Composite proton exchange membrane with high proton conductivity as well as preparation method and application of composite proton exchange membrane

Abstract

The invention belongs to the technical field of flow batteries, and discloses a composite proton exchange membrane with high proton conductivity and a preparation method and application thereof. The preparation method of the composite proton exchange membrane comprises the following steps: S1, carrying out Michael addition reaction on polyethyleneimine and diethyl 2-bromoethyl phosphonate, and carrying out hydrolysis, dialysis and freeze-drying on the reacted product to obtain a partially phosphorylated polyethyleneimine oligomer; s2, mixing the partially phosphorylated polyethyleneimine oligomer, proton exchange resin containing sulfonic groups and a solvent to obtain a membrane casting solution; s3, the membrane casting solution forms a membrane, and the composite proton exchange membrane is obtained. The composite proton exchange membrane prepared by the method has excellent proton conductivity, high ion selectivity and low swelling property.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, and specifically relates to a composite proton exchange membrane with high proton conductivity, its preparation method, and its application. Background Technology

[0002] Traditional fossil fuels face the crisis of energy depletion and generate environmental problems such as pollution during their use, including exacerbating the greenhouse effect, causing acid rain, and depleting the ozone layer. Therefore, vigorously developing new energy sources is a crucial trend in current development. There are many types of new energy sources, among which wind and solar power have attracted significant attention due to their inherent characteristics. However, the volatility and other inherent limitations of wind and solar power significantly restrict their development. Energy storage technologies and systems, characterized by mature technology, stable operation, and long service life, have become the preferred choice for the application of intermittent new energy sources. During power generation, electrical energy is converted into other forms of energy and stored through energy storage devices; when needed, this other form of energy is then converted back into electrical energy.

[0003] Compared to physical energy storage, chemical energy storage offers advantages such as ease of large-scale production and long service life. Currently, flow batteries are one of the most widely used chemical energy storage technologies, boasting mature technology, large-scale production capacity, rapid response, deep charge / discharge capability, and long service life. Therefore, flow battery technology has immense application prospects in energy storage and is of great significance to the sustainable development of new energy sources. The proton exchange membrane (PEM) is a core component of flow batteries, and its properties play a crucial role in the battery's performance. Developing PEMs with high proton conductivity, high selectivity, and low swelling remains a primary research objective. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention provides a composite proton exchange membrane with high proton conductivity, its preparation method and application, wherein the composite proton exchange membrane possesses excellent proton conductivity, high ion selectivity and low swelling.

[0005] In a first aspect, the present invention provides a method for preparing a composite proton exchange membrane, comprising the following steps: S1. Polyethyleneimine is subjected to a Michael addition reaction with diethyl 2-bromoethylphosphonate. The product after the reaction is hydrolyzed, dialyzed and lyophilized to obtain a partially phosphorylated polyethyleneimine oligomer. S2. The partially phosphorylated polyethyleneimine oligomer, the proton exchange resin containing sulfonic acid groups, and the solvent are mixed to obtain a casting solution. S3. The casting solution is used to form a film to obtain the composite proton exchange membrane.

[0006] Preferably, the partially phosphorylated polyethyleneimine oligomer has any of the following structural formulas: , , ; Wherein, n is 23-1628. Preferably, n is 30-100, more preferably, n is 40-60.

[0007] Preferably, the weight-average molecular weight (Mw) of the polyethyleneimine is 1,000-70,000; more preferably, the weight-average molecular weight of the polyethyleneimine is 1,000-10,000; and even more preferably, the weight-average molecular weight of the polyethyleneimine is 1,000-3,000.

[0008] Preferably, the partially phosphorylated polyethyleneimine oligomer contains phosphate groups and active sites NH, wherein the molar ratio of the phosphate groups to the active sites NH is 1:(0.5-5). This ratio can be any point value or any two points within the range of 1:(0.5-5), such as 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, etc.

[0009] Preferably, the proton exchange resin containing sulfonic acid groups includes at least one of perfluorosulfonic acid resin, sulfonated polyether ether ketone, and sulfonated polyether sulfone.

[0010] Preferably, the partially phosphorylated polyethyleneimine oligomer accounts for 0.5%-5% of the mass fraction of the composite proton exchange membrane. This mass fraction can be any point value or any two points within the range of 0.5%-5%, such as 0.5%, 1%, 2%, 3%, 4%, 5%, etc.

