A sulfonated polyether ether ketone / polyaniline composite membrane, a preparation method and application thereof

Abstract

The application belongs to the technical field of all-vanadium redox flow battery separators, and specifically discloses a sulfonated polyether ether ketone / polyaniline composite membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing polyether ether ketone with concentrated sulfuric acid, heating and reacting in a water bath, and preparing sulfonated polyether ether ketone solids; mixing molybdenum disulfide with toluene, ultrasonicating, adding 1,3-propanesultone, and heating in an oil bath to prepare sulfonated molybdenum disulfide powder; mixing the sulfonated molybdenum disulfide powder, polyaniline and a DMF solution, stirring and ultrasonicating, adding sulfonated polyether ether ketone solids, stirring to obtain casting membrane slurry, coating on a glass plate, drying into a film, sequentially immersing in a sulfuric acid solution and deionized water, and obtaining the sulfonated polyether ether ketone / polyaniline composite membrane. The application discloses a sulfonated polyether ether ketone / polyaniline composite membrane as well as a preparation method and application thereof. The sulfonated polyether ether ketone / polyaniline composite membrane has high proton conductivity, can maintain a low vanadium ion permeability, and improves the electrochemical performance of an all-vanadium redox flow battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of all-vanadium redox flow battery separators, and particularly relates to a sulfonated polyether ether ketone / polyaniline composite membrane as well as a preparation method and application thereof. BACKGROUND

[0002] With the increasing global energy demand and the growing emphasis on environmental protection, the limitations of traditional fossil fuels become increasingly apparent, and energy transformation has become an inevitable trend. In this context, renewable energy sources such as solar and wind energy have gradually become an important part of energy supply. However, the intermittency and instability of these renewable energy sources require efficient energy storage technology to ensure stable power supply. As a highly efficient energy storage technology, all-vanadium redox flow batteries have gradually become a popular choice in large-scale energy storage due to their high safety, long cycle life, and environmental friendliness.

[0003] One of the core components of all-vanadium redox flow batteries is the proton exchange membrane, whose performance directly affects the service life, efficiency, and cost of the battery. Currently, the most widely used proton exchange membrane in commercial applications is the Nafion series of perfluorosulfonic acid membranes produced by DuPont Company in the United States. Although it has high conductivity and good durability, it has the problems of high cost and high vanadium ion permeability, which limits the large-scale commercial application of all-vanadium redox flow batteries.

[0004] Sulfonated polyether ether ketone (SPEEK) is considered a potential alternative to Nafion as a new type of separator material due to its low cost, simple preparation, and excellent mechanical and chemical stability. The sulfonic acid groups in its structure can promote proton transfer, while the rigid backbone helps to reduce vanadium ion permeability. However, the sulfonation degree of SPEEK significantly affects its performance: increasing the sulfonation degree can enhance the proton conductivity, but will increase the vanadium ion permeability; reducing the sulfonation degree will reduce the proton transport sites and lower the proton conductivity. Therefore, how to reduce vanadium ion permeability while improving the proton conductivity of SPEEK membranes has become a key research issue. SUMMARY

[0005] The present application aims to provide a sulfonated polyether ether ketone / polyaniline composite membrane and its preparation method and application, which has high proton conductivity and can maintain low vanadium ion permeability, thereby improving the electrochemical performance of all-vanadium redox flow batteries.

[0006] To solve the above technical problems, the technical solutions adopted by the present application are as follows:

[0007] A preparation method of a sulfonated polyether ether ketone / polyaniline composite membrane, comprising the following steps:

[0008] S1, mixing the dried polyether ether ketone with concentrated sulfuric acid, stirring uniformly, water bath heating, after reaction pouring into ice deionized water, stirring until coagulation into filamentous solid, deionized water cleaning until pH is neutral, drying, obtaining sulfonated polyether ether ketone solid;

[0009] S2, mixing the molybdenum disulfide with toluene uniformly, ultrasonic, adding 1,3-propane sulfonic acid lactone, oil bath stirring heating, cooling to room temperature, centrifugation, discarding supernatant, sequentially cleaning and soaking the precipitate with deionized water and anhydrous ethanol, twice centrifugation, drying, obtaining sulfonated molybdenum disulfide powder;

[0010] S3, mixing the sulfonated molybdenum disulfide powder obtained in S2, polyaniline and DMF solution, stirring, ultrasonic, adding the sulfonated polyether ether ketone solid obtained in S1, stirring until completely dissolved, obtaining casting film slurry;

[0011] S4, coating the casting film slurry obtained in S3 on a glass plate, room temperature standing until the slurry no longer flows, drying into film, sequentially placing in sulfuric acid solution with concentration of 1 mol / L and deionized water for soaking, obtaining sulfonated polyether ether ketone / polyaniline composite film.

