Covalent organic framework polymer with integrated organic-inorganic active sites, preparation method thereof and lithium ion battery cathode material

Abstract

The application belongs to the technical field of lithium ion batteries, and discloses an organic-inorganic active site integrated covalent organic framework polymer, and a preparation method thereof, which comprises the following steps: 2,5-dihydroxyterephthaldehyde, 2,3,5,6-tetrakis(amino) p-benzoquinone and copper acetate monohydrate are condensed into the organic-inorganic active site integrated covalent organic framework polymer through Schiff base reaction. The organic-inorganic active site integrated covalent organic framework polymer material prepared by the application has rich organic active groups (C=O and C=N), and the Cu 2+ in the structure also has redox activity and can store lithium ions as inorganic active sites, thereby effectively increasing the specific capacity of lithium ions in the battery; in addition, the extended pi-d conjugated structure of the Cu-COF can effectively promote the rapid transfer of electrons and enhance the rate performance of the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to an organic-inorganic active site integrated covalent organic framework polymer, a preparation method thereof, a lithium ion battery positive electrode material, a lithium ion battery positive electrode sheet and a lithium ion battery. BACKGROUND

[0002] With the continuous growth of global energy demand, the finiteness of traditional fossil fuels and environmental pollution problems are increasingly prominent, prompting researchers to continue to explore new clean energy materials. Among many new energy materials, lithium ion batteries have become a research hotspot due to their high energy density and long cycle life. However, traditional inorganic positive electrode materials such as lithium-containing transition metal oxides, phosphides (such as lithium cobaltate LiCoO2, lithium nickelate LiNiO2, lithium iron phosphate LiFePO4) have problems such as resource shortage, high cost, environmental hazards and the like. Therefore, in order to guarantee energy demand, promote the development of new energy industry and promote the concept of sustainable development, it is of great significance to develop a new generation of green high-performance lithium ion battery positive electrode materials.

[0003] Compared with inorganic positive electrode materials, organic positive electrode materials have advantages such as abundant raw materials, green environmental protection and easy structure control, and are a class of green positive electrode materials with great application potential. Among them, covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with regular pore structure and flexible structure controllability, and have shown great application potential in the research of lithium ion battery electrode materials in recent years. SUMMARY

[0004] The present application aims at the above technical problems, and provides an organic-inorganic active site integrated covalent organic framework polymer and a preparation method thereof, and a lithium ion battery positive electrode material, a lithium ion battery positive electrode sheet and a lithium ion battery prepared by using the same. The material has abundant organic active groups (C=O and C=N), and the Cu 2+ in the structure thereof also has redox activity and can store lithium ions as inorganic active sites, effectively increasing the specific capacity of lithium ions in the battery; in addition, the extended pi-d conjugated structure of the Cu-COF can effectively promote the rapid transfer of electrons and enhance the rate performance of the battery.

[0005] To achieve the above purpose, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides an organic-inorganic active site integrated covalent organic framework polymer, which contains quinone, imine and Cu 2+The active site is formed by the conjugation of the d-orbital electrons of the transition metal copper ion and the pi electrons of the organic group, and an extended pi-d conjugated structure is formed in the two-dimensional plane, as shown in the following formula:

[0007]

[0008] In a second aspect, the present application provides a preparation method of the above-mentioned organic-inorganic active site integrated covalent organic framework polymer, comprising the following steps: condensing 2,5-dihydroxyterephthaldehyde, 2,3,5,6-tetraaminop-benzoquinone and copper acetate monohydrate by Schiff base reaction.

[0009] In one technical solution, the above-mentioned preparation method specifically comprises the following steps: adding 2,5-dihydroxyterephthaldehyde, 2,3,5,6-tetraaminop-benzoquinone and copper acetate monohydrate into an autoclave, then adding a reaction solvent, sealing the autoclave, and carrying out hydrothermal reaction at 100-150 DEG C for 48-96 hours; after the reaction is completed, filtering and washing the reaction product, and vacuum drying to obtain a red-black solid powder.

[0010] In one technical solution, the above-mentioned preparation method comprises the following steps: adding 2,5-dihydroxyterephthaldehyde, 2,3,5,6-tetraaminop-benzoquinone and copper acetate monohydrate into an autoclave, then adding a reaction solvent, sealing the autoclave, and carrying out hydrothermal reaction at 100-150 DEG C for 48-96 hours; after the reaction is completed, filtering and washing the reaction product, and vacuum drying to obtain a red-black solid powder.

