Diaphragm for electrochemical cell, electrode laminate for alkaline water electrolysis, and alkaline water electrolysis cell

Abstract

Provided are: a diaphragm having low resistance and high gas tightness; an electrode laminate for alkaline water electrolysis; and an alkaline water electrolysis cell, the electrode laminate and the alkaline water electrolysis cell using the diaphragm. This diaphragm is used in an electrochemical cell and comprises: a porous resin substrate; and a pair of mixed layers which are provided on both sides of the resin substrate and contain inorganic particles and a binder resin, wherein each of the mixed layers is provided to form a surface layer on the surface of the resin substrate and / or incorporated into the resin substrate to form an inner layer, the maximum diameter of pores that may be present in the mixed layers is 40 nm or less, and the thickness of the diaphragm is 100 μm or less.

Description

Diaphragms for electrochemical cells, electrode laminates for alkaline water electrolysis, and alkaline water electrolysis cells

[0001] This disclosure relates to a diaphragm for an electrochemical cell, an electrode laminate for alkaline water electrolysis, and an alkaline water electrolysis cell.

[0002] Alkaline water electrolysis is attracting attention as a useful technology for green hydrogen production using renewable energy. In this technology, for example, a diaphragm plays an important role in separating the hydrogen electrode and the oxygen electrode in the electrolytic cell, enabling the selective passage of ions. Conventional diaphragms for alkaline water electrolysis mainly use porous ceramic materials or polymer materials, and a representative example is the porous membrane (ZIRFON) made of resin and ceramics developed by Agfa-Gevaert (see, for example, Non-Patent Documents 1 and 2). This is a diaphragm used in many water electrolysis devices, and consists of a polyphenylene sulfide (PPS) mesh with zirconium oxide (ZrO) on both sides. ２ It has a structure in which a porous film of polymer is formed, and the specific surface area of ​​zirconium oxide is high, which is thought to provide the porosity and hydrophilicity necessary for ion transport.

[0003] As a diaphragm for alkaline water electrolysis, for example, Patent Document 1 (Japanese Patent No. 7444770) discloses a separator for alkaline water electrolysis comprising a porous support, a first porous polymer layer adjacent to one side of the porous support, and a second porous polymer layer adjacent to the opposite side of the porous support. Patent Document 2 (Japanese Patent Publication No. 2023-531792) discloses a separator for alkaline electrolysis comprising a porous support and a first porous layer and a second porous layer provided on one and the other side of the porous support, characterized in that the porous support has a thickness of 150 μm or less and the separator has a thickness of less than 250 μm. Furthermore, Patent Document 3 (Japanese Patent Publication No. 2024-525620) discloses a separator for alkaline electrolysis comprising a porous support and a porous layer provided on the porous support, characterized in that the lateral bubble point of the separator is at least 0.2 bar.

[0004] Patent No. 7444770 Publication Special Publication No. 2023-531792 Publication Special Publication No. 2024-525620

[0005] Technical Data Sheet ZIRFON PERL UTP 500. [online]. Agfa-Gevaert NV, May 2020. [retrieved on December 3, 2024]. Retrieved from the Internet: <URL: https: / / www.agfa.com / specialty-products / wp-content / uploads / sites / 8 / 2020 / 06 / TDS_ZIRFON_PERL_UTP_500_20200525.pdf> Technical Data Sheet ZIRFON UTP 220. [online]. Agfa-Gevaert NV, April 2021. [retrieved on December 3, 2024]. Retrieved from the Internet: <URL: https: / / www.agfa.com / specialty-products / wp-content / uploads / sites / 8 / 2021 / 05 / TDS_ZIRFON_UTP_220_20210511.pdf>

[0006] Low energy efficiency is a challenge in alkaline water electrolysis. To improve energy efficiency, the diaphragm must exhibit low liquid resistance and high gastightness. Thinning the diaphragm reduces resistance, thereby decreasing ohmic loss and improving energy efficiency and current density. High gastightness of the diaphragm suppresses crossover, preventing the permeation of gases such as hydrogen and oxygen, thus improving energy efficiency. While thinning is desirable to achieve low resistance in the diaphragm, there is a trade-off between diaphragm thickness and gastightness. Conventional diaphragms are insufficient in this regard, leaving a challenge. Therefore, a diaphragm that can achieve both low resistance and high gastightness is desired.