[0012] Preferably, in S1, the water bath heating temperature is 50℃, and the water bath heating time is 2h.

[0013] Preferably, in S1, the drying temperature is 60-80℃, and the drying time is 12-24h.

[0014] Preferably, in S2, the ultrasonic power is 600W, and the ultrasonic time is 1h.

[0015] Preferably, in S2, the oil bath heating temperature is 110℃, and the oil bath heating time is 24h.

[0016] Preferably, in S2, the centrifugation speed is 10000rpm, and the centrifugation time is 5-8min.

[0017] Preferably, in S2, the twice centrifugation speed is 10000rpm, and the twice centrifugation time is 5-8min.

[0018] Preferably, in S2, the drying temperature is room temperature, and the drying time is 24h.

[0019] Preferably, in S3, the ultrasonic temperature is 20-25℃, the ultrasonic power is 600W, and the ultrasonic time is 40-50min.

[0020] Preferably, in S3, the mass ratio of polyaniline and sulfonated polyether ether ketone solid is 2:98; the mass ratio of total mass of polyaniline and sulfonated polyether ether ketone solid and sulfonated molybdenum disulfide is 99-99.75:0.25-1.

[0021] Preferably, the mass ratio of the total mass of the polyaniline and the sulfonated polyether ether ketone to the mass of the sulfonated molybdenum disulfide is one of 99.75:0.25, 99.5:0.5 or 99:1.

[0022] Preferably, in S3, the mass-volume ratio of the sulfonated polyether ether ketone and the DMF solution is 2.592 g:19.44 mL.

[0023] Preferably, in S4, the drying and film-forming process is as follows: 80℃ air drying for 24h, and 100℃ vacuum drying for 24h.

[0024] The application also provides a sulfonated polyether ether ketone / polyaniline composite film prepared by the preparation method.

[0025] The application also provides an application of the sulfonated polyether ether ketone / polyaniline composite film or the sulfonated polyether ether ketone / polyaniline composite film prepared by the preparation method in a vanadium redox flow battery.

[0026] Compared with the prior art, the application has the following advantages and technical effects:

[0027] The application discloses a sulfonated polyether ether ketone / polyaniline composite film, a preparation method and application thereof. Through acid-base reaction between amino groups in polyaniline and sulfonic acid groups in a sulfonated polyether ether ketone matrix, strong acid-base electrostatic interaction and rich hydrogen bond networks are formed, which not only enhances the interfacial bonding force, but also accelerates proton conduction, and significantly improves the proton conductivity of the composite film. Meanwhile, sulfonic acid groups grafted on sulfonated molybdenum disulfide further provide proton transport sites and promote proton transport; the layered structure increases the complexity of vanadium ion permeation paths, effectively hinders vanadium ion permeation, and greatly reduces the vanadium ion permeation rate.

[0028] In addition, the composite film also has good mechanical strength, chemical stability and thermal stability, and the comprehensive performance is significantly optimized. The preparation process of the application is simple and efficient, easy to scale up, and has excellent performance in a vanadium redox flow battery, significantly improves the battery efficiency and cycle stability, and has important practical application value and broad development prospects.

[0029] The technical solutions of the application are further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 An energy efficiency comparison chart of the composite films provided for Example 2, Comparative Example 1 and Comparative Example 2;

[0031] Figure 2 A battery capacity comparison chart of the composite films provided for Example 2, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0034] Source of experimental materials:

[0035] Polyetheretherketone (PEEK): Mv-35000, purchased from Maclean Biotechnology Co., Ltd.; Molybdenum disulfide: 99.5%, purchased from Shanghai Aladdin Biotechnology Co., Ltd.; 1,3-propanesulfonic acid lactone: 99%, purchased from Shanghai Aladdin Biotechnology Co., Ltd.; Polyaniline: 98%, purchased from Maclean Biotechnology Co., Ltd.; Concentrated sulfuric acid: 99.8%, purchased from Modern Oriental (Beijing) Technology Development Co., Ltd.; Toluene: 99.7%, purchased from Maclean Biotechnology Co., Ltd.; N,N-Dimethylformamide: 99.5%, purchased from Maclean Biotechnology Co., Ltd.; Nafion 212, purchased from DuPont, USA; Anhydrous ethanol: 99.7%, purchased from Maclean Biotechnology Co., Ltd.

