Preparation method of ion exchange membrane with gradient ionic conductivity

Abstract

The invention relates to the technical field of new materials, in particular to a preparation method of an ion exchange membrane with gradient ionic conductivity. Two ionic conduction polymers A and B are selected, and the ionic conductivity of the polymer A is higher than that of the polymer B; respectively dissolving the polymer A and the polymer B in a solvent to form a membrane preparation solution; respectively pouring the membrane preparation liquid into culture dishes, and evaporating the solvent to basically form an initial membrane which still contains a certain amount of solvent; adhering one initial membrane of the polymer A and one initial membrane of the polymer B with the same shape and area up and down, putting into a new culture dish with the same shape and area, completely evaporating the solvent, and interpenetrating and fusing the two initial membranes to obtain an integral membrane; and acidifying or alkalizing the whole membrane to obtain the ion exchange membrane with gradient change ion conductivity in the permeation surface direction. Under the condition that the total raw materials for preparing the membrane are not changed, the limitation of isotropic conductivity of a traditional ion exchange membrane can be broken through, and the conduction advantage of single starting point-end point pointing in the direction of a permeation surface is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and particularly relates to a preparation method of an ion exchange membrane with gradient ionic conductivity. Background Art

[0002] Ion exchange membranes are key materials in clean energy or new energy storage fields such as fuel cells, water electrolyzers, carbon dioxide electrolyzers, and flow batteries. In actual electrochemical energy conversion devices in these application fields, the ion exchange membrane is located between the two electrodes on both sides. Ions need to cross the membrane in the through-plane direction (i.e., the thickness direction, the through-plane direction) of the ion exchange membrane and conduct across the membrane from one electrode to the other electrode. At the same time, this through-plane direction transmembrane conduction has the requirement of a single starting point - ending point direction in actual needs. For example, in an acidic fuel cell, hydrogen ions need to start from the anode and conduct across the membrane to the cathode as the ending point to achieve energy conversion, while the reverse transmembrane conduction of hydrogen ions from the cathode to the anode is ineffective; in an alkaline fuel cell, hydroxide ions need to start from the cathode and conduct across the membrane to the anode as the ending point to achieve energy conversion, while the reverse transmembrane conduction of hydroxide ions from the anode to the cathode is ineffective.

[0003] Ion exchange membranes prepared by general film preparation methods (such as solution casting) usually have an isotropic conduction structure and it is difficult to achieve rapid transmembrane conduction of ions in the through-plane direction. Although some reports have used auxiliary means such as electric fields and magnetic fields to construct an oriented conduction structure in the through-plane direction of the ion exchange membrane, which is beneficial to improving the ion transmembrane conduction efficiency, the single starting point - ending point direction ion conduction required in actual needs has not received extensive attention and in-depth research. In particular, it should be pointed out that the single starting point - ending point direction required for ion conduction in electrochemical devices is usually opposite to the direction of water molecule diffusion caused by the water content difference between the two electrodes on both sides. For example, in an acidic fuel cell, the diffusion of water molecules is from the cathode to the anode, and in an alkaline fuel cell, the diffusion of water molecules is from the anode to the cathode. The reverse diffusion of water molecules will carry ions to conduct in the opposite direction to the single starting point - ending point direction required in actual needs, which is ineffective. If only an oriented structure in the through-plane direction is constructed, it will make the reverse diffusion of water molecules and the carried ions easier, and to a certain extent, weaken the conduction of ions in the single starting point - ending point direction required in actual needs.

[0004] There is an urgent need in this field to develop an ion exchange membrane with the conduction advantage of a single starting point - ending point direction in the through-plane direction to further improve the performance of electrochemical energy conversion devices. Summary of the Invention

[0005] In order to achieve the above object, the present invention provides a preparation method of an ion exchange membrane with gradient ionic conductivity:

[0006] As a preferred technical solution of the present invention, S1: Select two ion-conducting polymers, the ion-conducting polymers include polymer A and polymer B, and the ionic conductivity of polymer A is higher than that of polymer B;

[0007] S2: Dissolve polymer A and polymer B in solvent A and solvent B respectively. After polymer A is fully dissolved in solvent A, a film-forming solution A is obtained. After polymer B is fully dissolved in solvent B, a film-forming solution B is obtained;

[0008] S3: Pour the film-forming solution A into petri dish A and the film-forming solution B into petri dish B. After evaporating part of solvent A and part of solvent B, the film-forming solution A is shaped into an initial film A in petri dish A, and the film-forming solution B is shaped into an initial film B in petri dish B;

[0009] S4: Select one piece each of the initial film A and the initial film B with the same shape and area, and laminate them up and down in petri dish C. The shape and area of petri dish C are the same as those of the initial film A and the initial film B selected in this step. Completely evaporate solvent A and solvent B in petri dish C to obtain an integral film;

[0010] S5: Perform acidification or alkalization treatment on the integral film to obtain an ion exchange membrane with a gradient change in ionic conductivity in the direction of the permeation surface.

[0011] As a preferred technical solution of the present invention, the ion-conducting groups of polymer A and polymer B are one of sulfonic acid group, carboxylic acid group, phosphonic acid group, hydroxyl group, ferrocyanide ligand, quaternary amine group, guanidine group, quaternary phosphonium group, tertiary sulfonium group, ferrocene salt group, and cobaltocene salt group.

[0012] As a preferred technical solution of the present invention, the main chains of polymer A and polymer B are one of polyperfluoroethylene, polyvinylidene fluoride, polystyrene, polystyrene, polyvinylpyridine, polyethylene, polysulfone, polyethersulfone, polyetheretherketone, polyphenylene ether, polybiphenyl, and polynorbornene.

[0013] As a preferred technical solution of the present invention, solvent A and solvent B are one of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and m-cresol.

[0014] As a preferred technical solution of the present invention, the content of the remaining solvent A in the initial film A in petri dish A is 10% - 200% of the mass of the polymer in the initial film A; the content of the remaining solvent B in the initial film B in petri dish B is 10% - 200% of the mass of the polymer in the initial film B.

[0015] As a preferred technical solution of the present invention, the temperature required for evaporating part of the solvent A and part of the solvent B is 60°C to 120°C.

[0016] As a preferred technical solution of the present invention, the temperature required for completely evaporating the solvent A and the solvent B in the petri dish C is 60°C to 120°C.

[0017] As a preferred technical solution of the present invention, the mass ratio of the polymer A to the polymer B in the initial film A and the initial film B with the same shape and area is 10:90 to 90:10.

[0018] Compared with the prior art, the present invention provides a method for preparing an ion exchange membrane with a gradient ionic conductivity, having the following beneficial effects: Compared with the general film-making method, the present invention first prepares two initial films containing a certain amount of solvent, that is, the polymer molecular chains in the initial film maintain a certain movement ability and shape plasticity, and then uses the two initial films to penetrate and fuse with each other to obtain an overall film treatment technology. Without changing the total raw materials for film-making, it can break through the limitation of the isotropic conductivity of traditional ion exchange membranes, construct a gradient interpenetrating structure of two components, polymer A and polymer B, in the overall film, obtain an ion exchange membrane with a gradient change in ionic conductivity in the through-plane direction, realize the ion conduction advantage of a single starting point - end point direction in the through-plane direction, and further improve the performance of the electrochemical energy conversion device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the method steps of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0021] A method for preparing an ion exchange membrane with a gradient ionic conductivity, the implementation steps of the method are as follows:

[0022] S1: Select two ion-conducting polymers, the ion-conducting polymers include polymer A and polymer B, and the ionic conductivity of polymer A is higher than that of polymer B;

[0023] S2: Dissolve the polymer A and the polymer B in the solvent A and the solvent B respectively. After the polymer A is fully dissolved in the solvent A, a film-forming solution A is obtained, and after the polymer B is fully dissolved in the solvent B, a film-forming solution B is obtained;

[0024] S3: Pour the film-forming solution A into Petri dish A and the film-forming solution B into Petri dish B. After evaporating part of the solvent A and part of the solvent B, the film-forming solution A is shaped into the initial film A in Petri dish A, and the film-forming solution B is shaped into the initial film B in Petri dish B;

[0025] S4: Select one piece each of the initial film A and the initial film B with the same shape and area, and stack them together in Petri dish C. The shape and area of Petri dish C are the same as those of the initial film A and the initial film B selected in this step. Completely evaporate the solvent A and the solvent B in Petri dish C to obtain the integral film;

[0026] S5: Perform acidification or alkalization treatment on the integral film to obtain an ion exchange membrane with a gradient change in ionic conductivity in the direction of the permeable surface.

