Method for regulating and controlling functionalization of lithium battery diaphragm COFs based on catalyst concentration

Abstract

The invention discloses a method for regulating and controlling functionalization of a lithium battery diaphragm COFs based on catalyst concentration, and belongs to the field of lithium battery diaphragms.The method for regulating and controlling functionalization of the lithium battery diaphragm COFs based on catalyst concentration comprises the steps that S1, a solution is prepared, specifically, 1, 1, 3-benzenetricarboxaldehyde is dissolved in dichloromethane, and a solution A is obtained; dissolving a catalyst in deionized water to obtain a solution B; dissolving tris (4-aminophenyl) amine in N, N-dimethylformamide to obtain a solution C; and S2, in-situ COFs functionalization: sequentially superposing the solution A, the solution B and the solution C to form a three-layer system, placing the commercial diaphragm of the lithium battery on the interface of the solution A and the solution B for reaction, and washing and drying after the reaction to obtain the COFs functionalized diaphragm, so that the problems of non-uniform distribution of functional materials, less filling of internal pore diameters, difficulty in loading of high-content functional materials and the like in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery separators, and more specifically to a method for functionalizing COFs in lithium battery separators based on catalyst concentration. Background Technology

[0002] In the existing technology, the growth mode of COFs in the membrane is difficult to control, and there are problems such as uneven distribution of functional materials, insufficient filling of internal pores, and difficulty in loading high content functional materials: (1) Uneven distribution of functional materials: Traditional methods cannot control the penetration depth of COF particles, resulting in insufficient filling of internal pores in the membrane; (2) The effect of catalyst concentration is unclear: There is a lack of theoretical basis for controlling the layered growth and mechanical strength of COFs by catalyst concentration; (3) Insufficient high loading performance: Low concentration catalysts lead to surface modification, while high concentrations cause the membrane to float or become loose.

[0003] Chinese patent CN119241789A discloses a method for preparing BrCOFs materials and covalent organic framework (COF) interface films for lithium metal batteries. The method involves dissolving 1,3,5-tris(4-aminophenyl)benzene and 2,5-dibromobenzene-1,4-dicarboxaldehyde in an organic solvent, then adding acetic acid dropwise. The reaction mixture is stirred, and after the reaction is complete, filtered, washed, and centrifuged to obtain Br-COFs. However, this method coats the prepared Br-COFs slurry onto a copper foil surface to obtain a Cu electrode covered by a Br-COFs film. The modified material cannot penetrate into the membrane, and the penetration depth of the COFs particles cannot be controlled, resulting in insufficient pore filling within the membrane. Therefore, a precise control method is needed to optimize the membrane pore filling degree and COFs functionalization. Summary of the Invention

[0004] To alleviate or partially alleviate the above-mentioned technical problems, the solution of the present invention is as follows:

[0005] A method for functionalizing COFs in lithium-ion battery separators based on catalyst concentration control includes the following steps:

[0006] S1. Solution preparation: Dissolve pyromellitic aldehyde in dichloromethane to obtain solution A; dissolve the catalyst in deionized water to obtain solution B; dissolve tris(4-aminophenyl)amine in N,N-dimethylformamide to obtain solution C;

[0007] S2. In-situ COFs functionalization: A three-layer system is formed by sequentially stacking solutions A, B, and C. A commercial lithium battery separator is placed at the interface between solution A and solution B to react. After the reaction, the separator is washed and dried to obtain a COFs functionalized separator.

[0008] This method constructs an oil-water-oil three-layer system, and then controls the nucleation mode and reaction rate of COFs on the membrane based on the catalyst concentration. This allows COFs to uniformly fill the membrane pores in a layered, penetrating growth manner, achieving uniform COFs formation in the membrane bulk phase and improving the mechanical strength of the membrane. It has the advantages of simple method, low cost and high efficiency.

[0009] Preferably, the catalyst in solution B of step S1 is formic acid, acetic acid, or propionic acid.

[0010] More preferably, the catalyst in solution B of step S1 is acetic acid.

[0011] Adding water-soluble organic acids as catalysts can accelerate the reaction.

[0012] Preferably, the concentration of acetic acid in solution B in step S1 is 1-9 mol / L. -1 .