[0036] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0037] Example 1

[0038] A method for preparing a sulfonated polyetheretherketone / polyaniline composite film includes the following steps:

[0039] S1. Weigh 10g of polyether ether ketone solid and dry it in a forced-air environment at 60℃ for 24h. Slowly pour the dried polyether ether ketone into a beaker containing 150mL of concentrated sulfuric acid and stir rapidly. Stir at room temperature for 24h to ensure that the polyether ether ketone is completely dissolved in the concentrated sulfuric acid. Heat in a water bath at 50℃ for 2h. After the reaction, slowly pour it into ice-cold deionized water and stir until it solidifies into a white filamentous solid. Wash with deionized water until the pH is neutral. Dry it in a forced-air environment at 60℃ and 80℃ for 12h in sequence to obtain sulfonated polyether ether ketone solid with a sulfonation degree of 69.8%.

[0040] S2, 3g of molybdenum disulfide was mixed with 30 mL of toluene at room temperature for 30 min, the mixed solution was put into an ultrasonic machine for 1 h, the ultrasonic power was 600 W, 1.2g of 1,3-propane sultone was added, and the stirring was continued at room temperature for 15 min, then the solution was heated at 110°C for 24 h, and then cooled to room temperature, centrifuged at 10000 rpm for 5 min, the supernatant was discarded, and the precipitate was washed and soaked with deionized water and anhydrous ethanol, respectively, for three times to remove the residual toluene and 1,3-propane sultone on the surface, and then centrifuged at 10000 rpm for 5 min, and dried at room temperature under vacuum for 24 h to obtain sulfonated molybdenum disulfide powder;

[0041] S3, 6.6 mg of sulfonated molybdenum disulfide powder obtained in S2 (mass concentration 0.25%) was mixed with 52.9 mg of polyaniline and 19.44 mL of DMF solution, and stirred at 20°C, and then ultrasonic treated for 40 min, the ultrasonic power was 600 W, 2.592 g of sulfonated polyether ether ketone obtained in S1 was added, and the stirring was continued until the solid was completely dissolved to obtain a casting film slurry;

[0042] S4, the casting film slurry obtained in S3 was coated on a 18 cm x 18 cm glass plate placed horizontally, and then the glass plate was placed at room temperature until the slurry stopped flowing, and then dried at 80°C for 24 h, and then dried at 100°C under vacuum for 24 h, and then the film was removed from the glass plate, and then immersed in a 1 mol / L H2SO4 solution for 48 h to protonate the film, and then the film was washed with deionized water to remove the excess acid on the surface, and then immersed in deionized water for 48 h to remove the residual sulfuric acid in the film, and finally the treated film was immersed in deionized water for standby, and then a sulfonated polyether ether ketone / polyaniline composite film S / PANI-(s-MoS2)-0.25 was obtained.

[0043] Example Two

[0044] The preparation method was the same as that in Example One, except that the amount of sulfonated molybdenum disulfide powder added in step S3 was 13.3 mg, and the mass concentration was 0.5%, and a sulfonated polyether ether ketone / polyaniline composite film S / PANI-(s-MoS2)-0.5 was obtained.

[0045] Example Three

[0046] The preparation method was the same as that in Example One, except that the amount of sulfonated molybdenum disulfide powder added in step S3 was 26.7 mg, and the mass concentration was 1%, and a sulfonated polyether ether ketone / polyaniline composite film S / PANI-(s-MoS2)-,1 was obtained.

[0047] Comparative Example One

[0048] Nafion 212 film purchased from DuPont Company, USA.

[0049] Comparative Example Two

[0050] S1. Weigh 10g of polyether ether ketone solid and dry it in a forced-air environment at 60℃ for 24h. Slowly pour the dried polyether ether ketone into a beaker containing 150mL of concentrated sulfuric acid and stir rapidly. Stir at room temperature for 24h to ensure that the polyether ether ketone is completely dissolved in the concentrated sulfuric acid. Heat in a water bath at 50℃ for 2h. After the reaction, slowly pour it into ice-cold deionized water and stir until it solidifies into a white filamentous solid. Wash with deionized water until the pH is neutral. Dry it in a forced-air environment at 60℃ and 80℃ for 12h in sequence to obtain sulfonated polyether ether ketone solid with a sulfonation degree of 69.8%.