[0027] Table 1. Comparison of the conductivity of the polymers used in the examples and comparative examples and the fuel cell power density of the prepared membranes

[0028]

[0029] Example 1:

[0030] As shown in Table 1, select perfluorinated ethylene with sulfonic acid groups and polyvinylidene fluoride with carboxylic acid groups;

[0031] Dissolve perfluorinated ethylene with sulfonic acid groups and polyvinylidene fluoride with carboxylic acid groups in solvents dimethylformamide and dimethylacetamide respectively. After complete dissolution, perform vacuum degassing to form two film-forming solutions;

[0032] Pour the two film-forming solutions into two Petri dishes respectively, and evaporate the solvents at a temperature of 80 °C so that the two film-forming solutions are basically shaped into the initial films. The two initial films in these two Petri dishes still contain a certain amount of solvent, and the remaining solvent amounts are obtained by weighing and calculating the film-forming raw materials, solvents, film-forming Petri dishes, and film-forming solutions during the film-forming process. The contents are 80% and 70% of the polymer mass in the initial films respectively;

[0033] Remove the above two initial films from the Petri dishes, select one piece each of the initial films of perfluorinated ethylene with sulfonic acid groups and polyvinylidene fluoride with carboxylic acid groups with the same shape and area, stack them together, with the mass ratio of perfluorinated ethylene with sulfonic acid groups to polyvinylidene fluoride with carboxylic acid groups in the initial film being 10:90, put them into a Petri dish with the same shape and area as the stacked film, and evaporate the remaining solvent at a temperature of 80 °C. During this process, the two initial films penetrate and fuse with each other to obtain the integral film;

[0034] By subjecting the overall membrane to acidification treatment, an ion exchange membrane with a gradient change in ionic conductivity in the through-plane direction can be obtained. The gradient change in ionic conductivity in the through-plane direction gradually increases from the side of the initial membrane of polyvinylidene fluoride with carboxyl groups to the side of the initial membrane of perfluorinated ethylene with sulfonic groups, thus achieving the ionic conduction advantage from the side of the initial membrane of polyvinylidene fluoride with carboxyl groups to the side of the initial membrane of perfluorinated ethylene with sulfonic groups in the through-plane direction.

[0035] The ion exchange membrane prepared in Example 1 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane of polyvinylidene fluoride with carboxyl groups was in contact with the anode gas diffusion electrode and the side of the initial membrane of perfluorinated ethylene with sulfonic groups was in contact with the cathode gas diffusion electrode, the peak power density was 818 ; when the side of the initial membrane of polyvinylidene fluoride with carboxyl groups was in contact with the cathode gas diffusion electrode and the side of the initial membrane of perfluorinated ethylene with sulfonic groups was in contact with the anode gas diffusion electrode, the peak power density was 604 . The ratio of the differences in the performance directions of the fuel cells obtained by calculating the proton unidirectional conductivity by dividing the two was approximately 1.35.

[0036] Comparative Example 1:

[0037] Perfluorinated ethylene with sulfonic groups and polyvinylidene fluoride with carboxyl groups were selected;

[0038] Perfluorinated ethylene with sulfonic groups and polyvinylidene fluoride with carboxyl groups were respectively dissolved in solvents dimethylformamide and dimethylacetamide. After complete dissolution, degassing under vacuum was performed to form two film-forming solutions;

[0039] The above two film-forming solutions were thoroughly mixed and poured into a petri dish. The mass ratio of perfluorinated ethylene with sulfonic groups to polyvinylidene fluoride with carboxyl groups was 10:90. The solvent was evaporated at a temperature of 80 °C until the solvent was completely evaporated to obtain a conventional membrane;

[0040] The conventional membrane was subjected to acidification treatment to obtain a conventional ion exchange membrane.

[0041] The ion exchange membrane prepared in Comparative Example 1 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the two sides of the membrane interchanged, the peak power densities were 712 and 709 , being basically the same, indicating that there is basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane of Example 1 when assembling the fuel cell in the direction of the proton unidirectional conduction advantage is 818 , compared with the peak power density of the fuel cell of the ion exchange membrane of Comparative Example 1 which is 709 - 712 is increased by about 15%.

[0042] Example 2:

[0043] As shown in Table 1, polystyrene with phosphonic acid groups and polystyrene with hydroxyl groups are selected;

[0044] The polystyrene with phosphonic acid groups and the polystyrene with hydroxyl groups are respectively dissolved in solvents dimethyl sulfoxide and dimethylformamide. After being fully dissolved, they are degassed under vacuum to form two film-forming solutions;

[0045] The two film-forming solutions are respectively poured into two petri dishes, and the solvents are evaporated at a temperature of 120 °C, so that the two film-forming solutions are basically shaped into initial films. The two initial films in these two petri dishes still contain a certain amount of solvent, and the remaining solvent amounts are obtained by weighing and calculating the film-forming raw materials, solvents, film-forming petri dishes, and film-forming solutions during the film-forming process, and the contents are 10% and 200% of the polymer mass in the initial films respectively;

[0046] The above two initial films are taken off from the petri dishes, and one piece of the initial film of polystyrene with phosphonic acid groups and one piece of the initial film of polystyrene with hydroxyl groups with the same shape and area are laminated up and down. The mass ratio of the polystyrene with phosphonic acid groups to the polystyrene with hydroxyl groups in the initial film is 75:25, and they are put into a petri dish with the same shape and area as the laminated film, and the remaining solvent is evaporated at a temperature of 120 °C. During this process, the two initial films penetrate and fuse with each other to obtain an integral film;

[0047] The integral film is acidified to obtain an ion exchange membrane with a gradient change in ionic conductivity in the direction of the permeation surface. The gradient change in the ionic conductivity in the direction of the permeation surface gradually increases from the side of the initial film of polystyrene with hydroxyl groups to the side of the initial film of polystyrene with phosphonic acid groups, so as to achieve the ionic conduction advantage from the side of the initial film of polystyrene with hydroxyl groups to the side of the initial film of polystyrene with phosphonic acid groups in the direction of the permeation surface.

[0048] The ion exchange membrane prepared in Example 2 is assembled with a gas diffusion electrode, and the polarization curve is tested and the power density is calculated by connecting to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , and the test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial film of polystyrene with hydroxyl groups contacts the anode gas diffusion electrode and the side of the initial film of polystyrene with phosphonic acid groups contacts the cathode gas diffusion electrode, the peak power density is 913 ; When one side of the initial polystyrene film with hydroxyl groups contacts the cathode gas diffusion electrode and one side of the initial polystyrene film with phosphonic acid groups contacts the anode gas diffusion electrode, the peak power density is 567 . The ratio of the difference in the performance direction of the fuel cell obtained by dividing the proton unidirectional conductivity is approximately 1.61.

[0049] Comparative Example 2:

[0050] Select polystyrene with phosphonic acid groups and polystyrene with hydroxyl groups;

[0051] Dissolve polystyrene with phosphonic acid groups and polystyrene with hydroxyl groups in solvents dimethyl sulfoxide and dimethylformamide respectively. After complete dissolution, vacuum degas to form two film-forming solutions;

[0052] Fully mix the above two film-forming solutions evenly and pour them into a petri dish. The mass ratio of polystyrene with phosphonic acid groups to polystyrene with hydroxyl groups is 75:25. Evaporate the solvent at a temperature of 120 °C until the solvent is completely evaporated to obtain a conventional membrane;

[0053] Perform acidification treatment on the conventional membrane to obtain a conventional ion exchange membrane.

[0054] Assemble the ion exchange membrane prepared in Comparative Example 2 with the gas diffusion electrode, connect it to a hydrogen-oxygen fuel cell to test the polarization curve and calculate the power density. The same gas diffusion layer and catalytic layer are used for the cathode and anode gas diffusion electrodes, and the catalyst loading is 0.3 , The test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the cathode and anode are assembled with the two sides of the membrane interchanged, the peak power densities are 734 and 729 , which are basically the same, indicating that there is basically no difference in the conduction directionality of the membrane. The peak power density of the fuel cell with the ion exchange membrane of Example 2 assembled in the direction of the proton unidirectional conduction advantage is 913 , which is about 25% higher than the peak power density of the fuel cell with the ion exchange membrane of Comparative Example 2, which is 729 - 734 .

