A triphenylene ketone-based two-dimensional covalent organic framework material, preparation method thereof and application as a cathode material for lithium-ion batteries

Abstract

The present invention belongs to the field of organic cathode materials for lithium-ion batteries, and particularly relates to a triphenylene ketone-based two-dimensional covalent organic framework material, a preparation method thereof, and an application as a cathode material for lithium-ion batteries. The triphenylene ketone-based two-dimensional covalent organic framework material prepared by the present invention presents a fully conjugated single crystal structure, and is rich in a large number of electrochemically active conjugated carbonyl groups and carbon-nitrogen double bonds, which can provide high-density redox active sites. As an electrode active material in lithium-ion batteries, it exhibits high reversible specific capacity, excellent cycle stability and rate performance, and has potential application value in the aspect of organic electrode materials.

Description

Technical Field

[0001] The present invention belongs to the field of organic cathode materials for lithium-ion batteries, and particularly relates to a triphenylene ketone-based two-dimensional covalent organic framework material, a preparation method thereof, and an application as a cathode material for lithium-ion batteries. Background Art

[0002] Lithium-ion batteries (LIBs) have been successfully and widely used as power sources in the fields of portable electronic devices and electric vehicles. However, with the advancement of technology development, they face two core challenges: one is that the improvement of energy density encounters bottlenecks, restricting the endurance; the other is the dependence on transition metals such as cobalt and nickel in inorganic cathode materials, which has raised concerns about resource scarcity and resource sustainability. Organic cathode materials (OCMs) have gradually become a research hotspot due to their significant potential in electrochemical performance and significant advantages in resource sustainability. Thanks to the rich electroactive groups or units in OCMs and the high degree of designability of organic structures, they are designed to be applied in rechargeable lithium batteries and other advanced battery systems in order to break through the current technological limitations.

[0003] Covalent organic framework compounds (COFs) are a class of emerging crystalline organic polymers with inherent porosity, structural periodicity, and light element composition, which construct covalently connected periodic two-dimensional or three-dimensional extended frameworks through organic units. COF materials have achieved rapid development due to their diverse structures, high porosity, high chemical stability, and high theoretical capacity. Most traditional COF material research focuses on 2D COFs, because their layered structures, rich active sites, high porosity, and clear channels are beneficial to the transfer and insertion / extraction of charges and lithium ions. However, the actual specific capacity of 2D COF materials is not ideal in practical applications. Yang et al. designed and prepared the COF-TRO cathode material and used it in all-solid-state organic lithium-ion batteries. The results showed that the reversible specific capacity of COF-TRO reached 268 mAh g -1 , almost reaching 97.5% of the theoretically calculated capacity. In addition, COF-TRO has excellent cycle stability (the capacity retention rate is 99.9% after cycling 100 times at 0.1 °C), which indicates that the COF based on triphenylene ketone has great potential in energy storage applications. However, its reversible capacity is not high, and the cycle stability and utilization rate of active sites need to be further improved. Therefore, it is necessary to develop a high actual specific capacity and strong structural stability, as well as to explore high-quality synthesis methods for the development of conjugated two-dimensional COFs, especially for the application of COF materials in the field of organic cathode materials for lithium-ion batteries, which has practical significance. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and provide an application of a triindenoanthrone-based two-dimensional covalent organic framework material as a cathode material for lithium-ion batteries. The prepared triindenoanthrone-based two-dimensional covalent organic framework material exhibits a fully conjugated single crystal structure, and is rich in a large number of electrochemically active conjugated carbonyl groups and carbon-nitrogen double bonds, which can provide a high density of redox active sites. As an electrode active material in lithium-ion batteries, it shows a high reversible specific capacity, excellent cycle stability and rate performance, and has potential application value in organic electrode materials.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] The first aspect of the present invention is to provide an application of a triindenoanthrone-based two-dimensional covalent organic framework material as a cathode material for lithium-ion batteries. The triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF) has the following structural formula:

[0007]

[0008] The second aspect of the present invention is to provide a triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF) with the above structure.

