Preparation and application of a composite ion-conducting membrane

Abstract

This invention discloses the preparation and application of a composite ion-conducting membrane. The process includes the following steps: Under an inert atmosphere, a catalyst and a four-membered aromatic amine are mixed and heated with stirring to obtain a homogeneous system; a diaromatic carboxylic acid or its derivative is added to the homogeneous system, and after heating and stirring, the mixture is washed to obtain a base membrane resin; the base membrane resin is dissolved in an organic solvent, and additives are added; after ultrasonic treatment, the target ion-conducting membrane is obtained by casting. The ion-conducting membrane prepared by this invention exhibits good electrical properties and mechanical strength, with a coulombic efficiency of up to 95.6%, a voltage efficiency of up to 93.2%, an energy efficiency of up to 87.9%, a tensile strength exceeding 110 MPa, and an elongation at break as high as 2877%. All performance characteristics are significantly higher than those of existing ion-conducting membranes. This invention can be applied to the preparation of various flow batteries.

Description

Technical Field

[0001] This invention relates to a method for preparing an ion-conducting membrane, and more particularly to a method for preparing a composite ion-conducting membrane for use in flow batteries. Background Technology

[0002] In the core structure of flow batteries, the ion-conducting membrane plays a crucial role. It serves not only as a barrier to the interpenetration of vanadium ions in the positive and negative electrolytes but also as a channel for hydrogen ion flow, forming a closed-loop battery. Its performance directly impacts the overall efficiency of the entire battery system. An ideal ion-conducting membrane should combine high ion selectivity, excellent ion conductivity, superior chemical stability, and economical cost. Existing commercial membrane materials, such as the perfluorosulfonic acid ion-conducting membrane (Nafion) produced by DuPont, while exhibiting stable performance, suffer from insufficient ion selectivity and high cost, hindering their widespread industrial application. Non-fluorinated ion-conducting membranes are characterized by low cost, high thermal stability and mechanical strength, and good ion selectivity. These membrane materials achieve precise separation of conductive ions and protons through a fine pore size sieving mechanism and charge repulsion effect; however, their relatively low conductivity remains a key factor restricting their further commercial application. Therefore, current research is focused on developing an ion-conducting membrane that combines high conductivity with excellent vanadium ion blocking performance, in order to further reduce overall costs while ensuring the efficient and stable operation of flow batteries and promote the industrial application of all-vanadium redox flow battery energy storage technology. Summary of the Invention

[0003] Objective of this invention: The objective of this invention is to provide a method for preparing a composite ion-conducting membrane, thus solving the problem of how to prepare a composite ion-conducting membrane. Another objective of this invention is to propose an application of the composite ion-conducting membrane in flow batteries, thereby addressing the problem of how to improve the performance of flow batteries.

[0004] Technical solution: The preparation method of the composite ion-conducting membrane of the present invention includes the following steps:

[0005] (1) Under an inert atmosphere, the catalyst and a four-membered aromatic amine were mixed and heated and stirred to obtain a homogeneous system;

[0006] (2) Add a diaromatic carboxylic acid or its derivative to the homogeneous system, heat and stir to react, and then wash to obtain the base film resin.

[0007] (3) The base film resin is dissolved in an organic solvent and additives are added. After ultrasonic treatment, the target ion-conducting membrane is obtained by casting.

[0008] The resin obtained by polymerizing quaternary aromatic amines and diaromatic carboxylic acids has a polybenzimidazole structure with a highly stable aromatic ring backbone in the main chain, exhibiting stronger stability in highly oxidizing and acidic electrolyte environments. However, this type of material has low conductivity, which manifests as reduced voltage efficiency in practical applications, adversely affecting battery performance. By adding additives, an ion-conducting membrane with both high vanadium ion conductivity and high electrical conductivity is obtained. This improves membrane conductivity while forming a microphase separation structure within the membrane, further optimizing the pore distribution of the ion-conducting membrane and enhancing proton conductivity.

[0009] Preferably, in step (1), the catalyst includes at least one of sulfuric acid, hydrochloric acid, polyphosphoric acid, phosphorus pentoxide, p-toluenesulfonic acid, aluminum trichloride, ferric chloride, and boron trifluoride; the quaternary aromatic amine includes at least one of 3,3'-diaminobenzidine, 3,3',4,4'-tetraaminodiphenylmethane, 3,3',4,4'-tetraaminodiphenyl ether, 3,3',4,4'-tetraaminodiphenyl sulfide, and 1,2,5,6-tetraaminonaphthalene.

