Covalent organic framework material, negative active material, negative pole piece and secondary battery

Abstract

The invention provides a covalent organic framework material, a negative active material, a negative pole piece and a secondary battery. The covalent organic framework material comprises a structural unit A and a structural unit B which are bonded, X1, X2 and X3 in the structural unit A are independently selected from S or Se, and the structural unit B is selected from and / or. STRUCTURAL UNIT A

Description

TECHNICAL FIELD

[0001] The present application relates to the field of organic materials, in particular to a covalent organic framework material, a negative active material, a negative electrode sheet and a secondary battery. BACKGROUND

[0002] Lithium ion batteries, as an important energy storage technology, are widely used in electric vehicles, energy storage power stations, consumer electronics and many other fields, and play an increasingly important role in today's society. The main components of lithium ion batteries include positive electrode sheets, negative electrode sheets, electrolytes and separators, among which the positive active materials and negative active materials in the positive electrode sheets and negative electrode sheets are the core that determines the performance of the battery.

[0003] Inorganic transition metal oxide materials are currently the mainstream commercial positive electrode materials for lithium ion batteries, but they have major problems such as non-renewability, high price, serious environmental pollution and limited theoretical capacity, making it increasingly difficult to meet the demand for green and high-performance electrode materials in society.

[0004] Organic electrode materials have attracted widespread attention due to their abundant resources, environmental friendliness and high designability. Some organic materials have the characteristics of being more stable in solvated state than in solid aggregated state, but they will face the problem of internal molecular arrangement in a disordered state, resulting in poor electrochemical performance, and the batteries tested during the charging and discharging process often result in significant performance degradation. SUMMARY

[0005] The present application provides a covalent organic framework material, a negative active material, a negative electrode sheet and a secondary battery, which provides better rate performance and cycle performance for the secondary battery.

[0006] The first aspect of the present application provides a covalent organic framework material, which comprises bonded structural units A and structural units B,

[0007]

[0008] Structural unit A

[0009] wherein X 1 , X 2 , X 3 are each independently selected from S or Se, and the structural unit B is selected from and / or .

[0010] In any embodiment of the first aspect, the crystal structure of the covalent organic framework material belongs to the P3 space group.

[0011] In any embodiment of the first aspect, the interlayer spacing of the covalent organic framework in the covalent organic framework material is greater than 3.5 nm.

[0012] In any embodiment of the first aspect, the pore size of the covalent organic framework material is concentrated below 4 nm.

[0013] In any embodiment of the first aspect, X 1 , X 2 , X 3 are all S or all Se.

[0014] In any embodiment of the first aspect, the covalent organic framework material comprises the following structure:

[0015] .

[0016] The second aspect of the present application provides a negative electrode active material, which comprises the covalent organic framework material provided in any embodiment of the first aspect.

[0017] The third aspect of the present application provides a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material, and the negative electrode active material comprising the covalent organic framework material provided in any embodiment of the first aspect.

[0018] In any embodiment of the third aspect, the weight content of the covalent organic framework material in the negative electrode film layer is 60%-80%.

[0019] In any embodiment of the third aspect, the negative electrode film layer further comprises a conductive agent and a binder, and the weight ratio of the covalent organic framework material, the conductive agent and the binder is (6-8):(3-1):1.

[0020] The fourth aspect of the present application provides a secondary battery, which comprises a negative electrode sheet, and the negative electrode sheet comprises the negative electrode sheet provided in any embodiment of the third aspect.

[0021] The covalent organic framework material provided in the application contains a sulfur atom-doped jaculene structure, the bowl-shaped structure of the jaculene expands the interlayer spacing of the covalent organic framework material, and forms a multi-dimensional ion channel; the doped S element or Se element provides a high-density, strongly active ion active adsorption site, which is beneficial to the efficient transmission of internal molecular electrons and improves the reaction kinetics; meanwhile, the conjugated framework including the above-mentioned structure unit A and structure unit B inhibits the dissolution of the small molecular jaculene in an organic solvent. In combination of the above effects, the covalent organic framework material has high solvent stability, strong lithium ion conduction and adsorption capacity, and more redox active sites, thereby effectively improving the rate performance and long cycle stability of a secondary battery with the covalent organic framework material. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

[0023] Figure 1 An infrared diffraction spectrum of the covalent organic framework material of Example 1 of the application is shown.

