Phenazine covalent organic framework / carbon nanotube composite material as well as preparation method and application thereof

Abstract

The invention discloses a phenazine covalent organic framework / carbon nanotube composite material as well as a preparation method and application thereof, and relates to the technical field of phenazine covalent organic framework composite materials and lithium ion batteries. The preparation method comprises the following steps: firstly, uniformly dispersing carbon nanotubes in a reaction organic solvent, and by taking the liquid-phase dispersed carbon nanotubes as nucleation sites, respectively carrying out dehydration condensation reaction on cyclohexanehexone and different primary amines to form phenazine bonds, thereby realizing in-situ growth of covalent organic frameworks (COFs) in the carbon nanotubes; the phenazine covalent organic framework (P-COFs) coated carbon nanotube composite material is obtained. The composite material solves the problems of poor conductivity and low active site utilization rate of a covalent organic framework material, and has high specific capacity, good rate capability and excellent cycle performance as a lithium ion battery electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrode materials, and particularly relates to a preparation method and application of a phenazine covalent organic framework and carbon nanotube composite material. BACKGROUND

[0002] Since the commercial application of lithium ion batteries (LIBs) in 1991, they have rapidly become the core energy storage device in the field of portable electronic devices and new energy vehicles due to their excellent electrochemical performance indicators. However, although LIBs dominate the market, their energy density is close to the theoretical limit, and they face problems such as resource shortage and flammable organic electrolyte. In the pursuit of high energy density, problems such as thermal runaway and lithium dendrite growth in the battery can lead to short circuits, fires, and even explosions; during charging and discharging, problems such as volume expansion of electrode materials and decomposition of electrolyte can cause rapid decline in battery performance, and so on. Therefore, developing new electrode materials with high performance has become an important direction for LIB research.

[0003] Covalent organic frameworks (COFs) are a new type of porous crystalline polymer with advantages such as lightweight framework, adjustable structure, and high specific surface area. Compared to traditional organic compound electrode materials, redox-active COFs exhibit more outstanding electrochemical performance as LIB electrode materials. The rich redox active sites within COF materials can theoretically provide more reaction sites for Li + insertion and extraction, thereby helping to improve the specific capacity of the battery. However, due to the high-density stacking of the two-dimensional layered structure of COF materials, this tight stacking structure causes the active sites within the material to be largely covered, resulting in some redox active sites not being fully utilized, thereby reducing their actual reversible specific capacity. On the other hand, most COFs are insulators or semiconductors, with poor electrical conductivity, which severely limits their electrochemical performance and hinders their practical application. In recent years, COFs have been modified by preparing composite materials with conductive materials, which can effectively improve the electrical conductivity, but there is still a lack of LIB electrode materials with high capacity, rate, and lifespan that are compatible with phenazine COFs. Therefore, there is an urgent need to develop a COF composite material with excellent comprehensive performance, thereby promoting its practical application in the field of electrochemical energy storage.

[0004] After searching, the application publication number CN117996028A, a kind of nitrogen heterocyclic type covalent organic framework carbon nanotube composite material and its preparation method and application are searched.In the presence of carbon nanotube, six azabenzo phenanthrene six carboxylic acid trianhydride and 2, 6-diaminobenzene [1, 2-d, 4, 5-d'] dithiazole or 1, 3, 4-thiadiazole-2, 5-diamine are carried out in situ composite by dehydration condensation reaction, after the reaction is finished, it is washed with deionized water, suction filtration, vacuum drying to obtain the composite material of nitrogen heterocyclic type covalent organic framework and carbon nanotube.

[0005] 1、The patent does not require carbon nanotube pre-dispersion, but one-dimensional carbon nanotube powder is difficult to disperse uniformly in solution due to strong π-π stacking effect, which leads to the aggregation of carbon nanotube unable to provide uniform deposition sites for COF. This not only hinders the uniform coating of COF on carbon nanotube, but also causes insufficient exposure of COF active sites and blockage of electron transport channel in the composite material. In addition, the pre-dispersion process can significantly reduce the amount of carbon nanotube used, while the patent requires a large amount of carbon nanotube (i.e. material waste due to non-optimized dispersion). 2、The patent uses phenazine-based covalent organic framework (COF), which has excellent conductivity due to its large conjugated system, but it also exacerbates the tendency of molecular stacking. Therefore, it is necessary to rely on uniformly dispersed carbon nanotubes in solution as nucleation sites to inhibit COF self-aggregation through heterogeneous nucleation, thereby solving the stacking problem. 3、The pre-dispersion process simultaneously solves the dual contradiction of carbon nanotube aggregation and COF stacking. First, it achieves uniform dispersion of carbon nanotube to form a continuous conductive network, and COF grows on the surface of carbon nanotube to form hierarchical pores. Second, it maximizes the exposure of COF electrochemical active sites and strengthens the ion / electron dual-channel transmission. Finally, it significantly reduces the amount of carbon nanotube used and reduces the dependence on high-cost materials. SUMMARY

