Perfluorosulfonic acid body hybrid membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of proton exchange membranes, and provides a perfluorosulfonic acid body hybrid membrane as well as a preparation method and application thereof. The perfluorosulfonic acid body hybrid membrane provided by the invention comprises a perfluorosulfonic acid membrane and a hybridization agent selectively distributed in an ion phase region of the perfluorosulfonic acid membrane, the hybridization agent is a poly (vinyl pyrrolidone-vinyl alcohol) random copolymer (PVP-PVA). PVP-PVA is adopted to hybridize the perfluorosulfonic acid membrane, PVP-PVA has supramolecular action sites, pyrrolidone groups and hydroxyl groups in PVP-PVA can form dense hydrogen bonds with sulfonic acid groups in the perfluorosulfonic acid membrane, so that a polymer is selectively assembled in an ion phase region of the perfluorosulfonic acid membrane; through the Tangnan effect of N + in the polymer and the steric hindrance effect of a pyrrolidone group, the vanadium ion transmittance of the membrane can be reduced, and meanwhile, relatively high proton conduction capability can be maintained, so that the long-term stability, coulombic efficiency and energy efficiency of the all-vanadium redox flow battery are improved.

Description

Technical Field

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

[0002] All-vanadium redox flow batteries (AVFBs) are energy storage batteries based on the principle of redox reactions. Their unique operating mechanism and significant advantages have made them a key player in the field of large-scale energy storage. Using vanadium ions of varying valence as the active material, AVFBs convert electrical energy into chemical energy, which is stored in a sulfuric acid electrolyte. The battery primarily consists of positive and negative electrode reservoirs, a stack, an external pump, and piping. During operation, the external pump circulates the sulfuric acid electrolyte between the positive and negative electrode reservoirs and the stack. A proton exchange membrane separates the positive and negative electrolytes within the battery. The membrane allows protons to pass while preventing vanadium ions of varying valences from mixing. During discharge, the low-valence vanadium ions at the negative electrode lose electrons in an oxidation reaction, which then flows to the positive electrode via an external circuit. The high-valence vanadium ions at the positive electrode gain electrons in a reduction reaction, and protons in the electrolyte migrate from the negative electrode to the positive electrode through the membrane, thus converting chemical energy into electrical energy.

[0003] A key component of all-vanadium redox flow batteries is the proton exchange membrane, which acts as a barrier to electrolytes and conducts protons. Currently, the most widely used proton exchange membrane is a perfluorosulfonic acid membrane, which forms interconnected ionic phases when hydrated, endowing the membrane with excellent proton conductivity and good chemical and physical stability. However, the larger ionic phases of the perfluorosulfonic acid membrane also present drawbacks, leading to significant crossover of vanadium ions, causing self-discharge in the all-vanadium redox flow battery and significantly negatively impacting the coulombic efficiency and energy efficiency of the battery. Summary of the Invention

[0004] In light of this, the present invention provides a perfluorosulfonic acid bulk hybrid membrane, its preparation method, and its application. The present invention utilizes a poly(vinyl pyrrolidone-vinyl alcohol) random copolymer hybrid perfluorosulfonic acid membrane to significantly improve the membrane's vanadium barrier properties while maintaining high proton conductivity.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A perfluorosulfonic acid bulk hybrid membrane comprises a perfluorosulfonic acid membrane and a hybridizing agent selectively distributed in the ionic phase region of the perfluorosulfonic acid membrane; the hybridizing agent is a poly(vinyl pyrrolidone-vinyl alcohol) random copolymer; and the mass of the hybridizing agent is 0.1-50% of the mass of the perfluorosulfonic acid membrane.

[0006] Preferably, the weight average molecular weight of the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer is 3500-13000000 Da.

[0007] Preferably, the perfluorosulfonic acid membrane includes one or more of Nafion proton exchange membrane, Xion-PEM-Dyeon proton exchange membrane and Gore proton exchange membrane.

[0008] The present invention also provides a method for preparing the perfluorosulfonic acid bulk hybrid membrane described in the above scheme, comprising the following steps: Dissolving poly(vinyl pyrrolidone-vinyl alcohol) random copolymer and perfluorosulfonic acid resin in an organic solvent to obtain a casting solution; The casting solution is cast into a membrane to obtain the perfluorosulfonic acid bulk hybrid membrane.