[0009] The third aspect of the present invention is to provide a preparation method of the above triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF), including the following steps:

[0010] (1) Put triindenoanthrone-triamine and 1,3,5-benzenetricarboxaldehyde in a flask according to a molar ratio of 1-5:1-5;

[0011] (2) Prepare a certain amount of mixed organic solvent, and then pour the powder in step (1) into the prepared mixed solvent, and disperse it fully by ultrasonic treatment;

[0012] (3) Add a certain amount of acidic catalyst to the mixed solution in step (2), and then carry out degassing by cycling liquid nitrogen freezing - vacuum pumping - thawing, and react at 130-160 °C for 3-4 days to obtain a suspension;

[0013] (4) After the suspension is cooled to room temperature, filter and collect the precipitate, and then carry out washing purification and vacuum drying treatment to obtain the triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF).

[0014] Furthermore, the organic solvent is a high-boiling solvent; the boiling point range is 70-170 °C; preferably one or more of mesitylene, 1,4-dioxane, toluene, chlorobenzene, pyridine and cyclohexanone. More preferably, the organic solvent is composed of mesitylene and 1,4-dioxane mixed in a volume ratio of 1:1.

[0015] Further, the acidic catalyst is one or more of acetic acid, trifluoroacetic acid, sulfuric acid, and propionic acid. Preferably, the acidic catalyst is acetic acid with a concentration of 6 mol / L, and the volume ratio of acetic acid to the organic solvent is 1:10.

[0016] Further, the washing liquids used in the washing treatment are dichloromethane, ethanol, acetone, and tetrahydrofuran in sequence.

[0017] Further, the purification method further includes Soxhlet extraction.

[0018] Further, the drying treatment is vacuum drying at 60 - 90 °C for 12 - 30 h.

[0019] The fourth aspect of the present invention is to provide a cathode material for a lithium-ion battery, which is the above-mentioned triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material.

[0020] The fifth aspect of the present invention is to provide a positive electrode sheet, which is prepared by mixing the above-mentioned triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material, conductive carbon, and binder in a mass ratio of 5:4:1.

[0021] The sixth aspect of the present invention is to provide a lithium-ion battery. The positive electrode is prepared by mixing the triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material, conductive carbon, and binder in a mass ratio of 5:4:1. The matching negative electrode is a lithium sheet. In the matching electrolyte, the organic solvent is composed of ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1, and the solute is lithium bis(trifluoromethanesulfonyl)imide with a concentration of 1 mol / L.

[0022] The invention provides a preparation method of a lithium-ion cathode material based on a 3-connected planar ligand two-dimensional covalent organic framework (2D COF) material, which can effectively solve the problem that the actual specific capacity of 2D COFs materials in practical applications is not ideal, thus affecting their actual electrochemical performance. The present invention uses two 3-connected planar organic ligands, and this kind of highly planar organic monomer can promote the π-π stacking between molecules of the COFs material, and the formed lamellar structure has uniformly distributed and fully exposed active sites, which can be fully utilized, so that a COFs material with high crystallinity, high specific capacity, and good stability can be obtained.

[0023] The two building units of 3-connected triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxalineamine and aryl aldehyde selected in the present invention both have a central π-conjugated planar structure. The formed triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material has a fully conjugated planar configuration, which is beneficial to charge transfer and can also maintain the stability of the three-dimensional framework. The two building units have a relatively high nitrogen content and a large number of benzene rings, as well as a large number of uniformly distributed imine bonds in the structure, which can provide rich lithium storage active sites and can be fully utilized while having good stability, thus obtaining excellent lithium storage performance.

[0024] The focus of the present invention is to use a 3-connected triindenoanthrone-based ligand and a 3-connected aryl aldehyde-based ligand to prepare a 2D [3+3] COF material through a Schiff base reaction as a cathode active material for lithium-ion batteries. By exploring a synthetic method for highly crystalline 2D COFs through highly connected planar building blocks, it promotes the development of the synthesis of COF materials with novel topological structures using highly connected building blocks, greatly enriching the types of 2D COFs.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) The present invention proposes a preparation method for a lithium-ion cathode material of a triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF) cathode material. Through 3-connected 2D highly connected building blocks, and then through solvothermal synthesis of a two-dimensional topological structure and highly connected permanent pores 2D COF, it can be used as a lithium-ion cathode material, and also provides the possibility for the enrichment and application of 2D COF materials in various fields.

