Method for planarizing lithium battery separator at two-phase interface and application in preparation of cofs separator

Abstract

The scheme discloses a method for flatly spreading lithium battery diaphragm at two-phase interface and application in preparation of COFs diaphragm, and belongs to the field of battery diaphragm.The method for flatly spreading lithium battery diaphragm at two-phase interface comprises the following steps: S1, preparing solution A by taking 2,4,6-triformylphloroglucinol as solute and a first organic reagent as solvent; and preparing solution B by taking tri(4-aminophenyl)amine as solute and a second organic reagent as solvent; S2, pouring solution A into a beaker, gently placing a lithium battery commercial diaphragm on the surface of solution A, then dropping deionized water to completely cover the surface of solution A and the lithium battery commercial diaphragm, and finally pouring solution B to completely cover the deionized water, so that the problems of unstable flat spreading of the diaphragm at the two-phase interface, unevenness of COFs functionalization caused by bending and shrinkage of the diaphragm and the like are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery separator, in particular to a method for flatting lithium battery separator at two-phase interface and application in preparation of COFs separator. BACKGROUND

[0002] Commercial lithium battery separators generally have lipophilicity and porous structure, but their flatness at the two-phase interface directly affects the in-situ growth efficiency and quality of subsequent functional materials. In the traditional method, the separator is easy to bend, shrink or overall flex due to solvent swelling, uneven interfacial tension and other factors, resulting in uneven growth of covalent organic framework (COFs) functional layer.

[0003] The existing technology faces the following challenges: (1) difficult to locate the two-phase interface: the lipophilic separator is easy to float or sink at the water phase interface, and cannot be stabilized at the two-phase interface; (2) imbalance of swelling stress: excessive solvent swelling leads to uneven stress distribution inside the separator, causing the increase of Gaussian curvature (K=k1×k2), and the deformation of the membrane surface; (3) lack of theoretical basis for flatness regulation: there is no method for accurately regulating the flatness of the separator by coupling physical fields. SUMMARY

[0004] In order to alleviate or partially alleviate the above technical problems, the solution of the present application is as follows:

[0005] The method for flatting lithium battery separator at two-phase interface comprises the following steps:

[0006] S1, preparing solution A with 2,4,6-triformylphloroglucinol as solute and a first organic reagent as solvent; and preparing solution B with tris(4-aminophenyl)amine as solute and a second organic reagent as solvent;

[0007] S2, pouring solution A into a beaker, placing the commercial lithium battery separator on the surface of solution A, then dropping deionized water to completely cover the surface of solution A and the commercial lithium battery separator, and finally pouring solution B to completely cover the deionized water.

[0008] This solution forms an oil-water-oil three-layer system by preparing an aldehyde group-containing monomer-containing bottom oil phase, a middle layer of water phase, and an amine group-containing monomer-containing top oil phase, and sequentially stacking them, and uses the balance of the gravitational field of the separator and the solvent buoyancy, the moderate swelling of the bottom organic solvent to the separator to regulate the difference between the longitudinal and lateral principal curvatures, so that the Gaussian curvature K≈0, realizes the stable flatness of the battery separator at the bottom organic solvent-water two-phase interface, and solves the problem of bending and shrinking of the separator in the traditional process.

[0009] The scheme provides a two-phase interface flat method based on multi-field coupling effect (gravity field, buoyancy, swelling effect), which can control the stable flat of commercial lithium battery separator at the interface through solvent system design, and can provide an ideal environment for functionalized separator preparation, and has the advantages of simple operation and controllable flatness.

[0010] Preferably, the first organic reagent is selected from any one of dichloromethane, trichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1,2-trichloroethane, chloroform, chlorobenzene, bromoethane, nitromethane, dibromomethane or iodomethane.

[0011] Preferably, the second organic reagent is selected from any one of N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, cyclohexanone or 1,4-dioxane.

[0012] More preferably, the first organic reagent is selected from dichloromethane.

[0013] More preferably, the second organic reagent is selected from N,N-dimethylformamide.

[0014] Preferably, the concentration of 2,4,6-triformylphloroglucinol in solution A in step S1 is 3-5 mol / L -1 ; the concentration of tris (4-aminophenyl) amine in solution B is 3-5 mol / L -1 .

[0015] More preferably, the concentration of 2,4,6-triformylphloroglucinol in solution A in step S1 is 4.2 mol / L -1 ; the concentration of tris (4-aminophenyl) amine in solution B is 4.2 mol / L -1 .

