Alkali-resistant composite porous diaphragm as well as preparation method and application thereof

Abstract

The invention discloses an alkali-resistant composite porous diaphragm as well as a preparation method and application thereof, and belongs to the field of membrane materials. The alkali-resistant composite porous diaphragm comprises an alkali-resistant polymer supporting net layer and a functional polymer layer, the functional polymer layer wraps the alkali-resistant polymer supporting net layer; hydrophilic inorganic nanoparticles are dispersed in the functional polymer layer. The composition of the functional polymer is adjusted, so that the functional polymer has good compatibility with the inorganic nanoparticles and the alkali-resistant polymer supporting network at the same time; and preparing the diaphragm material with high alkali-resistant stability, high proton conductivity, high hydrophilicity and high gas barrier property by a solvent-induced phase inversion method. The membrane material has wide application prospects in alkaline system energy conversion and storage devices such as alkaline water electrolysis hydrogen production and alkaline system flow batteries.

Description

Technical Field

[0001] The present application relates to an alkali-resistant composite porous separator and its preparation method and application, belonging to the field of membrane materials. Background Art

[0002] In modern society, the energy problem has become increasingly urgent. With the widespread application of renewable energy such as solar energy and wind energy, carbon neutrality and reduction of greenhouse gas emissions have become global goals. In this context, energy conversion and storage devices in alkaline systems have become increasingly important. Developing energy conversion and storage devices in alkaline systems, such as alkaline water electrolysis for hydrogen production and alkaline flow batteries, is to meet the challenges of future clean energy utilization and sustainable development and to address the needs of electrical energy storage and distribution.

[0003] First of all, alkaline water electrolysis for hydrogen production is an important technology that can decompose water into hydrogen and oxygen using electrical energy. Hydrogen, as one of the green clean energy sources, can be converted into electrical energy in a fuel cell, while only producing by-product water vapor. The development of alkaline water electrolysis for hydrogen production technology helps to achieve the production of green and clean hydrogen energy, thereby reducing the dependence on fossil fuels. In addition, the high economic value and high efficiency of alkaline water electrolysis for hydrogen production technology make it a key to realizing large-scale hydrogen energy production. Secondly, alkaline flow batteries also have great potential. A flow battery is a device that can convert electrical energy into chemical energy and release electrical energy again. Alkaline flow batteries usually involve the transfer of electrons between two electrolyte liquids. This technology has high scalability and flexibility and can play a key role in grid energy storage. Flow batteries under alkaline conditions are usually safer and more cost-effective, making them an ideal choice for realizing large-scale storage and distribution of renewable energy.

[0004] In summary, developing energy conversion and storage devices in alkaline systems is to achieve the goal of large-scale utilization of clean energy and sustainable development. These technologies can reduce the dependence on fossil fuels, improve the efficiency of the energy system, and at the same time reduce the impact on the environment. They will bring significant changes to the future green and clean energy field and promote the development of carbon neutrality and sustainable energy.

[0005] Currently, the separator, which is the core of energy conversion and storage devices in alkaline systems, still faces the following challenges:

[0006] (1) The separator is prone to degradation in an alkaline environment, resulting in a decrease in service life.

[0007] (2) To reduce the surface resistance of the membrane, the common methods are to modify the polymer in the membrane with basic hydrophilic groups of different structures (such as quaternary ammonium salts, etc.) or to increase the porosity of the membrane and reduce the thickness of the membrane. However, the alkali resistance stability of the basic hydrophilic groups is not high, and introducing them will directly reduce the alkali resistance stability of the membrane; while increasing the porosity of the membrane or reducing the thickness of the membrane is also likely to cause impurity ions or gas products to permeate across the membrane, reducing the selectivity of the membrane.

[0008] (3) The mechanical strength of the membrane is relatively low, and it is prone to breakage when assembled into energy conversion and storage devices in an alkaline system. Summary of the Invention

[0009] According to one aspect of the present application, an alkali-resistant composite porous separator is provided. The alkali-resistant composite porous separator can exhibit high selectivity (gas barrier property, ion selectivity) and high ion conduction ability while maintaining excellent alkali resistance stability. Such membrane materials have broad application prospects in energy conversion and storage devices in an alkaline system, such as alkaline water electrolysis for hydrogen production and alkaline redox flow batteries.