[0027] (2) The 2D COF lithium-ion battery cathode material prepared by the present invention is different from the existing COFs electrode materials with high theoretical capacity but low actual specific capacity. The novel fully conjugated 2D COF material synthesized by the unique planar ligand of this material has uniformly distributed rich active sites, and the fully conjugated planar framework structure has excellent thermal stability and chemical stability, thus exhibiting a high specific capacity.

[0028] (3) The present invention proposes a preparation method for a lithium-ion cathode material of a triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF) cathode material. Compared with the traditional vacuum tube firing preparation method, this preparation method is simple in synthesis, green and environmentally friendly, low in cost and safer. Description of the Drawings

[0029] Figure 1 It is the refined powder X-ray diffraction pattern of the triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention;

[0030] Figure 2 It is the powder X-ray diffraction pattern of the triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Comparative Examples 1-6 of the present invention;

[0031] Figure 3 It is the Fourier transform infrared spectrum of the triindenoanthrone-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention;

[0032] Figure 4For the indeno[1,2-b]fluorene-1-one-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention 13 13C solid nuclear magnetic resonance spectrum;

[0033] Figure 5 For the nitrogen adsorption-desorption isotherm of the indeno[1,2-b]fluorene-1-one-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention;

[0034] Figure 6 For the pore size distribution curve of the indeno[1,2-b]fluorene-1-one-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention;

[0035] Figure 7 For the high-magnification transmission electron microscopy image and selected area electron diffraction pattern of the indeno[1,2-b]fluorene-1-one-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention;

[0036] Figure 8 For the galvanostatic charge-discharge curve (0.2C) of the indeno[1,2-b]fluorene-1-one-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention;

[0037] Figure 9 For the cycle stability diagram (0.05 - 0.2C) of the indeno[1,2-b]fluorene-1-one-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention;

[0038] Figure 10 For the rate performance diagram (0.2 - 3C) of the indeno[1,2-b]fluorene-1-one-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared in Example 1 of the present invention. Detailed implementation manners

[0039] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0040] The present invention will be further described below in conjunction with specific examples and drawings.

[0041] Example 1

[0042] The specific preparation steps of an indeno[1,2-b]fluorene-1-one-based two-dimensional covalent organic framework material (TRO-BT-COF) are as follows:

[0043] (1) Add 32 mg of triphenylene ketone - triamine and 12.16 mg of benzene - 1,3,5 - tricarbaldehyde into a 10 mL flask, then add a mixed solution of mesitylene and 1,4 - dioxane (with a volume ratio of 0.5 mL:0.5 mL). After ultrasonic dissolution, add it into 0.1 mL of acetic acid aqueous solution with a concentration of 6 mol / L.

[0044] (2) Freeze - vacuum - thaw the above reaction system three times in liquid nitrogen for degassing treatment. Seal the reaction mixture in an oil - bath pot and heat it to 150 °C with stirring for 3 days.

[0045] (3) After the reaction is completed, cool it to room temperature. Filter the obtained mixture to collect the solid, then wash it with dichloromethane, ethanol, acetone and tetrahydrofuran. In addition, perform Soxhlet extraction for 3 days to further purify the product. Finally, vacuum - dry it at 80 °C for 24 h to obtain a dark - red powder of triphenylene ketone - based two - dimensional covalent organic framework material (TRO - BT - COF).

[0046] Figure 1 The XRD refinement results show that the theoretical calculation results of AA stacking correspond one - to - one with the experimental results, proving that the structure of the obtained triphenylene ketone - based two - dimensional covalent organic framework material (TRO - BT - COF) is indeed as shown in formula (Ι). The results show that this material exhibits high crystallinity.

[0047] Figure 3 The infrared spectrum of the triphenylene ketone - based two - dimensional covalent organic framework material (TRO - BT - COF) shows characteristic peaks at 1650 cm -1 (corresponding to the stretching vibration peak of the C=N group) and 1690 cm -1 (corresponding to the stretching vibration peak of the C=O group), proving the formation of imine bonds and the existence of carbonyl groups, indicating that the Schiff base reaction has occurred.

