Hydroxylated cof flexible quasi-solid-state lithium battery separator and lithium battery preparation method

Abstract

The application discloses a hydroxylated COF quasi-solid flexible polymer diaphragm and a lithium battery preparation method. First, a covalent organic material COF with amino and hydroxyl functional groups is synthesized by a freeze-drying method, then the covalent organic material COF is blended with polyethylene oxide PEO and a lithium salt to obtain an orange viscous liquid. The orange viscous liquid with hydroxyl and amino functional groups is poured into a polytetrafluoroethylene mold to obtain a hydroxylated flexible solid polymer film by a template method. The hydroxylated flexible solid polymer film is cut into a 19mm disc, and the disc is assembled with a lithium iron phosphate positive electrode and a lithium sheet negative electrode to obtain a hydroxylated COF quasi-solid flexible polymer lithium ion battery with high lithium ion migration rate and high Young's modulus. The battery has a capacity of 153mAh g ‑1 at a rated capacity of 0.2C, a coulombic efficiency of 95%, and a lithium ion migration rate of 0.786.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery separator, and also to a method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery. Background Technology

[0002] With the ever-increasing energy demands of electric vehicles and mobile devices, it is essential to develop next-generation rechargeable lithium-ion batteries (LIBs) that offer higher energy density and greater power output. Rechargeable lithium-ion batteries play a crucial role in electrochemical energy storage systems, bringing numerous benefits to portable energy applications and other sectors. However, lithium-ion batteries suffer from drawbacks such as a limited electrochemical window, susceptibility to short circuits, flammability, and explosiveness, posing significant safety risks. Furthermore, lithium metal batteries experience the formation of numerous lithium dendrites on the negative electrode surface during long-term charge-discharge cycles. The formation of these dendrites can lead to short circuits and even thermal runaway, hindering the commercialization of lithium metal batteries (LMBs). Solid-state lithium-ion batteries (SSLIBs), due to their higher energy density and better safety characteristics compared to lithium-ion batteries (LIBs), are currently considered the optimal alternative to lithium metal batteries.

[0003] To address the safety concerns of liquid lithium metal batteries, researchers have investigated a series of solid-state electrolyte (SSE) and quasi-solid-state electrolyte (SSE) membranes to replace traditional liquid lithium metal batteries. Solid-state electrolytes (SSEs) can be categorized into pure solid-state electrolytes and quasi-solid-state electrolytes. Pure solid-state electrolytes typically employ garnet-type (LLZO), sulfide, and NASICON-type solid-state electrolytes, possessing characteristics such as non-flammability, high Young's modulus, and a large electrochemical window. However, during charge and discharge, lithium dendrites form on the negative electrode surface of pure solid-state electrolytes, growing along the grain boundaries of inorganic particles, leading to battery failure. Furthermore, the brittleness of pure solid-state electrolyte membranes makes their fabrication difficult and increases the interfacial resistance between the negative electrode and the electrolyte, which is a major factor limiting the commercialization of pure solid-state electrolytes. Conversely, quasi-solid-state polymer electrolyte membranes combine the characteristics of both pure solid-state polymer electrolyte membranes and traditional liquid electrolytes, featuring ease of synthesis, close contact between the electrolyte and the negative electrode, and generally compatibility with large-scale manufacturing processes. Polyelectrolyte (PEO) is one of the most commonly used polymer materials in quasi-solid-state polymer electrolytes. However, because the crystallinity of polyethylene oxide is generally below 60°C, and its crystallinity is very high at room temperature, its ionic conductivity is typically around 10. -8 ~10 -7 cm -2 This approach fails to meet commercial requirements. Therefore, reducing the crystallinity of the ethylene oxide monomer segments within polyethylene oxide and improving the rapid transport of fast ions within the quasi-solid polymer electrolyte membrane is a pressing issue for researchers. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a hydroxylated COF quasi-solid-state flexible polymer lithium battery separator, which solves the problem of poor contact performance between existing solid electrolyte separators and electrodes, resulting in high interfacial impedance of solid lithium-ion batteries. By blending the flexible polymer with inorganic materials, the crystallization tendency of polymer chain monomers is reduced, thereby reducing the problems of low mechanical strength and electrochemical performance of solid electrolytes.

[0005] The purpose of this invention is to provide a method for preparing hydroxylated COF quasi-solid-state flexible polymer lithium batteries.

[0006] The first technical solution adopted in this invention is a method for preparing a COF quasi-solid-state flexible polymer lithium battery separator, and the specific operation steps are as follows:

[0007] Step 1: Weigh 2,5-dihydroxyterephthalaldehyde and tetraaminophenylmethane, use n-butanol and o-dichlorobenzene as solvents and acetic acid as catalyst, and ultrasonically disperse them evenly. Transfer the mixture into a glass tube, pump nitrogen into the mixture to remove oxygen, freeze and thaw with liquid nitrogen, seal under vacuum, and react in an oven at 120°C for 72 hours. Filter the obtained precipitate, wash it three times with anhydrous tetrahydrofuran and acetone respectively, and then wash it by Soxhlet extraction, with acetone and THF solution each washing for 24 hours. Dry it under vacuum at 80°C for 12 hours to obtain precursor powder A, i.e., COF precursor.

[0008] Step 2: Weigh precursor powder A and dissolve it with polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) in anhydrous acetonitrile and stir at room temperature to obtain viscous liquid B.

