Ionomer dispersion having hight disperse stability and polymer electrolyte membrane manufactured using the same

Abstract

The present invention relates to an ionomer dispersion used to manufacture a polymer electrolyte membrane included in a membrane-electrode assembly of a fuel cell or water electrolysis device, and to a method for manufacturing an ionomer dispersion capable of manufacturing a polymer electrolyte membrane with improved ion conductivity by improving the dispersion stability of the ionomer dispersion through bubble injection and degassing, an ionomer dispersion manufactured thereby, and a polymer electrolyte membrane manufactured using the same.

Description

Technology Field

[0001] The present invention relates to an ionomer dispersion used to manufacture a polymer electrolyte membrane included in a membrane-electrode assembly of a fuel cell or water electrolysis device. In particular, the invention relates to a method for manufacturing an ionomer dispersion in which the dispersion stability of the ionomer dispersion is improved by dispersing a solid ionomer in a solvent through bubble injection and degassing, an ionomer dispersion manufactured thereby, and a polymer electrolyte membrane manufactured using the same. Background Technology

[0002] To realize the commercialization of fuel cells or water electrolysis devices, requirements for high performance and long lifespan must be satisfied, and one of the electrochemical components that has the greatest influence on these requirements is the polymer electrolyte membrane.

[0003] The polymer electrolyte membrane takes the form of a reinforced composite membrane in which an ionomer is impregnated and coated onto a porous support to increase dimensional stability and provide mechanical durability.

[0004] While commonly used porous supports provide the beneficial function of increasing the mechanical strength of polymer electrolyte membranes, they also have the adverse function of increasing the resistance of the membranes because they are formed from materials lacking ion transport capabilities. Therefore, to ensure high performance in polymer electrolyte membranes in the form of reinforced composite membranes, it is necessary to optimize the morphology of the ionomer impregnated and coated onto the porous support.

[0005] Ionomers have a hydrophobic main chain and a hydrophilic side chain, and since these two have different solubility, they are introduced into porous supports in the form of a dispersion rather than a solution.

[0006] Meanwhile, to manufacture dense polymer electrolyte membranes, it is desirable to maximize the ionomer concentration in the solid portion of the dispersion; however, there is a problem in that dispersion stability decreases as the concentration of the solid ionomer in the dispersion increases. Polymer electrolyte membranes manufactured using such dispersions with reduced dispersion stability suffer from high resistance in the thickness direction due to the low impregnation of the dispersion. Furthermore, low dispersion stability prevents the ionomer from acquiring an appropriate morphology within the polymer electrolyte membrane, which consequently not only lowers the planar ion conductivity of the membrane but also increases its gas permeability.

[0007] Therefore, it is very important to prepare an ionomer dispersion with excellent dispersion stability while containing a high content of solid ionomer for manufacturing high-performance polymer electrolyte membranes.

[0008] Figure 1 is a schematic diagram showing the dispersion process of a conventional ionomer dispersion. As shown in Figure 1, in the past, after adding a solid ionomer to a solvent, it was dispersed by applying high energy, such as by applying high pressure or shaking and rotating a basket up and down and left and right.

[0009] However, this dispersion process has limitations in large-scale scale-up, and there is a concern that the physical properties of the ionomer dispersion may change due to heat generated by the applied high energy. Furthermore, not only is a cooling process after dispersion mandatory, but there is also a problem where foreign substances are generated due to friction between the ionomer solids in the dispersion and the basket. The problem to be solved

[0010] The present invention is conceived to solve the aforementioned problems and aims to provide a manufacturing method capable of producing an ionomer dispersion with improved dispersion stability by dispersing a solid ionomer with high dispersibility without applying high energy, an ionomer dispersion produced thereby, a polymer electrolyte membrane produced using the same having improved ion conductivity and durability (tensile strength, etc.), and a water electrolysis device or fuel cell including the same.

