A proton exchange membrane and its preparation method and application

Abstract

This invention belongs to the field of polymer materials technology, specifically relating to a proton exchange membrane, its preparation method, and application. The proton exchange membrane is prepared by blending a functional resin and an additive into a membrane; the functional resin comprises one or a combination of perfluorosulfonic acid resin, polybenzimidazole resin, polyetheretherketone resin, polyimide resin, polyethersulfone resin, and polysulfone resin; the additive is a sulfonated MXene; and the functional resin comprises 80-99.9% by mass, and the additive comprises 0.1-20% by mass. The proton exchange membrane prepared by this invention exhibits low ion permeability, high proton conductivity, excellent ion selectivity, and mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and in particular relates to a proton exchange membrane and a preparation method and application thereof. Background Art

[0002] To achieve safe, clean, and scalable renewable energy storage systems, liquid flow batteries (RFBs) have attracted significant attention in both the electrical and chemical energy fields due to their excellent battery efficiency, rapid response, long cycle life, and unique modular design, enabling the storage and release of electricity. As a key component of VRFB (vanadium liquid flow battery) systems, the proton exchange membrane (PEM) serves to isolate the positive and negative electrolytes and provides the necessary proton transport pathways. An excellent PEM should possess high proton conductivity, low metal ion permeability, excellent physical and chemical stability, and low cost. Therefore, research on PEMs with superior overall performance has become a hot topic in the liquid flow battery field.

[0003] Perfluorosulfonic acid resin is currently the most widely used proton exchange membrane material. Its special molecular structure gives it excellent mechanical and chemical stability. At the same time, the highly water-absorbing sulfonic acid group side chains on its surface also provide it with excellent proton conductivity. However, the high proton conductivity of perfluorosulfonic acid resin also increases its swelling properties, resulting in a decrease in its ability to block ion penetration and ion selectivity, which limits the effective use of perfluorosulfonic acid resin proton exchange membranes in liquid flow batteries.

[0004] By adding functional inorganic nanomaterials, the proton conductivity of the proton exchange membrane can be effectively improved or the metal ion permeability can be significantly reduced. However, the inability to achieve both has greatly affected the application of the proton exchange membrane in liquid flow batteries.

[0005] Therefore, the preparation of high-performance proton exchange membranes with low metal ion permeability and excellent proton conductivity is an important direction for the new generation of flow battery membranes. Summary of the Invention

[0006] The present invention provides a method for preparing a proton exchange membrane and its application. The present invention is based on the inventor's discovery and understanding of the following facts and problems: in the application of simple functional resins in liquid flow batteries, the problem of not being able to achieve both high proton transport capacity and low ion permeation rate affects the application performance of the proton exchange membrane. Therefore, it is urgently necessary to adopt the method of adding additives to achieve the improvement of the ion selectivity of the proton exchange membrane and obtain a high-performance proton exchange membrane.

[0007] The present invention proposes a proton exchange membrane based on sulfonated MXene. By adding sulfonated MXene materials, this composite membrane solves the problem of being unable to achieve both proton conduction and ion permeation. While reducing the vanadium ion permeation rate, the proton conduction capacity of the proton exchange membrane is further improved on the basis of pure MXene, making it a proton exchange membrane with excellent comprehensive performance, including high proton conductivity, low vanadium ion permeability, and excellent ion selectivity. Specifically, the present invention adopts the following technical means:

[0008] A method for preparing a proton exchange membrane, characterized in that a functional resin and an additive are blended to form a membrane, wherein the functional resin comprises one or more of perfluorosulfonic acid resin, polybenzimidazole resin, polyetheretherketone resin, polyimide resin, polyethersulfone resin, and polysulfone resin; and the additive is sulfonated MXene;

[0009] In terms of mass fraction, the functional resin accounts for 80-99.9%, and the additive accounts for 0.1-20%, preferably 0.5-5%.

[0010] Furthermore, the preparation method of the sulfonated MXene is:

[0011] A: Add LiF to a strong acid solution and stir at room temperature until the LiF salt is completely dissolved. The ratio of LiF to strong acid is 1:3-5 by mass.

