Polymer electrolyte membrane with improved selectivity

Abstract

The present invention relates to a polymer electrolyte membrane which is used in an energy device, such as a fuel cell or a water electrolysis system, in which a specification standard for lowering hydrogen gas permeability and increasing hydrogen ion conductivity and accordingly, maximizing selectivity, is quantified through small angle X-ray scattering (SAXS) analysis.

Description

Polymer electrolyte membrane with improved selectivity

[0001] The present invention relates to a polymer electrolyte membrane that maximizes selectivity by transmitting hydrogen ions while blocking hydrogen gas. The polymer electrolyte membrane according to the present invention can be applied to hydrogen fuel cells or water electrolysis systems, and can additionally be utilized in energy devices or components such as flow batteries (Redox flow batteries) and reverse electrodialysis (RED).

[0002] The cation-conducting polymer electrolyte membrane (PEM) is an exchange membrane and a separation membrane that must perform the role of transmitting hydrogen ions well while blocking hydrogen gas when applied to energy storage devices. Selectivity, which is a concept meaning the hydrogen gas permeability (or its inverse) compared to the hydrogen ion conductivity, is an important factor that determines performance.

[0003] Hydrogen ions (protons) usually move through ion channels, which are passages through which ions are transferred, so well-developing ion channels in a polymer electrolyte membrane is important for increasing hydrogen ion conductivity.

[0004] Meanwhile, hydrogen gas is primarily absorbed and transported within the amorphous or non-crystalline regions of the polymer, or through adsorption and desorption at the interface between the ion channels and the polymer described above. Therefore, under conditions where the level of ion channels is the same, hydrogen gas permeation can be minimized by minimizing the amorphous regions of the polymer, i.e., increasing the crystalline regions.

[0005] A polymer electrolyte membrane is a unit that must conduct or transmit hydrogen ions well while blocking the permeation of hydrogen gas, and in particular, it is necessary to find a way to minimize the blocking of hydrogen gas.

[0006] When hydrogen gas is permeated, in the case of a fuel cell, the hydrogen gas supplied to the anode permeates the polymer electrolyte membrane and is oxidized at the cathode, resulting in a decrease in cell performance. In the case of a water electrolysis system, the hydrogen gas permeating the polymer electrolyte membrane may react with oxygen gas, resulting in a fire or explosion.

[0007] As a result, increasing hydrogen ion transport while lowering hydrogen gas permeation to increase selectivity is a method that can improve the performance of energy devices / components while suppressing performance degradation or safety accidents.

[0008] Since sufficient ion channels must be secured to effectively transmit hydrogen ions, it is not easy to control permeation by adsorption and desorption at the interface between the ion channels and the polymer in the hydrogen gas permeation mechanism described above.

[0009] Therefore, hydrogen permeation should be suppressed by minimizing the amorphous region of the polymer, i.e., maximizing the crystalline region, and this aspect should be organically considered with the degree of ion channel development.

[0010] Accordingly, the present invention proposes a polymer electrolyte membrane capable of maximizing ion conductivity, i.e., selectivity, compared to hydrogen permeability by quantifying or parameterizing the level of development of a crystal region compared to an ion channel through small angle X-ray scattering (SAXS) analysis.

[0011] The present invention was conceived to solve the above-described problem, and aims to provide a specification standard for lowering the hydrogen gas permeability and increasing the hydrogen ion conductivity of a polymer electrolyte membrane used in energy devices such as fuel cells and water electrolysis systems, thereby maximizing selectivity, by quantifying it through small angle X-ray scattering (SAXS) analysis.

[0012] The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0013] The present invention relates to a polymer electrolyte membrane for maximizing selectivity by increasing hydrogen ion conductivity and decreasing hydrogen gas permeability, according to a preferred embodiment, wherein a slope of a straight line connecting the upper point (A) of a first peak and the upper point (B) of a second peak on a curve obtained through small angle X-ray scattering (SAXS) analysis of the polymer electrolyte membrane is a negative number less than 0, and the upper point (A) of the first peak is an X-axis value (unit: Å) on the curve. -1 ) is a point where the Y-axis value is maximum at 0.01 to 0.1, the upper point (B) of the second peak is a point where the Y-axis value is maximum at 0.1 to 0.4 in the curve, and the thickness of the polymer electrolyte membrane used in the SAXS analysis is 40 to 60 ㎛, the X-ray exposure time is 50 seconds, and the wavelength of the X-ray used is 0.73 Å.

