Bipolar COF materials based on TAPBA and anthraquinone, their synthesis methods and applications

Abstract

The present invention discloses a bipolar COF material based on TAPBA and anthraquinone, a synthesis method, and applications thereof. The present invention uses a solvothermal method to prepare the bipolar COF material, wherein the repeating structural unit is shown in formula (I). The bipolar COF material of the present invention can be used for a positive electrode of a battery. The COF structure has reversible electrochemical cyclic voltammetry characteristics, a high specific capacity and a charge-discharge platform, and excellent electrochemical cycle stability and charge-discharge stability, and a low electrochemical AC impedance.

Description

Technical Field

[0001] The present invention relates to the field of synthesis of COF materials, in particular to a bipolar COF material based on TAPBA (N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine) and anthraquinone, a synthesis method thereof, and application of the COF material in lithium-ion battery positive electrode materials. Background Art

[0002] The synthesis of covalent organic framework (COF) materials is the focus and difficulty of current research on COF materials. Exploring the synthesis conditions of COF materials and finding their synthesis rules are the ultimate goals of researchers dedicated to studying COF materials. In addition, the application of COF materials after preparation is another important direction of attention. At present, the synthesized COF materials have demonstrated important roles and excellent performance in important fields such as adsorption, electrolysis, catalysis, and luminescence. To this end, preparing COF materials and exploring their applications in real life are important ways to study this type of material in the future.

[0003] In this study, we prepared and characterized a COF material with a unique crystalline structure using TAPBA and anthraquinone as its base monomers via a solvothermal method. Solvent selection and temperature control demonstrate the feasibility of COF preparation based on TAPBA and anthraquinone. This material exhibits excellent electrochemical properties, enabling high specific capacity and a high discharge voltage plateau when used as a battery cathode material. This overcomes the low capacitance limitation of COF materials in battery cathode materials and expands their potential commercial applications in the future. Summary of the Invention

[0004] The present invention aims to provide a bipolar COF material based on TAPBA and anthraquinone, as well as its synthesis method and application. The COF material can be used in battery positive electrodes. The COF structure exhibits reversible electrochemical cyclic voltammetry (CV) characteristics, a high specific capacity, and a high charge-discharge platform. It also exhibits excellent electrochemical cycling and charge-discharge stability, and low electrochemical impedance.

[0005] The technical solutions of the present invention are as follows:

[0006] A bipolar COF material, whose repeating structural unit is shown in formula (I):

[0007]

[0008] The preparation method of the bipolar COF material of the present invention is:

[0009] N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine (abbreviated as TAPBA), bromine-substituted anthraquinone (abbreviated as EK) and an organic solvent are mixed, the reaction system is sealed after vacuum deoxygenation, and placed at 60-160° C. (preferably 120-130° C.) for 12-140 hours (preferably 48-72 hours), and then the reaction mixture is post-treated to obtain the bipolar COF material;

[0010] The molar ratio of TAPBA to EK is 1:1.8 to 2.2, preferably 1:2;

[0011] The organic solvent is selected from one or more solvents such as mesitylene, o-dichlorobenzene, dimethyl sulfoxide, N,N-dimethylformamide, benzyl alcohol, n-butanol, and 1,4-dioxane; preferably, a mixed solvent of mesitylene and 1,4-dioxane in a volume ratio of 1:1;

[0012] The specific post-treatment method is as follows: after the reaction is completed, the reaction mixture is poured into a washing solvent, stirred and washed, and then filtered to obtain a crude product; the crude product is extracted with a purified solvent using a Soxhlet extraction apparatus, and finally dried to obtain the product bipolar COF material;

[0013] Wherein, the washing solvent is selected from one or more solvents such as methanol, petroleum ether, acetone, tetrahydrofuran, etc.;

[0014] The purification solvent is selected from one or more solvents such as methanol, petroleum ether, dichloromethane, chloroform, tetrahydrofuran, N,N-dimethylformamide, etc.;

[0015]

[0016] The bipolar COF material of the present invention can be used as a positive electrode material for lithium batteries. The specific application method is as follows:

[0017] The bipolar COF material was mixed with PVDF (polyvinylidene fluoride) and acetylene black, and after being fully ground, N-methylpyrrolidone was added and the mixture was further ground until a viscous slurry was formed. The mixture was evenly coated on the surface of aluminum foil with a scraper and dried in a vacuum oven at 70°C for 24 hours to prepare an electrode sheet.

