Sulfonated polyetheretherketone / polyaniline composite membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of all-vanadium redox flow battery diaphragms, and particularly discloses a sulfonated polyetheretherketone / polyaniline composite membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing polyetheretherketone and concentrated sulfuric acid, and carrying out water bath heating reaction to prepare a sulfonated polyetheretherketone solid; molybdenum disulfide and methylbenzene are mixed and subjected to ultrasonic treatment, 1, 3-propane sultone is added, oil bath heating is conducted, and sulfonated molybdenum disulfide powder is prepared; the preparation method comprises the following steps: mixing and stirring sulfonated molybdenum disulfide powder, polyaniline and a DMF (Dimethyl Formamide) solution, performing ultrasonic treatment, adding a sulfonated polyether-ether-ketone solid, stirring to obtain membrane casting slurry, coating a glass plate with the membrane casting slurry, drying to form a membrane, and soaking the membrane in a sulfuric acid solution and deionized water in sequence to obtain the sulfonated polyether-ether-ketone / polyaniline composite membrane. The invention discloses a sulfonated polyetheretherketone / polyaniline composite membrane as well as a preparation method and application thereof. The sulfonated polyetheretherketone / polyaniline composite membrane has high proton conductivity, can maintain relatively low vanadium ion permeability and can improve the electrochemical performance of an all-vanadium redox flow battery.

Description

Technical Field

[0001] The invention belongs to the technical field of all-vanadium liquid flow battery diaphragms, and specifically relates to a sulfonated polyetheretherketone / polyaniline composite membrane and a preparation method and application thereof. Background Art

[0002] With the continuous growth of global energy demand and the increasing attention to environmental protection, the limitations of traditional fossil fuels have become increasingly obvious, and energy transformation has become an inevitable trend. In this context, renewable energy sources such as solar energy and wind energy have gradually become an important part of energy supply. However, the intermittent and unstable nature of these renewable energy sources requires efficient energy storage technology to ensure the stability of power supply. As an efficient energy storage technology, all-vanadium liquid flow battery has gradually become a popular choice in the field of large-scale energy storage due to its advantages such as high safety, long cycle life and environmental friendliness.

[0003] One of the core components of all-vanadium flow batteries is the proton exchange membrane, whose performance directly affects the battery's service life, efficiency and cost. At present, the most widely used proton exchange membrane in commercial applications is the Nafion series perfluorosulfonic acid membrane produced by DuPont 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 flow batteries.

[0004] Sulfonated polyetheretherketone (SPEEK) is considered to be a new type of diaphragm material with the potential to replace Nafion 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 main chain helps to reduce the permeability of vanadium ions. However, the sulfonation degree of SPEEK has a significant impact on its performance: although increasing the sulfonation degree can enhance proton conductivity, it will increase vanadium ion permeation; reducing the sulfonation degree will reduce proton transfer sites and reduce proton conductivity. Therefore, how to improve the proton conductivity of SPEEK membrane while reducing the permeability of vanadium ions has become the key to current research. Summary of the invention

[0005] The present invention aims to provide a sulfonated polyetheretherketone / polyaniline composite membrane and a preparation method and application thereof. The sulfonated polyetheretherketone / polyaniline composite membrane has high proton conductivity, can maintain a low vanadium ion permeability, and improve the electrochemical performance of an all-vanadium liquid flow battery.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a sulfonated polyetheretherketone / polyaniline composite membrane comprises the following steps:

[0008] S1, mixing the dried polyetheretherketone with concentrated sulfuric acid, stirring evenly, heating in a water bath, pouring into ice deionized water after the reaction, stirring until solidified into a filamentous solid, washing with deionized water until the pH is neutral, and drying to obtain a sulfonated polyetheretherketone solid;

[0009] S2, mixing molybdenum disulfide and toluene evenly, ultrasonicating, adding 1,3-propane sultone, stirring and heating in an oil bath, cooling to room temperature, centrifuging, discarding the supernatant, washing and soaking the precipitate with deionized water and anhydrous ethanol in turn, centrifuging twice, and drying to obtain sulfonated molybdenum disulfide powder;