[0014] At this time, the slope of the straight line connecting the first peak upper point (A) and the second peak upper point (B) may be less than 0 and more than -1,000, preferably less than 0 and more than -500, and more preferably from -400 to -100.

[0015] Additionally, the selectivity according to the following formula 1 may be 10 or more, and preferably 15 or more.

[0016] [Formula 1]

[0017] Selectivity (s·cmHg·mS / 10) -10 cm 3 )

[0018] = Hydrogen ion conductivity (mS / cm) / Hydrogen gas permeability (10 -10 cm 3 ·cm / cm 2 ·s·cmHg)

[0019] (The measurement conditions for the above hydrogen ion conductivity are 25°C and 100% relative humidity, and the measurement conditions for the above hydrogen gas permeability are 25°C and 100 kPa.)

[0020] And, the value (b / a) of the crystalline dispacing (d-spacing) (b) compared to the ion channel dispacing (d-spacing) (a) obtained through the SAXS analysis is 1 or more, and the ion channel dispacing (a) may be calculated by substituting the X-axis value (q) at the upper point (B) of the second peak into Equation 2 below, and the crystalline dispacing (b) may be calculated by substituting the X-axis value (q) at the upper point (A) of the first peak into Equation 2 below.

[0021] [Formula 2]

[0022] Dispacing (D-spacing) = 2π / q

[0023] At this time, the value of crystalline dispacing (d-spacing) (b) relative to ion channel dispacing (d-spacing) (a) (b / a) may be 1 to 50, and preferably 3 to 20.

[0024] The hydrogen ion conductivity of the polymer electrolyte membrane under the conditions of 80°C and 50% relative humidity is 0.01 S / cm or more, and the hydrogen gas permeability measured by linear sweep voltammetry (LSV) may be 0.10 to 0.70 mA / cm2. Under the conditions of 80°C and 100% relative humidity, the hydrogen ion conductivity is 0.10 S / cm or more, and the hydrogen gas permeability measured by linear sweep voltammetry may be 0.10 to 0.70 mA / cm2.

[0025] The polymer electrolyte membrane described above can be a PEM for a water electrolysis system or a PEM for a fuel cell.

[0026] The present invention provides a membrane-electrode assembly for a fuel cell or a water electrolysis system comprising a polymer electrolyte membrane as described above, according to another preferred embodiment, and provides a fuel cell or a water electrolysis system comprising the polymer electrolyte membrane as described above.

[0027] According to the present invention as described above, there is an effect in that the conditions for maximizing the selectivity of a polymer electrolyte membrane can be presented by quantifying or measuring the relative development degree of ion channels and amorphous regions through SAXS analysis.

[0028] The effects of the present invention are not limited to those mentioned above, and also include other effects that are not explicitly mentioned, although they can be clearly understood by those skilled in the art from the description throughout the specification.

[0029] FIG. 1 is a small-angle X-ray scattering curve for polymer electrolyte membrane samples 1 to 4 manufactured according to one embodiment of the present invention.

[0030] Figure 2 is a schematic diagram showing the crystalline distribution state according to the heat treatment temperature of a polymer electrolyte membrane manufactured according to one embodiment of the present invention.

[0031] FIG. 3 is a graph showing the slope of a straight line connecting the top points of two peaks in the SAXS curves for polymer electrolyte membrane samples 1 to 4 manufactured according to one embodiment of the invention.

[0032] FIG. 4 is a graph showing the selectivity for polymer electrolyte membrane samples 1 to 4 manufactured according to one embodiment of the invention.