[0013] The correspondence between acetic acid concentration and COF growth mode is: 1-5 mol L -1 At that time, COFs formed a non-uniform layer on the membrane surface, with an internal pore filling rate of 40-60%; 6 mol L -1 At that time, COFs form a dense layer on the membrane surface and uniformly fill the internal pores of the membrane through a layer-by-layer growth mode, with a filling rate of 80-90%; 7-9 mol L -1 When COFs form a loose layer, the membrane is easy to float, and the internal pore filling rate is <50%.

[0014] Preferably, the concentration of acetic acid in solution B in step S1 is 6 mol / L. -1 The concentration of pyromellitic aldehyde in solution A in step S1 is 4.2 mmol / L. -1 The concentration of tris(4-aminophenyl)amine in solution C in step S1 is 4.2 mmol / L. -1 .

[0015] Preferably, the commercial lithium battery separator in step S2 is selected from one of polypropylene separator (PP), polyethylene separator (PE), or PP / PE composite separator.

[0016] Preferably, the reaction time in step S2 is 5-10 days.

[0017] Preferably, the washing in step S2 is performed by sequentially washing with dichloromethane, ethanol, acetone and N,N-dimethylformamide.

[0018] Preferably, the reaction time in step S2 is 7 days; the drying temperature in step S2 is 60 °C and the drying time is 12 h; the volume ratio of solution A, solution B and solution C in step S2 is 8:2:5.

[0019] The technical solution of this invention has one or more of the following beneficial technical effects:

[0020] (1) By precisely controlling the concentration of acetic acid catalyst, a quantitative correlation mechanism between concentration and COF growth mode was established, which solved the problem of uncontrollable growth mode of functional materials in traditional methods.

[0021] (2) At 6 mol L -1 At certain concentrations, COFs uniformly fill the internal pores of the membrane in a layered penetration mode, increasing the filling rate by 40-50% compared to traditional surface modification methods, forming a "continuous functional network of surface and pores," which can significantly enhance the electrochemical performance of the membrane; using 6 mol L... -1 The optimal growth mode at acetic acid concentration shows a synergistic effect between the chemisorption of tertiary amine groups (-N⁻) in the COF structure and the physical confinement of narrow pores, which has the potential to improve the adsorption of polysulfides in lithium-sulfur batteries and reduce interfacial diffusion resistance. A balance between functionalization and mechanical strength is achieved through catalyst concentration control, with 6 mol L⁻¹ being the optimal growth mode. -1 The COFs functionalized separator prepared at the concentration still maintains structural integrity and high mechanical strength after bending and scratching, breaking through the bottleneck of insufficient mechanical properties of interfacial self-assembled membranes and meeting the stringent requirements of battery assembly for the mechanical properties of separators.

[0022] (3) This method uses Lewis acid acetic acid catalyst, the raw materials are readily available and the process is simple. It is compatible with commercial membranes such as polypropylene and polyethylene. Furthermore, the performance can be optimized from low load to high load through concentration gradient control, providing a low-cost and easily scalable technical path for the industrial production of functional membranes.

[0023] Furthermore, other beneficial effects of the present invention will be mentioned in the specific embodiments. Attached Figure Description

[0024] Figure 1 The images show the morphology of the diaphragm before and after modification in this scheme.

[0025] Figure 2 Field emission scanning electron microscope image of COF-functionalized septum;

[0026] Figure 3 The diagram shows the mechanical strength test results of the COFs-functionalized diaphragm in Example 2. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order.

[0029] Existing technologies suffer from problems such as uneven distribution of functional materials, insufficient internal pore filling, and difficulty in loading high-content functional materials. To address these issues, this solution provides a method for functionalizing COFs in lithium-ion battery separators based on catalyst concentration regulation, comprising the following steps:

[0030] S1. Solution preparation: Dissolve trimesin in dichloromethane to obtain solution A; dissolve the catalyst in deionized water to obtain solution B; dissolve tris(4-aminophenyl)amine in N,N-dimethylformamide to obtain solution C;

[0031] In the illustrated embodiment, the catalyst in solution B is acetic acid. The catalyst can also be a water-soluble organic acid such as formic acid or propionic acid. Organic acids can catalyze the reaction of trimesin and tris(4-aminophenyl)amine to proceed more quickly.