[0024] Figure 2 An infrared diffraction spectrum of the covalent organic framework material of Example 1 of the application is shown. 13 C solid nuclear magnetic test spectrum.

[0025] Figure 3 An infrared diffraction spectrum of the covalent organic framework material of Example 1 of the application is shown. 11 B solid nuclear magnetic test spectrum.

[0026] Figure 4 An XPS B 1s spectrum of the covalent organic framework material of Example 1 of the application is shown.

[0027] Figure 5 An XPS S 2p spectrum of the covalent organic framework material of Example 1 of the application is shown.

[0028] Figure 6 An X-ray diffraction spectrum of the covalent organic framework material of Example 1 of the application is shown.

[0029] Figure 7 An SEM test diagram of the covalent organic framework material of Example 1 of the application is shown.

[0030] Figure 8 A TEM test diagram of the covalent organic framework material of Example 1 of the application is shown.

[0031] Figure 9The N2 adsorption-desorption isotherm (77K) of the covalent organic framework material of Example 1 of this application is shown.

[0032] Figure 10 The pore size distribution curve of the covalent organic framework material of Embodiment 1 of this application is shown.

[0033] Figure 11 The infrared diffraction pattern of the covalent organic framework material of Example 2 of this application is shown.

[0034] Figure 12 The covalent organic framework material of Embodiment 2 of this application is shown. 13 C solid NMR spectrum.

[0035] Figure 13 The covalent organic framework material of Embodiment 2 of this application is shown. 11 B solid-state NMR spectrum.

[0036] Figure 14 The XPS B 1s spectrum of the covalent organic framework material of Example 2 of this application is shown.

[0037] Figure 15 The XPS Se 3d spectrum of the covalent organic framework material of Example 2 of this application is shown.

[0038] Figure 16 The X-ray diffraction pattern of the covalent organic framework material of Example 2 of this application is shown.

[0039] Figure 17 The SEM image of the covalent organic framework material of Example 2 of this application is shown.

[0040] Figure 18 The TEM test image of the covalent organic framework material of Embodiment 2 of this application is shown.

[0041] Figure 19 The nitrogen physisorption curve of the covalent organic framework material of Example 2 of this application is shown.

[0042] Figure 20 The pore size distribution curve of the covalent organic framework material of Embodiment 2 of this application is shown.

[0043] Figure 21 The test results of the solid conductivity of S-sum-COF of Example 2, Se-sum-COF of Example 1, and COF-5 of Comparative Example 1 are shown.

[0044] Figure 22 The results show the capacity test results of the button cell containing the S-sum-COF negative electrode prepared in Example 1 at different rates.

[0045] Figure 23 The results show the capacity test results of the button cell containing the Se-sum-COF negative electrode prepared in Example 2 at different rates.

[0046] Figure 24 The results show the capacity test results of the button cell containing the COF-5 negative electrode sheet prepared in Comparative Example 1 at different rates.

[0047] Figure 25 A 0.2 A·g button cell containing the S-sum-COF negative electrode prepared in Example 1 is shown. -1 Test results of battery capacity at current density.

[0048] Figure 26 A 0.2 A·g button cell containing the Se-sum-COF negative electrode prepared in Example 2 is shown. -1 Test results of capacity at current density.

[0049] Figure 27 A 0.2 A·g button cell containing the COF-5 negative electrode prepared in Comparative Example 1 is shown. -1 Test results of capacity at current density.

[0050] Figure 28 A 2 A·g button cell containing the S-sum-COF negative electrode prepared in Example 1 is shown. -1 Test results of battery capacity at current density.

[0051] Figure 29 A button cell containing the Se-sum-COF negative electrode prepared in Example 2 is shown. (2 A·g) -1 Test results of capacity at current density.

[0052] Figure 30 A 10 A·g coin cell containing the S-sum-COF negative electrode prepared in Example 1 is shown. -1 Test results of battery capacity at current density.