[0051] S2. Add 2.59g of sulfonated polyether ether ketone to 19.44mL of DMF and stir until the sulfonated polyether ether ketone is completely dissolved to form a transparent casting slurry. Coat the transparent casting slurry evenly onto a horizontally placed 18cm×18cm glass plate and let it stand at room temperature until the DMF evaporates and the slurry no longer flows. Then, dry it at 80℃ for 24h under forced air and at 100℃ under vacuum for 24h. After drying, peel the membrane off the glass plate and immerse it in a 1mol / L H2SO4 solution for 48h to fully protonate the membrane. Then, rinse the membrane with deionized water to remove excess acid from the surface and immerse it in deionized water for 48h to remove residual sulfuric acid. Finally, immerse the treated membrane in deionized water for later use to obtain the sulfonated polyether ether ketone (SPEEK) membrane.

[0052] The performance of the diaphragms provided in Examples 1-3 and Comparative Examples 1-2 was tested through the following experiments.

[0053] 1. Testing of membrane water absorption rate, swelling rate, ion exchange capacity, and proton conductivity.

[0054] The prepared membrane was cut into rectangular sample strips of 1cm × 5cm, soaked in deionized water for 24 hours, then removed and quickly wiped dry with lint-free paper. The quality (W) of the wet membrane was immediately tested. wet (g) and length (L) wet (cm). Subsequently, the film was dried in a forced-air drying oven at 80°C for 24 hours, and the quality of the dry film (W) was immediately tested. dry (g) and length (L) dry (cm). Three samples were tested for each group of membranes, and the average value was taken as the final result. The water absorption rate and swelling rate of the membrane were calculated using formulas (1) and (2):

[0055]

[0056] Weigh a certain mass of dry film and soak it in 40 mL of 1 mol L⁻¹ solution. -1The membrane was taken out and rinsed with deionized water to remove residual solution. 0.01 mol L -1 The NaCl solution containing hydrogen ions was titrated with NaOH solution, and phenolphthalein solution was used as the titration end point indicator. The ion exchange capacity of the membrane was calculated by formula (3):

[0057]

[0058] The proton conductivity of the membrane was tested by CHI760E electrochemical workstation of Shanghai Chenhua Instrument Co., Ltd. using two-electrode alternating current impedance method (EIS). First, the sample membrane to be tested was cut into a 1 cm x 5 cm strip and clamped in the middle of a custom conductivity test fixture, immersed in deionized water, and after the open circuit voltage was stable, the alternating current impedance test was performed. Test conditions: the initial test voltage is the open circuit voltage, the frequency range is 0.1 Hz-1 MHz, and the voltage amplitude is 10 mV. After the alternating current impedance test, the membrane was taken out, wiped dry and immediately measured the thickness of the membrane (d, μm) with a thickness gauge. In the Nyquist plot obtained by the alternating current impedance method, the abscissa corresponding to the intersection of the spectrum curve with the real axis at high frequency can be considered as the resistance (R, Ω) of the membrane. The proton conductivity of the membrane was calculated by formula (4):

[0059]

[0060] Where L (cm) is the distance between the two electrodes of the fixture, i.e. the length of the actual tested membrane; b (cm) is the width of the sample membrane, which is 1 cm in this paper; 10 7 is the calculation coefficient when the data unit is the unit given in this paper.

[0061] The test results of the water absorption, swelling rate, ion exchange capacity and proton conductivity of the membrane are shown in Table 1.

[0062] Table 1 Test results of water absorption, swelling rate, ion exchange capacity and proton conductivity of the membrane

[0063]

[0064]

[0065] As can be seen from Table 1, the composite membranes of Example 1-Example 3 have high water absorption, good hydrophilicity and low swelling rate, good mechanical properties, high ion exchange capacity, and a large number of exchangeable protons in the membrane, which are significantly improved compared with the Nafion 212 provided by Comparative Example 1 and the sulfonated polyether ether ketone membrane provided by Comparative Example 2.

[0066] 2. The separators of Example 2 and Comparative Examples 1-2 were used in full-liquid- return flow batteries to perform battery charge-discharge tests.