[0006] The present application aims to solve the problems of poor conductivity and low utilization rate of active sites of redox-active two-dimensional phenazine covalent organic framework material, and proposes a phenazine covalent organic framework / carbon nanotube composite material and its preparation method and application. The technical scheme of the present application is as follows:

[0007] A phenazine covalent organic framework / carbon nanotube composite material is formed by in-situ compounding of phenazine covalent organic framework (COFs) and carbon nanotube (CNTs), and the mass ratio of carbon nanotube to phenazine covalent organic framework is 1:10.

[0008] Further, the structural formula of the phenazine covalent organic framework is:

[0009]

[0010] A preparation method of a phenazine covalent organic framework / carbon nanotube composite material includes the following steps:

[0011] The organic solvent, the catalyst, the cyclohexanehexone octahydrate, the carbon nanotube, and 2,4,6,7,10,11-hexaaminobenzophenone hexahydrochloride and 1,2,4,5-benzene tetramine tetrahydrochloride and 3,3'-diaminobenzidine are mixed uniformly, respectively, and then a dehydration condensation reaction is carried out through a solvothermal method, and after cooling to room temperature, washing, suction filtration and drying are carried out to obtain a phenazine covalent organic framework and carbon nanotube composite material.

[0012] Further, the molar ratio of the cyclohexanehexone octahydrate and 2,4,6,7,10,11-hexaaminobenzophenone hexahydrochloride is 1:1, and the molar ratio of the cyclohexanehexone octahydrate and 1,2,4,5-benzene tetramine tetrahydrochloride or 3,3'-diaminobenzidine is 1:1.5.

[0013] Further, the dehydration condensation reaction temperature is 170-200 DEG C, and the reaction time is 3-5 days.

[0014] Further, the organic solvent comprises one or more of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.

[0015] Further, the catalyst is concentrated sulfuric acid, and the amount is 0.05-0.2 mL of concentrated sulfuric acid per milliliter of organic solvent.

[0016] Further, when suction filtration and washing are carried out, deionized water and acetone are used for preliminary washing in sequence, and then methanol is used as an extraction solvent, and a Soxhlet extraction method is used for deep washing for 2 days.

[0017] The phenazine covalent organic framework and carbon nanotube composite material is applied to a lithium ion battery electrode material.

[0018] The advantages and beneficial effects of the present application are as follows:

[0019] In the present application, a phenazine group is used as a connecting unit of two monomers to form a phenazine covalent organic framework, the phenazine group has a heteroatom nitrogen with a lone pair of electrons, has a unique pi conjugated system and rich C=N as a redox active site, and an electroactive imine group (-C=N-) exhibits a lower HOMO-LUMO energy level difference than other organic molecular structures, has a faster reaction rate and stronger charge transport capacity.

[0020] As one-dimensional nanocarbon materials, CNTs have excellent electrical conductivity, mechanical properties and chemical stability. Through compounding, CNTs provide efficient electron transmission channels for COFs, significantly improve the electrical conductivity of the materials, and make them exhibit more excellent performance in the field of electrochemistry; at the same time, the high mechanical strength of CNTs enhances the structural stability of COFs, so that they are not easy to collapse in the long cycle process. In addition, the mesoporous and macroporous structure of CNTs can form a multi-level pore with the microporous of COFs, optimize the mass transfer efficiency, and thus realize faster kinetic performance in the ion transmission process.

