Preparation method and application of PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified diaphragm

Abstract

The present invention relates to a preparation method and application of a PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified diaphragm. The PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified diaphragm obtained by the preparation method of the present invention has physical properties such as high mechanical strength and good wettability, and also improves the electrochemical properties such as the cycle performance and rate performance of lithium-sulfur batteries.

Description

Technical Field

[0001] The present invention belongs to the field of diaphragm materials, and in particular relates to a preparation method and application of a PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified diaphragm. Background Art

[0002] With the innovation of energy system, the rapid development of industries such as grid energy storage and new energy electric vehicles has promoted the demand of battery industry. Among different lithium batteries, lithium sulfur battery has a capacity of 1675mAh g -1 High theoretical specific capacity and 2600Wh kg -1 The high energy density of sulfur, its low environmental pollution and abundant reserves have also attracted a large number of scholars to study it, and it is considered to be one of the most promising systems in the next generation of renewable energy storage systems.

[0003] Recently, strategies based on the functionalization of commercial polyolefin separators have been developed, but they have struggled to effectively address safety issues such as thermal shrinkage caused by sudden internal battery temperature increases, breakdown caused by external impacts, and lithium dendrite growth. Battery separators made from high-performance organic fibers, including aramid nanofibers, polyphenylene sulfide (PPS) fibers, polyimide (PI) fibers, and paraphenylene benzobisoxazole (PBO) fibers, are being developed to meet the stringent requirements of future LSB technologies, such as protecting batteries from external impacts, sudden changes in ambient temperature, and unexpectedly high charge rates. However, due to the compact backbone structure of polymers like PBO and PPS and the lack of reactive side chains, the fibers exhibit overall inertness, resulting in unsatisfactory results in suppressing lithium dendrite growth. Summary of the Invention

[0004] In view of the defects of the prior art, the technical problem to be solved by the present invention is to provide a preparation method and application of a PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified diaphragm.

[0005] The present invention provides a method for preparing a fiber-modified diaphragm, comprising:

[0006] (1) nano-treating poly (2,5-dihydroxy-1,4-phenylene pyridinium diimidazole) (PIPD) fibers to obtain PIPD nanofibers; wherein the nano-treating comprises: adding the PIPD fibers to a mixed acid solution and stirring, adding a coagulation solution to form a gel, washing with acid, washing, and drying to obtain the PIPD nanofibers;

[0007] (2) preparing a mixed fiber dispersion containing high-temperature resistant organic functional nanofibers and PIPD nanofibers, stirring, and obtaining a coating slurry;

[0008] (3) The slurry is coated on the base membrane and then dried to obtain a fiber-modified membrane.

[0009] Preferably, the mixed acid solution in step (1) is a mixed acid solution of trifluoroacetic acid TFA and methanesulfonic acid MSA; wherein the volume ratio of trifluoroacetic acid TFA to methanesulfonic acid MSA is 1:1-23:2; and the mass volume ratio of the PIPD fiber to the mixed acid is 1-10 g:100-1000 mL.

[0010] Preferably, the coagulation liquid is one or more of ethanol, isopropanol and tert-butanol;

[0011] Preferably, the acid washing is performed by using a coagulation liquid to completely cover the surface of the diaphragm, and the acid washing time is ≥30 min;

[0012] Preferably, the washing is performed with deionized water; and the drying is performed under vacuum at a temperature of 50° C. to 70° C. for a time of ≥10 h.

[0013] Adding the coagulation liquid to form the gel in step (1) includes: evenly distributing the coagulation liquid on the surface of the fiber dispersion liquid.

[0014] Evenly spread the coagulation liquid on the surface of the fiber dispersion: spray the coagulation liquid on the surface of the fiber dispersion, wherein the spraying of the coagulation liquid is excessive, and wait until the color of the gel no longer changes.

