A lithiophilic PCOF-PMIA composite nanofiber membrane, preparation method and application

Abstract

The present invention relates to the field of lithium battery technology, and in particular to a lithiophilic PCOF-PMIA composite nanofiber membrane, a preparation method, and an application thereof. The preparation method uses electrospinning technology and a room temperature in-situ growth process to obtain a lithiophilic PCOF-PMIA composite nanofiber membrane, greatly improving the mechanical strength of the fiber membrane; COF nanoparticles are prepared by a room temperature stirring synthesis process, which has the advantages of mild reaction conditions, simple operation, and short time consumption; the lithiophilic PCOF-PMIA composite nanofiber membrane has a uniform mesh nanofiber structure, which can effectively connect the COF particles on the fiber surface and inside at the same time, thereby maximizing the COF utilization. The present invention provides a composite nanofiber membrane that simultaneously introduces PMIA and PCOF, which helps to improve the ionic conductivity and lithium ion migration number of the solid electrolyte, and is expected to be applied to the preparation of solid composite electrolytes.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a lithiophilic PCOF-PMIA composite nanofiber membrane, a preparation method and applications thereof. Background Art

[0002] Lithium-ion batteries, a key technology in current energy storage, are evolving towards higher energy density, improved safety, and longer lifespans, driven by non-renewable energy consumption and environmental concerns. However, traditional liquid lithium-ion batteries still have limitations in terms of energy density, safety, and cycle life, such as electrolyte leakage and the limited specific capacity of graphite anodes.

[0003] To overcome these problems, researchers have proposed the concept of all-solid-state lithium metal batteries. This battery replaces the traditional liquid electrolyte with a solid electrolyte and uses lithium metal as the negative electrode material, with a high theoretical capacity (3860mAh g -1 ), low electrochemical potential (3.04V relative to the standard hydrogen electrode), and other advantages can significantly increase the energy density of the battery. In addition, the introduction of solid-state electrolytes effectively solves the safety risks of liquid electrolytes such as flammability and leakage, while also inhibiting the growth of lithium dendrites and improving the overall stability of the battery.

[0004] Currently, research and development of solid-state electrolytes focuses on two main categories: solid polymer electrolytes and solid inorganic electrolytes. Solid polymer electrolytes have been widely studied due to their advantages such as flexibility, light weight, easy processing, and good interfacial compatibility. However, their performance is limited by issues such as low room-temperature ionic conductivity and poor lithium salt dissociation. While solid inorganic electrolytes offer high ionic conductivity and excellent mechanical properties, they face challenges such as poor interfacial wettability, complex preparation, and instability in air, which require urgent attention.

[0005] Covalent organic frameworks (COFs), a novel material, show great potential in energy storage due to their high crystallinity, excellent thermal stability, tunable pore size, and ease of modification. The interlayer π-electron cloud and open pores of COFs provide diverse pathways for high-speed charge carrier ion transfer and are considered a promising future research direction for fast ion conductors. However, the current synthesis of COFs primarily relies on solvothermal methods, which are complex and time-consuming, limiting their large-scale application.

[0006] All-solid-state lithium metal batteries, by combining a high-energy-density lithium metal anode with a high-performance solid electrolyte, are expected to address many of the challenges of conventional lithium-ion batteries. However, achieving this goal requires breakthroughs in the solid electrolyte's interfacial stability, ion transport efficiency, and fabrication process. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the first object of the present invention is to provide a method for preparing a lithiophilic PCOF-PMIA composite nanofibrous membrane; the second object of the present invention is to provide a lithiophilic PCOF-PMIA composite nanofibrous membrane; and the third object of the present invention is to provide an application of the lithiophilic PCOF-PMIA composite nanofibrous membrane.