[0009] Preferably, the organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and alcohol solvents.

[0010] Preferably, the dissolution temperature is 40-200° C. and the dissolution time is 12-48 hours.

[0011] Preferably, the method further comprises drying the wet film after the film casting, wherein the drying temperature is 40-200°C.

[0012] Preferably, the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer is obtained by hydrolyzing a poly(vinyl pyrrolidone-vinyl acetate) random copolymer.

[0013] Preferably, the preparation method of the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer comprises: mixing the poly(vinyl pyrrolidone-vinyl acetate) random copolymer, an alkaline agent and a solvent for hydrolysis reaction to obtain the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer; the alkaline agent comprises one or more of alkali metal hydroxide, alkali metal carbonate, alkali metal bicarbonate, hydrazine, ammonia and sodium thiosulfate.

[0014] The present invention also provides the use of the perfluorosulfonic acid bulk hybrid membrane described in the above scheme or the perfluorosulfonic acid bulk hybrid membrane prepared by the preparation method described in the above scheme in an all-vanadium redox flow battery.

[0015] The present invention provides a perfluorosulfonic acid bulk hybrid membrane, comprising a perfluorosulfonic acid membrane and a hybridizing agent selectively distributed in the ionic phase region of the perfluorosulfonic acid membrane; the hybridizing agent is a poly(vinyl pyrrolidone-vinyl alcohol) random copolymer (PVP-PVA); the mass of the hybridizing agent is 0.1-50% of the mass of the perfluorosulfonic acid membrane. The present invention uses a PVP-PVA hybrid perfluorosulfonic acid membrane. The PVP-PVA has supramolecular interaction sites. The pyrrolidone groups and hydroxyl groups therein can form dense hydrogen bonds with the sulfonic acid groups in the perfluorosulfonic acid membrane, thereby enabling the polymer to selectively assemble in the ionic phase region of the perfluorosulfonic acid membrane. Through the N+ The Donnan effect and the steric hindrance effect of the pyrrolidone group can reduce the vanadium ion permeability of the membrane and improve the selectivity, while maintaining a high proton conductivity, thereby improving the long-term stability, coulombic efficiency and energy efficiency of the all-vanadium liquid flow battery. DETAILED DESCRIPTION

[0016] The present invention provides a perfluorosulfonic acid bulk hybrid membrane, comprising a perfluorosulfonic acid membrane and a hybridizing agent selectively distributed in the ionic phase region of the perfluorosulfonic acid membrane; the hybridizing agent is a poly(vinyl pyrrolidone-vinyl alcohol) random copolymer; and the mass of the hybridizing agent is 0.1-50% of the mass of the perfluorosulfonic acid membrane.

[0017] In the present invention, the weight-average molecular weight of the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer is preferably 3500-13000000Da, specifically 5000Da, 10000Da, 40000Da, 50000Da, 100000Da, 500000Da, 1000000Da, 1200000Da, 2000000Da, 5000000Da, 8000000Da, 10000000Da or 12000000Da. In the present invention, the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer has the advantages of low cost and ease of preparation. The present invention uses the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer hybridized perfluorosulfonic acid membrane to obtain a novel proton exchange membrane with high vanadium resistance, good selectivity and low cost, which has broad application prospects in the fields of all-vanadium redox flow batteries.

[0018] In the present invention, the perfluorosulfonic acid membrane preferably includes one or more of Nafion proton exchange membrane, Xion-PEM-Dyeon proton exchange membrane and Gore proton exchange membrane; the Xion-PEM-Dyeon proton exchange membrane preferably includes Xion-PEM-Dyeon-725 proton exchange membrane, Xion-PEM-Dyeon-800 proton exchange membrane, Xion-PEM-Dyeon-1000 proton exchange membrane, Xion-PEM-D Yeon-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 5~50μm, specifically 5μm, 10μm, 25μm, 35μm or 50μm; the pore size of the Gore proton exchange membrane is preferably 8~18μm, specifically 9μm, 10μm, 16μm or 18μm.

