EG / DT-COF based on EG regulation of micro morphology, and preparation method and application thereof

Abstract

The application discloses an EG / DT-COF based on EG regulation of micro morphology, and a composite covalent organic framework supercapacitor negative material is prepared by using physical grinding method, with diaminoanthraquinone, triformylphloroglucinol and expanded graphite as raw materials, p-toluenesulfonic acid as a catalyst and deionized water as a lubricant. The material has a layered porous structure, and the pore size is 2-50 nm. The material has stability in the range of 20-450 DEG C, and starts to decompose at 445-455 DEG C. The preparation method comprises the following steps: 1, preparation of expanded graphite EG; 2, preparation of EG / DT-COF based on EG regulation of micro morphology. As the application of the negative material in the supercapacitor, the charging and discharging is in the range of-0.3-1V, the specific capacitance is 495-501 F / g when the current density is 1 A / g, and the capacitance retention rate is 93-94.4% after 10000 GCD cycles.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to an EG / DT-COF based on EG-controlled micromorphology, its preparation method, and its applications. Background Technology

[0002] MOF (Metal-Organic Facility) materials are used as electrode materials in supercapacitors due to their high specific capacitance and high power density. However, the instability of MOF materials prevents these MOF-based supercapacitors from maintaining stable performance over long periods. In contrast, novel covalent organic framework (COF) materials can address the issue of low stability. However, because these COF materials do not contain metal elements and are composed of non-metals, they suffer from low conductivity, resulting in electrochemical performance that fails to meet application requirements.

[0003] To solve this problem, two methods are usually used:

[0004] 1. Improve ion transport rate by controlling the microstructure of COF and increasing the specific surface area of ​​the material;

[0005] 2. Increase the number of active adsorption sites on the COF surface and improve the ion exchange rate.

[0006] For example, existing technology 1 (Li C, Yang J, Pachfule P, Li S, Ye MY, Schmidt J, Thomas A. Ultralight covalent organic framework / graphene aerogels with hierarchical porosity. Nat Commun. 2020 Sep 18; 11(1):4712.) uses graphene oxide to control the growth of COF. COF is grown in situ along the surface of two-dimensional graphene sheets using a hydrothermal method, stacked in a 3D manner, to synthesize COF / rGO aerogel materials. These materials provide a specific capacitance of 269 F / g at a current density of 0.5 A / g and retain 96% of their capacitance after 5000 cycles. This technology transforms the originally hollow tubular COF structure into a 3D sponge-like structure by adding graphene oxide, and the COF grows on the surface of graphene oxide. Although this technical solution achieves the control of the microstructure of COF, the ion transport channels are blocked due to the relatively thick thickness of the COF / rGO nanosheets, which reaches 2.9-6.0 nm.

[0007] For example, existing technology 2 (Xueying Kong, Shengyang Zhou, et al. Redoxactive covalentorganic framework based conductive nanofibers for flexible energy)

[0008] Storage device[J].Carbon,171(2021)248-256.) Core-shell c-CNT@COF materials were prepared by using carboxylated carbon nanotubes (c-CNTs) to regulate COF growth. The addition of carboxylated carbon nanotubes (c-CNTs) can effectively control COF growth.

[0009] The thickness and morphology of the nanolayers. At a current density of 0.2 A / g, it can provide a specific capacitance of 418.7 F / g, and after 10,000 GCD cycles, the device retains more than 94.0% of its original capacitance. This technical solution uses c-CNTs to regulate the microstructure of the COF. Although this effectively avoids stacking, the small surface area provided by the c-CNT material itself prevents uniform growth during COF induction, thus hindering the formation of a porous structure and consequently hindering the establishment of ion transport channels, resulting in a low ion transport rate. Summary of the Invention:

[0010] The purpose of this invention is to provide an EG / DT-COF based on EG-controlled micromorphology, its preparation method, and its application.