[0009] Step 3: Pour the viscous liquid B onto the polytetrafluoroethylene template and coat it uniformly onto the polytetrafluoroethylene template using a deposition method. Under room temperature conditions, vacuum dry for 12 hours to obtain a flexible polymer solid film C with a thickness of 80-100 micrometers.

[0010] Step 4: Cut the prepared flexible polymer solid film C into round pieces, vacuum dry at 60°C, and place them in a glove box with a water oxygen value of less than 0.01 ppm to obtain the flexible solid polymer membrane D.

[0011] The invention is further characterized in that,

[0012] In step 1, the molar ratio of 2,5-dihydroxyterephthalaldehyde and tetraaminophenylmethane is 1:1; the volume ratio of n-butanol to o-dichlorobenzene is 1:1; the ultrasonic time is not less than 10 minutes; the liquid nitrogen is used for freezing; and the number of thawing cycles is not less than 3.

[0013] In step 2, the mass ratio of precursor powder A, polyethylene oxide, and lithium bis(trifluoromethanesulfonyl)imide is 1:8:1, wherein the monomer of the ethylene oxide segment in polyethylene oxide and the Li in lithium bis(trifluoromethanesulfonyl)imide are... + The mass ratio is 20:1; stirring at room temperature for no less than 48 hours; the polytetrafluoroethylene can be replaced by any one of polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride, and polyacrylonitrile.

[0014] The size of the polytetrafluoroethylene template in step 3 is 10*10cm.

[0015] The vacuum drying time in step 4 is 12 hours, and the diameter of the disc in step 4 is 19 mm.

[0016] The second technical solution adopted in this invention is a method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery, the specific operation steps of which are as follows:

[0017] Step 1: Weigh carbon black, lithium iron phosphate powder, and polyvinylidene fluoride (PVDF) in a mass ratio of 2:7:1, place them in an agate mortar, grind them thoroughly, then place them in a covered glass bottle, add an appropriate amount of N,N-2-methylpyrrolidone, stir at room temperature until evenly dispersed into a viscous black slurry; place the stirred black slurry on aluminum foil, and prepare the lithium iron phosphate cathode by a scraping method; vacuum dry at 60℃ for 12 hours, cut into round pieces with a diameter of 14 mm, and obtain the lithium iron phosphate cathode sheet; store it in a glove box with an oxygen content not exceeding 0.01 ppm for later use;

[0018] Step 2: Assemble the lithium iron phosphate positive electrode, flexible solid polymer separator D and lithium negative electrode into a CR2032 battery. The electrolyte is lithium bis(trifluoromethanesulfonylimide) and LiNO3; 1,3-dioxolane DOL and ethylene glycol dimethyl ether DME are used as solvents, with a volume ratio of 1:1.

[0019] The specific operation is as follows: the positive electrode shell, the lithium iron phosphate positive electrode sheet, and the flexible solid polymer separator D dipped in electrolyte are assembled under a pressure of 2.5N. The entire assembly process is carried out in a glove box with a water oxygen value of less than 0.01ppm.

[0020] Step 3: Let the assembled battery stand for 12 hours, then place it on a blue electrode for battery rate performance testing; test the relationship between current and time and the electrochemical impedance of the battery before and after cycling on an electrochemical workstation.

[0021] The invention is further characterized in that,

[0022] Step 3: The starting voltage for the cyclic test should not be lower than 2V. The voltage range during the cycle is 2.5-4V, the scanning voltage range is 2.5-4.2V, and the scanning rate is 0.001V / s. The number of scans is 6, and the frequency during the electrochemical impedance measurement is 0.01-1000000Hz.

[0023] The lithium iron phosphate cathode can be made of lithium cobalt oxide, lithium manganese oxide, or LiNi. 0.33 Mn 0.33 Co 0.33 Any of the following can be substituted for O2.

[0024] The electrolyte in step 2 is a mixture of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium nitrate, wherein the molar ratio of LiTFSI to lithium nitrate is 1:5.

[0025] The synthesis principle of key steps in this invention:

[0026] (I) COF Precursors: Covalent organic frameworks (COFs) are a class of inorganic materials with high orientation, high density, and one-dimensional channels formed by covalent bonds. They are characterized by ordered structure, high porosity, abundant ion transport pathways, and high thermodynamic stability. Utilizing the hydrogen bonding anchoring effect between lithium ions and the inner walls of COF channels, lithium ions can move rapidly within the one dimension of the COF, providing a transition and conduction pathway for lithium ions and achieving rapid lithium ion transport.

[0027] (II) Introduction of OH groups in COF precursors: Due to the designability and ease of functionalization of COF materials, hydroxyl-functionalized COF materials (COF-OH) were successfully synthesized by introducing 2,5-dihydroxy-terephthalaldehyde and tetraaminophenylmethane. On the one hand, the introduction of carboxyl groups allows for hydrogen bonding between the lithium salt and the carboxyl group. This hydrogen bonding can anchor lithium ions and improve lithium efficiency. + The introduction of amino groups increases the ion mobility, thereby suppressing the formation rate of lithium dendrites. Furthermore, the introduction of amino groups allows them to form azo interactions with Li+, which facilitates the uniform transport of lithium ions within the COF framework. On the other hand, the lone pair electrons of the oxygen in the hydroxyl group also participate in the Li+ ion transport. + This desolvation accelerates the ion mobility of lithium ions and improves the transport performance of lithium-ion batteries.