[0019] In the present invention, the mass of the hybridizing agent is 0.1-50% of the mass of the perfluorosulfonic acid membrane, preferably 1-20%, specifically 1%, 2%, 3%, 4%, 5%, 10%, 15% or 20%.

[0020] The present invention also provides a method for preparing the perfluorosulfonic acid bulk hybrid membrane described in the above scheme, comprising the following steps: Dissolving poly(vinyl pyrrolidone-vinyl alcohol) random copolymer and perfluorosulfonic acid resin in an organic solvent to obtain a casting solution; The casting solution is cast into a membrane to obtain the perfluorosulfonic acid bulk hybrid membrane.

[0021] The present invention dissolves a poly(vinyl pyrrolidone-vinyl alcohol) random copolymer and a perfluorosulfonic acid resin in a solvent to obtain a casting solution. In the present invention, the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer is preferably obtained by hydrolyzing a poly(vinyl pyrrolidone-vinyl acetate) random copolymer (PVP-PVAc); specifically, the preparation method of the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer preferably includes: mixing a poly(vinyl pyrrolidone-vinyl acetate) random copolymer, an alkaline agent and a solvent for hydrolysis reaction to obtain a poly(vinyl pyrrolidone-vinyl alcohol) random copolymer; the alkaline agent preferably includes one or more of alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, hydrazine (N2H4), ammonia and sodium thiosulfate; the alkali metal hydroxide preferably includes one or both of sodium hydroxide and lithium hydroxide; the alkali metal The carbonate preferably includes one or both of sodium carbonate and potassium carbonate; the alkali metal bicarbonate preferably includes one or both of sodium bicarbonate and potassium bicarbonate; the molar amount of the alkaline agent is preferably more than 1 times the molar amount of the PVAc part in PVP-PVAc, more preferably 1 to 2 times; the solvent preferably includes one or more of water and alcohol; the alcohol preferably includes one or more of methanol, ethanol and isopropanol; specifically, the amount ratio of the PVP-PVAc, alkaline agent and alcohol is preferably 0.1~100g:0.125~300g:1~100mL; the temperature of the hydrolysis reaction is preferably room temperature, and the reaction time is preferably 24~72h, specifically 24h, 36h, 48h or 72h.

[0022] After the hydrolysis reaction is completed, the present invention preferably spin-dries the solvent in the obtained reaction solution to obtain a crude product; the crude product is dissolved in water to obtain a crude product solution; the crude product solution is dialyzed and then freeze-dried to obtain a poly(vinyl pyrrolidone-vinyl alcohol) random copolymer; the molecular weight cut-off of the dialysis bag for dialysis is preferably 5000, and the dialysis time is preferably 2 to 3 days; the freeze-drying temperature is preferably -70 to -80°C, more preferably -80°C, and the time is preferably 48 to 72 hours.

[0023] In the present invention, the preparation method of the perfluorosulfonic acid resin preferably includes: drying the perfluorosulfonic acid resin casting solution to remove the solvent to obtain the perfluorosulfonic acid resin; the drying temperature is preferably 60°C and the drying time is preferably 24 hours; the perfluorosulfonic acid resin casting solution can be a commercially available product, such as Nafion casting solution.

[0024] In the present invention, the organic solvent preferably includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and alcohol solvents; the amount ratio of the perfluorosulfonic acid resin to the organic solvent is preferably 100 mg:1~3 mL, more preferably 100 mg:1 mL; the dissolution temperature is preferably 40~200°C, specifically 60°C, 100°C or 150°C, and the dissolution time is preferably 12~48h, more preferably 24h; and the dissolution is preferably carried out under stirring conditions.

[0025] After obtaining the casting solution, the present invention casts the casting solution into a membrane to obtain the perfluorosulfonic acid bulk hybrid membrane. The present invention has no special requirements for the specific operation method of the casting membrane, and can adopt methods familiar to those skilled in the art; after the casting membrane, a wet film is obtained, and preferably the wet film is dried; the drying temperature is preferably 40 to 200°C, specifically 60°C, 80°C, 120°C, 160°C, or 200°C; the drying time is preferably 48 to 72 hours; the drying is preferably carried out in an oven, specifically by placing the wet film on a glass plate in the oven for drying; after drying, the film is preferably cooled to room temperature, and then peeled off the glass plate.