[0015] In step (1), the coagulation liquid is evenly spread on the surface of the fiber dispersion liquid, and acid washing is performed: the coagulation liquid of the fiber dispersion liquid is evenly spread on the surface of the fiber dispersion liquid, the color of the fiber dispersion liquid changes, and gradually changes from a viscous liquid to a gel-like solid state, and the fiber-modified membrane is continuously immersed in the coagulation liquid to achieve the purpose of sufficient acid washing; the acid washing time is ≥30min.

[0016] Preferably, the PIPD fiber is pretreated in step (1); wherein the pretreatment comprises shearing the PIPD fiber, ultrasonically cleaning it in an organic solvent, then rinsing it with deionized water, and drying it to obtain the pretreated PIPD fiber; the length after shearing is ≤3 cm; wherein the organic solvent is acetone.

[0017] Furthermore, the length after shearing is 0.2 cm to 3 cm. Furthermore, the fiber is washed with deionized water at least three times, and each washing time is ≥ 15 minutes. The drying is performed by air drying (performed in an air drying oven) for more than 20 hours to completely remove moisture from the fiber.

[0018] Furthermore, the mass volume ratio of untreated or pretreated PIPD fiber to mixed acid is 1-10 g:100-1000 mL.

[0019] Preferably, the operating temperature of the high-temperature resistant organic functional nanofibers in step (2) is above 180°C.

[0020] Preferably, the high-temperature resistant organic functional nanofibers in step (2) include but are not limited to one or more of para-aramid PPTA fibers, polyphenylene sulfide PPS fibers, polyimide PI fibers, polyetheretherketone PEEK fibers, polytetrafluoroethylene PTFE fibers, and polyparaphenylene benzobisoxazole PBO fibers.

[0021] Preferably, in step (2), the mass ratio of high-temperature resistant organic functional nanofibers to PIPD nanofibers is 1:1-10:1; the stirring temperature is 22-26°C, and the time is 8h-144h. Furthermore, the stirring is magnetic stirring, and the stirring time is 8h-56h.

[0022] Preferably, in step (2), the high-temperature resistant organic functional nanofibers are pretreated, wherein the pretreatment comprises shearing the high-temperature resistant organic functional nanofibers, ultrasonically cleaning them in an organic solvent, rinsing them with deionized water, and drying them to obtain pretreated high-temperature resistant organic functional nanofibers; wherein the organic solvent is acetone; and the length after shearing is ≤3 cm. Furthermore, the length after shearing is 0.2 cm-3 cm. Furthermore, the number of deionized water washings is not less than 3 times, and each washing time is ≥15 minutes; and the drying is blast drying (performed in a blast drying oven), and the blast drying time is more than 20 hours to completely remove moisture from the fibers.

[0023] Furthermore, the mass ratio of the untreated or pretreated high-temperature resistant organic functional nanofibers to the untreated or pretreated PIPD nanofibers is 1:1-10:1.

[0024] The solvent of the mixed fiber dispersion in step (2) is one or more of anhydrous ethanol, isopropyl alcohol, acetone, etc. The dispersion solvent can be specifically selected according to actual conditions.

[0025] Preferably, the base membrane in step (3) includes at least one of a PP membrane, a PE membrane, and a HDPE membrane; the coating thickness is greater than 5 μm, and further, the coating thickness is 5 μm-60 μm.

[0026] The drying in step (3) is vacuum drying, the drying temperature is 50° C.-70° C., and the time is ≥10 h to completely remove the moisture in the diaphragm.

[0027] The present invention provides a fiber-modified diaphragm prepared by the method, wherein the fiber-modified diaphragm is a multifunctional lithium battery composite diaphragm.

[0028] The present invention provides an application of the fiber-modified diaphragm in lithium-sulfur batteries and lithium-ion batteries.

[0029] The present invention comprises the steps of selecting high-temperature-resistant organic functional nanofibers, pre-treating the fibers, preparing PIPD nanofibers, preparing a fiber dispersion, and then forming and post-treating the enhanced high-temperature-resistant organic functional nanofiber-modified membrane to produce a PIPD nanofiber-reinforced high-temperature-resistant organic functional nanofiber-modified membrane. This preparation method exhibits high mechanical strength and physical properties such as wettability, while also improving the electrochemical properties of lithium-sulfur batteries, such as cycling performance and rate capability.