[0012] B: Gradually adding an inorganic metal carbonitride to the mixed solution in step A above, reacting under stirring at a temperature of 25 to 50° C. for 5 to 48 hours, washing the resulting solution with a 0.1 to 10 mol / L strong alkaline solution, then washing with deionized water at least 3 to 10 times to remove residues, and collecting the solid precipitate by centrifugation until the pH value of the supernatant is close to neutral; the ratio of LiF to inorganic metal carbonitride by mass is 1:0.4 to 1.

[0013] C: Deionized water is added to the solid sediment obtained in step B, and the solution is ultrasonically treated in an ice-water bath for 10-180 minutes. The suspension is then centrifuged for 10-60 minutes to collect the MXene colloidal suspension, which is then freeze-dried for 8-48 hours to obtain a MXene multilayer two-dimensional nanomaterial and stored at 2-8°C.

[0014] D: The MXene multilayer two-dimensional nanomaterial in step C is placed in pure water and stirred at room temperature, preferably, the stirring time is 8-24 hours, and the colloidal suspension obtained after stirring is ultrasonically treated in an ice-water bath, preferably, the ultrasonic treatment time is 2-4 hours, and then the suspension obtained is centrifuged for 10-120 minutes and the supernatant is collected and filtered, for example, the supernatant can be filtered using a porous PTFE filter, and the filtered solid is dried to obtain a few-layer MXene product, wherein the drying treatment can be drying in an oven at 30-80° C. for 8-48 hours;

[0015] E: The few-layer MXene nanomaterial prepared in step D is dispersed in a polar solvent, a protonic acid containing a sulfonic acid group is added, and the sulfonic acid group is grafted onto the MXene surface through a dehydration condensation reaction by a post-sulfonation method to prepare a sulfonated MXene.

[0016] Furthermore, in step B, the reaction time is 5-24 hours.

[0017] Furthermore, in step A, the strong acid is a 3 mol / l hydrochloric acid solution, and in step B, the strong base is potassium hydroxide (KOH).

[0018] Furthermore, in step B, the inorganic metal carbonitride is one or a combination of Ti3AlC2, Ti4AlC3, Ti2AlC, V3AlC2 or V2AlC, preferably Ti3AlC2.

[0019] Furthermore, in the step C, the number of layers of the final multilayer MXene product is 4-9 layers, and in the step D, the number of layers of the final few-layer MXene product is 1-3 layers.

[0020] Furthermore, in step D, the terminal group on the outer metal surface of the final product of the few-layer MXene is one or a combination of O, S, Cl, F, and OH, preferably OH.

[0021] The present invention uses LiF and HCl to make MXene generate more -OH and reduce the generation of -F. Secondly, during the stirring reaction, controlling the reaction temperature to 25-50°C and the reaction time to 5-24 hours can also reduce the generation of -F. Thirdly, selecting a strong alkaline solution KOH for post-washing treatment can promote the removal of -F and increase the -OH content. In this way, the MXene basically retains a large number of -OH groups.

[0022] The present invention controls the terminal group of the outer metal surface of the final product of the few-layer MXene to be -OH, which has the following advantages: -OH is easy to modify and can undergo grafting reaction with functional reagents, making the MXene easy to be sulfonated; secondly, -OH has proton conductivity, which can promote the transmission of protons to a certain extent and reduce the internal resistance of the membrane.

[0023] Furthermore, in step E, the protonic acid includes one or a combination of sulfuric acid, chlorosulfonic acid, 1,4-butanesultone and sulfonic anhydride, wherein concentrated sulfuric acid is preferred.

[0024] Furthermore, in step E, the reaction conditions of the dehydration condensation reaction are: stirring at 50-80° C. for 0.5-24 h, followed by centrifugation, washing, and drying.

[0025] Furthermore, the specific method of the blending film is: after the functional resin and the sulfonated MXene are mixed to prepare a casting liquid, the film is formed by one or more methods including doctor blade film forming, mold film forming, spray film forming and extrusion film forming, and volatilized at 25°C to 200°C for 0.5h-48h to prepare a composite proton exchange membrane.

[0026] The present invention also discloses a proton exchange membrane, which is prepared by any of the above-mentioned methods for preparing the proton exchange membrane.

