH. This water vapor adsorption capacity is, for example, 1 to 10 mg / g, specifically, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mg / g, and may be within a range between any two of the values ​​exemplified here.

[0016] The amount of water vapor adsorption can be determined, for example, by placing the electrolyte membrane in a cell with a fixed volume, introducing water vapor, and measuring the pressure fluctuation before and after the introduction.

[0017] Examples of hydrophilic additives include (a) oxide nanoparticles and (b) cellulose nanofibers.

[0018] (a) Oxide nanoparticles The oxide nanoparticles are preferably oxides that have surface hydroxyl groups or oxides to which surface hydroxyl groups can be introduced. Examples include TiO2, CeO2, SnO2, SiO2, Nb2O5, Al2O3, ZrO2, MgO, and BaTiO3. The oxide nanoparticles may consist of any one of these oxides or a mixture of two or more oxides.

[0019] The oxide nanoparticles may contain an element having a different valence from the elements included in the above group. The element having a different valence is at least one selected from rare earth elements such as yttrium, group 5 elements such as niobium and tantalum, group 6 elements such as tungsten, and group 15 elements such as antimony. Among these elements, group 5 elements such as niobium and tantalum, or group 6 elements such as tungsten are preferred, with tantalum, niobium, or tungsten being particularly preferred.

[0020] The size (crystallite diameter) of the oxide nanoparticles is preferably 5 to 100 nm, more preferably 5 to 50 nm. Specific examples of this size include 5, 10, 15, 20, 25, 30, 35, 40, 50, and 100 nm, and may be within a range between any two of the values ​​exemplified here. The crystallite diameter can be calculated from the half-width of the peak in the XRD pattern using the Scherrer equation.

[0021] As shown in Figures 2 and 3, the oxide nanoparticles preferably have a structure having chain portions 170 formed by fusion-bonding a plurality of crystallites 120 in a chain shape (hereinafter referred to as a "beaded structure"). The beaded structure preferably has a network-like microstructure in which the chain portions 170 branch at branch points 160. By having such a network structure, crystallization of the electrolyte can be inhibited when the oxide nanoparticles are added to the electrolyte.

[0022] The bead-and-loop structure of oxide nanoparticles will be explained below with reference to the drawings.

[0023] 2 and 3, the oxide nanoparticle 150 has three-dimensional voids 110 surrounded by its branches 160 and the holes present between the branches. The branches 160 are portions where a chain-like portion formed by fusion-bonding a plurality of crystallites 120 that make up the oxide nanoparticle 150 branches off.

[0024] As shown in FIGS. 2 and 3, the oxide nanoparticle 150 has four pores: a first pore surrounded by branch connection points (branch points, hereinafter sometimes simply referred to as branches) b1, b2, b5, b4, and b1; a second pore surrounded by branch points b1, b2, b3, and b1; a third pore surrounded by branch points b2, b3, b6, b7, b5, and b2; and a fourth pore surrounded by branch points b1, b3, b6, b7, b5, b4, and b1. Here, if the surfaces surrounded by the branch points of each pore (first to fourth pores) are defined as pore surfaces, the void 110 is a three-dimensional space surrounded by these four pore surfaces. The oxide nanoparticle 150 has a plurality of pores surrounded by multiple branch points where multiple branches connect. The oxide nanoparticle 150 has a structure in which three-dimensional spaces (voids) surrounded by multiple pores are continuously provided.

[0025] A simple configuration of the oxide nanoparticles 150 may simply include one hole (for example, a first hole surrounded by branch points b1, b2, b5, b4, and b1). In this case, the oxide nanoparticles 150 will have a void 110 equal to the thickness of the crystallite grain of the crystallite 120. An even simpler configuration may be one in which the oxide nanoparticles 150 have one or more branches. Even in this case, the oxide nanoparticles 150 cannot be in close contact with each other due to the presence of branches, and voids 110 can be formed between them.

[0026] The above-described hole may be rephrased as a closed curve (closed loop). Alternatively, it may be rephrased as having a void 110 surrounded by a closed curved surface including the plurality of branch points (for example, branch points b1 to b7) described above. The branch points b1 to b7 may be regarded as the centers of gravity of the metal oxide crystallites that constitute the oxide nanoparticle 150, where the branches are connected to each other, or may be any one point on the crystallite.