[0010] The alkali-resistant composite porous separator of the present application includes an alkali-resistant polymer support network layer and a functional polymer layer;

[0011] The thickness of the alkali-resistant composite porous separator is 30 - 700 μm;

[0012] The functional polymer layer wraps the alkali-resistant polymer support network layer;

[0013] Hydrophilic inorganic nanoparticles are dispersed in the functional polymer layer.

[0014] Optionally, the functional polymer in the functional polymer layer includes a first type of functional polymer and a second type of functional polymer;

[0015] The first type of functional polymer is a hydrophobic functional polymer;

[0016] The second type of functional polymer is a hydrophilic functional polymer.

[0017] Optionally, the hydrophobic functional polymer is selected from any one or more of polyethersulfone, polysulfone, chloromethylated polysulfone, polyether ketone, and polyolefin; preferably, the hydrophobic functional polymer is polyethersulfone.

[0018] Optionally, the hydrophilic functional polymer is selected from any one or more of sulfonated polyether ether ketone, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, and sulfonated polystyrene; preferably, the hydrophilic functional polymer is sulfonated polyether ether ketone.

[0019] Optionally, the mass ratio of the first type of functional polymer to the second type of functional polymer is 99:1 to 70:30; preferably, the mass ratio of the first type of functional polymer to the second type of functional polymer is 94:6.

[0020] Optionally, the hydrophilic inorganic nanoparticles are selected from any one or more of zirconia, titanium oxide, alumina, and magnesia, and have good hydrophilicity and alkali resistance stability; preferably, the hydrophilic inorganic nanoparticles are zirconia.

[0021] Optionally, the diameter of the hydrophilic inorganic nanoparticles is 10 to 100 nm; preferably, the diameter of the hydrophilic inorganic nanoparticles is 50 nm.

[0022] Optionally, the mass of the hydrophilic inorganic nanoparticles is 20 to 70% of the functional polymer; preferably, the mass of the hydrophilic inorganic nanoparticles is 40 to 60% of the functional polymer.

[0023] Optionally, the alkali-resistant polymer support mesh layer of the alkali-resistant polymer support mesh is selected from any one or more of polyphenylene sulfide mesh, polyurea mesh, and alkali-resistant glass fiber mesh.

[0024] Optionally, the alkali-resistant polymer support mesh is 10 to 200 mesh; preferably, the alkali-resistant polymer support mesh is 30 to 80 mesh.

[0025] Optionally, the thickness of the alkali-resistant polymer support mesh is 10 to 100 μm; preferably, the thickness of the alkali-resistant polymer support mesh is 30 to 70 μm.

[0026] Another aspect of the present application provides a method for preparing the alkali-resistant composite porous separator, including: stirring a mixture of a functional polymer, hydrophilic inorganic nanoparticles, and an organic solvent to obtain a mixed solution, coating the mixed solution on a dust-free glass plate carrying an alkali-resistant polymer support mesh, and soaking the coated plate in water to obtain the alkali-resistant composite porous separator.

[0027] Optionally, the method for preparing the alkali-resistant composite porous separator includes the following steps:

[0028] (1) Mixing a functional polymer and an organic solvent to obtain a functional polymer solution;

[0029] (2) Adding hydrophilic inorganic nanoparticles to the functional polymer solution to obtain a mixture;

[0030] (3) Stirring the mixture to obtain a mixed solution, coating the mixed solution on a dust-free glass plate carrying an alkali-resistant polymer support mesh, and soaking the coated plate in water to obtain the alkali-resistant composite porous separator.

[0031] Optionally, the functional polymer includes a first type of functional polymer and a second type of functional polymer;

[0032] The first type of functional polymer is a hydrophobic functional polymer;

[0033] The second type of functional polymer is a hydrophilic functional polymer.

[0034] Optionally, the hydrophobic functional polymer is selected from any one or more of polyethersulfone, polysulfone, chloromethylated polysulfone, polyether ketone, and polyolefin; preferably, the hydrophobic functional polymer is polyethersulfone.

[0035] Optionally, the hydrophilic functional polymer is selected from any one or more of sulfonated polyether ether ketone, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and sulfonated polystyrene; preferably, the hydrophilic functional polymer is sulfonated polyether ether ketone.

[0036] Optionally, the mass ratio of the first type of functional polymer to the second type of functional polymer is 99:1 to 70:30; preferably, the mass ratio of the first type of functional polymer to the second type of functional polymer is 95:5 to 75:25.