[0011] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0012] According to one embodiment of the present invention, a method for preparing an ionomer dispersion comprises the steps of: adding a certain amount of solid ionomer to one or more solvents to prepare a mixture of ionomer and solvent (S100); injecting one or more bubbles of a certain size into the mixture at a certain speed for a certain period of time to prepare an ionomer dispersion in which the ionomer is dispersed in the solvent (S200); and applying an external stimulus to the ionomer dispersion for a certain period of time to degas the bubbles present in the ionomer dispersion (S300).

[0013] In the above ionomer dispersion preparation step (S200), the bubble is characterized as being a mixture of one or more types of bubbles, including a millibubble with a diameter of millimeters (mm), a microbubble with a diameter of micrometers (㎛), and a nanobubble with a diameter of nanometers (㎚).

[0014] In the above ionomer dispersion preparation step (S200), the bubble injection time is characterized as being 30 minutes to 4 hours.

[0015] In the above ionomer dispersion preparation step (S200), the injection speed of the bubbles is characterized as being 10 ml / min to 5,000 ml / min.

[0016] In the above ionomer dispersion preparation step (S200), the method of injecting bubbles is characterized by being at least one of a linear type that injects bubbles upward from the bottom of the mixture to create a linear flow velocity in a vertical direction, a unidirectional rotational type that injects bubbles in one direction from one side to create a rotational flow velocity, and a vortex type that injects bubbles in two or more directions to create a rotational flow velocity.

[0017] In the above bubble degassing step (S300), the external stimulus is ultrasound, and the process is characterized by being carried out for 10 minutes to 2 hours.

[0018] After the above bubble degassing step (S300), the method is further characterized by including an additional bubble degassing step (S400) in which residual bubbles are additionally degassing by creating an atmospheric pressure, pressurized, or depressurized environment through pressure control.

[0019] The above additional bubble degassing step (S400) is characterized by being carried out for 10 minutes to 4 hours.

[0020] According to another embodiment of the present invention, the invention includes an ionomer dispersion prepared by the above-described manufacturing method.

[0021] The above ionomer dispersion is characterized by having a viscosity of 130 cP or less.

[0022] According to another embodiment of the present invention, a polymer electrolyte membrane comprises a porous support layer and an ionomer layer prepared by impregnating and coating the porous support layer with the above ionomer dispersion and then drying it.

[0023] According to another embodiment of the present invention, a membrane-electrode assembly comprising the polymer electrolyte membrane, a water electrolysis device comprising the same, or a fuel cell is included. Effects of the invention

[0024] According to the present invention as described above, the method for manufacturing an ionomer dispersion according to the present invention enables the production of an ionomer dispersion with improved dispersion stability by dispersing solid ionomers with high dispersibility without applying high energy. Therefore, large-scale scale-up is possible, and since no exothermic reaction occurs, there is no concern that the physical properties of the ionomer dispersion will change due to heat. Furthermore, since a cooling process after the dispersion process is not required, it is excellent in terms of process efficiency, and moreover, there is no concern that foreign substances will be generated due to friction between the solid ionomers in the dispersion and the basket.

[0025] By using the ionomer dispersion prepared in this way, it is possible to manufacture polymer electrolyte membranes with enhanced ion conductivity and durability.

[0026] The effects of the present invention are not limited to those mentioned above, and include other effects that are clearly understood by a person skilled in the art from the description throughout the specification but are not explicitly mentioned. Brief explanation of the drawing

[0027] Figure 1 is a schematic diagram showing the dispersion process of a conventional ionomer dispersion. FIG. 2 is a flowchart showing a method for preparing an ionomer dispersion according to the present invention. FIG. 3 is a schematic diagram showing a straight type of bubble injection method for the preparation of an ionomer dispersion according to the present invention, with the left side view and the right side view. FIG. 4 is a schematic diagram showing a one-way rotation type of the bubble injection method for the preparation of an ionomer dispersion according to the present invention, with the left side view and the right top view. FIG. 5 is a schematic diagram showing a vortex type among the bubble injection methods of the ionomer dispersion preparation method according to the present invention, with the left side view and the right side view. Specific details for implementing the invention

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the attached drawings.