[0027] The aggregate of oxide nanoparticles 150 is in a powder form. Such an aggregate is called "oxide powder."

[0028] The average particle size of the oxide nanoparticles 150 in the oxide powder is 0.1 μm to 4 μm, and preferably 0.5 μm to 2 μm. The average particle size of the oxide nanoparticles 150 can be measured by a laser diffraction / scattering particle size distribution measuring device.

[0029] The specific surface area of ​​the oxide powder is 12m 2 / g or more is preferable, and 25m 2 / g or more is more preferable. 2 / g, and specifically, for example, 12, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100m 2 / g and may be within a range between any two of the values ​​exemplified herein.

[0030] The oxide powder preferably has a porosity of 50% or more, and more preferably 60% or more. The porosity is, for example, 50 to 80%, specifically, for example, 50, 55, 60, 65, 70, 75, or 80%, and may be within a range between any two of the values ​​exemplified here. The porosity can be determined by the ratio of the bulk density of the oxide powder molded using a uniaxial pressure molding machine (molded body size: 5 mm × 5 mm × 30 mm, molding pressure 2 MPa or less) to the true density of the oxide powder, or by mercury intrusion porosimetry or FIB-SEM.

[0031] The oxide powder preferably has an angle of repose of 50 degrees or less, more preferably 45 degrees or less. In this case, the oxide powder has the same fluidity as wheat flour and is easy to handle. The angle of repose is, for example, 20 to 50 degrees, specifically, for example, 20, 25, 30, 35, 40, 45, or 50 degrees, and may be within a range between any two of the values ​​exemplified here. The angle of repose can be determined by the falling volume method. <Method of manufacturing oxide nanoparticles having a bead-like structure> The oxide powder, which is an aggregate of oxide nanoparticles having a bead-like structure, can be produced by the following powder formation process.

[0032] First, a manufacturing apparatus 1 that can be used to manufacture oxide nanoparticles will be described with reference to Figures 4 to 7. The manufacturing apparatus 1 includes a burner 2, a raw material supply unit 3, a reaction tube 4, a recovery vessel 5, and a gas storage unit 6. The raw material supply unit 3 includes an outer tube 13 and a raw material distribution tube 23.

[0033] The burner 2 is cylindrical, and the raw material supply unit 3 is disposed inside the burner 2. Burner gas 2a flows between the burner 2 and the outer casing 13. The burner gas 2a is used to form a flame 7 at the tip of the burner 2 upon ignition. The flame 7 forms a high-temperature region of 1000°C or higher. The burner gas 2a preferably contains a flammable gas such as propane, methane, acetylene, hydrogen, or nitrous oxide. In one example, a mixed gas of oxygen and propane can be used as the burner gas 2a. The temperature of the high-temperature region is, for example, 1000 to 2000°C, specifically, for example, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, or 2000°C, and may be within a range between any two of the values ​​exemplified here.

[0034] A raw material solution 23a for producing oxide nanoparticles flows through the raw material flow tube 23. The raw material solution 23a contains a metal compound. Examples of the metal compound include fatty acid metal (Ti, Ce, etc.) salts. The number of carbon atoms in the fatty acid is, for example, 2 to 20, preferably 4 to 15, and more preferably 6 to 12. The fatty acid is preferably octylic acid.

[0035] The raw material solution 23a may contain a metal compound for doping the oxide nanoparticles 150. Examples of the metal compound include fatty acid metal salts (Nb, Ta, W, etc.). The number of carbon atoms in the fatty acid is, for example, 2 to 20, preferably 4 to 15, and more preferably 6 to 12. Preferred examples of the fatty acid metal salts include niobium octylate, tantalum octylate, antimony octylate, and tungsten octylate.

[0036] In the raw material solution 23a, the metal compound is preferably dissolved or dispersed in a non-aqueous solvent. Examples of the non-aqueous solvent include organic solvents such as turpentine. If the raw material solution 23a contains water, the fatty acid metal salt may be hydrolyzed and deteriorated.

[0037] A mist-forming gas 13a used to atomize the raw material solution 23a flows between the outer cylinder 13 and the raw material flow cylinder 23. When the mist-forming gas 13a and the raw material solution 23a are ejected together from the tip of the raw material supply unit 3, the raw material solution 23a is atomized. A mist 23b of the raw material solution 23a is sprayed into the flame 7, and the metal compound in the raw material solution 23a undergoes a thermal decomposition reaction in the flame 7, producing oxide nanoparticles 150 having chain-like portions formed by fusion-bonding crystallites 120 into a chain shape. One example of the mist-forming gas 13a is oxygen.