[0033] 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 methods for achieving them, will become clear with reference to the embodiments described in detail below together with the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided only 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. Like reference numerals refer to like elements throughout the specification.

[0034] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by those of ordinary skill 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 terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise.

[0035] The terms "comprises" and / or "comprising" as used in the specification do not exclude the presence or addition of one or more other components, steps, operations and / or elements.

[0036]

[0037] First, the present invention relates to a polymer electrolyte membrane for maximizing selectivity by increasing hydrogen ion conductivity and reducing hydrogen gas permeability, wherein a slope of a straight line connecting the upper point (A) of a first peak and the upper point (B) of a second peak on a curve obtained through small angle X-ray scattering (SAXS) analysis of the polymer electrolyte membrane is a negative number less than 0, and the upper point (A) of the first peak is an X-axis value (unit: Å) on the curve. -1 ) is a point where the Y-axis value is maximum at 0.01 to 0.1, the upper point (B) of the second peak is a point where the Y-axis value is maximum at 0.1 to 0.4 in the curve, and the thickness of the polymer electrolyte membrane used in the SAXS analysis is 40 to 60 ㎛, the X-ray exposure time is 50 seconds, and the wavelength of the X-ray used is 0.73 Å.

[0038] To maximize the selectivity of an electrolyte membrane, it is necessary to maximize ionic conductivity and minimize hydrogen gas permeation. In other words, ion channels must be maximized and hydrogen gas permeation paths must be minimized.

[0039] Since hydrogen gas moves through the amorphous (non-crystalline) region of the polymer as described above, selectivity can be improved by minimizing the amorphous region if the electrolyte has ion channels of the same area.

[0040] Methods for minimizing amorphous regions on polymer electrolyte membranes include, but are not limited to, the following:

[0041] 1) Annealing: When heat treatment is performed at a temperature higher than the boiling point of the solvent but lower than 200°C, the temperature at which sulfonic acid groups are desorbed, that is, at 140 to 200°C, crystallinity can be increased without significantly affecting ionic conductivity.

[0042] 2) Reinforced composite membrane: When the electrolyte membrane is implemented in the form of a reinforced composite membrane that uses a fluororesin such as e-PTFE as a support and is impregnated or coated with an ionomer dispersion, the amorphous region can be minimized, i.e., hydrogen gas permeability can be reduced. In particular, a reinforced composite membrane with a three-layer structure in which a single ionomer coating layer exists on the upper and lower composite layers where the ionomer is impregnated and exists together with the support is advantageous.

[0043] 3) Additives: The amorphous region can be reduced by complexing or blending additives (substances) with an aromatic structure.

[0044]

[0045] Example 1: Small angle X-ray scattering (SAXS) analysis - slope of the straight line connecting the peak tops

[0046] A dispersion was prepared by mixing an appropriate amount of fluorinated ionomer (PFSA) in a mixed solvent of water, propanol, and ethanol using a rotating mixer, applying the dispersion using slot die coating, drying at 80°C, and heat treating for 10 minutes to produce a polymer electrolyte membrane.

[0047]

[0048] Segmentation Heat treatment temperature (℃) Crystalline d-spacing (nm) Ion channel d-spacing (nm) Linear AB Slope Sample 1 1407.9 2.85 9.15 Sample 2 1609.12.7-112.13 Sample 3 18011.7 2.7-338.57 Sample 4 20011.7 2.7-35 1.78

[0049] The results of small-angle X-ray scattering (SAXS) for the polymer electrolyte membranes of samples 1 to 4 are shown in Fig. 1. Among the two peaks, the right peak (second peak) is the ionomer peak, which represents the distance between ion channels, and the left peak (first peak) is the matrix knee, which represents the distance between crystallites. The matrix knee (left peak) is observed between the x-axis values ​​of 0.01 and 0.1, and the ionomer peak (right peak) is observed between the x-axis values ​​of 0.1 and 0.4. The q (X-axis value) value at the peak maximum intensity value (arbitrary unit, au) can be substituted into Bragg's equation described in Equation 2 below to calculate the distance value (dispacing, d-spacing). As shown in Fig. 1, even when the heat treatment temperature increases, the right peak (distance between ion channels) does not show much difference, while the left peak (distance between crystallites) tends to shift to the left.