[0055] Example 3:

[0056] As shown in Table 1, select polyethylene with sulfonic acid groups and polysulfone with carboxylic acid groups;

[0057] Dissolve polyethylene with sulfonic acid groups and polysulfone with carboxylic acid groups in solvents dimethylformamide and dimethylacetamide respectively. After complete dissolution, vacuum degas to form two film-forming solutions;

[0058] Pour the two film-forming solutions into two petri dishes respectively, and evaporate the solvent at a temperature of 110 °C to make the two film-forming solutions basically take shape into initial films. The two initial films in the two petri dishes still contain a certain amount of solvent, and the remaining solvent amounts are obtained by weighing and calculating the film-forming raw materials, solvents, film-forming petri dishes, and film-forming solutions during the film-forming process, and the contents are 25% and 140% of the polymer mass in the initial films respectively;

[0059] Remove the above two initial films from the petri dishes, select one piece of the initial film of polyethylene with sulfonic acid groups and one piece of the initial film of polysulfone with carboxylic acid groups with the same shape and area, and bond them together. The mass ratio of polyethylene with sulfonic acid groups to polysulfone with carboxylic acid groups in the initial film is 30:70, and put them into a petri dish with the same shape, area as the bonded film, and evaporate the remaining solvent at a temperature of 110 °C. During this process, the two initial films penetrate and fuse with each other to obtain an integral film;

[0060] Perform acidification treatment on the integral film to obtain an ion exchange membrane with a gradient change in ionic conductivity in the direction of the permeation surface. The gradient change in ionic conductivity in the direction of the permeation surface gradually increases from the side of the initial film of polysulfone with carboxylic acid groups to the side of the initial film of polyethylene with sulfonic acid groups, and the ionic conduction advantage from the side of the initial film of polysulfone with carboxylic acid groups to the side of the initial film of polyethylene with sulfonic acid groups in the direction of the permeation surface can be realized.

[0061] The ion exchange membrane prepared in Example 3 is assembled with a gas diffusion electrode, and the polarization curve is measured and the power density is calculated when connected to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , and the test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial film of polysulfone with carboxylic acid groups contacts the anode gas diffusion electrode and the side of the initial film of polyethylene with sulfonic acid groups contacts the cathode gas diffusion electrode, the peak power density is 1395 ; when the side of the initial film of polysulfone with carboxylic acid groups contacts the cathode gas diffusion electrode and the side of the initial film of polyethylene with sulfonic acid groups contacts the anode gas diffusion electrode, the peak power density is 817 . Divide the two to calculate the difference ratio of the fuel cell performance obtained from the proton unidirectional conductivity, which is about 1.71.

[0062] Comparative Example 3:

[0063] Select polyethylene with sulfonic acid groups and polysulfone with carboxylic acid groups;

[0064] Dissolve polyethylene with sulfonic acid groups and polysulfone with carboxylic acid groups in solvents dimethylformamide and dimethylacetamide respectively, and form two film-forming solutions after fully dissolving and degassing under vacuum;

[0065] Fully mix the above two film-forming solutions evenly and pour them into a petri dish. The mass ratio of the polyethylene with sulfonic acid groups to the polysulfone with carboxylic acid groups is 30:70. Evaporate the solvent at a temperature of 110 °C until the solvent is completely evaporated to obtain a conventional membrane;

[0066] Perform acidification treatment on the conventional membrane to obtain a conventional ion exchange membrane.

[0067] Assemble the ion exchange membrane prepared in Comparative Example 3 with a gas diffusion electrode, connect it to a hydrogen-oxygen fuel cell to test the polarization curve and calculate the power density. The same gas diffusion layer and catalyst layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , and the test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode are assembled with the two sides of the membrane swapped, the peak power densities are 1109 and 1093 , which are basically the same, indicating that there is basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane in Example 3 when assembled in the proton unidirectional conduction dominant direction is 1395 , compared with the peak power density of the fuel cell of the ion exchange membrane in Comparative Example 3, which is 1093 - 1109 is increased by about 27%.

[0068] Example 4:

[0069] As shown in Table 1, select polyvinylpyridine with ferrocyanide coordination groups and polyethersulfone with phosphonic acid groups;

[0070] Dissolve polyvinylpyridine with ferrocyanide coordination groups and polyethersulfone with phosphonic acid groups in solvents dimethylformamide and dimethylacetamide respectively. After complete dissolution, perform vacuum degassing to form two film-forming solutions;

[0071] Pour the two film-forming solutions into two petri dishes respectively, and evaporate the solvent at a temperature of 90 °C to make the two film-forming solutions basically take shape into initial membranes. The two initial membranes in these two petri dishes still contain a certain amount of solvent, and the remaining solvent amounts are obtained by weighing and calculating the film-forming raw materials, solvents, film-forming petri dishes, and film-forming solutions during the film-forming process, and the contents are 120% and 45% of the polymer mass in the initial membranes respectively;

[0072] Remove the above two initial membranes from the petri dishes, select one piece each of the initial membranes of polyvinylpyridine with ferrocyanide coordination groups and polyethersulfone with phosphonic acid groups with the same shape and area, and laminate them together. The mass ratio of polyvinylpyridine with ferrocyanide coordination groups to polyethersulfone with phosphonic acid groups in the initial membrane is 70:30. Place them in a petri dish with the same shape, area as the laminated membrane, and evaporate the remaining solvent at a temperature of 90 °C. During this process, the two initial membranes penetrate and fuse with each other to obtain an integral membrane;

[0073] By subjecting the overall membrane to acidification treatment, an ion exchange membrane with a gradient change in ionic conductivity in the direction of the permeation surface can be obtained. The gradient change in ionic conductivity in the direction of the permeation surface gradually increases from the initial membrane side of the polyethersulfone with phosphonic acid groups to the initial membrane side of the polyvinylpyridine with ferrocyanide coordination groups, thereby achieving the ionic conduction advantage from the initial membrane side of the polyethersulfone with phosphonic acid groups to the initial membrane side of the polyvinylpyridine with ferrocyanide coordination groups in the direction of the permeation surface.

[0074] The ion exchange membrane prepared in Example 4 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the initial membrane side of the polyethersulfone with phosphonic acid groups was in contact with the anode gas diffusion electrode and the initial membrane side of the polyvinylpyridine with ferrocyanide coordination groups was in contact with the cathode gas diffusion electrode, the peak power density was 1137 ; when the initial membrane side of the polyethersulfone with phosphonic acid groups was in contact with the cathode gas diffusion electrode and the initial membrane side of the polyvinylpyridine with ferrocyanide coordination groups was in contact with the anode gas diffusion electrode, the peak power density was 729 . The ratio of the performance direction differences of the fuel cells obtained by calculating the proton unidirectional conductivity by dividing the two was approximately 1.56.

[0075] Comparative Example 4:

[0076] Polyvinylpyridine with ferrocyanide coordination groups and polyethersulfone with phosphonic acid groups were selected;

[0077] Polyvinylpyridine with ferrocyanide coordination groups and polyethersulfone with phosphonic acid groups were respectively dissolved in solvents dimethylformamide and dimethylacetamide. After complete dissolution, degassing under vacuum was carried out to form two casting solutions;

[0078] The above two casting solutions were thoroughly mixed and poured into a petri dish. The mass ratio of polyvinylpyridine with ferrocyanide coordination groups to polyethersulfone with phosphonic acid groups was 70:30. The solvent was evaporated at a temperature of 90 °C until the solvent was completely evaporated to obtain a conventional membrane;

[0079] By subjecting the conventional membrane to acidification treatment, a conventional ion exchange membrane can be obtained.

[0080] The ion exchange membrane prepared in Comparative Example 4 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the two sides of the membrane interchanged, the peak power densities were 919 and 925 , being basically the same, indicating that there is basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane in Example 4 when assembling the fuel cell in the proton unidirectional conduction advantageous direction is 1137 , compared with the peak power density of the fuel cell with the ion exchange membrane in Comparative Example 4, which is 919 - 925 is increased by about 23%.

