A sulfonated polystyrene / polyolefin microporous composite membrane, a preparation method thereof, and an application thereof

Abstract

The present invention proposes a sulfonated polystyrene / polyolefin microporous composite membrane and its preparation method and application, belonging to the field of composite material technology. The method comprises the following steps: S1. dissolving chlorosulfonic acid in an organic solvent to obtain a sulfonated liquid; adding the sulfonated liquid dropwise to a polystyrene solution for reaction, adding water for distillation to remove the solvent, washing, and drying to obtain a sulfonated polystyrene; S2. placing a hydrophilic surface treatment liquid and a porous membrane in a high-pressure container, heating and maintaining, cooling, and drying to obtain a hydrophilic membrane; S3. placing the hydrophilic membrane on a horizontal glass plate, pouring a sulfonated polystyrene casting liquid on it to make the casting liquid uniform in thickness, placing it on the plate, drying, and obtaining a sulfonated polystyrene / polyolefin microporous membrane composite membrane. The present invention directly uses polystyrene resin as the main raw material, has a simple preparation process, and is low in cost. The obtained sulfonated polystyrene / polyolefin microporous membrane cross-linked composite membrane has broad practical prospects in the field of Fe / Cr liquid flow batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a sulfonated polystyrene / polyolefin microporous composite membrane and a preparation method and application thereof. Background Art

[0002] Traditional fossil energy represented by coal and oil is a non-renewable energy source. With the massive consumption of fossil energy, energy shortages and environmental pollution caused by the combustion of fossil energy are becoming increasingly serious. There is an urgent need to develop clean energy technologies.

[0003] Fe-Cr flow batteries were first studied by NASA in the 1970s. As an ideal energy storage technology, they are gaining increasing importance in clean energy systems such as wind power generation and photovoltaic power generation. The proton exchange membrane is one of the core components of the Fe / Cr flow battery. Its function is to separate the anode and cathode, conduct protons and insulate electrons. Currently, the proton exchange membrane is widely used in Nafion produced by DuPont in the United States, but this material is expensive (US$600-800 / m 2 ) limits its application in redox flow batteries. Therefore, developing proton exchange membranes with low cost, high proton conductivity, low iron ion permeability (low swelling rate), good mechanical properties, and high chemical stability is of great significance to promote the widespread application of Fe / Cr redox flow battery technology.

[0004] Polystyrene is a general-purpose engineering plastic with extremely low cost. Sulfonated polystyrene is produced by post-sulfonation of polystyrene or polymerization of sodium styrene sulfonate monomers. As an important type of ion exchange resin, sulfonated polystyrene has been widely used in industry. In addition, by controlling the ion exchange capacity, research on the use of sulfonated polystyrene as a proton exchange membrane for fuel cells has also been reported. For example, an international paper (J. Membr. Sci. 2000, 166, 189-197) reported that when the sulfonation degree of sulfonated polystyrene is controlled at 17-20%, its ion exchange capacity is 1.33-1.41 meq / g, and this membrane has a high proton conductivity (4.3-8.6×10 -2 S / cm, tested at 60°C in water). However, sulfonated polystyrene membranes have poor toughness, and to further increase the membrane's proton conductivity (for example, greater than 0.1 S / cm), its ion exchange capacity must be increased. However, excessive ion exchange capacity can lead to excessive swelling in water, greatly limiting its practical application.

[0005] To improve the toughness of sulfonated polystyrene membranes and reduce their swelling rate, compounding sulfonated polystyrene with other materials and cross-linking them to prepare cross-linked composite membranes is an effective method. To date, there are few reports on cross-linked sulfonated polystyrene composite membranes. An international paper (J. Membr. Sci. 251, (2005) 247–254) reported a method for preparing a cross-linked sulfonated polystyrene / polytetrafluoroethylene composite membrane: First, a polytetrafluoroethylene microporous membrane is immersed in a uniform reaction mixture containing styrene (monomer), p-divinylbenzene (cross-linking agent), and an initiator under a nitrogen atmosphere. The polytetrafluoroethylene microporous membrane, soaked in the reaction mixture, is then placed in a special apparatus for polymerization. After the polymerization reaction, the membrane undergoes a complex purification process to obtain a cross-linked polystyrene / tetrafluoroethylene composite membrane. Finally, the cross-linked composite membrane is swollen with dichloroethane and then post-sulfonated using chlorosulfonic acid as a sulfonation reagent to obtain a cross-linked sulfonated polystyrene / tetrafluoroethylene composite membrane. However, this method has obvious defects such as complex preparation process and equipment, harsh sulfonation conditions, difficulty in controlling the sulfonation degree and reaction uniformity of the membrane, and the inability to directly use polystyrene resin as raw material, which results in a significant increase in preparation costs.