[0011] The basic principle is as follows: by growing DT-COF on the surface of expanded graphite EG, the microstructure of DT-COF is controlled to improve the electrochemical performance of the composite material. At the same time, the surface of expanded graphite EG contains a large number of oxygen-containing functional groups, such as hydroxyl and carboxyl groups. These oxygen-containing functional groups can interact with the organic molecules of DT-COF through non-covalent interactions mainly based on hydrogen bonds and van der Waals forces, providing a good growth interface for DT-COF and improving the ion transport rate.

[0012] Furthermore, DT-COF is a COF based on the β-ketoenamine structure. This structure has strong stability and a large specific surface area, exposing more active sites and effectively improving the electron and ion transport rate during the electrochemical reaction, thereby enhancing the electrochemical performance of energy storage devices.

[0013] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0014] An EG / DT-COF based on EG-regulated microstructure is prepared using diaminoanthraquinone, triformylphloroglucinol, and expanded graphite as raw materials, p-toluenesulfonic acid as a catalyst, and deionized water as a lubricant, and is prepared by physical grinding method to form a composite covalent organic framework supercapacitor anode material.

[0015] The material has a layered porous structure with a pore size of 2-50 nm;

[0016] The material is stable in the range of 20-450℃, but begins to decompose at 445-455℃.

[0017] A method for preparing EG / DT-COF based on EG-regulated micromorphology includes the following steps:

[0018] Step 1, Preparation of expanded graphite EG: Under certain conditions, expandable graphite is heated to obtain expanded graphite EG.

[0019] In step 1, the heating conditions for expandable graphite are as follows: under air conditions, the heating temperature is 900-1000℃ and the heating time is 1-2 minutes.

[0020] Step 2, Preparation of DT-COF based on EG-regulated microstructure: First, EG obtained in Step 1, diaminoanthraquinone (DAAQ), phloroglucinol (TFP), and p-toluenesulfonic acid (PTSA) are mixed in a certain mass ratio. DAAQ, EG, and PTSA are placed in a mortar and deionized water is added dropwise to obtain mixture A. Then, mixture A is ground under certain conditions. After that, TFP is added to mixture A to obtain mixture B. Mixture B is ground under certain conditions to obtain the reactant. Finally, the reactant is placed in an oven under certain conditions for reaction. After the reaction is completed, the obtained product is ground, washed, and dried to obtain a deep red EG / DT-COF based on EG-regulated microstructure, abbreviated as EG / DT-COF.

[0021] In step 2, the mass ratio of EG, DAAQ, TFP and PTSA is 3:2:20;

[0022] In step 2, the grinding conditions for mixture A are as follows: grinding time is 25-30 minutes.

[0023] In step 2, the grinding conditions for mixture B are as follows: grinding time is 25-30 minutes.

[0024] In step 2, the reaction conditions are: a reaction temperature of 95-100℃ and a reaction time of 92-96h.

[0025] An application of EG / DT-COF based on EG-controlled micromorphology as a negative electrode material in supercapacitors shows that, in the charging and discharging range of -0.3 to 1V, the specific capacitance is 495-501 F / g at a current density of 1 A / g; and the capacitance retention rate is 93-94.4% after 10,000 GCD cycles.

[0026] The beneficial technical effects of this invention have been tested experimentally, and the results are as follows:

[0027] SEM analysis revealed that EG / DT-COF exhibits a layered porous structure. This demonstrates that the addition of EG plays a role in regulating the morphology of DT-COF.

[0028] EG / DT-COF, tested by BET, has a specific surface area of ​​1397 m². 2 / g, with pore sizes ranging from 2-50nm. This demonstrates that EG / DT-COF possesses a large specific surface area.

[0029] EG / DT-COF, as tested by TGA, exhibits stability within the temperature range of 20-450℃, but begins to decompose at 445-455℃. This demonstrates the good stability of EG / DT-COF.

[0030] EG / DT-COF was tested for specific capacitance. Within the charge-discharge range of -0.3 to 1V, the specific capacitance was 495-501 F / g at a current density of 1 A / g. This demonstrates that EG / DT-COF possesses excellent electrochemical performance.