[0007] The present inventors have now discovered that, in a diaphragm used in an electrochemical cell, a diaphragm with low resistance and high gastightness can be provided by providing a pair of mixed layers containing inorganic particles and a binder resin on both sides of a porous resin substrate.

[0008] Therefore, the object of the present invention is to provide a diaphragm with low resistance and high gastightness, as well as an electrode laminate for alkaline water electrolysis and an alkaline water electrolysis cell using the same.

[0009] The following embodiments are provided according to this disclosure: [Embodiment 1] A diaphragm for use in an electrochemical cell, comprising: a porous resin substrate; and a pair of mixed layers provided on both sides of the resin substrate, each of which is provided so as to form a surface layer on the surface of the resin substrate and / or incorporated so as to form an internal layer inside the resin substrate, wherein the maximum diameter of pores that may exist in the mixed layer is 40 nm or less, and the thickness of the diaphragm is 100 μm or less. [Embodiment 2] The diaphragm according to Embodiment 1, wherein the porosity of the mixed layer is 30% or less. [Embodiment 3] The diaphragm according to Embodiment 1 or 2, wherein the mixed layer includes the surface layer, and the thickness of each layer of the surface layer is 15 μm or less. [Embodiment 4] The diaphragm according to any one of Embodiments 1 to 3, wherein the average primary particle size of the inorganic particles is 30 nm or less. [Aspect 5] The diaphragm according to any one of aspects 1 to 4, wherein the inorganic particles include at least one selected from the group consisting of zirconium oxide, titanium oxide, and rare earth oxide. [Aspect 6] The diaphragm according to any one of aspects 1 to 5, wherein the binder resin includes at least one selected from the group consisting of polyvinyl alcohol, polyethylene, polypropylene, and polysulfone. [Aspect 7] The diaphragm according to any one of aspects 1 to 6, wherein the portion of the resin substrate other than the inner layer has a porosity of 25 to 70%. [Aspect 8] The diaphragm according to any one of aspects 1 to 7, wherein the resin substrate includes at least one selected from the group consisting of polyethylene, polypropylene, polysulfone, polyphenylene sulfide, polyether ether ketone, and polymethylpentene. [Aspect 9] The diaphragm according to any one of aspects 1 to 8, wherein the thickness of the resin substrate is 5 to 70 μm. [Aspect 10] The diaphragm according to any one of aspects 1 to 9, wherein the thickness of the diaphragm is 7 to 100 μm. [Aspect 11] A diaphragm according to any one of aspects 1 to 10, wherein the bubble point measured in accordance with ASTM F316-86 is 3.5 MPa or higher.[Aspect 12] An electrode stack for alkaline water electrolysis comprising: an anode as an oxygen-generating electrode; a cathode as a hydrogen-generating electrode; and a diaphragm according to any one of aspects 1 to 11, interposed between the anode and the cathode. [Aspect 13] The electrode stack for alkaline water electrolysis according to aspect 12, wherein the electrode stack has a zero-gap structure in which the anode, the diaphragm and the cathode are stacked in contact with each other. [Aspect 14] An alkaline water electrolysis cell comprising: the electrode stack for alkaline water electrolysis according to aspect 12 or 13; an electrolyte; and a partition wall that divides the internal space containing the electrode stack and the electrolyte.

[0010] This is a schematic cross-sectional view showing an example of the diaphragm of the present invention. This is a schematic cross-sectional view showing an example of the diaphragm of the present invention. This is a schematic cross-sectional view conceptually showing an electrode laminate for alkaline water electrolysis using the diaphragm of the present invention. This is a schematic cross-sectional view showing an example of an alkaline water electrolysis cell using the diaphragm of the present invention. This is a schematic cross-sectional view showing an electrochemical measurement system for measuring the resistance value of the diaphragm. This is a cross-sectional FE-SEM image of a diaphragm formed with a surface layer and an inner layer as a mixed layer, as shown in Example 2. This is a cross-sectional FE-SEM image of a diaphragm formed with a surface layer and an inner layer as a mixed layer, as shown in Example 2.