[0030] Beneficial effects

[0031] The present invention provides a preparation method and application of a PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified diaphragm. The PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified battery diaphragm prepared by the preparation method has physical properties such as high mechanical strength and good wettability, and also improves the electrochemical properties of lithium-sulfur batteries such as cycle performance and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Electrochemical cycling performance tests were conducted on the PBO nanofiber modified membrane obtained in Comparative Example 1, the PIPD nanofiber modified membrane obtained in Comparative Example 2, and the PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified membranes prepared in Example 1 and Example 5;

[0033] Figure 2 The electrochemical rate performance test was performed on the PBO nanofiber modified membrane obtained in Comparative Example 1 and the PIPD nanofiber reinforced PBO nanofiber modified membrane prepared in Example 3;

[0034] Figure 3 Electrolyte contact angle tests were performed on the PBO nanofiber modified membrane (A) obtained in Comparative Example 1, the PIPD nanofiber modified membrane (B) obtained in Comparative Example 2, and the PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified battery separators prepared in Example 1 (C) and Example 4 (D);

[0035] Figure 4 The tensile strength test was performed on the PIPD nanofiber modified diaphragm obtained in Comparative Example 2 and the PP diaphragm obtained in Comparative Example 3. DETAILED DESCRIPTION

[0036] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0037] Comparative Example 1

[0038] 10g of PBO nanofibers were cut into 0.5cm-1cm short fibers and ultrasonically cleaned in 10ml of acetone. The cleaned fibers were removed and rinsed three times with deionized water for 15 minutes each time. They were then dried in a forced-air drying oven at 50°C for 20 hours to obtain dry PBO nanofibers. 5g of the pretreated PBO nanofibers were used to prepare 100g of a fiber dispersion slurry, which was then magnetically stirred at 25°C for 48 hours.

[0039] A PP separator was mounted on a smooth, clean glass plate. 25 g of the PBO nanofiber dispersion was evenly coated onto the PP separator using a 5 μm scraper. The coated separator was then dried in a vacuum oven at 60°C for 12 hours to remove moisture from the fiber-modified separator, thereby producing a nanoscale PBO fiber-modified separator.

[0040] Comparative Example 2

[0041] Take 10g of PIPD fiber and cut it into 0.5cm-1cm short fibers, add it into 10ml acetone solution for ultrasonic cleaning, take out the ultrasonically cleaned fiber and rinse it repeatedly with deionized water 3 times, each time for 15 minutes, then put it into a blast drying oven for 50℃ blast drying, and obtain dry PIPD short fibers after drying for 20 hours.

[0042] Take 50 ml of trifluoroacetic acid and methanesulfonic acid respectively and mix them evenly, take 5 g of pretreated PIPD short fibers and add them to the mixed acid solution, then stir magnetically at 25 ° C for 48 hours, and wait for the fiber nano-process. Use anhydrous ethanol as the coagulation liquid of the fiber dispersion, and use a spray bottle to continuously spray anhydrous ethanol (100 ml) to the surface of the fiber dispersion. The color of the fiber dispersion changes and gradually changes from a viscous liquid to a gel state. When the state of the fiber dispersion no longer changes, continue to soak the fiber gel in anhydrous ethanol for 30 minutes to achieve the purpose of fully washing the acid. The fiber gel after acid washing is repeatedly washed with deionized water 3 times, each time for 10 minutes. After washing, it is vacuum dried at 60 ° C in a vacuum drying oven for 12 hours to remove the moisture in the fiber gel, thereby obtaining PIPD nanofibers.

[0043] 5 g of pretreated PIPD nanofibers were used to prepare 100 g of fiber dispersion slurry, which was then magnetically stirred at 25° C. for 48 h.

[0044] A PP separator was mounted on a smooth, clean glass plate. 25 g of the PIPD nanofiber dispersion was evenly coated onto the PP separator using a 5 μm scraper. The coated separator was then vacuum-dried at 60°C for 12 hours to remove moisture from the fiber-modified separator, thereby producing a nanoscale PIPD fiber-modified separator.