[0010] Preferably, in step (1), the molar ratio of the catalyst to the quaternary aromatic amine is 0.5-5:100.

[0011] Preferably, in step (1), the inert atmosphere is at least one of nitrogen, helium, and argon introduced into the reaction vessel, and the heating condition is to raise the temperature to 150-300°C.

[0012] Preferably, in step (2), the diaromatic carboxylic acid or its derivative includes at least one of dimethyl 1,4-phthalate, 1,3-phthalic acid, 1,4-phthalic acid, 1,3-phenylenediacetic acid, 1,4-phenylenediacetic acid, diphenyl 1,3-phthalate, 1,3-phthaloyl chloride, and 1,4-phthaloyl chloride.

[0013] Preferably, in step (2), a diaromatic carboxylic acid or its derivative is added to the homogeneous system at a molar ratio of 1-5:1-5 between a tetraaromatic amine and a diaromatic carboxylic acid or its derivative; the heating method is to heat to 40-60°C and gradually increase the temperature to 200°C in stages over 24-36 hours.

[0014] Preferably, in step (2), the washing method is to cool the reaction product, pour it into a poor solvent, filter to obtain the precipitate, and then wash it with deionized water to obtain the base film resin.

[0015] Preferably, in step (2), the undesirable solvent includes at least one of water, methanol, ethanol, isopropanol, and acetone.

[0016] Preferably, in step (3), the organic solvent includes at least one of dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide; the additive includes at least one of bismuth vanadate, bismuth molybdate, and bismuth tungstate; and the weight ratio of the additive to the base film resin is 0.01-0.1:100.

[0017] Another aspect of the present invention discloses the application of the composite ion-conducting membrane prepared by the above-described method in a flow battery.

[0018] In some embodiments, the flow battery includes one of a vanadium redox flow battery, a zinc / bromine flow battery, a zinc / iodine flow battery, an iron / chromium flow battery, or a vanadium / bromine flow battery.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The ion-conducting membrane prepared by the present invention has better electrical properties and mechanical strength, with a coulombic efficiency of up to 95.6%, a voltage efficiency of up to 93.2%, an energy efficiency of up to 87.9%, a tensile strength of over 110 MPa, and an elongation at break of up to 2877%. All of these properties are significantly higher than those of existing ion-conducting membranes. Attached Figure Description

[0020] Figure 1 This is a microstructure diagram of the surface of the ion-conducting membrane prepared in Example 3. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0022] Example 1: A method for preparing an ion-conducting membrane is as follows:

[0023] (1) Add p-toluenesulfonic acid to a round-bottom flask, purge with nitrogen and stir, add 3,3'-diaminobenzidine to the flask, the molar ratio of p-toluenesulfonic acid to 3,3'-diaminobenzidine is 0.5:100, heat to 150℃ and stir for 2h until a homogeneous system is formed;

[0024] (2) After turning off the heating and cooling to room temperature, add dimethyl 1,4-phthalate. The molar ratio of 3,3'-diaminobenzidine to dimethyl 1,4-phthalate is 1:1. Stir and heat to 50°C and keep warm for 6 hours. Then continue to heat to 100°C and keep warm for 6 hours. Continue to heat to 150°C and keep warm for 6 hours. Finally, heat to 200°C and keep warm for 6 hours to obtain the base film resin. After cooling, pour the base film resin into water, filter the precipitate and wash away the residual catalyst and unreacted substances on the surface of the resin with deionized water.

[0025] (3) The base film resin was dissolved in N-methylpyrrolidone at a material-to-liquid ratio of 20g:100mL. Bismuth vanadate was added, with a weight ratio of bismuth vanadate to base film resin of 0.05:100. After ultrasonic treatment, the target ion-conducting membrane was obtained by casting. Figure 1 As shown.

[0026] Example 2: A method for preparing an ion-conducting membrane is as follows:

[0027] (1) Add sulfuric acid to a round-bottom flask, introduce helium gas and stir, add 3,3',4,4'-tetraaminodiphenylmethane to the flask, the molar ratio of sulfuric acid to 3,3',4,4'-tetraaminodiphenylmethane is 1:100, heat to 300℃ and stir for 1h until a homogeneous system is formed;

[0028] (2) After turning off the heating and cooling to room temperature, add 1,3-phthalic acid. The molar ratio of 3,3',4,4'-tetraaminodiphenylmethane to 1,3-phthalic acid is 1:5. Stir and heat to 60°C and keep warm for 8 hours. Then continue to heat to 130°C and keep warm for 8 hours. Continue to heat to 200°C and keep warm for 8 hours to obtain the base film resin. After cooling, pour the base film resin into methanol, filter the precipitate and wash away the residual catalyst and unreacted substances on the surface of the resin with deionized water.