[0027] The invention also discloses the application of the proton exchange membrane for preparing a liquid flow battery.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention performs a sulfonation reaction on MXene and adds the sulfonated MXene to the proton exchange membrane. On the one hand, the flaky two-dimensional structure can effectively block the penetration of metal ions and reduce the cross-contamination of metal ions on both sides of the liquid electrolyte; on the other hand, the sulfonated MXene has extremely excellent proton conductivity. The -OH groups and sulfonic acid groups on the surface can transport protons in a variety of ways, thereby improving the proton conductivity of the proton exchange membrane, thereby obtaining a composite proton exchange membrane with excellent comprehensive performance of low ion permeability, high proton conductivity, excellent ion selectivity and mechanical properties. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to the following examples and comparative examples. It should be noted that the following examples are intended to facilitate understanding of the present invention and do not have any limiting effect on the present invention.

[0031] The reagents used in the examples and comparative examples are all common commercially available products.

[0032] The performance indicators of the proton exchange membranes prepared in the Examples and Comparative Examples were tested in accordance with NB / T42080-2023, General Technical Specifications and Test Methods for Ion Conducting Membranes for All-Vanadium Redox Flow Batteries. Proton conductivity was measured using an electrochemical impedance spectroscopy (EIS) instrument (CHI 604E, Shanghai Chenhua Instrument Co., Ltd.) at 45°C and 100% relative humidity.

[0033] Example 1

[0034] Step 1: Add 5g of LiF to 20g of 3mol / L HCl solution and stir at room temperature until the LiF salt is completely dissolved;

[0035] Step 2: Then 5 g of Ti3AlC2 was gradually added to the above mixed solution and stirred at 35 °C for 16 hours. The resulting solution was washed with 5 mol / L KOH solution and then washed with deionized water 5 times to remove the residue. The solid sediment was collected by centrifugation until the pH value of the supernatant was close to neutral.

[0036] Step 3: Deionized water was added to the solid sediment, and the solution was treated with ultrasound in an ice water bath for 60 min. The suspension was then centrifuged for 20 min to collect the MXene colloidal suspension. After that, the suspension was freeze-dried for 24 h to obtain 9 layers of Ti3C2T x 2D nanomaterials and stored at 2 °C.

[0037] Step 4: Prepare the Ti3C2T x The multilayer two-dimensional nanomaterial was stirred in pure water at room temperature for 24 hours, and the colloidal suspension obtained after stirring was ultrasonically treated in an ice water bath for 2 hours, and then the suspension was centrifuged for 30 minutes and the supernatant was collected. Finally, the supernatant was filtered using a porous PTFE filter, and the filtered solid was dried in an oven at 80°C for 48 hours to obtain the final three-layer Ti3C2T with terminal groups mainly -OH. x Nanomaterials.

[0038] Step 5: Prepared Ti3C2T x Add 2 mol / L H2SO4 solution, stir mechanically at 50℃ for 8 hours, filter, wash with water until neutral, and dry to obtain sulfonic acid functionalized sulfonated Ti3C2T x .

[0039] Step 6: Add perfluorosulfonic acid resin powder into DMF to prepare a resin solution with a solid content of 25%, and add three layers of Ti3C2T3 accounting for 0.5% of the resin mass. x The nanomaterials are evenly dispersed, cast into a membrane by solution casting, and dried at 80°C for 24 hours to obtain a composite proton exchange membrane with a thickness of 50 μm.

[0040] Example 2

[0041] The difference from Example 1 is that in the second step, stirring was performed at 30°C for 8 hours.

[0042] The other steps are exactly the same as those in Example 1.

[0043] Example 3

[0044] The difference from Example 1 is that in the second step, the obtained solution is washed with 3 mol / L KOH solution.

[0045] The other steps are exactly the same as those in Example 1.

[0046] Example 4

[0047] The difference from Example 2 is that in the second step, 2g of Ti3AlC2 is gradually added to the above mixed solution.

[0048] The other steps are exactly the same as those in Example 2.