[0028] (III) Preparation of Hydroxylated COF Flexible Polymer Lithium-ion Battery Separator Materials: Currently, commercially available PP separators (Cegrad 2400) are commonly used in the preparation of lithium, sodium, and potassium batteries. However, commercial PP separators are expensive, and their micron-sized pores can easily lead to the presence of Li- in the battery. +The uneven distribution of electrolytes leads to short circuits and potential explosions, posing safety hazards. Therefore, developing a cost-effective and high-performance battery separator is essential. Polyethylene oxide (PEO) is one of the most commonly used polymers in solid-state polymer electrolytes. However, PEO has high crystallinity at room temperature and low ionic conductivity, which fails to meet the normal requirements of lithium batteries. This experiment found that physical doping with monomers rich in ethylene oxide segments, lithium salts, and inorganic COF effectively reduces the regularity of the molecular chains, further decreasing the crystallinity tendency of PEO and improving its ionic conductivity.

[0029] (IV) Fabrication of Flexible Polymer Quasi-Solid-State Lithium Metal Batteries: The cathode materials for quasi-solid-state batteries include lithium cobalt oxide, lithium manganese oxide, ternary materials, and lithium iron phosphate. Due to its high performance, non-toxicity, environmental friendliness, readily available and inexpensive raw materials, and long cycle life, lithium iron phosphate was chosen as the cathode material for flexible polymer quasi-solid-state lithium metal batteries. By doping lithium iron phosphate powder with conductive carbon black in a certain proportion and using PVDF as a binder, the cathode material was prepared. It was found that this electrode exhibited good conductivity and cycle stability.

[0030] The beneficial effects of this invention are:

[0031] (1) COF material was synthesized by introducing 2,5-dihydroxyterephthalaldehyde and tetraaminophenylmethane and then by freeze drying. Due to the designability of the material structure and the diversity of functional groups, lithium ions are transported uniformly and rapidly in the COF channels, which improves the ion mobility of lithium batteries.

[0032] (2) Hydroxylated COF quasi-solid-state flexible polymer lithium battery separator material was prepared by template method. Since the hydroxyl and amino functional groups form hydrogen bond interaction and azo interaction with lithium ions, it is beneficial to the uniform transport of lithium ions and ion mobility in the COF skeleton.

[0033] (3) By uniformly mixing COF, polymer, and lithium salt, a flexible solid polymer film is formed. The mechanical properties of the film are improved by utilizing the segmental effect of polymer PEO in the flexible solid polymer separator. Using flexible solid polymer separators to replace commercial separators is currently a good method to reduce electrolyte leakage in lithium-ion batteries.

[0034] (4) The lithium-ion battery has the characteristics of simple assembly method, strong safety and strong operability. The solid electrolyte can be widely used in solid / quasi-solid polymer lithium / sodium batteries.

[0035] (5) This invention provides a method for preparing a hydroxylated COF quasi-solid-state flexible polymer lithium battery separator. Furthermore, it provides reference material for applying inorganic materials to quasi-solid-state lithium batteries. This method can be used in other inorganic-filled quasi-solid-state polymer lithium / sodium batteries, significantly expanding the applicability of inorganic materials. Attached Figure Description

[0036] Figure 1 This is a flowchart of the method for preparing the hydroxylated COF quasi-solid-state flexible lithium battery separator of the present invention;

[0037] Figure 2 This is a flowchart of the method for preparing hydroxylated COF quasi-solid-state flexible lithium batteries according to the present invention;

[0038] Figure 3 This is a graph showing the relationship between efficiency and specific capacity of the hydroxylated COF quasi-solid-state flexible lithium battery of the present invention after 100 cycles at a rated capacitance of 0.2C.

[0039] Figure 4 This is a rate capability diagram of the hydroxylated COF quasi-solid-state flexible lithium battery of the present invention under different rated capacitors.

[0040] Figure 5 This is a graph showing the relationship between current and potential of the hydroxylated COF quasi-solid-state flexible lithium battery of the present invention at different scan rates.

[0041] Figure 6 This is an electrochemical impedance spectroscopy diagram of the hydroxylated COF quasi-solid-state flexible lithium battery before and after cycling, according to the present invention. Detailed Implementation

[0042] The present invention provides a method for preparing hydroxylated COF quasi-solid-state flexible polymer lithium batteries, including the synthesis of COF materials by combining them with polymers PEO and Li. + -TFSI - The hydroxylated COF quasi-solid-state flexible polymer lithium battery separator was prepared by blending and then assembled with lithium iron phosphate cathode and lithium anode to form a flexible quasi-solid-state polymer lithium-ion battery.

[0043] The present invention will be further described below with reference to specific embodiments.

[0044] Example 1

[0045] Methods for preparing hydroxylated COF quasi-solid-state flexible polymer lithium battery separators, such as... Figure 1 As shown, the specific operation steps are as follows:

[0046] Step 1: Weigh 2,5-dihydroxyterephthalaldehyde and tetraaminophenylmethane, and use n-butanol and o-dichlorobenzene as solvents and acetic acid as catalyst to ultrasonically disperse them uniformly. Transfer the mixture into a Pyrex tube, pump nitrogen into the mixture to remove oxygen, freeze and thaw it three times with liquid nitrogen, then vacuum seal it and place it in an oven at 120°C for 72 hours. Filter the obtained precipitate, wash it three times with anhydrous tetrahydrofuran and acetone respectively, then wash it with Soxhlet extraction for 48 hours (24 hours each with acetone and THF solution), and vacuum dry it at 80°C for 12 hours to obtain orange-yellow precursor powder A.

