Composite diaphragm based on covalent organic framework as well as preparation method and application of composite diaphragm

Abstract

The invention discloses a composite diaphragm based on a covalent organic framework as well as a preparation method and application of the composite diaphragm, and belongs to the technical field of zinc ion batteries. According to the covalent organic framework-based composite diaphragm, slurry is coated and bonded on the diaphragm, and the slurry comprises the following raw materials: COFs powder, conductive carbon black and PVDF powder in a weight ratio of 2: 1: 0.5; the slurry further comprises a dissolving binder, and the mass volume ratio of the COFs powder to the dissolving binder is 30: 1. The invention also discloses a preparation method of the composite diaphragm based on the covalent organic framework and application of the composite diaphragm in an aqueous zinc ion battery. The COFs (at) GF diaphragm battery disclosed by the invention can effectively inhibit dendritic crystal growth under the conditions of low current density and high current density, and meanwhile, the COFs (at) GF diaphragm battery is better in charge transfer efficiency and zinc ion migration efficiency. Therefore, the COFs (at) GF diaphragm is a more effective battery diaphragm material, and the performance and the service life of the water-based zinc ion battery can be remarkably improved and prolonged.

Description

Technical Field

[0001] The present invention relates to a composite separator based on covalent organic frameworks and its preparation method and application, belonging to the technical field of zinc-ion batteries. Background Art

[0002] Energy is one of the fundamental substances that support human survival and economic development. Facing the environmental problems and energy crises caused by the exploitation of fossil fuels, developing new sustainable energy storage solutions with low cost and high performance has become an urgent global task. In this context, aqueous zinc-ion batteries are particularly important due to their high energy and power densities. Compared with other types of batteries, aqueous zinc-ion batteries exhibit significant advantages:

[0003] Firstly, aqueous zinc-ion batteries use water-based electrolytes, whose cost is much lower than that of traditional solvents such as esters, ethers, and ionic liquids. This not only reduces the production cost but also simplifies the manufacturing process. In addition, aqueous batteries are safer because they are not prone to combustion or explosion and have less impact on the environment.

[0004] Secondly, aqueous zinc-ion batteries use zinc as the anode material, and zinc ions have excellent diffusion kinetics in the compound lattice, making zinc-based batteries more economical.

[0005] However, the commercial application of aqueous zinc-ion batteries still faces challenges, mainly including the formation of zinc dendrites, irreversible side reactions, and the corrosion problem of zinc metal on the anode side. These problems are closely related to the ion transport efficiency, which will lead to a decrease in the Coulomb efficiency and cycle life of the battery. To overcome these limitations, researchers have explored various strategies to improve battery performance. In fact, the separator plays a crucial role in the battery. It not only isolates the positive and negative electrodes to prevent short circuits but also promotes ion transport. However, the performance of separators with different structures directly affects the utilization rate of active materials, battery internal resistance, safety, and overall performance. Therefore, the development and application of high-performance functional separators have important potential for solving the problems faced by aqueous zinc-ion batteries and improving their electrochemical performance. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a composite separator based on covalent organic frameworks, using a covalent organic framework (COFs) material and coating it on the surface of a blank separator to prepare the composite separator.

[0007] Meanwhile, the present invention provides a preparation method of a composite separator based on covalent organic frameworks.

[0008] Meanwhile, the present invention provides an application of a composite separator based on covalent organic frameworks in aqueous zinc-ion batteries.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0010] A composite separator based on covalent organic framework, with a slurry coated and adhered on the separator. The slurry comprises raw materials in the following weight ratio: COFs powder, conductive carbon black, and PVDF powder = 2:1:0.5; the slurry further comprises a dissolved binder, and the mass-volume ratio of the COFs powder to the dissolved binder is 30:1, with the unit being mg:mL.

[0011] Preferably, the separator comprises a glass fiber separator.

[0012] Preferably, the coating thickness of the slurry is 6 μm.

[0013] Preferably, the dissolved binder comprises NMP.

