A fully conjugated three-dimensional covalent organic polymer, preparation and application as a lithium ion battery cathode material
The synthesis of a fully π-conjugated three-dimensional covalent organic polymer with carbon-carbon double bonds via the Knoevenagel reaction solves the problem of charge transport obstruction in the positive electrode of lithium-ion batteries, achieving high stability and high capacity lithium-ion battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-20
- Publication Date
- 2026-03-24
AI Technical Summary
Existing three-dimensional conjugated covalent organic polymers suffer from hindered charge transport in the z-direction, affecting the conductivity of the materials and limiting their application in lithium-ion battery cathodes.
A fully π-conjugated three-dimensional covalent organic polymer with carbon-carbon double bonds was synthesized using the Knoevenagel reaction. By increasing the degree of π-conjugation in three-dimensional space, the charge transport performance was improved, and it was applied to the cathode of lithium-ion batteries.
The cathode material for lithium-ion batteries achieves high stability and high charge/discharge capacity, with a discharge capacity of 238.3 mAh·g⁻¹ at a current density of 0.1 A·g⁻¹, a coulombic efficiency of 99.61% after 200 cycles, and a capacity retention rate of 98.96% after 1000 cycles.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of porous covalent organic polymer materials, specifically relating to the preparation of a novel three-dimensional fully π-conjugated organic polymer material with carbon-carbon double bond (C=C) linkage. This three-dimensional covalent organic polymer can be applied to the cathode field of lithium-ion batteries and effectively improves the stability and charge / discharge capacity of lithium-ion batteries. Background Technology
[0002] Covalent organic polymers (COPs) are a class of porous organic materials formed by covalently linking multiple organic structural units. Due to their high adsorption capacity, large surface area, high porosity, chemical tunability, high stability, and ease of synthesis, they have attracted widespread interest and developed rapidly, finding broad applications in drug delivery, separation technology, chemical sensors, gas storage, catalysis, optoelectronics, energy storage, and biomedical products. (New J. Chem., 2020, 44, 12331).
[0003] Covalent polymers (COPs) can covalently polymerize organic ligands containing functional groups with specific active sites into multidimensional, multifunctional porous organic materials. Most current reports focus on fully conjugated two-dimensional COPs, which improve lithium storage capacity by introducing groups such as carbonyl groups (C=O) that can serve as lithium-ion active sites. For example, in 2021, Chen's research group constructed a two-dimensional COP containing numerous C=O active sites using 2,7-dibromo-4,5,9,10-pyrenetetrone and 1,3,5-benzenetricarboxylic acid as ligands and successfully applied it to the cathode of a lithium-ion battery. The COP, when used as a lithium-ion battery cathode material, exhibited excellent long-cycle stability at a current density of 0.1 A·g-1. -1 At that time, it had a capacity of 224 mAh·g -1 It has a relatively considerable capacity, and after 1400 cycles, the capacity retention rate is close to 95% (J. Mater. Chem. A, 2021, 9, 2700).
[0004] Compared to two-dimensional materials, research on three-dimensional materials is relatively limited. For two-dimensional carbon-carbon double bonds (COPs), charge can be rapidly transported and delocalized in the π-conjugated plane. However, in the z-direction perpendicular to the xy-conjugated plane, charge transport is hindered due to the lack of effective conjugation between layers, significantly affecting the conductivity of COP materials. Fully conjugated three-dimensional COPs, by increasing the π-conjugation degree in the dimensional dimension, effectively improve the charge transport performance of the material. Therefore, developing novel three-dimensional fully conjugated COPs for applications in batteries and other fields is of significant research importance. To this end, we constructed a novel three-dimensional COP material with fully conjugated carbon-carbon double bonds (C=C) and applied it to the cathode of lithium-ion batteries, exhibiting excellent cycle stability and charge-discharge capacity.
[0005] Exploring the preparation of three-dimensional fully conjugated covalent organic polymers and their application in lithium-ion battery cathodes is of great research significance for promoting the development of efficient, green and sustainable batteries. Summary of the Invention
[0006] The purpose of this invention is:
[0007] First, a method for synthesizing a fully π-conjugated three-dimensional covalent organic polymer material with abundant lithium-ion redox active sites linked by carbon-carbon double bonds is provided.
[0008] Second, the application of fully π-conjugated three-dimensional covalent organic polymer materials containing abundant lithium-ion redox active sites in the field of lithium-ion battery cathodes.