[0008] In order to achieve the first purpose, the technical solution adopted by the present invention is:

[0009] A method for preparing a lithiophilic PCOF-PMIA composite nanofiber membrane comprises the following steps:

[0010] S100, preparing a meta-aramid spinning precursor doped with tetraaminophenylporphyrin using an electrospinning technique, wherein the mass ratio of tetraaminophenylporphyrin to meta-aramid in the spinning precursor is 1:50 to 1:10;

[0011] S200, preparing solution A and solution B respectively, adding solution B to solution A, stirring for 23 to 25 hours, adding a terminator, and continuing stirring for 0.5 to 1.5 hours to obtain a fiber membrane;

[0012] The preparation process of solution A is as follows: tetraaminophenylporphyrin is dissolved in a mixed solution of acetonitrile and acetic acid, and after stirring evenly, the spinning precursor is added and stirred evenly to obtain solution A;

[0013] Solution B was prepared as follows: terephthalaldehyde was dissolved in acetonitrile to obtain terephthalaldehyde acetonitrile solution;

[0014] S300, washing the fiber membrane with acetonitrile and deionized water 2 to 4 times, respectively, at 25 to 35°C, and drying for 23 to 25 hours to obtain a lithiophilic PCOF-PMIA composite nanofiber membrane;

[0015] PCOF is the abbreviation of porphyrin-based covalent organic framework, and PMIA is the abbreviation of meta-aramid.

[0016] In the preparation method provided by the present invention, the porphyrin molecule centered on the central nitrogen atom (Lewis base) is modified with a tetraphenylamino group, which can undergo π-π interaction and metal-ligand coordination with the lithium salt to construct a stable ion channel; at the same time, the use of porphyrin-based covalent organic frameworks (COFs) can obtain the dual advantages of porphyrin and COFs structure, which has the dual functions of promoting lithium ion transfer and uniform lithium deposition.

[0017] The preparation method provided in this application can achieve rapid synthesis of nano-scale COFs particles at room temperature. At the same time, COFs as fillers are prone to agglomeration due to excess, resulting in the inability to exert the structural advantages of COFs. Combining COFs with nanofibers using electrospinning technology can effectively prevent the aggregation of COFs particles and increase the specific surface area of COFs. At the same time, it plays an important role in regulating the growth sequence of COFs.

[0018] In practical applications, it has been found that the COF particles within the nanofibers cannot be fully utilized due to the coating. Furthermore, due to the excessive size of some of the COF particles, the fiber surface develops a spindle or beaded structure, which degrades the fiber's mechanical properties. Existing free-standing COF nanofibers prepared using a sacrificial template method lose the support function of the flexible fibers and exhibit poor overall mechanical properties. Meta-aramid (PMIA) fibers possess excellent mechanical properties, chemical stability, and thermal stability. Using PMIA as a support substrate for COFs can provide enhanced mechanical strength. Furthermore, the hydrogen atoms in the amide bonds within meta-aramid can interact with the nitrogen atoms within the tetraaminophenylporphyrin molecules through protonation, anchoring the porphyrin-based COF to the fiber surface and interior. This ensures uniform COF anchoring and prevents detachment during use, significantly improving the utilization of porphyrin-based covalent organic framework (PCOF) nanoparticles.

[0019] Furthermore, S100 includes the following steps:

[0020] S110, dissolving tetraaminophenylporphyrin in N,N-dimethylacetamide, then adding meta-aramid stock solution, and continuously stirring for 11 to 13 hours to obtain a spinning solution;

[0021] S120, ejecting the spinning solution through a spinning needle at a speed of 0.5 to 1.5 ml / h to obtain a spinning precursor.

[0022] Furthermore, in step S110, the content of PMIA in the spinning solution is 11-13 wt%.

[0023] Furthermore, the terminator in step S200 is selected from benzaldehyde.

[0024] Furthermore, in step S200, the volume ratio of acetonitrile to acetic acid in the mixed solution is 7:1 to 5:1.

[0025] Furthermore, in step S200, the concentration of the phthalaldehyde acetonitrile solution is 0.188 mg / ml to 1.88 mg / ml.

[0026] In order to achieve the second purpose, the technical solution adopted by the present invention is:

[0027] A lithiophilic PCOF-PMIA composite nanofiber membrane is prepared using any of the above methods for preparing a lithiophilic PCOF-PMIA composite nanofiber membrane.

[0028] In order to achieve the third purpose, the technical solution adopted by the present invention is:

[0029] An application of a lithiophilic PCOF-PMIA composite nanofiber membrane, using any of the above lithiophilic PCOF-PMIA composite nanofiber membranes to prepare a solid composite electrolyte;

[0030] The solid composite electrolyte comprises a PCOF-PMIA composite nanofiber membrane, polyethylene oxide and lithium bis(trifluoromethanesulfonylimide), and the polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) are coated on the surface of the PCOF-PMIA composite nanofiber membrane.