[0053] Figure 31 A 10 A·g coin cell containing the Se-sum-COF negative electrode prepared in Example 2 is shown. -1 Test results of capacity at current density.

[0054] Figure 32 A 10 A·g button cell containing the COF-5 negative electrode prepared in Comparative Example 1 is shown. -1 Test results of capacity at current density. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0057] As mentioned earlier, although organic electrode materials are characterized by abundant resources, environmental friendliness, and high structural designability, the planar conjugated structures of small organic molecules often suffer from unfavorable π-π stacking, leading to structural instability during rapid charge-discharge processes and exhibiting limited redox activity, thus affecting ion transport. Achieving rapid ion transport using organic electrode materials requires structural distortion to suppress interlayer stacking, but such distortion usually sacrifices the activity and conductivity of redox sites. To address this issue, this application develops a covalent organic framework material.

[0058] The first embodiment of this application provides a covalent organic framework material, which includes bonded structural unit A and structural unit B.

[0059]

[0060] Structural Unit A

[0061] Among them, X in structural unit A 1 X 2 X 3 Each is independently selected from S or Se, and structural unit B is selected from... and / or .

[0062] The covalent organic framework material provided in this application includes a chalcogenide-doped jasmine structure. The bowl-shaped structure of jasmine expands the interlayer spacing of the covalent organic framework material, forming multidimensional ion channels. The doped S or Se elements provide high-density, highly active ion adsorption sites, which is beneficial for the efficient transport of electrons within the molecule and improves reaction kinetics. At the same time, the conjugated framework including the aforementioned structural units A and B inhibits the dissolution of small-molecule jasmine in organic solvents. Combining the above effects, this covalent organic framework material simultaneously possesses high solvent stability, strong lithium-ion conductivity and adsorption capacity, and a large number of redox active sites, thereby effectively improving the rate performance and long-cycle stability of secondary batteries containing it.

[0063] In some implementations, the crystal structure of the covalent organic framework material belongs to the P3 space group.

[0064] In some implementations, the interlayer spacing of the covalent organic framework in the covalent organic framework material is greater than 3.5 nm. This is larger than the interlayer spacing of COF materials formed from undoped jasmine.

[0065] In some implementations, the pore size of the covalent organic framework material is concentrated below 4 nm.

[0066] The doping elements in structural unit A can be arbitrarily selected and combined from S and Se. In some embodiments, X in structural unit A... 1 X 2 X 3 All are S or all are Se.

[0067] The structural unit A and structural unit B described above can be connected to form various covalent organic framework structures. In some embodiments, the organic framework compound includes the following structures:

[0068] .

[0069] The following provides a method for preparing the above-mentioned covalent organic framework material. This method is merely illustrative and does not limit the covalent organic framework material of this application to be prepared only by the following method. Using covalent organic framework material structural unit B as... The preparation method is described below, including:

[0070] 2,3,6,7,10,11 hexahydroxysulfonates or selenides ( ) and 1,4-phenylenediboric acid are dissolved in an organic solvent to obtain a mixed solution;

[0071] The mixed solution is heated and reacted under inert gas protection;

[0072] The crude product obtained after the reaction was washed and dried to obtain a covalent organic framework material.

[0073] In some embodiments, the molar ratio of sulfur- or selenide-containing jasmine to 1,4-phenylenediboronic acid is 1:1-2, such as 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 2, to adjust the product yield.

[0074] In some embodiments, the organic solvent is tetrahydrofuran, and the concentration of sulfur or selenide sulfonyl ...

[0075] In some embodiments, the inert gas is argon or nitrogen.

[0076] In some embodiments, the temperature of the heating reaction is 100°C-140°C (e.g., 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C or 140°C), and the reaction time is 2-5 days (e.g., 24h, 36h, 48h, 60h, 72h, 84h, 96h, 108h or 120h).

[0077] In some embodiments, the step of washing and drying the crude product obtained after the reaction includes: washing the crude product obtained after the reaction sequentially with dichloromethane, ethanol and water, and freeze-drying for 24-36 hours.

[0078] The second embodiment of this application provides a negative electrode active material, which includes any one of the organic framework compounds provided in the first embodiment. This covalent organic framework material possesses both strong lithium-ion conductivity and adsorption capacity, thus exhibiting high lithium intercalation stability.

