Covalent organic framework composite polymer electrolyte as well as preparation method and application thereof

Abstract

The invention belongs to the field of polymer electrolytes, and particularly relates to a covalent organic framework composite polymer electrolyte as well as a preparation method and application thereof. An amino monomer and an aldehyde group monomer for synthesizing the covalent organic framework are dissolved in a proper polymer monomer, a proper Lewis acid catalyst is selected, and the covalent organic framework with a porous structure is synthesized by the amino monomer and the aldehyde group monomer under the action of the catalyst; polymer monomers are subjected to polymerization reaction in pore channels of the covalent organic framework, so that polymer chains are directionally generated in the pore channels, and synthesis of the covalent organic framework and in-situ orthogonal polymerization of polymer monomer polymerization are realized. According to the preparation method provided by the invention, the covalent organic framework is ensured to be uniformly dispersed in the polymer, the preparation process of the covalent organic framework composite polymer electrolyte is simplified, the preparation period is shortened, the manufacturing cost is reduced, and the electrochemical performance of the covalent organic framework composite polymer electrolyte is improved.

Description

Technical Field

[0001] This application belongs to the field of polymer electrolytes, and more specifically, relates to a covalent organic framework composite polymer electrolyte, its preparation method and application. Background Art

[0002] The energy density of traditional lithium-ion batteries is approaching the theoretical limit of materials, making it difficult to meet the higher range requirements of new energy vehicles. Moreover, its rapid charge and discharge capabilities and long cycle life performance are poor, restricting the development of the industry. Polymer lithium-ion batteries (PLBs) have become an ideal choice for future power batteries of new energy vehicles due to advantages such as safety performance, relatively high energy density, good cycle stability, and a wide operating temperature range. Among them, polymer electrolytes are an important research direction for lithium-ion batteries, and solid polymer electrolytes show broad prospects.

[0003] Composite polymer electrolytes (CPEs) combine the advantages of fillers and polymer solid electrolytes. They consist of an organic phase (polymer electrolyte) and fillers, and have broad application prospects in high-energy density battery systems such as lithium-ion batteries. The fillers in CPEs systems are divided into conductive fillers and inert fillers. Conductive fillers such as inorganic ceramic electrolyte particles, and inert fillers such as oxide nanoparticles and porous materials. When conductive fillers are used alone, there are problems of large interfacial resistance and poor processability. Inert fillers can improve the electrochemical performance of the electrolyte through interaction with polymers or lithium salts. Aggregation of fillers will destroy the uniformity of the polymer matrix, reduce the ionic conductivity, exacerbate the interfacial resistance between the electrolyte and the electrode, affect the lithium ion transport efficiency, threaten the battery safety, and also affect the thermal stability, overall strength toughness and processability of the electrolyte.

[0004] Porous materials have become ideal fillers for preparing CPEs due to their unique long-range ordered pores and lower ion transport barriers. As a type of porous material, covalent organic frameworks are formed by connecting organic molecular building blocks through covalent bonds. They are similar in chemical structure and physical properties to polymer electrolytes, with better interfacial compatibility and dispersibility, and can improve the ion transport efficiency and mechanical properties of the electrolyte.

[0005] The traditional method for preparing covalent organic framework composite polymer electrolytes is mainly to physically mix covalent organic framework powders with polymer solutions, but there are problems of uneven filler dispersion, and the fillers are prone to secondary aggregation during the subsequent solvent evaporation process, thereby affecting the electrolyte performance. Patent document CN118538996A prepares a solid electrolyte composite of covalent organic framework and PDOL by in-situ polymerization reaction of polymer monomers (1,3-dioxolane, DOL) in the pores of covalent organic framework (COF), but there are problems such as complex preparation steps, high preparation temperature, long preparation cycle, high energy consumption, and the electrochemical performance of the electrolyte needs to be improved. Summary of the Invention

[0006] In view of the defects of the prior art, the purpose of the present application is to provide a covalent organic framework composite polymer electrolyte and its preparation method and application, aiming to solve the problems of the existing composite polymer electrolytes, such as complex preparation steps, long preparation cycle, high cost, and the need to improve the electrochemical performance of the electrolyte.

[0007] To achieve the above objectives, in a first aspect, the present application provides a method for preparing a covalent organic framework composite polymer electrolyte, comprising the following steps: The amino monomer, the aldehyde monomer, the lithium salt, the polymer monomer and the Lewis acid catalyst are mixed to obtain an electrolyte precursor solution, and the covalent organic framework composite polymer electrolyte is obtained by an in-situ reaction.

[0008] Preferably, the amino monomer is one or more of 1,3,5-tris(4-aminophenyl)benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin, tris(4-aminophenyl)amine and 5'-(4-amino-3,5-difluorophenyl)-3,3'',5,5''-tetrafluoro-[1,1':3',1''-terphenyl]-4,4''-diamine.

[0009] Preferably, the aldehyde monomer is one or more of terephthalaldehyde, 2,3,5,6-tetrafluorobenzaldehyde, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 2,5-dihydroxyterephthalaldehyde, 1,4-dialdehyde-2,5-divinylbenzene and 2,2'-bipyridine-5,5'-dicarboxaldehyde.

[0010] Preferably, the polymer monomer is one or more of trimethylene carbonate, propylene oxide, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane and trioxymethylene.

[0011] Preferably, the total mass of the amino monomer and the aldehyde monomer accounts for 2% to 15% of the mass of the polymer monomer.

[0012] Preferably, the Lewis acid catalyst is one or more of boron trifluoride ethyl etherate, boron trifluoride tetrahydrofuran, scandium trifluoromethanesulfonate, yttrium trifluoromethanesulfonate, stannous octoate, aluminum chloride and antimony trichloride.

[0013] Preferably, the amount of the Lewis acid catalyst is 0.2% to 3% of the total mass of the amino monomer, aldehyde monomer and polymer monomer.