[0031] The molar ratio of the ethylene oxide groups in the polyethylene oxide to the lithium ions in the lithium bis(trifluoromethanesulfonyl)imide is 18:1 to 10:1.

[0032] Furthermore, preparing the solid composite electrolyte comprises the following steps:

[0033] S410, adding dried polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) into an organic solvent and dissolving them to obtain an organic solution of polyethylene oxide and lithium bis(trifluoromethanesulfonylimide);

[0034] S420, applying the organic solution to both sides of the PCOF-PMIA composite nanofiber membrane by scraping, drying at 45-55° C. for 23-25 hours, removing the organic solvent, and obtaining the solid composite electrolyte by hot pressing.

[0035] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0036] The present invention provides a method for preparing a lithiophilic PCOF-PMIA composite nanofiber membrane. Using electrospinning technology and a room-temperature in-situ growth process, the resulting membrane utilizes PMIA as a substrate, significantly improving the membrane's mechanical strength compared to existing free-standing COF fiber membranes. This method not only anchors COF nanoparticles on the fiber surface and within the membrane, but also utilizes tetraaminophenylporphyrin (TAPP), a building block of the COF nanoparticles, to facilitate protonation interactions between the amide bond in the meta-aramid and the nitrogen atoms within the TAPP ring. This provides chemical support for the anchoring of the in-situ grown PCOF nanoparticles.

[0037] The present invention provides a method for preparing a lithiophilic PCOF-PMIA composite nanofiber membrane. By selecting a meta-aramid spinning solution and mixing a soluble building monomer to prepare an electrospinning solution, a uniform mesh nanofiber network structure without beads or spindles can be prepared. The mesh structure can effectively connect the COFs particles on the fiber surface and inside at the same time, thereby maximizing the utilization of COFs.

[0038] The present invention provides a method for preparing a lithiophilic PCOF-PMIA composite nanofiber membrane, which prepares COF nanoparticles through a room temperature stirring synthesis process, and has the advantages of mild reaction conditions, simple operation, and short time consumption.

[0039] The lithiophilic PCOF-PMIA composite nanofiber membrane provided by the present invention uses electrospun nanofibers as a carrier, improving the dispersibility of COF particles. This not only prevents aggregation of COF particles but also increases the contact surface area between the COF and reactants. Furthermore, the designed COF nanoparticles exhibit excellent lithiophilicity and electron-rich properties, which contribute to enhanced lithium ion transport capacity.

[0040] The lithiophilic PCOF-PMIA composite nanofiber membrane provided by the present invention uses meta-aramid nanofibers with excellent mechanical properties as a non-sacrificial template, which can effectively improve the mechanical strength of the composite fiber.

[0041] The lithiophilic PCOF-PMIA composite nanofiber membrane provided by the present invention simultaneously introduces PMIA and PCOF, which can simultaneously achieve the dissociation of lithium salts and the weakening of the coordination effect between lithium ions and polyethylene oxide (PEO) ether oxygen bonds. This dual effect helps to improve the ionic conductivity and lithium ion transference number of the solid electrolyte, thereby effectively improving the ion transport capacity in the solid composite electrolyte. Therefore, it is expected to be used in the preparation of solid composite electrolytes.

[0042] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is an SEM image of the spinning precursor provided in Example 1 of the present invention.

[0044] Figure 2 This is a SEM image of the lithiophilic PCOF-PMIA composite nanofiber membrane provided in Example 1 of the present invention.

[0045] Figure 3 This is an SEM image of the spinning precursor provided in Example 2 of the present invention.

[0046] Figure 4 This is a SEM image of the lithiophilic PCOF-PMIA composite nanofiber membrane provided in Example 2 of the present invention.

[0047] Figure 5 This is an SEM image of the spinning precursor provided in Example 3 of the present invention.

[0048] Figure 6 This is a SEM image of the lithiophilic PCOF-PMIA composite nanofiber membrane provided in Example 3 of the present invention.

[0049] Figure 7 This is an SEM image of the spinning precursor provided in Example 4 of the present invention.

[0050] Figure 8 This is a SEM image of the lithiophilic PCOF-PMIA composite nanofiber membrane provided in Example 4 of the present invention.