[0014] A preparation method of a composite separator based on covalent organic framework, comprising the following steps:

[0015] Step 1, a preparation method of covalent organic framework COFs. Add 21 mg, 0.1 mmol of TP, 40.8 mg, 0.15 mmol of DBA, 1.5 mL of dioxane, 0.5 mL of mesitylene, and 6.0 mol / L, 0.5 mL of acetic acid into a 15 mL Schlenk tube in sequence; subsequently, perform ultrasonic treatment on the mixture for 10 minutes, and then perform degassing treatment on the Schlenk tube; after completing the degassing step, seal the Schlenk tube and heat and react it at 120 °C for 72 hours; after the reaction ends, collect the generated COFs powder by filtration and wash it.

[0016] In this step, TP: 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (C9H6O6); DBA: 2,5-diaminoterephthalic acid (DBA): C8H8N2O4;

[0017] The power of the ultrasonic treatment is preferably 200 w, and ultrasonic treatment is performed at room temperature.

[0018] Step 2, according to the ratio of 30 mg of COFs powder, 15 mg of conductive carbon black, and 7.5 mg of PVDF powder, after grinding for 30 min, transfer the mixture to a small crucible, add 1 mL of NMP dissolved binder, perform magnetic stirring for 6 h to form a slurry; and use a spatula to evenly coat the slurry on the glass fiber separator with a coating thickness of 6 μm, then perform ordinary drying on the glass fiber separator at 80 °C for 5 h and vacuum drying at 120 °C for 10 h; after drying, perform separator cutting to obtain the composite separator.

[0019] In this step, the particle size of the COFs powder is preferably between 100 nm and 10 μm; the particle size of the carbon black is preferably between 10 nm and 100 nm; the particle size of the PVDF powder is preferably between 1 μm and 10 μm.

[0020] The volume of the small crucible is 10 mL.

[0021] The rotation speed of magnetic stirring is preferably 1000 rpm.

[0022] Preferably, in step one, the degassing treatment method is: placing the Schlenk tube in a liquid nitrogen bath for freezing treatment, and through the cycle operation of freezing - vacuum pumping - thawing, repeating three times to thoroughly remove the oxygen in the system.

[0023] Preferably, in step one, the washing method is: washing multiple times successively with N,N - dimethylformamide (DMF), N,N - dimethylacetamide (DMA) and acetone to remove the residual reactants and impurities; finally, washing the COFs powder with a large amount of tetrahydrofuran (THF) to ensure its purity; after the above steps, the yield of the finally obtained COFs powder is 87%.

[0024] Preferably, in step two, the grinding is carried out using an agate mortar; the doctor blade is a 10 - μm doctor blade; the diaphragm cutting is a diaphragm cutting with a diameter of 19 mm.

[0025] An application of a composite diaphragm based on covalent organic framework in an aqueous zinc - ion battery, and the application method is: assembling the composite diaphragm in the aqueous zinc - ion battery.

[0026] An aqueous zinc - ion battery is prepared by using a composite diaphragm based on covalent organic framework of the present invention.

[0027] A preparation method of a composite diaphragm based on covalent organic framework, comprising the following steps:

[0028] First, determine the parameters of the covalent organic framework material and accurately prepare it effectively. The solvothermal method is the most commonly used synthesis method, which needs to be carried out in a specific environment. Place the material in a tube for degassing and sealing, and then go through three steps, repeating three times to reach the specific environment. After reacting at a certain temperature for several days, a solid insoluble substance is obtained. After washing and drying, COFs powder is obtained. The microwave method is similar to the solvothermal method. After dissolving the monomers in a solvent, seal it under certain conditions, heat it with microwave radiation for dozens of minutes to make the system temperature stable at a certain temperature, and obtain the COFs material after purification;

[0029] Next, the COFs material, carbon black, PVDF and other materials are mixed in a certain proportion and ground in an agate mortar for dozens of minutes. Then, the mixture is transferred to a small crucible, and a buffer solvent is added dropwise to dissolve the mixture, followed by stirring to form a slurry. The slurry is evenly coated on a glass fiber separator using a scraper, and then the glass fiber separator is dried normally. After drying, the separator is cut into pieces.