[0011] The diaphragm is used in electrochemical cells (e.g., battery cells and alkaline water electrolysis cells). As shown in Figures 1A and 1B, the diaphragm 10 comprises a porous resin substrate 12 and a pair of mixed layers 14 provided on both sides of the resin substrate 12. The mixed layers 14 contain inorganic particles and a binder resin. Each of the pair of mixed layers 14 is provided so as to form a surface layer 14a on the surface of the resin substrate 12 and / or is incorporated inside the resin substrate 12 so as to form an internal layer 14b. The maximum diameter of pores that may exist in the mixed layers 14 is 40 nm or less. The thickness of the diaphragm 10 is 100 μm or less. In this way, in a diaphragm 10 used in electrochemical cells, particularly alkaline water electrolysis cells, by providing a pair of mixed layers 14 containing inorganic particles and a binder resin on both sides of the porous resin substrate 12, a diaphragm 10 with low resistance and high gastightness can be provided. Furthermore, the diaphragm 10 can be used in water electrolysis using an alkaline electrolyte (for example, one with a pH greater than 7). In addition to general alkaline water electrolysis (where the pH of the electrolyte used is 14 or higher), it can also be used in non-polar pH water electrolysis (where the pH of the electrolyte used is around 9 to 11). Therefore, "alkaline water electrolysis" using the diaphragm 10 typically refers to water electrolysis using an electrolyte with a pH of 9 or higher.

[0012] In other words, as mentioned above, the performance requirements for a diaphragm include low liquid resistance and high gastightness. By making the diaphragm thin, resistance can be reduced, thereby decreasing ohmic loss, improving energy efficiency, and increasing current density. High gastightness of the diaphragm suppresses crossover, which is caused by the permeation of gases such as hydrogen and oxygen, thereby improving energy efficiency. Thus, thinning is desirable for diaphragms to achieve low resistance, but there is a trade-off relationship between diaphragm thickness and gastightness, and in this respect, conventional diaphragms are insufficient in terms of performance, leaving some issues unresolved. Therefore, a diaphragm that can achieve both low resistance and high gastightness is desired. These issues are successfully resolved according to the present invention. In other words, in the diaphragm 10 of the present invention, a pair of mixed layers 14 are provided on both sides of the resin substrate 12 so as to form a surface layer 14a on the surface of the resin substrate 12 and / or incorporated inside the resin substrate 12 so as to form an internal layer 14b. With this configuration, a dense layer is formed on both sides of the thin diaphragm 10, allowing the electrolyte to pass through while making it difficult for gas to permeate. As a result, the diaphragm 10 is expected to have low resistance and high gas-tightness.

[0013] A pair of mixed layers 14 are provided on both sides of the resin substrate 12 so as to form a surface layer 14a and / or an internal layer 14b. The layer configuration of the mixed layer 14 is not particularly limited as long as it is formed on both sides of the resin substrate 12 as a dense layer that allows electrolyte to pass through while making it difficult for gas to permeate. For example, as shown in Figure 1A, only a surface layer 14a may be formed as the mixed layer 14, or only an internal layer 14b may be formed as the mixed layer 14, or a two-layer mixed layer 14 consisting of a surface layer 14a and an internal layer 14b may be formed on one side of the resin substrate 12, and a one-layer mixed layer 14 consisting of either a surface layer 14a or an internal layer 14b may be formed on the other side of the resin substrate 12. From the viewpoint of gas tightness, it is preferable that a two-layer mixed layer 14 consisting of a surface layer 14a and an internal layer 14b is formed on both sides of the resin substrate 12. Furthermore, the internal layer 14b does not have to be incorporated over the entire thickness of the inside of the resin substrate 12.

[0014] The maximum diameter of pores that may exist in the mixed layer 14 is 40 nm or less, preferably 35 nm or less, more preferably 30 nm or less, and even more preferably 20 nm or less. From the viewpoint of ensuring the gastightness of the diaphragm 10, it is preferable that the maximum diameter of pores that may exist in the mixed layer 14 be small, and although there is no particular lower limit, it is, for example, 0.5 nm or more.

[0015] The porosity of the mixed layer 14 is preferably 30% or less, more preferably 25% or less, even more preferably 20% or less, and particularly preferably 15% or less. As with the above, from the viewpoint of ensuring the gastightness of the diaphragm 10, the mixed layer 14 is typically dense, so the lower limit of the porosity is not particularly limited, but for example it is 1% or more.