[0079] A third embodiment of this application provides a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes any one of the organic framework compounds provided in the first embodiment. This covalent organic framework material has both strong lithium-ion conduction and adsorption capabilities, thereby effectively improving the rate performance and long-cycle stability of the negative electrode sheet.

[0080] In some embodiments, the weight content of covalent organic framework material in the negative electrode film is 60%-80%. A weight content of covalent organic framework material within this range is beneficial for providing as much lithium intercalation capacity as possible. Furthermore, since the conductivity of covalent organic framework material is relatively poor, controlling its content below 80% is a reserve proportion for the addition of conductive agents, thereby improving the conductivity of the negative electrode film.

[0081] In some embodiments, the negative electrode film layer further includes a conductive agent and a binder, with the weight ratio of covalent organic framework material, conductive agent, and binder being (6-8):(3-1):1. The conductive agent further improves the conductivity of the negative electrode film layer, thereby further improving the ion and electron transport capabilities of the negative electrode sheet, which is beneficial for improving the kinetic performance of the secondary battery.

[0082] The conductive agent and binder used in the negative electrode film layer of this application can be selected from the conductive agents and binders in conventional negative electrode sheets. In some embodiments, the conductive agent includes one or more of carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] In some embodiments, the binder includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0084] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0085] The fourth embodiment of this application provides a secondary battery including a negative electrode sheet, which includes any of the negative electrode sheets provided in the third embodiment described above.

[0086] Because the covalent organic framework material provided in this application has high solvent stability, strong lithium-ion conduction and adsorption capacity, and a large number of redox active sites, it effectively improves the rate performance and long-cycle stability of secondary batteries containing it.

[0087] In some embodiments, the secondary battery also includes a positive electrode, an electrolyte, and a separator. This application does not impose any particular restrictions on the selection of the positive electrode, electrolyte, and separator.

[0088] For example, if the secondary battery is a lithium-ion battery, the positive electrode active material can be any positive electrode active material known in the art for lithium-ion batteries. The positive electrode active material may include at least one of the following materials: lithium phosphates, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials; other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4, also referred to as LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Of course, the secondary battery may also be a sodium-ion battery, and the positive electrode active material can be any positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds, Prussian blue compounds, etc., and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0089] For example, the electrolyte can be a gel electrolyte, liquid electrolyte, or solid electrolyte. The electrolyte salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. The organic solvent in the electrolyte includes ethylene carbonate, dimethyl carbonate, and diethyl carbonate. Another example is the membrane, which can be a cellulose membrane, a glass fiber membrane, or a PP membrane.

[0090] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0091] Example 1

[0092] Preparation of covalent organic framework materials:

[0093] Weigh 20 mg of 2,3,6,7,10,11 hexahydroxythiazide sulfanol (S-sum-OH) S-sum-OH (Mw = 414 g / mol) was dissolved in 2.5 mL of tetrahydrofuran solution, and then 11.3 mg of 1,4-phenylenediboric acid (Mw = 166 g / mol) was added to the mixed solution. The molar ratio of S-sum-OH to 1,4-phenylenediboric acid was approximately 1:1.4. The mixture was sonicated for 10 minutes at room temperature to obtain a uniformly dispersed mixed solution. This mixed solution was transferred to a 10 mL conventional COF synthesis tube, and the reaction tube was placed in liquid nitrogen for 10 minutes to allow the solvent to solidify. In the solidified state, the gas inside the system was removed using a vacuum pump, and the glass tube was softened using an alcohol burner and other instruments before sealing the reaction tube. The reaction tube was placed in an oven at 120 °C for 3 days. After washing multiple times with dichloromethane, methanol, ethanol, and acetone, and freeze-drying, a covalent organic framework material containing thiamethoxamene (hereinafter referred to as S-sum-COF) was obtained.