[0037] The functional polymer solution includes a functional polymer and an organic solvent.

[0038] Optionally, the solid content of the functional polymer in the functional polymer solution is 10 to 50 wt%; preferably, the solid content of the functional polymer in the functional polymer solution is 15 to 40 wt%.

[0039] Optionally, the organic solvent is selected from any one or more of dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone; preferably dimethylacetamide.

[0040] Optionally, the hydrophilic inorganic nanoparticles are selected from any one or more of zirconia, titania, alumina, and magnesia, and have good hydrophilicity and alkali resistance stability.

[0041] Preferably, the hydrophilic inorganic nanoparticles are zirconia.

[0042] Optionally, the diameter of the hydrophilic inorganic nanoparticles is 10 to 100 nm; preferably, the diameter of the hydrophilic inorganic nanoparticles is 50 nm.

[0043] Optionally, the mass of the hydrophilic inorganic nanoparticles is 20 to 70% of the functional polymer; preferably, the mass of the hydrophilic inorganic nanoparticles is 40 to 60% of the functional polymer.

[0044] Optionally, the alkali-resistant polymer support mesh of the alkali-resistant polymer support mesh layer is selected from any one or more of polyphenylene sulfide mesh, polyurea mesh, and alkali-resistant glass fiber mesh.

[0045] Optionally, the alkali-resistant polymer support mesh is 10 to 200 mesh; preferably, the alkali-resistant polymer support mesh is 30 to 80 mesh.

[0046] Optionally, the thickness of the alkali-resistant polymer support mesh is 10 to 100 μm; preferably, the thickness of the alkali-resistant polymer support mesh is 30 to 70 μm.

[0047] The coating method is knife coating.

[0048] Optionally, the speed of the knife coating is 0.1 to 1 cm·s -1 ; preferably, the speed of the knife coating is 0.3 to 0.8 cm·s -1 .

[0049] Another aspect of the present application provides an application of the alkali-resistant composite porous separator in energy conversion and storage devices in an alkaline system.

[0050] Optionally, the energy conversion and storage devices in the alkaline system include but are not limited to alkaline water electrolysis for hydrogen production and alkaline flow batteries.

[0051] The beneficial effects that the present application can produce include:

[0052] (1) The preparation method of the alkali-resistant composite porous separator disclosed in the present application can enable the functional polymer in the composite membrane to have good compatibility with the support mesh and hydrophilic nanoparticles at the same time, which is beneficial for the composite membrane to maintain good mechanical strength and hydrophilicity at the same time.

[0053] (2) The preparation method of the alkali-resistant composite porous separator disclosed in the present application adjusts the component ratio, formulation and film-making process in the membrane, so that the composite membrane has a low surface resistance, thereby maintaining a high ion conduction ability.

[0054] (3) The preparation method of the alkali-resistant composite porous separator disclosed in the present application adjusts the microstructure of the composite membrane, ensuring that the composite membrane maintains high membrane material selectivity (gas barrier property, ion selectivity) while having a high ion conduction ability.

[0055] (4) The proposed alkali-resistant composite porous separator of the present application has excellent alkali resistance stability, expanding the selection range of membrane materials for energy conversion and storage devices applied to alkaline systems. Description of the Drawings

[0056] Figure 1 The polarization curve of the alkali-resistant composite porous separator prepared in Example 1 in the electrolytic cell for alkaline water electrolysis for hydrogen production.

[0057] Figure 2aIt is the micrograph of the alkali-resistant composite porous separator prepared in Example 1 observed by scanning electron microscope, and the membrane thickness is 220 μm.

[0058] Figure 2b It is the corresponding element distribution map of the alkali-resistant composite porous separator prepared in Example 1 observed by scanning electron microscope, and the membrane thickness is 220 μm.

[0059] Figure 3 It is the long cycle performance of the alkali-resistant composite porous separator prepared in Example 1 in an alkaline zinc-iron flow battery.

[0060] Figure 4 It is the rate performance curve of the alkali-resistant composite porous separator prepared in Example 1 in an alkaline zinc-iron flow battery.

[0061] Figure 5 It is the polarization curve of the alkali-resistant composite porous separator prepared in Example 1 in an alkaline zinc-iron flow battery.

[0062] Figure 6a It is the water contact angle of the membrane prepared in Example 1.

[0063] Figure 6b It is the water contact angle of the membrane prepared in Example 2.