[0029] (3) The base film resin was transferred to dimethyl sulfoxide and dissolved in a material-liquid ratio of 15g:100mL. Bismuth molybdate was added, and the weight ratio of bismuth molybdate to base film resin was 0.01:100. After ultrasonic treatment, the target ion-conducting membrane was obtained by casting.

[0030] Example 3: A method for preparing an ion-conducting membrane is as follows:

[0031] (1) Add polyphosphoric acid to a round-bottom flask, introduce argon gas and stir, add 3,3',4,4'-tetraaminodiphenyl ether to the flask, the molar ratio of polyphosphoric acid to 3,3',4,4'-tetraaminodiphenyl ether is 2:100, heat to 200℃, stir for 3h until a homogeneous system is formed;

[0032] (2) After turning off the heating and cooling to room temperature, add 1,3-phenylenediacetic acid, and the molar ratio of 3,3',4,4'-tetraaminodiphenyl ether to 1,3-phenylenediacetic acid is 5:1. Stir and heat to 40°C and keep warm for 6 hours. Then continue to heat to 100°C and keep warm for 6 hours. Continue to heat to 150°C and keep warm for 6 hours. Finally, heat to 200°C and keep warm for 6 hours to obtain the base film resin. After cooling, pour the base film resin into isopropanol, filter the precipitate and wash away the residual catalyst and unreacted substances on the surface of the resin with deionized water.

[0033] (3) The base film resin was transferred to dimethylacetamide and dissolved at a material-to-liquid ratio of 10g:100mL. Bismuth tungstate was added, and the weight ratio of bismuth tungstate to base film resin was 0.1:100. After ultrasonic treatment, the target ion-conducting membrane was obtained by casting.

[0034] Example 4: Everything else is the same as in Example 1, except that:

[0035] Replace p-toluenesulfonic acid with hydrochloric acid, and replace 3,3'-diaminobenzidine with 3,3',4,4'-tetraaminodiphenyl sulfide; the molar ratio of hydrochloric acid to 3,3',4,4'-tetraaminodiphenyl sulfide is 5:100.

[0036] Replace dimethyl 1,4-phthalate with 1,4-phthalic acid;

[0037] Pour the cooled base film resin into ethanol;

[0038] The base film resin was transferred to N,N-dimethylformamide and dissolved.

[0039] Example 5: Everything else is the same as in Example 1, except that:

[0040] Replace p-toluenesulfonic acid with phosphorus pentoxide, and replace 3,3'-diaminobenzidine with 1,2,5,6-tetraaminonaphthalene;

[0041] Replace dimethyl 1,4-phthalate with 1,4-phenylenediacetic acid;

[0042] Pour the cooled base film resin into acetone.

[0043] Example 6: Everything else is the same as in Example 1, except that:

[0044] Replace p-toluenesulfonic acid with aluminum trichloride;

[0045] Replace dimethyl 1,4-phthalate with diphenyl 1,3-phthalate:

[0046] Example 7: The rest is the same as Example 1, except that...

[0047] Replace p-toluenesulfonic acid with ferric chloride, and replace 3,3'-diaminobenzidine with 1,2,5,6-tetraaminonaphthalene;

[0048] Replace 1,4-dimethyl phthalate with 1,3-phthaloyl chloride;

[0049] Pour the cooled base film resin into acetone.

[0050] Example 8: Everything else is the same as in Example 1, except that:

[0051] Replace p-toluenesulfonic acid with boron trifluoride, and replace 3,3'-diaminobenzidine with 3,3',4,4'-tetraaminodiphenyl sulfide;

[0052] Replace dimethyl 1,4-phthalate with 1,4-phthaloyl chloride;

[0053] The base film resin was transferred to N,N-dimethylformamide and dissolved.

[0054] Example 9: The rest is the same as in Example 1, except that:

[0055] Replace p-toluenesulfonic acid with phosphorus pentoxide.

[0056] Example 10: Everything else is the same as in Example 1, except that:

[0057] Replace bismuth vanadate with bismuth molybdate.

[0058] Comparative Example 1: Everything else is the same as in Example 1, except that:

[0059] Bismuth vanadate is not added.

[0060] Comparative Example 2: Commercially available Nafion 117 was used as the test sample, and its thickness was the same as that of the ion-conducting membrane prepared in Example 3.