[0009] A three-dimensional covalent organic polymer, characterized by the following structural formula:
[0010] The wavy lines represent continuation with the structural formula.
[0011]
[0012] Terminal carbon-carbon double bond connection;
[0013] in The aromatic ring represents a heterocyclic aromatic ring, such as an O / S / Se hybrid ring, where the aromatic ring is benzene, naphthalene, etc.
[0014] like It can be Isoaromatic heterocycles. R is a hydrogen atom, C is a carbon atom. 1-20 Alkyl or alkyl substituents or other substituents (aryl, substituted aryl, halogen, nitro, etc.).
[0015] The first aspect of this invention is to provide a method for synthesizing a fully π-conjugated three-dimensional covalent organic polymer material with carbon-carbon double bonds, the synthesis steps of which are as follows:
[0016] (1) Dissolve the saddle-shaped cyclooctatetraene tetrathiophene derivative ligand COThP-CHO and S-indole-1,3,5,7(2H,6H)-tetraone (ICTO) with aromatic heterocyclic substituted ligands in an organic solvent, and then add the catalyst pyridine; wherein COThP-CHO is a saddle-shaped cyclooctatetraene tetrathiophene derivative ligand, and the aromatic heterocyclic ligand can be taken from benzene ring, furan, thiophene, selenophene and other aromatic heterocyclic ligands.
[0017] (2) The reaction system is thoroughly mixed and dispersed after a brief ultrasonic treatment, then subjected to a freeze-vacuum-thaw cycle, and finally sealed and heated to complete the reaction;
[0018] (3) The product was filtered, washed, and then purified by extraction to obtain a three-dimensional covalent organic polymer with a fully conjugated carbon-carbon double bond structure (named BUCT-COP-8).
[0019] The structural formula of the saddle-ring octatetraene tetrathiophene derivative ligand COThP-CHO is as follows: where The aromatic ring represents a heterocyclic aromatic ring, such as an O / S / Se hybrid ring, where the aromatic ring is benzene, naphthalene, etc.
[0020] like It can be Other aromatic compounds.
[0021]
[0022] Furthermore, in step (1), the molar ratio of COThP-CHO and S-indole-1,3,5,7(2H,6H)-tetraone (ICTO) is 1:1 to 10, with the optimal ratio being 1:2.
[0023] Furthermore, in step (1), the solvent is a mixture of n-butanol (n-BuOH) and o-dichlorobenzene (o-DCB).
[0024] Furthermore, in step (1), the mixed solvent is a mixture of n-butanol and o-dichlorobenzene with a volume ratio of 0 to 10: 10 to 0 (the optimal volume ratio is 1:1).
[0025] Furthermore, in step (1), the amount of pyridine catalyst used is 0 to 1 mL of COThP-CHO per 0.015 mmol (the optimal volume is 0.15 mL).
[0026] Furthermore, in step (2), the ultrasonic time is 1 to 30 minutes, and the freezing-vacuum-thawing cycle method is as follows: the reactants are frozen with liquid nitrogen, vacuumed, and thawed with nitrogen gas.
[0027] Furthermore, in step (2), the temperature of the heating reaction is between 50 and 200°C, and the reaction time is between 1 and 10 days.
[0028] Furthermore, in step (3), Soxhlet extraction is performed multiple times using organic solvents such as dichloromethane, acetone, and tetrahydrofuran, with each extraction lasting 1 to 3 days until the solvent becomes colorless. Finally, the solid is collected and vacuum dried to obtain a carbon-carbon double-bonded, fully π-conjugated, three-dimensional covalent organic polymer.
[0029] This invention utilizes the Knoevenagel reaction to synthesize, for the first time, a fully conjugated three-dimensional COP material, BUCT-COP-8, with the fully conjugated organic ligand COThP-CHO and s-indole-1,3,5,7(2H,6H)-tetraone (ICTO). The synthetic route is as follows:
[0030]
[0031] It can be The substituent R on the isoaromatic ring ICTO can be a hydrogen atom, C, or other atoms. 1-20 Alkyl or other substituent groups.
