Preparation and application of high-stability and high-elasticity flow battery membrane material

Abstract

The application provides a high-stability and high-elasticity membrane material for a flow battery, and specifically relates to a membrane prepared by mixing a rigid polymer and a high-elasticity polymer and applied to a flow battery. The application combines the characteristics of high mechanical strength, low cost, high efficiency and good stability of the rigid polymer membrane and the characteristics of good toughness and tensile strength of the high-elasticity polymer membrane, and prepares a high-stability and high-elasticity membrane material. The preparation method of the membrane material is simple, the membrane is uniform, and the membrane material is suitable for batch preparation. The membrane material has high mechanical strength, high efficiency, good stability, good toughness and good tensile strength. The proportion of the rigid polymer and the high-elasticity polymer can be adjusted according to different application requirements, the size and pore size distribution of the membrane material are controllable, and the application range of the flow battery membrane material is widened.

Description

Technical Field

[0001] This invention provides a membrane material for batteries, and particularly relates to its application in the field of flow batteries. Background Technology

[0002] In recent years, there has been a growing call for the use of renewable and clean energy. However, renewable energy power generation, such as wind and solar power, is significantly discontinuous and unstable due to seasonal, meteorological, and geographical conditions. Large-scale energy storage technology is considered a strategic technology to support the widespread adoption of renewable energy and has received high attention from governments and businesses worldwide. Among various energy storage technologies, flow battery technology has garnered even wider attention due to its advantages such as independently designable capacity and power, high flexibility, high capacity, wide range of applications, long cycle life, and safety and environmental friendliness.

[0003] In flow batteries, membrane materials are a crucial component, accounting for a significant proportion of the battery cost. Therefore, developing low-cost, high-performance, and stable battery membrane materials is a vital approach to reducing battery costs and improving performance. Among the raw materials for membrane fabrication, rigid polymers possess advantages such as high mechanical strength, low cost, and good stability, thus attracting considerable attention from researchers. However, most membrane materials prepared from rigid polymers exhibit deformation due to changes in the operating medium and temperature, leading to a decline in battery performance. Summary of the Invention

[0004] To address the above technical problems, this invention proposes to use a mixture of rigid polymers and highly elastic polymers to form a membrane for use in flow batteries, in order to avoid the degradation of battery performance caused by membrane material deformation due to changes in the medium and temperature environment during the use of the membrane material.

[0005] The specific technical solution of this invention is as follows:

[0006] A flow battery membrane material is prepared by mixing raw materials comprising a rigid polymer and a high-elastic polymer. The high-elastic polymer can be one or more of thermoplastic vulcanized rubber, thermoplastic polyurethane, thermoplastic polyester elastomer, SBS elastomer, and POE elastomer. The rigid polymer can be one or more of polybenzimidazole, polyethersulfone, polysulfone, etc. The mass ratio of the rigid polymer to the high-elastic polymer is 50-1:1.

[0007] Based on the above scheme, preferably, the high-elastic polymer is thermoplastic polyurethane; the rigid polymer is polybenzimidazole or polyethersulfone.

[0008] Based on the above scheme, preferably, the mass ratio of rigid polymer to high elastic polymer is 25-3:1, and more preferably 25-5:1.

[0009] Based on the above scheme, preferably, the thickness of the membrane material is 60-200μm.

[0010] The membrane material can be prepared by the following method:

[0011] 1) Mix rigid polymer and high elastic polymer in a certain proportion and dissolve them in a solvent. Stir at a temperature of 30-80℃ for more than 10 hours to obtain a solution;

[0012] If necessary, add the pore-forming agent to the solution prepared in step 1) and stir at room temperature for more than 2 hours to obtain the film-forming solution; the mass concentration of the pore-forming agent is between 1-5% (if no pore-forming agent is needed, then the solution obtained in step 1 is the film-forming solution).

[0013] 2) Coat the membrane-forming solution onto a flat plate and form a membrane using the solvent evaporation method at a temperature of 50-80℃ for a evaporation time of not less than 10 minutes; thus obtaining the membrane material.