[0094] Figure 1 The infrared diffraction pattern of this covalent organic framework material is shown; Figure 2 This covalent organic framework material is shown. 13 C solid NMR spectrum; Figure 3 This covalent organic framework material is shown. 11 B solid-state NMR spectrum; Figure 4 The XPS B 1s spectrum of this covalent organic framework material is shown. Figure 5 The XPS S 2p spectrum of this covalent organic framework material is shown. Figure 6 The X-ray diffraction pattern of this covalent organic framework material is shown; Figure 7 The SEM images of this covalent organic framework material are shown. Figure 8 The TEM test results of this covalent organic framework material are shown. Figure 9 The N2 adsorption-desorption isotherm (77 K) of this covalent organic framework material is shown. Figure 10 The pore size distribution curve of this covalent organic framework material is shown.

[0095] Example 2

[0096] Preparation of covalent organic framework materials:

[0097] Weigh 20 mg of 2,3,6,7,10,11 hexahydroxyselenosyl sulforaphane (Se-sum-OH) A solution of 1,4-phenylenediboric acid (Mw = 555 g / mol) was dissolved in 2.5 mL of tetrahydrofuran solution. Then, 8.9 mg of 1,4-phenylenediboric acid (Mw = 166 g / mol) was added to the mixture, and the solution was sonicated for 10 minutes at room temperature to obtain a uniformly dispersed mixture. This mixture was transferred to a 10 mL conventional COF synthesis tube, and the tube was placed in liquid nitrogen for 10 minutes to allow the solvent to solidify. In the solidified state, the gas inside the system was removed using a vacuum pump, and the glass tube was softened using an alcohol burner before sealing the tube. The tube was then placed in an oven at 120°C for 3 days. After washing multiple times with dichloromethane, methanol, ethanol, and acetone, the mixture was freeze-dried to obtain the covalent organic framework material (hereinafter referred to as Se-sum-COF).

[0098] Figure 11 The infrared diffraction pattern of this covalent organic framework material is shown; Figure 12 This covalent organic framework material is shown. 13 C solid NMR spectrum; Figure 13 This covalent organic framework material is shown. 11 B solid-state NMR spectrum; Figure 14 The XPS B 1s spectrum of this covalent organic framework material is shown. Figure 15 The XPS Se3d spectrum of this covalent organic framework material is shown. Figure 16 The X-ray diffraction pattern of this covalent organic framework material is shown; Figure 17 The SEM images of this covalent organic framework material are shown. Figure 18 The TEM test results of this covalent organic framework material are shown. Figure 19 The nitrogen physical adsorption curve of this covalent organic framework material is shown; Figure 20 The pore size distribution curve of this covalent organic framework material is shown.

[0099] Comparative Example 1

[0100] The process is the same as in Example 1, except that 2,3,6,7,10,11-hexahydroxytriphenylene oxide is used to replace S-sum-OH, and the resulting covalent organic framework material is COF-5.

[0101] according to Figure 1 and Figure 11 It can be seen that, compared with S-sum-OH and Se-sum-OH monomers, S-sum-COF and Se-sum-COF have a lower concentration at approximately 3340 cm⁻¹. -1 The significantly weakened stretching vibrations of the nearby OH groups indicate that a condensation reaction has occurred between S / Se-sum-OH and 1,4-phenylboronic acid. Simultaneously, BO (1306 cm⁻¹, 1337 cm⁻¹) -1 ), CO (1170cm)-1 ) and BC (1018cm) -1 The appearance of the characteristic absorption peak further confirms the formation of C2BO2 connectivity.

[0102] from Figure 3 and Figure 13 It can be seen that the chemical environment of boron atoms in COF materials has changed significantly compared with the spectra of monomers.

[0103] according to Figure 2 and Figure 12 of 13 Solid-state NMR spectroscopy confirmed that the basic structural units of the COF material contain five different types of carbon, indicating that the synthesized material has a reasonable and expected chemical structure.

[0104] according to Figure 4 , 5 X-ray photoelectron spectroscopy (XPS) results for 14 and 15 show that the total XPS spectra of the two COFs mainly exhibit four peaks, corresponding to C1s, O1s, B1s, and S2p (for S-sum-COF, ...). Figure 4 ) or Se 3d (for Se-sum-COF, Figure 14 ), representing the four main elements in the structure. In high-resolution XPS spectra, the B 1s spectrum ( Figure 4 and 14 A distinct peak at 191.6 eV is characteristic of the BO bond in borate esters, directly confirming the formation of covalent bonds between monomers. Furthermore, the S 2p and Se 3d spectra show characteristic doublets at S 2p3 / 2 (163.9 eV) and S 2p1 / 2 (164.9 eV), and Se 3d5 / 2 (54.2 eV) and Se 3d3 / 2 (55.0 eV), respectively. Figure 5 and 15 These features provide clear evidence for incorporating chalcogenide-doped jasmine units into the COF structure.

