A d-a type two-dimensional covalent organic framework film and a preparation method and application thereof

Abstract

The present application relates to a kind of D-A type two-dimensional covalent organic framework film and its preparation method and application, for electronic compound and electron-accepting compound as monomer, preparation obtains the covalent organic framework COFs containing D-A group;Again, by electrochemical redox film deposition at room temperature, obtains D-A type two-dimensional covalent organic framework film.The present application due to the introduction of D-A type group, gives two-dimensional covalent organic framework film good conductivity, charge transfer rate and redox activity, as lithium ion battery electrode material electrochemical performance is excellent, with good application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithium ion battery electrode materials, and particularly relates to a D-A type two-dimensional covalent organic framework film and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of wearable electronic devices, the market demand for matching flexible energy storage devices is increasing year by year. At present, the most common energy storage device is a lithium ion battery. Due to its high energy density, high working voltage, long cycle life, low self-discharge and other advantages, it has been widely used in various fields. Therefore, in order to meet the huge use demand of the flexible market for energy storage devices, it is urgent to develop flexible electrodes for the assembly of flexible lithium ion batteries.

[0003] Covalent organic frameworks (COFs) are crystalline materials with ordered porous structures formed by light elements such as carbon, nitrogen, oxygen and boron connected by covalent bonds, and thermodynamically controlled reversible polymerization. As a new type of crystalline porous polymer, COFs have the advantages of porosity, light weight, high stability, structure adjustability, etc. The synthesis of COFs can be achieved by pre-structural design to construct monomers or post-synthesis modification of existing frameworks to customize composition and function. This structural flexibility includes controllably adding electroactive groups on the COFs framework, and introducing electroactive parts in the structure will convert COFs into energy-related electroactive materials with great potential. It is crucial to carefully design electroactive COFs materials with a large number of accessible active sites, long cycle life, and low cost and green environmental protection. From previous research and literature reports, it can be found that the functional design of COFs materials is mainly focused on improving the conductivity and redox, and by enhancing the charge transfer rate of the electrode material, the purpose of improving the electrochemical performance is achieved. The electron-donating-accepting (D-A) group is considered as an ideal functional group to improve the charge transfer rate. Therefore, introducing D-A groups into the COFs framework for lithium ion battery electrode materials may help to improve the electrochemical performance. However, the previous D-A type polymers (such as Chemical Society Reviews, 2015, 44(5), 1113-1154, published on 20141016; Advanced Energy Materials, 2017, 7(2), 1601623, published on 20161010, etc.) are mainly used for photoelectric materials, and rarely used in the field of energy storage. The main reason is that while improving the charge transfer, it reduces the conductivity and redox. Therefore, it is necessary to choose a new design strategy to construct functional COFs.

[0004] At present, although there are many studies on the application of COFs-based electrode materials in lithium ion batteries, they are mainly based on the preparation of traditional electrodes, such as patents CN113248707A, CN113903899A, CN113754884A, CN110724166A, CN111446414A, etc., which need to use non-active components such as binders, conductive carbon additives, current collectors, etc. Non-active components are important for the electrical contact and mechanical connection of the electrode, but they still inevitably reduce the energy density of the battery, and may also cause phenomena such as cracking of the electrode sheet, shedding of active materials, etc., or produce side effects (such as decomposition of organic binders), which cannot meet the demand of flexible devices for flexible electrode materials. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a D-A type two-dimensional covalent organic framework film and its preparation method and application, which overcomes the current situation that COFs materials have low conductivity, poor redox property and are generally powder materials.

[0006] The present application provides a D-A type two-dimensional covalent organic framework film, which uses electron-donating compounds and electron-withdrawing compounds as monomers to prepare a covalent organic framework COFs containing D-A groups; and then deposits an electrochemical oxidation-reduction film at room temperature to obtain a D-A type two-dimensional covalent organic framework film.