[0021] The present application in-situ composites phenazine covalent organic framework and carbon nanotubes through solvothermal method, constructs new COF@CNT electrode material, through utilizing the conductive skeleton of CNTs, enhances electron transmission, exposes more active sites, significantly improves specific capacitance, rate characteristics and stability and other electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the solid-state nuclear magnetic carbon spectrum of the preferred embodiment HTPHA-COF provided by the present application;

[0023] Figure 2 is the TEM graph of HTPHA-COF@CNT;

[0024] Figure 3 is the infrared spectrum graph of HTPHA-COF, HTPHA-COF@CNT;

[0025] Figure 4 is the rate performance graph of HTPHA-COF, HTPHA-COF@CNT;

[0026] Figure 5 is the solid-state nuclear magnetic carbon spectrum of HTAB-COF;

[0027] Figure 6 is the TEM graph of HTAB-COF@CNT;

[0028] Figure 7 is the infrared spectrum graph of HTAB-COF, HTAB-COF@CNT;

[0029] Figure 8 is the rate performance graph of HTAB-COF, HTAB-COF@CNT;

[0030] Figure 9 is the solid-state nuclear magnetic carbon spectrum of HDAB-COF;

[0031] Figure 10 is the TEM graph of HDAB-COF@CNT;

[0032] Figure 11 Figure 8 is an infrared spectrum of HDAB-COF and HDAB-COF@CNT;

[0033] Figure 12 Figure 9 is a rate performance graph of HDAB-COF and HDAB-COF@CNT;

[0034] Figure 13 Figure 5 is a schematic diagram of the chemical structure of the phenazine covalent organic framework and carbon nanotube composite material of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. The described embodiments are only a part of the embodiments of the present application.

[0036] The technical solution of the present application to solve the above technical problems is:

[0037] Embodiment 1

[0038] Preparation of the phenazine covalent organic framework and carbon nanotube composite material:

[0039] 38mL of heat-resistant Pyrex tube as a reaction container, 78mg of monomer cyclohexanehexone octahydrate (HKH·8H2O) (0.25mmol), 134.5mg of 2,4,6,7,10,11-hexamino triphenylene hexahydrate (TPHA·6HCl) (0.25mmol) were weighed and mixed uniformly.

[0040] The CNTs of 10% of the theoretical synthesis mass of COFs were weighed and added to a 50mL beaker, and 25mL of N-methyl pyrrolidone (NMP) solution was added dropwise for ultrasonic crushing for 1h.

[0041] The NMP solution containing CNTs after ultrasonic crushing was transferred to the above-mentioned Pyrex tube, and the mixture was placed in an ultrasonic bath for ultrasonic treatment for 30min. 2mL of concentrated sulfuric acid was added as a catalyst to the tube, and the heat-resistant Pyrex tube containing the above-mentioned mixture was continuously ultrasonically treated for about 10min to ensure that the entire reaction system reached a highly uniform dispersion state.

[0042] The heat-resistant Pyrex tube was subjected to three cycles of freezing-vacuumizing-thawing, with an interval of about 1-3min between each step. After the cycle was completed, the heat-resistant Pyrex tube was sealed to a vacuum state and placed in a blast drying oven with a temperature setting of 175℃ for constant temperature heating reaction, and the reaction time was about 72h.

[0043] After the reaction is completed, wait for the Pyrex tube to cool to room temperature, transfer the reaction system to a filtration device, use pure water and acetone as detergents, filter and wash the reaction product, repeat the operation 3-5 times, and then transfer the washed product to a Soxhlet extractor, use methanol as the extraction agent, and perform Soxhlet extraction for 2 days.

[0044] Finally, the extracted powdered material was transferred to a vacuum drying oven and dried at 120°C for approximately 24 hours. Once the material was completely dry, dried HTPHA-COF@CNT was obtained. The yield of this reaction system was calculated to be 96%.

[0045] The morphology and structure of the synthesized HTPHA-COF@CNT were analyzed by transmission electron microscopy (TEM). Figure 2 As shown, TEM clearly shows the inner CNTs and the outer stacked COFs, indicating that the COFs material has been successfully grown in situ on the CNTs. The diameter of the rod-like structure was measured using a ruler, and a COFs layer with a thickness of approximately 35nm was grown on the outside of the CNTs.

[0046] Fourier transform infrared spectroscopy (FT-IR) was performed to determine the chemical bond composition of HTPHA-COF@CNT. Figure 3 As shown in the figure, the stretching vibration peaks of the corresponding characteristic functional groups in the monomer are -NH2 (3335, 3219 cm -1 ) and HKH·8H2O C=O(1637cm -1 ), disappeared at the corresponding position of the synthesized HTPHA-COF@CNT, while at 1509, 1448 and 1396 cm -1 A new characteristic absorption peak of phenazine bond appears at , indicating that Example 1 was successfully prepared.