[0031] After GCD cycling tests, EG / DT-COF maintained a capacitance of 93-94.4% after 10,000 cycles, demonstrating its excellent cycling performance.

[0032] Therefore, the present invention has the following advantages over the prior art:

[0033] 1. The EG / DT-COF prepared by this invention forms a layered porous structure through EG regulation, which helps to improve the ion transport rate and solves the problem of low conductivity of DT-COF;

[0034] 2. This invention utilizes the large number of oxygen-containing functional groups on the surface of EG to conduct non-covalent interactions with the organic molecules of DT-COF, thereby enhancing the stability of the material;

[0035] 3. This invention uses a grinding method with water as a solvent, which is safer than traditional hydrothermal methods and organic solvents. It also reduces energy consumption and equipment requirements, making it more environmentally friendly. Attached image description:

[0036] Figure 1XRD patterns of EG / DT-COF prepared in Example 1, Comparative Example 2, and Comparative Example 3;

[0037] Figure 2 SEM image of EG / DT-COF-9 prepared in Example 1;

[0038] Figure 3 The nitrogen adsorption-desorption curve of EG / DT-COF-9 prepared in Example 1 is shown.

[0039] Figure 4 The aperture size distribution diagrams for Example 1 and Comparative Example 1 are shown.

[0040] Figure 5 TGA image of EG / DT-COF-9 prepared in Example 1;

[0041] Figure 6 The constant current charge-discharge curves of EG / DT-COF-9 prepared in Example 1 at current densities of 0.5, 1, 2, 5, and 8 A / g.

[0042] Figure 7 The cycling performance of EG / DT-COF-9 prepared in Example 1 after 10,000 cycles is shown in the graph.

[0043] Figure 8 Cyclic voltammetry curves of EG / DT-COF-9 prepared in Example 1 at scan rates of 5MV, 10MV, 20MV, 50MV, and 100MV.

[0044] Figure 9 SEM image of DT-COF prepared in Comparative Example 1;

[0045] Figure 10 Nitrogen adsorption-desorption curve of DT-COF prepared in Comparative Example 1;

[0046] Figure 11 SEM image of EG / DT-COF-7 prepared for Comparative Example 2;

[0047] Figure 12 The constant current charge-discharge curves of EG / DT-COF prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 at a current density of 1 A / g are shown.

[0048] Figure 13 SEM image of EG / DT-COF-11 prepared for Comparative Example 3;

[0049] Figure 14 The constant current charge-discharge curves of DT-COF prepared for Comparative Examples 4 and 5 at a current density of 1 A / g are shown. Detailed Implementation

[0050] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0051] Example 1

[0052] A method for preparing EG / DT-COF based on EG-regulated micromorphology includes the following steps:

[0053] Step 1, Preparation of expanded graphite EG: Under air conditions, expandable graphite is heated at a temperature of 1000℃ for a heating time of 1 min to obtain expanded graphite EG.

[0054] Step 2, Preparation of DT-COF based on EG-regulated microstructure: First, using the mass ratio of EG obtained in Step 1, diaminoanthraquinone (DAAQ), triformylphloroglucinol (TFP), and p-toluenesulfonic acid (PTSA) of 3:2:20, 0.107 g of DAAQ, 0.0153 g of EG, and 0.5 g of PTSA were placed in a mortar and 1 mL of deionized water was added to obtain mixture A. Then, mixture A was ground for 30 min. After that, 0.063 g of... TFP was added to mixture A to obtain mixture B. Mixture B was ground for 30 minutes to obtain the reactant. Finally, the reactant was placed in an oven for reaction at a reaction temperature of 100°C and a reaction time of 96 hours. After the reaction was completed, the obtained product was ground, washed, and dried to obtain a deep red EG / DT-COF based on EG-controlled microstructure, abbreviated as EG / DT-COF. The EG / DT-COF obtained in specific Example 1 was named EG / DT-COF-9.

[0055] To demonstrate the composition and structure of EG / DT-COF-9, XRD tests were performed. The test results are as follows: Figure 1 As shown, EG / DT-COF-9 exhibits characteristic peaks of COF materials at 3.6 degrees and characteristic peaks of EG at 26.6 degrees. The test results indicate that EG / DT-COF was successfully synthesized.