[0016] Preferably, the commercial lithium battery separator in step S2 is a polyolefin separator or a non-woven fabric separator.

[0017] Preferably, the polyolefin separator is selected from any one of a polypropylene separator, a polyethylene separator, a PP / PE composite separator or a PP / PE / PP three-layer composite separator.

[0018] The scheme also provides an application of the method for flatting a lithium battery separator at a two-phase interface as described above in the preparation of a COFs separator. The beaker is placed at room temperature for 3-9 days to allow the separator to be fully modified by COFs functionalization. Then the COFs functionalized separator is taken out and washed with organic solvent A, ethanol, acetone and organic solvent C in turn. Finally, the COFs functionalized separator is dried at 40-70 ℃ for 8-24 h.

[0019] The diaphragm adjusts internal stress through the swelling effect of the bottom layer organic solvent, reduces the difference between the longitudinal main curvature (k1) and the transverse main curvature (k2), and the Gaussian curvature K is less than or equal to 0.1 cm-2; the multi-field coupling effect includes the balance effect of the gravity field and the buoyancy, the stress release effect caused by the solvent swelling, and the stable effect of the two-phase interfacial tension on the diaphragm positioning, so that the covalent organic framework (COFs) functional diaphragm can be uniformly polymerized in the preparation process.

[0020] The technical scheme of the present application has the following beneficial technical effects:

[0021] By constructing an oil-water-oil three-layer system, the high-density advantage of the bottom layer organic solvent is used to provide buoyancy support, and the difference between the longitudinal and transverse main curvatures of the diaphragm is adjusted by combining the moderate swelling effect, so that the diaphragm is stably flat at the oil-water two-phase interface, and the Gaussian curvature K is approximately equal to 0, realizing stable flatness, and completely solving the bending and shrinking problem of the diaphragm caused by the imbalance of gravity-buoyancy and uneven swelling stress in the traditional method; the stable flat interface state provides an ideal substrate for in-situ growth of functional materials, ensuring that the covalent organic framework (COFs) nanoparticles are uniformly and continuously nucleated at the interface;

[0022] The method of the present scheme realizes the synergistic optimization of the flatness of the diaphragm and the uniformity of the growth of functional materials through precise regulation of the multi-field coupling effect (gravity field, buoyancy, swelling effect), and provides a universal interface engineering strategy for controllable preparation of functional diaphragms.

[0023] By using the above multi-field coupling effect, the COFs functional material can be uniformly and continuously in-situ polymerized on the diaphragm, significantly improving the overall physical constraint ability of the functional diaphragm; the chemical adsorption of the tertiary amine group in the COFs structure and the physical restriction of the narrow pore size construct a "chemical adsorption-physical interception" double barrier, which can improve the COFs functional quality.

[0024] In addition, the present application also has other beneficial effects which will be mentioned in the specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The front view and top view of the flat polypropylene diaphragm at the two-phase interface in Example 1;

[0026] Figure 2 The morphology of the PP diaphragm at the oil-water two-phase interface;

[0027] Figure 3 The morphology of the COFs functional diaphragm prepared. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0029] In the preparation of the conventional functionalized separator, the separator cannot be stably flattened at the two-phase interface, resulting in problems such as unevenness, low efficiency and low quality of COFs functionalization. The present solution realizes the stable flattening of the separator at the two-phase interface by constructing an oil-water-oil three-layer system based on the multi-field coupling flattening mechanism of the gravity field and buoyancy balance, swelling effect and stress regulation, and interfacial tension synergy of the system, laying a foundation for the subsequent functionalization and modification of the separator of COFs, and has the advantages of simple process and controllable reaction.

[0030] The method for flattening the lithium battery separator at the two-phase interface comprises the following steps:

[0031] S1, preparing solution A with 2,4,6-triformylphloroglucinol as the solute and a first organic reagent as the solvent; and preparing solution B with tris(4-aminophenyl)amine as the solute and a second organic reagent as the solvent;

[0032] In the illustrated embodiment, the first organic reagent is selected from dichloromethane, trichloromethane and carbon tetrachloride, but the first organic reagent is not limited to dichloromethane, trichloromethane and carbon tetrachloride, and can also be selected from any one of 1,2-dichloroethane, 1,1,2-trichloroethane, chloroform, chlorobenzene, bromoethane, nitromethane, dibromomethane or iodomethane.