[0047] The volume ratio of n-butanol to o-dichlorobenzene is 1:1, the liquid nitrogen freezing and thawing is repeated at least 3 times, and the Soxhlet extraction washing time is at least 48 hours.

[0048] Step 2: Weigh precursor powder A, polyethylene oxide (PEO), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and use anhydrous acetonitrile as solvent. Transfer them to a flat-bottomed flask and stir at room temperature to obtain an orange-yellow viscous liquid B.

[0049] Step 3: Pour the orange-yellow viscous liquid B onto the polytetrafluoroethylene mold, and coat it evenly onto the polytetrafluoroethylene template using a deposition method. Under room temperature conditions, vacuum dry for 12 hours to obtain an orange-yellow flexible polymer solid film C with a thickness of 80-100 micrometers.

[0050] Step 4: Cut the prepared orange flexible polymer solid film C into round pieces, dry them under vacuum overnight at 60°C, and place them in a glove box with a water oxygen value of less than 0.01 ppm to obtain flexible solid polymer membrane D.

[0051] like Figure 2 As shown, the specific steps for preparing a hydroxylated COF quasi-solid-state flexible polymer lithium battery are as follows:

[0052] Step 1: Weigh carbon black (Super-P), lithium iron phosphate powder, and polyvinylidene fluoride (PVDF) into an agate mortar in a mass ratio of 2:7:1. Grind thoroughly and place in a 10mL glass bottle with a cap. Add an appropriate amount of N,N-2-methylpyrrolidone (NMP) and stir overnight at room temperature to disperse into a uniform, viscous black slurry. Place the stirred black slurry on aluminum foil and prepare a lithium iron phosphate (LFP) cathode by a scraping method. Vacuum dry at 60℃ for 12 hours and cut into 14mm diameter discs to obtain lithium iron phosphate (LFP) electrodes. Store in a glove box with an oxygen content not exceeding 0.01ppm for later use.

[0053] Step 2: Assemble the lithium iron phosphate (LFP) electrode E, flexible solid polymer separator D, and lithium negative electrode into a CR2032 battery. The electrolyte is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and LiNO3; 1,3-dioxolane DOL and ethylene glycol dimethyl ether DME are used as solvents in a 1:1 volume ratio. Specifically, the positive electrode shell, lithium iron phosphate electrode E, flexible solid polymer separator D soaked in electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell are placed sequentially and assembled on a packaging machine under a pressure of 2.5 N. The entire assembly process is carried out in a glove box with a water and oxygen level of less than 0.01 ppm.

[0054] Step 3: Let the assembled battery stand for 12 hours, then place it on a blue battery for a cycle test;

[0055] Step 4: Test the rate performance of the battery on Blue Electric.

[0056] Step 5: Test the relationship between the current and time of the battery on an electrochemical workstation;

[0057] Step 6: Test the electrochemical impedance of the battery before and after cycling on an electrochemical workstation at a frequency of 0.001-100000Hz.

[0058] Example 2

[0059] Methods for preparing hydroxylated COF quasi-solid-state flexible polymer lithium battery separators, such as... Figure 1 As shown, the specific operation steps are as follows:

[0060] Step 1: Weigh 2,5-dihydroxyterephthalaldehyde and tetraaminophenylmethane, and use n-butanol and o-dichlorobenzene as solvents and acetic acid as catalyst to ultrasonically disperse them uniformly. Transfer the mixture into a Pyrex tube, pump nitrogen into the mixture to remove oxygen, freeze and thaw it three times with liquid nitrogen, then vacuum seal it and place it in an oven at 120°C for 72 hours. Filter the obtained precipitate, wash it three times with anhydrous tetrahydrofuran and acetone respectively, then wash it with Soxhlet extraction for 48 hours (24 hours each with acetone and THF solution), and vacuum dry it at 80°C for 12 hours to obtain orange-yellow precursor powder A.

[0061] The volume ratio of n-butanol to o-dichlorobenzene is 1:1, the liquid nitrogen freezing and thawing process is no less than 3 times, and the Soxhlet extraction washing time is no less than 48 hours.

[0062] Step 2: Weigh precursor powder A, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and lithium bis(trifluoromethanesulfonylimide) (LiTFSI). Using N,N-dimethylpyrrolidone as a solvent, transfer them to a flat-bottomed flask and stir at room temperature to obtain an orange-yellow viscous liquid B.

[0063] Step 3: Pour the orange-yellow viscous liquid B onto the polytetrafluoroethylene template, coat it evenly onto the polytetrafluoroethylene template by scraping, and vacuum dry it for 12 hours at room temperature to obtain an orange-yellow polymer solid film C with a thickness of 80-100 micrometers.

[0064] Step 4: Cut the prepared orange-yellow polymer solid film C into round pieces, dry them under vacuum overnight at 60°C, and place them in a glove box with a water oxygen value of less than 0.01 ppm to obtain a flexible solid polymer membrane D.

[0065] The specific steps for preparing a hydroxylated COF quasi-solid-state flexible polymer lithium battery are as follows:

[0066] Step 1: Weigh carbon black (Super-P), lithium iron phosphate powder, and polyvinylidene fluoride (PVDF) into an agate mortar in a mass ratio of 1:8:1. Grind thoroughly and place in a 10mL glass bottle with a cap. Add an appropriate amount of N,N-2-methylpyrrolidone (NMP) and stir overnight at room temperature to disperse into a uniform, viscous black slurry. Place the stirred black slurry on aluminum foil and prepare a lithium iron phosphate (LFP) cathode by a scraping method. Vacuum dry at 60℃ for 14 hours and cut into 14mm diameter discs to obtain lithium iron phosphate electrode sheets (LFP)E. Store in a glove box with an oxygen content not exceeding 0.01ppm for later use.