[0018] The mass ratio of bipolar COF material, acetylene black and PVDF is 8-4:0.8-1.2:1.2-4, preferably 5:1:4;

[0019] The amount of N-methylpyrrolidone is 1-2% of the total mass of the slurry;

[0020] The obtained electrode sheet can be further prepared into a half-cell for testing electrochemical performance.

[0021] The technical principles of the present invention include:

[0022] Using TAPBA and anthraquinone as COF building blocks, TAPBA provides anion doping (p-doping) while anthraquinone provides cation doping (n-doping). Furthermore, the bipolar nature of this COF material enables both high capacity and high discharge voltage within the same electrode material, resolving the current issue of low voltage and low specific capacity in electrode materials.

[0023] Compared with the existing technology, the present invention has the following beneficial effects:

[0024] (1) The synthesis of the COF material of the present invention solves the technical difficulties in preparing COF using TAPBA and anthraquinone compounds, laying a solid foundation for the future synthesis of COF materials using this type of monomer.

[0025] (2) The present invention adopts a solvent thermal method to prepare a polymer material with a COF structure. The obtained final product powder can be used as a bipolar battery positive electrode material, can achieve reversible charge and discharge, has a higher charge and discharge platform (3.5V), a wider electrochemical window (2-4.3V), a high specific capacity (230mAh / g) and excellent electrochemical charge and discharge stability (2500 times), and has potential application value as a battery positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 : Infrared absorption spectrum of COF prepared in Example 1; wherein 1669cm -1 The absorption at indicates that the amino group and bromine undergo substitution reaction to form a CN bond.

[0027] Figure 2 : Simulation diagrams of the stacking structure of the theoretically prepared product in Example 1 (a, b) and the X-ray diffraction (XRD) spectrum of the prepared COF (c); The structure of the final product was simulated and predicted, and the small-angle diffraction peaks of the XRD diffraction peaks of the obtained product at 2 to 3 positions clearly coincided with the simulation results, which are absorption marks unique to COF materials, fully indicating that the obtained product has a COF crystal form, indicating the certainty of the product structure.

[0028] Figure 3 : Scanning electron microscope (SEM) image of the COF prepared in Example 1.

[0029] Figure 4 : Electrochemical cyclic voltammetry curve of COF prepared in Example 1 (compared to Li + ); Obviously, in the electrochemical cyclic voltammogram, the material exhibits good electrochemical properties, with obvious redox peaks near 2.5 and 3.7 V, which are attributed to the redox of the carbonyl group of anthraquinone and the nitrogen atom of TAPBA, respectively, and a wide voltage range of 2-4.3 V.

[0030] Figure 5 : Electrochemical charge-discharge curves of the COF prepared in Example 1; the charge-discharge voltage platform of the material is consistent with the cyclic voltammetry curve, which is consistent with the bipolar electrochemical characteristics of anthraquinone and TAPBA units. At the same time, it shows a discharge voltage platform of 3.5V and a high specific capacity of up to 230mAh / g.

[0031] Figure 6 : The electrochemical rate performance of the COF prepared in Example 1; the material has good rate performance at different current densities.

[0032] Figure 7 : The electrochemical cycle stability of the COF prepared in Example 1; the material has good cycle stability within the cycle range, and there is no obvious attenuation after 2500 cycles, which basically meets the electrochemical energy storage materials currently used in the market.

[0033] Figure 8 : AC impedance characteristics of the COF prepared in Example 1; its impedance value is relatively low. DETAILED DESCRIPTION

[0034] The present invention is further described below by means of specific examples, but the protection scope of the present invention is not limited thereto.

[0035] In the following examples, the raw materials TAPBA and bromine-substituted anthraquinone were purchased from Bidex Pharmaceuticals with a purity of >99%.

[0036] Example 1

[0037] The synthesis of bipolar COF materials, whose repeating structural units are shown below:

[0038]

[0039] TAPBA (0.95 g, 2 mmol), 2,6-dibromoanthraquinone (1.5 g, 4 mmol), 0.5 mL of mesitylene, and 0.5 mL of 1,4-dioxane were added to a reaction flask, sealed after vacuum deoxygenation, and placed at 120 ° C for 72 h. After the reaction, the reaction mixture was poured into tetrahydrofuran, stirred, washed, and filtered to obtain a crude product; the crude product was extracted with tetrahydrofuran using a Soxhlet extraction apparatus and finally dried to obtain 0.5 g of a bipolar COF material. The structural characterization is shown in FIG. Figure 1-Figure 3 .