[0038] The reaction tube 4 is provided between the collector 5 and the gas storage section 6. A flame 7 is formed in the reaction tube 4. The collector 5 is provided with a filter 5a and a gas outlet 5b. Negative pressure is applied to the gas outlet 5b. As a result, an airflow toward the gas outlet 5b is generated in the collector 5 and the reaction tube 4.

[0039] The gas storage section 6 is cylindrical and includes a cooling gas inlet 6a and a slit 6b. A cooling gas 6g is introduced into the gas storage section 6 through the cooling gas inlet 6a. The cooling gas inlet 6a is oriented in a direction tangent to the inner peripheral wall 6c of the gas storage section 6, so that the cooling gas 6g introduced into the gas storage section 6 through the cooling gas inlet 6a swirls along the inner peripheral wall 6c. A burner insertion hole 6d is provided in the center of the gas storage section 6. A burner 2 is inserted through the burner insertion hole 6d. The slit 6b is positioned adjacent to the burner insertion hole 6d and surrounds the burner insertion hole 6d. Therefore, when the burner 2 is inserted through the burner insertion hole 6d, the slit 6b surrounds the burner 2. The cooling gas 6g in the gas storage section 6 is driven by the negative pressure applied to the gas outlet 5b and discharged from the slit 6b toward the reaction tube 4. The cooling gas 6g may be any gas capable of cooling the generated metal oxide, and is preferably an inert gas, such as air. The flow rate of the cooling gas 6g is preferably at least twice that of the burner gas 2a. The upper limit of the flow rate of the cooling gas 6g is not particularly specified, but may be, for example, 1,000 times that of the burner gas 2a. The ratio of the flow rate of the cooling gas 6g to the flow rate of the burner gas 2a is, for example, 2 to 1,000, and more specifically, may be, for example, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, 500, or 1,000, or may be within a range between any two of the values ​​exemplified here. In this embodiment, the cooling gas 6g is caused to flow by applying negative pressure to the gas outlet 5b, but the cooling gas 6g may also be caused to flow by applying positive pressure to the cooling gas inlet 6a.

[0040] After the oxide nanoparticles 150 leave the flame 7, they are immediately cooled by the cooling gas 6g, so that the structure having chain portions is maintained. The cooled oxide nanoparticles 150 are captured and collected by the filter 5a. The captured oxide nanoparticles 150 may be heat-treated at 400 to 1000°C to adjust them to a desired crystallite size.

[0041] In the present invention, oxide nanoparticles 150 can be produced by using a production apparatus 1 to form a high-temperature region of 1000°C or higher by a flame 7 at the tip of a burner 2, and by thermally decomposing a metal compound in this high-temperature region while supplying a cooling gas 6g to the periphery of the high-temperature region through a slit 6b. The high-temperature region may be formed by a source other than the flame 7, such as plasma.

[0042] The amount of oxide nanoparticles contained in the composite electrolyte membrane is 0.5% to 10%, preferably 1% to 4%, in mass ratio to the composite electrolyte membrane, and specifically, for example, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10%, and may be within a range between any two of the values ​​exemplified here. If the content of oxide nanoparticles is too low, sufficient effect cannot be obtained, while if it is too high, the formation of proton conduction paths in the membrane is inhibited, resulting in a decrease in proton conductivity.

[0043] (b) Cellulose-based nanofibers Cellulose nanofibers are fibers made of cellulose or a cellulose derivative, and have a number average minor axis diameter of 1 nm to 1000 nm or less and an aspect ratio (number average major axis diameter / number average minor axis diameter) of 50 or more. The number average minor axis diameter is preferably 1 nm to 10 nm, more preferably 2 to 5 nm, and specifically, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nm, and may be within a range between any two of the values ​​exemplified here.

[0044] The cellulose nanofibers are preferably those in which the hydroxyl groups are substituted with acetyl groups, alkyl groups, etc., and are more preferably carboxymethyl cellulose nanofibers (CMCNF). Carboxymethylation can impart high dispersibility.