[0047] Applications of phenazine covalent organic framework and carbon nanotube composites:

[0048] Example 1 was used as the active material, and the mass ratio of the carbon tube and the binder was controlled to be 6:3:1. The binder was sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), and the mass ratio was controlled to be CMC:SBR=1:2. Pure water was used as the solvent. After sufficient grinding, a uniformly mixed electrode slurry was obtained. The electrode slurry was applied to the copper foil with a scraper and dried at 65°C for 6 hours to dry the solvent. The copper foil coated with the electrode slurry after drying was rolled using a roller press. The rolled copper foil was then cut into circular electrode sheets with a diameter of 12 mm, placed in a vacuum oven at 85°C and dried for 24 hours, and finally transferred to a glove box filled with argon for storage. The cut electrode sheet was used as the positive terminal and the lithium metal sheet as the negative terminal, separated by a polypropylene (PP) membrane, and 60 μL of a 1 M LiPF6 solution of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (volume ratio 1:1:1) was used as the electrolyte to assemble button-type LIBs (half-cell LIBs).

[0049] Under constant temperature conditions, the rate performance test of the electrode material of Example 1 was carried out. Figure 4 As shown in the figure, during the test, the current density gradually increased from 0.1 A / g to 0.2, 0.5, 1, 2, and 5, and the capacities were 1091, 987, 823, 676, 505, and 254 mAh / g, respectively. When the current density was reduced to 0.1 A / g again, the specific capacity returned to about the initial value, indicating that Example 1 can still maintain its stability under high current density conditions and fast charge and discharge rates.

[0050] Example 2

[0051] Preparation of a phenazine covalent organic framework and carbon nanotube composite material: The TPHA·6HCl in Example 1 was replaced with 106.5 mg (0.375 mmol) of 1,2,4,5-benzenetetramine tetrahydrochloride (TAB·4HCl). The reaction temperature was set to 185°C. Other reactions were the same as in Example 1. The product was named HTAB-COF@CNT. The yield of this reaction system was 96%.

[0052] like Figure 6 As shown in the figure, TEM can clearly observe the internal CNTs and the outer stacked COFs. The diameter of the rod-like structure was measured using a ruler, and a COFs layer with a thickness of about 35nm was grown on the outside of the CNTs. Figure 7 As shown, the stretching vibration peak of the corresponding characteristic functional group in the monomer is -NH2 (2895cm -1 ) and HKH·8H2O C=O(1637cm -1 ), disappear at the corresponding position of the synthesized HTAB-COF@CNT, while at 1439 and 1239 cm -1The characteristic absorption peak of the new phenazine bond appeared, indicating that Example 2 was successfully prepared.

[0053] Application of the phenazine covalent organic framework-carbon nanotube composite material:

[0054] The buckle battery was assembled with Example 2 as the active material according to Example 1.

[0055] The rate performance test was as shown in Figure 8 The current density was gradually increased from 0.1 A / g to 0.2, 0.5, 1, 2, 5, and the capacity was 786, 755, 674, 554, 443, and 258 mAh / g, respectively. When the current density was reduced to 0.1 A / g again, the specific capacity returned to the initial value, indicating that Example 2 could maintain its stability under the condition of high current density and fast charge-discharge rate.

[0056] Example 3

[0057] Preparation of the phenazine covalent organic framework-carbon nanotube composite material: TPHA·6HCl in Example 1 was replaced by 3,3'-diaminobenzidine (DAB) 80.35 mg (0.375 mmol), the reaction temperature was set to 200°C, and the other conditions were the same as in Example 1. The product was named HDAB-COF@CNT, and the yield of the reaction system was 81%.

[0058] As shown in Figure 10 , the TEM could clearly observe the internal CNTs and the outer stacked COFs. The diameter of the rod-shaped structure was measured using a ruler, and the COFs layer with a thickness of about 35 nm was grown on the outside of the CNTs. As shown in Figure 11 , the characteristic functional group stretching vibration peaks in the monomer were -NH2 (3387, 3355 cm -1 ) of DAB and C=O (1637 cm -1 ) of HKH·8H2O, which disappeared in the synthesized HDAB-COF@CNT, and a new characteristic absorption peak of the phenazine bond appeared at 1700 cm -1 , indicating that Example 3 was successfully prepared.

[0059] Application of the phenazine covalent organic framework-carbon nanotube composite material:

[0060] The buckle battery was assembled with Example 3 as the active material according to Example 1.

[0061] The rate performance test was as shown in Figure 12As shown, during the test, the current density gradually increased from 0.1 A / g to 0.2, 0.5, 1, 2, 5, and the capacity was 669, 585, 487, 413, 342, 252 mAh / g, respectively. When the current density was reduced to 0.1 A / g again, the specific capacity returned to the initial value, indicating that the product of Example 3 could maintain its stability under the condition of high current density and fast charge-discharge rate.