[0010] S3, mixing the sulfonated molybdenum disulfide powder, polyaniline and DMF solution obtained in S2, stirring, ultrasonicating, adding the sulfonated polyetheretherketone solid obtained in S1, stirring until completely dissolved, to obtain a casting slurry;

[0011] S4. Apply the casting slurry obtained in S3 onto a glass plate, let it stand at room temperature until the slurry no longer flows, dry it into a film, and soak it in a 1 mol / L sulfuric acid solution and deionized water in turn to obtain a sulfonated polyetheretherketone / polyaniline composite membrane.

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

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

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

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

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

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

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

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

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

[0021] Preferably, the mass ratio of the total mass of the polyaniline and sulfonated polyetheretherketone solids to 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 sulfonated polyetheretherketone and DMF solution is 2.592 g:19.44 mL.

[0023] Preferably, in S4, the specific process flow of drying and film forming is: forced air drying at 80° C. for 24 hours, and then vacuum drying at 100° C. for 24 hours.

[0024] The invention also provides the sulfonated polyetheretherketone / polyaniline composite membrane prepared by the preparation method.

[0025] The present invention also provides the use of the sulfonated polyetheretherketone / polyaniline composite membrane or the sulfonated polyetheretherketone / polyaniline composite membrane prepared by the preparation method in an all-vanadium redox flow battery.

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

[0027] The present invention discloses a sulfonated polyetheretherketone / polyaniline composite membrane and its preparation method and application. The amino groups in polyaniline react with the sulfonic acid groups in the sulfonated polyetheretherketone matrix to form a strong acid-base electrostatic interaction and a rich hydrogen bond network, which not only enhances the interfacial bonding force, but also accelerates proton conduction, significantly improving the proton conductivity of the composite membrane. At the same time, the sulfonic acid groups grafted on the sulfonated molybdenum disulfide further provide proton transfer sites to promote proton transfer; its layered structure increases the complexity of the vanadium ion penetration path, effectively hinders the penetration of vanadium ions, and greatly reduces the vanadium ion permeability.

[0028] In addition, the composite membrane also has good mechanical strength, chemical stability and thermal stability, and its comprehensive performance is significantly optimized. The preparation process of the invention is simple and efficient, easy to mass produce, and exhibits excellent performance in all-vanadium liquid flow batteries, significantly improving battery efficiency and cycle stability, and has important practical application value and broad development prospects.

[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A comparison chart of the energy efficiency of the composite membranes provided in Example 2, Comparative Example 1 and Comparative Example 2;

[0031] Figure 2 This is a comparison chart of the battery capacities of the composite membranes provided in Example 2, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0033] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0034] Source of test materials:

[0035] Polyetheretherketone: specification is Mv-35000, purchased from McLean Biochemical Technology Co., Ltd.; molybdenum disulfide: specification is 99.5%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; 1.3-propanesultone: specification is 99%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; polyaniline: specification is 98%, purchased from McLean Biochemical Technology Co., Ltd.; concentrated sulfuric acid: specification is 99.8%, purchased from Modern Oriental (Beijing) Technology Development Co., Ltd.; toluene: specification is 99.7%, purchased from McLean Biochemical Technology Co., Ltd.; N,N-dimethylformamide: specification is 99.5%, purchased from McLean Biochemical Technology Co., Ltd.; Nafion212 was purchased from DuPont of the United States; anhydrous ethanol: specification is 99.7%, purchased from McLean Biochemical Technology Co., Ltd.