[0006] Chinese patent CN201410838676.8 provides a method for preparing a sulfonated polystyrene / polyolefin microporous cross-linked composite membrane. This method uses highly sulfonated polystyrene to coat the micropores of a porous polyolefin, which is then cross-linked with phosphorus pentoxide to form an ion exchange membrane. However, the disadvantage is that highly sulfonated polystyrene is water-soluble, making it difficult for phosphorus pentoxide to cross-link it with the polyolefin. Consequently, when used in aqueous solutions, the sulfonic acid groups are lost, ultimately resulting in a loss of ion exchange functionality.

[0007] Therefore, developing a method for preparing a sulfonated polystyrene cross-linked composite membrane using polystyrene resin as the main raw material and having a simple preparation process has broad market prospects. Summary of the Invention

[0008] The purpose of the present invention is to propose a sulfonated polystyrene / polyolefin microporous composite membrane and its preparation method and application. Polystyrene resin is directly used as the main raw material, the preparation process is simple, and the cost is low. The prepared sulfonated polystyrene / polyolefin microporous membrane cross-linked composite membrane has broad practical prospects in the field of Fe / Cr liquid flow batteries.

[0009] The technical solution of the present invention is achieved as follows:

[0010] The present invention provides a method for preparing a sulfonated polystyrene / polyolefin microporous composite membrane, comprising the following steps:

[0011] S1. Preparation of sulfonated polystyrene:

[0012] Dissolve chlorosulfonic acid in an organic solvent and stir at room temperature for 1-2 hours to obtain a sulfonated solution; add the obtained sulfonated solution dropwise to a polystyrene solution to react; add water to the reaction mixture and distill to remove the solvent, wash, and dry to obtain sulfonated polystyrene;

[0013] S2. Surface hydrophilic treatment of polyolefin microporous membrane:

[0014] The hydrophilic surface treatment liquid and the porous membrane are placed in a high-pressure container, heated to 80-95°C, maintained for 5-30 minutes, cooled, the porous membrane is taken out, and dried to obtain a hydrophilic membrane;

[0015] S3. Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane:

[0016] Place the hydrophilic membrane on a horizontal glass plate, pour sulfonated polystyrene casting solution on it, use a scraping device to make the casting solution thickness uniform, place it for 0-5min, dry it at 40-70℃, and then dry it at 80-110℃ to obtain a sulfonated polystyrene / polyolefin microporous membrane composite membrane.

[0017] As a further improvement of the present invention, the organic solvent in step S1 is 1,2-dichloroethane; the solvent in the polystyrene solution is 1,2-dichloroethane; and the volume ratio of the chlorosulfonic acid to the organic solvent is 1:5-20.

[0018] As a further improvement of the present invention, the reaction temperature in step S1 is 40-80° C., and the reaction time is 3-30 h.

[0019] As a further improvement of the present invention, the sulfonation degree of the sulfonated polystyrene in step S1 is 10-35%.

[0020] As a further improvement of the present invention, the hydrophilic surface treatment liquid in step S2 is prepared from the following raw materials in weight percentage: 85-95% solvent, 2-13% hydrophilic reactant, and 0.1-1% catalyst; the preparation method is: mixing the components and stirring for 10-30 minutes to dissolve; the solvent is one or a mixture of two or more of methanol, ethanol, or isopropanol; the hydrophilic reactant is a monofunctional or multifunctional acrylate, or a mixture thereof; the catalyst is a peroxide selected from ammonium persulfate, potassium persulfate, sodium persulfate, and benzoyl peroxide.

[0021] As a further improvement of the present invention, the porous membrane in step S2 is a polytetrafluoroethylene microporous membrane, a polyethylene microporous membrane or a polypropylene microporous membrane, and the porous membrane has a pore size of 0.05-5 μm, a porosity of 30-90%, and a membrane thickness of 10-1000 μm.

