Perfluorosulfonic acid hybrid membrane, preparation method thereof and application of perfluorosulfonic acid hybrid membrane in all-vanadium redox flow battery

Abstract

The invention relates to the technical field of proton exchange membranes, and provides a perfluorosulfonic acid hybrid membrane, a preparation method thereof and application of the perfluorosulfonic acid hybrid membrane in an all-vanadium redox flow battery. The perfluorosulfonic acid hybrid membrane provided by the invention comprises a perfluorosulfonic acid membrane and a hybridization agent modified in a hydrophilic phase region of the perfluorosulfonic acid membrane, the hybridization agent is a polystyrene-poly (vinylpyridine) random copolymer; the mass of the hybridizing agent is 1%-20% of the mass of the perfluorosulfonic acid membrane. By adopting the polystyrene-poly (vinylpyridine) random copolymer hybrid perfluorosulfonic acid membrane, the vanadium resistance and ion selectivity of the membrane can be remarkably improved while the proton conductivity is maintained, so that the long-term stability, coulombic efficiency and energy efficiency of the all-vanadium redox flow battery are effectively improved, and the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of proton exchange membranes, and in particular to a perfluorosulfonic acid hybrid membrane, a preparation method thereof, and an application thereof in a vanadium redox flow battery. Background Art

[0002] A vanadium redox flow battery is a new type of electrochemical energy storage device, which mainly utilizes the reversible redox reaction of vanadium ions between different oxidation states to achieve the storage and release of electrical energy. The electrical energy of the vanadium redox flow battery is stored in the sulfuric acid electrolyte of vanadium ions in different valence states in the form of chemical energy. The electrolyte is pumped into the battery stack body by an external pump, and under the action of mechanical power, it circulates in a closed loop of different storage tanks and half-cells. A proton exchange membrane is used as the diaphragm of the battery pack, and the electrolyte solution flows parallel to the electrode surface and undergoes an electrochemical reaction. The current is collected and conducted through the bipolar plate, so that the chemical energy stored in the solution is converted into electrical energy.

[0003] The proton exchange membrane is a key component of the vanadium redox flow battery, which has the functions of separating the positive and negative electrolyte solutions and transferring protons. At present, the mainstream proton exchange membrane is the perfluorosulfonic acid membrane, which has high proton conductivity, good chemical and physical stability. The perfluorosulfonic acid membrane is mainly composed of a hydrophobic perfluorocarbon main chain and a hydrophilic sulfonic acid group. There are nanoionic phase regions in the internal structure of the membrane, and these nanoionic phase regions are formed due to the aggregation of sulfonic acid groups. However, at present, the nanoionic phase regions of the perfluorosulfonic acid membrane are relatively large, and the relatively large nanoionic phase regions make it easier for vanadium ions to pass through the membrane and migrate from one electrolyte solution to the other, resulting in serious vanadium crossover, which seriously affects the Coulomb efficiency and energy efficiency of the vanadium redox flow battery.

[0004] Adding SiO 2 nanoparticles, TiO 2 or ZrO 2 nanotubes, graphene oxide nanosheets, and MOF and other additives to the perfluorosulfonic acid membrane, or blending polymers such as poly(vinylidene fluoride) and polytetrafluoroethylene with the perfluorosulfonic acid membrane can improve the vanadium resistance performance of the perfluorosulfonic acid membrane to a certain extent, but usually the continuous proton transport channels are damaged due to incompatibility or aggregation of non-conductive components. Therefore, how to improve the vanadium resistance while maintaining the continuity of the proton transport channels of the perfluorosulfonic acid membrane is still a challenge. Summary of the Invention

[0005] In view of this, the present invention provides a perfluorosulfonic acid hybrid membrane, a preparation method thereof, and an application thereof in a vanadium redox flow battery. The perfluorosulfonic acid hybrid membrane provided by the present invention greatly improves the vanadium resistance and selectivity while maintaining proton conductivity.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions: A perfluorosulfonic acid hybrid membrane, comprising a perfluorosulfonic acid membrane and a hybridizing agent modified in the hydrophilic phase region of the perfluorosulfonic acid membrane; the hybridizing agent is a polystyrene-poly(vinylpyridine) random copolymer; the mass of the hybridizing agent is 1% to 20% of the mass of the perfluorosulfonic acid membrane.