[0081] Example 5:

[0082] As shown in Table 1, polyethylene with hydroxyl groups and polyvinylpyridine with ferrocyanide ligands are selected;

[0083] The polyethylene with hydroxyl groups and the polyvinylpyridine with ferrocyanide ligands are respectively dissolved in solvents N - methylpyrrolidone and dimethyl sulfoxide. After being fully dissolved, they are degassed under vacuum to form two film - forming solutions;

[0084] The two film - forming solutions are respectively poured into two petri dishes, and the solvents are evaporated at a temperature of 80 °C, so that the two film - forming solutions are basically shaped into initial films. The two initial films in these two petri dishes still contain a certain amount of solvent, and the remaining solvent amounts are obtained by weighing and calculating the film - forming raw materials, solvents, film - forming petri dishes, and film - forming solutions during the film - forming process, and the contents are 65% and 90% of the polymer mass in the initial films respectively;

[0085] The above - mentioned two initial films are taken off from the petri dishes, and one piece of the initial film of polyethylene with hydroxyl groups and one piece of the initial film of polyvinylpyridine with ferrocyanide ligands with the same shape and area are selected and laminated together. The mass ratio of polyethylene with hydroxyl groups to polyvinylpyridine with ferrocyanide ligands in the initial film is 15:85, and they are put into a petri dish with the same shape, area as the laminated film, and the remaining solvent is evaporated at a temperature of 80 °C. During this process, the two initial films penetrate and fuse with each other to obtain an integral film;

[0086] The integral film is subjected to acidification treatment, and an ion exchange membrane with a gradient change in ionic conductivity in the through - surface direction can be obtained. The gradient change in ionic conductivity in the through - surface direction gradually increases from the side of the initial film of polyvinylpyridine with ferrocyanide ligands to the side of the initial film of polyethylene with hydroxyl groups, and thus the ionic conduction advantage from the side of the initial film of polyvinylpyridine with ferrocyanide ligands to the side of the initial film of polyethylene with hydroxyl groups in the through - surface direction can be realized.

[0087] The ion exchange membrane prepared in Example 5 is assembled with a gas diffusion electrode, and the polarization curve is tested and the power density is calculated by connecting it to a hydrogen - oxygen fuel cell. The same gas diffusion layer and catalytic layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , the test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial film of polyvinylpyridine with a ferrocyanide ligand contacts the anode gas diffusion electrode and the side of the initial film of polyethylene with a hydroxyl group contacts the cathode gas diffusion electrode, the peak power density is 251 ; when the side of the initial film of polyvinylpyridine with a ferrocyanide ligand contacts the cathode gas diffusion electrode and the side of the initial film of polyethylene with a hydroxyl group contacts the anode gas diffusion electrode, the peak power density is 189 . The ratio of the difference in the performance direction of the fuel cell obtained by calculating the proton unidirectional conductivity by dividing the two is about 1.33

[0088] Comparative Example 5:

[0089] Select polyethylene with a hydroxyl group and polyvinylpyridine with a ferrocyanide ligand;

[0090] Dissolve polyethylene with a hydroxyl group and polyvinylpyridine with a ferrocyanide ligand in solvents N-methylpyrrolidone and dimethyl sulfoxide respectively. After complete dissolution, degas under vacuum to form two film-forming solutions;

[0091] Fully mix the above two film-forming solutions and pour them into a petri dish. The mass ratio of polyethylene with a hydroxyl group to polyvinylpyridine with a ferrocyanide ligand is 15:85. Evaporate the solvent at 80 °C until the solvent is completely evaporated to obtain a conventional membrane;

[0092] Perform acidification treatment on the conventional membrane to obtain a conventional ion exchange membrane.

[0093] Assemble the ion exchange membrane prepared in Comparative Example 5 with the gas diffusion electrode, connect it to a hydrogen-oxygen fuel cell to test the polarization curve and calculate the power density. The same gas diffusion layer and catalytic layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , the test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode are assembled with the two sides of the membrane interchanged, the peak power densities are 213 and 214 , which are basically the same, indicating that there is basically no difference in the conduction directionality of the membrane. The peak power density of the fuel cell with the ion exchange membrane of Example 5 assembled in the direction of the proton unidirectional conduction advantage is 251 , compared with the peak power density of the fuel cell with the ion exchange membrane of Comparative Example 5, which is 213-214 is increased by about 17%.

[0094] Example 6:

[0095] As shown in Table 1, select perfluorinated ethylene sulfonate and polyvinylidene fluoride sulfonate;

[0096] Perfluorinated ethylene polymer with sulfonic acid groups and polyvinylidene fluoride with sulfonic acid groups are separately dissolved in solvents dimethyl sulfoxide and dimethylformamide. After complete dissolution, they are degassed under vacuum to form two casting solutions.

[0097] The two casting solutions are separately poured into two petri dishes. The solvents are evaporated at a temperature of 120 °C, causing the two casting solutions to basically solidify into initial membranes. The two initial membranes in the two petri dishes still contain a certain amount of solvent, and the remaining solvent amounts are obtained through weighing and calculation during the film-forming process of the film-forming raw materials, solvents, film-forming petri dishes, and casting solutions, and the contents are 45% and 170% of the polymer mass in the initial membranes, respectively.

[0098] The above two initial membranes are removed from the petri dishes. One piece of perfluorinated ethylene polymer with sulfonic acid groups and one piece of polyvinylidene fluoride with sulfonic acid groups with the same shape and area are selected and laminated together. The mass ratio of perfluorinated ethylene polymer with sulfonic acid groups to polyvinylidene fluoride with sulfonic acid groups in the initial membranes is 50:50. They are placed in a petri dish with the same shape and area as the laminated membrane, and the remaining solvents are evaporated at a temperature of 120 °C. During this process, the two initial membranes penetrate and fuse with each other to obtain an integral membrane.

[0099] The integral membrane is subjected to acidification treatment to obtain an ion exchange membrane with a gradient change in ionic conductivity in the through-plane direction. The gradient change in ionic conductivity in the through-plane direction gradually increases from the side of the initial membrane of polyvinylidene fluoride with sulfonic acid groups to the side of the initial membrane of perfluorinated ethylene polymer with sulfonic acid groups, thus realizing the ionic conduction advantage from the side of the initial membrane of polyvinylidene fluoride with sulfonic acid groups to the side of the initial membrane of perfluorinated ethylene polymer with sulfonic acid groups in the through-plane direction.

[0100] The ion exchange membrane prepared in Example 6 is assembled with a gas diffusion electrode, and the polarization curve is measured and the power density is calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , and the test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane of polyvinylidene fluoride with sulfonic acid groups contacts the anode gas diffusion electrode and the side of the initial membrane of perfluorinated ethylene polymer with sulfonic acid groups contacts the cathode gas diffusion electrode, the peak power density is 3592 ; when the side of the initial membrane of polyvinylidene fluoride with sulfonic acid groups contacts the cathode gas diffusion electrode and the side of the initial membrane of perfluorinated ethylene polymer with sulfonic acid groups contacts the anode gas diffusion electrode, the peak power density is 1327 . The ratio of the performance direction differences of the fuel cells obtained by calculating the proton unidirectional conductivity by dividing the two is approximately 2.71.

[0101] Comparative Example 6:

[0102] Perfluorinated ethylene polymer with sulfonic acid groups and polyvinylidene fluoride with sulfonic acid groups are selected.

[0103] Perfluorinated ethylene sulfonic acid and polyvinylidene fluoride sulfonic acid were respectively dissolved in solvents dimethyl sulfoxide and dimethylformamide. After complete dissolution, degassing under vacuum was carried out to form two casting solutions.

[0104] The above two casting solutions were fully mixed and poured into a petri dish. The mass ratio of polyethylene with hydroxyl groups to polyvinylpyridine with ferrocyanide ligands was 50:50. The solvent was evaporated at a temperature of 120 °C until the solvent was completely evaporated, obtaining a conventional membrane.

[0105] The conventional membrane was subjected to acidification treatment to obtain a conventional ion exchange membrane.

[0106] The ion exchange membrane prepared in Comparative Example 6 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated for a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 . The test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the membrane sides swapped, the peak power densities were 2422 and 2398 , which were basically the same, indicating that there was basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane in Example 6 when assembled in the proton unidirectional conduction dominant direction for the fuel cell was 3592 , compared with the peak power density of the fuel cell of the ion exchange membrane in Comparative Example 6, which was 2398 - 2422 was increased by about 49%.

[0107] Example 7:

[0108] As shown in Table 1, polystyrene 1 with carboxyl groups and polystyrene 2 with carboxyl groups were selected;

[0109] Polystyrene 1 with carboxyl groups and polystyrene 2 with carboxyl groups were respectively dissolved in solvents N-methylpyrrolidone and dimethyl sulfoxide. After complete dissolution, degassing under vacuum was carried out to form two casting solutions;

[0110] The two casting solutions were respectively poured into two petri dishes, and the solvent was evaporated at a temperature of 110 °C until the two casting solutions were basically shaped into initial membranes. The two initial membranes in the two petri dishes still contained a certain amount of solvent, and the remaining solvent amounts were obtained by weighing and calculating during the film-forming process of the film-forming raw materials, solvents, film-forming petri dishes, and casting solutions, and the contents were 85% and 110% of the polymer mass in the initial membranes respectively;

[0111] Remove the above two initial membranes from the culture dish. Select one piece of the initial membrane of polybenzene 1 with carboxyl groups and one piece of the initial membrane of polybenzene 2 with carboxyl groups that have the same shape and area, and stack them together. The mass ratio of polybenzene 1 with carboxyl groups to polybenzene 2 with carboxyl groups in the initial membrane is 35:65. Place them in a culture dish with the same shape and area as the stacked membrane, and evaporate the remaining solvent at a temperature of 110 °C. During this process, the two initial membranes penetrate and fuse with each other to obtain an integral membrane;

[0112] Perform acidification treatment on the integral membrane to obtain an ion exchange membrane with a gradient change in ionic conductivity in the through-plane direction. The gradient change in ionic conductivity in the through-plane direction gradually increases from the side of the initial membrane of polybenzene 2 with carboxyl groups to the side of the initial membrane of polybenzene 1 with carboxyl groups, thus realizing the ionic conduction advantage from the side of the initial membrane of polybenzene 2 with carboxyl groups to the side of the initial membrane of polybenzene 1 with carboxyl groups in the through-plane direction.