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

[0037] Embodiment 1

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

[0039] S1. Weigh 10g of polyetheretherketone solid, dry it with air at 60°C for 24h, slowly pour the dried polyetheretherketone into a beaker containing 150mL of concentrated sulfuric acid, stir rapidly, stir at room temperature for 24h to ensure that the polyetheretherketone is completely dissolved in the concentrated sulfuric acid, heat it in a water bath at 50°C for 2h, slowly pour it into ice deionized water after the reaction, stir until it solidifies into a white filamentous solid, wash it with deionized water until the pH is neutral, and dry it with air at 60°C and 80°C for 12h, respectively, to obtain a sulfonated polyetheretherketone solid with a sulfonation degree of 69.8%;

[0040] S2, 3g of molybdenum disulfide and 30mL of toluene were stirred at room temperature for 30min to mix evenly, the mixed solution was placed in an ultrasonic machine for 1h, the ultrasonic power was 600W, 1.2g of 1,3-propane sultone was added, stirring was continued for 15min at room temperature, and then heated with stirring in an oil bath at 110°C for 24h, cooled to room temperature, centrifuged at 10000rpm for 5min, the supernatant was discarded, and the precipitate was washed and soaked with deionized water and anhydrous ethanol in turn, and the mixture was repeated three times to remove the residual toluene and 1.3-propane sultone on the surface, centrifuged twice at 10000rpm for 5min, and vacuum dried at room temperature for 24h to obtain sulfonated molybdenum disulfide powder;

[0041] S3, 6.6 mg of sulfonated molybdenum disulfide powder (mass concentration 0.25%) obtained from S2, 52.9 mg of polyaniline and 19.44 mL of DMF solution were mixed and stirred, and ultrasonicated for 40 min at 20°C with an ultrasonic power of 600 W, and 2.592 g of sulfonated polyetheretherketone solid obtained from S1 was added, and stirred until completely dissolved to obtain a casting slurry;

[0042] S4, the casting film slurry obtained in S3 was coated on a horizontally placed 18 cm × 18 cm glass plate, and allowed to stand at room temperature until the slurry no longer flowed, and then dried with air at 80 ° C for 24 h, and then vacuum dried at 100 ° C for 24 h. After drying, the film was peeled off the glass plate and heated in a 1 mol / L H 2 SO 4 The membrane was immersed in the solution for 48 hours to fully protonate the membrane, and then the membrane was rinsed with deionized water to remove excess acid on the surface, and then immersed in deionized water for 48 hours to remove residual sulfuric acid inside. Finally, the treated membrane was immersed in deionized water for standby use to obtain the sulfonated polyetheretherketone / polyaniline composite membrane S / PANI-(s-MoS 2 )-0.25.

[0043] Embodiment 2

[0044] The preparation method is the same as that of Example 1, except that in step S3, the amount of sulfonated molybdenum disulfide powder added is 13.3 mg, and the mass concentration is 0.5%, to obtain a sulfonated polyetheretherketone / polyaniline composite membrane S / PANI-(s-MoS 2 )-0.5.

[0045] Embodiment 3

[0046] The preparation method is the same as that of Example 1, except that in step S3, the amount of sulfonated molybdenum disulfide powder added is 26.7 mg, the mass concentration is 1%, and the sulfonated polyetheretherketone / polyaniline composite membrane S / PANI-(s-MoS 2 )-,1.

[0047] Comparative Example 1

[0048] The Nafion 212 membrane was purchased from DuPont, USA.

[0049] Comparative Example 2

[0050] S1. Weigh 10g of polyetheretherketone solid, dry it with air at 60°C for 24h, slowly pour the dried polyetheretherketone into a beaker containing 150mL of concentrated sulfuric acid, stir rapidly, stir at room temperature for 24h to ensure that the polyetheretherketone is completely dissolved in the concentrated sulfuric acid, heat it in a water bath at 50°C for 2h, slowly pour it into ice deionized water after the reaction, stir until it solidifies into a white filamentous solid, wash it with deionized water until the pH is neutral, and dry it with air at 60°C and 80°C for 12h, respectively, to obtain a sulfonated polyetheretherketone solid with a sulfonation degree of 69.8%;

