A triazine-based porous polymer / cnt composite material, a preparation method and application thereof

Abstract

This invention provides a triazine-based porous polymer@CNT composite material, its preparation method, and its application, belonging to the technical field of organic polymer-based composite materials. The composite material uses 4,4',4”-(1,3,5-triazine-2,4,6-trimethyl)triphenylamine with a nitrogen-containing heterocyclic structure as the basic framework and reacts with 4,4'-biphenyldicarboxaldehyde via a Schiff base reaction to prepare the triazine-based porous framework. CNTs are added during the reaction to obtain the triazine-based porous polymer@CNT composite material. The composite material of this invention can be used as a negative electrode material in lithium-ion batteries, exhibiting good activity and stability at 1 A g. ‑1 It can still provide 350.9 mAh g after 2000 cycles at high current density. ‑1 Specific capacity.

Description

Technical Field

[0001] This invention belongs to the field of organic polymer-based composite materials technology, specifically relating to a triazine-based porous polymer@CNT composite material, its preparation method, and its application. Background Technology

[0002] Driven by various energy and environmental issues and the massive consumption of non-renewable fossil fuels, rechargeable lithium-ion batteries (LIBs), with their high energy density and stable cycle performance, have become the most popular energy storage devices. However, the development of renewable and environmentally friendly electrode materials is a key issue for the sustainable development of LIBs. Recent research has shown that organic electrode materials are among the best candidate materials for energy storage device research due to their diversity, environmental friendliness, and structural designability. Based on this, researchers have designed sustainable electrode materials for energy storage devices, such as organic free radicals, conjugated carbonyl compounds, organic sulfur compounds, and organic carbon / nitrogen compounds.

[0003] In recent years, the application of nitrogen-containing compounds (OCNs) as electrode materials has been widely reported. The electrochemically active sites containing nitrogen (N) can act as electrochemical reaction centers and offer the following advantages: compared to other materials, OCNs can provide more lithium storage sites per active unit; due to their high nitrogen content, OCNs can provide high conductivity; and the heteroaromatic N atoms in OCNs can increase the redox potential. However, the solubility, thermochemical instability, and poor conductivity of these small organic molecule electrode materials are serious obstacles limiting their development in energy storage systems. Therefore, it is crucial to design stable polymer framework structures with electroactive groups through molecular engineering as high-performance anode materials for lithium-ion batteries.

[0004] Nitrogen-containing porous organic polymers, as a rapidly developing type of porous polymer material, have become thermoelectric materials in the energy storage field due to their low backbone density, environmental friendliness, high thermochemical stability under harsh environments, and diverse molecular structures. In particular, introducing electrophilic triazine rings into the polymer backbone can effectively modulate the energy levels and band gaps of molecular orbitals, further regulating electron transport capabilities and redox potentials. However, due to the close packing of polymers, even at high current densities, Li... + It is also difficult to penetrate into the internal active sites buried deep between layers. This inevitably leads to insufficient utilization of redox active sites, thereby reducing the lithium storage capacity of the electrode material. Summary of the Invention

[0005] The purpose of this invention is to provide a triazine-based porous polymer@CNT composite material, its preparation method, and its application. The composite material of this invention has excellent conductivity and can be used as a negative electrode material in lithium-ion batteries, exhibiting good activity and stability.

[0006] The present invention adopts the following technical solution:

[0007] This invention first provides a triazine-based porous polymer@CNT composite material, which is formed by adding CNTs during the synthesis of the triazine-based porous polymer. The structural formula of the triazine-based porous polymer TAPT-BTPA is shown in Formula 1:

[0008]

[0009] This invention also provides a method for preparing a triazine-based porous polymer@CNT composite material, comprising:

[0010] 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 4,4'-biphenyldicarboxaldehyde and CNT were added to a reaction vessel, dissolved in a solvent, and then glacial acetic acid was added to obtain a mixture. The mixture was placed in a mixer to react and obtain a triazine-based porous polymer@CNT composite material.