[0113] The ion exchange membrane prepared in Example 7 is assembled with a gas diffusion electrode, and the polarization curve is measured and the power density is calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 Under the test conditions of 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane of polybenzene 2 with carboxyl groups contacts the anode gas diffusion electrode and the side of the initial membrane of polybenzene 1 with carboxyl groups contacts the cathode gas diffusion electrode, the peak power density is 1269 ; when the side of the initial membrane of polybenzene 2 with carboxyl groups contacts the cathode gas diffusion electrode and the side of the initial membrane of polybenzene 1 with carboxyl groups contacts the anode gas diffusion electrode, the peak power density is 545 . Divide the two to calculate the difference ratio of the fuel cell performance obtained from the proton unidirectional conductivity, which is about 2.33.

[0114] Comparative Example 7:

[0115] Select polybenzene 1 with carboxyl groups and polybenzene 2 with carboxyl groups;

[0116] Dissolve polybenzene 1 with carboxyl groups and polybenzene 2 with carboxyl groups in solvents N-methylpyrrolidone and dimethyl sulfoxide respectively. After complete dissolution, perform vacuum degassing to form two film-forming solutions;

[0117] Fully mix the above two film-forming solutions evenly and pour them into a culture dish. The mass ratio of polybenzene 1 with carboxyl groups to polybenzene 2 with carboxyl groups is 35:65. Evaporate the solvent at a temperature of 110 °C until the solvent is completely evaporated to obtain a conventional membrane;

[0118] Perform acidification treatment on the conventional membrane to obtain a conventional ion exchange membrane.

[0119] The ion exchange membrane prepared in Comparative Example 7 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the membrane sides swapped, the peak power densities were 894 and 891 , which were basically the same, indicating that there was basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane of Example 7 when assembled in the proton unidirectional conduction dominant direction was 1269 , which was about 42% higher than the peak power density of the fuel cell of the ion exchange membrane of Comparative Example 7, which was 891 - 894 .

[0120] Example 8:

[0121] As shown in Table 1, polyphenylene ether with a quaternary amino group and polybiphenyl with a ferrocene salt group were selected;

[0122] The polyphenylene ether with a quaternary amino group and the polybiphenyl with a ferrocene salt group were respectively dissolved in solvents N-methylpyrrolidone and dimethylformamide. After complete dissolution, degassing was performed under vacuum to form two film-forming solutions;

[0123] The two film-forming solutions were respectively poured into two petri dishes, and the solvents were evaporated at a temperature of 70 °C so that the two film-forming solutions were basically shaped into initial films. The two initial films in the two petri dishes still contained a certain amount of solvent, and the remaining solvent amounts were obtained by weighing and calculating the film-forming raw materials, solvents, film-forming petri dishes, and film-forming solutions during the film-forming process, and the contents were 25% and 160% of the polymer mass in the initial films respectively;

[0124] The above two initial films were removed from the petri dishes, and one piece of the initial film of polyphenylene ether with a quaternary amino group and one piece of the initial film of polybiphenyl with a ferrocene salt group with the same shape and area were laminated together. The mass ratio of the polyphenylene ether with a quaternary amino group to the polybiphenyl with a ferrocene salt group in the initial film was 70:30. They were placed in a petri dish with the same shape and area as the laminated film, and the remaining solvent was evaporated at a temperature of 70 °C. During this process, the two initial films penetrated and fused with each other to obtain an integral film;

[0125] The integral film was alkalized to obtain an ion exchange membrane with a gradient change in ion conductivity in the through-plane direction. The gradient change in ion conductivity in the through-plane direction gradually increased from the side of the initial film of polybiphenyl with a ferrocene salt group to the side of the initial film of polyphenylene ether with a quaternary amino group, and the ion conduction advantage from the side of the initial film of polybiphenyl with a ferrocene salt group to the side of the initial film of polyphenylene ether with a quaternary amino group in the through-plane direction could be realized.

[0126] The ion exchange membrane prepared in Example 8 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane of poly(phenylene ether) with quaternary amino groups was in contact with the anode gas diffusion electrode and the side of the initial membrane of poly(biphenyl) with ferrocenium salt groups was in contact with the cathode gas diffusion electrode, the peak power density was 1844 ; when the side of the initial membrane of poly(phenylene ether) with quaternary amino groups was in contact with the cathode gas diffusion electrode and the side of the initial membrane of poly(biphenyl) with ferrocenium salt groups was in contact with the anode gas diffusion electrode, the peak power density was 1212 . The ratio of the differences in the performance directions of the fuel cells obtained by calculating the proton unidirectional conductivity by dividing the two was approximately 1.44

[0127] Comparative Example 8:

[0128] Poly(phenylene ether) with quaternary amino groups and poly(biphenyl) with ferrocenium salt groups were selected;

[0129] Poly(phenylene ether) with quaternary amino groups and poly(biphenyl) with ferrocenium salt groups were respectively dissolved in solvents N-methylpyrrolidone and dimethylformamide, and after complete dissolution, they were degassed under vacuum to form two film-forming solutions;

[0130] The above two film-forming solutions were thoroughly mixed and poured into a petri dish. The mass ratio of poly(phenylene ether) with quaternary amino groups to poly(biphenyl) with ferrocenium salt groups was 70:30, and the solvent was evaporated at 70 °C until the solvent was completely evaporated to obtain a conventional membrane;

[0131] The conventional membrane was alkalized to obtain a conventional ion exchange membrane.

[0132] The ion exchange membrane prepared in Comparative Example 8 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the two sides of the membrane interchanged, the peak power densities were 1531 and 1526 , which were basically the same, indicating that there was basically no difference in the conduction directionality of the membrane. The peak power density of the fuel cell assembled with the ion exchange membrane of Example 8 in the direction of the proton unidirectional conduction advantage was 1844 , which was about 21% higher than the peak power density of the fuel cell of the ion exchange membrane of Comparative Example 8, which was 1526 - 1531 .

[0133] Example 9:

[0134] As shown in Table 1, polyethersulfone with guanidine groups and polyetheretherketone with ferrocene salt groups were selected;

[0135] The polyethersulfone with guanidine groups and the polyetheretherketone with ferrocene salt groups were respectively dissolved in solvents dimethylformamide and m-cresol. After complete dissolution, they were degassed under vacuum to form two casting solutions;

[0136] The two casting solutions were respectively poured into two petri dishes, and the solvents were evaporated at a temperature of 65 °C, so that the two casting solutions were basically shaped into initial membranes. The two initial membranes in the two petri dishes still contained a certain amount of solvent, and the remaining solvent amounts were obtained by weighing and calculating the casting raw materials, solvents, film-forming petri dishes, and casting solutions during the film-forming process. The contents were 35% and 125% of the polymer mass in the initial membranes respectively;

[0137] The above two initial membranes were taken off from the petri dishes. One piece of the initial membrane of polyethersulfone with guanidine groups and one piece of the initial membrane of polyetheretherketone with ferrocene salt groups with the same shape and area were laminated together. The mass ratio of polyethersulfone with guanidine groups to polyetheretherketone with ferrocene salt groups in the initial membrane was 90:10. They were placed in a petri dish with the same shape and area as the laminated membrane, and the remaining solvents were evaporated at a temperature of 65 °C. During this process, the two initial membranes penetrated and fused with each other to obtain an integral membrane;

[0138] The integral membrane was alkalized to obtain an ion exchange membrane with a gradient change in ionic conductivity in the direction of the permeation surface. The gradient change in ionic conductivity in the direction of the permeation surface gradually increased from the side of the initial membrane of polyetheretherketone with ferrocene salt groups to the side of the initial membrane of polyethersulfone with guanidine groups, thus realizing the ionic conduction advantage from the side of the initial membrane of polyetheretherketone with ferrocene salt groups to the side of the initial membrane of polyethersulfone with guanidine groups in the direction of the permeation surface.