[0056] To verify the microstructure of EG / DT-COF-9, SEM testing was performed. The test results are as follows: Figure 2 As shown, EG / DT-COF-9 has a layered porous structure.

[0057] To further demonstrate the microporous structure of EG / DT-COF-9, BET testing was performed. The test results are as follows: Figure 3 and Figure 4 As shown, the specific surface area of ​​EG / DT-COF-9 is as high as 1397 m². 2 / g, and the pore size is between 2-50nm, with only mesopores present.

[0058] To demonstrate the thermal stability of EG / DT-COF-9, TGA testing was performed. The test results are as follows: Figure 5 As shown, EG / DT-COF-9 exhibits slight mass loss at 140℃ and 220℃. The loss is only 7.3% before 450℃, indicating stability below 450℃. However, above 450℃, EG / DT-COF begins to decompose.

[0059] To demonstrate the performance of EG / DT-COF as a supercapacitor, electrode sheets were prepared and their electrochemical performance was tested. Specifically, the electrode sheets were prepared by grinding EG / DT-COF, acetylene black, and polytetrafluoroethylene (PTFE) in a mortar with a mass ratio of 8:1:1, adding 0.5 mL of ethanol, and grinding to obtain the electrode material. Then, the electrode material was pressed with a 2 mm thick nickel foam current collector at a pressure of 10 kPa to obtain the electrode sheet. Finally, the electrode sheet was dried in air at room temperature and then cut into 2 cm × 2 cm pieces.

[0060] The charge / discharge performance test results of EG / DT-COF-9 are as follows: Figure 6 As shown, the specific capacitance of EG / DT-COF is 501F / g when the discharge current density is 1A / g.

[0061] The GCD cycle performance test results of EG / DT-COF-9 are as follows: Figure 7 As shown, at a discharge current density of 1 A / g and a cycle count of 10,000, the capacitance retention of EG / DT-COF is 94.4%.

[0062] The CV test results of EG / DT-COF-9 are as follows: Figure 8 As shown, when the scan rate is 20mV / s, the charge-discharge test was performed, and the system remained stable after three charge-discharge cycles.

[0063] To demonstrate the effect of EG on composite materials, Comparative Example 1 is provided, which is DT-COF prepared without the addition of EG.

[0064] Comparative Example 1

[0065] A method for preparing DT-COF without adding EG is provided. The steps unless otherwise specified are the same as in Example 1, except that step 1 is not required, and EG is not added in step 2. The resulting material is named DT-COF.

[0066] The SEM test results of DT-COF are as follows: Figure 9As shown, DT-COF is a tightly stacked sheet structure. Comparison with the SEM test results of Example 1 shows that the addition of EG transforms the microstructure of COF from a tightly stacked sheet structure to a layered porous structure.

[0067] The BET test results of DT-COF are as follows: Figure 4 and Figure 10 As shown, the specific surface area of ​​DT-COF is 956 m². 2 / g. The pore size is between 0-50nm, containing both micropores and mesopores. Comparison with the BET test results of Example 1 shows that adding EG causes the micropores to disappear while simultaneously increasing the specific surface area. This phenomenon contradicts the conventional view—generally, increasing the microporous structure can improve the specific surface area of ​​a material. The reason, combined with subsequent TGA test results, is that oligomers were generated during the synthesis of DT-COF. These oligomers are the direct cause of micropores, and their presence blocks the mesopores, reducing ion transport rates. Adding EG causes the oligomers to disappear; although this reduces micropores, it actually exposes the mesoporous structures that were blocked by the oligomers, ultimately increasing the specific surface area of ​​the material.

[0068] The TGA test results of DT-COF are as follows: Figure 5 As shown, DT-COF experiences a 6% mass loss at 420℃, and a 7.3% loss before 450℃. Above 450℃, EG / DT-COF begins to decompose. Comparison with the TGA test results of Example 1 shows that the stability before and after adding EG is not significantly different. The mass loss of DT-COF is attributed to the formation of oligomers during the synthesis of DT-COF, which decompose at 420℃.