[0011] In one technical solution, the above-mentioned preparation method comprises the following steps: adding 2,5-dihydroxyterephthaldehyde, 2,3,5,6-tetraaminop-benzoquinone and copper acetate monohydrate into an autoclave, then adding a reaction solvent, sealing the autoclave, and carrying out hydrothermal reaction at 100-150 DEG C for 48-96 hours; after the reaction is completed, filtering and washing the reaction product, and vacuum drying to obtain a red-black solid powder.

[0012] In one technical solution, the above-mentioned preparation method comprises the following steps: adding 2,5-dihydroxyterephthaldehyde, 2,3,5,6-tetraaminop-benzoquinone and copper acetate monohydrate into an autoclave, then adding a reaction solvent, sealing the autoclave, and carrying out hydrothermal reaction at 100-150 DEG C for 48-96 hours; after the reaction is completed, filtering and washing the reaction product, and vacuum drying to obtain a red-black solid powder.

[0013] In a fourth aspect, the present application provides a lithium ion battery positive electrode sheet, which is coated with a mixed slurry composed of the above-mentioned organic-inorganic active site integrated covalent organic framework polymer, Ketjen black and polyvinylidene fluoride.

[0014] In one technical solution, the mass ratio of the covalent organic framework polymer, Ketjen black and polyvinylidene fluoride is 5-7:2-4:1.

[0015] In a fifth aspect, the present application provides a lithium ion battery, the positive electrode sheet of which is coated with a mixed slurry composed of the above-mentioned organic-inorganic active site integrated covalent organic framework polymer, Ketjen black and polyvinylidene fluoride.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] 1) Compared with traditional covalent organic frameworks, the covalent organic framework polymer Cu-COF designed and synthesized in the application not only has rich organic active groups (C=O and C=N), but also has redox activity in the structure, can store lithium as inorganic active sites, and can perform multi-electron transfer reaction as a positive electrode material of lithium ion battery, effectively increasing the specific capacity of the battery. In addition, the electrons of the d orbit of the transition metal copper ion and the π electrons of the organic group form an extended π-d conjugated structure in the two-dimensional plane, which helps the high delocalization of electrons and enhances the electron conduction ability, effectively promotes the rapid transfer of electrons and enhances the rate performance of the battery. 2+ 13 2) Compared with the traditional solvent thermal synthesis method of covalent organic framework materials, the covalent organic framework polymer Cu-COF of the application is synthesized by one-pot method using a hydrothermal kettle, without freezing-vacuumizing-thawing treatment, and the operation steps are more simple and the reaction conditions are more mild.

[0018] 3) Compared with traditional covalent organic framework materials, the covalent organic framework polymer Cu-COF of the application has a large specific surface area, which is beneficial to the storage of lithium ions and the transfer of electrons. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 FIG. 1 is an X-ray diffraction spectrum of Cu-COF prepared in Example 1 of the application.

[0020] Figure 2 FIG. 2 is an infrared absorption spectrum of Cu-COF prepared in Example 1 of the application.

[0021] Figure 3 FIG. 3 is a C solid-state NMR spectrum of Cu-COF prepared in Example 1 of the application. 13

[0022] Figure 4 FIG. 4 is a rate performance graph of a lithium ion battery assembled by a Cu-COF positive electrode sheet prepared in Example 4 of the application.

[0023] Figure 5 FIG. 5 is a cycle capacity graph of a lithium ion battery assembled by a Cu-COF positive electrode sheet prepared in Example 4 of the application at 2 A g -1 DETAILED DESCRIPTION

[0024] The following examples are used to illustrate the application, but are not used to limit the protection scope of the application. If not specifically indicated, the technical means used in the examples is the conventional means known to those skilled in the art. The test methods in the following examples are conventional methods, unless otherwise specified.

[0025] Example 1

[0026] ​2,5-Dihydroxyterephthalaldehyde (HBC, 49.8 mg), 2,3,5,6-tetra(amino)-p-benzoquinone (TABQ, 25.2 mg), and excess copper acetate monohydrate (Cu(OAc)₂·H₂O, 119.8 mg) were added to a 25 mL hydrothermal reactor, followed by the addition of 3 mL of 1,4-dioxane and 1 mL of mesitylene solvent. The resulting solution was sonicated for half an hour, the hydrothermal reactor was sealed, and the reaction was carried out at 120 °C for 72 h. After the reaction was completed, the mixture was automatically cooled to room temperature, filtered, and repeatedly washed with DMF, methanol, and THF. Finally, the product was vacuum dried at 80 °C for 12 h to obtain a reddish-black solid powder, denoted as Cu-COF. The preparation route of Cu-COF is shown below:

[0027]

[0028] The Cu-COF prepared in Example 1 was subjected to XRD testing, and the results are as follows: Figure 1 As shown by the yellow line, three distinct characteristic peaks can be observed, indicating that the Cu-COF material synthesized in Example 1 is a well-crystallized covalent organic framework material.