[0011] Preferably, the mass ratio of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 4,4'-biphenyldicarboxaldehyde, and CNT is 14.17:12.62:13.50.

[0012] Preferably, the solvent is acetonitrile.

[0013] Preferably, the concentration of the glacial acetic acid is 6M.

[0014] Preferably, the reaction temperature is room temperature and the reaction time is 96 hours.

[0015] The present invention also provides the application of the above-mentioned triazine-based porous polymer@CNT composite material as a negative electrode material in lithium-ion batteries.

[0016] Beneficial effects of the present invention

[0017] This invention provides a triazine-based porous polymer@CNT composite material, its preparation method, and its application. This composite material is prepared by reacting a nitrogen-containing heterocyclic 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine (TAPT) as the basic framework with 4,4'-biphenyldicarboxaldehyde (BTPA) via a Schiff base reaction. CNTs are added during the reaction to prepare the triazine-based porous polymer@CNT composite material. The synthesized TAPT-BTPA@CNT possesses a stable polymer framework structure, solving the problem of easy solubility of small organic molecules in electrolytes. The abundant triazine framework and imine bonds in the triazine-based porous polymer can serve as Li... + The insertion sites are optimized to increase the capacity of LIBs; using BTPA as a monomer can increase the pore size of the polymer, which is beneficial for Li + The diffusion of TAPT as a monomer and the introduction of electrophilic triazine rings into the polymer can effectively regulate the energy levels and band gaps of molecular orbitals, and further regulate electron transport capability and redox potential. The introduction of CNTs allows the polymer to be separated in situ during growth; the polymer forms only a few layers around the CNTs through π-π interactions, effectively solving the severe stacking phenomenon of the polymer itself. Controllable growth of the polymer on CNTs not only improves the conductivity of the composite material but also further enhances the utilization rate of the polymer's active sites. Given the improved conductivity, porous structure, and abundant active sites of the composite material, it exhibits good energy storage performance as a negative electrode material for lithium-ion batteries. It can be used in lithium-ion batteries, possessing good activity and stability, and at 1 A g... -1 Even after 2000 cycles at high current density, it can still provide 350.9mAh g. -1 Specific capacity. Attached Figure Description

[0018] Figure 1 FT-IR spectra of TAPT, BTPA, TAPT-BTPA of Comparative Example 1, and TAPT-BTPA@CNT prepared in Example 1.

[0019] Figure 2 The image shows the SEM image of TAPT-BTPA in Comparative Example 1.

[0020] Figure 3 The image shows a SEM image of TAPT-BTPA@CNT prepared in Example 1.

[0021] Figure 4 Thermogravimetric properties of TAPT-BTPA in Comparative Example 1 and TAPT-BTPA@CNT prepared in Example 1 are shown in the diagram.

[0022] Figure 5Photographs of TAPT-BTPA from Comparative Example 1 and TAPT-BTPA@CNT prepared in Example 1 in the electrolyte;

[0023] Figure 6 N2 adsorption-desorption isotherms of TAPT-BTPA in Comparative Example 1 and TAPT-BTPA@CNT prepared in Example 1;

[0024] Figure 7 The TAPT-BTPA@CNT prepared in Example 1 was used at 0.1 mV s -1 The CV curve;

[0025] Figure 8 The TAPT-BTPA@CNT prepared in Example 1 was in 1A g -1 Cyclic stability at current density;

[0026] Figure 9 The rate performance curve of TAPT-BTPA@CNT prepared in Example 1;

[0027] Figure 10 The EIS spectra of TAPT-BTPA@CNT prepared in Example 1 are shown in the initial state and after 1, 5, 50, 100 and 200 cycles. Detailed Implementation

[0028] This invention first provides a triazine-based porous polymer@CNT composite material, which is formed by adding CNTs during the synthesis of the triazine-based porous polymer. The structural formula of the triazine-based porous polymer TAPT-BTPA is shown in Formula 1:

[0029]

[0030] This invention also provides a method for preparing a triazine-based porous polymer@CNT composite material, comprising:

[0031] 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 4,4'-biphenyldicarboxaldehyde, and CNTs are added to a reaction vessel and dissolved in a solvent. The preferred dissolution method is ultrasonic dissolution, with an ultrasonic time of 1-2 min. The preferred solvent is acetonitrile. Then, glacial acetic acid is added, with a concentration of 6 M, to obtain a mixture. The mixture is placed in a mixer and preferably shaken vigorously for 10-15 s before reacting. The preferred reaction temperature is room temperature, and the preferred reaction time is 96 h. The obtained product is preferably collected by centrifugation and washed three times with N,N-dimethylformamide, tetrahydrofuran, and anhydrous ethanol, respectively. Finally, the powder is dried under high vacuum conditions for 24-48 h to obtain a triazine-based porous polymer@CNT composite material.

[0032] According to the present invention, the preferred mass ratio of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 4,4'-biphenyldicarboxaldehyde and CNT is 14.17:12.62:13.50.

[0033] The present invention also provides the application of the above-mentioned triazine-based porous polymer@CNT composite material as a negative electrode material in lithium-ion batteries.

[0034] The present invention will be further described in detail below with reference to specific embodiments. All raw materials involved in the embodiments are commercially available.

[0035] Comparative Example 1: Synthesis of Triazine Porous Polymer (TAPT-BTPA)

[0036] 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine (14.17 mg) and 4,4'-biphenyldicarboxaldehyde (12.62 mg) were added to a test tube. Then, 5 mL of acetonitrile was added, and the mixture was sonicated for 1 min to completely dissolve it. Next, 0.4 mL of 6M glacial acetic acid was added. The mixture was then vigorously shaken on a vortex mixer for 10 s and reacted at room temperature for 96 h. The resulting yellow precipitate was collected by centrifugation and washed three times with N,N-dimethylformamide, tetrahydrofuran, and anhydrous ethanol, respectively. Finally, the powder was dried under high vacuum for 24 h to obtain 13.5 mg of a yellow solid powder. The reaction process is as follows:

[0037]

[0038] Example 1

[0039] 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine (14.17 mg), 4,4'-biphenyldicarboxaldehyde (12.62 mg), and CNT (13.50 mg) were added to a test tube. Then, 5 mL of acetonitrile was added, and the mixture was sonicated for 1 min to ensure complete dissolution. Next, 0.4 mL of 6M glacial acetic acid was added. The mixture was then vigorously shaken on a vortex mixer for 10 s and reacted at room temperature for 96 h. The resulting yellow precipitate was collected by centrifugation and washed three times with N,N-dimethylformamide, tetrahydrofuran, and anhydrous ethanol, respectively. Finally, the powder was dried under high vacuum for 24 h to obtain the triazine-based porous polymer@CNT composite material.

[0040] Figure 1 FT-IR spectra of TAPT, BTPA, TAPT-BTPA from Comparative Example 1, and TAPT-BTPA@CNT prepared in Example 1. Figure 1 It can be seen that a 1625 cm⁻¹ appears in the FTIR spectra of TAPT-BTPA and TAPT-BTPA@CNT. -1 The strong C=N stretching peak at 2794 cm⁻¹, and also at 2701 cm⁻¹. -1 The characteristic peaks of -CH in BTPA are located at 3466, 3333 and 3219 cm⁻¹. -1 The near disappearance of the characteristic peak of the -NH- stretching vibration in TAPT, and the 1605 cm⁻¹ -1 The disappearance of the -C=O group in BTPA indicates the success of the condensation reaction between TAPT and BTPA. The weaker amino characteristic peak in the TAPT-BTPA spectrum is attributed to unreacted groups on the side chains. The FTIR spectrum of TAPT-BTPA@CNT shows a peak at 3402 cm⁻¹. -1 The broad characteristic peak at that location is attributed to the presence of some water in the material.

[0041] Figure 2 Here is a SEM image of TAPT-BTPA from Comparative Example 1; from Figure 2 As can be seen, TAPT-BTPA exhibits a coral-like nanoribbon morphology with a smooth surface and uniform shape.