[0014] Preferably, the lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorosulfonylimide), lithium nitrate and lithium iodide.

[0015] Preferably, the temperature of the in-situ polymerization reaction is 0°C to 40°C, and the time of the in-situ polymerization reaction is 12 h to 72 h.

[0016] In a second aspect, the present application provides a covalent organic framework composite polymer electrolyte prepared by the above preparation method.

[0017] In a third aspect, the present application provides a lithium-ion battery, which includes the above covalent organic framework composite polymer electrolyte.

[0018] In a fourth aspect, the present application provides a preparation method of the above lithium-ion battery, including the following steps: Mix the above amino monomer, aldehyde monomer, lithium salt, polymer monomer and Lewis acid catalyst to obtain an electrolyte precursor solution; then apply the above electrolyte precursor solution on the surface of the separator, and assemble a lithium-ion battery including the separator, and perform an in-situ reaction to obtain a lithium-ion battery.

[0019] Generally speaking, compared with the prior art by the above technical solutions conceived by the present application, the following technical advantages are mainly achieved: (1) In the present application, by dissolving the amino monomer and aldehyde monomer used for synthesizing the covalent organic framework in a suitable polymer monomer and selecting a suitable Lewis acid catalyst, under the action of this catalyst, while the amino monomer and aldehyde monomer are synthesized into a covalent organic framework with a porous structure, the polymer monomer undergoes a polymerization reaction in the pores of the covalent organic framework, enabling the polymer chains to be generated directionally in the pores, realizing the in-situ orthogonal polymerization of the synthesis of the covalent organic framework and the polymerization of the polymer monomer. The preparation method provided by the present application simplifies the preparation process of the covalent organic framework composite polymer electrolyte, shortens the preparation cycle, reduces the manufacturing cost, and at the same time greatly improves its electrochemical performance, that is, provides a method for efficiently preparing a high-performance covalent organic framework composite polymer electrolyte.

[0020] (2) In the present application, by reasonably designing the catalyst and the structures of the amino monomer, aldehyde monomer and polymer monomer, there is no need to additionally introduce a variety of catalysts, polar solvents or other compounds, nor is it necessary to perform complex covalent organic framework pretreatment (such as pre-freezing treatment) steps. Only the selected Lewis acid catalyst can simultaneously orthogonally catalyze the synthesis of the covalent organic framework and the polymerization of the polymer monomer, realizing the homogeneous room-temperature synthesis of the covalent organic framework in the polymer monomer environment and the directional polymerization growth of the polymer monomer in the pores of the covalent organic framework, and preparing a covalent organic framework composite polymer electrolyte.

[0021] (3) Compared with the traditional preparation method of composite polymer electrolytes, the unique strategy of in-situ orthogonal polymerization of the synthesis reaction of covalent organic frameworks and the polymerization reaction of polymer monomers adopted in this application effectively solves the problem of uneven dispersion of covalent organic frameworks in polymers, significantly improves the dispersion of covalent organic frameworks in polymers, maximizes the entanglement effect between covalent organic frameworks and polymers, and fully utilizes the advantages of its long-range ordered pore structure, enabling the polymer chains to grow directionally in the pores of covalent organic frameworks to form regular migration paths. Furthermore, it greatly reduces the transport resistance of lithium ions, effectively lowers the migration activation energy, significantly accelerates the lithium ion transport rate, and greatly improves the electrochemical performance of the covalent organic framework composite polymer electrolyte, providing ideas and technical support for the design and preparation of high-performance composite polymer electrolyte materials.

[0022] (4) The covalent organic framework composite polymer electrolyte provided in this application can be applied to match high-voltage cathode materials and is simultaneously compatible with metal lithium anode materials. It has excellent electrochemical performance and is suitable as an electrolyte for lithium-ion batteries. In addition, the preparation method of the covalent organic framework composite polymer electrolyte and the lithium-ion battery preparation method provided in this application are fully compatible with the existing battery processes. The preparation of the composite polymer electrolyte can be achieved during the battery assembly process without introducing additional battery preparation steps. On the premise of simplifying the preparation process of the composite polymer electrolyte, it effectively simplifies the preparation process of lithium-ion batteries and reduces the manufacturing cost of lithium-ion batteries, showing broad application prospects. Description of the Drawings

[0023] Figure 1 is a schematic diagram of the principle for preparing the covalent organic framework composite polymer electrolyte in this application; Figure 2 is the infrared spectrum of the covalent organic framework composite polymer electrolyte prepared in Example 1 of this application at a wavelength of 1100 - 1000 cm -1 ; Figure 3 is the infrared spectrum of the covalent organic framework composite polymer electrolyte prepared in Example 1 of this application at a wavelength of 1740 - 1580 cm -1 ; Figure 4 is the conductivity and lithium ion transference number of the covalent organic framework composite polymer electrolytes prepared in Example 1 and Comparative Examples 1, 2, and 3 of this application at room temperature; Figure 5 is a bar chart of the electrochemical stability window of the covalent organic framework composite polymer electrolytes prepared in Example 1 and Comparative Examples 1, 2, and 3 of this application; Figure 6It is the voltage-time graph of the Li-Li symmetric battery assembled with the covalent organic framework composite polymer electrolyte prepared in Example 1 and Comparative Example 1 of the present application under constant current charge and discharge cycling; Figure 7 It is the cycling performance of the lithium-ion full battery (Li||LFP soft-pack battery) assembled with the covalent organic framework composite polymer electrolyte prepared in Example 1 and Comparative Example 1 of the present application at a temperature of 35 °C, a test voltage of 2.5 - 4.2 V, and a 1C rate. Detailed implementation manners

[0024] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] In the description of the present application, it should be understood that the term "and / or" is an association relationship describing associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In this article, the symbol " / " represents an "or" relationship between associated objects. For example, A / B represents A or B.