[0011] Preferably, the Michael addition reaction in step S1 is carried out at a temperature of 60-100°C.

[0012] Preferably, the Michael addition reaction is carried out under an inert gas atmosphere.

[0013] Preferably, the inert gas is selected from at least one of nitrogen, argon, and xenon.

[0014] Preferably, the Michael addition reaction takes 24-72 hours.

[0015] Preferably, the Michael addition reaction is carried out under alkaline conditions.

[0016] Preferably, the alkaline substance used in the alkaline conditions includes Cs2CO3.

[0017] Preferably, the molar ratio of polyethyleneimine to diethyl 2-bromoethylphosphonate is 1:(30-33).

[0018] Preferably, the molar ratio of polyethyleneimine to Cs2CO3 is 1:(40-43).

[0019] Preferably, the mass ratio of the partially phosphorylated polyethyleneimine oligomer to the proton exchange resin containing sulfonic acid groups is 1:(19-99).

[0020] Preferably, the hydrolysis is carried out under acidic conditions.

[0021] Preferably, the acidic substance used in the acidic conditions includes a hydrochloric acid solution.

[0022] Preferably, the concentration of the hydrochloric acid solution is 2-4 mol / L.

[0023] Preferably, the hydrolysis time is 24-72 hours.

[0024] Preferably, the dialysis is performed using a dialysis bag with a molecular weight cutoff of 800-1200 Da.

[0025] Preferably, the dialysis time is 48-120 hours; more preferably, the dialysis time is 48-96 hours.

[0026] Preferably, the solvent comprises water and / or N,N-dimethylformamide (DMF).

[0027] Preferably, in step S3, after the casting solution forms a film, the resulting film is further subjected to annealing and post-treatment.

[0028] Preferably, the annealing temperature is 150-190℃.

[0029] Preferably, the annealing process takes 2-6 hours.

[0030] Preferably, the post-treatment process includes: immersing the annealed membrane in a 0.5-1 mol / L H2SO4 solution for 0.5-2 h at 80°C, then immersing it in water for 0.5-2 h, and repeating the H2SO4 solution immersion and water immersion 2-3 times.

[0031] In a second aspect, the present invention provides a composite proton exchange membrane, which is prepared by the preparation method described in the first aspect of the present invention.

[0032] Preferably, the thickness of the composite proton exchange membrane is 20-30 μm.

[0033] In a third aspect, the present invention provides a flow battery comprising the composite proton exchange membrane described in the second aspect of the present invention.

[0034] Preferably, the flow battery is a vanadium redox flow battery.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention prepares a partially phosphorylated polyethyleneimine oligomer (PA-PEI) by grafting phosphate groups onto polyethyleneimine (PEI). By partially phosphorylating polyethyleneimine, the excessively dense active sites NH of polyethyleneimine can be prevented from reacting excessively with the sulfonic acid groups on the proton exchange resin, thus preventing gelation. In addition, the electrostatic interaction between the imino groups on the surface of PA-PEI and the sulfonic acid groups in the proton exchange resin induces the rearrangement of the side chains of the proton exchange resin, strengthens the microphase separation structure of the proton exchange membrane and constructs a confined proton fast transport channel. The presence of the "acid-base pair" also plays a role in physical cross-linking, which can effectively inhibit the excessive swelling of the proton exchange membrane under aqueous conditions.

[0036] (2) The composite proton exchange membrane prepared by this invention has excellent proton conductivity, high ion selectivity and low swelling, wherein the proton conductivity at 30℃ is 0.1-0.15 S·cm. -1 The vanadium ion permeability is (0.7-1.5)×10⁻⁶. -7 cm 2 ·min -1 The vanadium ion selectivity is (10.2-12.8)×10⁻⁶. 4 S·min / cm 3 . Attached Figure Description

[0037] Figure 1 For PEI and PA-PEI in Example 1 1 H NMR spectrum and 13 C NMR spectrum; Figure 2 The FTIR spectrum of PA-PEI in Example 1; Figure 3 The graph shows a comparison of the proton conductivity of the proton exchange membranes prepared in Examples 1-3 and Comparative Examples 1-2 at different temperatures. Detailed Implementation