[0042] Figure 3 The image shows a SEM image of TAPT-BTPA@CNT prepared in Example 1; from Figure 3As can be seen, after CNT doping, the coral-like morphology disappears, and TAPT-BTPA@CNT exhibits a uniform linear nanotube morphology. Furthermore, no large, isolated polymer particles exist around the tubes, indicating that it grows uniformly on the CNT surface in a thin layer. It can also be observed that after CNT and polymer are combined, the composite material becomes very porous, possessing numerous pores. This will facilitate the entry of electrolytes and promote electron transport, potentially improving the electrochemical energy storage performance of both polymers.

[0043] Figure 4 Thermogravimetric properties of TAPT-BTPA in Comparative Example 1 and TAPT-BTPA@CNT prepared in Example 1 are shown in the diagram. Figure 4 It can be seen that TAPT-BTPA exhibits a 4.85% capacity loss rate at 200℃, which is attributed to the presence of organic solvents and moisture in the material. TAPT-BTPA shows no significant capacity loss before 500℃, maintaining an 89.52% weight retention rate. After 500℃, a rapid weight reduction occurs due to partial skeleton collapse, but a 50.78% weight retention rate is still maintained at 700℃. When compounded with CNTs, TAPT-BTPA@CNT also exhibits good weight retention before 500℃, and retains approximately 82.76% weight retention even at temperatures up to 700℃, indicating good polymer skeleton stability.

[0044] Figure 5 Photographs of TAPT-BTPA from Comparative Example 1 and TAPT-BTPA@CNT prepared in Example 1 in an electrolyte solution, wherein the electrolyte is 1M LiPF6 dissolved in ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (volume ratio 1:1:1). Figure 5 It can be seen that TAPT-BTPA and TAPT-BTPA@CNT maintain good morphology in the electrolyte, which is clear and transparent, further demonstrating their good structural stability and promising to ensure reversible redox reactions during electrochemical energy storage.

[0045] Figure 6 The N2 adsorption-desorption isotherms of TAPT-BTPA in Comparative Example 1 and TAPT-BTPA@CNT prepared in Example 1 are shown. Figure 6 It can be seen that the specific surface area for TAPT-BTPA is determined to be 32.46 m². 2 g -1 The BET for TAPT-BTPA@CNT was determined to be 209.98m. 2 g -1Clearly, the specific surface area of ​​the polymer increases significantly after being combined with CNTs, providing favorable conditions for the rapid diffusion and penetration of the electrolyte into the material. Furthermore, it can be observed that both TAPT-BTPA and TAPT-BTPA@CNT exhibit a rapid rise in isotherm under relatively high pressures (0.8–1), indicating that they are both mesoporous.

[0046] CR2032 coin cells were assembled using TAPT-BTPA@CNT as the negative electrode material according to the techniques in this field to study the lithium storage performance of TAPT-BTPA@CNT as the negative electrode material. The specific assembly steps are as follows: TAPT-BTPA@CNT, acetylene black, and sodium carboxymethyl cellulose were mixed in a weight ratio of 8:1:1 with water as a solvent to prepare a uniform slurry for use as the electrode. The slurry was thoroughly ground in a mortar for 60 minutes. Then, the uniform slurry was coated onto copper foil and dried at room temperature. The dried electrode sheet was cut into 1 cm discs. In an Ar-filled glove box, the CR2032 coin cells were assembled in the following order: negative electrode shell, electrode sheet, electrolyte, separator, lithium sheet, gasket, spring sheet, and positive electrode shell. First, its redox mechanism was studied by CV testing.