[0105] Figure 6 In the study, several distinct peaks were observed at 3.70°, 6.36°, 9.6°, and 25.48° for S-sum-COF. These peaks correspond to the (100), (110), (210), and (001) crystal planes, respectively. Molecular simulation (MS) confirmed that the material conforms to the P3 space group with lattice parameters a = 28.028 Å, b = 28.028 Å, c = 4.382 Å; α = β = 90°, γ = 120°.

[0106] Figure 16In the Se-sum-COF, the (100) peak shows a leftward shift compared to the S-sum-COF. This can be attributed to the relatively smaller curvature of the Se monomer relative to the S monomer, resulting in a material with larger porosity. Therefore, the (100) peak of Se-sum-COF is approximately at 3.58°. The peak positions of Se-sum-COF are 3.58°, 6.22°, 9.12°, 14.04°, and 25.48°. These peaks correspond to the (100), (110), (120), (400), and (001) crystal planes, respectively.

[0107] Figure 7 and 17 Scanning electron microscopy (SEM) analysis showed that both S-sum-COF and Se-sum-COF exhibited disordered coral-like structures under SEM.

[0108] Figure 8 and 18 Transmission electron microscopy (TEM) analysis showed that the interplanar spacing of the (100) crystal plane of the material was 2.48 nm (S-sum-COF) and 2.38 nm (Se-sum-COF).

[0109] Figure 9 and 19 The results show that S-sum-COF and Se-sum-COF are both 1021.58m. 2 / g and 579.52m 2 / g BET specific surface area.

[0110] Figure 10 and 20 The pore size distributions of S-sum-COF are concentrated at 2.0 nm, and those of Se-sum-COF are concentrated at 2.2 nm.

[0111] Conductivity test: S-sum-COF of Example 2, Se-sum-COF of Example 1, and COF-5 of Comparative Example 1 were prepared respectively. Silver paste was uniformly coated on the upper and lower surfaces of the tablet samples and connected with gold wires with a diameter of 50 micrometers as electrodes. The conductivity was tested by the upper and lower electrode AC method with a frequency of 20 Hz to 10 MHz.

[0112] Figure 21 The top left, top right, and bottom images show the test results of the solid conductivity of S-sum-COF, Se-sum-COF, and COF-5, respectively. Specifically, the conductivity of Se-sum-COF and S-sum-COF is 2.88 × 10⁻⁶. -7 S·cm -1 and 1.49×10 -7 S·cm-1 It is approximately COF-5 (9.8 × 10⁻⁵). -10 S·cm -1 300 times that of ).

[0113] Preparation of negative electrode sheet:

[0114] Covalent organic framework material, conductive carbon Super P, and binder polyvinylidene fluoride were weighed in a mass ratio of 6:3:1, and mixed with organic solvent N-methylpyrrolidone to form a viscous slurry. The slurry was ball-milled at 300 rpm for 4 hours, coated onto copper foil, and dried in a vacuum drying oven at 120°C for 12 hours to remove the organic solvent. The slurry was then cut to 1 cm using a cutting machine. 2 Size, i.e., the size of the negative electrode sheet prepared.

[0115] Negative electrode performance test:

[0116] The negative electrode sheet prepared by this invention is used as the positive electrode of the CR 2032 button battery, lithium metal is used as the negative electrode, the separator is a polypropylene (PP) separator, and the electrolyte is formed by dissolving 1 mol / L lithium hexafluorophosphate in a solution with ethylene carbonate: dimethyl carbonate: diethyl carbonate = 1:1:1 as a mixed solvent, and then assembled into a CR 2032 button battery.