[0026] In the description of the embodiments of the present application, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific manner.

[0027] In the description of the embodiments of the present application, unless otherwise specified, the meaning of "a plurality" refers to two or more.

[0028] The present application provides a method for preparing a covalent organic framework composite polymer electrolyte, including the following steps: Mix an amino monomer, an aldehyde monomer, a lithium salt, a polymer monomer and a Lewis acid catalyst to obtain an electrolyte precursor solution; perform an in-situ reaction to achieve an in-situ orthogonal polymerization of the reaction of synthesizing a covalent organic framework from the above-mentioned amino monomer and the above-mentioned aldehyde monomer and the polymerization reaction of the above-mentioned polymer monomer, that is, obtain the above-mentioned covalent organic framework composite polymer electrolyte.

[0029] In this application, an amino monomer and an aldehyde monomer for synthesizing a covalent organic framework are dissolved in a suitable polymer monomer, and a suitable Lewis acid catalyst is selected. Under the action of the Lewis acid catalyst, while the amino monomer and the aldehyde monomer synthesize a covalent organic framework with a porous structure, the polymer monomer undergoes a polymerization reaction in the pores of the covalent organic framework under the action of the catalyst, enabling the polymer chains to be directionally generated in the pores, thus realizing the in-situ orthogonal polymerization of the synthesis of the covalent organic framework and the polymerization of the polymer monomer. The above in-situ orthogonal polymerization method not only ensures the uniform dispersion of the covalent organic framework but also maximizes the entanglement between the covalent organic framework and the polymer. By fully leveraging the advantages of the porous structure of the covalent organic framework, the polymer chains grow directionally in the pores of the covalent organic framework, forming regular migration paths, thereby significantly reducing the lithium-ion transport resistance, effectively lowering the migration activation energy, remarkably accelerating the lithium-ion transport rate, greatly enhancing the electrochemical performance of the composite polymer electrolyte, and reducing the manufacturing cost.

[0030] In some embodiments, the above amino monomer is one or more of 1,3,5-tris(4-aminophenyl)benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin, tris(4-aminophenyl)amine, and 5'-(4-amino-3,5-difluorophenyl)-3,3'',5,5''-tetrafluoro-[1,1':3',1''-terphenyl]-4,4''-diamine.

[0031] In some embodiments, the above aldehyde monomer is one or more of terephthalaldehyde, 2,3,5,6-tetrafluoroterephthalaldehyde, 2,5-dimethoxybenzene-1,4-dicarbaldehyde, 2,5-dihydroxyterephthalaldehyde, 1,4-dialdehyde-2,5-divinylbenzene, and 2,2'-bipyridine-5,5'-dicarbaldehyde.

[0032] In some embodiments, the mass ratio of the above amino monomer to the aldehyde monomer is 1:(0.5 - 2).

[0033] In a specific embodiment of this application, the chemical structure schematic diagram of the covalent organic framework synthesized from the amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and the aldehyde monomer 2,3,5,6-tetrafluoroterephthalaldehyde is shown in Formula (I):

[0034] Formula (I).

[0035] In some embodiments, the above polymer monomers are one or more of trimethylene carbonate, propylene oxide, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, and trioxymethylene. It can be understood that the polymerization reaction of the above polymer monomers can be homopolymerization or copolymerization of multiple polymer monomers.

[0036] In some embodiments, the total mass of the above amino monomer and the above aldehyde monomer accounts for 2% to 15% of the mass of the above polymer monomer. When too much covalent organic framework synthesized from the amino monomer and the aldehyde monomer affects the electrochemical performance of the composite polymer electrolyte, resulting in performance degradation.

[0037] In some embodiments, the above Lewis acid catalyst is one or more of boron trifluoride diethyl ether, boron trifluoride tetrahydrofuran, scandium trifluoromethanesulfonate, yttrium trifluoromethanesulfonate, stannous octoate, aluminum chloride, and antimony trichloride.

[0038] In some embodiments, the dosage of the above Lewis acid catalyst is 0.2% to 3% of the total mass of the above amino monomer, aldehyde monomer, and polymer monomer.

[0039] In some embodiments, the above lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium nitrate, and lithium iodide.

[0040] In some embodiments, the mass percentage of the lithium salt in the above electrolyte precursor solution is 2% to 50%.

[0041] In some embodiments, the temperature of the above in-situ polymerization reaction is 0°C to 40°C, and the time of the in-situ polymerization reaction is 12 h to 72 h.

[0042] By rationally designing the catalyst and the structures of the amino monomer, aldehyde monomer, and polymer monomer, the present application realizes the homogeneous room-temperature synthesis of covalent organic frameworks in the polymer monomer. After the covalent organic framework forms an ordered porous structure, under the action of the catalyst, the polymer monomer undergoes a polymerization reaction within the pores of the covalent organic framework, enabling the polymer chains to grow directionally in the pores. Compared with the traditional preparation method of composite polymer electrolytes, the unique strategy of in-situ orthogonal polymerization of the synthesis reaction of covalent organic frameworks and the polymerization reaction of polymer monomers adopted in the present application effectively solves the problem of uneven dispersion of covalent organic frameworks in polymers, significantly improves the dispersion of covalent organic frameworks in polymers, and realizes the directional polymerization of polymer monomers within the pores by virtue of its long-range ordered pore structure. The preparation method provided by the present application simplifies the preparation process of covalent organic framework composite polymer electrolytes, shortens the preparation cycle, reduces the manufacturing cost, and at the same time greatly improves the lithium-ion transference number and ionic conductivity of covalent organic framework composite polymer electrolytes, enhancing their electrochemical performance. That is, the present application provides a method for efficiently preparing high-performance covalent organic framework composite polymer electrolytes.