[0051] Figure 9 This is an SEM image of the spinning precursor provided in Example 5 of the present invention.

[0052] Figure 10 This is a SEM image of the lithiophilic PCOF-PMIA composite nanofiber membrane provided in Example 5 of the present invention.

[0053] Figure 11 This is an SEM image of the spinning precursor provided in Comparative Example 1 of the present invention.

[0054] Figure 12 This is an SEM image of the PCOF-PMIA composite nanofiber membrane provided in Comparative Example 1 of the present invention.

[0055] Figure 13 1 is a Fourier transform infrared spectrum of the PCOF-PMIA composite nanofiber membrane provided in Example 1 of the present invention, and the nano PCOF particles and PMIA provided in Comparative Example 1.

[0056] Figure 14 This is a graph showing the relationship between the ionic conductivity of different material systems provided in the embodiments and comparative examples of the present invention and the change in temperature.

[0057] Figure 15 Schematic diagram of the electrochemical window of the solid composite electrolyte provided in Example 2 of the present invention and the PEO control group at 50°C.

[0058] Figure 16 This is a graph showing the cycle performance of a LiFePO4 / / li battery using a solid composite electrolyte provided in Example 2 of the present invention at 50°C and 0.5C. DETAILED DESCRIPTION

[0059] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0060] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used are all commercially available unless otherwise specified.

[0061] Example 1

[0062] 1. Preparation of TAPP-doped PMIA spinning precursor using electrospinning technology. The process is as follows:

[0063] TAPP (20 mg) was dissolved in N,N-dimethylacetamide (DMAC) (3.33 g) and stirred continuously until the solution had a uniform color. Then, PMIA stock solution (5 g, solid content 20 wt%) was added to the above solution and stirred continuously for 12 h to obtain a uniform spinning solution (PMIA content of 12 wt%). Then, the above spinning solution was ejected through an 18G spinning needle at a rate of 1 ml / h. During the electrospinning process, a voltage of 25 kV was applied, the receiving roller speed was 65 rpm, and the distance between the needle tip and the receiving roller was set to 15 cm. The PMIA spinning precursor was collected and then placed in a vacuum oven at 50 ° C for 12 h to remove the residual solvent to obtain a TAPP-doped PMIA spinning precursor. The mass ratio of TAPP to PMIA in the spinning precursor was 1:50. The electron microscope image of the spinning precursor is shown as follows. Figure 1As shown;

[0064] The electron microscope shooting parameters are as follows: accelerating voltage 10.0 kV; working distance 12.4 mm, magnification 20000;

[0065] 2. In situ growth of PCOF-PMIA composite nanofiber membrane at room temperature. The process is as follows:

[0066] Prepare Solution A: Dissolve TAPP (21.1 mg) in a mixture of 7.5 ml acetonitrile (ACN) and 1 ml acetic acid, stirring continuously for 30 min. Then, add the previously prepared spinning precursor (132.6 mg, including 2.6 mg TAPP) and stir evenly to obtain Solution A.

[0067] Among them, the total amount of TAPP in solution A is 23.7 mg;

[0068] Prepare solution B: dissolve terephthalaldehyde (TPA) (9.4 mg, 0.07 mmol) in ACN (5 ml) and stir until the solution becomes clear.

[0069] Solution B was added to solution A and stirred at 1100 rpm for 24 h. Benzaldehyde (1 μl) was then added and stirred for another 1 h to obtain a PCOF-PMIA composite nanofiber membrane. The membrane was taken out and washed three times with acetonitrile and deionized water, respectively. After drying at 30 °C for 24 h, a lithiophilic PCOF-PMIA composite nanofiber membrane was obtained. The electron microscope image of the PCOF-PMIA composite nanofiber membrane is shown in FIG. Figure 2 As shown;

[0070] The electron microscope shooting parameters are as follows: accelerating voltage 10.0 kV; working distance 12.7 mm, magnification 40000;

[0071] 3. Preparation of PCOF-PMIA / PEO / LiTFSI solid composite electrolyte by combining solution doctor blade coating and hot pressing process. The process is as follows:

[0072] The molecular weight of the dried 5 g·mol -1 Polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LITFSI) (purity 99.99%) were added to anhydrous acetonitrile (99.80%) and dissolved to obtain an acetonitrile solution of PEO and LITFSI;

[0073] The molar ratio of the ethylene oxide groups in the added PEO to the lithium ions in the added LITFSI is 15:1;

[0074] The acetonitrile solution of PEO and LITFSI was coated on the surface of the PCOF-PMIA composite nanofiber membrane using a glass rod (not limited to a glass rod), and dried at 50°C for 24 hours to remove the solvent;

[0075] Finally, a solid composite electrolyte with a thickness of about 50 μm was obtained by hot pressing.