[0026] The present invention also provides the use of the perfluorosulfonic acid bulk hybrid membrane described in the above scheme, or the perfluorosulfonic acid bulk hybrid membrane prepared by the preparation method described in the above scheme, in an all-vanadium redox flow battery. The perfluorosulfonic acid bulk hybrid membrane provided by the present invention has excellent vanadium resistance and high proton conductivity. Its application in an all-vanadium redox flow battery can prevent self-discharge and improve the coulombic efficiency and energy efficiency of the all-vanadium redox flow battery.

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions 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 creative efforts are within the scope of protection of the present invention.

[0028] The preparation method of Nafion resin used in the following examples is as follows: pour the Nafion casting solution into a clean watch glass, place it in a 60° C. forced air oven for 24 hours to remove the solvent, and obtain dry Nafion resin.

[0029] The preparation method of PVP-PVA used in the following examples is as follows: 10 g of PVP-PVAc (molecular weight of approximately 5w), 10 g of potassium hydroxide and 20 mL of methanol are mixed, and the mixture is reacted at room temperature for 36 hours. After the reaction is completed, the methanol in the reaction solution is dried to obtain a crude product; the crude product is dissolved in water and dialyzed in a dialysis bag (molecular weight cut-off of approximately 5000) for 2 days, and then freeze-dried at -80°C for 48 hours to obtain PVP-PVA with a molecular weight of approximately 4w.

[0030] Example 1 3 mg of PVP-PVA and 100 mg of Nafion resin were added to 1 mL of DMF, heated and stirred at 60°C for 24 hours to obtain a casting solution; the casting solution was cast to obtain a wet film, which was placed on a glass plate in a drying oven, and the solvent was evaporated at 80°C for 72 hours. After cooling to room temperature, the film was peeled off from the glass plate to obtain a perfluorosulfonic acid bulk hybrid membrane.

[0031] Example 2 2 mg of PVP-PVA and 100 mg of Nafion resin were added to 1 mL of DMF, heated and stirred at 60°C for 24 hours to obtain a casting solution; the casting solution was cast to obtain a wet film, which was placed on a glass plate in a drying oven, and the solvent was evaporated at 80°C for 72 hours. After cooling to room temperature, the film was peeled off from the glass plate to obtain a perfluorosulfonic acid bulk hybrid membrane.

[0032] Example 3 4 mg of PVP-PVA and 100 mg of Nafion resin were added to 1 mL of DMF, heated and stirred at 60°C for 24 hours to obtain a casting solution; the casting solution was cast to obtain a wet film, which was placed on a glass plate in a drying oven, and the solvent was evaporated at 80°C for 72 hours. After cooling to room temperature, the film was peeled off from the glass plate to obtain a perfluorosulfonic acid bulk hybrid membrane.

[0033] Example 4 3 mg of PVP-PVA and 100 mg of Nafion resin were added to 1 mL of DMAc, heated and stirred at 60°C for 24 hours to obtain a casting solution; the casting solution was cast to obtain a wet film, which was placed on a glass plate in a drying oven, and the solvent was evaporated at 80°C for 72 hours. After cooling to room temperature, the film was peeled off from the glass plate to obtain a perfluorosulfonic acid bulk hybrid membrane.

[0034] Comparative Example 1 A membrane was prepared directly by casting using Nafion casting solution, and the obtained Nafion membrane was used as comparative example 1.

[0035] Test Case The proton conductivity, vanadium ion leakage rate and ion selectivity of the perfluorosulfonic acid bulk hybrid membranes prepared in Examples 1 to 4 and the Nafion membrane prepared in Comparative Example 1 were tested. The test method is as follows: Proton conductivity test: surface resistance of membrane samples AR (Ω cm 2 ) were measured using a two-probe method on an AMETEK VersaSTAT3 impedance analyzer in the frequency range of 0.1 Hz to 10 MHz, with a perturbation voltage set to 10 mV. The test apparatus consisted of a diffusion cell with graphite rod electrodes inserted on both sides, each containing 35 mL of 3 M H2SO4 solution. A membrane sample (3 × 3 cm) was placed 2 ) was soaked in 3 M H2SO4 solution for 12 hours in advance and then clamped in the middle of the diffusion cell. The resistance of the test device with and without membrane was recorded as r 1 and r 2. AR and the proton conductivity in the membrane permeation direction σ (S cm -1 ) is calculated by the following formula: ; ; in L (cm) is the thickness of the film sample, S (cm 2 ) is the effective area of ​​the membrane sample sandwiched in the middle of the diffusion cell that contacts the solution, which is 2.0 cm 2 .