[0051] S2. Take 2.59g of sulfonated polyetheretherketone and add it to 19.44mL of DMF. Stir until the sulfonated polyetheretherketone is completely dissolved to form a transparent casting film slurry. Evenly coat the transparent casting film slurry on a horizontally placed 18cm×18cm glass plate and let it stand at room temperature. When the DMF evaporates until the slurry no longer flows, dry it with air at 80℃ for 24h and vacuum dry it at 100℃ for 24h. After drying, peel off the film from the glass plate and place it in a 1mol / L H 2 SO 4 The membrane was soaked in the solution for 48 hours to fully protonate the membrane, and then rinsed with deionized water to remove excess acid on the surface, and then soaked in deionized water for 48 hours to remove residual sulfuric acid inside. Finally, the treated membrane was soaked in deionized water for standby use to obtain the sulfonated polyetheretherketone membrane SPEEK.

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

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

[0054] The prepared membrane was cut into rectangular sample strips of 1 cm × 5 cm, soaked in deionized water for 24 h, taken out and the moisture on the surface of the wet membrane was quickly wiped with dust-free paper, and the quality of the wet membrane (W wet , g) and length (L wet Subsequently, the film was dried in a forced air drying oven at 80°C for 24 h, and the quality of the dry film (W 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 by formula (1) and formula (2):

[0055]

[0056] Weigh a certain amount of dry film and soak it in 40 mL of 1 mol L -1 NaCl solution, stirred at room temperature for 48 h to ensure that all exchangeable hydrogen ions are replaced by sodium ions in the solution. Remove the membrane and rinse the membrane surface with deionized water so that the residual solution can also be detected. Use 0.01 mol L -1 The NaCl solution containing hydrogen ions is obtained by titrating with NaOH solution, and phenolphthalein solution is used as the titration endpoint indicator. The ion exchange capacity of the membrane is calculated by formula (3):

[0057]

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

[0059]

[0060] Wherein, L (cm) is the distance between the two electrodes of the fixture, that is, the length of the film actually tested; b (cm) is the width of the sample film, which is 1 cm in this paper; 10 7 It is the calculation coefficient when the data unit is the unit given in this article.

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

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

[0063]

[0064]

[0065] As can be seen from Table 1, the composite membranes of Examples 1 to 3 of the present invention have high water absorption, good hydrophilicity and low swelling rate, good mechanical properties and high ion exchange capacity, and a large number of exchangeable protons in the membrane, which are significantly improved compared to the Nafion212 provided in Comparative Example 1 and the sulfonated polyetheretherketone membrane provided in Comparative Example 2.

[0066] 2. The diaphragms of Example 2 and Comparative Examples 1-2 were used in full-flow batteries for battery charge and discharge tests.

[0067] The effect of the diaphragm on the performance of VRB batteries was evaluated using a battery testing system. The prepared diaphragm assembled battery was connected to a blue power testing system for battery rate charge and discharge cycle testing. The battery energy efficiency of the membranes prepared in Example 2 and Comparative Examples 1-2 at different current densities is shown in Table 2. The energy efficiency comparison is Figure 1 As shown; the battery capacity of the first cycle of the membranes prepared in Example 2 and Comparative Examples 1-2 at different current densities is shown in Table 3, and the battery capacity comparison is as follows Figure 2 shown.

[0068] It should be noted that during the battery test, in order to avoid hydrogen and oxygen evolution reactions caused by too low or too high voltage and corrosion of the graphite plate, the charge cut-off voltage was set to 1.65V and the discharge cut-off voltage was set to 0.8V. -2 At this time, the initial charge and discharge voltages of the assembled battery have reached the set values ​​of the cut-off voltage, 1.65V and 0.8V, so there is no data on battery capacity and battery efficiency.