[0016] When the mixed layer 14 includes a surface layer 14a, the thickness of each layer of the surface layer 14a is preferably 15 μm or less, more preferably 0.1 to 10 μm, even more preferably 0.1 to 5.0 μm, and particularly preferably 0.1 to 3.0 μm.

[0017] The mixed layer 14 contains inorganic particles and a binder resin. When a diaphragm 10 having such a mixed layer 14 is used in a battery or an alkaline water electrolysis device, the binder resin swells in the electrolyte, and ions can conduct through the gaps in the binder resin as conduction paths. The binder resin is not particularly limited as long as it functions as a base material in which inorganic particles are dispersed and embedded, but it preferably contains polyvinyl alcohol, polyethylene, polypropylene, polysulfone, or a combination thereof, and more preferably polyvinyl alcohol.

[0018] The inorganic particles are not particularly limited as long as they are alkali-resistant yet hydrophilic, but they preferably contain zirconium oxide, titanium oxide, rare earth oxide, or a combination thereof, and more preferably zirconium oxide.

[0019] The average primary particle size of the inorganic particles is preferably 30 nm or less, more preferably 1 to 25 nm, even more preferably 1 to 22 nm, and particularly preferably 1 to 19 nm. Here, "average primary particle size" refers to the average particle size of multiple primary particles contained in the mixed layer 14 of the diaphragm 10. This primary particle size can be measured by image analysis of a cross-sectional FE-SEM image of the diaphragm 10. For example, the diaphragm 10 is processed with a cross-section polisher (CP) to expose the polished cross section. This polished cross section is observed with an FE-SEM (field emission scanning electron microscope) at a predetermined magnification (e.g., 200,000x) and a predetermined field of view (e.g., 5 μm × 5 μm). At this time, the field of view is set so that there are 20 or more primary particles in the field of view. The diameter of the circumscribed circle drawn for all primary particles in the obtained FE-SEM image is determined, and the average value of these can be taken as the average primary particle size.

[0020] The porous resin substrate 12 contained in the diaphragm 10 preferably has a porosity of 25 to 75% in the portion other than the inner layer 14b (i.e., the portion of the resin substrate 12 other than the portion in which the inner layer 14b is incorporated), more preferably 30 to 70%, and even more preferably 40 to 60%.

[0021] The resin substrate 12 is not particularly limited as long as it has low gas permeability and alkali resistance, but it preferably contains polyethylene, polypropylene, polysulfone, polyphenylene sulfide, polyetheretherketone, polymethylpentene, or a combination thereof, and more preferably polyethylene.

[0022] The thickness of the resin substrate 12 is preferably 5 to 70 μm, more preferably 5 to 50 μm, even more preferably 5 to 35 μm, and particularly preferably 5 to 25 μm. The thickness of the resin substrate 12 refers to the total thickness of the resin substrate 12, including the portion in which the internal layer 14b, as a mixed layer 14, is incorporated, even when the internal layer 14b is incorporated into the resin substrate 12.

[0023] From the perspective of making the separator 10 have low resistance, the thickness of the separator 10 is 100 μm or less, preferably 7 to 100 μm, more preferably 7 to 70 μm, and even more preferably 7 to 35 μm.

[0024] The separator 10 preferably has a bubble point measured in accordance with ASTM F316 - 86 of 3.5 MPa or more, more preferably 3.5 to 8.0 MPa, and even more preferably 3.5 to 6.0 MPa. Thus, the separator 10 of the present invention has high gastightness while having low resistance.

[0025] The separator 10 for the alkaline water electrolysis electrode laminate can be incorporated into an electrochemical cell (for example, a cell for a battery and an alkaline water electrolysis cell). Therefore, as shown in FIG. 2, the separator 10 can be incorporated into the alkaline water electrolysis electrode laminate 20. The alkaline water electrolysis electrode laminate 20 can include an anode 22 as an oxygen generation electrode, a cathode 24 as a hydrogen generation electrode, and a separator 10 interposed between the anode 22 and the cathode 24. Since the alkaline water electrolysis electrode laminate 20 having such a configuration uses the separator 10 having low resistance and high gastightness, the energy efficiency can be improved by using the electrode laminate 20 in an alkaline water electrolysis apparatus.