[0007] Preferably, the polystyrene-poly(vinylpyridine) random copolymer comprises one or both of a polystyrene-poly(2-vinylpyridine) random copolymer and a polystyrene-poly(4-vinylpyridine) random copolymer.

[0008] Preferably, the polystyrene-poly(2-vinylpyridine) random copolymer has a weight-average molecular weight of 3500 to 13000000 Da.

[0009] Preferably, the polystyrene-poly(4-vinylpyridine) random copolymer has a weight-average molecular weight of 3500 to 13000000 Da.

[0010] Preferably, the perfluorosulfonic acid membrane comprises one or more of a Nafion proton exchange membrane, a Gore proton exchange membrane, and an Xion-PEM-Dyeon proton exchange membrane.

[0011] The present invention also provides a method for preparing the perfluorosulfonic acid hybrid membrane described in the above solution, comprising the following steps: Dissolve the polystyrene-poly(vinylpyridine) random copolymer and the perfluorosulfonic acid resin in a solvent to obtain a casting solution; Form the casting solution into a film to obtain the perfluorosulfonic acid hybrid membrane.

[0012] Preferably, the solvent comprises one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and an alcohol solvent.

[0013] Preferably, the dissolution temperature is 40 to 200 °C; after dissolution, the obtained solution is further stirred at room temperature.

[0014] Preferably, the film formation comprises: casting the casting solution to obtain a wet film, and drying the wet film; the drying temperature is 40 to 200 °C.

[0015] The present invention also provides the application of the perfluorosulfonic acid hybrid membrane described in the above solution or the perfluorosulfonic acid hybrid membrane prepared by the preparation method described in the above solution in a vanadium redox flow battery.

[0016] The present invention provides a perfluorosulfonic acid hybrid membrane, which comprises a perfluorosulfonic acid membrane and a hybrid agent modified in the hydrophilic phase region of the perfluorosulfonic acid membrane; the hybrid agent is a polystyrene-poly(vinylpyridine) random copolymer, and the mass of the hybrid agent is 1% - 20% of the mass of the perfluorosulfonic acid membrane. The present invention uses a polystyrene-poly(vinylpyridine) random copolymer to hybridize the perfluorosulfonic acid membrane. The polystyrene-poly(vinylpyridine) random copolymer has good compatibility with the perfluorosulfonic acid membrane. It is precisely modified in the hydrophilic phase region of the perfluorosulfonic acid membrane through hydrophilic assembly. Through the Donnan effect of its N + ions and the steric hindrance effect of the benzene ring, the vanadium resistance and selectivity of the perfluorosulfonic acid membrane can be significantly improved. Moreover, by regulating the density of polyvinylpyridine with styrene, good dispersion of pyridine groups can be achieved, and at the same time, the polystyrene-poly(vinylpyridine) has an appropriate crosslinking density and proton transport ability. Furthermore, while maintaining the proton conductivity, the hybrid membrane can obtain a synergistic enhancement of vanadium resistance performance and selectivity, thereby effectively improving the long-term stability, Coulomb efficiency and energy efficiency of the all-vanadium redox flow battery. Detailed implementation mode

[0017] The present invention provides a perfluorosulfonic acid hybrid membrane, which comprises a perfluorosulfonic acid membrane and a hybrid agent modified in the hydrophilic phase region of the perfluorosulfonic acid membrane; the hybrid agent is a polystyrene-poly(vinylpyridine) random copolymer; the mass of the hybrid agent is preferably 1% - 20% of the mass of the perfluorosulfonic acid membrane.