[0067] Step 2: Assemble the lithium iron phosphate (LFP) electrode E, flexible solid polymer separator D, and lithium negative electrode into a CR2032 battery. The electrolyte is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and LiNO3; 1,3-dioxolane DOL and ethylene glycol dimethyl ether DME are used as solvents in a 1:1 volume ratio. Specifically, the positive electrode shell, lithium iron phosphate electrode E, flexible solid polymer separator D soaked in electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell are placed sequentially and assembled on a packaging machine under a pressure of 2.5 N. The entire assembly process is carried out in a glove box with a water and oxygen level of less than 0.01 ppm.

[0068] Step 3: Let the assembled battery stand for 18 hours, then place it on a blue battery for a cycle test;

[0069] Step 4: Test the rate performance of the battery on Blue Electric.

[0070] Step 5: Test the relationship between the current and time of the battery on an electrochemical workstation;

[0071] Step 6: Test the electrochemical impedance of the battery before and after cycling on an electrochemical workstation at a frequency of 0.001-100000Hz.

[0072] Example 3

[0073] Methods for preparing hydroxylated COF quasi-solid-state flexible polymer lithium battery separators, such as... Figure 1 As shown, the specific operation steps are as follows:

[0074] Step 1: Weigh 2,5-dihydroxyterephthalaldehyde and tetraaminophenylmethane, and use n-butanol and o-dichlorobenzene as solvents and acetic acid as catalyst to ultrasonically disperse them uniformly. Transfer the mixture into a Pyrex tube, pump nitrogen into the mixture to remove oxygen, freeze and thaw it three times with liquid nitrogen, then vacuum seal it and place it in an oven at 120°C for 72 h. Filter the obtained precipitate, wash it three times with anhydrous tetrahydrofuran and acetone respectively, then wash it with Soxhlet extraction for 72 hours (36 h each with acetone and THF solution), and vacuum dry it at 80°C for 24 h to obtain orange-yellow precursor powder A.

[0075] The volume ratio of n-butanol to o-dichlorobenzene is 1:1, the liquid nitrogen freezing and thawing is repeated at least 3 times, and the Soxhlet extraction washing time is at least 48 hours.

[0076] Step 2: Weigh precursor powder A, polyvinylidene fluoride (PVDF), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and use N,N-dimethylpyrrolidone as solvent. Transfer the mixture to a flat-bottomed flask and stir at room temperature to obtain an orange-yellow viscous liquid B.

[0077] Step 3: Pour the orange-yellow viscous liquid B onto the polytetrafluoroethylene template and coat it evenly onto the polytetrafluoroethylene template using a scraping method. Under room temperature, vacuum dry for 12 hours to obtain an orange-yellow flexible polymer solid film C with a thickness of 80-90 micrometers.

[0078] Step 4: Cut the prepared orange flexible polymer solid film C into round pieces, dry them under vacuum overnight at 60°C, and place them in a glove box with a water oxygen value of less than 0.01 ppm to obtain flexible solid polymer membrane D.

[0079] The specific steps for preparing a hydroxylated COF quasi-solid-state flexible polymer lithium battery are as follows:

[0080] Step 1: Weigh carbon black (Super-P), lithium cobalt oxide powder, and polyvinylidene fluoride (PVDF) into an agate mortar in a mass ratio of 1:8:1. Grind thoroughly and place in a 10mL glass bottle with a cap. Add an appropriate amount of N,N-2-methylpyrrolidone (NMP) and stir overnight at room temperature to disperse into a uniform, viscous black slurry. Place the stirred black slurry on aluminum foil and prepare the lithium cobalt oxide cathode using a scraping method. Vacuum dry at 60℃ for 12 hours and cut into 14mm diameter discs to obtain lithium cobalt oxide electrode E. Store in a glove box with an oxygen content not exceeding 0.01ppm for later use.

[0081] Step 2: Assemble the lithium cobalt oxide electrode E, flexible solid polymer separator D, and lithium negative electrode into a CR2032 battery. The electrolyte is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and LiNO3; 1,3-dioxolane DOL and ethylene glycol dimethyl ether DME are used as solvents in a 1:1 volume ratio. Specifically, the positive electrode shell, lithium cobalt oxide electrode E, flexible solid polymer separator D soaked in electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell are placed sequentially and assembled on a packaging machine under a pressure of 2.5 N. The entire assembly process is carried out in a glove box with a water and oxygen level less than 0.01 ppm.

[0082] Step 3: Let the assembled battery stand for 12 hours, then place it on a blue battery for a cycle test;

[0083] Step 4: Test the rate performance of the battery on Blue Electric.

[0084] Step 5: Test the relationship between the current and time of the battery on an electrochemical workstation;

[0085] Step 6: Test the electrochemical impedance of the battery before and after cycling on an electrochemical workstation at a frequency of 0.001-100000Hz.