[0043] On the other hand, the present application also provides a covalent organic framework composite polymer electrolyte prepared by the above preparation method. The covalent organic framework composite polymer electrolyte prepared by the present application has a high ionic conductivity. At 30 °C, the conductivity can reach 1.05 mS / cm, the lithium-ion transference number can reach 0.81, and the electrochemical stability window is 5.3 V. The high ionic conductivity and lithium-ion transference number can accelerate the ion transport efficiency in the electrolyte and greatly reduce the concentration polarization of lithium ions in the electrolyte, can be adapted to high-voltage cathode materials, and at the same time be compatible with metal lithium anode materials, and is suitable for use as an electrolyte of lithium-ion batteries.

[0044] Based on this, the present application also provides a lithium-ion battery comprising the above covalent organic framework composite polymer electrolyte.

[0045] On the other hand, the present application also provides a preparation method of a lithium-ion battery, comprising the following steps: (1) Mix an amino monomer, an aldehyde monomer, a lithium salt, a polymer monomer, and a Lewis acid catalyst to obtain an electrolyte precursor solution; (2) Apply the above electrolyte precursor solution on the surface of a separator, and assemble a lithium-ion battery comprising the separator, and conduct an in-situ reaction to realize the in-situ orthogonal preparation of the synthesis of covalent organic frameworks and the polymerization of polymer monomers, thereby preparing a lithium-ion battery.

[0046] In some embodiments, the assembly of the lithium-ion battery including the separator means that after stacking the positive electrode case, the positive electrode, and the separator in sequence, the above-mentioned electrolyte precursor solution is dropped in, and then the negative electrode, the gasket, the shrapnel, and the negative electrode case are covered in sequence, and the battery is sealed for in-situ reaction. In some embodiments, the above-mentioned positive electrode can be, but is not limited to, lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganate ternary positive electrode material or lithium nickel cobalt aluminate ternary positive electrode material. The above-mentioned negative electrode can be metallic lithium.

[0047] In some embodiments, the above-mentioned separator can be, but is not limited to, one or more of a cellulose separator, a glass fiber separator, and a polyethylene terephthalate separator.

[0048] This application adopts an in-situ orthogonal preparation strategy for the synthesis of covalent organic frameworks and the polymerization of polymer monomers, enabling the preparation of composite polymer electrolytes during the battery assembly process without introducing additional battery preparation steps, and being able to adapt to current lithium-ion battery preparation methods. The preparation method of the composite polymer electrolyte and the lithium-ion battery preparation method provided by this application are fully compatible with existing battery processes. On the premise of simplifying the preparation process of the composite polymer electrolyte, the preparation process of the lithium-ion battery is simplified and the manufacturing cost of the lithium-ion battery is reduced, having broad application prospects.

[0049] It should be understood that materials with the same or similar types, models, qualities, properties, or functions as the reagents and instruments used in the following embodiments can all be used to implement this application. The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can all be obtained from commercial channels unless otherwise specified.

[0050] The following are examples: Example 1 This example provides a method for preparing a covalent organic framework composite polymer electrolyte, as Figure 1 shown, including the following steps: (1) Dissolve 0.014 g of the amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 0.5 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 0.012 g of the aldehyde monomer 2,3,5,6-tetrafluorobenzaldehyde in 1 g of the polymer monomer tetrahydrofuran, and then add 0.015 g of the Lewis acid catalyst boron trifluoride tetrahydrofuran, and stir evenly at room temperature for 1 min to obtain an electrolyte precursor solution.

[0051] (2) React the above electrolyte precursor solution at room temperature (25 °C) for 24 h. Under the action of a Lewis acid catalyst, the Schiff base reaction of the amino monomer and the aldehyde monomer to synthesize the covalent organic framework proceeds rapidly, while the polymer monomer slowly polymerizes, realizing the in-situ orthogonal preparation of the synthesis of the covalent organic framework and the polymerization of the polymer monomer, and obtaining a covalent organic framework composite polymer electrolyte. Among them, the chemical structure schematic diagram of the covalent organic framework is shown in Formula (I):

[0052] Formula (I).

[0053] Perform Fourier transform infrared spectroscopy characterization on the prepared covalent organic framework composite polymer electrolyte, and the results are as Figure 2 、 Figure 3 shown.

[0054] Figure 2 The infrared spectrum of the covalent organic framework composite polymer electrolyte prepared in this example at a wavelength of 1000-1100 cm -1 is shown. It can be seen that there is a displacement of the stretching vibration characteristic peak of the ether oxygen bond when THF is converted to PTHF, which proves the polymerization of THF monomers. Figure 3 The infrared spectrum of the covalent organic framework composite polymer electrolyte prepared in this example at a wavelength of 1580-1740 cm -1 is shown. It can be seen that the intensity of the characteristic absorption peak of the C=N group changes with time, which indicates that the amino monomer and the aldehyde monomer react to form C=N, proving the synthesis of COF.

[0055] Test the performance of the prepared covalent organic framework composite polymer electrolyte: a1. Ionic conductivity: Use the electrochemical impedance (EIS) method to test the ionic conductivity of the electrolyte. Specifically, assemble a stainless steel symmetric battery based on the in-situ orthogonal prepared covalent organic framework composite polymer electrolyte and use an electrochemical workstation for testing. Among them, the EIS frequency range is 10 MHz to 10 Hz, and the test data in the temperature range of 30 °C to 80 °C is collected and recorded every 10 °C. Calculate the ionic conductivity through the following formula: .

[0056] σ is the ionic conductivity of the electrolyte, L is the thickness of the electrolyte, S is the effective contact area between the stainless steel and the electrolyte, R b is the impedance.