[0064] Figure 6c It is the water contact angle of the membrane prepared in Example 3. Detailed implementation manners

[0065] The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples.

[0066] Unless otherwise specified, the raw materials in the examples of the present application are all purchased through commercial channels.

[0067] Example 1

[0068] Preparation process of the alkali-resistant composite porous separator:

[0069] (1) Polyethersulfone and sulfonated polyether ether ketone (sulfonation degree is 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 94:6, and the solid content is 30 wt%, to prepare an organic solution of the functional polymer.

[0070] (2) Zirconia with a particle size of 50 nm is added to the organic solution prepared in step (1), and the mass of zirconia is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h.

[0071] (3) The organic solution prepared in step (2) is doctor-bladed on a dust-free glass plate carrying a polyphenylene sulfide support mesh with 50 meshes, a size of 10 cm × 10 cm, and a thickness of 50 μm, and the doctor-blading speed is 0.5 cm·s-1 ; After scraping coating, soak the film in water at room temperature for 20 min. After soaking, rinse the composite film with water until it is clean.

[0072] Use a field emission scanning electron microscope (JEOL Ltd.—JSM-7800F) to observe the microstructure of the alkali-resistant composite film ( Figures 2a to 2b ), the thickness of the alkali-resistant composite separator is 220 μm, the polyphenylene sulfide support network is distributed inside the composite film, and the functional polymer uniformly wraps the support network, and zirconia is uniformly distributed in the functional polymer.

[0073] Wipe the surface water of the alkali-resistant composite porous separator clean and weigh it, and record the mass as m1; then dry it at 80 °C for 72 h, weigh it after the film is completely dehydrated, and record it as m2. The water absorption rate of the composite film can be calculated according to the formula [(m2 - m1) / m1], and the water absorption rate is 49.5%.

[0074] Use a universal testing machine to conduct tensile mechanical property tests on the composite film at a load rate of 10 mm·min -1 , and the maximum tensile strength is 25.5 MPa.

[0075] Conduct membrane surface resistance tests on the alkali-resistant composite porous separator. The test method is as follows: Clamp the composite film in an H-shaped electrolytic cell (Tianjin Aida Hengsheng H-type electrolytic cell—CH2001-S), and calculate the resistance of the electrolytic cell according to the slope of the I-V curve. Measure the resistance values of the electrolytic cell with and without the film assembled respectively, and the surface resistance of the composite film can be obtained by using the difference between the two:

[0076] R Ω = S×(R1 - R2)

[0077] Where R Ω is the surface resistance of the film; S is the effective area of the film (0.785 cm 2 ); R1 is the resistance of the electrolytic cell with the film, and R2 is the resistance of the electrolytic cell without the film. The surface resistance values of the film are recorded in Table 2.

[0078] Immerse the alkali-resistant composite porous separator in a 7 mol·L -1 potassium hydroxide solution at 80 °C, and regularly measure the mass loss percentage of the composite film (the percentage of the mass loss of the film in the initial weight before soaking in the alkali solution) to analyze the alkali resistance stability of the composite film. The results show that the film can maintain a mass loss of less than 0.06% within 1000 hours (Table 1).

[0079] Table 1

[0080]

[0081] The prepared alkali-resistant composite membrane was installed in the device for hydrogen production by alkaline water electrolysis: The electrolysis device was arranged in the following order: the cathode end plate (high-purity graphite plate), the porous cathode gas diffusion electrode, the alkali-resistant composite membrane, the porous anode gas diffusion electrode, and the anode end plate (TA2 titanium plate plated with platinum on the surface, with a platinum coating thickness of 2 μm). Among them, the porous cathode gas diffusion electrode was nickel foam sprayed with Raney nickel on the surface. The porosity of the nickel foam was 95%, the thickness was 500 μm, and the loading of Raney nickel was 1.8 mg·cm -2 ; The porous anode gas diffusion electrode was platinum-plated titanium foam. The porosity of the titanium foam was 95%, the thickness was 200 μm, and the thickness of the platinum coating was 2 μm. The test conditions were as follows: at 80 °C, with a flow rate of 10 mL·min -1 6 mol·L -1 potassium hydroxide solution was introduced into the electrolytic cell. The electrolysis voltage at the cathode and anode was controlled within the range of 1 V to 2 V, and the rate of voltage increase from 1 V to 2 V was 20 mV·min -1 . During the voltage increase process, the current density of the electrolytic cell was measured, and the obtained polarization curve is shown in Figure 1 . The measured electrolysis performance was that at an electrolysis voltage of 1.8 V, the current density was 730 mA·cm -2 .