[0076] The prepared solid composite electrolyte was placed in an argon-filled glove box for further drying (≥36 h) to obtain the PCOF-PMIA / PEO / LiTFSI solid composite electrolyte.

[0077] Example 2

[0078] The difference between this embodiment and embodiment 1 is that:

[0079] 1. In the process of preparing TAPP-doped PMIA spinning precursor using electrospinning technology: the amount of TAPP added is 40 mg; during the electrospinning process, the applied voltage is 30 kV, the distance between the needle tip and the receiving roller is set to 18 cm, the mass ratio of TAPP to PMIA in the spinning precursor is 1:25, and the electron microscope image of the spinning precursor is as follows: Figure 3 As shown;

[0080] The electron microscope shooting parameters are as follows: acceleration voltage is 10.0 kV; working distance is 13.0 mm, magnification is 20000;

[0081] 2. In the process of in-situ growth preparation of PCOF-PMIA composite nanofiber membrane at room temperature: when preparing solution A, the amount of TAPP added was 18.96 mg, and the amount of PMIA spinning precursor added was 123.24 mg. The electron microscope image of PCOF-PMIA composite nanofiber membrane is as follows: Figure 4 As shown;

[0082] The electron microscope shooting parameters are as follows: accelerating voltage 10.0 kV; working distance 12.7 mm, magnification 40000;

[0083] 3. Preparation of PCOF-PMIA / PEO / LiTFSI solid composite electrolyte by combining solution coating and hot pressing process:

[0084] The molar ratio of the ethylene oxide groups in the added PEO to the lithium ions in the added LITFSI is 10:1.

[0085] The rest of the process is the same as in Example 1.

[0086] Example 3

[0087] The difference between this embodiment and embodiment 1 is that:

[0088] 1. In the process of preparing TAPP-doped PMIA spinning precursor using electrospinning technology: the amount of TAPP added is 60 mg; during the electrospinning process, the applied voltage is 30 kV, the distance between the needle tip and the receiving roller is set to 17 cm, the mass ratio of TAPP to PMIA in the spinning precursor is 3:50, and the electron microscope image of the spinning precursor is as follows: Figure 5 As shown;

[0089] The electron microscope shooting parameters are as follows: accelerating voltage 10.0 kV; working distance 12.7 mm, magnification 40000;

[0090] 2. In the process of in-situ growth preparation of PCOF-PMIA composite nanofiber membrane at room temperature: when preparing solution A, the amount of TAPP added was 21.33 mg, and the amount of PMIA spinning precursor added was 46.5 mg. The electron microscope image of PCOF-PMIA composite nanofiber membrane is as follows: Figure 6 As shown;

[0091] The electron microscope shooting parameters are as follows: acceleration voltage is 10.0 kV; working distance is 12.8 mm, magnification is 40000K;

[0092] 3. Preparation of PCOF-PMIA / PEO / LiTFSI solid composite electrolyte by combining solution coating and hot pressing process:

[0093] The molar ratio of ethylene oxide groups in the added PEO to lithium ions in the added LITFSI is 12:1.

[0094] The rest of the process is the same as in Example 1.

[0095] Example 4

[0096] The difference between this embodiment and embodiment 1 is that:

[0097] 1. In the process of preparing TAPP-doped PMIA spinning precursor using electrospinning technology: the amount of TAPP added is 80 mg, the mass ratio of TAPP to PMIA in the spinning precursor is 2:25, and the electron microscope image of the spinning precursor is as follows: Figure 7 As shown;

[0098] The electron microscope shooting parameters are as follows: accelerating voltage 10.0 kV; working distance 12.7 mm, magnification 40000;

[0099] 2. In the process of in-situ growth preparation of PCOF-PMIA composite nanofiber membrane at room temperature: when preparing solution A, the amount of spinning precursor added was 35.1 mg. The electron microscope image of PCOF-PMIA composite nanofiber membrane is as follows: Figure 8 As shown;

[0100] The electron microscope shooting parameters are as follows: acceleration voltage is 10.0 kV; working distance is 12.8 mm, magnification is 40000;

[0101] 3. Preparation of PCOF-PMIA / PEO / LiTFSI solid composite electrolyte by combining solution coating and hot pressing process:

[0102] The molar ratio of ethylene oxide groups in the added PEO to lithium ions in the added LITFSI is 18:1.