[0047] Figure 7 The TAPT-BTPA@CNT prepared in Example 1 was used at 0.1 mV s -1 The CV curve; from Figure 7 As can be seen, the CV curves only show significant reduction peaks at 1.81V, 0.93V, and 0.66V in the first cycle, which is due to the formation of the SEI film. In subsequent cycles, the broad, weak reduction peak at 1.22-0.58V corresponds to the lithiation of C=C and C=C double bonds. During the subsequent oxidation process, the broad, weak oxidation peak at 0.68-1.44V is attributed to the insertion and extraction of lithium ions and the reformation of C=C and C=C double bonds. The overlapping of the CV curves in subsequent cycles demonstrates the stable redox reaction of TAPT-BTPA@CNT.

[0048] Figure 8 The TAPT-BTPA@CNT prepared in Example 1 was in 1A g -1 Cyclic stability at current density; Figure 8 As can be seen, in the first cycle, the reversible charging specific capacity of TAPT-BTPA@CNT is 572.8mAh g. -1The low coulombic efficiency at this point is due to the formation of the SEI film. During subsequent constant current cycling, the coulombic efficiency gradually increases to approximately 98%. The first 30 cycles show a relatively rapid capacity decay, likely due to electrolyte decomposition at high current densities. In subsequent cycles, the capacity shows an upward trend due to the activation of more active sites, stabilizing around 350 cycles, and still providing 350.9 mAh g⁻¹ after 2000 cycles. -1 The high specific charge capacity and coulombic efficiency of 99% demonstrate the good energy storage performance of TAPT-BTPA@CNT as an anode material.

[0049] In addition, to further evaluate the potential application of TAPT-BTPA@CNT as a negative electrode material, the rate performance under stepped current density was evaluated through continuous constant current charge-discharge tests, which is an important indicator for electrode materials to achieve rapid charge-discharge. Figure 9 The rate performance curve of TAPT-BTPA@CNT prepared in Example 1 is shown; from Figure 9 It can be seen that at 0.1Ag -1 After 10 cycles, when the current density decreases from 0.2 A g -1 Stepped type increased to 5A g -1 At that time, the capacity provided by TAPT-BTPA@CNT at different current densities was 490.9 mAh g. -1 382.4mAh g -1 303.4mAh g -1 243.6mAh g -1 and 177.9 mAh g -1 When the current density is readjusted back to 0.1 A g -1 At that time, it can still provide 515.3mAh g -1 The inverse capacity confirms its good rate performance.

[0050] Figure 10 The EIS spectra of TAPT-BTPA@CNT prepared in Example 1 are shown in the initial state and after 1, 5, 50, 100, and 200 cycles. Figure 10As can be seen, the initial EIS spectrum before cycling and the EIS spectra after 1, 5, 50, 100, and 200 cycles are displayed. The spectra are mainly divided into two parts: a low-frequency sloping line and a high-frequency semicircle, representing the Warburg resistance (Rw) and charge transfer resistance (Rct), respectively. It can be observed that the Rct value of TAPT-BTPA@CNT increases after one cycle, which is due to the formation of an SEI film during the first cycle; after five cycles, Rct gradually decreases, which is due to electrochemical activation; the approximate Rct values ​​after 50, 100, and even 200 cycles confirm the structural stability of TAPT-BTPA@CNT during repeated redox processes.

Claims

1. The application of a triazine-based porous polymer@CNT composite material as a negative electrode material in lithium-ion batteries, characterized in that, This composite material is formed by adding CNTs during the synthesis of a triazine-based porous polymer. The structural formula of the triazine-based porous polymer TAPT-BTPA is shown in Formula 1. The method for preparing a triazine-based porous polymer@CNT composite material includes: 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 4,4'-biphenyldicarboxaldehyde and CNT were added to a reaction vessel, dissolved in a solvent, and then glacial acetic acid was added to obtain a mixture. The mixture was placed in a mixer to react and obtain a triazine-based porous polymer@CNT composite material. The mass ratio of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 4,4'-biphenyldicarboxaldehyde, and CNT is 14.17:12.62:13.

50. The reaction temperature was room temperature, and the reaction time was 96 hours.

2. The application according to claim 1, characterized in that, The solvent is acetonitrile.

3. The application according to claim 1, characterized in that, The concentration of the glacial acetic acid is 6M.

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