[0029] However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0030] Unless otherwise defined, all terms used herein (including technical and scientific terms) may be used in a meaning commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. The terms used herein are for describing embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text.

[0031] As used in the specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0032] FIG. 2 is a flowchart illustrating a method for preparing an ionomer dispersion according to the present invention. As shown in FIG. 2, the method for preparing an ionomer dispersion according to the present invention comprises the steps of: preparing a mixture in which a solid ionomer and a solvent are mixed (S100); injecting bubbles into the mixture to prepare an ionomer dispersion in which the ionomer is dispersed in the solvent (S200); and applying an external stimulus to the ionomer dispersion to degas the bubbles within the ionomer dispersion (S300). Each step is described in detail below.

[0033] The mixture preparation step (S100) is a step of preparing a mixture of solid ionomer and solvent by adding a certain amount of solid ionomer to one or more solvents.

[0034] In the above step (S100), the solid ionomer may be a fluorine-based ionomer, a hydrocarbon-based ionomer, a perfluorosulfonic acid-based ionomer, or a mixture thereof, and specifically, it is preferable to include a perfluorosulfonic acid-based ionomer.

[0035] In the above step (S100), the solvent may be distilled water, an alcohol-based solvent, or a mixture thereof, wherein the alcohol-based solvent may be one or more of methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol.

[0036] In the above step (S100), the solid ionomer and the solvent may be mixed in a weight ratio of 0.1:1 to 1:1. If less solid ionomer is added, it is difficult to manufacture a high-performance polymer electrolyte membrane, and if more solid ionomer is added, it may be added excessively, making it difficult to disperse during the dispersion process.

[0037] The ionomer dispersion preparation step (S200) is a step of preparing an ionomer dispersion in which the ionomer is dispersed in a solvent by injecting one or more bubbles of a certain size into the previously prepared mixture at a constant speed for a certain period of time.

[0038] In the above step (S200), the bubble may be a mixture of one or more types of a millibubble having a diameter of millimeters, a microbubble having a diameter of micrometers, and a nanobubble having a diameter of nanometers, and it is preferable to have a mixture of two or more types for improved dispersibility. Here, a bubble having a diameter of millimeters (mm) is also referred to as Bubbles or giant bubbles, and specifically refers to a bubble having a diameter of 0.5 mm or more. A microbubble having a diameter of micrometers (㎛) is also referred to as Fine Bubbles, and specifically refers to a bubble having a diameter of 500 µm to 1 ㎛. A nanobubble having a diameter of nanometers (nm) is also referred to as Ultrafine Bubbles, and specifically refers to a bubble having a diameter of 1 ㎛ or less.

[0039] In the above step (S200), the injection time of the bubble is preferably 30 minutes to 4 hours, and most preferably 1 to 2 hours. If it is shorter than 30 minutes, sufficient dispersion is not achieved, and if it is longer than 4 hours, the dispersion stability tends to decrease again.

[0040] In the above step (S200), the injection speed of the bubbles is preferably 10 ml / min to 5,000 ml / min. If it is slower than this, sufficient dispersion is not achieved, and if it is faster than this, the dispersion stability tends to decrease again due to excessive bubbles.

[0041] In the above step (S200), a bubble is injected using one or more of air, nitrogen, and inert gas, and the injection speed of the gas represents the injection speed of the bubble.

[0042] In the above step (S200), the method of injecting bubbles is preferably at least one of the following: a linear type in which bubbles are injected upward from the bottom of the mixture to create a linear flow velocity in the vertical direction; a unidirectional rotational type in which bubbles are injected in one direction from one side to create a rotational flow velocity; and a vortex type in which bubbles are injected in two or more directions to create a rotational flow velocity. In fact, FIGS. 3 to 5 are schematic diagrams showing the bubble injection method. FIG. 3 is a schematic diagram showing the linear type, with the left side view and the right top view. FIG. 4 is a schematic diagram showing the unidirectional rotational type, with the left side view and the right top view. FIG. 5 is a schematic diagram showing the vortex type, with the left side view and the right top view.