[0086] Example 4

[0087] Methods for preparing hydroxylated COF quasi-solid-state flexible polymer lithium battery separators, such as... Figure 1 As shown, the specific operation steps are as follows:

[0088] Step 1: Weigh 2,5-dihydroxyterephthalaldehyde and tetraaminophenylmethane, and use n-butanol and o-dichlorobenzene as solvents and acetic acid as catalyst to ultrasonically disperse them uniformly. Transfer the mixture into a Pyrex tube, pump nitrogen into the mixture to remove oxygen, freeze and thaw it three times with liquid nitrogen, then vacuum seal it and place it in an oven at 120°C for 72 hours. Filter the obtained precipitate, wash it three times with anhydrous tetrahydrofuran and acetone respectively, then wash it with Soxhlet extraction for 48 hours (24 hours each with acetone and THF solution), and vacuum dry it at 80°C for 12 hours to obtain orange-yellow precursor powder A.

[0089] The volume ratio of n-butanol to o-dichlorobenzene is 1:1, the liquid nitrogen freezing and thawing process is no less than 3 times, and the Soxhlet extraction washing time is no less than 48 hours.

[0090] Step 2: Weigh precursor powder A and lithium polyacrylonitrile, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), use N,N-2-methylpyrrolidone as solvent, transfer them to a flat-bottomed flask, and stir at room temperature to obtain orange-yellow viscous liquid B.

[0091] Step 3: Pour the orange-yellow viscous liquid B onto the polytetrafluoroethylene mold, and coat it evenly onto the polytetrafluoroethylene template using a deposition method. Under room temperature conditions, vacuum dry for 12 hours to obtain an orange-yellow flexible polymer solid film C with a thickness of 80-100 micrometers.

[0092] Step 4: Cut the prepared orange flexible polymer solid film C into round pieces, dry them under vacuum overnight at 70°C, and place them in a glove box with a water oxygen value of less than 0.01 ppm to obtain the flexible solid polymer membrane D.

[0093] The specific steps for preparing a hydroxylated COF quasi-solid-state flexible polymer lithium battery are as follows:

[0094] Step 1: Weigh carbon black (Super-P), lithium manganese oxide powder, and polyvinylidene fluoride (PVDF) into an agate mortar in a mass ratio of 1:8:1. Grind thoroughly and then place in a 10mL glass bottle with a cap. Add an appropriate amount of N,N-2-methylpyrrolidone (NMP) and stir overnight at room temperature to disperse into a uniform, viscous black slurry. Place the stirred black slurry on aluminum foil and prepare the lithium manganese oxide cathode using a scraping method. Vacuum dry at 60℃ for 12 hours and cut into round pieces with a diameter of 14mm to obtain lithium manganese oxide electrode E. Store in a glove box with an oxygen content not exceeding 0.01ppm for later use.

[0095] Step 2: Assemble the lithium manganese oxide electrode E, flexible solid polymer separator D, and lithium negative electrode into a CR2032 battery. The electrolyte is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and LiNO3; 1,3-dioxolane DOL and ethylene glycol dimethyl ether DME are used as solvents in a 1:1 volume ratio. Specifically, the positive electrode shell, lithium manganese oxide electrode E, flexible solid polymer separator D soaked in electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell are placed sequentially and assembled on a packaging machine under a pressure of 2.5 N. The entire assembly process is carried out in a glove box with a water and oxygen level less than 0.01 ppm.

[0096] Step 3: Let the assembled battery stand for 12 hours, then place it on a blue battery for a cycle test;

[0097] Step 4: Test the rate performance of the battery on Blue Electric.

[0098] Step 5: Test the relationship between the current and time of the battery on an electrochemical workstation;

[0099] Step 6: Test the electrochemical impedance of the battery before and after cycling on an electrochemical workstation at a frequency of 0.001-100000Hz.

[0100] Example 5

[0101] Methods for preparing hydroxylated COF quasi-solid-state flexible polymer lithium battery separators, such as... Figure 1 As shown, the specific operation steps are as follows:

[0102] Step 1: Weigh 2,5-dihydroxyterephthalaldehyde and tetraaminophenylmethane, and use n-butanol and o-dichlorobenzene as solvents and acetic acid as catalyst to ultrasonically disperse them uniformly. Transfer the mixture into a Pyrex tube, pump nitrogen into the mixture to remove oxygen, freeze and thaw it three times with liquid nitrogen, then vacuum seal it and place it in an oven at 120°C for 72 hours. Filter the obtained precipitate, wash it three times with anhydrous tetrahydrofuran and acetone respectively, then wash it with Soxhlet extraction for 48 hours (24 hours each with acetone and THF solution), and vacuum dry it at 80°C for 12 hours to obtain orange-yellow precursor powder A.

[0103] The volume ratio of n-butanol to o-dichlorobenzene is 1:1, the liquid nitrogen freezing and thawing is repeated at least 3 times, and the Soxhlet extraction washing time is at least 48 hours.

[0104] Step 2: Weigh precursor powder A, polyethylene oxide (PEO), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and use anhydrous acetonitrile as solvent. Transfer them to a flat-bottomed flask and stir at room temperature to obtain an orange-yellow viscous liquid B.

[0105] Step 3: Pour the orange-yellow viscous liquid B onto the polytetrafluoroethylene mold, and coat it evenly onto the polytetrafluoroethylene template using a deposition method. Under room temperature conditions, vacuum dry for 12 hours to obtain an orange-yellow flexible polymer solid film C with a thickness of 80-100 micrometers.

[0106] Step 4: Cut the prepared orange flexible polymer solid film C into round pieces, dry them under vacuum overnight at 60°C, and place them in a glove box with a water oxygen value of less than 0.01 ppm to obtain flexible solid polymer membrane D.