[0014] Based on the above scheme, preferably, the solvent can be at least one of toluene, dichloromethane, and dichloroethane, or at least one of toluene, dichloromethane, and dichloroethane mixed with solvent gasoline.

[0015] Based on the above scheme, preferably, the pore-forming agent includes one or more of polyvinylpyrrolidone, polydiallyl dimethyl ammonium chloride, dibutyl phthalate, and dimethyl phthalate.

[0016] The membrane material produced by this invention can be applied to fields such as vanadium-based flow batteries and zinc-based flow batteries.

[0017] Beneficial results of the present invention:

[0018] 1. This invention is the first to propose the idea of ​​mixing rigid polymers with highly elastic polymers to prepare membranes, and applies the prepared membrane materials to the field of flow batteries;

[0019] 2. This invention combines a rigid polymer with a specific high-elasticity polymer to prepare a highly stable and highly elastic membrane material, which solves the problem of battery performance degradation caused by membrane material deformation due to changes in the medium and temperature environment during membrane material use.

[0020] 3. The preparation method of the membrane material of the present invention is simple, the film formation is uniform, and it is suitable for large-scale production;

[0021] 4. Membrane materials have high mechanical strength, high efficiency, good stability, good toughness, and good tensile strength;

[0022] 5. The ratio of rigid polymer to high-elastic polymer can be adjusted according to the needs of flow batteries, and the size and pore size distribution of the membrane material are controllable;

[0023] 6. This invention broadens the application scope of flow battery membrane materials. Attached Figure Description

[0024] Figure 1 This is a comparison chart of the multi-cycle coulombic efficiency test data of Example 13 and Comparative Example 3. Detailed Implementation

[0025] The following embodiments are further illustrations of the present invention and are not intended to limit the scope of the invention.

[0026] Example 1

[0027] The rigid polymer chosen is commercially available polybenzimidazole, and the elastic polymer is thermoplastic polyurethane.

[0028] Take 10g of polybenzimidazole, 2g of thermoplastic polyurethane, and 88g of toluene. Place the three in a container and stir at 50℃ for 15 hours to prepare a film-forming solution. Coat the film-forming solution onto a plate and form a film using the solvent evaporation method at 50℃ for 30 minutes. The thickness of the resulting film material is 80μm.

[0029] The prepared membrane material was subjected to mechanical property testing, showing a Young's modulus of 3.56 GPa, a tensile strength of 125 MPa, and an elongation at break of 95%. For flow battery performance testing, this invention uses an all-vanadium redox flow battery as an example: the electrode area of ​​a single cell is 50 cm². 2 60 mL of vanadium electrolyte was added to each of the positive and negative electrode storage tanks. The electrolyte contained vanadium in a 3.5 valence state (a mass ratio of 1:1 for trivalent and tetravalent vanadium), with a vanadium concentration of 1.5 mol / L and a sulfuric acid concentration of 3 mol / L. The operating current density was 80 mA·cm⁻¹. -2 Under constant current charge and discharge conditions, the coulombic efficiency is 99.5%, the voltage efficiency is 83.1%, and the energy efficiency is 82.7%.

[0030] Examples 2-6

[0031] In Examples 2-6, the rigid polymer used was the same polybenzimidazole as in Example 1; the film thickness and solvent used in the film-forming solution were the same as in Example 1; the test conditions and procedures for the single cell were the same as in Example 1 (all parameters and units were the same), except that:

[0032] The effects of different ratios of rigid polymer polybenzimidazole and high-elastic polymer thermoplastic polyurethane on the mechanical properties of the membrane material and the battery performance were investigated by adding different amounts of rigid polymer polybenzimidazole and high-elastic polymer thermoplastic polyurethane to the membrane solution.