[0057] a2. Lithium ion transference number: Based on the in-situ orthogonal preparation of a covalent organic framework composite polymer electrolyte to assemble a lithium symmetric battery, the lithium deposition-stripping behavior and lithium ion transference number ( were tested at a temperature of 60 °C. The battery was polarized at a polarization voltage of 10 mV ( to determine the initial current ( ) and the steady-state current ( ) until the current reached stability (10000 s), and the interfacial resistance before polarization ( ) and after polarization ( ) was tested. The lithium ion transference number was calculated by the following formula: .

[0058] a3. Oxidation voltage: The linear voltammetry scanning method was used to test the oxidation voltage of the electrolyte. Specifically, a lithium / electrolyte / stainless steel battery was assembled based on the in-situ orthogonal preparation of a covalent organic framework composite polymer electrolyte and tested using an electrochemical workstation. At a temperature of 60 °C and a scanning rate of 0.1 mV / s, the electrochemical stability of the lithium / electrolyte / stainless steel battery was tested in the range of 0 - 7 V. The voltage value at which the oxidation current rapidly increased was the oxidation voltage of the electrolyte.

[0059] The test results showed (as shown in Figure 4 , Figure 5 ) that the conductivity of the covalent organic framework composite polymer electrolyte could reach 1.05 mS / cm at 35 °C, the lithium ion transference number was 0.81, and the oxidation voltage was 5.3 V.

[0060] The application performance of the prepared covalent organic framework composite polymer electrolyte was tested. Based on this, this example also provided a preparation method for a polymer solid-state battery (lithium-lithium symmetric battery), including the following steps: (1) Dissolve 0.014 g of the amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 0.5 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 0.012 g of the aldehyde monomer 2,3,5,6-tetrafluorobenzaldehyde in 1 g of the polymer monomer tetrahydrofuran, and then add 0.015 g of the Lewis acid catalyst boron trifluoride tetrahydrofuran and stir evenly at room temperature for 1 min to prepare an electrolyte precursor solution.

[0061] (2) Drop the electrolyte precursor solution prepared in step (1) onto the separator. Then stack the negative electrode case, steel sheet, negative electrode (lithium sheet), and the above-mentioned separator in sequence, drop the electrolyte precursor solution prepared in step (1), then cover the positive electrode (lithium sheet), steel sheet, shrapnel, and positive electrode case in sequence, and encapsulate the battery. Place it under the condition of 25 °C and react for 24 h. The Schiff base reaction for synthesizing covalent organic frameworks from amino monomers and aldehyde monomers proceeds rapidly, while the polymer monomers slowly polymerize, realizing the in-situ orthogonal preparation of covalent organic framework synthesis and polymer monomer polymerization, obtaining a separator containing a covalent organic framework composite polymer electrolyte (polymer@COF), and assembling to obtain a polymer solid-state battery, that is, a lithium-lithium symmetric battery, simply referred to as a Li / polymer@COF / Li battery.

[0062] This example also provides a preparation method for a polymer solid-state battery (Li||LFP soft-pack battery), including the following steps: (1) Dissolve 0.014 g of amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 0.5 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 0.012 g of aldehyde monomer 2,3,5,6-tetrafluorobenzaldehyde in 1 g of polymer monomer tetrahydrofuran, then add 0.015 g of Lewis acid catalyst boron trifluoride tetrahydrofuran, and stir evenly at room temperature for 1 min to prepare an electrolyte precursor solution.

[0063] (2) Plastic-seal the lithium metal negative electrode, separator, and lithium iron phosphate positive electrode sheet with an aluminum foil plastic film, and pour the above-mentioned electrolyte precursor solution. After vacuum encapsulation, a soft-pack battery is obtained. Place it under the condition of 25 °C and react for 24 h. The Schiff base reaction for synthesizing covalent organic frameworks from amino monomers and aldehyde monomers proceeds rapidly, while the polymer monomers slowly polymerize, realizing the in-situ orthogonal preparation of covalent organic framework synthesis and polymer monomer polymerization, obtaining a separator containing a covalent organic framework composite polymer electrolyte (polymer@COF), and assembling to obtain a polymer solid-state battery, that is, a Li||LFP soft-pack battery, simply referred to as a Li / polymer@COF / LFP battery.

[0064] Test the cycle stability of the assembled lithium-lithium symmetric battery and Li||LFP soft-pack battery: b1. Lithium-lithium symmetric battery: Test the cycle performance of the Li / polymer@COF / Li battery under the conditions of a temperature of 35 °C, a current density of 0.5 mA / cm 2 , and a specific capacity of 0.5 mAh / cm 2 .

[0065] b2. Li||LFP soft-pack battery: Test the cycle performance of the Li / polymer@COF / LFP battery under the conditions of a temperature of 35 °C, a test voltage of 2.5 - 4.2 V, and a 1C rate.

[0066] Comparative Example 1 The difference from Example 1 is that only the polymer monomers are polymerized to prepare a pure polymer electrolyte. The specific steps are as follows: (1) Dissolve 0.5 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1 g of the polymer monomer tetrahydrofuran, then add 0.015 g of the Lewis acid catalyst boron trifluoride tetrahydrofuran, and stir evenly at room temperature for 1 min to obtain a polymer monomer precursor solution.

[0067] (2) React the above precursor solution at 25 °C for 24 h to complete the polymerization reaction of the polymer monomers and prepare a pure polymer electrolyte.

[0068] The performance of the pure polymer electrolyte prepared in this comparative example was tested according to the method provided in Example 1. The test results show that ( Figure 4 、 Figure 5 ) the conductivity of this pure polymer electrolyte at 35 °C is 0.061 mS / cm, the lithium ion transference number is 0.32, and the oxidation voltage is 5.06 V.

[0069] The application performance of the pure polymer electrolyte prepared in this comparative example was tested according to the method provided in Example 1.