[0050] In the SAXS curve, the ionomer peak corresponding to the distance between ion channels shifts to the left (the larger the d-spacing), indicating well-developed channels. In addition, in the SAXS curve, the left peak corresponding to the distance between crystallites shifts to the right (the smaller the d-spacing) under the same intensity, indicating well-developed crystal regions. However, in the present example, when the intensity of the peak increases relatively greatly, even if it shifts slightly to the left, it can be interpreted that the crystal region is well-developed. This is believed to be because the crystals are relatively largely developed even though the distance between crystallites is somewhat farther away, and a conceptual diagram explaining this is illustrated in Fig. 2.

[0051]

[0052] Referring to Fig. 3, the degree of crystal development relative to the ion channel can be quantified / quantified through the slope of the straight line connecting the upper points of the first and second peaks in the SAXS curve. Specifically, the slope of the straight line (AB) connecting the upper point (A) of the first peak where the Y-axis value (intensity) is maximum in the X-axis value (q value) range of 0.01 to 0.1 and the upper point (B) of the second peak where the Y-axis value is maximum in the X-axis value range of 0.1 to 0.4 can be defined as a parameter.

[0053] The slope value of the straight line varies depending on the degree of left-right shift between the first and second peaks and the intensity of the first peak. Since the crystal region in the first peak, which is directly related to hydrogen gas permeability, must develop to a certain level and exhibit significant intensity, it is desirable for the first peak to have a negative slope with a larger Y-axis value than the second peak.

[0054] The fact that the slope value decreases with respect to a negative number (the straight line becomes steeper) means 1) that the second peak shifts to the left, that is, that the ion channel dispacing (d-spacing) increases, which means that the ion channel is well developed, thereby increasing the hydrogen ion conductivity (however, the hydrogen gas permeability through the ion channel also increases), 2) that the first peak shifts to the right, which means that the crystalline dispacing decreases, which means that the crystalline region is well developed (the distance between crystals becomes shorter), thereby decreasing the hydrogen gas permeability, and 3) that the intensity value of the first peak increases, which means that the shape and size of the crystals are well developed and well identified, thereby decreasing the hydrogen gas permeability.

[0055] On the other hand, an increase in the slope value based on a negative number (a smoother straight line) means that 1) the second peak shifts to the right, i.e., ion channel dispacing decreases, ion channels become less developed, and thus hydrogen ion conductivity decreases; 2) the first peak shifts to the left, i.e., crystalline dispacing increases, crystalline regions become less developed (the distance between crystals becomes greater), and thus hydrogen gas permeability increases; and 3) the intensity value of the first peak decreases, i.e., the shape and size of crystals become less developed and not easily discernible, and thus hydrogen gas permeability increases.

[0056]

[0057] In conclusion, the smaller the slope value based on the negative number, the better the crystal region is developed compared to the ion channel. Since the development of the ion channel is related to ion conductivity and the development of the crystal region is related to gas permeability, a smaller slope value of the SAXS curve means that the gas permeability is low compared to the ion conductivity, i.e., the selectivity is high.

[0058] In the case of sample 1, the decision region is hardly developed or is not clearly identifiable, so the intensity of the first peak is significantly low, and the upper point of the second peak is relatively high, so it can be confirmed that the slope has a positive value greater than 0.

[0059] On the other hand, samples 2 to 4 have a negative slope value less than 0, so the level of ion channel development is almost the same or similar to that of sample 1, but the crystal region is relatively well developed, so the hydrogen gas permeability is low and the selectivity is high.

[0060] The slope of the straight line connecting the top point of the first peak (A) and the top point of the second peak (B) can be less than 0 and greater than -1,000. If the slope decreases to less than -1,000, the crystal region may be excessively developed, which may excessively increase the brittleness of the polymer. In other words, the electrolyte membrane may be easily broken, making it difficult to apply in practical applications such as fuel cells and water electrolysis.