[0107] The specific steps for preparing a hydroxylated COF quasi-solid-state flexible polymer lithium battery are as follows:

[0108] Step 1, weigh out carbon black (Super-P) and LiNi 0.33 Mn 0.33 Co 0.33 O2 powder and polyvinylidene fluoride (PVDF) were ground thoroughly in an agate mortar at a mass ratio of 1:8:1. The mixture was then placed in a 10mL capped glass bottle, and an appropriate amount of N,N-2-methylpyrrolidone (NMP) was added. The mixture was stirred overnight at room temperature to disperse it into a uniform, viscous black slurry. The stirred black slurry was then placed on aluminum foil and coated using a blade coating method to prepare LiNi. 0.33 Mn 0.33 Co 0.33O2 cathode, vacuum dried at 60℃ for 12 h, cut into circular pieces with a diameter of 14 mm to obtain LiNi. 0.33 Mn 0.33 Co 0.33 O2 electrode E; store in a glove box with an oxygen level not exceeding 0.01 ppm for later use.

[0109] Step 2, LiNi 0.33 Mn 0.33 Co 0.33 The O2 electrode E, flexible solid polymer separator D, and lithium negative electrode are assembled into a CR2032 battery. The electrolyte is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and LiNO3; 1,3-dioxolane DOL and ethylene glycol dimethyl ether DME are used as solvents, with a volume ratio of 1:1. The specific operation is as follows: the positive electrode shell, LiNi 0.33 Mn 0.33 Co 0.33 The O2 electrode E, the flexible solid polymer separator D soaked in electrolyte, the lithium sheet, gasket, spring, and negative electrode shell are placed in sequence and assembled on a packaging machine under a pressure of 2.5N. The entire assembly process is carried out in a glove box with a water and oxygen level of less than 0.01ppm.

[0110] Step 3: Let the assembled battery stand for 12 hours, then place it on a blue battery for a cycle test;

[0111] Step 4: Test the rate performance of the battery on Blue Electric.

[0112] Step 5: Test the relationship between the current and time of the battery on an electrochemical workstation;

[0113] Step 6: Test the electrochemical impedance of the battery before and after cycling on an electrochemical workstation at a frequency of 0.001-100000Hz.

[0114] like Figure 3 The figure shows the relationship between efficiency and specific capacity of hydroxylated COF quasi-solid-state flexible polymer lithium-ion batteries under slow charging current density of 0.2C. Clearly, after 100 cycles under slow charging current density of 0.2C, COF-OH maintains a specific capacity of 153 mAh g⁻¹ and a capacity retention of 95%.

[0115] like Figure 4 The figure shows the rate capability of a hydroxylated COF quasi-solid-state flexible polymer lithium-ion battery after 10 cycles at different current densities. Clearly, the charge / discharge specific capacities of the COF-OH solid polymer film at current densities of 0.1C, 0.2C, 0.5C, 1C, and 2C are 165, 153, 137, 116, and 95 mA hg, respectively. -1The efficiency is close to 100%. This is due to the synthesized covalent organic COFs material containing hydroxyl and amino functional groups. This material has excellent one-dimensional channels and functional group modifiability, which can accelerate the uniform transport of lithium ions. In addition, the hydrogen bonding and azo interactions between the hydroxyl and amino functional groups and lithium ions are beneficial to the uniform transport and ion mobility of lithium ions in the COF framework. At the same time, the presence of polymer PEO gives the polymer separator excellent mechanical properties and good interfacial compatibility, further improving the thermal stability of the quasi-solid-state polymer lithium-ion battery.

[0116] like Figure 5 The figure shows the ion transference number test of the hydroxylated COF quasi-solid-state flexible polymer lithium battery prepared in this invention under an electrochemical workstation. First, a lithium-lithium symmetric battery was assembled, and the impedance of the battery was tested at a frequency of 0.01-10. 6 Secondly, the it curve of the battery was tested at a time of 2000 s and a polarization voltage of 10 mV. Finally, the EIS of the battery after polarization was tested. The calculated lithium-ion transference number of the battery was 0.786. This indicates that the flexible solid polymer separator prepared by combining COF material and PEO polymer has good interfacial compatibility in lithium-ion batteries, improving the lithium-ion transport rate.

[0117] like Figure 6 The figure shows the electrochemical impedance spectroscopy (EIS) measurements of the hydroxylated COF quasi-solid-state flexible polymer lithium battery prepared in this invention before and after cycling under an electrochemical workstation, with a frequency of 0.01-100000 Hz. The figure shows that the charge transfer resistance before cycling is 131.73 Ω, and the charge transfer resistance after 100 cycles is 438.99 Ω. This indicates that the internal resistance of the hydroxylated COF quasi-solid-state flexible polymer lithium battery separator material increases during battery cycling, but it still has a low initial internal resistance. This also demonstrates that the hydroxylated COF quasi-solid-state flexible polymer lithium battery separator material has low impedance and high electron conductivity.

[0118] This invention utilizes a blend of COF, polyethylene oxide, and inorganic lithium salt to prepare a quasi-solid-state electrolyte membrane exhibiting excellent electrochemical performance and high ionic conductivity. The ion transference number of this quasi-solid-state electrolyte is 0.786 at room temperature, and the current density at a slow charging current density of 0.2C is 153 mAh g⁻¹. -1 The coulombic efficiency is 95%. This is due to the hydrogen bonding anchoring effect between lithium ions and the inner wall of the COF channel, which provides a transition and conduction pathway for lithium ions, enabling them to move rapidly within the one-dimensional COF channel and achieve rapid lithium ion transport.