[0032] Catalyst concentration of 1-9 mol L -1 In the illustrated embodiment, the catalyst concentration is 3 mol L. -1 6 mol / L -1 Or 9 mol L -1 ;

[0033] In the illustrated embodiment, the concentration of pyromellitic aldehyde in solution A is 4.2 mmol / L. -1 The concentration of tris(4-aminophenyl)amine in solution C is 4.2 mmol / L. -1 .

[0034] S2. In-situ COFs functionalization: A three-layer system is formed by sequentially stacking solutions A, B, and C. A commercial lithium battery separator is placed at the interface between solution A and solution B to react. After the reaction, the separator is washed and dried to obtain a COFs functionalized separator.

[0035] In the illustrated embodiment, the commercial lithium battery separator in step S2 is selected from one of polypropylene separator, polyethylene separator, or PP / PE composite separator.

[0036] In the embodiment shown, the reaction time is 5-10 days, the drying temperature in step S2 is 60 °C, and the drying time is 12 h.

[0037] In the illustrated embodiment, the washing is performed by sequentially cleaning with dichloromethane, ethanol, acetone, and N,N-dimethylformamide.

[0038] The amounts of solutions A, B, and C can be adjusted according to the reaction. In the embodiment shown, the volume ratio of solutions A, B, and C is 8:2:5.

[0039] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0040] Example 1

[0041] Preparation of solution: Dissolve trimesaldehyde in dichloromethane to a concentration of 4.2 mmol / L. -1 Solution A was obtained; acetic acid was dissolved in deionized water to a concentration of 3 mol / L. -1 Solution B was obtained; tris(4-aminophenyl)amine was dissolved in N,N-dimethylformamide to a concentration of 4.2 mmol / L. -1 Solution C is obtained;

[0042] In-situ COFs functionalization: A three-layer system was formed by stacking solutions A, B, and C in a volume ratio of 8:2:5. A polypropylene (PP) membrane was placed at the interface between solutions A and B. After reacting for 7 days, the membrane was washed sequentially with dichloromethane, ethanol, acetone, and N,N-dimethylformamide. After drying at 60 °C for 12 h, the COFs functionalized membrane was obtained.

[0043] Example 2

[0044] The only difference between this embodiment and Example 1 is that the acetic acid concentration in solution B is 6 mol / L. -1 The remaining preparation process is the same as in Example 1.

[0045] Example 3

[0046] The only difference between this embodiment and Example 1 is that the acetic acid concentration in solution B is 9 mol / L.-1 The remaining preparation process is the same as in Example 1.

[0047] Example 4

[0048] The only difference between this embodiment and Example 2 is that the reaction time is 5 days; the rest of the preparation process is the same as in Example 2.

[0049] Example 5

[0050] The only difference between this embodiment and Embodiment 2 is that the reaction time in step S2 is 10 days, while the rest of the preparation process is the same as in Embodiment 2.

[0051] Example 6

[0052] The only difference between this embodiment and Embodiment 2 is that the polypropylene (PP) film is replaced with a polyethylene (PE) film for the modification reaction; the rest of the preparation process is the same as in Embodiment 2.

[0053] Example 7

[0054] The only difference between this embodiment and Example 2 is that the polypropylene (PP) membrane is replaced with a PP / PE composite membrane for the modification reaction; the rest of the preparation process is the same as in Example 2.

[0055] Figure 1 These are morphological diagrams of the diaphragms in Examples 1-3, wherein... Figure 1 (a) is a morphological diagram of polypropylene (PP); Figure 1 (b) is a morphological diagram of the COFs-functionalized diaphragm in Example 1; Figure 1 (c) is a morphological diagram of the COFs-functionalized diaphragm in Example 2; Figure 1 (d) is a morphological diagram of the COFs-functionalized membrane in Example 3; Figure 1 It can be seen that the modified PP membrane was successfully functionalized with COFs;