[0022] As a further improvement of the present invention, the sulfonated polystyrene casting solution in step S3 is an alcohol solution containing 1-10 wt% of sulfonated polystyrene, and the alcohol is one of methanol, ethanol, and isopropanol, or a mixture of two or more thereof.

[0023] As a further improvement of the present invention, the drying atmosphere in step S3 is a vacuum atmosphere or an inert atmosphere, and the inert atmosphere is a nitrogen or argon atmosphere.

[0024] The present invention further protects a sulfonated polystyrene / polyolefin microporous composite membrane prepared by the above preparation method.

[0025] The present invention further protects the use of the above-mentioned sulfonated polystyrene / polyolefin microporous composite membrane as an ion exchange membrane for Fe / Cr liquid flow batteries.

[0026] The present invention has the following beneficial effects: the sulfonated polystyrene / polyolefin microporous membrane cross-linked composite membrane of the present invention directly uses polystyrene resin as the main raw material, has a simple preparation process and low cost, and the prepared sulfonated polystyrene / polyolefin microporous membrane cross-linked composite membrane has broad practical prospects in the field of Fe / Cr liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is the charge and discharge curve of the single cell assembled with the membrane in Example 2 of the present invention;

[0029] Figure 2 This is the charge and discharge curve of a single cell assembled with the membrane in Example 4 of the present invention. DETAILED DESCRIPTION

[0030] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] Example 1

[0032] S1. Preparation of sulfonated polystyrene:

[0033] 1) Preparation of sulfonated liquid: 300 g of 1,2-dichloroethane was weighed into a three-necked flask with a rotor and stirred under nitrogen protection. Then 30 g of chlorosulfonic acid was added dropwise and mixed thoroughly to obtain 330 g of sulfonated liquid.

[0034] 2) Preparation of 28% sulfonated polystyrene

[0035] Weigh 2200g of 1,2-dichloroethane and add 100g of polystyrene while stirring. Slowly raise the temperature to 50°C and stir for 2-3 hours until completely dissolved. Control the temperature at 50-60°C and add the sulfonation solution dropwise. Add the solution dropwise within 2 hours, allowing the product to gradually precipitate. Continue stirring and react for 5 hours. Allow the mixture to stand overnight, filter out the dichloroethane, and obtain the crude product. Re-evaporate the dichloroethane, dry it, and reuse it. Air-dry the crude product, dry it under reduced pressure, and pulverize it to obtain the finished product, with a measured degree of sulfonation of approximately 28%.

[0036] S2. Surface hydrophilic treatment of polyolefin microporous membrane

[0037] In a beaker, add 93.5g of ethanol and stir. Then, add 4.0g of hydroxypropyl methacrylate, 1.0g of trimethylolpropane triacrylate, 1.0g of BPO, and 0.5g of 84 disinfectant in that order and stir for 15 minutes. Add all of these liquids into an autoclave along with the polypropylene microporous membrane. Seal the autoclave. Raise the temperature to 90-95°C and hold for 30 minutes until the reaction is complete. After cooling, open the autoclave, remove the membrane, and dry it to obtain a hydrophilic membrane.

[0038] S3. Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane:

[0039] 1) Configuration of 3.5wt% sulfonated polystyrene casting solution:

[0040] A 3.5 wt % sulfonated polystyrene casting solution was prepared with sulfonated polystyrene as solute and ethanol as solvent.

[0041] 2) Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane

[0042] A hydrophilic-treated polyolefin microporous membrane was placed on a horizontal glass plate. A polysulfonated styrene casting solution was poured onto the membrane. A scraping device was used to ensure a uniform thickness of the polysulfonated styrene casting solution. The membrane was then dried for 3 minutes at 70°C and then at 90°C to produce a polysulfonated styrene / polyolefin microporous membrane composite.

[0043] Example 2

[0044] S1. Preparation of sulfonated polystyrene:

[0045] 1) Preparation of sulfonated liquid: 260 g of 1,2-dichloroethane was weighed into a three-necked flask with a rotor and stirred under nitrogen protection. Then 26.2 g of chlorosulfonic acid was added dropwise and mixed thoroughly to obtain 266.2 g of sulfonated liquid.