[0030] Finally, it is assembled into a button-type zinc-ion battery, and the electrochemical performance of the assembled battery is tested to accurately and clearly evaluate the excellent performance of the battery, so as to analyze and explain the mechanism of the COFs-based composite separator in aqueous zinc-ion batteries.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The COFs@GF separator battery of the present invention shows significant advantages in both inhibiting dendrite growth and improving the zinc-ion migration efficiency. Compared with the traditional GF separator battery, the COFs@GF separator battery can effectively inhibit dendrite growth under both low current density and high current density conditions, and also shows better performance in terms of charge transfer efficiency and zinc-ion migration efficiency. This indicates that the COFs@GF separator is a more effective battery separator material, which can significantly improve the performance and lifespan of aqueous zinc-ion batteries. Description of the Drawings

[0033] Figure 1 FIG. is a comparison diagram of dendrites of GF batteries and COFs@GF batteries. Among them, a is the dendrite diagram of GF separator battery and COFs@GF separator battery at 1 mA; b is the dendrite diagram of GF separator battery and COFs@GF separator battery at 3 mA.

[0034] Figure 2 FIG. is a zinc-ion symmetric transference number diagram of GF batteries and COFs@GF batteries. Among them, a is the impedance diagram of the two batteries before polarization; b is the impedance diagram of the two batteries after polarization; c is the polarization curve of the two batteries; d is the bar chart of the transference number of the two batteries. Detailed Embodiments

[0035] The present invention will be further described in detail below with reference to the drawings and specific embodiments. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0036] Embodiment 1

[0037] A preparation method of a composite separator based on covalent organic frameworks, comprising the following steps:

[0038] 1) First, a preparation method for covalent organic frameworks (COFs) was determined, using the classical solvothermal method. The specific steps are as follows: TP (21 mg, 0.1 mmol), DBA (40.8 mg, 0.15 mmol), dioxane (1.5 mL), mesitylene (0.5 mL), and 6.0 mol / L acetic acid (0.5 mL) were successively added to a 15 mL Schlenk tube. Subsequently, the mixture was ultrasonically treated for 10 minutes to ensure thorough mixing of the components. Then, the Schlenk tube was placed in a liquid nitrogen bath for freezing treatment, and the freeze-pump-thaw cycle operation was repeated three times to completely remove oxygen from the system. After completing the degassing step, the tube was sealed and heated at 120 °C for 72 hours. After the reaction, the generated COFs powder was collected by filtration and washed multiple times with dimethylformamide (DMF), dimethylacetamide (DMA), and acetone to remove residual reactants and impurities. Finally, the COFs powder was washed with a large amount of tetrahydrofuran (THF) to ensure its purity. After the above steps, the yield of the finally obtained COFs powder was 87%;

[0039] 2) Next, the COFs material was combined with materials such as carbon black and PVDF in the ratio of COFs powder (30 mg), conductive carbon black (15 mg), and PVDF powder (7.5 mg). After grinding them in an agate mortar for 30 min, the mixture was transferred to a small crucible, 1 ml of NMP was added to dissolve the binder, and magnetic stirring was carried out for 6 h to form a slurry; and a 10 μm doctor blade was used to evenly coat the slurry on a glass fiber separator with a coating thickness of 6 μm. Then, the glass fiber separator was dried conventionally at 80 °C for 5 h and dried under vacuum at 120 °C for 10 h; after drying, the separator was cut into pieces with a diameter of 19 mm;

[0040] In this step, both the crucible and the magnetic stir bar are very small, enabling the stirring of the above slurry. When the slurry is poured out, it can be pulled very long with a doctor blade;

[0041] 3) Finally, it was assembled into a button-type aqueous zinc-ion battery, and the electrochemical performance of the assembled battery was tested to accurately and clearly evaluate the excellent performance of all aspects of the battery, such as:

[0042] a) The current impulse of the zinc-ion battery under the conditions of a step potential of 0.01 V, a time of 0.5 s per point, and a duration of 1000 s;

[0043] b) The dendrite growth conditions of the GF battery and the COFs@GF battery were respectively tested under current densities of 1 mA and 3 mA.