[0048] Figure 4 The 13 13C solid - state NMR spectrum of the triphenylene ketone - based two - dimensional covalent organic framework material (TRO - BT - COF) is shown. The results show that chemical shifts at 152.21 and 190 ppm can be observed in the carbon NMR spectrum, indicating the formation of imine bonds and the existence of carbonyl groups, and once again proving the successful polymerization of the two monomers.

[0049] Figure 5 , Figure 6 The nitrogen adsorption - desorption isotherm and pore - size distribution curve of the obtained triphenylene ketone - based two - dimensional covalent organic framework material (TRO - BT - COF) are shown. The results show that the prepared triphenylene ketone - based two - dimensional covalent organic framework material has a hierarchical porous structure. The specific surface area of the triphenylene ketone - based two - dimensional covalent organic framework material (TRO - BT - COF) is 62.1739 m 2 g-1 , the pore size distribution is concentrated at 1.8 nm;

[0050] Figure 7 (a) in shows the HRTEM image of the obtained triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material (TRO-BT-COF). The results show that the triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material (TRO-BT-COF) has a lamellar morphology, Figure 7 (b) in shows the selected area electron diffraction pattern of the obtained triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material (TRO-BT-COF). The results show that the diffraction spots of the triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material (TRO-BT-COF) are arranged in an ordered array, proving its single crystal structure.

[0051] Application of the triindeno[1,2-b:2',1'-d:1'',2''-f]quinoxaline-based two-dimensional covalent organic framework material (TRO-BT-COF) prepared by the present invention in lithium ion batteries.

[0052] (1) According to the amount of active material: conductive carbon: binder = 5:4:1, first weigh 0.025 g of DAAQ-TFPCOF powder and 0.02 g of Ketjenblack (ECP-600JD) and put them into a mortar and grind for 30 minutes. Then pour the ground mixed powder into a glass bottle containing 0.005 g of powdered polytetrafluoroethylene, and knead it into a shiny ball with a spatula repeatedly. Roll it into a round sheet with a size of 10 mm, and evenly roll it onto a titanium mesh with a diameter of 10 mm. Dry it under vacuum at 80 °C for more than 12 h to fully volatilize the solvent, and obtain a positive electrode plate.

[0053] (2) Assemble the battery with the prepared positive electrode plate in a glove box filled with argon (w(H2O) ≤ 0.1 ppm, w(O2) ≤ 0.1 ppm): the positive electrode plate is the working electrode, and the high-purity lithium sheet is the counter electrode; celgard 2400 is the separator; in the electrolyte, the organic solvent is obtained by mixing ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of DME:DOL = 1:1, and the solute is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) with a concentration of 1 mol / L. Assemble a CR2032 coin cell under a pressure of 1 Mpa. The voltage setting range is 1 - 3.5 V.

[0054] (3) Description of test conditions

[0055] At room temperature, the battery is left standing overnight, first activated at 0.05 C for 50 cycles, and then cycled at 0.2 C for 350 cycles for cycle performance testing; at rates of 0.2, 0.5, 1, 2, and 3 C respectively, rate performance testing is carried out.

[0056] Figure 8It is shown that the tribenzotriindeno[1,2-b:1',2'-d:1'',2''-f]azulen-6-one-based two-dimensional covalent organic framework material (TRO-BT-COF) has a discharge specific capacity of 445 mAh g -1 , accounting for 99.1% of the theoretical capacity.

[0057] Figure 9 It is shown that for the battery with the tribenzotriindeno[1,2-b:1',2'-d:1'',2''-f]azulen-6-one-based two-dimensional covalent organic framework material (TRO-BT-COF) as the cathode material, after 400 cycles, the theoretical capacity retention rate is 84.5%, indicating good cycle stability.

[0058] Figure 10 It reflects the rate performance of the battery, demonstrating its excellent rate performance and structural stability.

[0059] Comparative Example 1

[0060] The difference from Example 1 is that the concentration of acetic acid is 5 mol / L.

[0061] Comparative Example 2

[0062] The difference from Example 1 is that the concentration of acetic acid is 7 mol / L.