[0139] The ion exchange membrane prepared in Example 9 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting it to a hydrogen oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane of polyethersulfone with guanidine groups was in contact with the anode gas diffusion electrode and the side of the initial membrane of polyetheretherketone with ferrocene salt groups was in contact with the cathode gas diffusion electrode, the peak power density was 1114 ; when the side of the initial membrane of polyethersulfone with guanidine groups was in contact with the cathode gas diffusion electrode and the side of the initial membrane of polyetheretherketone with ferrocene salt groups was in contact with the anode gas diffusion electrode, the peak power density was 892 . The ratio of the difference in the performance direction of the fuel cell obtained by calculating the proton unidirectional conductivity by dividing the two was about 1.25.

[0140] Comparative Example 9:

[0141] Select polyethersulfone with guanidyl group and polyetheretherketone with ferrocene salt group;

[0142] Dissolve polyethersulfone with guanidyl group and polyetheretherketone with ferrocene salt group in solvents dimethylformamide and m-cresol respectively. After complete dissolution, degas under vacuum to form two casting solutions;

[0143] Fully mix the above two casting solutions evenly and pour them into a petri dish. The mass ratio of polyethersulfone with guanidyl group to polyetheretherketone with ferrocene salt group is 90:10. Evaporate the solvent at 65 °C until the solvent is completely evaporated to obtain a conventional membrane;

[0144] Alkalize the conventional membrane to obtain a conventional ion exchange membrane.

[0145] Assemble the ion exchange membrane prepared in Comparative Example 9 with a gas diffusion electrode, connect it to a hydrogen-oxygen fuel cell to test the polarization curve and calculate the power density. The same gas diffusion layer and catalytic layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode are assembled with the two sides of the membrane interchanged, the peak power densities are 974 and 969 , which are basically the same, indicating that there is basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane in Example 9 when assembled with a fuel cell in the proton unidirectional conduction dominant direction is 1114 , compared with the peak power density of the fuel cell of the ion exchange membrane in Comparative Example 9, which is 969 - 974 is increased by about 14%.

[0146] Example 10:

[0147] Select polynorbornene with cobaltocene salt group and polyphenylene ether with quaternary phosphonium group;

[0148] Dissolve polynorbornene with cobaltocene salt group and polyphenylene ether with quaternary phosphonium group in solvents N-methylpyrrolidone and m-cresol respectively. After complete dissolution, degas under vacuum to form two casting solutions;

[0149] Pour the two casting solutions into two petri dishes respectively. Evaporate the solvent at 60 °C to make the two casting solutions basically take shape into initial membranes. The two initial membranes in these two petri dishes still contain a certain amount of solvent. The remaining solvent amounts are obtained by weighing and calculating during the film-forming process of the film-forming raw materials, solvents, film-forming petri dishes, and casting solutions, and the contents are 180% and 15% of the polymer mass in the initial membranes respectively;

[0150] Remove the above two initial membranes from the petri dish. Select one piece of poly(norbornene) with a cobaltocene salt group and one piece of poly(phenylene ether) with a quaternary phosphonium group that have the same shape and area, and stack them together. The mass ratio of poly(norbornene) with a cobaltocene salt group to poly(phenylene ether) with a quaternary phosphonium group in the initial membranes is 20:80. Place them in a petri dish with the same shape and area as the stacked membrane, and evaporate the remaining solvent at a temperature of 60 °C. During this process, the two initial membranes penetrate and fuse with each other to obtain an integral membrane;

[0151] Alkalize the integral membrane to obtain an ion exchange membrane with a gradient change in ionic conductivity in the through-plane direction. The gradient change in ionic conductivity in the through-plane direction gradually increases from the side of the initial membrane of poly(phenylene ether) with a quaternary phosphonium group to the side of poly(norbornene) with a cobaltocene salt group, thus achieving the ionic conduction advantage from the side of the initial membrane of poly(phenylene ether) with a quaternary phosphonium group to the side of poly(norbornene) with a cobaltocene salt group in the through-plane direction.

[0152] The ion exchange membrane prepared in Example 10 is assembled with a gas diffusion electrode, and the polarization curve is measured and the power density is calculated by connecting to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , and the test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane of poly(norbornene) with a cobaltocene salt group contacts the anode gas diffusion electrode and the side of the initial membrane of poly(phenylene ether) with a quaternary phosphonium group contacts the cathode gas diffusion electrode, the peak power density is 833 ; when the side of the initial membrane of poly(norbornene) with a cobaltocene salt group contacts the cathode gas diffusion electrode and the side of the initial membrane of poly(phenylene ether) with a quaternary phosphonium group contacts the anode gas diffusion electrode, the peak power density is 691 . Divide the two to calculate the difference ratio of fuel cell performance obtained from the proton unidirectional conductivity, which is about 1.30.

[0153] Comparative Example 10:

[0154] Select poly(norbornene) with a cobaltocene salt group and poly(phenylene ether) with a quaternary phosphonium group;

[0155] Dissolve poly(norbornene) with a cobaltocene salt group and poly(phenylene ether) with a quaternary phosphonium group in solvents N-methylpyrrolidone and m-cresol respectively. After complete dissolution, degas under vacuum to form two film-forming solutions;

[0156] Fully mix the above two film-forming solutions evenly and pour them into a petri dish. The mass ratio of poly(norbornene) with a cobaltocene salt group to poly(phenylene ether) with a quaternary phosphonium group is 20:80. Evaporate the solvent at a temperature of 60 °C until the solvent is completely evaporated to obtain a conventional membrane;

[0157] Alkalize the conventional membrane to obtain a conventional ion exchange membrane.

[0158] The ion exchange membrane prepared in Comparative Example 10 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the membrane sides swapped, the peak power densities were 742 and 743 , which were basically the same, indicating that there was basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane of Example 10 when assembled in the proton unidirectional conduction advantageous direction was 833 , which was about 12% higher than the peak power density of the fuel cell of the ion exchange membrane of Comparative Example 10, which was 742-743 .

[0159] Example 11:

[0160] As shown in Table 1, polysulfone with a cobaltocene salt group and polyetheretherketone with a tertiary sulfonium group were selected;

[0161] The polysulfone with a cobaltocene salt group and the polyetheretherketone with a tertiary sulfonium group were respectively dissolved in solvents N-methylpyrrolidone and dimethylacetamide. After complete dissolution, they were degassed under vacuum to form two film-forming solutions;

[0162] The two film-forming solutions were respectively poured into two petri dishes, and the solvents were evaporated at a temperature of 75 °C so that the two film-forming solutions were basically shaped into initial membranes. The two initial membranes in these two petri dishes still contained a certain amount of solvent, and the remaining solvent amounts were obtained by weighing and calculating the film-forming raw materials, solvents, film-forming petri dishes, and film-forming solutions during the film-forming process, and the contents were 70% and 100% of the polymer mass in the initial membranes respectively;

[0163] The above two initial membranes were removed from the petri dishes, and one piece of the polysulfone initial membrane with a cobaltocene salt group and one piece of the polyetheretherketone initial membrane with the same shape and area were selected and laminated together. The mass ratio of the polysulfone with a cobaltocene salt group to the polyetheretherketone with a tertiary sulfonium group in the initial membrane was 25:75. They were placed in a petri dish with the same shape and area as the laminated membrane, and the remaining solvents were evaporated at a temperature of 75 °C. During this process, the two initial membranes penetrated and fused with each other to obtain an integral membrane;

[0164] The integral membrane was alkalized to obtain an ion exchange membrane with a gradient change in ion conductivity in the through-plane direction. The gradient change in ion conductivity in the through-plane direction increased gradually from the side of the initial membrane of polyetheretherketone with a tertiary sulfonium group to the side of the initial membrane of polysulfone with a cobaltocene salt group, thus realizing the ion conduction advantage from the side of the initial membrane of polyetheretherketone with a tertiary sulfonium group to the side of the initial membrane of polysulfone with a cobaltocene salt group in the through-plane direction.

[0165] The ion exchange membrane prepared in Example 11 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane of polysulfone with a cobaltocene salt group contacted the anode gas diffusion electrode and the side of the initial membrane of polyether ether ketone with a sulfonium group contacted the cathode gas diffusion electrode, the peak power density was 549 ; when the side of the initial membrane of polysulfone with a cobaltocene salt group contacted the cathode gas diffusion electrode and the side of the initial membrane of polyether ether ketone with a sulfonium group contacted the anode gas diffusion electrode, the peak power density was 381 . The ratio of the differences in the performance directions of the fuel cells obtained by calculating the proton unidirectional conductivity by dividing the two was approximately 1.44.