[0045] 1-3.Small angle X-ray scattering (SAXS) Small-angle X-ray scattering measurements can be performed using a commercially available general-purpose X-ray device, such as the Rigaku NANO-Viewer nanoscale X-ray structure evaluation device.

[0046] In small-angle X-ray scattering measurements, for example, X-rays such as CuKα rays are irradiated onto a sample, and the scattered X-rays are detected by a semiconductor detector. The horizontal axis is the scattering vector q (nm -1 ) and obtain a one-dimensional scattering profile with the vertical axis representing the scattering intensity. By measuring the scattered X-rays that appear in the low-angle region (for example, 2θ<10°), structural information on the order of a few nm to a few tens of nm can be obtained. The structural period d value can be calculated from 2π / (the value of q at which the scattering intensity reaches its maximum value). The smaller the d value, the finer the structure of the sample.

[0047] For Nafion etc., q is usually 1 to 6 nm. -1 The first peak is near (d=1-5 nm) and the second peak is near (q=0.3-0.8 nm). -1 A second peak (d=8 to 20 nm) is observed. The first peak is due to water clusters in the electrolyte membrane, and the second peak is due to the crystallinity of the electrolyte polymer. In the composite electrolyte membrane of the present invention, the crystallinity of the electrolyte polymer is low, so that either the second peak is not observed, or, as shown in FIGS. 8 to 10, when the intensity of the first peak is I1 and the intensity of the second peak is I2, the I2 / I1 ratio at 80°C and 80% RH is 0.5 or less, preferably 0.3 or less. Specific examples of the I2 / I1 value are 0, 0.1, 0.2, 0.3, 0.4, and 0.5, and may be within a range between any two of the values ​​exemplified here or less than any of them.

[0048] The calculation method for I1 and I2 is shown in Figure 11. For example, in the case of I2, there are minimum values ​​before and after the second peak in the SAXS graph. The equation of a linear function connecting these minimum values ​​is calculated, and the d value (x-axis value) of the second peak is substituted into the equation of the linear function to obtain the baseline (y-axis value) of the intensity of the second peak. I2 is calculated by subtracting the baseline of the intensity from the absolute value of the second peak intensity. I1 can be calculated in the same way.

[0049] As shown in FIGS. 8 to 10 and Table 1, the d value calculated from the first peak of the composite electrolyte membrane changes by 0.5 nm or less, preferably 0.2 nm or less, when the humidity is changed from 80% RH to 20% RH at 80°C. Specifically, the d value may be, for example, 0, 0.1, 0.2, 0.3, 0.4, or 0.5 nm, or may be within a range between any two of the values ​​exemplified here.

[0050] When the hydrophilic additive is TiO2, the d value is 3.7 nm or less, preferably 3.5 nm or less, at 80°C and 80% RH, as shown in Figure 8 and Table 1, and specifically, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, or 3.7 nm, and may be within a range between any two of the values ​​exemplified here or less than any one of them.

[0051] Furthermore, when the hydrophilic additive is carboxymethyl cellulose nanofiber, the d value is 4.8 nm or less at 80°C and 80% RH, as shown in Figure 10 and Table 1, and specifically, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 4.8 nm, and may be within a range between any two of the values ​​exemplified here or less than any one of them.

[0052] 2. Manufacturing method of composite electrolyte membrane The composite electrolyte membrane of the present invention may be produced by any method, for example, by forming a coating liquid containing a polyelectrolyte polymer, a hydrophilic additive, a liquid medium, and, if necessary, other components.

[0053] Examples of methods for dispersing a hydrophilic additive in a polyelectrolyte polymer include a homogenizer, Filmics, and a bead mill.

[0054] Specific examples of methods for producing a polymer electrolyte membrane using a coating liquid include a method in which the coating liquid is applied to a support such as a substrate film or a catalyst layer, and then dried (casting method).

[0055] The method for applying the coating liquid onto the support is not particularly limited, and examples thereof include methods using a coating device such as a roller, dipping, spray coater, roll coater, die coater, applicator, or spin coater.

[0056] The obtained polymer electrolyte membrane may be further subjected to post-treatments such as heat treatment or pressure application. When heat treatment is performed, the crystallinity of the polymer electrolyte membrane increases and the proton conductivity decreases with increasing heat treatment temperature, so the heat treatment temperature is preferably 100 to 200°C, and more preferably 100 to 160°C. Specific examples of the heat treatment temperature are 100, 120, 140, 160, 180, and 200°C, and may be within a range between any two of the values ​​exemplified here.