[0018] In the present invention, the polystyrene-poly(vinylpyridine) random copolymer preferably comprises one or both of a polystyrene-poly(2-vinylpyridine) (PS-P2VP) random copolymer and a polystyrene-poly(4-vinylpyridine) (PS-P4VP) random copolymer; the weight-average molecular weight of the polystyrene-poly(vinylpyridine) random copolymer is preferably 3500-13000000 Da; specifically, the weight-average molecular weight of the polystyrene-poly(2-vinylpyridine) random copolymer is preferably 3500-13000000 Da, and may specifically be 200000 Da, 220000 Da, 500000 Da, 800000 Da or 1000000 Da; the weight-average molecular weight of the polystyrene-poly(4-vinylpyridine) random copolymer is preferably 3500-13000000 Da, and may specifically be 200000 Da, 220000 Da, 500000 Da, 800000 Da or 1000000 Da. The polystyrene-poly(vinylpyridine) random copolymer adopted in the present invention has good hydrophilicity, good compatibility with the matrix membrane, can be uniformly dispersed in the matrix membrane, and is continuously positioned in the ion transport channels; moreover, the polystyrene-poly(vinylpyridine) random copolymer is not easily decomposed at high temperatures, has good thermal stability; can be dissolved in many solvents, has good compatibility in organisms, has good environmental friendliness, and also has good film-forming properties; in addition, the polystyrene-poly(vinylpyridine) random copolymer has the advantages of low cost and being simple and easy to prepare. By hybridizing the perfluorosulfonic acid membrane with the polystyrene-poly(vinylpyridine) random copolymer, the present invention can improve the vanadium resistance and selectivity of the membrane while maintaining its proton conductivity, and at the same time has a low cost, and has broad prospects in the field of all-vanadium redox flow batteries.

[0019] In the present invention, the mass of the hybridizing agent is 1%-20% of the mass of the perfluorosulfonic acid membrane, and may specifically be 1%, 2%, 3%, 5%, 10%, 12%, 15% or 18%.

[0020] In the present invention, the perfluorosulfonic acid membrane preferably comprises one or more of Nafion proton exchange membrane, Gore proton exchange membrane and Xion-PEM-Dyeon proton exchange membrane; the pore size of the Gore proton exchange membrane is preferably 8-18 μm, specifically it can be 8 μm, 12 μm, 15 μm or 18 μm; the Xion-PEM-Dyeon proton exchange membrane preferably comprises Xion-PEM-Dyeon-725 proton exchange membrane, Xion-PEM-Dyeon-800 proton exchange membrane, Xion-PEM-Dyeon-1000 proton exchange membrane, Xion-PEM-Dyeon-1100 proton exchange membrane, Xion-PEM-Dyeon-720 proton exchange membrane or Xion-PEM-Dyeon-830 proton exchange membrane; the pore size of the Xion-PEM-Dyeon proton exchange membrane is preferably 5-50 μm, specifically it can be 5 μm, 10 μm, 20 μm, 30 μm or 50 μm.

[0021] The present invention also provides a method for preparing the perfluorosulfonic acid hybrid membrane described in the above solution, comprising the following steps: Dissolve the polystyrene-poly(vinylpyridine) random copolymer and the perfluorosulfonic acid resin in a solvent to obtain a casting solution; Form the casting solution into a film to obtain the perfluorosulfonic acid hybrid membrane.

[0022] In the present invention, the polystyrene-poly(vinylpyridine) random copolymer and the perfluorosulfonic acid resin are dissolved in a solvent to obtain a casting solution. In the present invention, the preparation method of the perfluorosulfonic acid resin preferably comprises: pouring the perfluorosulfonic acid resin casting solution into a clean petri dish, drying to remove the solvent to obtain the perfluorosulfonic acid resin; the drying temperature is preferably 60 °C and the time is preferably 24 h; the perfluorosulfonic acid resin casting solution can use commercially available products, such as Nafion casting solution.

[0023] In the present invention, the solvent preferably includes one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and alcohol solvents; the alcohol solvents preferably include one or more of methanol, ethanol, and isopropanol; the present invention has no special requirements for the amount of the solvent, as long as it can dissolve the polystyrene-poly(vinylpyridine) random copolymer and the perfluorosulfonic acid resin. In a specific embodiment of the present invention, the dosage ratio of the perfluorosulfonic acid resin to the solvent can be 100 mg:1 mL; the dissolution temperature is preferably 40-200 °C, specifically 60 °C. The present invention has no special requirements for the dissolution time, and it is based on the complete dissolution of the polystyrene-poly(vinylpyridine) random copolymer and the perfluorosulfonic acid resin, specifically 12 h; after dissolution, it is preferably further included to stir the obtained dissolution solution at room temperature; the stirring time at room temperature is preferably 24 h.