[0007] The electron-donating compound is 2,3,6,7-tetrakis(4-formylphenyl) tetrathiafulvalene. The chemical formula is as follows:

[0008]

[0009] The electron-withdrawing compound is one or more of 2,6-diaminoanthraquinone, 2,3-diamino naphthalene-1,4-dione, 2,6-diaminoanthracene, and 1,4,5,8-tetraaminoanthraquinone. The chemical formula is as follows:

[0010]

[0011] The present application also provides a preparation method of a D-A type two-dimensional covalent organic framework film, comprising the following steps:

[0012] (1) using electron-donating compounds and electron-withdrawing compounds as monomers to prepare a covalent organic framework COFs containing D-A groups;

[0013] (2) mixing and grinding 21-24 mg of covalent organic framework powder containing D-A groups, 3-6 mg of conductive carbon black, and 3 mg of polytetrafluoroethylene to obtain a clay-like mixture, and using the mixture as a working electrode; using an ITO film as a counter electrode, using Ag / Ag +As a reference electrode, N,N-dimethylformamide DMF is used as an electrolyte, and a two-dimensional covalent organic framework film is formed on an ITO film at-1.0 V by a constant potential method, and then washed to obtain a D-A type two-dimensional covalent organic framework film.

[0014] The preparation process in step (1) is as follows: the electron-donating compound, the electron-withdrawing compound and the solvent are uniformly mixed by ultrasonic, then acetic acid solution is added and transferred to a hydrothermal kettle, sealed and placed in an oven at 120-140 DEG C for 24-72 h, cooled to room temperature, vacuum filtration, washing, Soxhlet extraction and drying to obtain a covalent organic framework COF containing D-A groups.

[0015] The molar ratio of the electron-donating compound to the electron-withdrawing compound is 1:1-2.

[0016] The solvent in the preparation process is trimethylbenzene and N,N-dimethylacetamide.

[0017] The solvent used in the Soxhlet extraction is tetrahydrofuran, the water bath temperature is 80 DEG C, and the extraction time is 24-72 h.

[0018] The DMF in step (2) contains 0.1 mol / L -1 Lithium perchlorate and 0.01 mol / L -1 p-toluenesulfonic acid.

[0019] The step (2) is carried out in a glove box (nitrogen atmosphere).

[0020] The application also provides a D-A type two-dimensional covalent organic framework film in a lithium ion battery.

[0021] Advantages

[0022] (1) The preparation conditions of the application are mild, simple to operate, and have universality, which can greatly expand the application potential of COFs.

[0023] (2) The application introduces D-A groups into the COFs structure, effectively enhances the charge transfer rate of the electrode material, and thus achieves the purpose of improving the electrochemical performance.

[0024] (3) The D-A type two-dimensional covalent organic framework prepared by the application is in the form of a film, which eliminates the electrode pretreatment steps such as slurry preparation and coating.

[0025] (4) The D-A type two-dimensional covalent organic framework film prepared by the application is used for the preparation of lithium ion batteries, and exhibits excellent electrochemical performance, showing great application potential in the field of energy storage. DETAILED DESCRIPTION

[0026] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that after reading the content of the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope defined by the appended claims.

[0027] Example 1

[0028] Preparation of D-A type two-dimensional covalent organic framework powder: 124 mg (0.2 mmol) of 2,3,6,7-tetrakis (4-formylphenyl) tetrathiafulvalene, 54 mg (0.2 mmol) of 1,4,5,8-tetraaminanthraquinone, 2 mL of mesitylene, 0.3 mL of N,N-dimethylacetamide were added into a 10 mL beaker, after ultrasonic mixing, 0.2 mL of 3 mol L -1 acetic acid solution was added and the mixed solution was transferred to a 10 mL hydrothermal kettle, which was sealed and placed in a 120°C oven for reaction for 72 h, cooled to room temperature, vacuum filtration, washed with N,N-dimethylformamide, acetone three times respectively, then the powder was placed in a Soxhlet extractor, the selected solvent was tetrahydrofuran, the temperature was 80°C, and the extraction time was 24 h, and the powder was further dried to obtain the D-A type two-dimensional covalent organic framework powder.