[0057] The composite electrolyte membrane produced by the above method has a membrane thickness of 8 to 50 nm, preferably 8 to 30 nm, specifically, for example, 8, 10, 20, 30, 40, or 50 nm, or may be within a range between any two of the numerical values ​​exemplified here.

[0058] 3. Electrochemical Cell 16, the electrochemical cell 100 has a load R connected between the cathode 200 and the anode 300, and when oxygen is supplied to the cathode 200 and hydrogen is supplied to the anode 300, an electromotive force is generated and water is produced by the cathode reaction and the anode reaction shown below. The generated electromotive force causes electrons to move from the anode 300 to the cathode 200 through the load R, and H + moves from the anode 300 to the cathode 200 through the proton exchange membrane 400. In this case, the electrochemical cell 100 becomes a proton exchange membrane fuel cell and operates to generate electricity. Cathode: H + +1 / 4O2+e - →1 / 2H2O Anode: 1 / 2H2 → H + +e -

[0059] 17, when a voltage is applied between the cathode 200 and the anode 300 and water is supplied to the anode 300, the following cathode and anode reactions occur, generating hydrogen from the cathode 200 and oxygen from the anode. Electrons move from the anode 300 to the cathode 200 through the wiring, and H + moves from the anode 300 to the cathode 200 through the proton exchange membrane 400. In this case, the electrochemical cell 100 becomes a proton exchange membrane water electrolysis cell and performs water electrolysis operation. Cathode: H + +e - →1 / 2H2 Anode: 1 / 2H2O → 1 / 4O2 + H + +e -

[0060] In the electrochemical cell 100, the proton exchange membrane 400 plays a role in transferring protons from one electrode to the other electrode. In one embodiment of the electrochemical cell 100, the composite electrolyte membrane of the present invention is used as the proton exchange membrane 400, thereby improving proton conductivity and enabling the production of a high-performance fuel cell or water electrolysis cell. [Example]

[0061] Composite electrolyte membranes were produced by the following methods and various evaluations were carried out. Note that these are merely examples and do not limit the scope of the present invention. Example 1 1. Manufacturing method of oxide powder Oxide powder was produced using the production apparatus 1 shown in Figures 4 to 7. Burner gas 2a was a mixture of 5 L / min of oxygen and 1 L / min of propane gas. This gas was ignited to form a flame (chemical flame) 7 at a temperature of 1600 °C or higher at the tip of burner 2. Titanium octylate and tantalum octylate were mixed and dissolved in mineral split turpentine to form raw material solution 23a. Oxygen was used as mist-forming gas 13a. 9 L / min of mist-forming gas 13a was mixed with 3 g / min of raw material solution 23a, and the mixture was sprayed from the tip of raw material supply unit 3, which is a spray nozzle (atomizer), toward the center of the flame. The mixture was burned to produce oxide powder, which is an aggregate of oxide nanoparticles 150. Negative pressure was applied to gas outlet 5b, allowing air to be drawn through slit 6b at a flow rate of 170 L / min. The produced oxide powder was collected in collector 5 (with filter 5a). The raw material supply section 3 has a double-pipe structure (total length 322.3 mm), and oxygen gas is supplied from the outer cylinder 13, and raw material solution 23a is supplied to the raw material circulation cylinder 23. The tip of the raw material circulation cylinder 23 is equipped with a fluid nozzle and an air nozzle, where the raw material solution 23a is converted into mist 23b. The amount of powder recovered after 60 minutes of operation was 10 g or more.

[0062] 2. Manufacturing method of composite electrolyte membrane The powder of Ta-TiO2 nanoparticles obtained in 1 was atomized using a wet atomizer (150 MPa, Star Burst, Sugino Machine), filtered using filter paper (25 μm), and dried at 80°C for 3 hours.

[0063] The pretreated nanoparticle powder was dispersed in a water / 2-propanol mixture using an ultrasonic nanodisperser (PR-1, Thinky) at 60 Hz for 60 minutes. The resulting dispersion was mixed with Nafion solution (D2020, Chemours Com.) using a planetary ball mill (PULVERISETTE 7, FRITSCH) at 270 rpm for 30 minutes. The resulting mixture was degassed for 5 minutes using a stirrer / degasser (HM-400W, Kyoritsu Seiki) to obtain a mixed solution of Ta-TiO2 nanoparticles and Nafion.