[0166] Comparative Example 11:

[0167] Polysulfone with a cobaltocene salt group and polyether ether ketone with a sulfonium group were selected;

[0168] Polysulfone with a cobaltocene salt group and polyether ether ketone with a sulfonium group were respectively dissolved in solvents N-methylpyrrolidone and dimethylacetamide, and after complete dissolution, degassing under vacuum was carried out to form two film-forming solutions;

[0169] The above two film-forming solutions were fully mixed and poured into a petri dish. The mass ratio of polysulfone with a cobaltocene salt group to polyether ether ketone with a sulfonium group was 25:75, and the solvent was evaporated at a temperature of 75 °C until the solvent was completely evaporated to obtain a conventional membrane;

[0170] The conventional membrane was alkalized to obtain a conventional ion exchange membrane.

[0171] The ion exchange membrane prepared in Comparative Example 11 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the two sides of the membrane interchanged, the peak power densities were 455 and 453 , which were basically the same, indicating that there was basically no difference in the conduction directionality of the membrane. The peak power density of the fuel cell when the ion exchange membrane of Example 11 was assembled in the direction of the proton unidirectional conduction advantage was 549 , which was about 21% higher than the peak power density of the fuel cell of the ion exchange membrane of Comparative Example 11, which was 453 - 455 .

[0172] Example 12:

[0173] As shown in Table 1, polybiphenyl with guanidine groups and polyphenylene ether with quaternary amine groups were selected.

[0174] The polybiphenyl with guanidine groups and the polyphenylene ether with quaternary amine groups were respectively dissolved in solvents dimethylformamide and dimethyl sulfoxide. After complete dissolution, they were degassed under vacuum to form two film-forming solutions.

[0175] The two film-forming solutions were respectively poured into two petri dishes, and the solvents were evaporated at a temperature of 60 °C, so that the two film-forming solutions were basically shaped into initial films. The two initial films in these two petri dishes still contained a certain amount of solvent, and the remaining solvent amounts were obtained by weighing and calculating the film-forming raw materials, solvents, film-forming petri dishes, and film-forming solutions during the film-forming process. The contents were 90% and 70% of the polymer mass in the initial films respectively.

[0176] The above two initial films were removed from the petri dishes, and one piece of the polybiphenyl initial film with guanidine groups and one piece of the polyphenylene ether initial film with quaternary amine groups with the same shape and area were selected and laminated together. The mass ratio of the polybiphenyl with guanidine groups to the polyphenylene ether with quaternary amine groups in the initial film was 45:55. They were put into a petri dish with the same shape and area as the laminated film, and the remaining solvents were evaporated at a temperature of 60 °C. During this process, the two initial films penetrated and fused with each other to obtain an integral film.

[0177] The integral film was alkalized to obtain an ion exchange membrane with a gradient change in ionic conductivity in the through-plane direction. The gradient change in ionic conductivity in the through-plane direction increased gradually from the side of the initial film of polyphenylene ether with quaternary amine groups to the side of the initial film of polybiphenyl with guanidine groups, thus realizing the ionic conduction advantage from the side of the initial film of polyphenylene ether with quaternary amine groups to the side of the initial film of polybiphenyl with guanidine groups in the through-plane direction.

[0178] The ion exchange membrane prepared in Example 12 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated when connected to a hydrogen oxygen fuel cell. The same gas diffusion layer and catalytic layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial film of polybiphenyl with guanidine groups was in contact with the anode gas diffusion electrode and the side of the initial film of polyphenylene ether with quaternary amine groups was in contact with the cathode gas diffusion electrode, the peak power density was 2979 ; when the side of the initial film of polybiphenyl with guanidine groups was in contact with the cathode gas diffusion electrode and the side of the initial film of polyphenylene ether with quaternary amine groups was in contact with the anode gas diffusion electrode, the peak power density was 1320 . The ratio of the differences in the performance directions of the fuel cells obtained by calculating the proton unidirectional conductivity by dividing the two was approximately 2.26.

[0179] Comparative Example 12:

[0180] Select polyphenyl with guanidine group and polyphenylene ether with quaternary amine group;

[0181] Dissolve polyphenyl with guanidine group and polyphenylene ether with quaternary amine group in solvents dimethylformamide and dimethyl sulfoxide respectively. After complete dissolution, degas under vacuum to form two film-forming solutions;

[0182] Fully mix the above two film-forming solutions and pour them into a petri dish. The mass ratio of polyphenyl with guanidine group to polyphenylene ether with quaternary amine group is 45:55. Evaporate the solvent at 60 °C until the solvent is completely evaporated to obtain a conventional membrane;

[0183] Alkalize the conventional membrane to obtain a conventional ion exchange membrane.

[0184] Assemble the ion exchange membrane prepared in Comparative Example 12 with a gas diffusion electrode, connect it to a hydrogen-oxygen fuel cell to test the polarization curve and calculate the power density. The same gas diffusion layer and catalyst layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 . The test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode are assembled with the two sides of the membrane interchanged, the peak power densities are 2005 and 2009 , which are basically the same, indicating that there is basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane in Example 12 when assembled in the proton unidirectional conduction advantageous direction is 2979 , which is about 48% - 49% higher than the peak power density of the fuel cell of the ion exchange membrane in Comparative Example 12, which is 2005 - 2009 .

[0185] Example 13:

[0186] As shown in Table 1, select polyphenyl with guanidine group and polyphenyl with quaternary amine group;

[0187] Dissolve polyphenyl with guanidine group and polyphenyl with quaternary amine group in solvents dimethylformamide and dimethyl sulfoxide respectively. After complete dissolution, degas under vacuum to form two film-forming solutions;

[0188] Pour the two film-forming solutions into two petri dishes respectively, and evaporate the solvent at 65 °C to make the two film-forming solutions basically take shape into initial membranes. The two initial membranes in these two petri dishes still contain a certain amount of solvent, and the remaining solvent amounts are obtained by weighing and calculation during the film-forming process of the film-forming raw materials, solvents, film-forming petri dishes, and film-forming solutions, and the contents are 80% and 90% of the polymer mass in the initial membranes respectively;

[0189] Remove the above two initial membranes from the culture dish. Select one piece of polybiphenyl with guanidyl and one piece of polybiphenyl with quaternary amino group that have the same shape and area, and laminate them together. The mass ratio of polybiphenyl with guanidyl to polybiphenyl with quaternary amino group in the initial membrane is 60:40. Place them in a culture dish with the same shape and area as the laminated membrane, and evaporate the remaining solvent at a temperature of 65 °C. During this process, the two initial membranes penetrate and fuse with each other to obtain an integral membrane;

[0190] Alkalize the integral membrane to obtain an ion exchange membrane with a gradient change in ionic conductivity in the through-plane direction. The gradient change in ionic conductivity in the through-plane direction gradually increases from the side of the initial membrane of polybiphenyl with quaternary amino group to the side of the initial membrane of polybiphenyl with guanidyl, thus realizing the ionic conduction advantage from the side of the initial membrane of polybiphenyl with quaternary amino group to the side of the initial membrane of polybiphenyl with guanidyl in the through-plane direction.

[0191] The ion exchange membrane prepared in Example 13 is assembled with a gas diffusion electrode, and the polarization curve is measured and the power density is calculated by connecting to a hydrogen oxygen fuel cell. The same gas diffusion layer and catalytic layer are used for the anode and cathode gas diffusion electrodes, and the catalyst loading is 0.3 , The test conditions are 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane of polybiphenyl with guanidyl contacts the anode gas diffusion electrode and the side of the initial membrane of polybiphenyl with quaternary amino group contacts the cathode gas diffusion electrode, the peak power density is 2861 ; When the side of the initial membrane of polybiphenyl with guanidyl contacts the cathode gas diffusion electrode and the side of the initial membrane of polybiphenyl with quaternary amino group contacts the anode gas diffusion electrode, the peak power density is 1127 . Divide the two to calculate the difference ratio of fuel cell performance obtained from the proton unidirectional conductivity, which is about 2.54.