[0029] Preparation of D-A type two-dimensional covalent organic framework film: in a glove box (nitrogen atmosphere), 21 mg of D-A type two-dimensional covalent organic framework powder, 6 mg of Ketjen black, 3 mg of polytetrafluoroethylene were mixed and ground for 5 min to obtain a clay-like mixture, which was lightly pressed onto a platinum mesh as a working electrode, ITO as a counter electrode, Ag / Ag + as a reference electrode, DMF (containing 0.1 mol L -1 of lithium perchlorate and 0.01 mol L -1 of p-toluenesulfonic acid) as electrolyte, a two-dimensional covalent organic framework film was formed on the ITO film by constant potential method at-1.0 V, which was achieved by cathodic reduction to transfer the imine bond to the protonated amine bond and introduce a large number of positive charges to the COFs framework, thereby peeling off the COFs into the electrolyte solution to form highly dispersed large-area nanosheets, then, these COFs nanosheets migrated to the counter electrode under the driving of the electric field and were anodically oxidized to recover the imine bond from the protonated amine bond, thereby the COFs film appeared on the electrode, and the film was further washed with acetonitrile for 3 times to remove the doped electrolyte to obtain the D-A type two-dimensional covalent organic framework film. The obtained D-A type two-dimensional covalent organic framework film was directly applied to the lithium ion battery electrode material, and the discharge capacity was still up to 1050 mAh g -1 after 250 cycles at a current density of 100 mA g -1Further in-situ FTIR, in-situ Raman, non-in-situ XPS and DFT calculation show that the reversible capacity of D-A type two-dimensional covalent organic framework film is mainly due to the participation of benzene ring, C=N, C=O and other groups in lithium storage.

[0030] Example 2

[0031] Preparation of D-A type two-dimensional covalent organic framework powder: 124 mg (0.2 mmol) of 2,3,6,7-tetrakis (4-formylphenyl) tetrathiafulvalene, 48 mg (0.2 mmol) of 2,6-diaminoanthraquinone, 38 mg (0.2 mmol) of 2,3-diaminonaphthalene-1,4-dione, 2 mL of mesitylene, 0.3 mL of N,N-dimethylacetamide were added into a 10 mL beaker, and after ultrasonic mixing, 0.2 mL of 3 mol L -1 acetic acid solution was added and the mixed solution was transferred to a 10 mL hydrothermal kettle, which was sealed and placed in a 120°C oven for reaction for 24 h, cooled to room temperature, vacuum filtered, washed with N,N-dimethylformamide and acetone three times respectively, and then the powder was placed in a Soxhlet extractor for Soxhlet extraction, and tetrahydrofuran was selected as the solvent, the temperature was 80°C, and the extraction time was 36 h. Further drying the powder to obtain the D-A type two-dimensional covalent organic framework powder.

[0032] Preparation of D-A type two-dimensional covalent organic framework film: in a glove box (nitrogen atmosphere), 24 mg of D-A type two-dimensional covalent organic framework powder, 3 mg of Ketjen black, and 3 mg of polytetrafluoroethylene were mixed and ground for 5 min to obtain a clay-like mixture, which was lightly pressed onto a platinum mesh as a working electrode, ITO as a counter electrode, Ag / Ag + as a reference electrode, and DMF (containing 0.1 mol L -1 of lithium perchlorate and 0.01 mol L -1 of p-toluenesulfonic acid) as an electrolyte, a D-A type two-dimensional covalent organic framework film was formed on the ITO film at -1.0 V by constant potential method, and the film was further washed with acetonitrile three times to remove the doped electrolyte, to obtain the D-A type two-dimensional covalent organic framework film. The obtained D-A type two-dimensional covalent organic framework film was directly applied to lithium ion battery electrode material, and after 250 cycles at a current density of 100 mA g -1 , the discharge capacity was still up to 1278 mAh g -1 .

[0033] Example 3

[0034] Preparation of D-A type two-dimensional covalent organic framework powder: 124 mg (0.2 mmol) of 2,3,6,7-tetrakis(4-formylphenyl) tetrathiafulvalene, 38 mg (0.2 mmol) of 2,3-diaminonaphthalene-1,4-dione, 42 mg (0.2 mmol) of 2,6-diaminoanthracene, 2 mL of mesitylene, 0.3 mL of N,N-dimethylacetamide were added into a 10 mL beaker, after ultrasonic mixing, 0.2 mL of 3 mol / L acetic acid solution was added, and the mixed solution was transferred to a 10 mL hydrothermal kettle, sealed and placed in a 120°C oven for reaction for 36 h, cooled to room temperature, vacuum filtration, washed with N,N-dimethylformamide, acetone respectively three times, then the powder was placed in a Soxhlet extractor, the selected solvent was tetrahydrofuran, the temperature was 80°C, and the extraction time was 72 h, and the powder was further dried to obtain the D-A type two-dimensional covalent organic framework powder. -1 Preparation of D-A type two-dimensional covalent organic framework powder: 124 mg (0.2 mmol) of 2,3,6,7-tetrakis(4-formylphenyl) tetrathiafulvalene, 38 mg (0.2 mmol) of 2,3-diaminonaphthalene-1,4-dione, 42 mg (0.2 mmol) of 2,6-diaminoanthracene, 2 mL of mesitylene, 0.3 mL of N,N-dimethylacetamide were added into a 10 mL beaker, after ultrasonic mixing, 0.2 mL of 3 mol / L acetic acid solution was added, and the mixed solution was transferred to a 10 mL hydrothermal kettle, sealed and placed in a 120°C oven for reaction for 36 h, cooled to room temperature, vacuum filtration, washed with N,N-dimethylformamide, acetone respectively three times, then the powder was placed in a Soxhlet extractor, the selected solvent was tetrahydrofuran, the temperature was 80°C, and the extraction time was 72 h, and the powder was further dried to obtain the D-A type two-dimensional covalent organic framework powder.