[0069] The charge-discharge performance test results of DT-COF are as follows: Figure 6 As shown, the specific capacitance of DT-COF is 407 F / g at a discharge current density of 1 A / g. A comparison with the electrochemical performance test results of Example 1 shows that the addition of EG increased the specific capacitance by 23%.

[0070] By comparing Comparative Example 1 and Example 1, it can be seen that adding EG can not only adjust the microstructure of the composite material, but also make the oligomers that were originally blocked in the mesopores disappear, thereby increasing the ion transport rate and improving the electrochemical performance.

[0071] To demonstrate the effect of EG addition on the composite material, Comparative Example 2 and Comparative Example 3 are provided, with EG / DT-COF prepared by adding 7% and 11% EG, respectively.

[0072] Comparative Example 2

[0073] A method for preparing EG / DT-COF with an EG addition of 7% is provided. The steps not specifically described are the same as those in Example 1, except that in step 2, the EG addition is 7%, i.e., 0.0119g of EG is added, and the resulting material is named EG / DT-COF-7.

[0074] The XRD test results of EG / DT-COF-7 are as follows: Figure 1 As shown, EG / DT-COF-7 exhibits characteristic peaks of COF material at 3.6 degrees and characteristic peaks of EG at 26.6 degrees. Comparison with the XRD test results of Example 1 shows that the characteristic peaks still exist even with reduced EG addition, indicating that it has no effect on the synthesis of EG / DT-COF.

[0075] SEM test results of EG / DT-COF-7 are as follows Figure 11 As shown, EG / DT-COF-7 has a layered structure, but the porous structure is not obvious. A comparison with the SEM test results of Example 1 shows that when the amount of EG added is too small, there are fewer growth interfaces provided, and particles are present on the material surface, indicating that COF does not grow uniformly on EG, and therefore cannot fully form a porous structure.

[0076] The charge / discharge performance test results of EG / DT-COF-7 are as follows: Figure 12 As shown, the specific capacitance of EG / DT-COF is 462 F / g at a discharge current density of 1 A / g. A comparison with the electrochemical performance test results of Example 1 reveals that when the amount of EG added is too small, the ion transport channel cannot be established, resulting in a low ion transport rate and ultimately poor electrochemical performance.

[0077] Comparative Example 3

[0078] A method for preparing EG / DT-COF with an EG addition of 11% is provided. The steps not specifically described are the same as in Example 1, except that in step 2, the EG addition is 11%, i.e., 0.0187g of EG is added, and the resulting material is named EG / DT-COF-11.

[0079] The XRD test results of EG / DT-COF-11 are as follows: Figure 1 As shown, EG / DT-COF-11 exhibits characteristic peaks of COF materials at 3.6 degrees and characteristic peaks of EG at 26.6 degrees. Comparison with the XRD test results of Example 1 shows that the characteristic peaks still exist even with increased EG content, indicating that it has no effect on the synthesis of EG / DT-COF.

[0080] SEM test results of EG / DT-COF-11 are as follows Figure 13As shown, the EG / DT-COF-11 layered stack is relatively thick, and the porous structure is not obvious. A comparison with the SEM test results of Example 1 shows that excessive EG addition leads to stacking and pore blockage.

[0081] The charge / discharge performance test results of EG / DT-COF-11 are as follows: Figure 12 As shown, the specific capacitance of EG / DT-COF is 477 F / g at a discharge current density of 1 A / g. A comparison with the electrochemical performance test results of Example 1 reveals that excessive EG addition leads to stacking, which blocks ion transport channels, reducing the ion transport rate and ultimately resulting in poor electrochemical performance.

[0082] By comparing Comparative Example 2, Comparative Example 3 and Example 1, it can be seen that...

[0083] When the amount of EG added is too small, ion transport channels cannot be established, resulting in a low ion transport rate. When the amount of EG added is too large, layered stacking occurs, blocking the ion transport channels and leading to a low ion transport rate. This indicates that changing the amount of EG added affects the morphology of the composite material, leading to a decrease in performance.