[0024] After obtaining the casting solution, the present invention forms a film from the casting solution to obtain the perfluorosulfonic acid hybrid membrane. In the present invention, the film formation preferably includes: performing solution casting on the casting solution to obtain a wet film, and drying the wet film; the drying temperature is preferably 40-200 °C, specifically 80 °C. The drying is preferably carried out in an oven, specifically by placing the wet film on a glass plate in a drying oven for drying; the present invention removes the solvent in the wet film by drying; the present invention has no special requirements for the drying time, and it is based on the complete volatilization of the solvent in the wet film. In a specific embodiment of the present invention, the drying time is 12 h. After drying is completed, cooling is carried out, and then the film is peeled off from the glass plate.

[0025] The present invention also provides the application of the perfluorosulfonic acid hybrid membrane described in the above solution or the perfluorosulfonic acid hybrid membrane prepared by the preparation method described in the above solution in a vanadium redox flow battery.

[0026] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] The preparation method of the Nafion resin used in the following examples is: pouring the Nafion casting solution into a clean petri dish, and placing it in a 60 °C blast drying oven for 24 h to remove the solvent, obtaining a dry Nafion resin.

[0028] The specific test methods for testing the surface conductivity, vanadium ion leakage rate, and ion selectivity of the membrane in the following examples are as follows: The surface resistance of the membrane sampleAR (Ω cm 2 ) was measured on an impedance analyzer of model VersaSTAT3 from AMETEK Inc. in the United States by using the two-probe method in the frequency range of 0.1 Hz to 10 MHz, with the perturbation voltage set at 10 mV. The test device was a diffusion cell with graphite rod electrodes inserted on both sides and each containing 35 mL of 3 M H 2 SO 4 solution. The membrane sample (3×3 cm 2 ) was pre-soaked in 3 M H 2 SO 4 solution for 12 h and then clamped in the middle of the diffusion cell. The resistances with and without the membrane in the test device were denoted as r 1 and r 2 . AR And the proton conductivity σ (S cm -1 ) in the direction of membrane permeation was calculated by the following formula:

[0029]

[0030] where L (cm) is the thickness of the membrane sample, S (cm 2 ) is the effective area of the membrane sample in contact with the solution when clamped in the middle of the diffusion cell, which is 2.0 cm 2 .

[0031] The vanadium ion permeation experiment was carried out through the diffusion cell. The membrane sample (3×3 cm 2 ) was pre-soaked in 3 M H 2 SO 4 solution for 12 h and then clamped in the middle of the diffusion cell. The left diffusion half-cell was filled with 40 mL of 3 M H 4 SO 2 solution containing 1.5 M VOSO 4 , and the right diffusion half-cell was filled with 40 mL of 3 M H 4 SO 2 solution containing 1.5 M MgSO 4 to balance the osmotic pressure. Magnetic stirring was maintained throughout the test (120 h) to eliminate concentration polarization. Every 24 h, 3 mL of solution was taken from the right diffusion cell for ultraviolet absorption spectroscopy (SHIMADZU UV-1900i ultraviolet-visible spectrophotometer) detection to determine the absorption peak intensity of the solution at 762 nm. After the test, the solution was recovered to the right diffusion cell. The vanadium ion leakage rate P (cm 2min -1 ) and proton selectivity S (S mincm -3 ) is calculated by the following formula:

[0032]

[0033] where L (cm) is the thickness of the membrane sample, A (cm 2 ) is the effective area of the membrane sample in contact with the solution in the middle of the diffusion cell, which is 2.0 cm 2 ; V R is the volume of the solution in the right diffusion half-cell, which is 40 mL; C 0 and C t (mol L -1 ) are the concentrations of VO t in the left half-cell and at time 2+ in the right half-cell, respectively.