[0026] The electrode laminate 20 preferably has a zero - gap structure in which the anode 22, the separator 10, and the cathode 24 are laminated so as to be in contact with each other. By using such an electrode laminate 20 in an alkaline water electrolysis apparatus, the distance between the electrode and the separator 10 becomes zero, the liquid resistance becomes low, and the power efficiency is also improved, so that efficient hydrogen generation can be realized.

[0027] As shown in the following reaction formulas, in alkaline water electrolysis, at the anode 22 as an oxygen generation electrode, OH － is oxidized to generate O ２ , while at the cathode 24 as a hydrogen generation electrode, H ２ O is reduced to generate H ２ . Anode: 4OH － →O ２ +2H ２ O + 4e － Cathode: 4H２ O+4e － →2H ２ +4OH －

[0028] Therefore, as long as the above reaction occurs in alkaline water electrolysis, the form of the anode 22 and cathode 24 and the materials used are not particularly limited.

[0029] As shown in Figure 3, the diaphragm 10 or the electrode stack 20 for alkaline water electrolysis can be incorporated into the alkaline water electrolysis cell 30. The alkaline water electrolysis cell 30 comprises the electrode stack 20, the electrolyte 32, and the partition wall 34. The partition wall 34 divides the internal space that houses the electrode stack 20 and the electrolyte 32. Because the alkaline water electrolysis cell 30 with this configuration uses a diaphragm 10 that has low resistance and high gastightness, energy efficiency can be improved by using the alkaline water electrolysis cell 30 in an alkaline water electrolysis apparatus.

[0030] Preferably, the alkaline water electrolysis cell 30 is equipped with a sealant (gasket) 36, and the diaphragm 10 is fixed by embedding the end of the diaphragm 10 in the sealant (gasket) 36, and the partition walls 34 are joined together via the sealant (gasket) 36. The sealant (gasket) 36 can be an insulating resin material such as polypropylene, polytetrafluoroethylene, or PFA resin, and is not particularly limited.

[0031] The present invention will be further described in detail by the following examples. However, the present invention is not limited to the following examples.

[0032] Example 1 (1) Preparation of porous resin substrate A commercially available polyethylene microporous membrane with a thickness of 20 μm (porosity: 50%) was prepared as the resin substrate 12 and cut to a size of 5.0 cm × 5.0 cm.

[0033] (2) Formation of the mixed layer Ion-exchanged water in which polyvinyl alcohol (manufactured by Fujifilm Wako Pure Chemical Corporation) as a binder resin was dissolved was mixed with a zirconia dispersion (manufactured by Takaki Chemical Co., Ltd.) containing zirconium oxide (average primary particle size: 20 nm) as inorganic particles. This mixed solution was applied to both sides of the resin substrate 12 and dried to produce a separator 10 in which a pair of mixed layers 14 formed a surface layer 14a on the surface of the resin substrate 12.

[0034] (3) Measurement of the thickness of each layer For the separator 10 (5.0 cm × 5.0 cm) produced in (2) above, the film thickness was measured at five arbitrary positions with a micrometer, and the arithmetic mean value thereof was taken as the thickness (μm) of the separator 10. As a result, the thickness of the separator 10 was 24 μm. Also, since the thickness of the resin substrate 12 in (1) above was 20 μm, the thickness of each layer of the surface layer 14a as the mixed layer 14 was calculated to be 2 μm.