[0043] In the above step (S200), the dissolution and dispersion of the solid ionomer are promoted and actively carried out by the injected bubbles, but since no heat is generated, the temperature of the ionomer dispersion is maintained without rising.

[0044] The bubble degassing step (S300) is a step of degassing bubbles present in the ionomer dispersion by applying an external stimulus to the previously prepared ionomer dispersion for a certain period of time.

[0045] In the above step (S300), the external stimulus is preferably ultrasound, and the intensity of the ultrasound is preferably 10 to 750 Watts.

[0046] The above step (S300) is preferably carried out for 10 minutes to 2 hours, and most preferably for 1 hour. If it is shorter than 10 minutes, the bubbles are not sufficiently degassed, and if it is longer than 2 hours, the dispersion stability tends to decrease again.

[0047] Meanwhile, after the above step (S300), an additional bubble degassing step (S400) may be further performed to additionally degas the remaining bubbles by controlling the pressure.

[0048] The above additional bubble degassing step (S400) is a step in which degassing proceeds by maintaining the ionomer dispersion for a certain period of time in an atmospheric pressure, pressurized, or reduced pressure environment, due to bubble membrane contraction and increased internal pressure.

[0049] The above step (S400) is preferably carried out for 10 minutes to 4 hours, and most preferably for 1 hour. If it is shorter than 10 minutes, the bubbles are not completely degassed, and if it is longer than 4 hours, the dispersion stability tends to decrease again.

[0050] The method for manufacturing an ionomer dispersion described so far enables the production of an ionomer dispersion with improved dispersion stability by dispersing solid ionomers with high dispersibility without applying high energy. Therefore, large-scale scale-up is possible, and since no exothermic reaction occurs, there is no concern that the physical properties of the ionomer dispersion will change due to heat. Furthermore, since a cooling process after the dispersion process is not required, it is excellent in terms of process efficiency, and there is no concern that foreign substances will be generated due to friction between the solid ionomers in the dispersion and the basket. In one embodiment, the method for manufacturing an ionomer dispersion according to the present invention enables large-scale scale-up production with a capacity of 0.5 to 100 liters, and the most desirable conditions for each step described above can be considered the most optimized conditions when manufacturing based on a capacity of 5 to 20 liters of ionomer dispersion.

[0051] According to another embodiment of the present invention, the invention includes an ionomer dispersion prepared by the method for preparing an ionomer dispersion as described above.

[0052] The ionomer dispersion prepared in this way has a viscosity of 130 cP or less, and using it makes it possible to manufacture polymer electrolyte membranes with improved ion conductivity and durability.

[0053] According to another embodiment of the present invention, a polymer electrolyte membrane comprises a porous support layer and an ionomer layer prepared by impregnating and coating the porous support layer with the above ionomer dispersion and then drying it.

[0054] Meanwhile, according to one embodiment of the present invention, the polymer electrolyte membrane may be in the form of a reinforced composite membrane having a three-stage structure, further including additional ionomer layers disposed on the upper and lower portions of the porous support layer, respectively. In this case, the additional ionomer layer is a layer made of pure ionomer and can be formed simultaneously when the ionomer layer is formed by impregnating and coating the porous support layer with an ionomer dispersion.

[0055] According to another embodiment of the present invention, a membrane-electrode assembly comprising the polymer electrolyte membrane, a water electrolysis device comprising the same, or a fuel cell is included.

[0057] Specific embodiments of the present invention are examined below.

[0058] Comparative Example 1: No bubble injection

[0059] A solid perfluorosulfonic acid-based ionomer (3M, product name EW725) containing SO3 groups was added and mixed in a solvent mixture of distilled water and ethyl alcohol at a weight ratio of 1:1 (ionomer:solvent), then placed in a paste mixer and dispersed by operating at 2,000 rpm for 30 minutes. Afterward, it was removed from the equipment and maintained at room temperature and atmospheric pressure for 6 hours.