[0033] Table 1 Summary of Test Data for Examples 2-6

[0034]

[0035] The data obtained from Examples 1-6 show that, with a fixed total amount of film-forming solution, the mechanical properties of the membrane material increase with the increase of the high-elasticity polymer thermoplastic polyurethane, but the voltage efficiency of a single cell decreases. The membrane material exhibits optimal overall performance when the film-forming solution contains 10g of polybenzimidazole, 2g of thermoplastic polyurethane, and 88g of toluene.

[0036] Example 7

[0037] The rigid polymer chosen is commercially available polyethersulfone, the high-elastic polymer is thermoplastic polyurethane, and the pore-forming agent is polyvinylpyrrolidone.

[0038] Take 16g of polyethersulfone, 2g of thermoplastic polyurethane, 2g of polyvinylpyrrolidone, and 80g of toluene. Place the four ingredients in a container and stir at 50°C for 15 hours to prepare a film-forming solution. Coat the film-forming solution onto a plate and form a film using the solvent evaporation method at 50°C for 30 minutes. The thickness of the resulting film material is 65μm.

[0039] The prepared membrane material was subjected to mechanical property testing, showing a Young's modulus of 750 MPa, a tensile strength of 65 MPa, and an elongation at break of 83%. For flow battery performance testing, this invention uses a vanadium redox flow battery as an example: the electrode area of ​​a single cell is 50 cm². 2 60 mL of vanadium electrolyte was added to each of the positive and negative electrode storage tanks. The electrolyte contained vanadium in a 3.5 valence state (a mass ratio of 1:1 for trivalent and tetravalent vanadium), with a vanadium concentration of 1.5 mol / L and a sulfuric acid concentration of 3 mol / L. The operating current density was 80 mA·cm⁻¹. -2 Under constant current charge and discharge conditions, the coulombic efficiency is 98.3%, the voltage efficiency is 85.1%, and the energy efficiency is 83.7%.

[0040] Examples 8-12

[0041] In Examples 8-12, the rigid polymer used was the same polyethersulfone as in Example 7, and the amount of pore-forming agent polyvinylpyrrolidone added was the same as in Example 7; the film thickness and the solvent used in the film-forming solution were the same as in Example 7; the test conditions and procedures for the single cell were the same as in Example 7 (all parameters and units were the same), except that:

[0042] The effects of different amounts of rigid polymer polyethersulfone and high-elastic polymer thermoplastic polyurethane added to the membrane-forming solution on the mechanical properties of the membrane material and the battery performance were investigated.

[0043] Table 2 Summary of Test Data for Examples 8-12

[0044]

[0045]

[0046] The data obtained from Examples 8-12 show that, with a fixed total amount of film-forming solution, the mechanical properties of the membrane material increase with the increase of the high-elasticity polymer thermoplastic polyurethane, while the voltage efficiency of the single cell decreases. The membrane material exhibits optimal overall performance when the film-forming solution contains 16g of polyethersulfone, 2g of thermoplastic polyurethane, 2g of polyvinylpyrrolidone, and 80g of toluene.

[0047] Example 13

[0048] The rigid polymer chosen is commercially available polyethersulfone, the high-elastic polymer is thermoplastic polyurethane, and the pore-forming agent is polyvinylpyrrolidone.

[0049] Take 16g of polyethersulfone, 2g of thermoplastic polyurethane, 2g of polyvinylpyrrolidone, and 80g of toluene. Place the three in a container and stir at 50°C for 15 hours to prepare a film-forming solution. Coat the film-forming solution onto a plate and form a film using the solvent evaporation method at 50°C for 30 minutes. The thickness of the resulting film material is 65μm.

[0050] The prepared membrane material was subjected to mechanical property testing, showing a Young's modulus of 750 MPa, a tensile strength of 65 MPa, and an elongation at break of 83%. For flow battery performance testing, this invention uses a vanadium redox flow battery as an example: the electrode area of ​​a single cell is 50 cm². 2 60 mL of vanadium electrolyte was added to each of the positive and negative electrode storage tanks. The electrolyte contained vanadium in a 3.5 valence state (a mass ratio of 1:1 for trivalent and tetravalent vanadium), with a vanadium concentration of 1.5 mol / L and a sulfuric acid concentration of 3 mol / L. The operating current density was 80 mA·cm⁻¹. -2 Constant current charge and discharge were performed at different temperatures under the conditions, and the test data are shown in Table 3.