[0034] Example 1 2 mg of PS-P2VP (M w ≈22w) and 100 mg of Nafion resin were added to 1 mL of DMF. The mixture was fully dissolved in an oven at 60 °C for 12 h and then stirred at room temperature for 24 h. The resulting casting solution was prepared into a membrane by the solution casting method. The obtained wet membrane was placed on a glass plate in a drying oven for drying. The solvent was evaporated at 80 °C for 12 h. After cooling to room temperature, the membrane was peeled off from the glass plate. The obtained perfluorosulfonic acid hybrid membrane was denoted as PS-P2VP@Nafion. The surface conductivity, vanadium ion leakage rate, and ion selectivity of the obtained perfluorosulfonic acid hybrid membrane were tested, and the results are shown in Table 1.

[0035] Table 1 Test results of the perfluorosulfonic acid hybrid membrane in Example 1

[0036] Example 2 3 mg of PS-P2VP (M wApproximately 22 w) and 100 mg of Nafion resin were added to 1 mL of DMF. The mixture was fully dissolved in an oven at 60 °C for 12 h and then stirred at room temperature for 24 h. The resulting casting solution was prepared into a film by the solution casting method. The obtained wet film was placed on a glass plate in a drying oven for drying. The solvent was volatilized at 80 °C for 12 h. After cooling to room temperature, the film was peeled off from the glass plate. The obtained perfluorosulfonic acid hybrid film was denoted as PS-P2VP@Nafion. The surface conductivity, vanadium ion leakage rate, and ion selectivity of the obtained perfluorosulfonic acid hybrid film were tested, and the results are shown in Table 2.

[0037] Table 2 Test results of the perfluorosulfonic acid hybrid film in Example 2

[0038] Example 3 3 mg of PS-P4VP (M w Approximately 20 w) and 100 mg of Nafion resin were added to 1 mL of DMF. The mixture was fully dissolved in an oven at 60 °C for 12 h and then stirred at room temperature for 24 h. The resulting casting solution was prepared into a film by the solution casting method. The obtained wet film was placed on a glass plate in a drying oven for drying. The solvent was volatilized at 80 °C for 12 h. After cooling to room temperature, the film was peeled off from the glass plate. The obtained perfluorosulfonic acid hybrid film was denoted as PS-P4VP@Nafion. The surface conductivity, vanadium ion leakage rate, and ion selectivity of the obtained perfluorosulfonic acid hybrid film were tested, and the results are shown in Table 3.

[0039] Table 3 Test results of the perfluorosulfonic acid hybrid film in Example 3

[0040] Example 4 2 mg of PS-P4VP (M w Approximately 20 w) and 100 mg of Nafion resin were added to 1 mL of DMF. The mixture was fully dissolved in an oven at 60 °C for 12 h and then stirred at room temperature for 24 h. The resulting casting solution was prepared into a film by the solution casting method. The obtained wet film was placed on a glass plate in a drying oven for drying. The solvent was volatilized at 80 °C for 12 h. After cooling to room temperature, the film was peeled off from the glass plate. The obtained perfluorosulfonic acid hybrid film was denoted as PS-P4VP@Nafion. The surface conductivity, vanadium ion leakage rate, and ion selectivity of the obtained perfluorosulfonic acid hybrid film were tested, and the results are shown in Table 4.

[0041] Table 4 Test results of the perfluorosulfonic acid hybrid film in Example 4

[0042] Example 5 2 mg of PS-P2VP (Mw Approximately 22 w) and 100 mg of Nafion resin were added to 1 mL of DMAc. The mixture was fully dissolved in an oven at 60 °C for 12 h and then stirred at room temperature for 24 h. The resulting casting solution was formed into a film by the solution casting method. The obtained wet film was placed on a glass plate in a drying oven for drying. The solvent was volatilized at 80 °C for 12 h. After cooling to room temperature, the film was peeled off from the glass plate. The obtained perfluorosulfonic acid hybrid film was denoted as PS-P2VP@Nafion. The surface conductivity, vanadium ion leakage rate, and ion selectivity of the obtained perfluorosulfonic acid hybrid film were tested. The results are shown in Table 5.