[0061] In addition, the slope of the straight line can be less than 0 and more than -500, and even when the slope is small, less than -500, the movement of the polymer chains may be restricted due to the well-developed crystal region. That is, when the electrolyte membrane is hydrated in applications such as fuel cells and water electrolysis, the aggregation of the sulfonic acid groups present at the ends of the polymer side chains may be restricted, which may lead to a decrease in device performance.

[0062] In addition, it is preferable that the slope of the straight line be between -400 and -100. If the slope is less than -400, the level of development of the ion channel is significantly lower than the crystal region, making it difficult to secure an appropriate level of ion conductivity, which may result in a decrease in selectivity. If it exceeds -100, the crystal region is not sufficiently developed compared to the ion channel, making it difficult to expect the effect described above. Therefore, in order to secure the optimal selectivity of the electrolyte membrane, it is preferable that the slope value be controlled within the above range.

[0063]

[0064] Example 2: Small angle X-ray scattering (SAXS) analysis - ion channel dispacing versus crystalline dispacing

[0065] Polymer electrolyte membranes of samples 1 to 4 were prepared in the same manner as in Example 1 described above, and SAXS analysis was performed.

[0066]

[0067] Classification Heat treatment temperature (℃) Crystalline d-spacing (nm) Ion channel d-spacing (nm) Crystalline / Ion channel Sample 1 1407.9 2.8 2.7 Sample 2 1609.12 7 3.3 Sample 3 18011.7 2.7 4.3 Sample 4 20011.7 2.7 4.3

[0068] Referring to FIG. 1, the dispacing (d-spacing) value obtained using the X-axis value at the top of the first peak as described above indicates the distance between crystallites, and the dispacing value obtained using the X-axis value at the top of the second peak indicates the distance between ion channels. In FIG. 1 and Table 2, it can be confirmed that the ion channel dispacing does not change much even when the heat treatment temperature increases, while the crystalline dispacing increases. This means that although the change in the ion channel is minimal, the distance between crystallites becomes noticeably farther as the shape and size of the crystallites are strengthened. Therefore, the crystalline dispacing (the “crystallite / ion channel” value in Table 2 above) increases relative to the ion channel dispacing, ultimately improving the selectivity of the polymer electrolyte membrane.

[0069] In conclusion, the selectivity is improved when the value of crystalline dispacing (b) relative to ion channel dispacing (a) (b / a) is 1 or more, that is, when the value of crystalline dispacing is greater than that of ion channel dispacing, and preferably may be 1 to 50, and more preferably may be 3 to 20.

[0070] If the above value (b / a) is below the lower limit, it means that the crystals are not developed sufficiently to inhibit the permeation of hydrogen gas. If it exceeds the upper limit, the crystal region may be excessively developed, which may result in excessively high brittleness of the electrolyte membrane or restricted movement of the polymer chains, which may result in a decrease in device performance.

[0071]

[0072] Example 3: Hydrogen permeability, ionic conductivity, and selectivity by sample

[0073] Polymer electrolyte membranes of samples 1 to 4 were manufactured in the same manner as in Example 1 described above, and the hydrogen permeability (P H2 ) was connected so that one side of the electrolyte membrane was vacuumed and the other side was hydrogen-flowed at 25℃ and 100 kPa, and the pressure change was measured when hydrogen passed through the electrolyte membrane toward the vacuum side, and then the result was substituted into the diffusion formula to calculate it. The ionic conductivity was calculated by connecting the sample to a Bekktech 4 probe cell at 25℃ and 100% relative humidity, measuring the resistance of the electrolyte membrane with an impedance device, and then substituting it into the resistivity formula.