[0082] The prepared alkali-resistant composite porous diaphragm was installed in an alkaline zinc-iron redox flow battery: The positive and negative electrodes were both porous carbon felt electrodes, and the current collectors were both graphite plates; The composition of the positive electrode electrolyte of the battery was 0.8 mol·L -1 Fe(CN)6 4- + 3 mol·L -1 KOH; The composition of the negative electrode electrolyte was 0.4 mol·L -1 Zn(OH)4 2- + 3 mol·L -1 NaOH. The battery adopted a constant current charge-discharge mode. It was charged for 18 min at a current density of 80 mA·cm -2 , and then discharged to 0.1 V at a current density of 80 mA·cm -2 . The Coulombic efficiency of the battery was 97.7%, and the voltage efficiency was 91.2%. Figure 3 The long cycle performance of the prepared alkali-resistant composite porous diaphragm in the alkaline zinc-iron redox flow battery is shown. The test results show that the composite membrane can maintain stable Coulombic efficiency and voltage efficiency within 200 cycles. Figure 4 The rate performance curve of the alkali-resistant composite porous diaphragm prepared in Example 1 in the alkaline zinc-iron redox flow battery is shown. The test conditions were 80 mA·cm -2 , 140 mA·cm -2 , 160 mA·cm -2 , 180 mA·cm -2, 200 mA·cm -2 , 300 mA·cm -2 ; The test results show that the performance of the composite membrane can still be maintained above 70% under high-rate conditions. Figure 5 The polarization curve of the alkali-resistant composite porous separator prepared in Example 1 in an alkaline zinc-iron flow battery, conditions: voltage 0.2 - 1.9 V, the peak power density can reach 800 mW·cm -2 .

[0083] Figure 6a ~c are the water contact angles of the membranes prepared in Example 1, Example 2, and Example 3 respectively. The instrument model is Shanghai Zhongchen JC-2000D. The contact angle of Example 1 is measured to be 61°, the contact angle of Example 2 is measured to be 64°, and the contact angle of Example 3 is measured to be 69°.

[0084] Comparative Example 1

[0085] The process and conditions are the same as those in Example 1. The difference is that after the solution is prepared according to the method in step (1) of Example 1, the organic solution is directly spin-coated on a dust-free glass plate carrying a polyphenylene sulfide support mesh with 50 meshes, a size of 10 cm × 10 cm, and a thickness of 50 μm. The spin-coating speed is 0.5 cm·s -1 ; After spin-coating, the membrane is immersed in water at room temperature for 20 min. After immersion, the composite membrane is rinsed clean with water.

[0086] Example 2

[0087] The process and conditions are the same as those in Example 1. The difference is that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide in a mass ratio of 94:6, and the solid content is 30 wt% to prepare an organic solution of the functional polymer. Subsequently, zirconia with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconia is 60% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The methods of preparing the membrane material by spin-coating and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0088] Example 3

[0089] The process and conditions are the same as those in Example 1. The difference is that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 94:6, and the solid content is 30 wt%, to obtain an organic solution of the functional polymer. Subsequently, zirconia with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconia is 40% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The remaining methods of preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0090] Comparative Example 2

[0091] The process and conditions are the same as those in Example 1. The difference is that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 94:6, and the solid content is 10 wt%, to obtain an organic solution of the functional polymer. Subsequently, zirconia with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconia is 10% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The remaining methods of preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0092] Comparative Example 3

[0093] The process and conditions are the same as those in Example 1. The difference is that after preparing the solution according to the method in step (1) of Example 1, zirconia with a particle size of 150 nm is added to the prepared organic solution, and the mass of zirconia is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The remaining methods of preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0094] Comparative Example 4

[0095] The process and conditions are the same as those in Example 1. The difference is that after preparing the solution according to the method in step (1) of Example 1, zirconia with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconia is 10% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The remaining methods of preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0096] Comparative Example 5

[0097] The process and conditions are the same as those in Example 1, except that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 10 mL of dimethylacetamide at a mass ratio of 94:6, with a solid content of 30 wt%, to obtain an organic solution of the functional polymer. Subsequently, zirconia with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconia is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The methods for preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0098] Comparative Example 6