[0070] Figure 6 Shown are the voltage-time graphs of the polymer solid-state batteries (lithium-lithium symmetric batteries) assembled in Example 1 and Comparative Example 1 under the conditions of a temperature of 35 °C, a current density of 0.5 mA / cm 2 , and a specific capacity of 0.5 mAh / cm 2 under constant current charge-discharge cycling. It can be seen that the lithium-lithium symmetric battery assembled in Example 1 can stably cycle for more than 250 h at a smaller polarization voltage, and there is no obvious increase in voltage polarization; the lithium-lithium symmetric battery assembled in Comparative Example 1 shows an obvious increase in polarization voltage after 48 h of cycling. This shows that the lithium-lithium symmetric battery assembled with the covalent organic framework composite polymer electrolyte prepared in Example 1 has a lower polarization voltage and longer cycle stability, and good electrolyte interface stability.

[0071] Figure 7The cyclic performance of the polymer solid-state battery (Li||LFP soft-pack battery) assembled in Example 1 and Comparative Example 1 is shown at a temperature of 35 °C, a test voltage of 2.5 - 4.2 V, and a 1C rate. It can be seen that the initial discharge capacity of the Li||LFP soft-pack battery assembled in Example 1 reaches 108 mAh / g, the Coulombic efficiency is 99.56%, and the capacity retention rate is 91% after 600 cycles, showing excellent cyclic stability; while the battery capacity of the Li||LFP soft-pack battery assembled in Comparative Example 1 drops sharply at about 50 cycles, the Coulombic efficiency increases sharply, and the battery fails due to overcharging.

[0072] Comparative Example 2 The difference from Example 1 is that the amino monomer and aldehyde monovalent are first synthesized to obtain a covalent organic framework, and then it is directly loaded with polymer monomers for in-situ polymerization of the monomers to prepare a composite polymer electrolyte. The specific steps are as follows: (1) Dissolve 0.5 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1 g of the polymer monomer tetrahydrofuran, then add 0.015 g of the Lewis acid catalyst boron trifluoride tetrahydrofuran, and stir evenly at room temperature for 1 min to obtain a polymer monomer precursor solution.

[0073] (2) By the solvothermal method, ultrasonically dissolve 0.014 g of the amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 20.012 g of the aldehyde monomer 2,3,5,6-tetrafluorobenzaldehyde in a mixed solvent composed of 0.5 mL of 1,4-dioxane and 0.5 mL of mesitylene in a volume ratio of 1:1, then freeze-dry in a vacuum environment of 0.1 MPa in a liquid nitrogen bath for 0.5 h, and after thawing, heat up to 120 °C and react for 72 h. After drying and activation treatment, a covalent organic framework is synthesized.

[0074] (3) Mix the polymer monomer precursor solution prepared in step (1) and the covalent organic framework synthesized in step (2) and react at 25 °C for 24 h to complete the polymerization reaction of the polymer monomers and prepare a composite polymer electrolyte.

[0075] The performance of the composite polymer electrolyte prepared in this comparative example was tested according to the method provided in Example 1. The test results show ( Figure 4 、 Figure 5 ) that the conductivity of this composite polymer electrolyte at 35 °C is 0.081 mS / cm, the lithium ion transference number is 0.68, and the oxidation voltage is 5.2 V.

[0076] Comparative Example 3 The difference from Example 1 is that this comparative example is a traditional method for preparing a composite polymer electrolyte. A covalent organic framework is synthesized by reacting an amino monomer and an aldehyde monovalent monomer, and a monomer polymerization product is obtained by polymerizing a polymer monomer. Then, the covalent organic framework and the monomer polymerization product are blended to prepare the composite polymer electrolyte. The specific steps are as follows: (1) Dissolve 0.5 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 5 mL of acetonitrile and stir and mix evenly at room temperature for 12 h to synthesize a poly(tetrahydrofuran) solution.

[0077] (2) By solvothermal method, ultrasonically dissolve 0.014 g of the amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 20.012 g of the aldehyde monomer 2,3,5,6-tetrafluorobenzaldehyde in a mixed solvent composed of 0.5 mL of 1,4-dioxane and 0.5 mL of mesitylene in a volume ratio of 1:1. Then, freeze-dry in a vacuum environment of 0.1 MPa in a liquid nitrogen bath for 0.5 h. After thawing, raise the temperature to 120 °C and react for 72 h. After drying and activation treatment, synthesize the covalent organic framework.

[0078] (3) Physically mix the poly(tetrahydrofuran) solution synthesized in step (1) and the covalent organic framework synthesized in step (2) to prepare the composite polymer electrolyte.

[0079] Test the performance of the composite polymer electrolyte prepared in this comparative example according to the method provided in Example 1. The test results show ( Figure 4 、 Figure 5 ) that the conductivity of this composite polymer electrolyte at 35 °C is 0.0079 mS / cm, the lithium ion transference number is 0.52, and the oxidation voltage is 5.1 V.

[0080] From Figure 4 、 Figure 5 it can be seen that the conductivity and lithium ion transference number of the covalent organic framework composite polymer electrolyte prepared in Example 1 at 35 °C are significantly better than those of Comparative Examples 1-3, which is beneficial to the conduction of ions in the electrolyte and effectively weakens the concentration polarization of lithium ions in the electrolyte. In addition, the covalent organic framework composite polymer electrolyte prepared in Example 1 has a high oxidation voltage and a higher electrochemical stability window.

[0081] Example 2 This example provides a method for preparing a covalent organic framework composite polymer electrolyte, including the following steps: (1) Dissolve 0.16 g of amino monomer 5,10,15,20 - tetra(4 - aminophenyl)-21H,23H - porphyrin, 0.25 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.001 g of lithium iodide (LiI), and 0.1 g of aldehyde monomer methoxybenzene - 1,4 - dialdehyde in 2.5 g of polymer monomers (including 1.2 g of tetrahydrofuran and 1.3 g of 1,3 - dioxolane), then add 0.013 g of Lewis acid catalyst scandium trifluoromethanesulfonate, and stir evenly at room temperature for 1 min to obtain an electrolyte precursor solution.