[0044] The Chinese name of GF is glass fiber, and GF is short for Glass Fiber.

[0045] A composite separator based on covalent organic framework, with a slurry coated and bonded on the separator. The slurry includes raw materials in the following weight ratio: COFs powder, conductive carbon black, and PVDF powder = 2:1:0.5. The slurry also includes a dissolved binder, and the mass-volume ratio of COFs powder to the dissolved binder is 30:1, with the unit being mg:mL. Preferably, the separator is a glass fiber separator. Preferably, the coating thickness of the slurry is 6 μm. Preferably, the dissolved binder is NMP.

[0046] Application of a composite separator based on covalent organic framework in an aqueous zinc-ion battery. The application method is: assembling the composite separator in the aqueous zinc-ion battery.

[0047] An aqueous zinc-ion battery is prepared by using a composite separator based on covalent organic framework of this embodiment.

[0048] From Figure 1 As can be seen from the dendrite diagram at a - 1 mA, for GF: the dendrite growth is relatively obvious, the battery is penetrated by dendrites, and the damage time is early, indicating that under such conditions, the dendrite growth in the GF separator battery is relatively active. For COFs@GF: the dendrite growth is relatively less, and the time for the battery to be damaged by dendrite penetration is relatively late, indicating that the COFs@GF separator battery performs better in inhibiting dendrite growth.

[0049] From Figure 1 As can be seen from the dendrite diagram at b - 3 mA, for GF: the dendrite growth is further aggravated, indicating that at a higher current density, the dendrite growth problem in the GF separator battery is more serious. For COFs@GF: the dendrite growth is still less, and compared with the condition of 1 mA, the increase amplitude of dendrite growth is smaller, indicating that the COFs@GF separator can still effectively inhibit dendrite growth at a high current density.

[0050] It can be seen from this that: the COFs@GF separator battery shows better dendrite inhibition ability under both low current density (1 mA) and high current density (3 mA) conditions. Compared with the traditional GF separator battery, the dendrite growth is significantly reduced. This indicates that the COFs@GF separator has significant advantages in inhibiting dendrite growth, especially at a high current density.

[0051] Figure 2 a - Impedance diagrams of the two batteries before polarization: Through the impedance diagrams, it can be observed that under the condition of charge transfer impedance of the two batteries before polarization, the impedance of the COFs@GF separator battery is lower, indicating that its charge transfer efficiency is higher.

[0052] Figure 2Impedance diagrams of the two types of batteries after b-polarization: After polarization, the impedance changes of the two types of batteries can reflect their charge transfer characteristics during the charge and discharge processes. The impedance change of the COFs@GF separator battery is smaller, indicating that it has a higher charge transfer efficiency and better stability during polarization.

[0053] Figure 2 c-Polarization curves of the two types of batteries: The polarization curve reflects the voltage change of the battery at different current densities. The polarization voltage of the COFs@GF separator battery is lower, indicating that it has better voltage stability during the charge and discharge processes.

[0054] Figure 2 d-Bar charts of the transference numbers of the two types of batteries: The transference number reflects the migration efficiency of zinc ions in the battery. The COFs@GF separator battery has a higher transference number, indicating that it has a higher zinc ion migration efficiency, which helps to improve the performance and lifespan of the battery.

[0055] It can be seen that the impedance change of the COFs@GF separator battery before and after polarization is smaller, indicating that it has a higher charge transfer efficiency and better voltage stability during the charge and discharge processes. Moreover, the COFs@GF separator battery has a higher zinc ion transference number, indicating that it has a higher zinc ion migration efficiency, which helps to improve the overall performance and cycle stability of the battery.

[0056] In summary, from Figure 1 and Figure 2 analysis, it can be seen that the COFs@GF separator battery shows significant advantages in both inhibiting dendrite growth and improving the zinc ion migration efficiency. Compared with the traditional GF separator battery, the COFs@GF separator battery can effectively inhibit dendrite growth under both low current density and high current density conditions, and at the same time shows better performance in terms of charge transfer efficiency and zinc ion migration efficiency. This indicates that the COFs@GF separator is a more effective battery separator material, which can significantly improve the performance and lifespan of the battery.