[0032] The second aspect of this invention is that the material prepared by the above-described method for synthesizing a fully conjugated three-dimensional covalent organic polymer is applied to the positive electrode of a lithium-ion battery and subjected to battery testing. The method includes the following steps: dispersing the fully conjugated covalent organic polymer (BUCT-COP-8), Ketjen black, and polyvinylidene fluoride (PVDF) in a certain proportion in N-methylpyrrolidone (NMP) to form a slurry, loading it onto copper foil, and vacuum drying it at a certain temperature. Using this as the positive electrode, a lithium sheet as the counter electrode, lithium hexafluorophosphate + EC / DMC as the electrolyte, and a polyethylene membrane as the separator, the battery is assembled in an argon-atmospheric glove box. The front cover, positive electrode, and separator are placed in that order. After dripping in the lithium hexafluorophosphate + EC / DMC electrolyte, the lithium sheet, gasket, and washers are added. Then, the back cover is placed on top for pressing, and the battery is left to stand for 12-24 hours to allow the electrolyte to fully contact the electrodes, thus forming a BUCT-COP-8 battery for performance testing.
[0033] Furthermore, the slurry ratio is BUCT-COP-8: Ketjen Black: polyvinylidene fluoride mass ratio = 1~8:8~1:1~8 (the optimal ratio is 7:2:1).
[0034] Furthermore, the loading amount of the slurry on the copper foil is 0.5–2 mg / cm². 2 .
[0035] Furthermore, the vacuum drying temperature of the material is 30–60°C (the optimal temperature is 40°C).
[0036] Furthermore, the material is tested in the Blue Electric testing system for battery capacity and charge-discharge cycle stability.
[0037] The advantages of this invention are:
[0038] (1) This invention successfully synthesized a highly stable, fully conjugated three-dimensional saddle-shaped covalent organic polymer material with carbon-carbon double bond linkage in one step via the Knoevenagel reaction, and applied it to the field of lithium-ion battery cathode.
[0039] (2) The fully conjugated three-dimensional covalent organic polymer BUCT-COP-8 prepared in this invention exhibits high stability and capacity in the field of lithium-ion batteries, with a capacity of 0.1 A·g. -1 At current density, the discharge capacity of the BUCT-COP-8 battery can reach 238.3 mAh·g. -1 After 200 laps, the Coulomb efficiency was 99.61%, at 1 A·g -1 After 1000 cycles, the discharge capacity is 122.4 mAh·g. -1 After 1000 cycles, the coulombic efficiency was 99.90%, and the capacity retention was 98.96%. In rate testing, the values were 0.1, 0.2, 0.5, 1.0, 2.0, and 0.1 A·g. -1 The discharge capacities at the given current densities were 234, 204, 155, 121, 92, and 218 mAh·g, respectively. -1 When the current density returns to 0.1 A·g -1 At that time, it can be restored to 218mAh·g -1 Reversible capacity. Attached Figure Description
[0040] Figure 1 The infrared absorption spectrum (FT-IR) of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared in this invention.
[0041] Figure 2 X-ray photoelectron spectroscopy (XPS) of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared in this invention.
[0042] Figure 3 Solid-state NMR spectrum of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared in this invention.
[0043] Figure 4 The nitrogen adsorption-desorption curve and pore size distribution of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared in this invention are shown.
[0044] Figure 5Cyclic voltammetry (CV) curves of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared in this invention.
[0045] Figure 6 The impedance spectrum of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared in this invention.
[0046] Figure 7 Long-cycle charge-discharge stability curves of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared for this invention.
[0047] Figure 8 The constant current charge-discharge curves of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared in this invention were obtained after it was assembled into a battery.
[0048] Figure 9 Rate testing of the three-dimensional covalent organic polymer (BUCT-COP-8) prepared in this invention after being assembled into a battery. Detailed Implementation
[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, the scope of protection of this invention is not limited to the following examples.