[0117] Rate performance testing: The prepared button cells were charged and discharged using a Blue Battery testing system at a constant temperature of 30℃. The charge and discharge voltage range was 0-3 V (vs. Li / Li). + Rate performance tests were conducted at current densities of 0.2, 0.5, 1, 2, 5, and 10 A / g to test the battery's cycle capacity decay at different rates.

[0118] Figure 22 The test results of a coin cell containing the S-sum-COF negative electrode prepared in Example 1 are shown. Figure 23 The test results of a battery containing the Se-sum-COF negative electrode sheet prepared in Example 2 are shown. Figure 24 Test results of a battery containing the COF-5 negative electrode sheet prepared in Example 2 are shown. Figures 22 to 24The results show that at a current density of 0.2 A / g, the specific capacity of the button cell containing the S-sum-COF negative electrode prepared in Example 1 is 630 mAh / g, and the specific capacity of the button cell containing the Se-sum-COF negative electrode prepared in Example 2 is 1200 mAh / g; at a current density of 10 A / g, the specific capacity of the button cell containing the S-sum-COF negative electrode prepared in Example 1 is 25.5 mAh / g, and the specific capacity of the button cell containing the Se-sum-COF negative electrode prepared in Example 2 is 100 mAh / g.

[0119] Further Figure 23 Analysis shows that Se-sum-COF at 0.2 A·g -1 0.5A·g -1 1A·g -1 2A·g -1 and 5A·g -1 Maintaining a current density of 1200 mAh·g -1 950mAh·g -1 748mAh·g -1 546mAh·g -1 and 247mAh·g -1 Specific capacity. When the current returns to 0.2 A·g -1 At that time, Se-sum-COF still exhibited a capacity of 1200 mAh·g. -1 It exhibits excellent specific capacity, with a capacity retention rate approaching 100%. Comparative analysis. Figure 22 , Figure 23 and Figure 24 Analysis shows that the performance of S-sum-COF and COF-5 is significantly inferior to that of Se-sum-COF: S-sum-COF at 0.2 A·g -1 It maintains approximately 638 mAh·g -1 The specific capacitance, and when the current increases to 5 A·g -1 At that time, its capacity dropped sharply to 104 mAh·g -1 It was unable to recover its initial performance after current regression; COF-5 exhibited performance below 500 mAh·g at all current densities. -1 The specific capacity, and at 5 A·g - 1 with a capacity of only 21 mAh·g -1 It exhibits extremely poor rate performance.

[0120] Cyclic performance test:

[0121] The prepared button batteries were subjected to charge-discharge tests on a Blue Battery Testing System at a constant temperature of 30℃. The charge-discharge voltage range was 0-3 V (vs. Li / Li).+ The device was charged and discharged at current densities of 0.2, 2, and 10 A / g to test the capacity decay during the test cycle.

[0122] Figures 25-27 The performance graphs of negative electrode sheets containing S-sum-COF, Se-sum-COF and COF-5 are shown sequentially after 100 cycles at a current density of 0.2 A / g. Figure 25 The results showed that S-sum-COF initially exhibited a capacity of up to 1140.8 mAh·g. -1 Its significantly high specific charge capacity decreased to 632.7 mAh·g after 100 cycles. -1 The capacity retention rate was only 55.5%.

[0123] Figure 26 The initial charge specific capacity of Se-sum-COF is shown to be 1053 mAh·g. -1 As the number of cycles increases, its specific capacity shows a gradual upward trend, reaching 1200 mAh·g after 100 cycles. -1 .

[0124] Figure 27 The results show that COF-5 exhibits an initial charge specific capacity of 726.4 mAh·g⁻¹ and an initial coulombic efficiency of 40.1%; after 100 cycles, its charge specific capacity decreases and remains at 355 mAh·g⁻¹. -1 .

[0125] Figures 28-29 The performance graphs of S-sum-COF and Se-sum-COF are shown after 500 cycles at a current density of 2 A / g.

[0126] Figure 28 The results show that the performance of S-sum-COF declines rapidly, with its charge specific capacity dropping to only 336 mAh·g after 500 cycles. -1 . Figure 29 The results show that Se-sum-COF remains stable for 500 cycles at a current density of 2 A / g, providing 701 mAh·g. -1 The charging capacity retention rate exceeds 100%.