[0036] Vanadium ion leakage rate and proton selectivity test: The vanadium ion permeation experiment was carried out by using a diffusion cell. 2 ) was soaked in 3 M H2SO4 solution for 12 h in advance and then clamped in the middle of the diffusion cell. The left diffusion half cell was filled with 40 mL of 3 M H2SO4 solution containing 1.5 M VOSO4, and the right diffusion half cell was filled with 40 mL of 3 M H2SO4 solution containing 1.5 M MgSO4 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 out from the right diffusion cell for ultraviolet absorption spectroscopy (SHIMADZU UV-1900i UV-visible spectrophotometer) to determine the absorption peak intensity of the solution at 762 nm. After the test, the solution was recovered to the right diffusion cell. Vanadium ion leakage rate P (cm 2 min -1 ) and proton selectivity S (S min cm -3 ) is calculated by the following formula: ; ; in L (cm) is the thickness of the film sample, A (cm 2 ) is the effective area of ​​the membrane sample sandwiched in the middle of the diffusion cell that contacts the solution, 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 left half pool and time t The VO of the right half of the cistern is 2+ concentration.

[0037] The test results are shown in Table 1.

[0038] Table 1 Test results

[0039] According to the data in Table 1, it can be seen that the use of PVP-PVA for bulk hybridization of perfluorosulfonic acid membrane can significantly improve the vanadium resistance and ion selectivity of the membrane while maintaining good proton conductivity.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A perfluorosulfonic acid bulk hybrid membrane, characterized in that: The invention comprises a perfluorosulfonic acid membrane and a hybridizing agent selectively distributed in the ionic phase region of the perfluorosulfonic acid membrane; the hybridizing agent is a poly(vinyl pyrrolidone-vinyl alcohol) random copolymer; and the mass of the hybridizing agent is 0.1-50% of the mass of the perfluorosulfonic acid membrane.

2. The perfluorosulfonic acid bulk hybrid membrane according to claim 1, characterized in that: The weight average molecular weight of the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer is 3500-13000000 Da.

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

4. The method for preparing a perfluorosulfonic acid bulk hybrid membrane according to any one of claims 1 to 3, characterized in that: The following steps are involved: Dissolving poly(vinyl pyrrolidone-vinyl alcohol) random copolymer and perfluorosulfonic acid resin in an organic solvent to obtain a casting solution; The casting solution is cast into a membrane to obtain the perfluorosulfonic acid bulk hybrid membrane.

5. The preparation method according to claim 4, characterized in that The organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and alcohol solvents.

6. The preparation method according to claim 4, characterized in that The dissolution temperature is 40-200° C., and the dissolution time is 12-48 hours.

7. The preparation method according to claim 4, characterized in that The method further comprises drying the wet film after the film is cast; the drying temperature is 40-200°C.

8. The preparation method according to claim 4, characterized in that The poly(vinyl pyrrolidone-vinyl alcohol) random copolymer is obtained by hydrolyzing a poly(vinyl pyrrolidone-vinyl acetate) random copolymer.

9. The preparation method according to claim 8, characterized in that The preparation method of the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer comprises: mixing the poly(vinyl pyrrolidone-vinyl acetate) random copolymer, an alkaline agent and a solvent and performing a hydrolysis reaction to obtain the poly(vinyl pyrrolidone-vinyl alcohol) random copolymer; the alkaline agent comprises one or more of alkali metal hydroxide, alkali metal carbonate, alkali metal bicarbonate, hydrazine, ammonia and sodium thiosulfate.

10. Use of the perfluorosulfonic acid bulk hybrid membrane according to any one of claims 1 to 3 or the perfluorosulfonic acid bulk hybrid membrane prepared by the preparation method according to any one of claims 4 to 9 in an all-vanadium redox flow battery.

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