[0040] 0.5 g of the bipolar COF material prepared above was mixed with 0.4 g of PVDF and 0.1 g of acetylene black. After thorough grinding, 0.01 mL of N-methylpyrrolidone was added and the mixture was further ground until a viscous slurry was obtained. The mixture was evenly coated on the surface of aluminum foil with a spatula to a thickness of 25 μm and then dried in a vacuum oven at 70°C for 24 h to prepare an electrode sheet.

[0041] The aluminum foil placed in the vacuum oven was cut into circular electrode sheets with a diameter of 1 cm. A half-cell was assembled in a glove box using a lithium metal sheet as the counter electrode, an electrolyte containing 1M LiPF6 (EC / DMC / DEC in a ratio of 1:1:1), and Celgard 2400 as the separator.

[0042] COFs materials have attracted widespread attention due to their specific long-range ordered structure, especially in the field of energy storage. Their large specific surface area, easily modified reaction sites, and regular pore structure make them one of the best choices for developing high-performance lithium battery electrode materials. Most COFs electrode materials reported so far are unipolar, and research on electrode materials with p / n bipolar doping is still scarce. The present invention, based on the structure of aniline derivatives, develops a new COFs material with both p / n dual doping capabilities to obtain lithium-ion batteries with a wide voltage window and high specific capacity, ultimately obtaining a high-energy density battery electrode material, which will provide guidance for the future preparation of high-energy, wide-voltage lithium-ion batteries.

Claims

1. A bipolar COF material, whose repeating structural unit is shown in formula (I):

2. The method for preparing the bipolar COF material according to claim 1, wherein: The preparation method is: N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine, bromine-substituted anthraquinone and an organic solvent are mixed, the reaction system is sealed after vacuum deoxygenation, and placed at 60-160° C. for 12-140 hours, and the reaction mixture is post-treated to obtain the bipolar COF material; The structural formula of N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine and bromine-substituted anthraquinone is as follows:

3. The preparation method according to claim 2, wherein The molar ratio of N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine to bromine-substituted anthraquinone is 1:1.8-2.

2.

4. The preparation method according to claim 3, wherein The molar ratio of N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine and bromine-substituted anthraquinone is 1:

2.

5. The preparation method according to claim 2, wherein The organic solvent is selected from one or more of mesitylene, o-dichlorobenzene, dimethyl sulfoxide, N,N-dimethylformamide, benzyl alcohol, n-butanol, and 1,4-dioxane.

6. The preparation method according to claim 5, wherein The organic solvent is a mixed solvent of mesitylene and 1,4-dioxane in a volume ratio of 1:

1.

7. The preparation method according to claim 2, wherein The reaction temperature is 120-130°C and the reaction time is 48-72h.

8. The preparation method according to claim 2, wherein The post-treatment method is as follows: after the reaction is completed, the reaction mixture is poured into a washing solvent, stirred and washed, and then filtered to obtain a crude product; the crude product is extracted with a purified solvent using a Soxhlet extraction apparatus, and finally dried to obtain the product bipolar COF material; Wherein, the washing solvent is selected from one or more of methanol, petroleum ether, acetone, and tetrahydrofuran; The purification solvent is selected from one or more of methanol, petroleum ether, dichloromethane, chloroform, tetrahydrofuran, and N,N-dimethylformamide.

9. Use of the bipolar COF material as claimed in claim 1 as a positive electrode material for lithium batteries.

10. The use according to claim 9, characterized in that The application method is as follows: The bipolar COF material was mixed with PVDF and acetylene black, and after being fully ground, N-methylpyrrolidone was added and the mixture was further ground until a viscous slurry was obtained. The mixture was evenly coated on the surface of aluminum foil with a scraper and dried in a vacuum oven at 70°C for 24 hours to prepare an electrode sheet. The mass ratio of bipolar COF material, acetylene black, and PVDF is 8 to 4: 0.8～1.2：1.2～4； The amount of N-methylpyrrolidone used is 1-2% of the total mass of the slurry.

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