[0035] (4) Measurement of the bubble point The bubble point measurement of the separator 10 produced in (2) above was carried out in accordance with ASTM F316-86 using a gas-liquid porometer (POROLUX Revo) manufactured by Porometer Co., Ltd. Specifically, first, the dried separator 10 was cut out to a size of 25 mm in diameter and placed in a container containing ion-exchanged water. The separator 10 was vacuum-impregnated for 10 minutes by putting this container in a vacuum state. The impregnated separator 10 was set in a sample holder. Then, while increasing the pressure applied to the separator 10, the permeation flow rate was measured, and the pressure at the time when bubbles were generated from the separator 10 was taken as the bubble point (MPa). As a result, in this separator 10, since the permeation flow rate was not measured even when a pressure of 3.5 MPa, which is the measurement upper limit of the apparatus, was applied, the bubble point of the separator 10 was determined to be 3.5 MPa or more. ＴＭ Revo) was used and carried out in accordance with ASTM F316-86. Specifically, first, the dried separator 10 was cut out to a size of diameter 25 mm and placed in a container containing ion-exchanged water. By putting this container in a vacuum state, the separator 10 was vacuum-impregnated for 10 minutes. The impregnated separator 10 was set in a sample holder. Then, while increasing the pressure applied to the separator 10, the permeation flow rate was measured, and the pressure when bubbles were generated from the separator 10 was taken as the bubble point (MPa). As a result, in this separator 10, since the permeation flow rate was not measured even when a pressure of 3.5 MPa, which is the measurement upper limit of the apparatus, was applied, the bubble point of the separator 10 was determined to be 3.5 MPa or more.

[0036] (5) Measurement of Porosity and Maximum Pore Diameter of the Mixed Layer The porosity (%) of the mixed layer 14 and the maximum diameter (maximum pore diameter) (nm) of the pores that may exist in the mixed layer 14 were measured in the diaphragm 10 prepared in (2) above. Specifically, a) the diaphragm 10 was cross-sectionally polished using a cross-section polisher (CP), b) two cross-sectional images of the diaphragm 10 were acquired at a magnification of 100,000x using an FE-SEM (field emission scanning electron microscope), c) the image was binarized using image analysis software (e.g., Image-J) based on the acquired cross-sectional image data, and d) the area of ​​each pore in the mixed layer 14 was determined for each of the two fields. The porosity of the mixed layer 14 in each of the two fields was calculated by dividing the total area of ​​the pores in each field by the area of ​​that field. In addition, the pore diameter of each pore in the mixed layer 14 in each of the two fields was calculated from the area of ​​the pores in each field. The porosity of the mixed layer 14 was defined as the arithmetic mean of the porosities in the two fields of view, and the maximum pore diameter that could exist in the mixed layer 14 was defined as the maximum pore diameter in the two fields of view. As a result, the porosity of the mixed layer 14 was 2%, and the maximum pore diameter was 20 nm.

[0037] (6) Measuring the Resistance of the Diaphragm The resistance of the diaphragm 10 in the electrolyte was measured as follows using the electrochemical measurement system shown in Figure 4. The diaphragm 10 was sandwiched on both sides by 1 mm thick silicone packing 40 and assembled into a PTFE flange-type cell 42 with an inner diameter of 6 mm. As electrodes 46, #100 mesh nickel wire mesh was assembled into the cell 42 in a cylindrical shape with a diameter of 6 mm, so that the distance between electrodes was 2.2 mm. As the electrolyte 44, a 30 wt% KOH aqueous solution was filled into the cell 42. An electrochemical measurement system (potentiometer / galvanostat-frequency response analyzer, Solartron 1287A and 1255B models) was used, and measurements were taken under the conditions of a frequency range of 1 MHz to 0.1 Hz and an applied voltage of 10 mV. The intercept of the real axis was taken as the resistance of the diaphragm 10, and the resistance value (Ω・cm) was calculated. ２ ) was sought.

[0038] Example 2 In (2) above, the resin substrate 12 was vacuum-impregnated with the mixed solution and dried, whereby a diaphragm 10 was produced in which a pair of mixed layers 14 were provided on the surface of the resin substrate 12 to form a surface layer 14a and incorporated into the resin substrate 12 to form an inner layer 14b. In the same manner as in Example 1, except for this, the diaphragm 10 was produced and various measurements were carried out. The results were as shown in Table 1. Further, as shown in FIGS. 5A and 5B, when the cross-section of the diaphragm 10 was observed by FE-SEM (field emission scanning electron microscope) at magnifications of 10,000 times and 50,000 times, respectively, it was confirmed that the diaphragm 10 had a pair of mixed layers 14 provided on the surface of the resin substrate 12 to form a surface layer 14a and incorporated into the resin substrate 12 to form an inner layer 14b.