[0045] Comparative Example 3

[0046] The PP membrane was added into 10 ml of acetone solution for ultrasonic cleaning. The ultrasonically cleaned membrane was taken out and rinsed repeatedly with deionized water for 3 times, each time for 15 minutes. It was then placed in a forced air drying oven and dried at 60°C for 12 hours to remove moisture from the membrane to obtain a PP membrane.

[0047] Example 1

[0048] Take 5g of PBO nanofiber and PIPD fiber respectively and cut them into 0.5cm-1cm short fibers, add them into 10ml acetone solution for ultrasonic cleaning, take out the ultrasonically cleaned fibers and rinse them repeatedly with deionized water 3 times, each time for 15 minutes, and then put them into a blast drying oven for 50℃ blast drying. After drying for 20h, dry PBO nanofiber and PIPD fiber are obtained.

[0049] Take 50 ml of trifluoroacetic acid and methanesulfonic acid respectively and mix them evenly, take 5 g of pretreated PIPD short fibers and add them to the mixed acid solution, then stir magnetically at 25 ° C for 48 hours, and wait for the fiber nano-process. Use anhydrous ethanol as the coagulation liquid of the fiber dispersion, and use a spray bottle to continuously spray anhydrous ethanol (100 ml) to the surface of the fiber dispersion. The color of the fiber dispersion changes and gradually changes from a viscous liquid to a gel state. When the state of the fiber dispersion no longer changes, continue to soak the fiber gel in anhydrous ethanol for 30 minutes to achieve the purpose of fully washing the acid. The fiber gel after acid washing is repeatedly washed with deionized water 3 times, each time for 10 minutes. After washing, it is vacuum dried at 60 ° C in a vacuum drying oven for 12 hours to remove the moisture in the fiber gel, thereby obtaining PIPD nanofibers.

[0050] 5 g of the pretreated PBO nanofibers and 5 g of the PIPD nanofibers were taken to prepare 100 g of a mixed fiber dispersion slurry, which was then magnetically stirred at 25° C. for 48 h.

[0051] A PP separator was mounted on a smooth, clean glass plate. 25 g of the mixed fiber dispersion was evenly coated on the PP separator using a 5 μm scraper. The coated separator was vacuum dried in a vacuum oven at 60°C for 12 hours to remove moisture from the fiber-modified separator, thereby producing a PIPD nanofiber-reinforced PBO nanofiber-modified separator.

[0052] Example 2

[0053] Take 5g of PPS nanofibers and PIPD fibers respectively and cut them into 0.5cm-1cm short fibers, add them into 10ml of acetone solution for ultrasonic cleaning, take out the ultrasonically cleaned fibers and rinse them repeatedly with deionized water 3 times, each time for 15 minutes, and then put them into a blast drying oven for 50℃ blast drying. After drying for 20h, dry PPS nanofibers and PIPD fibers are obtained.

[0054] Take 50 ml of trifluoroacetic acid and methanesulfonic acid respectively and mix them evenly, take 5 g of pretreated PIPD short fibers and add them to the mixed acid solution, then stir magnetically at 25 ° C for 48 hours, and wait for the fiber nano-process. Use anhydrous ethanol as the coagulation liquid of the fiber dispersion, and use a spray bottle to continuously spray anhydrous ethanol (100 ml) to the surface of the fiber dispersion. The color of the fiber dispersion changes and gradually changes from a viscous liquid to a gel state. When the state of the fiber dispersion no longer changes, continue to soak the fiber gel in anhydrous ethanol for 30 minutes to achieve the purpose of fully washing the acid. The fiber gel after acid washing is repeatedly washed with deionized water 3 times, each time for 10 minutes. After washing, it is vacuum dried at 60 ° C in a vacuum drying oven for 12 hours to remove the moisture in the fiber gel, thereby obtaining PIPD nanofibers.

[0055] 5 g of the pretreated PPS nanofibers and 5 g of the PIPD nanofibers were taken to prepare 100 g of a mixed fiber dispersion slurry, which was then magnetically stirred at 25° C. for 48 h.