[0061] Examples 1 to 3: Bubble injection - Ultrasonic degassing

[0062] A solid perfluorosulfonic acid-based ionomer containing SO3 groups (3M, product name EW725) was added and mixed in a solvent mixture of distilled water and ethyl alcohol at a weight ratio of ionomer to solvent of 1:1. The mixture was then placed in a bubble injection bath and dispersed by injecting bubbles for 1 hour. As shown in Fig. 4, a type that generates a rotational flow rate in one direction was applied for the bubble injection method. Subsequently, the bubbles were degassed by irradiating with ultrasound for a certain period of time. The bubble degassment time (which is also the ultrasonic irradiation time) was adjusted differently according to each example. Specifically, as shown in Table 1 below.

[0063] division Bubble injection time [h] Bubble degassing time [h] (ultrasonic irradiation) Example 1 1 0.5 Example 2 1 1 Example 3 1 2

[0064] Examples 4 to 9: Bubble injection - Ultrasonic degassing - Pressure degassing

[0065] The preparation was carried out in the same manner as in Example 2 above, but after degassing the bubbles by irradiating with ultrasound, additional bubble degassing was performed by maintaining the environment for a certain period under room temperature and atmospheric pressure conditions. The additional bubble degassing time (which is also the atmospheric pressure holding time) was adjusted differently according to each example. Specifically, as shown in Table 2 below.

[0066] division Bubble injection time [h] Bubble degassing time [h] (ultrasonic irradiation) Additional bubble degassing time [h] (maintaining atmospheric pressure) Example 4 1 1 1 Example 5 1 1 2 Example 6 1 1 4

[0067] Meanwhile, the preparation was carried out in the same manner as in Example 4, but the bubble injection time was adjusted differently according to each example. Specifically, as shown in Table 3 below.

[0068] division Bubble injection time [h] Bubble degassing time [h] (ultrasonic irradiation) Additional bubble degassing time [h] (maintaining atmospheric pressure) Example 7 2 1 1 Example 8 3 1 1 Example 9 4 1 1

[0069] Comparative Examples 2 to 4: Bubble injection - Pressure degassing

[0070] The preparation was carried out in the same manner as in Example 2 above, but instead of performing degassing using ultrasound after bubble injection, only pressure degassing was performed by maintaining the environment at room temperature and atmospheric pressure for a certain period of time. The degassing time was adjusted differently for each comparative example. Specifically, as shown in Table 4 below.

[0071] division Bubble injection time [h] Bubble degassing time [h] (ultrasonic irradiation) Additional bubble degassing time [h] (maintaining atmospheric pressure) Comparative Example 2 1 - 1 Comparative Example 3 1 - 4 Comparative Example 4 1 - 6

[0072] The comparative examples and embodiments prepared above are summarized as shown in Table 5 below.

[0073] division Bubble injection time [h] Bubble degassing time [h] (ultrasonic irradiation) Additional bubble degassing time [h] (maintaining atmospheric pressure) Comparative Example 1 - - - Comparative Example 2 1 - 1 Comparative Example 3 1 - 4 Comparative Example 4 1 - 6 Example 1 1 0.5 - Example 2 1 1 - Example 3 1 2 - Example 4 1 1 1 Example 5 1 1 2 Example 6 1 1 4 Example 7 2 1 2 Example 8 3 1 2 Example 9 4 1 2

[0075] Experimental Example 1: Temperature of the ionomer dispersion

[0076] The temperature of the ionomer dispersion after the dispersion process was measured for Comparative Example 1 and Examples 1 to 3 to determine the degree of exothermic reaction. Specifically, for Comparative Example 1, the temperature was measured after mixing and dispersing in a paste mixer, and for Examples 1 to 3, the temperature was measured after dispersing via bubble injection. The measurement results are shown in Table 6 below.