[0099] The process and conditions are the same as those in Example 1, except that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 50:50, with a solid content of 30 wt%, to obtain an organic solution of the functional polymer. Subsequently, zirconia with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconia is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The methods for preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0100] Comparative Example 7

[0101] The process and conditions are the same as those in Example 1, except that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 20:80, with a solid content of 30 wt%, to obtain an organic solution of the functional polymer. Subsequently, zirconia with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconia is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The methods for preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0102] Comparative Example 8

[0103] The process and conditions are the same as those in Example 1, except that after obtaining the organic solution according to the methods in steps (1) and (2) of Example 1, the organic solution is doctor blade coated on a dust-free glass plate carrying a polyphenylene sulfide support mesh with 50 meshes, a size of 10 cm × 10 cm, and a thickness of 50 μm, and the doctor blade coating speed is 3 cm·s -1; After the doctor blade coating is completed, soak the film in water at room temperature for 20 min. After the soaking is completed, rinse the composite film thoroughly with water. The method of assembling the film into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery is the same as that in Example 1 for the rest.

[0104] Comparative Example 9

[0105] The process and conditions are the same as those in Example 1. The difference is that after obtaining the organic solution according to the methods of steps (1) and (2) in Example 1, the organic solution is doctor blade coated on a dust-free glass plate at a doctor blade coating speed of 0.5 cm·s -1 ; After the doctor blade coating is completed, soak the film in water at room temperature for 20 min. After the soaking is completed, rinse the composite film thoroughly with water. The method of assembling the film into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery is the same as that in Example 1 for the rest.

[0106] Comparative Example 10

[0107] The process and conditions are the same as those in Example 1. The difference is that after obtaining the organic solution according to the methods of steps (1) and (2) in Example 1, the organic solution is doctor blade coated on a dust-free glass plate carrying a polyphenylene sulfide support mesh with 50 meshes, a size of 10 cm×10 cm, and a thickness of 50 μm at a doctor blade coating speed of 0.5 cm·s -1 ; After the doctor blade coating is completed, air-dry the film at room temperature. The method of assembling the film into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery is the same as that in Example 1 for the rest.

[0108] Example 4

[0109] The process and conditions are the same as those in Example 1. The difference is that when preparing the solution according to the method of step (1) in Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 94:6, and the solid content is 30 wt% to prepare an organic solution of the functional polymer. Subsequently, magnesium oxide with a particle size of 50 nm is added to the prepared organic solution, and the mass of magnesium oxide is 50% of the total mass of the polymer in step (1); stir the solution at room temperature for 48 h. The method of preparing the membrane material by doctor blade coating and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery is the same as that in Example 1 for the rest.

[0110] Example 5

[0111] The process and conditions are the same as those in Example 1, except that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 94:6, with a solid content of 30 wt%, to prepare an organic solution of the functional polymer. Subsequently, titanium oxide with a particle size of 50 nm is added to the prepared organic solution, and the mass of titanium oxide is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The methods for preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0112] Example 6

[0113] The process and conditions are the same as those in Example 1, except that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 94:6, with a solid content of 30 wt%, to prepare an organic solution of the functional polymer. Subsequently, aluminum oxide with a particle size of 50 nm is added to the prepared organic solution, and the mass of aluminum oxide is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The methods for preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0114] Example 7

[0115] The process and conditions are the same as those in Example 1, except that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethylacetamide at a mass ratio of 80:20, with a solid content of 30 wt%, to prepare an organic solution of the functional polymer. Subsequently, zirconium oxide with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconium oxide is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The methods for preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0116] Example 8

[0117] The process and conditions are the same as those in Example 1, except that when preparing the solution according to the method in step (1) of Example 1, polyethersulfone and sulfonated polyether ether ketone (sulfonation degree of 100%) are dissolved in 30 mL of dimethyl sulfoxide at a mass ratio of 94:6, and the solid content is 30 wt%, to prepare an organic solution of the functional polymer. Subsequently, zirconia with a particle size of 50 nm is added to the prepared organic solution, and the mass of zirconia is 50% of the total mass of the polymer in step (1); the solution is stirred at room temperature for 48 h. The remaining methods for preparing the membrane material by the doctor blade method and assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0118] Example 9

[0119] The process and conditions are the same as those in Example 1, except that after preparing the organic solution according to the methods in steps (1) and (2) of Example 1, the organic solution is doctor-blade coated on a dust-free glass plate carrying an alkali-resistant glass fiber mesh with 50 meshes, a size of 10 cm × 10 cm, and a thickness of 50 μm, and the doctor-blade coating speed is 0.5 cm·s -1 ; after the doctor-blade coating is completed, the membrane is immersed in water at room temperature for 20 min. After the immersion is completed, the composite membrane is rinsed clean with water. The remaining methods for assembling the membrane into the alkaline water electrolysis hydrogen production device and the alkaline zinc-iron flow battery are the same as those in Example 1.