[0050] Example 1
[0051] The synthetic steps for a carbon-carbon double-bonded, three-dimensional, fully conjugated covalent organic polymer rich in carbonyl groups (BUCT-COP-8) are as follows:
[0052] Weigh out 0.015 mmol of COThP-CHO and 0.03 mmol of s-indole-1,3,5,7(2H,6H)-tetraone (ICTO) and add them to a Pyrex tube. Add 0.5 mL of n-butanol (n-BuOH) and 0.5 mL of o-dichlorobenzene (o-DCB) to the tube, then sonicate to mix thoroughly. Add 0.15 mL of pyridine catalyst and sonicate for 10 min to disperse evenly. Seal the wider end of the Pyrex tube and purge the narrower end with nitrogen gas. Repeat the evacuation and thawing process several times. After tightening the tube, place it in an oven and allow it to stand. Increase the temperature from room temperature to 50°C–200°C and maintain this temperature for 12–72 hours to carry out the reactive thermal polycondensation reaction. After the reaction is complete, allow it to cool naturally in the oven. To remove unreacted ligands and small organic molecules from COP, the product was sequentially washed with various organic solvents, including tetrahydrofuran, 1,4-dioxane, and dichloromethane, by filtration. The COP was then collected in a paper package and placed in a Soxhlet extractor, where it was refluxed with tetrahydrofuran to further remove the small organic molecules. The solvents used for the extraction were changed multiple times, including dichloromethane and acetone, for a total extraction period of over three days. After the paper package was removed and dried, the COP inside was collected and placed in a drying oven for further drying to remove the solvent. A brownish-black powdery solid was obtained.
[0053] Figure 1 and Figure 2 These are the infrared spectrum and the X-ray photoelectron spectrum, respectively. The wavelength in the infrared spectrum is 1720.19 cm⁻¹. -1 The typical carbonyl band at the position proves the successful introduction of ICTO. The peak at 284.5 eV in the XPS spectrum indicates the formation of carbon-carbon double bonds, confirming the formation of carbon-carbon double bond connecting units and proving the successful synthesis of the material BUCT-COP-8.
[0054] Example 2: The three-dimensional fully conjugated covalent organic polymer BUCT-COP-8 was assembled into a lithium-ion battery, and charge-discharge tests were performed.
[0055] The fully conjugated covalent organic polymer (BUCT-COP-8), Ketjen black, and polyvinylidene fluoride prepared in this invention are dispersed in N-methylpyrrolidone (NMP) in a certain ratio (mass ratio 7:2:1) to form a slurry, which is loaded onto copper foil and vacuum dried at a certain temperature. The slurry is used as the positive electrode, lithium sheet as the counter electrode, lithium hexafluorophosphate + EC / DMC as the electrolyte, and polyethylene film as the separator. The battery is assembled in a glove box under an argon atmosphere.
[0056] The BUCT-COP-8 assembled battery at 0.5 mV·s -1 Cyclic voltammetry (CV) was performed, and two sets of redox peaks appeared in the second to fifth cycles, corresponding to the reversible lithiation / deoxygenation reaction of lithium ions and carbonyl groups, such as... Figure 5It can be seen that it has good reversibility. Rate tests were conducted at different current densities: 0.1, 0.2, 0.5, 1.0 and 2.0, 0.1 A·g. -1 The discharge capacities at the given current densities were 234, 204, 155, 121, 92, and 218 mAh·g, respectively. -1 When the current density returns to 0.1 A·g -1 At that time, it can be restored to 218mAh·g -1 The reversible capacity (indicating minimal reversible loss), such as Figure 9 In 1A·g -1 After undergoing 1000 cycles of long-term cycling stability testing, the discharge capacity was 122.4 mAh·g. -1 After 1000 cycles, the coulombic efficiency is 99.90%, and the capacity retention rate is 98.96%. Figure 7 Experiments have shown that three-dimensional fully conjugated covalent organic polymers with carbon-carbon double bonds, when assembled into the positive electrode of lithium-ion batteries, exhibit excellent stability and high capacity, making a significant contribution to the application of covalent organic polymers in lithium-ion and other battery fields.
[0057] The above embodiments are merely illustrative examples to clearly illustrate the present invention, and should not be construed as limiting the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All changes made within the scope of the independent claims of this invention are also within the scope of protection of this invention.
[0058] Appendix Figure 1 Note that the wavelength in the infrared spectrum is 1720.19 cm⁻¹. -1 The carbonyl characteristic peak at the position confirms the successful introduction of the ICTO ligand.
[0059] Appendix Figure 2 The results show the formation of C=C (284.6 eV) and the introduction of C=O (287.5 eV), as well as the introduction of C=O (531.8 eV), with a relatively high peak intensity. This demonstrates the successful formation of C=C and the introduction of C=O in BUCT-COP-8.
[0060] Appendix Figure 3 The solid-state NMR spectrum of BUCT-COP-8, based on the quantity and types of C, further confirms the successful synthesis of BUCT-COP-8.
[0061] Appendix Figure 4 This indicates that the pores in BUCT-COP-8 are mainly micropores, with a small number of mesopores or macropores.