[0046] 2) Preparation of 18% sulfonated polystyrene

[0047] Weigh 2200g of 1,2-dichloroethane, add 100g of polystyrene while stirring, slowly raise the temperature to 50°C, stir for 2-3h, and completely dissolve; control the temperature at 50-60°C, add the sulfonation liquid dropwise, and control the addition to be completed within 2h. During the addition, the product gradually precipitates. After the addition is completed, continue stirring and react for 5h; after the reaction, add 1000g of pure water, concentrate most of the 1,2-dichloroethane, filter out the crude product, wash with pure water, filter out, dry under vacuum, and crush to obtain the finished product. The measured sulfonation degree is about 18%.

[0048] S2. Surface hydrophilic treatment of polyolefin microporous membrane

[0049] In a beaker, add 93.5g of ethanol and stir. Then, add 4.0g of hydroxypropyl methacrylate, 1.0g of trimethylolpropane triacrylate, 1.0g of BPO, and 0.5g of 84 disinfectant in that order and stir for 15 minutes. Add all of these liquids into an autoclave along with the polypropylene microporous membrane. Seal the autoclave. Raise the temperature to 90-95°C and hold for 30 minutes until the reaction is complete. After cooling, open the autoclave, remove the membrane, and dry it to obtain a hydrophilic membrane.

[0050] S3. Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane:

[0051] 1) Configuration of 3.5wt% sulfonated polystyrene casting solution:

[0052] A 3.5 wt % sulfonated polystyrene casting solution was prepared with sulfonated polystyrene as solute and ethanol as solvent.

[0053] 2) Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane

[0054] A hydrophilic-treated polyolefin microporous membrane was placed on a horizontal glass plate. A polysulfonated styrene casting solution was poured onto the membrane. A scraping device was used to ensure a uniform thickness of the polysulfonated styrene casting solution. The membrane was then dried for 3 minutes at 70°C and then at 90°C to produce a polysulfonated styrene / polyolefin microporous membrane composite.

[0055] Example 3

[0056] S1. Preparation of sulfonated polystyrene:

[0057] 1) Preparation of sulfonated liquid: 300 g of 1,2-dichloroethane was weighed into a three-necked flask with a rotor and stirred under nitrogen protection. Then 30 g of chlorosulfonic acid was added dropwise and mixed thoroughly to obtain 330 g of sulfonated liquid.

[0058] 2) Preparation of 28% sulfonated polystyrene

[0059] Weigh 2200g of 1,2-dichloroethane and add 100g of polystyrene while stirring. Slowly raise the temperature to 50°C and stir for 2-3 hours until completely dissolved. Control the temperature at 50-60°C and add the sulfonation solution dropwise. Add the solution dropwise within 2 hours, allowing the product to gradually precipitate. Continue stirring and react for 5 hours. Allow the mixture to stand overnight, filter out the dichloroethane, and obtain the crude product. Re-evaporate the dichloroethane, dry it, and reuse it. Air-dry the crude product, dry it under reduced pressure, and pulverize it to obtain the finished product, with a measured degree of sulfonation of approximately 28%.

[0060] S2. Surface hydrophilic treatment of polyolefin microporous membrane

[0061] In a beaker, add 93.5g of ethanol and stir. Then, add 4.0g of hydroxypropyl methacrylate, 1.0g of trimethylolpropane triacrylate, 1.0g of BPO, and 0.5g of 84 disinfectant in that order and stir for 15 minutes. Add all of these liquids into an autoclave along with the polypropylene microporous membrane. Seal the autoclave. Raise the temperature to 90-95°C and hold for 30 minutes until the reaction is complete. After cooling, open the autoclave, remove the membrane, and dry it to obtain a hydrophilic membrane.

[0062] S3. Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane:

[0063] 1) Configuration of 4wt% sulfonated polystyrene casting solution:

[0064] A 4 wt % sulfonated polystyrene casting solution was prepared with sulfonated polystyrene as solute and ethanol as solvent.

[0065] 2) Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane

[0066] A hydrophilic-treated polyolefin microporous membrane was placed on a horizontal glass plate. A polysulfonated styrene casting solution was poured onto the membrane. A scraping device was used to ensure a uniform thickness of the polysulfonated styrene casting solution. The membrane was then dried for 3 minutes at 70°C and then at 90°C to produce a polysulfonated styrene / polyolefin microporous membrane composite.