[0082] (2) React the above - mentioned electrolyte precursor solution at 30 °C for 36 h. Under the action of the Lewis acid catalyst, the Schiff - base reaction between the amino monomer and the aldehyde monomer to synthesize the covalent organic framework proceeds rapidly, and at the same time, the polymer monomers polymerize slowly, realizing the in - situ orthogonal preparation of the synthesis of the covalent organic framework and the polymerization of the polymer monomers, and obtaining a covalent organic framework composite polymer electrolyte.

[0083] Test the performance of the pure polymer electrolyte prepared in this example according to the method provided in Example 1. The test results show that the conductivity of this pure polymer electrolyte at 35 °C is 1.2 mS / cm, the lithium - ion transference number is 0.83, and the oxidation voltage is 4.8 V.

[0084] Example 3 This example provides a preparation method of a covalent organic framework composite polymer electrolyte, including the following steps: (1) Dissolve 0.012 g of amino monomer tris(4 - aminophenyl)amine, 0.28 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.05 g of lithium nitrate (LiNO3), and 0.015 g of aldehyde monomer 2,5 - dihydroxyterephthalaldehyde in 0.8 g of polymer monomer trioxane, then add 0.01 g of Lewis acid catalyst stannous octoate, and stir evenly at room temperature for 2 min to obtain an electrolyte precursor solution.

[0085] (2) React the above - mentioned electrolyte precursor solution at 20 °C for 48 h. Under the action of the Lewis acid catalyst, the Schiff - base reaction between the amino monomer and the aldehyde monomer to synthesize the covalent organic framework proceeds rapidly, and at the same time, the polymer monomers polymerize slowly, realizing the in - situ orthogonal preparation of the synthesis of the covalent organic framework and the polymerization of the polymer monomers, and obtaining a covalent organic framework composite polymer electrolyte.

[0086] Test the performance of the pure polymer electrolyte prepared in this example according to the method provided in Example 1. The test results show that the conductivity of this pure polymer electrolyte at 35 °C is 0.95 mS / cm, the lithium - ion transference number is 0.78, and the oxidation voltage is 4.9 V.

[0087] Example 4 This example provides a method for preparing a covalent organic framework composite polymer electrolyte, which includes the following steps: (1) Dissolve 0.013 g of amino monomer 5'-(4-amino-3,5-difluorophenyl)-3,3''',5,5'''-tetrafluoro-[1,1':3',1''-terphenyl]-4,4'''-diamine, 0.26 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 0.011 g of aldehyde monomer 1,4-dialdehyde-2,5-divinylbenzene in 1.3 g of polymer monomers (including 1.2 g of 1,3-dioxane and 0.1 g of propylene oxide), then add 0.014 g of Lewis acid catalyst yttrium trifluoromethanesulfonate, and stir evenly at room temperature for 1 min to obtain an electrolyte precursor solution.

[0088] (2) React the above electrolyte precursor solution at 28 °C for 30 h. Under the action of the Lewis acid catalyst, the Schiff base reaction of the amino monomer and the aldehyde monomer to synthesize the covalent organic framework proceeds rapidly, while the polymer monomers slowly polymerize, realizing the in-situ orthogonal preparation of the synthesis of the covalent organic framework and the polymerization of the polymer monomers, and obtaining a covalent organic framework composite polymer electrolyte.

[0089] Test the performance of the pure polymer electrolyte prepared in this example according to the method provided in Example 1. The test results show that the conductivity of the pure polymer electrolyte at 35 °C is 0.6 mS / cm, the lithium ion transference number is 0.71, and the oxidation voltage is 4.5 V.

[0090] Example 5 This example provides a method for preparing a covalent organic framework composite polymer electrolyte, which includes the following steps: (1) Dissolve 0.015 g of amino monomer 1,3,5-tris(4-aminophenyl)benzene, 0.6 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 0.009 g of aldehyde monomer 2,2'-bipyridine-5,5'-dialdehyde in 0.5 g of polymer monomer tetrahydrofuran, then add 0.012 g of Lewis acid catalyst aluminum chloride, and stir evenly at room temperature for 1 min to obtain an electrolyte precursor solution.

[0091] (2) React the above electrolyte precursor solution at 35 °C for 12 h. Under the action of the Lewis acid catalyst, the Schiff base reaction of the amino monomer and the aldehyde monomer to synthesize the covalent organic framework proceeds rapidly, while the polymer monomers slowly polymerize, realizing the in-situ orthogonal preparation of the synthesis of the covalent organic framework and the polymerization of the polymer monomers, and obtaining a covalent organic framework composite polymer electrolyte.

[0092] The performance of the pure polymer electrolyte prepared in this example was tested according to the method provided in Example 1. The test results showed that the conductivity of the pure polymer electrolyte at 35 °C was 0.82 mS / cm, the lithium ion transference number was 0.85, and the oxidation voltage was 5.1 V.

[0093] Example 6 This example provides a preparation method of a covalent organic framework composite polymer electrolyte, including the following steps: (1) Dissolve 1.5 g of amino monomer 1,3,5-tris(4-aminophenyl)benzene, 5 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 2.4 g of aldehyde monomer 2,2'-bipyridine-5,5'-dicarboxaldehyde in 30 g of polymer monomer (including 28 g of tetrahydrofuran and 2 g of propylene oxide), then add 0.12 g of Lewis acid catalyst aluminum chloride, and stir evenly at room temperature for 2 min to obtain an electrolyte precursor solution.