[0062] Appendix Figure 5 This indicates that the redox reaction in the lithium-ion battery assembled by BUCT-COP-8 has high reversibility.
[0063] Appendix Figure 6 The decrease in electrochemical impedance of the BUCT-COP-8 battery indicates that the battery is continuously activated as it cycles, exposing more redox active sites, which is beneficial to the battery reaction.
[0064] Appendix Figure 7 This demonstrates that the introduction of BUCT-COP-8 into the electrode material provides more active sites for lithium ions, thereby significantly improving the capacity performance of lithium-ion batteries.
[0065] Appendix Figure 8 This indicates that the redox reaction in the battery has high reversibility.
[0066] Appendix Figure 9 The charge / discharge rate tests at different current densities show that the battery has a considerable capacity at different current densities, and the redox reaction of the battery has good reversibility.
Claims
1. A fully conjugated three-dimensional covalent organic polymer, characterized in that, The structure is as follows: , The wavy lines represent continuation within the structural formula. Terminal carbon-carbon double bond connection; in Represents an aromatic ring, an O / S / Se hybridized aromatic heterocycle; R represents a hydrogen atom, C represents a carbon atom. 1-20 Alkyl or alkyl substituent.
2. The fully conjugated three-dimensional covalent organic polymer according to claim 1, characterized in that, The aromatic ring is benzene or naphthalene.
3. A fully conjugated three-dimensional covalent organic polymer according to claim 1, characterized in that, for .
4. A method for preparing a fully conjugated three-dimensional covalent organic polymer according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Dissolve the aromatic heterocyclic substituted saddle-shaped cyclooctatetraene tetrathiophene derivative ligand COThP-CHO and S-indole-1,3,5,7(2H,6H)-tetraone (ICTO) in an organic solvent, and then add the catalyst pyridine; wherein COThP-CHO is a saddle-shaped cyclooctatetraene tetrathiophene derivative ligand. (2) The reaction system is thoroughly mixed and dispersed after a brief ultrasonic treatment, then subjected to a freeze-vacuum-thaw cycle, and finally sealed and heated to complete the reaction; (3) The product was filtered, washed, and then purified by extraction to obtain a three-dimensional covalent organic polymer with a fully conjugated carbon-carbon double bond structure (named BUCT-COP-8). 。 5. The method according to claim 4, characterized in that, In step (1), the molar ratio of COThP-CHO and S-indole-1,3,5,7(2H,6H)-tetraone (ICTO) is 1:1~10.
6. The method according to claim 4, characterized in that, In step (1), the molar ratio of COThP-CHO and S-indole-1,3,5,7(2H,6H)-tetraone (ICTO) is 1:
2.
7. The method according to claim 4, characterized in that, In step (1), the solvent is n-butanol ( n A mixed solvent of -BuOH and o-dichlorobenzene (o-DCB); a mixed solvent of n-butanol and o-dichlorobenzene in a volume ratio of 0~10:10~0.
8. The method according to claim 7, characterized in that, The volume ratio of the mixed solvent of n-butanol and o-dichlorobenzene is 1:
1.
9. The method according to claim 4, characterized in that, In step (1), the amount of pyridine catalyst used is 0 to 1 mL of COThP-CHO per 0.015 mmol.
10. The method according to claim 4, characterized in that, Each 0.015 mmol corresponds to a COThP-CHO volume of 0.15 mL.
11. The method according to claim 4, characterized in that, In step (2), the ultrasonic time is 1~30 min, and the freezing-vacuum-thawing cycle method is: freezing the reactants with liquid nitrogen, evacuating, and thawing with nitrogen gas; in step (2), the heating reaction temperature is between 50~200 ℃, and the reaction time is 1~10 days. In step (3), Soxhlet extraction is performed multiple times with dichloromethane, acetone and tetrahydrofuran, with each extraction lasting 1 to 3 days until the solvent becomes colorless. Finally, the solid is collected and vacuum dried to obtain a fully conjugated three-dimensional covalent organic polymer with carbon-carbon double bonds.
12. The application of the fully conjugated three-dimensional covalent organic polymer according to any one of claims 1-3 as a cathode material for lithium-ion batteries.
13. A lithium-ion battery, characterized in that, The positive electrode comprises a fully conjugated three-dimensional covalent organic polymer as described in any one of claims 1-3.