[0057] It should be understood that, in order to streamline the present disclosure and assist in understanding one or more of the various inventive aspects, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected by the claims, the inventive aspects lie in less than all of the features of the preceding disclosed embodiments. Thus, the claims following the detailed description are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate embodiment of the present invention.

[0058] Although the present invention has been described based on a limited number of embodiments, those skilled in the art in this technical field will understand that other embodiments can be envisaged within the scope of the present invention thus described. In addition, it should be noted that the language used in this specification is mainly selected for the purpose of readability and teaching, rather than for the purpose of explaining or limiting the subject matter of the present invention. Therefore, many modifications and changes will be obvious to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure of the present invention is illustrative rather than restrictive, and the scope of the present invention is defined by the appended claims.

[0059] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, several improvements and refinements can be made without departing from the principle of the present invention, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A composite separator based on covalent organic framework, characterized in that, The separator is coated with a slurry, and the slurry includes raw materials in the following weight ratio: COFs powder, conductive carbon black, and PVDF powder = 2:1:0.5; the slurry also includes a dissolved binder, and the mass-volume ratio of COFs powder to the dissolved binder is 30:1, with the unit being mg:mL.

2. The composite separator based on covalent organic framework according to claim 1, wherein, The separator includes a glass fiber separator.

3. The composite separator based on covalent organic framework according to claim 1, wherein The coating thickness of the slurry is 6 μm.

4. The composite separator based on covalent organic framework according to claim 1, characterized in that The dissolved binder includes NMP.

5. A preparation method of a composite separator based on covalent organic framework according to any one of claims 1 to 4, characterized in that, It includes the following steps: Step 1, Preparation method of covalent organic framework COFs: 21 mg, 0.1 mmol of TP, 40.8 mg, 0.15 mmol of DBA, 1.5 mL of dioxane, 0.5 mL of mesitylene, and 6.0 mol / L, 0.5 mL of acetic acid are successively added to a 15 mL Schlenk tube; subsequently, the mixture is ultrasonically treated for 10 minutes, and then the Schlenk tube is degassed; after the degassing step is completed, the Schlenk tube is sealed and heated at 120 °C for 72 hours; after the reaction ends, the generated COFs powder is collected by filtration and washed. Step 2, According to the ratio of 30 mg of COFs powder, 15 mg of conductive carbon black, and 7.5 mg of PVDF powder, after grinding for 30 min, the mixture is transferred to a small crucible, 1 mL of NMP dissolved binder is added dropwise, and magnetic stirring is carried out for 6 h to make a slurry. And use a scraper to evenly coat the slurry on the glass fiber separator with a coating thickness of 6 μm, and then the glass fiber separator is dried conventionally at 80 °C for 5 h and vacuum dried at 120 °C for 10 h; after drying, the separator is cut into pieces to obtain a composite separator.

6. The preparation method according to claim 5, characterized in that, In Step 1, the degassing treatment method is: placing the Schlenk tube in a liquid nitrogen bath for freezing treatment, and through the cycle operation of freezing - pumping - thawing, repeating three times to thoroughly remove oxygen in the system.

7. The preparation method according to claim 5, characterized in that In Step 1, the washing method is: successively washing with dimethylformamide DMF, dimethylacetamide DMA, and acetone for multiple times to remove residual reactants and impurities; finally, washing the COFs powder with a large amount of tetrahydrofuran THF to ensure its purity. After the above steps, the yield of the finally obtained COFs powder is 87%.

8. The preparation method according to claim 5, characterized in that, In Step 2, the grinding is carried out using an agate mortar; the scraper is a 10 μm scraper; the separator cutting is to cut the separator with a diameter of 19 mm.

9. Use of a composite separator based on covalent organic framework in an aqueous zinc ion battery according to any one of claims 1 to 4, characterized in that, The application method is: assembling the composite separator in an aqueous zinc-ion battery.

10. A water-based zinc-ion battery, characterized in that, It is obtained by preparing a composite separator based on covalent organic framework according to any one of claims 1 to 4.

Images