[0127] Figures 30-32 The performance graphs of S-sum-COF, Se-sum-COF, and COF-5 are shown after 1000 cycles at a current density of 10 A / g.

[0128] Figure 30 and 32The results showed that both S-sum-COF and COF-5 exhibited poor performance, retaining only 178 mAh·g after 1000 cycles. -1 and 160mAh·g -1 . Figure 31 The results show that Se-sum-COF exhibits a capacity of 358.1 mAh·g. -1 The initial charge specific capacity, which gradually increases and remains at 500 mAh·g after 1000 cycles. -1 The coulomb efficiency is close to 100%.

[0129] In addition, other Se-sum-COF, S-sum-COF and COF were prepared using Examples 3 to 5 and Comparative Example 2, respectively, as detailed below.

[0130] Example 3

[0131] The process is the same as in Example 1, except that the mass of S-sum-OH and 1,4-phenylenediboronic acid is adjusted so that their molar ratio is 1:1.

[0132] Example 4

[0133] The process is the same as in Example 2, except that the mass of Se-sum-OH and 1,4-phenylenediboronic acid is adjusted so that their molar ratio is 1:1.

[0134] Example 5

[0135] The process is the same as in Example 2, except that the mass of Se-sum-OH and 1,4-phenylenediboronic acid is adjusted so that the molar ratio of the two is 1:2.

[0136] Comparative Example 2

[0137] The process is the same as in Comparative Example 1, except that the mass of 2,3,6,7,10,11-hexahydroxytriphenylene and 1,4-phenylenediboronic acid is adjusted so that their molar ratio is 1:1.

[0138] The specific capacity of button cells containing COF materials prepared in Examples 1 to 5 and Comparative Examples 1 to 2, prepared according to the above method at current densities of 0.2 A / g and 10 A / g, is recorded in Table 1. At the same time, the capacity retention rate 1 after 100 cycles at 0.2 A / g and the capacity retention rate 2 after 1000 cycles at 10 A / g are also recorded in Table 1.

[0139] Table 1

[0140]

[0141] The results above show that heteroatom doping (Examples 1-5) significantly improves the rate performance and overall capacity retention compared to the undoped system (Comparative Examples 1 and 2), especially Se doping (Examples 2, 4, and 5) which shows a more significant improvement compared to S doping (Examples 1 and 3).

[0142] The exemplary embodiments of the present invention have been described above. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A covalent organic framework material, said covalent organic framework material comprising bonded structural unit A and structural unit B, Structural Unit A in, X in structural unit A 1 X 2 X 3 Each is independently selected from S or Se, and structural unit B is selected from... and / or .

2. The covalent organic framework material according to claim 1, wherein, The crystal structure of the covalent organic framework material belongs to the P3 space group.

3. The covalent organic framework material according to claim 1 or 2, wherein, The interlayer spacing of the covalent organic framework in the covalent organic framework material is greater than 3.5 nm.

4. The covalent organic framework material according to any one of claims 1 to 3, wherein, The pore size of the covalent organic framework material is concentrated below 4 nm.

5. The covalent organic framework material according to any one of claims 1 to 4, wherein, X in structural unit A 1 X 2 X 3 All are S or all are Se.

6. The covalent organic framework material according to any one of claims 1 to 5, wherein, The covalent organic framework material includes the following structure: 。 7. A negative electrode active material, said negative electrode active material comprising any one of claims 1 to 6, a covalent organic framework material.

8. A negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer comprising a negative electrode active material, the negative electrode active material comprising the covalent organic framework material according to any one of claims 1 to 6.

9. The negative electrode sheet according to claim 8, wherein, The weight content of the covalent organic framework material in the negative electrode film layer is 60%-80%.

10. The negative electrode sheet according to claim 8 or 9, wherein, The negative electrode film layer also includes a conductive agent and a binder, and the weight ratio of the covalent organic framework material, the conductive agent and the binder is (6-8):(3-1):

1.

11. A secondary battery, comprising a negative electrode, wherein, The negative electrode sheet comprises the negative electrode sheet according to any one of claims 8 to 10.

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