[0056] A PP separator was fixed on a smooth, clean glass plate. 25 g of the mixed fiber dispersion was evenly coated on the PP separator using a 5 μm scraper. The coated separator was vacuum-dried in a vacuum drying oven at 60°C for 12 hours to remove moisture from the fiber-modified separator, thereby producing a PIPD nanofiber-reinforced PPS nanofiber-modified separator.

[0057] Example 3

[0058] Take 5g of PBO nanofiber and PIPD fiber respectively and cut them into 0.5cm-1cm short fibers, add them into 10ml acetone solution for ultrasonic cleaning, take out the ultrasonically cleaned fibers and rinse them repeatedly with deionized water 3 times, each time for 15 minutes, and then put them into a blast drying oven for 50℃ blast drying. After drying for 20h, dry PBO nanofiber and PIPD fiber are obtained.

[0059] Take 50 ml of trifluoroacetic acid and methanesulfonic acid respectively and mix them evenly, take 5 g of pretreated PIPD short fibers and add them to the mixed acid solution, then stir magnetically at 25 ° C for 48 hours, and wait for the fiber nano-process. Use anhydrous ethanol as the coagulation liquid of the fiber dispersion, and use a spray bottle to continuously spray anhydrous ethanol (100 ml) to the surface of the fiber dispersion. The color of the fiber dispersion changes and gradually changes from a viscous liquid to a gel state. When the state of the fiber dispersion no longer changes, continue to soak the fiber gel in anhydrous ethanol for 30 minutes to achieve the purpose of fully washing the acid. The fiber gel after acid washing is repeatedly washed with deionized water 3 times, each time for 10 minutes. After washing, it is vacuum dried at 60 ° C in a vacuum drying oven for 12 hours to remove the moisture in the fiber gel, thereby obtaining PIPD nanofibers.

[0060] 5 g of the pretreated PBO nanofibers and 5 g of the PIPD nanofibers were taken to prepare 100 g of a mixed fiber dispersion slurry, which was then magnetically stirred at 25° C. for 48 h.

[0061] A PE separator was fixed on a smooth, clean glass plate. 25 g of the mixed fiber dispersion was evenly coated on the PE separator using a 5 μm scraper. The coated separator was vacuum-dried in a vacuum drying oven at 60°C for 12 hours to remove moisture from the fiber-modified separator, thereby producing a PIPD nanofiber-reinforced PBO nanofiber-modified separator.

[0062] Example 4

[0063] Based on Example 1, a high-density polyethylene (HDPE) membrane was fixed to a smooth, clean glass plate. 25 g of the mixed fiber dispersion was evenly coated on the HDPE membrane using a 5 μm scraper. The coated membrane was vacuum-dried in a vacuum drying oven at 60°C for 12 hours to remove moisture from the fiber-modified membrane, thereby producing a PIPD nanofiber-reinforced PBO nanofiber-modified membrane.

[0064] Example 5

[0065] On the basis of Example 1, 7 g of pretreated PBO nanofibers and 3 g of PIPD nanofibers were taken to prepare 100 g of mixed fiber dispersion slurry, which was then magnetically stirred at 25°C for 48 h.

[0066] A PP separator was mounted on a smooth, clean glass plate. 25 g of the mixed fiber dispersion was evenly coated on the PP separator using a 5 μm scraper. The coated separator was vacuum dried in a vacuum oven at 60°C for 12 hours to remove moisture from the fiber-modified separator, thereby producing a PIPD nanofiber-reinforced PBO nanofiber-modified separator.