[0038] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0039] Example 1 A method for preparing a composite proton exchange membrane includes the following steps: S1. Dissolve 1 g (0.55 mmol) of polyethyleneimine (Mw = 1800) in 50 mL of deionized water, then add 7.57 g (23.25 mmol) of Cs₂CO₃ and stir magnetically until completely dissolved to obtain a mixture. Transfer the mixture to an 80°C water bath, and then slowly add 4.274 g (17.44 mmol) of diethyl 2-bromoethylphosphonate dropwise to the mixture using a dropping funnel. React under a N₂ atmosphere for 48 h. After the reaction is complete, remove the liquid and pour it into a container. The crude product was obtained by stirring in 80 mL of 3 mol / L dilute hydrochloric acid solution for 48 h. To remove excess monomer and small molecule impurities, the crude product was poured into a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 72 h. The dialysis process was repeated three times. Finally, the liquid in the dialysis bag was collected and freeze-dried to obtain partially phosphorylated polyethyleneimine oligomer (solid PA-PEI product). The molar ratio of phosphate groups to active site NH in the solid PA-PEI product was 1:0.67. The specific structural formula of PA-PEI is as follows:

[0040] Where n=42.

[0041] S2. Dissolve 3.345g of solid PA-PEI product in 20mL of deionized water and stir until completely dissolved to obtain PA-PEI solution; dissolve 108.155g of proton exchange resin (Nafion in this example) in DMF to obtain Nafion solution; then add PA-PEI solution to Nafion solution and continue to use ultrasonic treatment and high shear mixing for 12h to form a uniform casting solution; S3. The casting solution is ultrasonically treated for 20 minutes to eliminate any air bubbles. Then, the evenly dispersed casting solution is poured onto a clean glass plate. The desired film thickness is controlled by an adjustable doctor blade. After the coating is completed, the film is kept at 50℃ for 24 hours to allow it to pre-shape. Then, it is annealed in a 170℃ forced-air drying oven for 4 hours. After annealing, the film is peeled off from the glass plate for post-treatment. The post-treatment process is as follows: At 80℃, the film is first immersed in a 0.5mol / L H2SO4 solution for 1 hour, and then immersed in deionized water for 1 hour. The above post-treatment steps are repeated three times. The film is then dried in a 70℃ vacuum drying oven for 24 hours to obtain a composite proton exchange membrane with a thickness of 25±1μm (named Nafion / PA-PEI-3, where 3 represents the mass fraction of PA-PEI in the proton exchange membrane as 3%).

[0042] Figure 1(a) illustrates the PEI and PA-PEI in this embodiment. 1 H NMR spectrum Figure 1 (b) Demonstrates the PEI and PA-PEI in this embodiment. 13 C10 NMR spectrum.

[0043] from Figure 1 (a) It can be seen that, compared with PEI 1 Compared to the 1H NMR spectrum, the new peaks at 3.21, 3.43, and 3.59 ppm of PA-PEI are attributed to the NCH2-CH2-PO3H2 segment. Furthermore, the absorption peak attributed to the -CH2-CH2-NH- segment shifted from 1.79 ppm to around 2.18 ppm, indicating that the NH group in PEI reacted with diethyl 2-bromoethylphosphonate to form a new NC bond.

[0044] from Figure 1 (b) It can be seen that in PA-PEI 13 The newly appearing peaks at 35.3, 37.2, 46.9 and 51.9 ppm in the C NMR spectrum correspond to the -CH2-CH2-PO3H2 segment, which also indicates that the -PO3H2 group was successfully introduced into the PEI.

[0045] Figure 2 The image shows the FTIR spectrum of PA-PEI in this embodiment, where 3100-3500 cm⁻¹ -1 The vibrational peaks at 1625 and 785 cm⁻¹ represent the stretching vibrations of the NH and OH groups. -1 The bending vibration of NH, 1200-1250cm -1 For stretching vibrations of P=O, 1035 and 958 cm -1 This refers to the stretching vibration of PO.

[0046] Example 2 A method for preparing a composite proton exchange membrane includes the following steps: S1. Dissolve 2 g (1.110 mmol) of polyethyleneimine (Mw = 1800) in 100 mL of deionized water, then add 15.140 g (46.50 mmol) of Cs₂CO₃ and stir magnetically until completely dissolved to obtain a mixture. Transfer the mixture to an 80°C water bath. Then, slowly add 8.548 g (34.88 mmol) of diethyl 2-bromoethylphosphonate to the mixture using a dropping funnel. React under a N₂ atmosphere for 72 h. After the reaction is complete, remove the liquid and... The crude product was obtained by stirring in 160 mL of 3 mol / L dilute hydrochloric acid solution for 72 h. To remove excess monomer and small molecule impurities, the crude product was poured into a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 96 h. The dialysis process was repeated three times. Finally, the liquid in the dialysis bag was collected and freeze-dried to obtain partially phosphorylated polyethyleneimine oligomer (solid PA-PEI product). The molar ratio of phosphate groups to active site NH in the solid PA-PEI product was 1:1.5. The specific structural formula of PA-PEI is as follows:

[0047] Where n=47.