[0103] The rest of the process is the same as in Example 1.

[0104] Example 5

[0105] The difference between this embodiment and embodiment 1 is that:

[0106] 1. In the process of preparing TAPP-doped PMIA spinning precursor using electrospinning technology: the amount of TAPP added is 100 mg, the mass ratio of TAPP to PMIA in the spinning precursor is 1:10, and the electron microscope image of the spinning precursor is as follows: Figure 9 As shown;

[0107] The electron microscope shooting parameters are as follows: acceleration voltage is 10.0 kV; working distance is 12.8 mm, magnification is 40000;

[0108] 2. In the process of in-situ growth preparation of PCOF-PMIA composite nanofiber membrane at room temperature: when preparing solution A, the amount of spinning precursor added was 28.6 mg. The electron microscope image of PCOF-PMIA composite nanofiber membrane is as follows: Figure 10 As shown;

[0109] The electron microscope shooting parameters are as follows: accelerating voltage 10.0 kV; working distance 12.7 mm, magnification 40000;

[0110] 3. Preparation of PCOF-PMIA / PEO / LiTFSI solid composite electrolyte by combining solution coating and hot pressing process:

[0111] The molar ratio of ethylene oxide groups in the added PEO to lithium ions in the added LITFSI is 18:1.

[0112] The rest of the process is the same as in Example 1.

[0113] Comparative Example 1

[0114] 1. Preparation of PMIA spinning precursor without TAPP using electrospinning technology. The process is as follows:

[0115] Meta-aramid stock solution (PMIA, solid content 20%) was added to N,N-dimethylacetamide (DMAC) (3.33 g) and stirred continuously for 12 h to obtain a uniform spinning solution (PMIA content was 12%). Then, the spinning solution was ejected through an 18G spinning needle at a rate of 1 ml / h. During the electrospinning process, a voltage of 25 kV was applied, the receiving roller speed was 65 rpm, and the distance between the needle tip and the receiving roller was set to 15 cm. The PMIA spinning precursor was collected and then placed in a vacuum oven at 50°C for 12 h to remove residual solvent, thereby obtaining a PMIA spinning precursor undoped with TAPP. The electron microscope image of the spinning precursor is shown as follows. Figure 11 As shown;

[0116] The electron microscope shooting parameters are as follows: acceleration voltage is 10.0 kV; working distance is 12.8 mm, magnification is 40000;

[0117] Second, the preparation of nano-PCOF particles under room temperature conditions is as follows:

[0118] Prepare Solution A: Dissolve TAPP (23.7 mg, 0.035 mmol) in 7.5 mL of acetonitrile (ACN) and 1 mL of acetic acid and stir for 30 min to obtain Solution A.

[0119] Prepare solution B: dissolve terephthalaldehyde (TPA) (9.4 mg, 0.07 mmol) in ACN (5 ml) and stir until the solution becomes clear.

[0120] Solution B was added to solution A, and the mixture was stirred at 1100 rpm for 24 h. Benzaldehyde (1 μl) was then added, and the mixture was stirred for another 1 h. The mixture was centrifuged to obtain a precipitate, which was washed three times with acetonitrile and deionized water, respectively, and dried at 30°C for 24 h to obtain nanoporphyrin-based (PCOF) particles.

[0121] 3. In situ growth preparation of PCOF-PMIA composite nanofiber membrane under room temperature conditions, the process is as follows:

[0122] TAPP (23.7 mg, 0.035 mmol) was dissolved in a mixed solution consisting of 7.5 ml of acetonitrile (ACN) and 1 ml of acetic acid. After stirring for 30 min, the spinning precursor (68.47 mg) was added and stirred evenly to obtain solution A.