[0077] division Temperature of the ionomer dispersion after the dispersion process [°C] Comparative Example 1 45 Example 1 26 Example 2 25 Example 3 25

[0078] As shown in Table 6 above, in the case of Comparative Example 1, heat generation occurred and the temperature of the ionomer dispersion rose to 45°C, whereas in the case of Examples 1 to 3, no heat generation occurred and the temperature was maintained at room temperature. In other words, unlike conventional dispersion processes that use mixer equipment for mixing, the dispersion process according to the present invention, which disperses by injecting bubbles, does not cause an exothermic reaction, so there is no concern that the physical properties of the ionomer dispersion will change due to heat, and it is excellent in terms of process efficiency as it does not require a cooling process after the dispersion process.

[0080] Experimental Example 2: Particle Size and Viscosity of Ionomer Dispersion

[0081] The particle size and viscosity of the ionomer dispersions of Comparative Examples 1 to 4 and Examples 1 to 9 were measured, respectively. Here, particle size refers to the particle size of the ionomer present in the ionomer dispersion, and a smaller value indicates better dispersion. Viscosity refers to the degree of viscosity of the ionomer dispersion, and a low viscosity value indicates better dispersion. The measurement results are shown in Table 7 below. For reference, viscosity was measured using a cone-plate type instrument at a temperature of 25°C.

[0082] division Bubble injection time [h] Bubble degassing time [h] (ultrasonic irradiation) Additional bubble degassing time [h] (maintaining atmospheric pressure) Particle size [nm] Viscosity [cP] Comparative Example 1 - - - 95 132 Comparative Example 2 1 - 1 180 156 Comparative Example 3 1 - 4 166 141 Comparative Example 4 1 - 6 151 142 Example 1 1 0.5 - 81 130 Example 2 1 1 - 67 120 Example 3 1 2 - 90 130 Example 4 1 1 1 21 102 Example 5 1 1 2 18 108 Example 6 1 1 4 27 104 Example 7 2 1 2 28 98 Example 8 3 1 2 43 109 Example 9 4 1 2 39 111

[0083] As shown in Table 7 above, it was observed that the particle size and viscosity of Examples 1 to 9 were both smaller and had lower values ​​than those of Comparative Examples 1 to 4.

[0084] Meanwhile, Comparative Examples 2 to 4 were cases in which only degassing was performed by maintaining at atmospheric pressure without performing degassing through ultrasonic irradiation after bubble injection, and it was observed that the particle size and viscosity were very large and had high values. This means that in order to improve dispersion stability, a degassing process involving external stimulation, such as ultrasonic irradiation after bubble injection, must be performed.

[0085] Meanwhile, Examples 1 to 3 involved only degassing via ultrasonic irradiation after bubble injection, whereas Examples 4 to 9 involved both degassing via ultrasonic irradiation after bubble injection and additional degassing maintained at atmospheric pressure. It was observed that the particle size and viscosity of Examples 4 to 9 were both smaller and lower than those of Examples 1 to 3. In other words, this implies that performing both degassing with external stimulation, such as ultrasonic irradiation, and additional degassing maintained at a constant pressure is desirable for improving dispersion stability.

[0086] Meanwhile, when comparing Examples 5 and 7 to 9, which differed only in the bubble injection time, it was observed that Examples 8 and 9 had relatively larger particle size and viscosity and higher values ​​than Examples 5 and 7. Therefore, it was found that a bubble injection time of 1 to 2 hours is most desirable.

[0087] As shown in Table 7 above, the ionomer dispersion according to the present invention may have a viscosity of 130 cP or less, more specifically 120 cP or less, and even more specifically 115 cP or less. In addition, the particle size of the ionomer present in the ionomer dispersion may be 90 nm or less, more specifically 70 nm or less, and even more specifically 50 nm or less.

[0089] Preparation Examples 1 to 4: Preparation of polymer electrolyte membranes

[0090] Polymer electrolyte membranes were prepared using the ionomer dispersions of Comparative Example 1 and Examples 4 to 6, respectively. The preparation method was identical for all of them. Specifically, 10 g of the ionomer dispersion was applied onto a porous support polymer film (PET), and then coated to a thickness of 20 μm using a thickness-adjustable applicator. Subsequently, a first drying step was performed at 40°C and a second drying step at 80°C to obtain the final polymer electrolyte membrane.