[0067] Example 6

[0068] The electrochemical cycle performance of the PBO nanofiber modified membrane obtained in Example 1, the PIPD nanofiber modified membrane obtained in Example 2, and the PIPD nanofiber reinforced high temperature resistant organic functional nanofiber modified membranes prepared in Example 1 and Example 5 were tested. The test results are as follows: Figure 1 As shown. The button-type battery was assembled in an argon-filled glove box, in which the contents of H2O and O2 were both below the level of 0.1ppm. The electrolyte consisted of DOL (1,3-dioxolane) and DME (1,2-dimethoxyethane) (1:1, volume ratio), dissolved with 1M LiTFSI and 0.1M LiNO3. The cycle test was to assemble the separator in a 2032-type standard button cell, and evaluate the cycle performance of the battery by constant current charge and discharge test on a Neware battery test system (TC5.1, China) in the potential range of 1.7 to 2.8V (compared to Li / Li+). The value of 0.2C is calculated based on the theoretical capacity of sulfur, which is 335mAg -1 .Depend on Figure 1 It can be seen that the cycle performance of different separators tested at a rate of 0.2C. After 50 cycles, the battery with the PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified separator prepared in Example 5 still retained 1099.92 mAh g -1 , which is better than the battery with PIPD nanofiber reinforced high temperature resistant organic functional nanofiber modified membrane prepared in Example 1 (930.48 mAh g -1 ), and its performance is better than the battery performance of the PBO nanofiber membrane prepared in Comparative Example 1 and the PIPD nanofiber membrane prepared in Comparative Example 2. The embodiment membrane not only has a high capacity retention rate, but also maintains a charge and discharge efficiency of more than 99%, indicating that the cycle performance of the lithium-sulfur battery can be improved.

[0069] Example 7

[0070] The electrochemical rate performance of the PBO nanofiber modified membrane obtained in Example 1 and the PIPD nanofiber reinforced PBO nanofiber modified membrane prepared in Example 3 were tested. The test results are as follows: Figure 2As shown. The button-type battery was assembled in an argon-filled glove box, where the contents of H2O and O2 were both below 0.1ppm. The electrolyte consisted of DOL (1,3-dioxolane) and DME (1,2-dimethoxyethane) (1:1, volume ratio), dissolved with 1M LiTFSI and 0.1M LiNO3. The cycle test was performed by assembling the separator in a 2032-type standard button cell and evaluating the rate performance of the battery by constant current charge and discharge test on a Neware battery test system (TC 5.1, China) in the potential range of 1.7 to 2.8V (compared to Li / Li+). The value of 1C is calculated based on the theoretical capacity of sulfur, which is 1675mAg -1 .Depend on Figure 2 It can be seen that the PIPD nanofiber reinforced PBO nanofiber modified diaphragm prepared in Example 3 exhibits the best rate performance, and exhibits 1607.06, 1183.54, 1073.39, 961.31, and 858.78 mAh g-1 at current densities of 0.2, 0.5, 1, 2, and 3 C, respectively. -1 .

[0071] Example 8

[0072] In this Example 8, the PBO nanofiber modified diaphragm obtained in Comparative Example 1 and the PIPD nanofiber modified diaphragm obtained in Comparative Example 2, and the PIPD nanofiber reinforced high temperature resistant organic functional nanofiber modified battery diaphragms prepared in Example 1 and Example 4 were tested for electrolyte contact angle. The test results are shown in FIG. Figure 3 As shown; Place the diaphragm on the platform and perform horizontal calibration to ensure the stability of the instrument. Use a micro-injector to drip an appropriate amount of battery electrolyte on the sample surface to form a uniform droplet. Use the camera of the OCA40Micro contact angle measurement instrument to capture the side image of the droplet. The image is taken 0.5 seconds after the electrolyte contacts the diaphragm. The specific values ​​of the contact angle test are shown in Table 1. Figure 3 As can be seen from Table 1, the wettability of the PIPD nanofiber reinforced high-temperature resistant organic functional nanofiber modified membrane to the electrolyte is greatly improved compared with the PBO nanofiber membrane. This is because the presence of polar groups (hydroxyl groups) of the PIPD nanofibers makes the polarity of PIPD better than that of PBO fibers, the fiber surface activity is enhanced, and the surface free energy is increased.

[0073] Table 1. Contact angle values ​​of different separators prepared in Comparative Examples 1 and 2 and Examples 1 and 4 to electrolyte.