[0061] The mechanical and electrical properties of the ion exchange membranes in Examples 1-10 and Comparative Examples 1-2 were tested using the following methods:

[0062] Tensile strength and elongation at break can characterize the tensile properties of the comparative and exemplary samples, thus reflecting their mechanical strength to a certain extent. Tensile strength and elongation at break were tested using a universal testing machine. Before testing, the comparative and exemplary samples were soaked in ultrapure water for 24 hours, then cut into 1cm × 5cm pieces. These pieces were placed in the test fixture, with the longitudinal axis of the sample coinciding with the line connecting the centers of the upper and lower fixtures, and then clamped tightly. The required load and corresponding film thickness and width were read from the measured tensile curves, and the tensile strength and elongation at break were calculated.

[0063] To investigate the practical application effects of the comparative and embodiment examples, single-cell performance testing is required to determine their coulombic efficiency, voltage efficiency, and energy efficiency. Single-cell performance testing is performed using a charge-discharge testing system with a preset cutoff voltage of 1–1.65V and a current density of 200 mA·cm⁻¹. -2 .

[0064] Table 1 Performance test results of ion-conducting membranes prepared by different methods

[0065]

[0066] Table 1 shows that the ion-conducting membrane prepared by this invention has excellent mechanical and electrical properties, with the upper limits of each property exceeding those of existing ion-conducting membranes. Furthermore, the addition of bismuth-containing additives can significantly improve the performance of the ion-conducting membrane.

Claims

1. A method for preparing a composite ion-conducting membrane, characterized in that, Includes the following steps: (1) Under an inert atmosphere, the catalyst and a four-membered aromatic amine are mixed and heated and stirred to obtain a homogeneous system; (2) Add a diaromatic carboxylic acid or its derivative to a homogeneous system, heat and stir to react, and then wash to obtain the base film resin; (3) The base film resin was dissolved in an organic solvent and additives were added. After ultrasonic treatment, the target ion-conducting membrane was obtained by casting. In step (1), the catalyst includes at least one of sulfuric acid, hydrochloric acid, polyphosphoric acid, phosphorus pentoxide, p-toluenesulfonic acid, aluminum trichloride, ferric chloride, and boron trifluoride; the quaternary aromatic amine includes at least one of 3,3'-diaminobenzidine, 3,3',4,4'-tetraaminodiphenylmethane, 3,3',4,4'-tetraaminodiphenyl ether, 3,3',4,4'-tetraaminodiphenyl sulfide, and 1,2,5,6-tetraaminonaphthalene. In step (2), the diaromatic carboxylic acid or its derivative includes at least one of 1,3-phthalic acid, 1,4-phthalic acid, 1,3-phenylenediacetic acid, 1,4-phenylenediacetic acid, diphenyl 1,3-phthalic acid, 1,3-phthaloyl chloride, and 1,4-phthaloyl chloride. The additives include at least one of bismuth vanadate, bismuth molybdate, and bismuth tungstate.

2. The method for preparing the composite ion-conducting membrane according to claim 1, characterized in that, In step (1), the molar ratio of the catalyst to the quaternary aromatic amine is 0.5-5:

100.

3. The method for preparing the composite ion-conducting membrane according to claim 1, characterized in that, In step (1), the inert atmosphere is at least one of nitrogen, helium, and argon introduced into the reaction vessel, and the heating condition is to raise the temperature to 150-300℃.

4. The method for preparing the composite ion-conducting membrane according to claim 1, characterized in that, In step (2), a diaromatic carboxylic acid or its derivative is added to the homogeneous system at a molar ratio of 1-5:1-5 between a tetraaromatic amine and a diaromatic carboxylic acid or its derivative; the heating method is to heat to 40-60℃ and gradually increase the temperature to 200℃ in stages over 24-36 hours.

5. The method for preparing the composite ion-conducting membrane according to claim 1, characterized in that, In step (2), the washing method is to cool the reaction product, pour it into a poor solvent, filter to obtain the precipitate, and then wash it with deionized water to obtain the base film resin.

6. The method for preparing the composite ion-conducting membrane according to claim 5, characterized in that, In step (2), the undesirable solvent includes at least one of water, methanol, ethanol, isopropanol, and acetone.

7. The method for preparing the composite ion-conducting membrane according to claim 1, characterized in that, In step (3), the organic solvent includes at least one of dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide; the weight ratio of the additive to the base film resin is 0.01-0.1:

100.

8. The application of the composite ion-conducting membrane prepared by any one of claims 1-7 in a flow battery.

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