[0062] Comparative Example 1

[0063] Preparation of the phenazine covalent organic framework material:

[0064] In the preparation process of Example 1, no CNTs were added, and the other conditions were the same as in Example 1. The product was named as HTPHA-COF.

[0065] Application of the phenazine covalent organic framework material:

[0066] A button cell was assembled using the active material of Comparative Example 1 according to Example 1.

[0067] Rate performance test as shown in Figure 4 As shown, the capacity was 888, 750, 548, 398, 275, 156 mAh / g, respectively.

[0068] Comparative Example 2

[0069] Preparation of the phenazine covalent organic framework material:

[0070] In the preparation process of Example 2, no CNTs were added, and the other conditions were the same as in Example 2. The product was named as HTAB-COF.

[0071] Application of the phenazine covalent organic framework material:

[0072] A button cell was assembled using the active material of Comparative Example 2 according to Example 2.

[0073] Rate performance test as shown in Figure 8 As shown, the capacity was 650, 582, 469, 371, 270, 133 mAh / g, respectively.

[0074] Comparative Example 3

[0075] Preparation of the phenazine covalent organic framework material:

[0076] In the preparation process of Example 3, no CNTs were added, and the other conditions were the same as in Example 3. The product was named as HDAB-COF.

[0077] Application of the phenazine covalent organic framework material:

[0078] A button cell was assembled using the active material of Comparative Example 3 according to Example 3.

[0079] Rate performance test was carried out as described in Example 1. Figure 12 The capacities were 582, 501, 342, 234, 158, 75 mAh / g, respectively.

[0080] It should also be noted that the terms "comprising", "comprises" or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises a... " does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0081] The above examples are to be understood only as illustrative of the application and not a limitation of the scope of protection of the application. After reading the description of the application, a person skilled in the art can make various modifications or changes to the application, and these equivalent changes and modifications also fall within the scope defined by the claims of the application.

Claims

1. A phenazine covalent organic framework / carbon nanotube composite material, characterized in that: The composite is in situ formed by the in-situ compounding of phenazine covalent organic frameworks (COFs) and carbon nanotubes (CNTs), with the mass ratio of carbon nanotubes to phenazine covalent organic frameworks being 1:

10.

2. The phenazine covalent organic framework / carbon nanotube composite material according to claim 1, characterized in that: The structural formula of the phenazine covalent organic framework is:

3. A method for preparing a composite material of phenazine covalent organic framework and carbon nanotubes, characterized in that: The steps include: An organic solvent, a catalyst, cyclohexanone octahydrate, carbon nanotubes, 2,4,6,7,10,11-hexaaminotriphenylene hexahydrochloride, 1,2,4,5-phenyltetramine tetrahydrochloride, and 3,3'-diaminobenzidine are mixed uniformly, and then dehydrated and condensed by a solvent thermal method. After cooling to room temperature, the mixture is washed, filtered, and dried to obtain a phenazine covalent organic framework and carbon nanotube composite material.

4. The method for preparing the composite material of phenazine covalent organic framework and carbon nanotubes according to claim 3, characterized in that: The molar ratio of cyclohexanone octahydrate to 2,4,6,7,10,11-hexaaminotriphenylene hexahydrochloride is 1:1, and the molar ratio of cyclohexanone octahydrate to 1,2,4,5-phenyltetramine tetrahydrochloride or 3,3'-diaminobenzidine is 1:1.

5.

5. The method for preparing the composite material of phenazine covalent organic framework and carbon nanotubes according to claim 3, characterized in that: The dehydration condensation reaction temperature is 170-200°C, and the reaction time is 3-5 days.

6. The method for preparing the composite material of phenazine covalent organic framework and carbon nanotubes according to claim 3, characterized in that: The organic solvent includes a mixture of one or more of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

7. The method for preparing a composite material of phenazine covalent organic framework and carbon nanotubes according to claim 2, characterized in that: The catalyst is concentrated sulfuric acid, and the amount used is 0.05-0.2 mL of concentrated sulfuric acid per mL of organic solvent.

8. The method for preparing a composite material of phenazine covalent organic framework and carbon nanotubes according to claim 3, characterized in that: During filtration and washing, deionized water and acetone were used for preliminary washing in sequence, and then methanol was used as the extraction solvent and Soxhlet extraction was used for deep washing for 2 days.

9. An application of a phenazine covalent organic framework and carbon nanotube composite material, characterized in that: Used in lithium-ion battery electrode materials.

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