[0123] TPA (9.4 mg, 0.07 mmol) was dissolved in ACN (5 ml) and stirred continuously until the solution became clear. The solution was then added to solution A and stirred at 1100 rpm for 24 h. Benzaldehyde (1 μl) was then added and stirred for 1 h to obtain a PCOF-PMIA composite nanofiber membrane. The membrane was taken out and washed three times with acetonitrile and deionized water, respectively, and dried at 30 °C for 24 h to obtain a PCOF-PMIA composite nanofiber membrane. The electron micrograph of the PCOF-PMIA composite nanofiber membrane is shown in FIG. Figure 12 As shown;

[0124] The electron microscope shooting parameters are as follows: accelerating voltage 10.0 kV; working distance 12.7 mm, magnification 40000;

[0125] 3. Preparation of PCOF-PMIA / PEO / LiTFSI solid composite electrolyte by combining solution doctor blade coating and hot pressing process. The process is as follows:

[0126] The molecular weight of the dried 5 g·mol -1 Polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LITFSI) (purity 99.99%) were added to anhydrous acetonitrile (99.80%) and dissolved to obtain an acetonitrile solution of PEO and LITFSI;

[0127] The molar ratio of the ethylene oxide groups in the added PEO to the lithium ions in the added LITFSI is 15:1;

[0128] The acetonitrile solution of PEO and LITFSI is coated on the surface of the lithiophilic PCOF-PMIA composite nanofiber membrane using a glass rod (not limited to a glass rod). After drying at 50°C for 24 hours to remove the solvent, a solid composite electrolyte with a thickness of approximately 50 μm is obtained by hot pressing.

[0129] The prepared solid composite electrolyte was placed in an argon-filled glove box for further drying (≥36 h) to obtain the PCOF-PMIA / PEO / LiTFSI solid composite electrolyte.

[0130] like Figure 13 As shown, the Fourier transform infrared spectra of the PCOF-PMIA composite nanofiber membrane provided in Example 1, the nano PCOF particles and PMIA provided in Comparative Example 1 show that PCOF grows on the surface of PMIA fibers and does not completely cover the fiber surface.

[0131] The test results of the mechanical properties of the lithiophilic PCOF-PMIA composite nanofiber membrane and PMIA nanofiber provided in Example 2 are shown in Table 1:

[0132] Table 1 Mechanical properties test results of different materials

[0133]

[0134] As can be seen from Table 1, the lithiophilic PCOF-PMIA composite nanofiber membrane provided by the present invention has excellent mechanical strength, with a tensile strength of 22.29 MPa and an elongation at break of 36.71%.

[0135] The ionic conductivity of the PCOF-PMIA / PEO / LiTFSI solid composite electrolyte, pure polyethylene oxide (PEO) electrolyte and PEO / PMIA nanofiber composite electrolyte provided in Examples 1 to 5 was tested. The results are as follows: Figure 14 As shown in the figure, the ionic conductivity of the electrolyte increases with the increase of temperature. Compared with the ionic conductivity of pure PEO electrolyte, the ionic conductivity of the PCOF-PMIA / PEO / LiTFSI solid composite electrolyte is improved, reaching 7.09677×10 -4 S cm -1 The results show that the charge aggregation effect inside PCOF can promote the dissociation of lithium salts and the rapid migration of lithium ions. The porphyrin monomers in PCOF can also coordinate with lithium ions, further promoting the dissociation of lithium salts. At the same time, the three-dimensional interconnected network structure constructed by PCOF pores and PMIA nanofibers also provides a more continuous and low-migration barrier lithium ion rapid transport channel within the electrolyte.

[0136] like Figure 15 As shown, this is a schematic diagram of the electrochemical window of the composite electrolyte and pure PEO electrolyte provided in Example 2 of the present application at 50°C. It can be seen from the figure that with the increase of voltage, the current of both materials gradually increases, but after the voltage exceeds 5V, the current of the PEO / PCOF-PMIA / LiTFSI composite solid electrolyte is significantly higher than that of the pure PEO electrolyte, showing better electrochemical performance. Therefore, it has the conditions to match high-voltage cathode materials.