[0049] Example 5

[0050] The difference from Example 4 is that in the first step, 5 g of LiF was added to 15 g of 3 mol / L HCl solution and stirred at room temperature until the LiF salt was completely dissolved.

[0051] The other steps are exactly the same as those in Example 4.

[0052] Example 6

[0053] The difference from Example 5 is that in the fourth step, the solution was treated with ultrasound in an ice-water bath for 120 min, and then the suspension was centrifuged for 60 min to collect the MXene colloidal suspension, which was then freeze-dried for 24 hours to obtain 9 layers of Ti3C2T x 2D nanomaterials and stored at 2°C;

[0054] In the fifth step, the filtered solid was dried in an oven at 80 °C for 48 h to obtain the final single-layer Ti3C2T x Nanomaterials.

[0055] The other steps are exactly the same as those in Example 5.

[0056] Example 7

[0057] The difference from Example 6 is that in the sixth step, a single layer of Ti3C2T3 accounting for 2% of the resin mass is added. x Nanomaterials,

[0058] The other steps are exactly the same as those in Example 6.

[0059] Example 8

[0060] The difference from Example 1 is that in the second step, 5g of Ti3AlC2 was added to the mixed solution and stirred at 50°C for 5 hours.

[0061] The other steps are exactly the same as those in Example 1.

[0062] Example 9

[0063] The difference from Example 1 is that in the second step, 5g of Ti3AlC2 was added to the mixed solution and stirred at 25°C for 24 hours.

[0064] The other steps are exactly the same as those in Example 1.

[0065] Example 10

[0066] The difference from Example 1 is that in the fifth step, the prepared Ti3C2T x Add 2 mol / L H2SO4 solution, stir mechanically at 80℃ for 24 hours, filter, wash with water until neutral, and dry to obtain sulfonic acid functionalized sulfonated Ti3C2T x ,

[0067] The other steps are exactly the same as those in Example 1.

[0068] Example 11

[0069] The difference from Example 1 is that in the second step, 5g of V3AlC2 was added to the mixed solution and stirred at 35°C for 16 hours.

[0070] The other steps are exactly the same as those in Example 1.

[0071] Comparative Example 1

[0072] A certain amount of perfluorosulfonic acid resin powder was added to DMF to prepare a resin solution with a solid content of 25%. The solution was cast into a membrane by solution casting, and then dried at 80°C for 24 hours to obtain a proton exchange membrane with a thickness of 50 μm.

[0073] Comparative Example 2

[0074] The difference from Example 6 is that the prepared single-layer structure of Ti3C2T x After the nanomaterial is prepared, the unsulfonated single-layer Ti3C2T is directly used without sulfonation treatment. x The composite proton exchange membrane was prepared using nanomaterials, and the other processing procedures were exactly the same as those in Example 6.

[0075] Comparative Example 3

[0076] The difference from Example 1 is that no multilayer Ti3C2T x The 9 layers of Ti3C2T prepared by exfoliation of two-dimensional nanomaterials xThe two-dimensional nanomaterial was directly added into 2 mol / L H2SO4 solution and mechanically stirred at 50℃ for 8 hours. The sulfonic acid functionalized sulfonated Ti3C2T was obtained by filtration, washing with water until neutrality, and drying. x .

[0077] The other steps are exactly the same as those in Example 1.

[0078] Comparative Example 4

[0079] The difference from Example 1 is that the prepared three-layer Ti3C2T x The nanomaterial was added into 2 mol / L silane coupling agent and mechanically stirred at 50 °C for 8 hours. The product was filtered, washed with water until neutral, and dried to obtain amino (-NH2) functionalized aminated Ti3C2T x .

[0080] The other steps are exactly the same as those in Example 1.

[0081] Comparative Example 5

[0082] The difference from Example 1 is that in the second step, 5g Ti3AlC2 was added to the mixed solution and stirred at 80°C for 3 hours.

[0083] The other steps are exactly the same as those in Example 1.

[0084] Comparative Example 6

[0085] The difference from Example 1 is that in the second step, 5 g of Ti3AlC2 was added to the mixed solution and stirred at 15°C for 30 hours.

[0086] The other steps are exactly the same as those in Example 1.