[0048] S2. Dissolve 6.690g of solid PA-PEI product in 40mL of deionized water and stir until completely dissolved to obtain PA-PEI solution; dissolve 127.110g of proton exchange resin (Nafion in this example) in DMF to obtain Nafion solution; then add PA-PEI solution to Nafion solution and continue ultrasonic treatment and high shear mixing for 24h to form a uniform casting solution; S3. The casting solution is ultrasonically treated for 30 minutes to eliminate any air bubbles. Then, the evenly dispersed casting solution is poured onto a clean glass plate. The desired film thickness is controlled by an adjustable doctor blade. After the coating is completed, the film is pre-formed at 50°C for 36 hours. Then, it is annealed in a 190°C forced-air drying oven for 6 hours. After annealing, the film is peeled off from the glass plate for post-treatment. The post-treatment process is as follows: At 80°C, the film is first immersed in a 0.5 mol / L H2SO4 solution for 2 hours, and then immersed in deionized water for 2 hours. The above post-treatment steps are repeated three times. The film is then dried in a vacuum drying oven at 80°C for 36 hours to obtain a composite proton exchange membrane with a thickness of 25±1 μm (named Nafion / PA-PEI-5, where 5 represents the mass fraction of PA-PEI in the proton exchange membrane as 5%).

[0049] Example 3 A method for preparing a composite proton exchange membrane includes the following steps: S1. Dissolve 0.2 g (0.110 mmol) of polyethyleneimine (Mw = 1800) in 10 mL of deionized water, then add 1.514 g (4.650 mmol) of Cs₂CO₃ and stir magnetically until completely dissolved to obtain a mixture. Transfer the mixture to an 80°C water bath, and then slowly add 0.855 g (3.488 mmol) of diethyl 2-bromoethylphosphonate dropwise to the mixture using a dropping funnel. React under a N₂ atmosphere for 24 h. After the reaction is complete, remove the liquid. The crude product was poured into 16 mL of a 3 mol / L dilute hydrochloric acid solution and stirred for 24 h to obtain a crude product. To remove excess monomer and small molecule impurities, the crude product was poured into a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 48 h. The dialysis process was repeated three times. Finally, the liquid in the dialysis bag was collected and freeze-dried to obtain a partially phosphorylated polyethyleneimine oligomer (solid PA-PEI product). The molar ratio of phosphate groups to active site NH in the solid PA-PEI product was 1:4. The specific structural formula of PA-PEI is as follows:

[0050] Where n=54.

[0051] S2. Dissolve 0.669g of solid PA-PEI product in 10mL of deionized water and stir until completely dissolved to obtain PA-PEI solution; dissolve 66.231g of proton exchange resin (Nafion in this example) in DMF to obtain Nafion solution; then add PA-PEI solution to Nafion solution and continue ultrasonic treatment and high shear mixing for 6h to form a uniform casting solution; S3. The casting solution is ultrasonically treated for 10 minutes to eliminate any air bubbles. Then, the evenly dispersed casting solution is poured onto a clean glass plate. The desired film thickness is controlled by an adjustable doctor blade. After the coating is completed, the film is kept at 50℃ for 12 hours to allow it to pre-shape. Then, it is annealed in a 150℃ forced-air drying oven for 2 hours. After annealing, the film is peeled off from the glass plate for post-treatment. The post-treatment process is as follows: At 80℃, the film is first immersed in a 0.5mol / L H2SO4 solution for 0.5 hours, and then immersed in deionized water for 0.5 hours. The above post-treatment steps are repeated three times. The film is then dried in a 60℃ vacuum drying oven for 12 hours to obtain a composite proton exchange membrane with a thickness of 25±1μm (named Nafion / PA-PEI-1, where 1 represents the mass fraction of PA-PEI in the proton exchange membrane as 1%).