[0051] Table 3 Summary of test data for Example 13 and Comparative Example 3

[0052]

[0053] Comparative Example 1

[0054] 11.8g of commercially available polybenzimidazole, 0.2g of thermoplastic polyurethane (a high-elasticity polymer), and 88g of toluene were selected and placed in a container and stirred at 50°C for 15 hours to prepare a film-forming solution. The film-forming solution was coated onto a plate and a film was formed by solvent evaporation at 50°C for 30 minutes, resulting in a film material with a thickness of 80μm.

[0055] The prepared membrane material was subjected to mechanical property tests, showing a Young's modulus of 2.36 GPa, a tensile strength of 88 MPa, and an elongation at break of 55%. Flow battery performance was also tested, using a vanadium redox flow battery as an example: the electrode area of ​​a single cell was 50 cm². 2 60 mL of vanadium electrolyte was added to each of the positive and negative electrode storage tanks. The electrolyte contained vanadium in a 3.5 valence state (a mass ratio of 1:1 for trivalent and tetravalent vanadium), with a vanadium concentration of 1.5 mol / L and a sulfuric acid concentration of 3 mol / L. The operating current density was 80 mA·cm⁻¹. -2 Under constant current charge and discharge conditions, the coulombic efficiency is 99.1%, the voltage efficiency is 84.1%, and the energy efficiency is 83.3%.

[0056] Comparative Example 2

[0057] 17.8g of commercially available polyethersulfone, 0.2g of thermoplastic polyurethane, 2g of polyvinylpyrrolidone, and 80g of toluene were selected and placed in a container and stirred at 50°C for 15 hours to prepare a film-forming solution. The film-forming solution was coated on a plate and a film was formed by solvent evaporation at 50°C for 30 minutes, resulting in a film material with a thickness of 65μm.

[0058] The prepared membrane material was subjected to mechanical property tests, with a Young's modulus of 325 MPa, tensile strength of 23 MPa, and elongation at break of 25%. Flow battery performance was also tested, using a vanadium redox flow battery as an example: the electrode area of ​​a single cell was 50 cm². 2 60 mL of vanadium electrolyte was added to each of the positive and negative electrode storage tanks. The electrolyte contained vanadium in a 3.5 valence state (a mass ratio of 1:1 for trivalent and tetravalent vanadium), with a vanadium concentration of 1.5 mol / L and a sulfuric acid concentration of 3 mol / L. The operating current density was 80 mA·cm⁻¹. -2 Under constant current charge and discharge conditions, the coulombic efficiency is 97.1%, the voltage efficiency is 86.9%, and the energy efficiency is 84.4%.

[0059] Comparative Example 3

[0060] 18g of commercially available polyethersulfone, 2g of polyvinylpyrrolidone, and 80g of toluene were selected and placed in a container and stirred at 50°C for 15 hours to prepare a membrane-forming solution. The membrane-forming solution was coated on a plate and a membrane was formed by solvent evaporation at 50°C for 30 minutes, resulting in a membrane material with a thickness of 65μm.

[0061] The prepared membrane material was subjected to mechanical property tests, showing a Young's modulus of 305 MPa, a tensile strength of 21 MPa, and an elongation at break of 15%. Flow battery performance was also tested, using a vanadium redox flow battery as an example: the electrode area of ​​a single cell was 50 cm². 260 mL of vanadium electrolyte was added to each of the positive and negative electrode storage tanks. The electrolyte contained vanadium in a 3.5 valence state (a mass ratio of 1:1 for trivalent and tetravalent vanadium), with a vanadium concentration of 1.5 mol / L and a sulfuric acid concentration of 3 mol / L. The operating current density was 80 mA·cm⁻¹. -2 Constant current charge and discharge under different conditions and constant current charge and discharge at different temperatures are shown in Table 3.