[0029] The Cu-COF prepared in Example 1 was subjected to infrared absorption spectroscopy. The infrared absorption spectrum is as follows: Figure 2 As shown in the infrared absorption spectrum of Cu-COF, the NH and -OH bonds are located at 3370 and 3279 cm⁻¹, respectively. -1 The disappearance of the characteristic peak at 1654 cm⁻¹ indicates that the reaction proceeds fully via the one-pot method. Furthermore, the infrared absorption spectrum of Cu-COF shows that at 1654 cm⁻¹... -1 and 1570cm -1 And 548cm -1 and 507~517cm -1 The absorption peaks observed at the positions correspond to the stretching vibration peaks of C=O and the linking group C=N, as well as -Cu-N and -Cu-O, respectively, further verifying the successful synthesis of Cu-COF.

[0030] The Cu-COF material prepared in Example 1 was subjected to... 13 C solid-state NMR spectroscopy, such as Figure 3 As shown in the image, the spectrum exhibits a characteristic carbonyl (C=O) signal at 197.4 ppm and a unique resonance signal of an imine (C=N) bond at 177.5 ppm, confirming the formation of an imine bond.

[0031] Example 2

[0032] 2,5-dihydroxyterephthaldehyde (HBC, 49.8 mg), 2,3,5,6-tetraamino-p-benzoquinone (TABQ, 25.2 mg) and excess copper acetate monohydrate (Cu(OAc)2.H2O, 89.9 mg) were added into a 25 mL autoclave, followed by 3 mL of 1,4-dioxane and 1 mL of mesitylene solvent. The resulting solution was sonicated for half an hour, the autoclave was sealed and reacted at 120 °C for 72 h. After the reaction, the autoclave was allowed to cool to room temperature, filtered and washed repeatedly with DMF, methanol and THF. Finally, the product was vacuum dried at 80 °C for 12 h to obtain a red-black solid powder, whose XRD spectrum is shown in Figure 2. Figure 1 The middle blue line.

[0033] Example 3

[0034] 2,5-dihydroxyterephthaldehyde (HBC, 49.8 mg), 2,3,5,6-tetraamino-p-benzoquinone (TABQ, 25.2 mg) and excess copper acetate monohydrate (Cu(OAc)2.H2O, 149.8 mg) were added into a 25 mL autoclave, followed by 3 mL of 1,4-dioxane and 1 mL of mesitylene solvent. The resulting solution was sonicated for half an hour, the autoclave was sealed and reacted at 120 °C for 72 h. After the reaction, the autoclave was allowed to cool to room temperature, filtered and washed repeatedly with DMF, methanol and THF. Finally, the product was vacuum dried at 80 °C for 12 h to obtain a red-black solid powder, whose XRD spectrum is shown in Figure 2. Figure 1 The middle purple line.

[0035] Example 4 Preparation of lithium-ion battery anode sheet using Cu-COF

[0036] 60 mg of Cu-COF prepared in Example 1, 30 mg of Ketjen black and 10 mg of polyvinylidene fluoride were weighed and then mixed in a corundum mortar to obtain a slurry with a suitable viscosity by adding 500 mL of NMP. The prepared mixed slurry was uniformly coated on a carbon-coated aluminum foil with a thickness of 500 μm, and the coated aluminum foil was placed in a vacuum oven at 60 °C for drying overnight. The dried aluminum foil was cut into a circular anode sheet with a diameter of 12 mm using a manual sheet cutter. Finally, the cut anode sheet was transferred to a glove box for use.

[0037] Example 5 Assembly of lithium-ion battery

[0038] The Cu-COF anode sheet prepared in Example 4 was used as the anode, a lithium metal sheet was used as the cathode, and a commercial polypropylene (PP) separator was used as the separator. When assembling the battery, the electrolyte composition was 1.0 M LiTFSI (DOL:DME = 1:1), and a CR2032 battery shell was selected. After assembly, the battery was compacted on a tablet press and allowed to stand for a certain period of time before performing electrochemical performance testing.