[0094] (2) React the above electrolyte precursor solution at 40 °C for 72 h. Under the action of the Lewis acid catalyst, the Schiff base reaction of the amino monomer and the aldehyde monomer to synthesize the covalent organic framework proceeds rapidly, and at the same time the polymer monomer slowly polymerizes, realizing the in-situ orthogonal preparation of the covalent organic framework synthesis and the polymer monomer polymerization, and obtaining a covalent organic framework composite polymer electrolyte.

[0095] The performance of the pure polymer electrolyte prepared in this example was tested according to the method provided in Example 1. The test results showed that the conductivity of the pure polymer electrolyte at 35 °C was 0.65 mS / cm, the lithium ion transference number was 0.67, and the oxidation voltage was 5.2 V.

[0096] Example 7 This example provides a preparation method of a covalent organic framework composite polymer electrolyte, including the following steps: (1) Dissolve 1.5 g of amino monomer 1,3,5-tris(4-aminophenyl)benzene, 5 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 2.4 g of aldehyde monomer 2,2'-bipyridine-5,5'-dicarboxaldehyde in 30 g of propylene oxide, then add 0.12 g of Lewis acid catalyst aluminum chloride, and stir evenly at room temperature for 2 min to obtain an electrolyte precursor solution.

[0097] (2) React the above electrolyte precursor solution at 40 °C for 72 h. Under the action of the Lewis acid catalyst, the Schiff base reaction of the amino monomer and the aldehyde monomer to synthesize the covalent organic framework proceeds rapidly, and at the same time the polymer monomer slowly polymerizes, realizing the in-situ orthogonal preparation of the covalent organic framework synthesis and the polymer monomer polymerization, and obtaining a covalent organic framework composite polymer electrolyte.

[0098] The performance of the covalent organic framework composite polymer electrolyte prepared in this example was tested according to the method provided in Example 1. The test results showed that the ionic conductivity of the covalent organic framework composite polymer electrolyte at 35 °C was 0.32 mS / cm, the lithium ion transference number was 0.72, and the oxidation voltage was 4.3 V. Its ionic conductivity and oxidation voltage were lower than those in Example 6. The reason may be that the solubility of propylene oxide in the amino monomer and aldehyde monomer was poor, which affected the uniform dispersion of the covalent organic framework, and thus affected the electrochemical performance of the composite polymer electrolyte.

[0099] As can be seen from the above examples, in this application, by selecting appropriate Lewis acid catalysts and polymer monomers, the synthesis of covalent organic frameworks from amino monomers and aldehyde monomers and the polymerization reaction of polymer monomers can achieve in-situ orthogonal catalysis under the action of the catalyst. The covalent organic framework composite polymer electrolyte can be obtained through a one-step reaction without the need to additionally add other catalysts, polar solvents or other compounds, and without complex steps such as freeze treatment and casting into films. Compared with the traditional non-in-situ blending method, it has the advantages of simple operation process and short preparation process, and can effectively shorten the preparation cycle of the composite polymer electrolyte. The covalent organic framework composite polymer electrolyte prepared in this application has high ionic conductivity, lithium ion transference number and oxidation potential, showing excellent electrochemical performance. When applied to batteries, it can improve the rate performance and cycle stability of the batteries.

[0100] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of this application, and are not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A method for preparing a covalent organic framework composite polymer electrolyte, characterized in that: The steps include: The amino monomer, the aldehyde monomer, the lithium salt, the polymer monomer and the Lewis acid catalyst are mixed to obtain an electrolyte precursor solution, and an in-situ reaction is performed to obtain the covalent organic framework composite polymer electrolyte.

2. The preparation method according to claim 1, characterized in that: The amino monomer is one or more of 1,3,5-tris(4-aminophenyl)benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin, tris(4-aminophenyl)amine and 5'-(4-amino-3,5-difluorophenyl)-3,3'',5,5''-tetrafluoro-[1,1':3',1''-terphenyl]-4,4''-diamine; and / or, The aldehyde monomer is one or more of terephthalaldehyde, 2,3,5,6-tetrafluorobenzaldehyde, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 2,5-dihydroxyterephthalaldehyde, 1,4-dialdehyde-2,5-divinylbenzene and 2,2'-bipyridine-5,5'-dicarboxaldehyde.

3. The preparation method according to claim 1, characterized in that: The polymer monomer is one or more of trimethylene carbonate, propylene oxide, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane and trioxymethylene.

4. The preparation method according to claim 3, characterized in that: The total mass of the amino monomer and the aldehyde monomer accounts for 2% to 15% of the mass of the polymer monomer.

5. The preparation method according to claim 1, characterized in that: The Lewis acid catalyst is one or more of boron trifluoride ethyl etherate, boron trifluoride tetrahydrofuran, scandium trifluoromethanesulfonate, yttrium trifluoromethanesulfonate, stannous octoate, aluminum chloride and antimony trichloride; Preferably, the Lewis acid catalyst is used in an amount of 0.2% to 3% of the total mass of the amino monomer, the aldehyde monomer and the polymer monomer.

6. The preparation method according to claim 1, characterized in that: The lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium nitrate and lithium iodide.

7. The preparation method according to claim 1, characterized in that: The temperature of the in-situ polymerization reaction is 0° C. to 40° C., and the time of the in-situ polymerization reaction is 12 h to 72 h.

8. A covalent organic framework composite polymer electrolyte prepared by the preparation method according to any one of claims 1 to 7.

9. A lithium ion battery, characterized in that: The invention comprises the covalent organic framework composite polymer electrolyte as claimed in claim 8.

10. A method for preparing a lithium ion battery as claimed in claim 9, characterized in that: The steps include: The amino monomer, aldehyde monomer, lithium salt, polymer monomer and Lewis acid catalyst are mixed to obtain an electrolyte precursor solution; the electrolyte precursor solution is then applied to the surface of the diaphragm, and a lithium ion battery containing the diaphragm is assembled to perform an in-situ reaction to obtain a lithium ion battery.

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