[0063] Comparative Example 3

[0064] The difference from Example 1 is that in step (2), the reaction is carried out at 120 °C for 3 days.

[0065] Comparative Example 4

[0066] The difference from Example 1 is that in step (2), the reaction is carried out at 170 °C for 3 days.

[0067] Comparative Example 5

[0068] The difference from Example 1 is that in step (2), the reaction is carried out at 150 °C for 2 days.

[0069] Comparative Example 6

[0070] The difference from Example 1 is that in step (2), the reaction is carried out at 150 °C for 5 days.

[0071] Figure 2 XRD comparison diagrams of the tribenzotriindeno[1,2-b:1',2'-d:1'',2''-f]azulen-6-one-based two-dimensional covalent organic framework material (TRO-BT-COF) obtained under different experimental conditions are shown. By regulating the concentration of acetic acid solution, reaction temperature and reaction time, it is found that when the acetic acid concentration is 5 M and 7 M, no obvious COF diffraction peaks appear, indicating that the COF structure is not formed under this condition; when the reaction temperature is 120 °C and 170 °C, the diffraction peaks are all amorphous structures, indicating that the COF structure is not formed under this condition; when the reaction time is 2 and 5 days, the diffraction peaks are relatively weak, especially the small-angle diffraction peaks are very unclear, indicating that the COF crystallinity is poor under this condition.

[0072] In this specification, for the same or similar parts among various embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and for the relevant parts, reference can be made to the partial description of the foregoing embodiments.

[0073] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of them. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Application of a triphenylene ketone-based two-dimensional covalent organic framework material as a cathode material for a lithium-ion battery, characterized in that: The indeno[1,2-b:3,4-b':5,6-b'']triindenone-based two-dimensional covalent organic framework material has the structure shown in formula (Ι): Both of the two building units, the 3-connected indeno[1,2-b:3,4-b':5,6-b'']triindenone amine and aryl aldehyde, have a central π-conjugated planar structure, and the indeno[1,2-b:3,4-b':5,6-b'']triindenone-based two-dimensional covalent organic framework material formed by the two has a fully conjugated planar configuration.

2. The application according to claim 1, characterized in that, The positive electrode plate is prepared by mixing the indeno[1,2-b:3,4-b':5,6-b'']triindenone-based two-dimensional covalent organic framework material, conductive carbon and binder in a mass ratio of 5:4:

1.

3. The application according to claim 2, wherein The matching negative electrode is a lithium sheet. In the matching electrolyte, the organic solvent is composed of 1,2-dimethoxyethane and 1,3-dioxolane in a volume ratio of 1:1, and the solute is lithium bis(trifluoromethanesulfonyl)imide with a concentration of 1 mol / L.

4. An indeno[1,2-b:3,4-b':5,6-b'']triindenone-based two-dimensional covalent organic framework material has the structure shown in formula (Ι):

5. A method for preparing the triphenylene ketone-based two-dimensional covalent organic framework material according to claim 4, characterized in that, The indeno[1,2-b:3,4-b':5,6-b'']triamine and benzene-1,3,5-tricarbaldehyde are added to the organic solvent in a molar ratio of 1-5:1-5, and ultrasonic treatment is performed to make them fully dispersed. Then, an acidic catalyst is added, and after degassing by cycling liquid nitrogen freezing-vacuum pumping-thawing, the reaction is carried out at 130-160 °C for 3-4 days to obtain a suspension; after the suspension is cooled to room temperature, the precipitate is collected by filtration, washed, purified and dried repeatedly to obtain the indeno[1,2-b:3,4-b':5,6-b'']triindenone-based two-dimensional covalent organic framework material. The acidic catalyst is acetic acid with a concentration of 6 mol / L, and the volume ratio of acetic acid to the organic solvent is 1:

10.

6. The preparation method according to claim 5, characterized in that, The organic solvent is one or more of mesitylene, 1,4-dioxane, toluene, chlorobenzene, pyridine and cyclohexanone.

7. The preparation method according to claim 6, characterized in that, The organic solvent is composed of mesitylene and 1,4-dioxane in a volume ratio of 1:

1.

8. The preparation method according to claim 5, characterized in that, After degassing, the reaction is carried out at 150 °C for 3 days to obtain a suspension.

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