[0137] like Figure 16 As shown, this is a LiFePO4 / / Li battery cycle performance diagram of the PEO / PCOF-PMIA / LiTFSI composite solid electrolyte provided in Example 2 of the present application under conditions of 50°C and 0.5C. It can be seen from the figure that the battery can be stably cycled for more than 450 cycles, which indicates that the composite solid electrolyte exhibits excellent long-cycle performance in all-solid-state lithium metal batteries.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a lithiophilic PCOF-PMIA composite nanofiber membrane, characterized in that: The steps include: S100, preparing a meta-aramid spinning precursor doped with tetraaminophenylporphyrin using an electrospinning technique, wherein the mass ratio of tetraaminophenylporphyrin to meta-aramid in the spinning precursor is 1:50 to 1:10; S200, preparing solution A and solution B respectively, adding solution B to solution A, stirring for 23 to 25 hours, adding a terminator, and continuing stirring for 0.5 to 1.5 hours to obtain a fiber membrane; The preparation process of solution A is as follows: tetraaminophenylporphyrin is dissolved in a mixed solution of acetonitrile and acetic acid, and after stirring evenly, the spinning precursor is added and stirred evenly to obtain solution A; Solution B was prepared as follows: terephthalaldehyde was dissolved in acetonitrile to obtain terephthalaldehyde acetonitrile solution; S300, washing the fiber membrane with acetonitrile and deionized water 2 to 4 times, respectively, at 25 to 35°C, and drying for 23 to 25 hours to obtain a lithiophilic PCOF-PMIA composite nanofiber membrane; PCOF is the abbreviation of porphyrin-based covalent organic framework, and PMIA is the abbreviation of meta-aramid.

2. The method for preparing the lithiophilic PCOF-PMIA composite nanofiber membrane according to claim 1, wherein: S100 includes the following steps: S110, dissolving tetraaminophenylporphyrin in N,N-dimethylacetamide, then adding meta-aramid stock solution, and continuously stirring for 11 to 13 hours to obtain a spinning solution; S120, ejecting the spinning solution through a spinning needle at a speed of 0.5 to 1.5 ml / h to obtain a spinning precursor.

3. The method for preparing the lithiophilic PCOF-PMIA composite nanofiber membrane according to claim 2, wherein: In step S110, the content of PMIA in the spinning solution is 11-13 wt%.

4. The method for preparing the lithiophilic PCOF-PMIA composite nanofiber membrane according to claim 1, wherein: The terminator in step S200 is selected from benzaldehyde.

5. The method for preparing the lithiophilic PCOF-PMIA composite nanofiber membrane according to claim 1, wherein: In step S200, the volume ratio of acetonitrile to acetic acid in the mixed solution is 7:1 to 5:

1.

6. The method for preparing the lithiophilic PCOF-PMIA composite nanofiber membrane according to claim 1, wherein: In step S200 , the concentration of the terephthalaldehyde-acetonitrile solution is 0.188 mg / ml to 1.88 mg / ml.

7. A lithiophilic PCOF-PMIA composite nanofiber membrane, characterized in that: The nanofiber membrane is prepared by the method for preparing the lithiophilic PCOF-PMIA composite nanofiber membrane according to any one of claims 1 to 6.

8. An application of a lithiophilic PCOF-PMIA composite nanofiber membrane, characterized in that: A solid composite electrolyte is prepared using the lithiophilic PCOF-PMIA composite nanofiber membrane according to claim 7; The solid composite electrolyte comprises a PCOF-PMIA composite nanofiber membrane, polyethylene oxide and lithium bis(trifluoromethanesulfonylimide), and the polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) are coated on the surface of the PCOF-PMIA composite nanofiber membrane. The molar ratio of the ethylene oxide groups in the polyethylene oxide to the lithium ions in the lithium bis(trifluoromethanesulfonyl)imide is 18:1 to 10:

1.

9. The use of the lithiophilic PCOF-PMIA composite nanofiber membrane according to claim 8, characterized in that: The preparation of the solid composite electrolyte comprises the following steps: S410, adding dried polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) into an organic solvent and dissolving them to obtain an organic solution of polyethylene oxide and lithium bis(trifluoromethanesulfonylimide); S420, applying the organic solution to both sides of the PCOF-PMIA composite nanofiber membrane by scraping, drying at 45-55° C. for 23-25 hours, removing the organic solvent, and obtaining the solid composite electrolyte by hot pressing.

10. The use of the lithiophilic PCOF-PMIA composite nanofiber membrane according to claim 9, characterized in that: The organic solvent is selected from acetonitrile.

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