Claims

1. A method for the preparation of a hydroxylated COF flexible quasi-solid state lithium battery separator, characterized in that, The specific operation steps are as follows: Step 1, weigh 2, 5-dihydroxy terephthaldehyde and tetraamino phenyl methane, take n-butanol and o-dichlorobenzene as solvents, and take acetic acid as catalyst, ultrasonic homogeneously disperse, move the mixture into a glass tube, pump nitrogen into the mixture to remove oxygen, after freezing and thawing by liquid nitrogen, vacuum seal, place in a 120°C oven for 72h; filter the obtained precipitate, wash with anhydrous tetrahydrofuran, acetone 3 times respectively, then wash with soxhlet extraction method, among which acetone and THF solution each washes for 24h; 80°C vacuum drying for 12h, obtain precursor powder A; Step 2, weigh precursor powder A and polyethylene oxide, lithium bis-trifluoromethanesulfonimide in anhydrous acetonitrile, stir at room temperature to obtain viscous liquid B; Step 3, pour viscous liquid B into a polytetrafluoroethylene template, uniformly coat on the polytetrafluoroethylene template by deposition method, vacuum drying for 12h at room temperature, obtain flexible polymer solid-state thin film C with a thickness of 80-100 microns; Step 4, cut the prepared flexible polymer solid-state thin film C into a round piece, vacuum drying at 60°C, and place it in a glove box with water and oxygen value less than 0.01ppm, obtain flexible solid-state polymer separator D.

2. The method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery separator according to claim 1, characterized in that, The molar ratio of 2, 5-dihydroxy terephthaldehyde and tetraamino phenyl methane in step 1 is 1:1; The volume ratio of n-butanol and o-dichlorobenzene is 1:1, the ultrasonic time is not less than 10 minutes, the liquid nitrogen freezing and thawing times are not less than 3 times.

3. The method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery separator according to claim 1, characterized in that, The mass ratio of precursor powder A, polyethylene oxide and lithium bis-trifluoromethanesulfonimide in step 2 is 1:8:1, wherein the monomer of ethylene oxide segment in polyethylene oxide and Li in lithium bis-trifluoromethanesulfonimide + The mass ratio of the lithium bis-trifluoromethanesulfonimide and the polytetrafluoroethylene template is 20:1; stirring at room temperature for no less than 48 hours; the polytetrafluoroethylene template can be replaced by a template made of any one of polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinylidene fluoride and polyacrylonitrile.

4. The method of claim 1, wherein the hydroxylated COF flexible quasi-solid-state lithium battery separator is prepared by the method comprising: The size of the polytetrafluoroethylene template in step 3 is 10*10cm.

5. The method of claim 1, wherein the hydroxylated COF flexible quasi-solid-state lithium battery separator is prepared by the method comprising: The vacuum drying time in step 4 is 12h, and the diameter of the round piece in step 4 is 19mm.

6. A method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery, characterized in that, The specific operation steps of using the flexible solid-state polymer separator D in any one of claims 1-5 are as follows: Step 1: weigh carbon black, lithium iron phosphate powder and polyvinylidene fluoride PVDF according to the mass ratio of 2:7:1, place in an agate mortar, grind thoroughly, then place in a glass bottle with a lid, add appropriate amount of N,N-2-methylpyrrolidone, stir at room temperature, disperse uniformly into a viscous black slurry; place the stirred black slurry on aluminum foil, prepare lithium iron phosphate positive electrode by doctor blade method, vacuum drying at 60°C for 12h, cut into a round piece with a diameter of 14mm, obtain lithium iron phosphate positive electrode piece; place in a glove box with water and oxygen value not more than 0.01ppm for standby; Step 2, assemble the lithium iron phosphate positive electrode piece, flexible solid-state polymer separator D and lithium negative electrode into a CR2032 type battery, the electrolyte is lithium bis-trifluoromethanesulfonimide, LiNO3, 1,3-dioxolane DOL, ethylene glycol dimethyl ether DME; 1,3-dioxolane DOL and ethylene glycol dimethyl ether DME as solvent, the volume ratio of the two is 1:1; The specific operation is: assemble the positive electrode shell, lithium iron phosphate positive electrode piece, and flexible solid-state polymer separator D dipped with electrolyte, the pressure is 2.5N, the whole assembly process is carried out in a glove box with water and oxygen value less than 0.01ppm; Step 3: The above CR2032 battery was rested for 12 hours and then placed on a blue cell for battery rate capability test; the current versus time relationship of the battery and the electrochemical impedance of the battery before and after cycling were tested on an electrochemical workstation.

7. The method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery according to claim 6, characterized in that, The cycle test starting voltage in step 3 was not less than 2V, the voltage range during cycling was 2.5-4V, the scanning voltage range was 2.5-4.2V, the scanning rate was 0.001V / s; the scanning number was 6 circles, and the frequency was 0.01-1000000Hz when the electrochemical impedance was measured.

8. The method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery according to claim 6, characterized in that, The lithium iron phosphate positive electrode sheet can be replaced by any one of lithium cobaltate, lithium manganate, LiNi 0.33 Mn 0.33 Co 0.33 O2.

9. The method for preparing a hydroxylated COF flexible quasi-solid-state lithium battery according to claim 6, characterized in that, The electrolyte in step 2 was a mixture of lithium bis(trifluoromethanesulfonyl)imide LiTFSI and lithium nitrate, and the molar ratio of lithium bis(trifluoromethanesulfonyl)imide LiTFSI to lithium nitrate was 1:5.

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