[0074]

[0075] Hydrogen permeability (10 -10 cm 3 ·cm / cm 2 ·s·cmHg)Ionic conductivity (mS / cm)Selectivity (s·cmHg·mS / 10 -10 cm 3 )Sample 15.528014.5Sample 23.917017.9Sample 31.397050.4Sample 41.397050.4

[0076] As mentioned in the SAXS analysis above, it can be confirmed that as the heat treatment temperature for the polymer electrolyte membrane increases, the crystalline domain of the membrane is well developed, and the hydrogen permeability decreases accordingly. In addition, even though the heat treatment temperature increases, the difference in the ion channel is minimal except for sample 1, and the ionic conductivities of samples 2 to 4 were measured to be almost the same. "Selectivity" can be assumed as a parameter indicating the performance of the polymer electrolyte membrane, and a high selectivity means that the polymer electrolyte membrane allows hydrogen ions to pass through well while blocking the permeation of hydrogen gas. Therefore, as shown in Fig. 4, a high selectivity means that the ion conductivity is high compared to the hydrogen permeability.

[0077] The selectivity according to the following equation 1 is a performance indicator of a polymer electrolyte membrane and has no upper limit, and it is preferable to have a value of 15 or more, and more preferably a value of 20 or more.

[0078] [Formula 1]

[0079] Selectivity (s·cmHg·mS / 10) -10 cm 3 )

[0080] = Hydrogen ion conductivity (mS / cm) / Hydrogen gas permeability (10 -10 cm 3 ·cm / cm 2 ·s·cmHg)

[0081] (The measurement conditions for the above hydrogen ion conductivity are 25°C and 100% relative humidity, and the measurement conditions for the above hydrogen gas permeability are 25°C and 100 kPa.)

[0082] If the selectivity value is lower than the lower limit described above, the hydrogen permeability is excessively high compared to the ionic conductivity, which may be fatal to the durability of the device when applied to fuel cells, water electrolysis devices, etc.

[0083]

[0084] The polymer electrolyte membrane according to the present invention can be applied to various energy devices or elements that require high hydrogen ion (cation) conductivity and low hydrogen gas permeability, i.e., good selectivity.

[0085] For example, it can be applied to a PEM for a fuel cell and can be adopted as a component of a membrane-electrode assembly (MEA) or a fuel cell. When applied as a fuel cell or hydrogen fuel cell PEM, the hydrogen ion conductivity of the polymer electrolyte membrane under the conditions of 80°C and 50% relative humidity is 0.01 S / cm or more, and the hydrogen gas permeability measured by linear sweep voltammetry can be 0.10 to 0.70 mA / cm2.

[0086] If the hydrogen ion conductivity falls below 0.01 S / cm, the fuel cell performance may be significantly reduced, and if the hydrogen gas permeability falls outside the above-mentioned range, the fuel cell durability may be significantly reduced.

[0087] As another example, it can be applied to a PEM for water electrolysis and can be adopted as a component of a membrane-electrode assembly (MEA) or a water electrolysis system. When applied as a PEM for a water electrolysis system, the hydrogen ion conductivity of the polymer electrolyte membrane under the conditions of 80°C and 100% relative humidity can be 0.10 S / cm or more, and the hydrogen gas permeability can be 0.10 to 0.70 mA / cm2.

[0088] If the hydrogen ion conductivity is less than 0.10 S / cm, the water electrolysis performance may be significantly reduced, and if the hydrogen gas permeability is outside the above-mentioned range, there is a risk of explosion and fire due to the mixing of hydrogen and oxygen gases.

[0089]

[0090] Although embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical concept or essential features thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. In a polymer electrolyte membrane for maximizing selectivity by increasing hydrogen ion conductivity while reducing hydrogen gas permeability, The slope of the straight line connecting the top point (A) of the first peak and the top point (B) of the second peak on the curve obtained through small angle X-ray scattering (SAXS) analysis of the polymer electrolyte membrane is a negative number less than 0, The upper point (A) of the first peak is the X-axis value (unit: Å) on the curve. -1 ) is the point where the Y-axis value is maximum from 0.01 to 0.1, and the upper point (B) of the second peak is the point where the Y-axis value is maximum from 0.1 to 0.4 in the X-axis value of the curve. A polymer electrolyte membrane characterized in that the thickness of the polymer electrolyte membrane used in the SAXS analysis is 40 to 60 ㎛, the X-ray exposure time is 50 seconds, and the wavelength of the X-ray used is 0.73 Å.