[0069] Table 2 Cell energy efficiency of membrane at different current densities

[0070]

[0071]

[0072] Table 3 Cell capacity of the first cycle of the membrane at different current densities

[0073]

[0074] From the above results, it can be seen that the amino groups in polyaniline form a large number of hydrogen bond networks, and at the same time, s-MoS 2 The sulfonic acid groups in the composite membrane provide additional proton transfer sites, and the proton conductivity of the composite membrane is significantly improved. The voltage drop caused by the diaphragm resistance in the battery test is reduced. During the rate charge and discharge process, as the current density increases, the energy efficiency of the assembled battery in Example 2 is significantly higher than that in Comparative Examples 1 and 2. 2The permeation path of vanadium ions becomes complicated and tortuous, and the acid-base pair further hinders the permeation of vanadium ions. The assembled battery in Example 2 still has a high battery capacity at a higher current density, which is much higher than that of Comparative Examples 1 and 2.

[0075] The present invention provides a sulfonated polyetheretherketone / polyaniline composite membrane and a preparation method and application thereof, and obtains a composite membrane with excellent physical properties (water absorption rate, swelling rate) and high electrical conductivity. The prepared composite membrane is used in an all-vanadium liquid flow battery, and relatively excellent rate charge and discharge performance is obtained, the energy efficiency of the battery is improved, and a higher battery capacity is obtained, which solves the problem that the proton conductivity of the sulfonated polyetheretherketone membrane is difficult to break through when the vanadium ion permeability is low.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a sulfonated polyetheretherketone / polyaniline composite membrane, characterized in that: The following steps are involved: S1, mixing the dried polyetheretherketone with concentrated sulfuric acid, stirring evenly, heating in a water bath, pouring into ice deionized water after the reaction, stirring until solidified into a filamentous solid, washing with deionized water until the pH is neutral, and drying to obtain a sulfonated polyetheretherketone solid; S2, mixing molybdenum disulfide and toluene evenly, ultrasonicating, adding 1,3-propane sultone, stirring and heating in an oil bath, cooling to room temperature, centrifuging, discarding the supernatant, washing and soaking the precipitate with deionized water and anhydrous ethanol in turn, centrifuging twice, and drying to obtain sulfonated molybdenum disulfide powder; S3, mixing the sulfonated molybdenum disulfide powder, polyaniline and DMF solution obtained in S2, stirring, ultrasonicating, adding the sulfonated polyetheretherketone solid obtained in S1, stirring until completely dissolved, to obtain a casting slurry; S4. Apply the casting slurry obtained in S3 onto a glass plate, let it stand at room temperature until the slurry no longer flows, dry it into a film, and soak it in a 1 mol / L sulfuric acid solution and deionized water in turn to obtain a sulfonated polyetheretherketone / polyaniline composite membrane.

2. The preparation method according to claim 1, characterized in that: In S1, the water bath heating temperature is 50° C., and the water bath heating time is 2 h.

3. The preparation method according to claim 1, characterized in that: In S2, the ultrasonic power was 600 W and the ultrasonic time was 1 h.

4. The preparation method according to claim 1, characterized in that: In S2, the oil bath heating temperature is 110°C, and the oil bath heating time is 24h.

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

6. The preparation method according to claim 1, characterized in that: In S3, the mass ratio of polyaniline to sulfonated polyetheretherketone solid is 2:98; the mass ratio of the total mass of polyaniline and sulfonated polyetheretherketone solid to sulfonated molybdenum disulfide is 99-99.75:0.25-1.

7. The preparation method according to claim 1, characterized in that: In S3, the mass-volume ratio of sulfonated polyetheretherketone and DMF solution is 2.592 g:19.44 mL.

8. The preparation method according to claim 1, characterized in that: In S4, the specific process flow of the drying film formation is: forced air drying at 80° C. for 24 hours, and then vacuum drying at 100° C. for 24 hours.

9. The sulfonated polyetheretherketone / polyaniline composite membrane prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the sulfonated polyetheretherketone / polyaniline composite membrane according to claim 9 or the sulfonated polyetheretherketone / polyaniline composite membrane prepared by the preparation method according to any one of claims 1 to 8 in an all-vanadium redox flow battery.

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