[0052] Comparative Example 1 (Traditional Nafion Membrane) A method for preparing a proton exchange membrane includes the following steps: S1. Dissolve proton exchange resin Nafion in DMF to obtain Nafion solution, and then use ultrasonic treatment and high shear mixing for 6 hours to form a uniform casting solution. S2. The casting solution is ultrasonically treated for 10 minutes to eliminate any air bubbles. Then, the evenly dispersed casting solution is poured onto a clean glass plate. The desired film thickness is controlled by an adjustable doctor blade. After the coating is completed, the film is kept at 50℃ for 12 hours to allow it to pre-shape. Then, it is annealed in a 150℃ forced-air drying oven for 2 hours. After annealing, the film is peeled off from the glass plate for post-treatment. The post-treatment process is as follows: At 80℃, the film is first immersed in a 0.5mol / L H2SO4 solution for 0.5 hours, and then immersed in deionized water for 0.5 hours. The above post-treatment steps are repeated three times. Finally, the film is dried in a 60℃ vacuum drying oven for 12 hours to obtain a proton exchange membrane with a thickness of 25±1μm (named Recast Nafion membrane).

[0053] Comparative Example 2 (The difference from Example 1 is that the PEI was not modified by phosphorylation) A method for preparing a composite proton exchange membrane includes the following steps: S1. Dissolve 3.345g of PEI (Mw = 1800) in 20mL of deionized water and stir until completely dissolved to obtain a PEI solution; dissolve proton exchange resin (Nafion) in DMF to obtain a Nafion solution; then add the PEI solution to the Nafion solution and continue to use ultrasonic treatment and high shear mixing for 12h to form a uniform casting solution. S2. The casting solution is ultrasonically treated for 20 minutes to eliminate any air bubbles. Then, the evenly dispersed casting solution is poured onto a clean glass plate. The desired film thickness is controlled by an adjustable doctor blade. After the coating is completed, the film is kept at 50°C for 24 hours to allow it to pre-shape. Then, it is annealed in a 170°C forced-air drying oven for 4 hours. After annealing, the film is peeled off from the glass plate for post-treatment. The post-treatment process is as follows: At 80°C, the film is first immersed in a 0.5 mol / L H2SO4 solution for 1 hour, and then immersed in deionized water for 1 hour. The above post-treatment steps are repeated three times. Finally, the film is dried in a 70°C vacuum drying oven for 24 hours to obtain a composite proton exchange membrane with a thickness of 25±1 μm (named Nafion / PEI).

[0054] Performance testing 1. In order to evaluate the actual effect of PA-PEI on the conductivity of proton exchange membranes, the proton conductivity of proton exchange membranes prepared in Examples 1-3 and Comparative Examples 1-2 was tested under different temperatures and 100% humidity conditions.

[0055] Proton conductivity testing procedure: A conductivity measurement system consisting of an electrochemical workstation (Autolab, PGSTA302N) and a constant temperature and humidity environmental test chamber (Taiwan Jufu, ETH-080ST-SSP) was used to study the conductivity under different temperature and relative humidity conditions. The proton conductivity of the proton exchange membrane was measured under specific temperature and humidity conditions. Before impedance testing, the proton exchange membrane samples were stabilized in an environmental chamber for one hour. During the test, the electrochemical workstation was set to a scanning frequency range of 1 Hz to 1 MHz, with a perturbation voltage of 10 mV. High-frequency impedance values ​​were read from EIS impedance spectra. Finally, the conductivity of the proton exchange membrane was calculated using the following formula:

[0056] Wherein, σ (S·cm) -1 L (cm), R (Ω), b (cm) and d (cm) represent the proton conductivity of the membrane, the distance between the two electrodes, the high-frequency impedance of the membrane, the effective length of the membrane in the direction perpendicular to the electrodes, and the thickness of the membrane, respectively. The test results of proton conductivity are as follows: Figure 3 As shown, the proton conductivity of all proton exchange membranes increases with increasing temperature. This is because higher temperatures help reduce the energy barrier during proton transport. Furthermore, at all temperatures, the composite proton exchange membranes prepared with PA-PEI (Examples 1-3) exhibit higher proton conductivity than Comparative Example 1. For example, at 30°C and 80°C, the proton conductivity of Nafion / PA-PEI-3 prepared in Example 1 is 0.136 S·cm. -1 and 0.243 S·cm -1 The values ​​were 1.58 and 1.24 times that of Comparative Example 1, respectively. In contrast, at all temperatures, the composite proton exchange membrane prepared with unphosphorylated PEI (Comparative Example 2) exhibited lower proton conductivity than Comparative Example 1.