2. In paragraph 1, A polymer electrolyte membrane characterized in that the slope of a straight line connecting the upper point (A) of the first peak and the upper point (B) of the second peak is less than 0 and greater than -1,000.

3. In paragraph 1, A polymer electrolyte membrane characterized in that the slope of a straight line connecting the upper point (A) of the first peak and the upper point (B) of the second peak is less than 0 and greater than -500.

4. In paragraph 1, A polymer electrolyte membrane characterized in that the slope of a straight line connecting the upper point (A) of the first peak and the upper point (B) of the second peak is -400 to -100.

5. In paragraph 1, A polymer electrolyte membrane characterized by a selectivity of 10 or more according to the following formula 1: [Formula 1] Selectivity (s·cmHg·mS / 10) -10 cm 3 ) = Hydrogen ion conductivity (mS / cm) / Hydrogen gas permeability (10 -10 cm 3 ·cm / cm 2 ·s·cmHg) (The measurement conditions for the above hydrogen ion conductivity are 25°C and 100% relative humidity, and the measurement conditions for the above hydrogen gas permeability are 25°C and 100 kPa.) 6. In paragraph 1, A polymer electrolyte membrane characterized by a selectivity of 15 or more according to the following formula 1: [Formula 1] Selectivity (s·cmHg·mS / 10) -10 cm 3 ) = Hydrogen ion conductivity (mS / cm) / Hydrogen gas permeability (10 -10 cm 3 ·cm / cm 2 ·s·cmHg) (The measurement conditions for the above hydrogen ion conductivity are 25°C and 100% relative humidity, and the measurement conditions for the above hydrogen gas permeability are 25°C and 100 kPa.) 7. In paragraph 1, The value of crystalline d-spacing (b) compared to ion channel d-spacing (a) obtained through the above SAXS analysis (b / a) is 1 or more, A polymer electrolyte membrane characterized in that the ion channel dispacing (a) is calculated by substituting the X-axis value (q) at the upper point (B) of the second peak into Equation 2 below, and the crystalline dispacing (b) is calculated by substituting the X-axis value (q) at the upper point (A) of the first peak into Equation 2 below. [Formula 2] Dispacing (D-spacing) = 2π / q 8. In paragraph 7, A polymer electrolyte membrane characterized in that the value of crystalline d-spacing (b) relative to ion channel d-spacing (a) (b / a) is 1 to 50.

9. In paragraph 7, A polymer electrolyte membrane characterized in that the value of crystalline d-spacing (b) relative to ion channel d-spacing (a) (b / a) is 3 to 20.

10. In paragraph 1, A polymer electrolyte membrane characterized in that the hydrogen ion conductivity of the polymer electrolyte membrane under conditions of 80°C and 50% relative humidity is 0.01 S / cm or more, and the hydrogen gas permeability measured by linear sweep voltammetry (LSV) is 0.10 to 0.70 mA / cm2.

11. In paragraph 1, A polymer electrolyte membrane characterized in that the hydrogen ion conductivity of the polymer electrolyte membrane under conditions of 80°C and 100% relative humidity is 0.10 S / cm or more, and the hydrogen gas permeability measured by linear sweep voltammetry (LSV) is 0.10 to 0.70 mA / cm2.

12. In paragraph 1, A polymer electrolyte membrane characterized in that the polymer electrolyte membrane is a PEM for a water electrolysis system or a PEM for a fuel cell.

13. A membrane-electrode assembly for a fuel cell comprising a polymer electrolyte membrane according to any one of claims 1 to 12.

14. A membrane-electrode assembly for a water electrolysis system comprising a polymer electrolyte membrane according to any one of claims 1 to 12.

15. A fuel cell comprising a polymer electrolyte membrane according to any one of claims 1 to 12.

16. A water electrolysis system comprising a polymer electrolyte membrane according to any one of claims 1 to 12.

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