[0084] To demonstrate the effect of reaction temperature on the performance of DT-COF, Comparative Examples 4 and 5 are provided, with DT-COF synthesized at temperatures of 80℃ and 120℃, respectively.

[0085] Comparative Example 4

[0086] A method for synthesizing DT-COF at 80℃ is provided. The steps unless otherwise specified are the same as those in Comparative Example 1, except that the reaction temperature is 80℃ and the resulting material is named DT-COF-80.

[0087] The charge / discharge performance test results of DT-COF-80 are as follows: Figure 14 As shown, the specific capacitance of DT-COF-80 is 284 F / g at a discharge current density of 1 A / g. Comparison with the electrochemical performance test results of Comparative Example 1 reveals that at excessively low temperatures, DT-COF synthesis is incomplete, resulting in poor electrochemical performance.

[0088] Comparative Example 5

[0089] A method for synthesizing DT-COF at 120℃ is provided. The steps unless otherwise specified are the same as those in Comparative Example 1, except that the reaction temperature is 120℃ and the resulting material is named DT-COF-120.

[0090] The charge / discharge performance test results of DT-COF-120 are as follows: Figure 14As shown, the specific capacitance of DT-COF-120 is 345 F / g at a discharge current density of 1 A / g. Comparison with the electrochemical performance test results of Comparative Example 1 reveals that while sufficient DT-COF can be synthesized at excessively high temperatures, other oligomers are generated, affecting the purity of DT-COF and resulting in poor electrochemical performance.

[0091] Comparisons of Comparative Examples 1, 4, and 5 show that DT-COF cannot be fully synthesized at too low a temperature, and other oligomers will be generated at too high a temperature, reducing the purity of DT-COF.

Claims

1. A method for preparing EG / DT-COF based on EG-regulated microstructure, characterized in that... Includes the following steps: Step 1, Preparation of expanded graphite EG: Expandable graphite is heated to obtain expanded graphite EG. Step 2, Preparation of DT-COF based on EG-regulated microstructure: First, EG obtained in Step 1, diaminoanthraquinone (DAAQ), phloroglucinol (TFP), and p-toluenesulfonic acid (PTSA) were placed in a mortar and deionized water was added dropwise to obtain mixture A. Then, mixture A was ground. After that, TFP was added to mixture A to obtain mixture B. Mixture B was ground to obtain the reactant. Finally, the reactant was placed in an oven for reaction. After the reaction was completed, the obtained product was ground, washed, and dried to obtain the deep red EG / DT-COF based on EG-regulated microstructure, abbreviated as EG / DT-COF. The obtained EG / DT-COF has a layered porous structure with a pore size of 2-50 nm; it is stable in the range of 20-450℃, but begins to decompose at 445-455℃.

2. The preparation method according to claim 1, characterized in that: In step 1, the heating conditions for expandable graphite are as follows: under air conditions, the heating temperature is 900-1000℃ and the heating time is 1-2 min.

3. The preparation method according to claim 1, characterized in that: In step 2, the mass ratio of EG, DAAQ, TFP, and PTSA is 0.0153:0.107:0.063:0.

5.

4. The preparation method according to claim 1, characterized in that: In step 2, the grinding conditions for mixture A are as follows: grinding time is 25-30 min; In step 2, the grinding conditions for mixture B are as follows: grinding time is 25-30 min. In step 2, the reaction conditions are: a reaction temperature of 95-100℃ and a reaction time of 92-96h.

5. The application of EG / DT-COF obtained by the preparation method according to claim 1 as a negative electrode material in supercapacitors, characterized in that: When charged and discharged within the range of -0.3 to 1V, the specific capacitance is 495-501 F / g when the current density is 1 A / g.

6. The application of EG / DT-COF obtained by the preparation method according to claim 1 as a negative electrode material in supercapacitors, characterized in that: After 10,000 GCD cycles, the capacitance retention rate was 93-94.4%.

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