[0043] Table 5 Test Results of the Perfluorosulfonic Acid Hybrid Film in Example 5

[0044] Example 6 2 mg of PS-P4VP (M w Approximately 20 w) and 100 mg of Nafion resin were added to 1 mL of DMAc. The mixture was fully dissolved in an oven at 60 °C for 12 h and then stirred at room temperature for 24 h. The resulting casting solution was formed into a film by the solution casting method. The obtained wet film was placed on a glass plate in a drying oven for drying. The solvent was volatilized at 80 °C for 12 h. After cooling to room temperature, the film was peeled off from the glass plate. The obtained perfluorosulfonic acid hybrid film was denoted as PS-P4VP@Nafion. The surface conductivity, vanadium ion leakage rate, and ion selectivity of the obtained perfluorosulfonic acid hybrid film were tested. The results are shown in Table 6.

[0045] Table 6 Test Results of the Perfluorosulfonic Acid Hybrid Film in Example 6

[0046] Comparative Example 1 A Nafion film was directly prepared into a film by the casting method using a Nafion casting solution. The obtained Nafion film was used as Comparative Example 1. The surface conductivity, vanadium ion leakage rate, and ion selectivity of the obtained Nafion film were tested. The results are shown in Table 7.

[0047] Table 7 Test Results of the Perfluorosulfonic Acid Proton Exchange Membrane in Comparative Example 1

[0048] It can be seen from the data in Tables 1 to 7 that compared with the Nafion film, the perfluorosulfonic acid hybrid film prepared by the present invention has significantly improved vanadium resistance and ion selectivity while maintaining good proton conductivity.

[0049] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A perfluorosulfonic acid hybrid membrane, characterized in that: The invention comprises a perfluorosulfonic acid membrane and a hybridizing agent modified in the hydrophilic phase region of the perfluorosulfonic acid membrane; the hybridizing agent is a polystyrene-poly (vinyl pyridine) random copolymer; and the mass of the hybridizing agent is 1% to 20% of the mass of the perfluorosulfonic acid membrane.

2. The perfluorosulfonic acid hybrid membrane according to claim 1, characterized in that: The polystyrene-poly(vinylpyridine) random copolymer includes one or both of a polystyrene-poly(2-vinylpyridine) random copolymer and a polystyrene-poly(4-vinylpyridine) random copolymer.

3. The perfluorosulfonic acid hybrid membrane according to claim 2, characterized in that: The weight average molecular weight of the polystyrene-poly (2-vinylpyridine) random copolymer is 3500-13000000 Da.

4. The perfluorosulfonic acid hybrid membrane according to claim 2, characterized in that: The weight average molecular weight of the polystyrene-poly (4-vinylpyridine) random copolymer is 3500-13000000 Da.

5. The perfluorosulfonic acid hybrid membrane according to claim 1, characterized in that: The perfluorosulfonic acid membrane includes one or more of a Nafion proton exchange membrane, a Gore proton exchange membrane and a Xion-PEM-Dyeon proton exchange membrane.

6. The method for preparing the perfluorosulfonic acid hybrid membrane according to any one of claims 1 to 5, characterized in that: The following steps are involved: Dissolving polystyrene-poly(vinylpyridine) random copolymer and perfluorosulfonic acid resin in a solvent to obtain a casting solution; The casting solution is formed into a membrane to obtain the perfluorosulfonic acid hybrid membrane.

7. The preparation method according to claim 6, characterized in that: The solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and alcohol solvents.

8. The preparation method according to claim 6 or 7, characterized in that: The dissolving temperature is 40-200° C. and after the dissolving, the obtained solution is stirred at room temperature.

9. The preparation method according to claim 6, characterized in that: The film forming comprises: solution casting the film casting liquid to obtain a wet film, and drying the wet film; the drying temperature is 40-200°C.

10. Use of the perfluorosulfonic acid hybrid membrane according to any one of claims 1 to 5 or the perfluorosulfonic acid hybrid membrane prepared by the preparation method according to any one of claims 6 to 9 in an all-vanadium redox flow battery.

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