[0064] The mixed solution obtained above was applied six times to a film thickness of 40 μm using a die coater (Taku Daimini 50, Daimon), and then dried with hot air. The coated film was hot-pressed at 140 °C for 3 minutes (TCMD-2.5, Toho Kogyo) to obtain a composite electrolyte membrane.

[0065] <Example 2> Oxide nanoparticles and a composite electrolyte membrane were produced in the same manner as in Example 1, except that cerium octylate and niobium octylate were used as the raw material solution 23a, and commercially available DE521 was used as the Nafion solution. Example 3 Since carboxymethyl cellulose nanofiber (CMCNF) is vulnerable to acids, Nafion neutralized with potassium hydroxide was used in step 2. After coating, hot pressing was performed at 160°C for 3 minutes. After hot pressing, the electrolyte membrane was immersed in a 0.1M aqueous sulfuric acid solution for 1 hour to perform ion exchange, thereby obtaining a composite electrolyte membrane. Other than the above steps, the composite electrolyte membrane was produced in the same manner as in Example 2.

[0066] Example 4 Oxide nanoparticles and a composite electrolyte membrane were produced in the same manner as in Example 2, except that cerium octylate and zirconium octylate were used as the raw material solution 23a.

[0067] <Comparative Examples 1 and 2> A commercially available pre-formed membrane (NRE212) was used as the electrolyte membrane of Comparative Example 1. Furthermore, a commercially available pre-formed membrane (NRE211) was used as the electrolyte membrane of Comparative Example 2.

[0068] [Table 1]

[0069] 3. Evaluation of Polymer Electrolyte Membranes <Small angle X-ray scattering> The crystal long period in the composite electrolyte membrane was measured by small-angle X-ray scattering using a transmission method with a Rigaku NANO-Viewer. The sample was irradiated with CuKα radiation (1.2 kW, 1.58 Å), and scattering was detected using a semiconductor detector, PILATUS100K. The sample was set so that the sample surface was perpendicular to the X-ray incidence direction. The measurement conditions were 80°C and humidity of 20%, 40%, 60%, and 80%. For Comparative Example 1, the measurement conditions were 80°C and humidity of 30%, 50%, 70%, and 90%.

[0070] The results are shown in Figures 8 to 10 and Table 1. In all of Examples 1 to 3, the second peak was either not observed or its intensity was low, confirming that the crystallinity of the electrolyte membrane polymer was low. In Example 1, the d value at high humidity was smaller than in Comparative Example 1, confirming that the water clusters in the membrane were finer. Furthermore, in Example 1, the change in the d value with changes in humidity was smaller than in the Comparative Example, confirming that the change in the water absorption of the membrane was smaller.

[0071] <Proton conductivity measurement> The proton conductivity in the membrane thickness direction was measured by the four-terminal method using AC impedance under the conditions of 80°C and humidity of 20%, 40%, 60%, and 80%.

[0072] The results are shown in Figures 12 to 14 and Table 1. In all of Examples 1 to 3, improvements in proton conductivity were confirmed at all humidity levels compared to Comparative Examples 1 and 2.

[0073] <Water absorption measurement> The amount of water absorbed by the electrolyte membrane was measured gravimetrically using a moisture adsorption / desorption measuring device at various humidity levels at 80°C and 20%, 40%, 60%, and 80% humidity.

[0074] The results are shown in Figure 15. In Example 1, the amount of water absorbed by the electrolyte membrane remained almost constant at each humidity level even when the amount of oxide nanoparticles increased. This confirmed that the improvement in proton conductivity of the electrolyte membrane in Example 1 was not due to an increase in the amount of water absorbed by the membrane caused by the additive.

[0075] 4. Power generation performance A single cell was constructed using the electrolyte membranes of Example 1 and Comparative Example 1 in a standard cell established by the Japan Automobile Research Institute (JARI). A commercially available Pt / CB catalyst (TEC10E50E, Tanaka Kikinzoku) was used as the supported metal catalyst, and the amount of supported metal catalyst used was 0.30 mg / cm. 2 The current-voltage relationship for this single cell was obtained at a cell temperature of 120°C, a back pressure of 50 kPa, and a humidity of 20%.