[0067] The influence of the separators on the performance of VRB batteries was evaluated using a battery test system. The prepared separators were assembled into batteries and connected to a blue-ice test system to perform battery rate charge-discharge cycling tests. The energy efficiencies of the batteries with the separators of Example 2 and Comparative Examples 1-2 at different current densities are shown in Table 2, and the comparison of the energy efficiencies is shown in Figure 1 Figure 2

[0068] It should be noted that, during the battery test, in order to avoid the hydrogen evolution and oxygen evolution reactions and the corrosion of the graphite plate caused by excessively low or high voltage, the charge cut-off voltage was set to 1.65 V, and the discharge cut-off voltage was set to 0.8 V. However, for Comparative Example 1, the initial charge-discharge voltage of the assembled battery reached the set values of 1.65 V and 0.8 V at a current density of 200 mA cm -2

[0069] Table 2. Energy efficiencies of batteries with different separators at different current densities

[0070]

[0071]

[0072] Table 3. Capacities of batteries with different separators at the first cycle at different current densities

[0073]

[0074] From the above results, it can be seen that the proton conductivity of the composite separator is significantly improved due to the formation of a large number of hydrogen bond networks by the amino groups in polyaniline and the provision of additional proton transport sites by the sulfonic acid groups in s-MoS2. The voltage drop caused by the resistance of the separator is reduced in the battery test. During the rate charge-discharge process, the energy efficiency of the battery assembled with the separator of Example 2 is significantly higher than that of the batteries assembled with the separators of Comparative Examples 1 and 2. Furthermore, the penetration path of vanadium ions becomes complex and tortuous due to the laminar s-MoS2, and the penetration of vanadium ions is further hindered by the acid-base pair. The battery assembled with the separator of Example 2 still has a higher capacity at a larger current density, which is much higher than that of the batteries assembled with the separators of Comparative Examples 1 and 2.

[0075] ​​​The application provides a sulfonated polyether ether ketone / polyaniline composite film and a preparation method and application thereof, and the composite film has excellent physical performance (water absorption and swelling rate) and high conductivity, the prepared composite film is used in a full vanadium redox flow battery, excellent rate charge and discharge performance is obtained, the energy efficiency of the battery is improved, higher battery capacity is obtained, and the problem that the proton conductivity of the sulfonated polyether ether ketone film is difficult to break through under the condition that the vanadium ion permeability is low is solved.

[0076] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, but not to limit them. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. Use of a sulfonated polyether ether ketone / polyaniline composite membrane in a vanadium redox flow battery, characterized in that, The preparation method of the sulfonated polyether ether ketone / polyaniline composite film comprises the following steps: S1, mixing the dried polyether ether ketone with concentrated sulfuric acid, stirring uniformly, water bath heating, pouring into ice deionized water after reaction, stirring to coagulation into filamentous solid, deionized water cleaning to neutral pH, drying, obtaining sulfonated polyether ether ketone solid; S2, mixing the molybdenum disulfide with toluene uniformly, ultrasonic, adding 1,3-propanesultone, oil bath stirring heating, cooling to room temperature, centrifugation, discarding supernatant, sequentially cleaning and soaking the precipitate with deionized water and anhydrous ethanol, twice centrifugation, drying, obtaining sulfonated molybdenum disulfide powder; S3, mixing the sulfonated molybdenum disulfide powder obtained in S2, polyaniline and DMF solution, stirring, ultrasonic, adding the sulfonated polyether ether ketone solid obtained in S1, stirring to completely dissolve, obtaining casting film slurry; S4, coating the casting film slurry obtained in S3 on a glass plate, room temperature standing until the slurry no longer flows, drying into a film, sequentially immersing in a 1 mol / L sulfuric acid solution and deionized water, obtaining a sulfonated polyether ether ketone / polyaniline composite film; In S3, the mass ratio of polyaniline and sulfonated polyether ether ketone solid is 2:98; the mass ratio of the total mass of polyaniline and sulfonated polyether ether ketone solid to sulfonated molybdenum disulfide is 99-99.75:0.25-1.

2. Use according to claim 1, characterized in that, In S1, the water bath heating temperature is 50℃, and the water bath heating time is 2h.

3. Use according to claim 1, characterized in that, In S2, the ultrasonic power is 600W, and the ultrasonic time is 1h.

4. The use according to claim 1, characterized in that, In S2, the oil bath heating temperature is 110℃, and the oil bath heating time is 24h.

5. The use according to claim 1, characterized in that, In S3, the ultrasonic temperature is 20-25℃, the ultrasonic power is 600W, and the ultrasonic time is 40-50min.

6. The use according to claim 1, characterized in that, In S3, the mass-volume ratio of sulfonated polyether ether ketone and DMF solution is 2.592g:19.44mL.

7. Use according to claim 1, characterized in that, In S4, the specific process flow of the drying into a film is: 80℃ air drying for 24h, and 100℃ vacuum drying for 24h.

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