[0067] Example 4

[0068] S1. Preparation of sulfonated polystyrene:

[0069] 1) Preparation of sulfonated liquid: 260 g of 1,2-dichloroethane was weighed into a three-necked flask with a rotor and stirred under nitrogen protection. Then 26.2 g of chlorosulfonic acid was added dropwise and mixed thoroughly to obtain 286.2 g of sulfonated liquid.

[0070] 2) Preparation of 28% sulfonated polystyrene

[0071] Weigh 2200g of 1,2-dichloroethane, add 100g of polystyrene while stirring, slowly raise the temperature to 50°C, stir for 2-3h, and completely dissolve; control the temperature at 50-60°C, add the sulfonation liquid dropwise, and control the addition to be completed within 2h. During the addition, the product gradually precipitates. After the addition is completed, continue stirring and react for 5h; after the end, add 1000g of pure water, concentrate most of the 1,2-dichloroethane, filter out the crude product, wash with pure water, filter out, dry under vacuum, and crush to obtain the finished product. The measured sulfonation degree is about 18%.

[0072] S2. Surface hydrophilic treatment of polyolefin microporous membrane

[0073] In a beaker, add 93.5g of ethanol and stir. Then, add 4.0g of hydroxypropyl methacrylate, 1.0g of trimethylolpropane triacrylate, 1.0g of BPO, and 0.5g of 84 disinfectant in that order and stir for 15 minutes. Add all of these liquids into an autoclave along with the polypropylene microporous membrane. Seal the autoclave. Raise the temperature to 90-95°C and hold for 30 minutes until the reaction is complete. After cooling, open the autoclave, remove the membrane, and dry it to obtain a hydrophilic membrane.

[0074] S3. Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane:

[0075] 1) Configuration of 4wt% sulfonated polystyrene casting solution:

[0076] A 4 wt % sulfonated polystyrene casting solution was prepared with sulfonated polystyrene as solute and ethanol as solvent.

[0077] 2) Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane

[0078] A hydrophilic-treated polyolefin microporous membrane was placed on a horizontal glass plate. A polysulfonated styrene casting solution was poured onto the membrane. A scraping device was used to ensure a uniform thickness of the polysulfonated styrene casting solution. The membrane was then dried for 3 minutes at 70°C and then at 90°C to produce a polysulfonated styrene / polyolefin microporous membrane composite.

[0079] Application Example 1Fe / Cr flow battery performance test

[0080] The composite membranes prepared in Examples 2 and 4 of the present invention were used as ion exchange membranes in Fe / Cr flow batteries to test their performance in charge and discharge experiments. The positive and negative electrolytes were equal volumes of FeCl2+CrCl3+HCl solutions; the positive and negative electrodes were treated graphite carbon felt. The charge and discharge current was 100 mA / cm 2 , charging cut-off voltage 1.25V, discharging cut-off voltage 0.3V. Test results are shown in Figure 1-2 The coulombic efficiencies are 94.8% and 95.3% respectively; the voltage efficiencies are 80.4% and 80.3% respectively.

[0081] Test Example 1 Performance Test

[0082] The tensile test was carried out on an Instron 4465 universal electronic tensile testing machine, with an ambient relative humidity of 80% and a tensile rate of 2 mm / min.

[0083] Membrane conductivity was measured using the impedance method. Both sides of the membrane were immersed in 3M hydrochloric acid and the impedance was measured at 20°C using a VSP-300 electrochemical workstation. The frequencies used ranged from 100 Hz to 100 kHz. Proton conductivity (σ) was calculated using the following formula:

[0084] σ=D / (LBR) (1)

[0085] Where D is the distance between the two electrodes, L and B are the thickness and width of the film when it reaches swelling equilibrium in deionized water, and R is the measured film impedance.

[0086] The water absorption and dimensional stability test method is to soak three films (each film weighing approximately 0.1-0.2g) in deionized water at 20℃ for 24 hours. The films are then removed, the surface moisture is absorbed with filter paper, and the film is quickly weighed on an electronic balance. The water absorption rate WU of the film is calculated using the following formula:

[0087] W U =(W s –W d ) / W d ×100(%) (2)

[0088] Where W d and W s are the masses of the film in dry and wet states, respectively. The water absorption rate of the film is the average value of three films.