[0076] The results are shown in Figure 18. In Example 1, the output was improved compared to Comparative Example 1, and it was confirmed that the current density was particularly large in the region affected by resistance overvoltage (in the present invention, approximately 0.7 V or less). [Explanation of symbols]

[0077] 1: Manufacturing equipment 2: Burner 2a: Burner gas 3: Raw material supply section 4: Reaction tube 5: Collector 5a: Filter 5b: Gas exhaust section 6: Gas storage section 6a: Cooling gas inlet 6b: Slit 6c: Inner wall 6d: Burner insertion hole 6g: Cooling gas 7: Flame 13: Outer cylinder 13a: Mist gas 23: Raw material distribution cylinder 23a: Raw material solution 23b: Mist 100: Electrochemical cell 110 :Void 120: Crystallite 150: Oxide nanoparticles 160: branch 170: Chain part 200: Cathode 300: Anode 210: Cathode side gas diffusion layer 220: Cathode side microporous layer 230: Cathode side catalyst layer 310: Anode side gas diffusion layer 320: Anode side microporous layer 330: Anode side catalyst layer 400: Proton exchange membrane

Claims

1. a polyelectrolyte; a hydrophilic additive dispersed in the polymer electrolyte, the polymer electrolyte is made of a perfluorosulfonic acid polymer; The composite electrolyte membrane has a scattering pattern obtained by small nucleus X-ray scattering measurement (SAXS) that is When the structural period is d, a first peak appears at 1≦d≦5 nm and a second peak appears at 8≦d≦20 nm, The ratio I2 / I1 of the scattering intensity I1 of the first peak to the scattering intensity I2 of the second peak is 0.5 or less at 80°C and 80% RH; Composite electrolyte membrane.

2. 2. The composite electrolyte membrane according to claim 1, the change in the d value when the humidity is changed from 80% to 20% at 80°C is 0.5 nm or less; Composite electrolyte membrane.

3. 2. The composite electrolyte membrane according to claim 1, the hydrophilic additive has a network-like or linear microstructure, Furthermore, the water vapor adsorption amount at 80°C and 20% RH is 1 mg / g or more. Composite electrolyte membrane.

4. 2. The composite electrolyte membrane according to claim 1, the hydrophilic additive is an oxide nanoparticle; The oxide nanoparticles are A composite electrolyte membrane having a crystallite diameter measured by XRD of 5 nm or more and 100 nm or less.

5. The composite electrolyte membrane according to claim 4, The oxide nanoparticles have a chain portion formed by fusion-bonding a plurality of crystallites in a chain shape. Composite electrolyte membrane.

6. The composite electrolyte membrane according to claim 4, The oxide nanoparticles are TiO ２ , CeO ２ , SnO ２ , SiO ２ , Nb ２ O ５ , Al ２ O ３ , ZrO ２ , MgO, BaTiO ３ A composite electrolyte membrane comprising at least one selected from the group consisting of:

7. The composite electrolyte membrane according to claim 4, A composite electrolyte membrane, wherein the mass ratio of the oxide nanoparticles to the composite electrolyte membrane is 0.5% or more and 10% or less.

8. The composite electrolyte membrane according to claim 4, The d value at 80°C and 80% RH is 3.7 nm or less; Composite electrolyte membrane.

9. 2. The composite electrolyte membrane according to claim 1, the hydrophilic additive is cellulose nanofiber, The cellulose nanofibers are carboxymethylated. Composite electrolyte membrane.

10. The composite electrolyte membrane according to claim 9, The d value at 80°C and 80% RH is 4.8 nm or less; Composite electrolyte membrane.

11. a polyelectrolyte; and oxide nanoparticles dispersed in the polymer electrolyte, the polymer electrolyte is made of a perfluorosulfonic acid polymer; The oxide nanoparticles are A composite electrolyte membrane having a crystallite diameter measured by XRD of 5 nm or more and 100 nm or less.

12. a polyelectrolyte; A composite electrolyte membrane comprising: cellulose nanofibers dispersed in the polymer electrolyte; the polymer electrolyte is made of a perfluorosulfonic acid polymer; The cellulose nanofibers are carboxymethylated. Composite electrolyte membrane.

13. An electrochemical cell comprising a cathode, an anode and a polymer electrolyte membrane disposed therebetween, An electrochemical cell, wherein the polymer electrolyte membrane is the composite electrolyte membrane according to any one of claims 1 to 12.

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