[0074]

[0075] Example 9

[0076] The tensile strength test of the PIPD nanofiber modified diaphragm obtained in Example 2 and the PP diaphragm obtained in Example 3 was carried out. The test results are shown in FIG. Figure 4 As shown in the figure, cut the diaphragm into a uniform sample of 100mm in length and 10mm in width. Install the sample correctly on the testing machine, ensure that the clamp is firm and the axis of the sample is consistent with the tensile direction of the testing machine. Start the testing machine and stretch the sample at a speed of 50mm / min under the same conditions. During the test, record the force-displacement data. When the sample breaks, the testing machine will automatically stop. Figure 4 It can be obtained that the tensile strength of the PIPD nanofiber modified membrane is 90 MPa, which is much higher than the 19 MPa of the PP membrane, indicating that the PIPD nanofiber modified membrane can effectively increase the mechanical strength of the membrane.

Claims

1. A method for preparing a fiber-modified diaphragm, comprising: (1) Nano-processing poly (2,5-dihydroxy-1,4-phenylene pyridinium diimidazole) (PIPD) fibers to obtain PIPD nanofibers; The nano-fiberization treatment includes: adding PIPD fibers to a mixed acid solution and stirring, adding a coagulation solution to form a gel, washing with acid, washing, and drying to obtain PIPD nanofibers; The mixed acid solution is a mixed acid solution of trifluoroacetic acid TFA and methanesulfonic acid MSA; the coagulation liquid is one or more of ethanol, isopropanol and tert-butanol; the acid washing is to completely cover the surface of the diaphragm with the coagulation liquid; (2) preparing a mixed fiber dispersion containing high-temperature resistant organic functional nanofibers and PIPD nanofibers, stirring to obtain a slurry; the high-temperature resistant organic functional nanofibers include one or more of para-aramid PPTA fiber, polyphenylene sulfide PPS fiber, polyimide PI fiber, polyetheretherketone PEEK fiber, polytetrafluoroethylene PTFE fiber, and polyparaphenylene benzobisoxazole PBO fiber; (3) The slurry is coated on the base membrane and then dried to obtain a fiber-modified membrane.

2. The preparation method according to claim 1, characterized in that In the step (1), the volume ratio of trifluoroacetic acid TFA to methanesulfonic acid MSA is 1:1-23:2; the mass volume ratio of the PIPD fiber to the mixed acid is 1-10 g:100-1000 mL; The acid washing time is ≥30min; The washing is performed by washing with deionized water; the drying is performed by vacuum drying at a temperature of 50° C. to 70° C. for a time of ≥10 h.

3. The preparation method according to claim 1, characterized in that In step (1), the PIPD fibers are pretreated; the pretreatment includes shearing the PIPD fibers, ultrasonically cleaning them in an organic solvent, rinsing them with deionized water, and drying them; the length after shearing is ≤3 cm; and the organic solvent is acetone.

4. The preparation method according to claim 1, characterized in that The working temperature of the high-temperature resistant organic functional nanofibers in step (2) is above 180°C.

5. The preparation method according to claim 1, characterized in that: In step (2), the high-temperature resistant organic functional nanofibers are pretreated, wherein the pretreatment comprises shearing the high-temperature resistant organic functional nanofibers, ultrasonically cleaning them in an organic solvent, then rinsing them with deionized water, and drying them; the length after shearing is ≤3 cm; wherein the organic solvent is acetone.

6. The preparation method according to claim 1, characterized in that: In the step (2), the mass ratio of the high-temperature resistant organic functional nanofibers to the PIPD nanofibers is 1:1-10:1; the stirring temperature is 22-26° C., and the stirring time is 8 h-144 h.

7. The preparation method according to claim 1, characterized in that: In the step (3), the base diaphragm includes at least one of a PP diaphragm, a PE diaphragm, and a HDPE diaphragm; and the coating thickness is greater than 5 μm.

8. A fiber-modified diaphragm prepared by the method of claim 1.

9. Use of the fiber-modified diaphragm according to claim 8 in lithium-sulfur batteries and lithium-ion batteries.

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