[0035] Preparation of D-A type two-dimensional covalent organic framework film: In a glove box (nitrogen atmosphere), 22 mg of D-A type two-dimensional covalent organic framework powder, 5 mg of Ketjen black, 3 mg of polytetrafluoroethylene were mixed and ground for 5 min to obtain a clay-like mixture, and the mixture was lightly pressed onto a platinum net as a working electrode, ITO as a counter electrode, Ag / Ag + as a reference electrode, DMF (containing 0.1 mol / L -1 lithium perchlorate and 0.01 mol / L -1 p-toluenesulfonic acid) as electrolyte, a two-dimensional covalent organic framework film was formed on the ITO film by constant potential method at-1.0 V, and the film was further washed with acetonitrile three times to remove the doped electrolyte, to obtain the D-A type two-dimensional covalent organic framework film. The obtained D-A type two-dimensional covalent organic framework film was directly applied to lithium ion battery electrode material, and after 250 cycles at a current density of 100 mAg -1 , the discharge capacity was still up to 980 mAh / g -1 .

[0036] Example 4

[0037] Preparation of D-A type two-dimensional covalent organic framework powder: 124 mg (0.2 mmol) of 2,3,6,7-tetrakis(4-formylphenyl) tetrathiafulvalene, 38 mg (0.2 mmol) of 2,3-diaminonaphthalene-1,4-dione, 42 mg (0.2 mmol) of 2,6-diaminoanthracene, 2 mL of mesitylene, 0.3 mL of N,N-dimethylacetamide were added into a 10 mL beaker, after ultrasonic mixing, 0.2 mL of 3 mol / L acetic acid solution was added, and the mixed solution was transferred to a 10 mL hydrothermal kettle, sealed and placed in a 120°C oven for reaction for 36 h, cooled to room temperature, vacuum filtration, washed with N,N-dimethylformamide, acetone respectively three times, then the powder was placed in a Soxhlet extractor, the selected solvent was tetrahydrofuran, the temperature was 80°C, and the extraction time was 72 h, and the powder was further dried to obtain the D-A type two-dimensional covalent organic framework powder. -1The mixture solution was transferred into a 10 mL hydrothermal kettle, sealed and placed in a 120 °C oven for reaction for 72 h, cooled to room temperature, vacuum filtration, washed with N,N-dimethylformamide, acetone three times respectively, and then the powder was placed in a Soxhlet extractor for Soxhlet extraction, the selected solvent was tetrahydrofuran, the temperature was 80 °C, and the extraction time was 24 h. The powder was further dried to obtain the D-A type two-dimensional covalent organic framework powder.

[0038] Preparation of the D-A type two-dimensional covalent organic framework film: In a glove box (nitrogen atmosphere), 21 mg of the D-A type two-dimensional covalent organic framework powder, 6 mg of Ketjen black and 3 mg of polytetrafluoroethylene were mixed and ground for 5 min to obtain a clay-like mixture, which was lightly pressed onto a platinum mesh as a working electrode, ITO as a counter electrode, Ag / Ag + as a reference electrode, and DMF (containing 0.1 mol L -1 of lithium perchlorate and 0.01 mol L -1 of p-toluenesulfonic acid) as an electrolyte. A two-dimensional covalent organic framework film was formed on the ITO film at -1.0 V by constant potential method. The film was further washed with acetonitrile three times to remove the doped electrolyte to obtain the D-A type two-dimensional covalent organic framework film. The obtained D-A type two-dimensional covalent organic framework film was directly applied to the lithium ion battery electrode material. After 250 cycles at a current density of 100 mA g -1 , the discharge capacity was still as high as 1215 mAh g -1 .