[0120] The test results of the membranes prepared in different examples and comparative examples are recorded in Table 2. By comparing the data, the following points can be determined:

[0121] (1) In Comparative Example 1, zirconia is not added, and the surface resistance is 0.465 Ω·cm 2 , which is higher than 0.251 Ω·cm of Example 1 2 ; it shows that the introduction of hydrophilic nanoparticles promotes the reduction of the membrane surface resistance. In Examples 2 and 3, the introduction amount of zirconia is changed (the introduction amount in Example 1 is 50%)), which are 60% and 40% respectively. The test results show that a slightly higher particle introduction amount can reduce the membrane surface resistance, but it will lead to a decrease in the Coulomb efficiency in the flow battery; while reducing the particle introduction amount will lead to an increase in the membrane surface resistance, a decrease in the electrolytic water efficiency and the voltage efficiency of the flow battery. If the introduction amount of zirconia is too low, such as the addition amount of zirconia in Comparative Example 2 is 10%, its voltage efficiency drops too much. The above results show that the doping amount of hydrophilic nanoparticles will affect the performance of the composite membrane. In Comparative Example 3, the size of the introduced zirconia particles is increased to 150 nm, and the surface resistance of the composite membrane increases. This is because when the particle size is too large, zirconia will agglomerate in the membrane, thus affecting the pore structure in the membrane and causing a part of the pore size to be smaller.

[0122] (2) In Examples 4 to 6, the doping amount was kept the same as that in Example 1, but the types of hydrophilic nanoparticles were changed to magnesium oxide, titanium oxide, and aluminum oxide, respectively. Different hydrophilic nanoparticles have different hydrophilicities. Therefore, after introducing the composite membrane, the hydrophilicities of the composite membranes are different. Different types of hydrophilic nanoparticles can affect the electrolysis efficiency of the composite membrane in an alkaline water electrolyzer and the Coulombic efficiency and voltage efficiency in an alkaline zinc-iron flow battery.

[0123] (3) In Comparative Example 4, the concentration of the membrane-forming solution was reduced to 10% (30% in Example 1). The surface resistance of the prepared membrane was slightly lower than that of the membrane prepared in Example 1. This is because reducing the concentration of the membrane-forming solution makes the solution thinner, increases the difficulty of membrane preparation, and the prepared membrane has poor uniformity and a reduced local thickness. Therefore, the Coulombic efficiency in the flow battery also decreased. This shows that there is a certain preferred range for the concentration of the membrane-forming solution, that is, there is a preferred range for the solid content of the polymer in the membrane-forming solution.

[0124] (4) In Comparative Example 5, the amount of the membrane-forming solution was changed, and the performance of the prepared membrane was not much different from that of the membrane prepared in Example 1. However, due to the large loss in the preparation of the membrane by the solvent phase inversion method, the available area of the prepared membrane decreased with a smaller amount of solvent in Comparative Example 5.

[0125] (5) In Comparative Examples 6 and 7, the proportion of the functional polymer was changed, and the surface resistance increased or the composite membrane had defects and could not be used, indicating that by regulating the composition of the functional polymer, its compatibility with the alkali-resistant polymer support network can be changed, and thus the surface resistance of the composite membrane can be changed.

[0126] (6) In Comparative Example 8, the casting speed was increased, and the prepared composite membrane had defects and could not be used. This shows that during the process of casting the composite membrane, if the casting speed is too fast, the distribution of the functional polymer on the alkali-resistant polymer support network will be uneven, affecting the performance of the composite membrane, and even causing local damage to the composite membrane and making it unusable.

[0127] (7) In Comparative Example 9, the alkali-resistant polymer support network was not introduced, and the tensile strength was only 18.7 MPa, indicating that the introduction of the alkali-resistant polymer support network can improve the mechanical strength of the composite membrane.