[0056] Figure 2 The image shows a field emission scanning electron microscope (SEM) image of a COF-functionalized diaphragm, in which... Figure 2 (a) is a SEM image of the COFs-functionalized diaphragm in Example 1; Figure 2 (b) is a SEM image of the COFs-functionalized diaphragm in Example 2; Figure 2 (c) is a SEM image of the COFs-functionalized membrane in Example 3; 3 mol L -1 At that time, COFs formed a non-uniform layer on the membrane surface, with an internal pore filling rate of 40-60%; 6 mol L -1 At that time, COFs formed a dense layer on the membrane surface and uniformly filled the internal pores of the membrane through a layer-by-layer growth mode, with a filling rate of 80-90%; 9 mol L-1 When COFs form a loose layer, the membrane is easy to float, and the internal pore filling rate is <50%.

[0057] At 6 mol L -1 At certain concentrations, COFs uniformly fill the internal pores of the membrane in a layered penetration mode, increasing the filling rate by 40-50% compared to traditional surface modification methods, forming a "continuous functional network of surface and pores," which can significantly enhance the electrochemical performance of the membrane; using 6 mol L... -1 The optimal growth mode at acetic acid concentration, the synergistic effect of chemisorption of tertiary amine groups (-N⁻) in COF structure and physical confinement of narrow pore size, has the potential to improve the adsorption effect of polysulfides in lithium-sulfur batteries and reduce interfacial diffusion resistance.

[0058] Figure 3 The diagram shows the mechanical strength test results of the COFs-functionalized membrane in Example 2. Figure 3 (a) is a bending test; Figure 3 (b) is the scratch test; the balance between functionalization and mechanical strength is achieved by adjusting the catalyst concentration, 6 mol L -1 The COFs functionalized separator prepared at the specified concentration maintains structural integrity and high mechanical strength after bending and scratching, breaking through the bottleneck of insufficient mechanical properties of interfacial self-assembled membranes and meeting the stringent requirements of battery assembly for the mechanical properties of separators.

[0059] Examples 4-7 show that by adjusting the reaction time and modifying the raw materials, similar modification effects can be achieved. This demonstrates that the method of this scheme is compatible with commercial separators such as polypropylene (PP) and polyethylene (PE). Therefore, this scheme provides a low-cost and easily scalable technical path for the industrial production of functional separators for lithium-sulfur batteries.

[0060] To better illustrate the present invention, numerous specific details have been provided in the detailed embodiments described above. Those skilled in the art should understand that the present invention can be practiced even without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of the present invention.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for functionalizing COFs in lithium-ion battery separators based on catalyst concentration regulation, characterized in that, Includes the following steps: S1. Solution preparation: Dissolve trimesin in dichloromethane to obtain solution A; dissolve the catalyst in deionized water to obtain solution B; dissolve tris(4-aminophenyl)amine in N,N-dimethylformamide to obtain solution C; S2. In-situ COFs functionalization: A three-layer system is formed by sequentially stacking solutions A, B, and C. A commercial lithium battery separator is placed at the interface between solution A and solution B to react. After the reaction, the separator is washed and dried to obtain a COFs functionalized separator.

2. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, The catalyst in solution B of step S1 is any one of formic acid, acetic acid or propionic acid.

3. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, The catalyst in solution B of step S1 is acetic acid.

4. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, The catalyst concentration in solution B of step S1 is 1-9 mol / L. -1 .

5. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, The catalyst concentration in solution B in step S1 is 6 mol / L. -1 The concentration of pyromellitic aldehyde in solution A in step S1 is 4.2 mmol / L. -1 The concentration of tris(4-aminophenyl)amine in solution C in step S1 is 4.2 mmol / L. -1 .

6. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, The commercial lithium battery separator mentioned in step S2 is selected from one of polypropylene separator, polyethylene separator, or PP / PE composite separator.

7. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, The reaction time in step S2 is 5-10 days.

8. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, The washing in step S2 is performed by sequentially washing with dichloromethane, ethanol, acetone and N,N-dimethylformamide.

9. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, The reaction time in step S2 is 7 days; the drying temperature in step S2 is 60 ℃ and the drying time is 12 h.

10. The method for functionalizing COFs in lithium battery separators based on catalyst concentration regulation according to claim 1, characterized in that, In step S2, the volume ratio of solution A, solution B, and solution C is 8:2:5.

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