[0192] Comparative Example 13:

[0193] Select polybiphenyl with guanidyl and polybiphenyl with quaternary amino group;

[0194] Dissolve polybiphenyl with guanidyl and polybiphenyl with quaternary amino group in solvents dimethylformamide and dimethyl sulfoxide respectively. After complete dissolution, degas under vacuum to form two membrane-making solutions;

[0195] Fully mix the above two membrane-making solutions evenly and pour them into a culture dish. The mass ratio of polybiphenyl with guanidyl to polybiphenyl with quaternary amino group is 60:40. Evaporate the solvent at a temperature of 65 °C until the solvent is completely evaporated to obtain a conventional membrane;

[0196] Alkalize the conventional membrane to obtain a conventional ion exchange membrane.

[0197] The ion exchange membrane prepared in Comparative Example 13 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the membrane sides swapped, the peak power densities were 1882 and 1885 , which were basically the same, indicating that there was basically no difference in the conduction directionality of the membrane. The peak power density of the ion exchange membrane of Example 13 when assembled in the proton unidirectional conduction advantageous direction was 2861 , which was about 52% higher than the peak power density of the fuel cell of the ion exchange membrane of Comparative Example 13, which was 1882 - 1885 .

[0198] Example 14:

[0199] As shown in Table 1, polyether ether ketone 1 with a sulfonium group and polyether ether ketone 2 with a sulfonium group were selected;

[0200] Polyether ether ketone 1 with a sulfonium group and polyether ether ketone 2 with a sulfonium group were respectively dissolved in solvents N-methylpyrrolidone and m-cresol. After complete dissolution, they were degassed under vacuum to form two film-forming solutions;

[0201] The two film-forming solutions were respectively poured into two petri dishes, and the solvents were evaporated at a temperature of 80 °C so that the two film-forming solutions were basically shaped into initial membranes. The two initial membranes in these two petri dishes still contained a certain amount of solvent, and the remaining solvent amounts were obtained by weighing and calculating the film-forming raw materials, solvents, film-forming petri dishes, and film-forming solutions during the film-forming process, and the contents were 90% and 110% of the polymer mass in the initial membranes respectively;

[0202] The above two initial membranes were taken off from the petri dishes, and one piece of the initial membrane of polyether ether ketone 1 with a sulfonium group and one piece of the initial membrane of polyether ether ketone 2 with a sulfonium group with the same shape and area were laminated together. The mass ratio of polyether ether ketone 1 with a sulfonium group to polyether ether ketone 2 with a sulfonium group in the initial membrane was 40:60, and they were placed in a petri dish with the same shape, area as the laminated membrane, and the remaining solvent was evaporated at a temperature of 80 °C. During this process, the two initial membranes penetrated and fused with each other to obtain an integral membrane;

[0203] The integral membrane was alkalized to obtain an ion exchange membrane with a gradient change in ionic conductivity in the through-plane direction. The gradient change in ionic conductivity in the through-plane direction gradually increased from the side of the initial membrane of polyether ether ketone 2 with a sulfonium group to the side of the initial membrane of polyether ether ketone 1 with a sulfonium group, and thus the ionic conduction advantage from the side of the initial membrane of polyether ether ketone 2 with a sulfonium group to the side of the initial membrane of polyether ether ketone 1 with a sulfonium group in the through-plane direction was achieved.

[0204] The ion exchange membrane prepared in Example 14 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the side of the initial membrane with sulfonium group-containing polyether ether ketone 1 was in contact with the anode gas diffusion electrode and the side of the initial membrane with sulfonium group-containing polyether ether ketone 2 was in contact with the cathode gas diffusion electrode, the peak power density was 1003 ; when the side of the initial membrane with sulfonium group-containing polyether ether ketone 1 was in contact with the cathode gas diffusion electrode and the side of the initial membrane with sulfonium group-containing polyether ether ketone 2 was in contact with the anode gas diffusion electrode, the peak power density was 534 . The ratio of the difference in the performance direction of the fuel cell obtained by calculating the proton unidirectional conductivity by dividing the two was about 1.88.

[0205] Comparative Example 14:

[0206] Sulfonium group-containing polyether ether ketone 1 and sulfonium group-containing polyether ether ketone 2 were selected;

[0207] Sulfonium group-containing polyether ether ketone 1 and sulfonium group-containing polyether ether ketone 2 were respectively dissolved in solvents N-methylpyrrolidone and m-cresol, and after complete dissolution, they were degassed under vacuum to form two film-forming solutions;

[0208] The above two film-forming solutions were fully mixed and poured into a petri dish. The mass ratio of sulfonium group-containing polyether ether ketone 1 to sulfonium group-containing polyether ether ketone 2 was 40:60. The solvent was evaporated at 80 °C until the solvent was completely evaporated to obtain a conventional membrane;

[0209] The conventional membrane was alkalized to obtain a conventional ion exchange membrane.

[0210] The ion exchange membrane prepared in Comparative Example 14 was assembled with a gas diffusion electrode, and the polarization curve was measured and the power density was calculated by connecting it to a hydrogen-oxygen fuel cell. The same gas diffusion layer and catalyst layer were used for the anode and cathode gas diffusion electrodes, and the catalyst loading was 0.3 , and the test conditions were 80 °C, 80% relative humidity, and 1 MPa back pressure. When the anode and cathode were assembled with the two sides of the membrane interchanged, the peak power densities were 729 and 722 , which were basically the same, indicating that there was basically no difference in the conduction directionality of the membrane. The peak power density of the fuel cell assembled with the ion exchange membrane of Example 14 in the direction of the proton unidirectional conduction advantage was 1003 , which was about 38% higher than the peak power density of the fuel cell of the ion exchange membrane of Comparative Example 14, which was 722-729 .

[0211] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an ion exchange membrane having a gradient ion conductivity, characterized in that: The steps of the method include: S1: selecting two ion-conducting polymers, the ion-conducting polymers comprising polymer A and polymer B, the ion conductivity of polymer A being higher than the ion conductivity of polymer B; S2: dissolving the polymer A and the polymer B in solvent A and solvent B respectively, wherein the polymer A is fully dissolved in solvent A to obtain film-forming solution A, and the polymer B is fully dissolved in solvent B to obtain film-forming solution B; S3: pouring the film-forming solution A into a culture dish A and the film-forming solution B into a culture dish B, and after evaporating part of the solvent A and part of the solvent B, the film-forming solution A is formed into an initial film A in the culture dish A, and the film-forming solution B is formed into an initial film B in the culture dish B; S4: Select one piece of the initial film A and one piece of the initial film B of the same shape and area, and attach them up and down in a culture dish C. The shape and area of ​​the culture dish C are consistent with the initial film A and the initial film B selected in this step. Completely evaporate the solvent A and the solvent B in the culture dish C to obtain an integral film; S5: acidifying or alkalizing the entire membrane to obtain an ion exchange membrane with a gradient-varying ion conductivity in the permeable surface direction.

2. The method for preparing an ion exchange membrane with gradient ion conductivity according to claim 1, characterized in that: The ion-conducting groups of the polymer A and the polymer B are one of sulfonic acid group, carboxylic acid group, phosphonic acid group, hydroxyl group, ferrocyanide group, quaternary amine group, guanidine group, quaternary phosphine group, tertiary sulfonium group, ferrocenium salt group and cobaltocene salt group.

3. The method for preparing an ion exchange membrane with gradient ion conductivity according to claim 2, characterized in that: The main chain of the polymer A and the polymer B is one of polyperfluoroethylene, polyvinylidene fluoride, polyphenyl, polystyrene, polyvinyl pyridine, polyethylene, polysulfone, polyethersulfone, polyetheretherketone, polyphenylene ether, polybiphenyl, and polynorbornene.

4. The method for preparing an ion exchange membrane with gradient ion conductivity according to claim 1, characterized in that: The solvent A and the solvent B are one of dimethylformamide, dimethylacetamide, nitrogen-methylpyrrolidone, dimethyl sulfoxide and m-cresol.

5. The method for preparing an ion exchange membrane with gradient ion conductivity according to claim 1, characterized in that: The content of the remaining solvent A in the initial film A in the culture dish A is 10%-200% of the mass of the polymer in the initial film A; the content of the remaining solvent B in the initial film B in the culture dish B is 10%-200% of the mass of the polymer in the initial film B.

6. The method for preparing an ion exchange membrane with gradient ion conductivity according to claim 1, characterized in that: The temperature required to evaporate part of the solvent A and part of the solvent B is 60°C to 120°C.

7. The method for preparing an ion exchange membrane with gradient ion conductivity according to claim 6, characterized in that: The temperature required for completely evaporating the solvent A and the solvent B in the culture dish C is 60° C. to 120° C.

8. The method for preparing an ion exchange membrane with gradient ion conductivity according to claim 1, characterized in that: The mass ratio of the polymer A to the polymer B in the initial film A and the initial film B having the same shape and area is 10:90 to 90:10.

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