[0039] Example 5

[0040] Preparation of the D-A type two-dimensional covalent organic framework powder: 124 mg (0.2 mmol) of 2,3,6,7-tetrakis (4-formylphenyl) tetrathiafulvalene, 75 mg (0.4 mmol) of 2,3-diaminonaphthalene-1,4-dione, 2 mL of mesitylene and 0.3 mL of N,N-dimethylacetamide were added into a 10 mL beaker, ultrasonically mixed until uniform, and then 0.2 mL of 3 mol L -1 acetic acid solution was added, and the mixed solution was transferred into a 10 mL hydrothermal kettle, sealed and placed in a 120 °C oven for reaction for 72 h, cooled to room temperature, vacuum filtration, washed with N,N-dimethylformamide, acetone three times respectively, and then the powder was placed in a Soxhlet extractor for Soxhlet extraction, the selected solvent was tetrahydrofuran, the temperature was 80 °C, and the extraction time was 36 h. The powder was further dried to obtain the D-A type two-dimensional covalent organic framework powder.

[0041] Preparation of DA-type two-dimensional covalent organic framework membrane: In a glove box (nitrogen atmosphere), 24 mg of DA-type two-dimensional covalent organic framework powder, 3 mg of Ketjen black, and 3 mg of polytetrafluoroethylene were mixed and ground for 5 min to obtain a clay-like mixture, which was then lightly pressed onto a platinum mesh as a working electrode, ITO as a counter electrode, and Ag / Ag as a substrate. + As the reference electrode, DMF (containing 0.1 mol L -1 Lithium perchlorate and 0.01 mol L -1 A two-dimensional covalent organic skeleton membrane was formed on an ITO film by a constant potential method at -1.0 V using p-toluenesulfonic acid as the electrolyte. The membrane was then washed three times with acetonitrile to remove the doped electrolyte, resulting in a DA-type two-dimensional covalent organic skeleton membrane. The obtained DA-type two-dimensional covalent organic skeleton membrane was directly applied to lithium-ion battery electrode materials and the membrane was heated to 100 mA g -1 After 250 cycles, the discharge capacity can still reach 1162mAh g -1 .

Claims

1. A method for preparing a D-A type two-dimensional covalent organic framework film, comprising the following steps: (1) using an electron-donating compound and an electron-accepting compound as monomers to prepare a covalent organic framework (COF) containing a D-A group; wherein, the electron-donating compound is 2, 3, 6, 7-tetrakis (4-formylphenyl) tetrathiafulvalene; and the electron-accepting compound is one or more of 2, 6-diaminoanthraquinone, 2, 3-diaminonaphthalene-1, 4-dione, 2, 6-diaminoanthracene and 1, 4, 5, 8-tetraaminoanthraquinone; (2) 21-24 mg of covalent organic framework powder containing D-A groups, 3-6 mg of conductive carbon black, and 3 mg of polytetrafluoroethylene were mixed and milled to obtain a clay-like mixture, and the mixture was used as a working electrode; an ITO film was used as a counter electrode, an Ag / Ag + reference electrode, and N,N-dimethylformamide DMF was used as an electrolyte, a two-dimensional covalent organic framework film was formed on the ITO film at -1.0 V by a constant potential method, and the film was washed to obtain a D-A type two-dimensional covalent organic framework film.

2. The method of claim 1, wherein: the preparation process in step (1) is as follows: the electron-donating compound, the electron-accepting compound and a solvent are uniformly mixed by ultrasonic, then acetic acid solution is added and transferred to an autoclave, which is sealed and placed in an oven at 120-140 ℃ for 24-72 h, cooled to room temperature, vacuum filtered, washed, then Soxhlet extracted and dried to obtain a covalent organic framework (COF) containing D-A groups.

3. The method of claim 1, wherein: The molar ratio of the electron-donating compound to the electron-accepting compound is 1: 1-2.

4. The method of claim 1, wherein: The solvent used for Soxhlet extraction is tetrahydrofuran, the water bath temperature is 80 ℃, and the extraction time is 24-72 h.

5. The method of claim 1, wherein: The DMF in the step (2) contains 0.1 mol L -1 Lithium perchlorate and 0.01 mol L -1 p-Toluenesulfonic acid.

6. Application of a D-A type two-dimensional covalent organic framework film prepared by the method of claim 1 in a lithium ion battery.

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