[0039] The lithium ion battery prepared in Example 5 was subjected to electrochemical test at different current densities, and the results are shown in Figure 4 At the current densities of 0.25, 0.5, 1.0, 2.0 A g -1 , the discharge capacities were 271, 250, 235, 222 mAh g -1 , respectively, exhibiting high initial capacity and excellent rate performance. The high initial capacity is attributed to the synergistic effect between the organic active sites (quinone, imine) and the inorganic active sites (Cu 2+ in the material, and the excellent rate performance is due to the conjugation between the d-orbital electrons of the transition metal copper ions and the π-electrons of the organic groups, forming an extended π-d conjugated structure in the two-dimensional plane, which promotes the high delocalization of electrons and realizes the rapid transfer of electrons, thus exhibiting excellent rate performance.

[0040] The lithium ion battery prepared in Example 5 was subjected to long cycle test at a large current density of 2 A g -1 , and the results are shown in Figure 5 The initial capacity at the current density of 2 A g -1 was 222 mAh g -1 , and after 200 cycles, the capacity remained at 169 mAh g -1 , with a capacity retention rate of 76.1%.

[0041] In summary, the present application uses 2,5-dihydroxyterephthaldehyde (HBC) and 2,3,5,6-tetra(aminophenyl)quinone (TABQ) as organic ligands, and introduces copper acetate monohydrate (Cu(OAc)2﹒H2O) to participate in the polycondensation reaction, and through molecular design, a covalent organic framework (Cu-COF) with ordered porous structure is constructed. Unlike traditional COF electrode materials, the Cu-COF designed and synthesized in the present application not only has rich organic active groups (C=O and C=N), but also the Cu 2+ in its structure has redox activity and can store lithium ions as inorganic active sites, effectively increasing the specific capacity of the battery. In addition, the extended π-d conjugated structure of the Cu-COF can effectively promote the rapid transfer of electrons, enhancing the rate performance of the battery.

[0042] The above-described embodiments are only preferred embodiments of the present application, merely used to explain the present application, and are not intended to limit the scope of the present application. For those skilled in the art, of course, other embodiments can be easily made by substitution or change based on the technical content disclosed in the present specification, and therefore, any changes and improvements made on the principles of the present application shall be included in the scope of the patent application.

Claims

1. An organo-inorganic active site integrated covalent organic framework polymer, characterized in that, The covalent organic framework polymer contains quinone, imine and Cu 2+ Active site, whose structural formula is as follows:

2. The method for preparing the organic-inorganic active site-integrated covalent organic framework polymer according to claim 1, characterized in that, The method comprises the following steps: The 2,5-dihydroxy terephthaldehyde, 2,3,5,6-tetra (amino) p-benzoquinone and copper acetate monohydrate are condensed by Schiff base reaction.

3. The production method according to claim 2, characterized by, The method comprises the following steps: The 2,5-dihydroxy terephthaldehyde, 2,3,5,6-tetra (amino) p-benzoquinone and copper acetate monohydrate are added into a hydrothermal kettle, and then a reaction solvent is added, the hydrothermal kettle is sealed, and hydrothermal reaction is carried out at 100-150 DEG C for 48-96 hours; after the reaction is completed, the reaction product is filtered and washed, and vacuum drying is carried out to obtain a red-black solid powder.

4. The production method according to claim 2 or 3, characterized by, The molar ratio of the 2,5-dihydroxy terephthaldehyde, 2,3,5,6-tetra (amino) p-benzoquinone and copper acetate monohydrate is 2:1:2-6.

5. The production method according to claim 2 or 3, characterized by, The reaction solvent is a mixture of mesitylene and 1,4-dioxane.

6. A lithium-ion battery cathode material, characterized in that, The lithium ion battery positive electrode material contains the organic-inorganic active site integrated covalent organic framework polymer of claim 1.

7. A lithium-ion battery cathode electrode sheet, characterized by, The lithium ion battery positive electrode sheet is coated with a mixed slurry composed of the organic-inorganic active site integrated covalent organic framework polymer of claim 1, ketchen black and polyvinylidene fluoride.

8. The lithium-ion battery cathode electrode sheet according to claim 7, wherein, The mass ratio of the covalent organic framework polymer, ketchen black and polyvinylidene fluoride is 5-7:2-4:

1.

9. A lithium-ion battery, characterized by The lithium ion battery positive electrode sheet is coated with a mixed slurry composed of the organic-inorganic active site integrated covalent organic framework polymer of claim 1, ketchen black and polyvinylidene fluoride.

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