[0057] 2. Ion permeability was tested in an H-type counter-diffusion cell. The membrane to be tested was sandwiched in the middle of the counter-diffusion cell. One side of the diffusion cell contained 50 mL of a 1.5 mol / L VOSO4 + 3.0 mol / L H2SO4 solution, while the other side contained the same volume of a 1.5 mol / L MgSO4 / 3.0 mol / L H2SO4 solution. Magnetic stirring was used to reduce concentration polarization within the diffusion cells. Every 24 hours, 4 mL of solution was taken from the MgSO4 / H2SO4 solution side, and the absorbance was measured using a UV-Vis spectrophotometer. The ion permeability was determined using an absorbance / concentration standard curve. 2+ The concentration of vanadium ions. The vanadium ion permeability is calculated using the following formula:

[0058] Among them, V B The volume of the MgSO4 / H2SO4 solution is 50 mL; C B (t) represents the VO in the MgSO4 / H2SO4 solution at time t. 2+ Ion concentration; C A VO in VOSO4 / H2SO4 solution 2+ Concentration is considered constant over a short experimental period to simplify calculations; A and L represent the effective membrane area (1.77 cm²). 2 ) and membrane thickness; P is vanadium ion permeability.

[0059] The performance test results of the proton exchange membranes prepared in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1.

[0060] In Table 1, ion selectivity is defined as the relationship between proton conductivity and VO2. 2+ The ratio of permeability, and the ion selectivity in Table 1, were calculated at proton conductivity at 80℃, using the following formula:

[0061] Table 1

[0062] As shown in Table 1, compared with the traditional Nafion membrane (Comparative Example 1), the composite proton exchange membranes prepared by adding PA-PEI (Examples 1-3) showed improved selectivity, decreased swelling degree, and decreased vanadium ion permeability; while the composite proton exchange membranes prepared by adding PEI (Comparative Example 2) also showed some improvement in selectivity, decreased swelling degree, and decreased vanadium ion permeability, but the changes were smaller than those shown in the examples.

[0063] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for preparing a composite proton exchange membrane, characterized by, The method comprises the following steps: S1, subjecting polyethyleneimine to a Michael addition reaction with diethyl 2-bromoethyl phosphonate, subjecting the product after the reaction to hydrolysis, dialysis and lyophilization to obtain a partially phosphonated polyethyleneimine oligomer; S2, mixing the partially phosphonated polyethyleneimine oligomer, a proton exchange resin containing a sulfonic acid group and a solvent to obtain a casting solution; S3, subjecting the casting solution to film formation to obtain the composite proton exchange membrane.

2. The production method according to claim 1, characterized by, The partially phosphonated polyethyleneimine oligomer has any one of the following structural formulae: 、 、 ； wherein n is 23-1628.

3. The preparation method according to claim 1, characterized in that, The partially phosphonated polyethyleneimine oligomer contains phosphonic acid groups and active sites N-H, and the molar ratio of the phosphonic acid groups to the active sites N-H is 1:(0.5-5).

4. The production method according to claim 1, characterized by, The proton exchange resin containing a sulfonic acid group comprises at least one of perfluorosulfonic acid resin, sulfonated polyether ether ketone and sulfonated polyether sulfone.

5. The preparation method according to claim 1, characterized in that, The mass fraction of the partially phosphonated polyethyleneimine oligomer in the composite proton exchange membrane is 0.5%-5%.

6. The method of claim 1, wherein, The Michael addition reaction in the step S1 is carried out at a temperature of 60-100℃; and / or, the Michael addition reaction is carried out under inert gas protection; and / or, the Michael addition reaction is carried out for 24-72h; and / or, the Michael addition reaction is carried out under alkaline conditions.

7. The preparation method according to claim 1, characterized in that, The molar ratio of the polyethyleneimine to diethyl 2-bromoethyl phosphonate is 1:(30-33).

8. The method of claim 1, wherein, The hydrolysis is carried out under acidic conditions; and / or, the hydrolysis is carried out for 24-72h.

9. A composite proton exchange membrane, characterized by, The method is prepared by any one of claims 1-8.

10. A flow battery, characterized in that, The flow battery comprises the composite proton exchange membrane of claim 9. The flow battery comprises the composite proton exchange membrane of claim 9.

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