[0092] Experimental Example 3: Ionic conductivity of a polymer electrolyte membrane

[0093] The ionic conductivity of the polymer electrolyte membranes of Preparation Examples 1 to 4 was measured under RH 100% conditions. The measurement results are shown in Table 8 below.

[0094] division Ionomer dispersion used Ionic conductivity [S / cm] Preparation Example 1 Comparative Example 1 0.126 Preparation Example 2 Example 4 0.133 Preparation Example 3 Example 5 0.137 Preparation Example 4 Example 6 0.131

[0095] As shown in Table 8 above, it was confirmed that the ionic conductivity of Preparation Examples 2 to 4 was further improved compared to Preparation Example 1. Among them, the ionic conductivity of the polymer electrolyte membrane prepared using the ionomer dispersion of Example 5 was the most improved.

[0096] As shown in Table 8 above, the ionic conductivity of the polymer electrolyte membrane according to the present invention may be 0.130 S / cm or higher.

[0098] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 A method for preparing an ionomer dispersion with improved dispersion stability, comprising: a step of preparing a mixture of ionomer and solvent by adding a solid ionomer, including a fluorine-based ionomer, a hydrocarbon-based ionomer, a perfluorosulfonic acid-based ionomer, or a mixture thereof, to a solvent that is distilled water, an alcohol-based solvent, or a mixture thereof; a step of preparing an ionomer dispersion in which the ionomer is dispersed in a solvent by injecting bubbles having one or more sizes into the mixture at an injection rate of 10 ml / min to 5,000 ml / min for 30 minutes to 4 hours; and a step of degassing bubbles present in the ionomer dispersion by applying an external stimulus to the ionomer dispersion for 10 minutes to 2 hours. Claim 2 A method for preparing an ionomer dispersion with improved dispersion stability according to claim 1, wherein, in the step of preparing the ionomer dispersion, the bubble is a mixture of one or more types of a millibubble having a diameter of millimeters (mm), a microbubble having a diameter of micrometers (㎛), and a nanobubble having a diameter of nanometers (㎚). Claim 3 delete Claim 4 delete Claim 5 A method for manufacturing an ionomer dispersion with improved dispersion stability according to claim 1, wherein, in the step of manufacturing the ionomer dispersion, the method of injecting the bubbles is characterized by being at least one of a linear type in which bubbles are injected upward from the bottom of the mixture to create a linear flow velocity in a vertical direction, a unidirectional rotational type in which bubbles are injected in one direction from one side to create a rotational flow velocity, and a vortex type in which bubbles are injected in two or more directions to create a rotational flow velocity. Claim 6 A method for preparing an ionomer dispersion with improved dispersion stability, characterized in that, in the step of degassing the bubbles according to claim 1, the external stimulus is ultrasound. Claim 7 A method for preparing an ionomer dispersion with improved dispersion stability, characterized in that, in claim 1, after the step of degassing the bubbles, it further includes an additional bubble degassing step of creating an atmospheric pressure, pressurized, or reduced pressure environment to additionally degassing the remaining bubbles. Claim 8 A method for preparing an ionomer dispersion with improved dispersion stability, characterized in that, in claim 7, the additional bubble degassing step is carried out for 10 minutes to 4 hours. Claim 9 An ionomer dispersion manufactured by any one of the manufacturing methods of paragraphs 1, 2, 5 through 8. Claim 10 In claim 9, the ionomer dispersion is characterized by having a viscosity of 130 cP or less. Claim 11 A polymer electrolyte membrane comprising: a porous support layer; and an ionomer layer prepared by impregnating and coating the porous support layer with the ionomer dispersion of claim 9 and then drying it. Claim 12 A membrane-electrode assembly comprising the polymer electrolyte membrane of claim 11. Claim 13 A water electrolysis device comprising the membrane-electrode assembly of claim 12. Claim 14 A fuel cell comprising the membrane-electrode assembly of claim 12.

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