[0087] Table 1 is a table showing the dimensional change rate, mechanical strength, proton conductivity, ion permeability and ion selectivity of the proton exchange membranes prepared in Examples and Comparative Examples.

[0088] Table 1

[0089]

[0090] The test results of Examples 1 to 11 above show that a composite proton exchange membrane with relatively excellent comprehensive performance can be prepared by adopting the preparation method provided by the present invention.

Claims

1. A method for preparing a proton exchange membrane, characterized in that: The film is formed by blending functional resins and additives; The functional resin includes one or a combination of perfluorosulfonic acid resin, polybenzimidazole resin, polyetheretherketone resin, polyimide resin, polyethersulfone resin and polysulfone resin; the additive is sulfonated MXene; Calculated by mass fraction, the functional resin accounts for 80-99.9%, and the additive accounts for 0.1-20%; The preparation method of the sulfonated MXene is: A: Add LiF to a strong acid solution and stir at room temperature until the LiF is completely dissolved; B: adding an inorganic metal carbonitride to the mixed solution of step A, reacting under stirring at a temperature of 25 to 50° C. for 5 to 24 hours, washing the resulting solution with a 0.1-10 mol / L strong alkaline solution, and then washing with deionized water at least 3 to 10 times to remove residues, and collecting the solid sediment by centrifugation until the pH value of the supernatant is close to neutral; C: Deionized water is added to the solid sediment obtained in step B, and the solution is ultrasonically treated in an ice water bath for 10-180 minutes. The suspension is then centrifuged for 10-60 minutes, and the MXene colloidal suspension is collected. The MXene colloidal suspension is then freeze-dried for 8-48 hours to obtain a MXene multilayer two-dimensional nanomaterial, which is then stored at 2-8°C. D: The MXene multilayer two-dimensional nanomaterial prepared in step C is placed in pure water and stirred at room temperature. The colloidal suspension obtained after stirring is ultrasonically treated in an ice-water bath. The suspension is then centrifuged for 10 to 120 minutes and the supernatant is collected. The supernatant is filtered and the filtered solid is dried to obtain a few-layer MXene product. E: The few-layer MXene product prepared in step D is dispersed in a polar solvent, a protonic acid containing a sulfonic acid group is added, and the sulfonic acid group is grafted onto the MXene surface by a dehydration condensation reaction through a post-sulfonation method to prepare a sulfonated MXene; In step A, the strong acid is 3 mol / L hydrochloric acid, and in step B, the strong base is potassium hydroxide.

2. The method for preparing a proton exchange membrane according to claim 1, wherein: The proportion of the additive is 0.5~5%.

3. The method for preparing a proton exchange membrane according to claim 1, wherein: The inorganic metal carbonitride is one or a combination of Ti3AlC2, Ti4AlC3, Ti2AlC, V3AlC2 or V2AlC.

4. The method for preparing a proton exchange membrane according to claim 1, wherein: The inorganic metal carbonitride is Ti3AlC2; In step C, the final multilayer MXene product has 4 to 9 layers; In step D, the final product of the few-layer MXene has 1-3 layers; In the step E, the protonic acid includes one or a combination of sulfuric acid, chlorosulfonic acid, 1,4-butanesultone and sulfonic anhydride.

5. The method for preparing a proton exchange membrane according to claim 1, wherein: In the step E: The protonic acid is concentrated sulfuric acid; The reaction conditions for the dehydration condensation reaction by the post-sulfonation method are: stirring and reacting at 50-100° C. for 0.5-24 hours, followed by centrifugation, washing, and drying.

6. The method for preparing a proton exchange membrane according to claim 1, wherein: The specific method of the blending membrane is: functional resin and sulfonated MXene are mixed to prepare a casting solution, and then a membrane is formed by one or more methods of doctor blade film forming, mold film forming, spray film forming and extrusion film forming, and volatilized at 25°C to 200°C for 0.5h-48h to prepare a composite proton exchange membrane.

7. A proton exchange membrane, characterized in that The proton exchange membrane is prepared by the method for preparing the proton exchange membrane according to any one of claims 1 to 6.

8. The use of the proton exchange membrane according to claim 7, characterized in that: Used to prepare liquid flow batteries.

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