[0128] In Example 9, under the condition of ensuring the same mesh number, thickness, etc., the type of the alkali-resistant polymer support network was changed, and the performance of the composite membrane had little difference, indicating that different types of alkali-resistant polymer support networks have little difference in the influence on the surface resistance of the composite membrane and the performance of the corresponding alkaline system energy conversion and storage devices.

[0129] In Comparative Example 10, when other conditions are the same, the film is prepared by air-drying the membrane instead of the phase inversion method, and the surface resistance of the obtained film is relatively large because the slow evaporation of the solvent will make the film denser, and the reduction of the pore structure in the film will increase the difficulty of ion transmembrane transport.

[0130] Table 2

[0131]

[0132] As described above, the above are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications using the technical content disclosed above within the scope of the technical solution of the present application, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. An alkali-resistant composite porous separator, characterized in that, It includes an alkali-resistant polymer support mesh layer and a functional polymer layer; The functional polymer layer wraps the alkali-resistant polymer support mesh layer; Hydrophilic inorganic nanoparticles are dispersed in the functional polymer layer; The film thickness of the alkali-resistant composite porous separator is 30 to 700 μm.

2. The alkali-resistant composite porous separator according to claim 1, characterized in that, The functional polymer in the functional polymer layer includes a first type of functional polymer and a second type of functional polymer; The first type of functional polymer is a hydrophobic functional polymer; The second type of functional polymer is a hydrophilic functional polymer.

3. The alkali-resistant composite porous separator according to claim 2, characterized in that, The hydrophobic functional polymer is selected from any one or more of polyethersulfone, polysulfone, chloromethylated polysulfone, polyether ketone, and polyolefin; Preferably, the hydrophobic functional polymer is polyethersulfone; The hydrophilic functional polymer is selected from any one or more of sulfonated polyether ether ketone, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, and sulfonated polystyrene; Preferably, the hydrophilic functional polymer is sulfonated polyether ether ketone.

4. The alkali-resistant composite porous separator according to claim 2, characterized in that, The mass ratio of the first type of functional polymer to the second type of functional polymer is 99:1 to 70:

30.

5. The alkali-resistant composite porous separator according to claim 1, characterized in that, The hydrophilic inorganic nanoparticles are selected from any one or more of zirconia, titania, alumina, and magnesia; The diameter of the hydrophilic inorganic nanoparticles is 10 to 100 nm; The mass of the hydrophilic inorganic nanoparticles is 20 to 70% of the functional polymer.

6. The alkali-resistant composite porous separator according to claim 1, characterized in that, The alkali-resistant polymer support mesh of the alkali-resistant polymer support mesh layer is selected from any one or more of polyphenylene sulfide mesh, polyurea mesh, and alkali-resistant glass fiber mesh; The mesh number of the alkali-resistant polymer support mesh is 10 to 200 mesh; The thickness of the alkali-resistant polymer support mesh is 10 to 100 μm.

7. A method for preparing the alkali-resistant composite porous separator according to any one of claims 1 to 6, characterized in that, It includes: A mixture of a functional polymer, hydrophilic inorganic nanoparticles, and an organic solvent is stirred to obtain a mixed solution, which is coated on a dust-free glass plate carrying an alkali-resistant polymer support mesh and immersed in water to obtain the alkali-resistant composite porous separator.

8. The method for preparing the alkali-resistant composite porous separator according to claim 7, characterized in that, The solid content of the functional polymer in the functional polymer solution is 10 to 50 wt%; the functional polymer solution includes a functional polymer and an organic solvent; The functional polymer includes a first type of functional polymer and a second type of functional polymer; The first type of functional polymer is a hydrophobic functional polymer; The second type of functional polymer is a hydrophilic functional polymer; The hydrophobic functional polymer is selected from any one or more of polyethersulfone, polysulfone, chloromethylated polysulfone, polyether ketone, and polyolefin; The hydrophilic functional polymer is selected from any one or more of sulfonated polyether ether ketone, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, and sulfonated polystyrene; The mass ratio of the first type of functional polymer to the second type of functional polymer is 99:1 to 70:30; The organic solvent is selected from any one or more of dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

9. The method for preparing the alkali-resistant composite porous separator according to claim 7, characterized in that, The coating method is doctor blade coating; The speed of scraping coating is 0.1 - 1 cm·s -1 .

10. Use of the alkali-resistant composite porous separator according to any one of claims 1 to 6 in an energy conversion and storage device in an alkaline system.

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