[0039] Example 3 (Comparison) For comparison, Non-Patent Document 1 (Technical Data Sheet ZIRFON PERL UTP 500, Agfa-Gevaert N.V., May 2020), which is a technical data sheet of Zirfon Perl UTP500 (manufactured by Agfa-Gevaert) having a structure in which a porous film of zirconium oxide (ZrO ２ ) and a polymer is formed on both sides of a polyphenylene sulfide (PPS) mesh, was obtained. According to this technical data sheet, Zirfon Perl UTP500 had a thickness of 500 ± 50 μm, a porosity of 55 ± 10%, a bubble point of 0.2 ± 0.1 MPa, and a resistance value at 30 °C when using a 30% KOH aqueous solution of 0.28 Ω·cm ２ . These values are shown in Table 1.

[0040] Example 4 (Comparison) For comparison, on both sides of a polyphenylene sulfide (PPS) mesh, zirconium oxide (ZrO <Non-patent document 2 (Technical Data Sheet ZIRFON UTP 220, Agfa-Gevaert NV, April 2021) is obtained, which is a technical data sheet for ZIRFON UTP 220 (manufactured by Agfa-Gevaert), which has a structure in which a porous film of polymer is formed. According to this technical data sheet, ZIRFON UTP 220 has a thickness of 220 ± 30 μm, a porosity of 60 ± 10%, a bubble point of 0.2 ± 0.1 MPa, and a resistance of 0.10 Ω·cm at 30°C when using a 30% KOH aqueous solution. ２ These values ​​are shown in Table 1.

[0041]

[0042] 10: Diaphragm, 12: Resin substrate, 14: Mixed layer, 14a: Surface layer, 14b: Inner layer, 20: Alkaline water electrolysis electrode laminate, 22: Anode, 24: Cathode, 30: Alkaline water electrolysis cell, 32: Electrolyte, 34: Diaphragm, 40: Silicone packing, 42: Flange-type cell, 44: Electrolyte, 46: Electrode

Claims

1. A diaphragm used in an electrochemical cell, comprising: a porous resin substrate; and a pair of mixed layers provided on both sides of the resin substrate, each of which is provided so as to form a surface layer on the surface of the resin substrate and / or incorporated so as to form an internal layer inside the resin substrate, wherein the maximum diameter of pores that may exist in the mixed layers is 40 nm or less, and the thickness of the diaphragm is 100 μm or less.

2. The diaphragm according to claim 1, wherein the porosity of the mixed layer is 30% or less.

3. The diaphragm according to claim 1, wherein the mixed layer includes the surface layer, and the thickness of each layer of the surface layer is 15 μm or less.

4. The diaphragm according to claim 1, wherein the average primary particle size of the inorganic particles is 30 nm or less.

5. The diaphragm according to claim 1, wherein the inorganic particles include at least one selected from the group consisting of zirconium oxide, titanium oxide, and rare earth oxide.

6. The diaphragm according to claim 1, wherein the binder resin comprises at least one selected from the group consisting of polyvinyl alcohol, polyethylene, polypropylene, and polysulfone.

7. The diaphragm according to claim 1, wherein the portion of the resin substrate other than the inner layer has a porosity of 25 to 75%.

8. The diaphragm according to claim 1, wherein the resin substrate comprises at least one selected from the group consisting of polyethylene, polypropylene, polysulfone, polyphenylene sulfide, polyetheretherketone, and polymethylpentene.

9. The diaphragm according to claim 1, wherein the thickness of the resin substrate is 5 to 70 μm.

10. The diaphragm according to claim 1, wherein the thickness of the diaphragm is 7 to 100 μm.

11. The diaphragm according to claim 1, wherein the bubble point measured in accordance with ASTM F316-86 is 3.5 MPa or higher.

12. An electrode laminate for alkaline water electrolysis, comprising: an anode as an oxygen-evolving electrode; a cathode as a hydrogen-evolving electrode; and a diaphragm according to any one of claims 1 to 11, interposed between the anode and the cathode.

13. The electrode laminate for alkaline water electrolysis according to claim 12, wherein the electrode laminate has a zero-gap structure in which the anode, the diaphragm and the cathode are laminated in contact with each other.

14. An alkaline water electrolysis cell comprising: an electrode laminate for alkaline water electrolysis according to claim 12; an electrolyte; and a partition wall that divides the internal space containing the electrode laminate and the electrolyte.

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