[0089] The dimensional change in the film plane direction (ΔL) is calculated by the following formula:

[0090] ΔL=(L1–L0) / L0×100(%) (3)

[0091] Where L1 and L0 are the lengths of the film in dry and wet states, respectively.

[0092] The dimensional change in the film thickness direction (ΔB) is calculated using the following formula:

[0093] ΔB=(B1–B0) / t0×100(%) (4)

[0094] Where B1 and B0 are the thickness of the film in dry and wet states, respectively.

[0095] Table 1 lists the main properties of the prepared sulfonated polystyrene / polypropylene microporous membrane composite membrane, including tensile strength, elongation at break, water absorption, swelling ratio and proton conductivity.

[0096] Table 1

[0097]

[0098] Note: “-” in the table means unmeasurable; ΔL refers to the rate of change in the film plane direction, and ΔB refers to the rate of change in the film thickness direction.

[0099] Compared with the existing technology, the sulfonated polystyrene / polyolefin microporous membrane cross-linked composite membrane of the present invention directly uses polystyrene resin as the main raw material, has a simple preparation process and low cost, and the prepared sulfonated polystyrene / polyolefin microporous membrane cross-linked composite membrane has broad practical prospects in the field of Fe / Cr liquid flow batteries.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a sulfonated polystyrene / polyolefin microporous composite membrane, characterized in that: The following steps are involved: S1. Preparation of sulfonated polystyrene: Dissolve chlorosulfonic acid in an organic solvent and stir at room temperature for 1-2 hours to obtain a sulfonated solution; add the obtained sulfonated solution dropwise to a polystyrene solution to react; add water to the reaction mixture and distill to remove the solvent, wash, and dry to obtain sulfonated polystyrene; S2. Surface hydrophilic treatment of polyolefin microporous membrane: The hydrophilic surface treatment liquid and the porous membrane are placed in a high-pressure container, heated to 80-95°C, maintained for 5-30 minutes, cooled, the porous membrane is taken out, and dried to obtain a hydrophilic membrane; S3. Preparation of sulfonated polystyrene / polyolefin microporous membrane composite membrane: Place the hydrophilic membrane on a horizontal glass plate, pour a sulfonated polystyrene casting solution on it, use a scraping device to make the casting solution thickness uniform, place it for 0-5 minutes, dry it at 40-70°C, and then dry it at 80-110°C to obtain a sulfonated polystyrene / polyolefin microporous membrane composite membrane; The organic solvent in step S1 is 1,2-dichloroethane; the solvent in the polystyrene solution is 1,2-dichloroethane; the volume ratio of chlorosulfonic acid to the organic solvent is 1:5-20; The reaction temperature in step S1 is 40-80° C., and the reaction time is 3-30 h; The degree of sulfonation of the sulfonated polystyrene in step S1 is 10-35%; The sulfonated polystyrene casting solution in step S3 is an alcohol solution containing 1-10 wt% of sulfonated polystyrene, and the alcohol is one of methanol, ethanol, and isopropanol, or a mixture of two or more thereof.

2. The preparation method according to claim 1, characterized in that The hydrophilic surface treatment liquid in step S2 is prepared from the following raw materials by weight percentage: 85-95% solvent, 2-13% hydrophilic reactant, and 0.1-1% catalyst; the preparation method is: mixing the components and stirring for 10-30 minutes to dissolve; the solvent is one or a mixture of two or more of methanol, ethanol, or isopropanol; the hydrophilic reactant is a monofunctional or multifunctional acrylate, or a mixture thereof; and the catalyst is selected from ammonium persulfate, potassium persulfate, sodium persulfate, and benzoyl peroxide.

3. The preparation method according to claim 1, characterized in that The porous membrane in step S2 is a polytetrafluoroethylene microporous membrane, a polyethylene microporous membrane or a polypropylene microporous membrane, and the porous membrane has a pore size of 0.05-5 μm, a porosity of 30-90%, and a membrane thickness of 10-1000 μm.

4. The preparation method according to claim 1, characterized in that The drying atmosphere in step S3 is a vacuum atmosphere or an inert atmosphere, and the inert atmosphere is a nitrogen or argon atmosphere.

5. A sulfonated polystyrene / polyolefin microporous composite membrane prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the sulfonated polystyrene / polyolefin microporous composite membrane as claimed in claim 5 as an ion exchange membrane for Fe / Cr redox flow batteries.

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