[0062] The test data from Example 13 and Comparative Example 3 show that as the temperature gradually increases, the coulombic efficiency of the membrane material prepared with the addition of the high-elasticity polymer does not change significantly with increasing temperature, indicating that it has a stronger ability to hinder inion migration. In contrast, the coulombic efficiency of the membrane material without the addition of the high-elasticity polymer decreases significantly with increasing temperature. Therefore, the membrane material prepared with the addition of the high-elasticity polymer has a greater advantage in operating under high-temperature conditions.

[0063] Following the conditions of Example 13 and Comparative Example 3, the test temperature was set to 45°C, and the cyclic stability of the membrane material was further tested. The obtained coulombic efficiency test data are as follows: Figure 1 As shown:

[0064] As can be seen from the comparison chart of the multi-cycle coulombic efficiency test data of Example 13 and Comparative Example 3, at a test temperature of 45°C, the battery assembled using the membrane material prepared with the addition of the high-elasticity polymer showed no decrease in coulombic efficiency after nearly 100 cycles; while the battery assembled using the membrane material without the addition of the high-elasticity polymer showed a significant decrease in coulombic efficiency after 70 cycles. Therefore, the membrane material prepared with the addition of the high-elasticity polymer has a greater advantage in cycle stability under high-temperature conditions.

[0065] In summary, composite membrane materials made from rigid polymers and highly elastic polymers can significantly improve the mechanical properties of membrane materials. By optimizing the ratio of the two, the mechanical and battery performance of the membrane material reaches its optimum when the mass concentration of the highly elastic polymer is 2%. Furthermore, the addition of the highly elastic polymer significantly improves the high-temperature testing performance and cycle stability of the membrane material.

Claims

1. A flow battery membrane material, characterized in that: The membrane material is prepared by mixing raw materials comprising a rigid polymer and a high-elastic polymer; the high-elastic polymer is one or more of thermoplastic vulcanized rubber, thermoplastic polyurethane, thermoplastic polyester elastomer, SBS elastomer, and POE elastomer; the rigid polymer is one or more of polybenzimidazole, polyethersulfone, and polysulfone; the mass ratio of the rigid polymer to the high-elastic polymer is 25. 5:1; The method for preparing the flow battery membrane material includes the following steps: 1) Mix the rigid polymer and the high-elastic polymer in a solvent, and heat at a temperature of 30°C. Stirring at 80°C for more than 10 hours yields a film-forming solution; or, mixing a rigid polymer and a high-elastic polymer in a solvent and stirring at 30°C... Stir at 80°C for more than 10 hours, then add the pore-forming agent and stir at room temperature for more than 2 hours to obtain the film-forming solution; 2) The film-forming solution is coated onto a flat plate, and the film is formed using the solvent evaporation method at a temperature of 50°C. The membrane material is obtained by evaporation at 80°C for at least 10 minutes. The solvent is at least one of toluene, dichloromethane, and dichloroethane, or a mixture of at least one of toluene, dichloromethane, and dichloroethane with solvent gasoline.

2. The flow battery membrane material according to claim 1, characterized in that: The high-elastic polymer is thermoplastic polyurethane; the rigid polymer is polybenzimidazole or polyethersulfone.

3. The flow battery membrane material according to claim 1, characterized in that: The thickness of the membrane material is 60. 200μm.

4. The flow battery membrane material according to claim 1, characterized in that: The mass concentration of the pore-forming agent in the film-forming solution is 1. 5%.

5. The flow battery membrane material according to claim 1, characterized in that: The pore-forming agent includes one or more of polyvinylpyrrolidone, polydiallyl dimethyl ammonium chloride, dibutyl phthalate, and dimethyl phthalate.

6. A claim 1 5. Application of any of the membrane materials described above in flow batteries.

Images