[0033] The concentration of 2,4,6-triformylphloroglucinol in solution A can be selected from the range of 3-5 mol / L. -1 The concentration of tris(4-aminophenyl)amine in solution B is 3-5 mol / L. -1 For example, in the illustrated embodiment, the concentration of 2,4,6-triformylphloroglucinol is preferably 4.2 mol / L. -1 The concentration of tris(4-aminophenyl)amine in solution B is 4.2 mol / L. -1

[0034] In the illustrated embodiment, the second organic reagent is selected from N,N-dimethylformamide, but the second organic reagent is not limited to N,N-dimethylformamide, and the second organic reagent can also be selected from any one of N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, cyclohexanone or 1,4-dioxane.

[0035] ​S2, pour solution A into a beaker, place a lithium battery commercial separator on the surface of solution A, then drop deionized water to make the surface of solution A and the lithium battery commercial separator be completely covered, and finally pour solution B to make the deionized water be completely covered.

[0036] The lithium battery commercial separator can be a polyolefin separator or a non-woven fabric separator; the polyolefin separator is selected from any one of a polypropylene separator, a polyethylene separator, a PP / PE composite separator, or a PP / PE / PP three-layer composite separator; for example, in the illustrated embodiment, the lithium battery commercial separator is selected from a polypropylene separator.

[0037] The method of flattening the lithium battery separator at the two-phase interface described above can be applied to the preparation of a COFs separator, and a COFs separator can be obtained.

[0038] Hereinafter, the examples of the present application will be described. The examples described below are exemplary and are only used to explain the present application and cannot be understood as a limitation of the present application. If a specific technology or condition is not specified in the examples, it is performed according to the technology or condition described in the literature in the art or according to the product manual. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0039] Example 1

[0040] As Figure 1 shown is a schematic diagram of flattening a polypropylene separator at a two-phase interface, the method is as follows S1, 2,4,6-triformylphloroglucinol is used as a solute, dichloromethane is used as a solvent to prepare solution A with a concentration of 4.2 mol L -1 ; tris(4-aminophenyl)amine is used as a solute, N,N-dimethylformamide is used as a solvent to prepare solution B with a concentration of 4.2 mol L -1 ;

[0041] S2, first pour an appropriate amount of solution A into a beaker, place a polypropylene (PP) separator on the surface of solution A, then drop deionized water to make the surface of solution A and the PP separator be completely covered, and finally pour solution B to make the deionized water be completely covered.

[0042] Example 2

[0043] The beaker in Example 1 was placed at room temperature for 7 days to allow the separator to be fully COFs functionalized, then the COFs functionalized separator was taken out and washed with dichloromethane, ethanol, acetone, and N,N-dimethylformamide in sequence, and finally dried at 60°C for 12 h to obtain a COFs functionalized separator.

[0044] Comparative Example 1

[0045] The difference between the present comparative example and Example 1 is that solvent A used is chloroform, and the method of flattening the lithium battery separator at the two-phase interface is the same as that of Example 1.

[0046] Comparative Example 2

[0047] The difference between the present comparative example and Example 1 is that solvent A used is carbon tetrachloride, and the method of flattening the lithium battery separator at the two-phase interface is the same as that of Example 1.

[0048] Comparative Example 3

[0049] The difference between the present comparative example and Example 2 is that solvent A used is chloroform, and the method of preparing the COFs functionalized separator is the same as that of Example 2.

[0050] Comparative Example 4

[0051] The difference between the present comparative example and Example 2 is that solvent A used is carbon tetrachloride, and the method of preparing the COFs functionalized separator is the same as that of Example 2.

[0052] Figure 2 The morphological images of the PP separators of Example 1, Comparative Examples 1-2 at the two-phase interface are shown, wherein Figure 2 (a) of FIG. 1 is the morphological image of the PP separator in Example 1 at the two-phase interface; Figure 2 (b) of FIG. 1 is the morphological image of the PP separator in Comparative Example 1 at the two-phase interface; Figure 2 (c) of FIG. 1 is the morphological image of the PP separator in Comparative Example 2 at the two-phase interface; the separator is quickly flattened into a circle at the two phases in dichloromethane solvent.

[0053] Figure 3 (a) of FIG. 2 is the morphological image of the COFs functionalized separator in Example 2; Figure 3 (b) of FIG. 2 is the morphological image of the COFs functionalized separator in Comparative Example 3; Figure 3 (c) of FIG. 2 is the morphological image of the COFs functionalized separator in Comparative Example 4, after reaction, 2,4,6-triformylphloroglucinol and tris(4-aminophenyl)amine modify the surface of the PP separator to obtain the COFs functionalized separator.

[0054] In order to better illustrate the present application, numerous specific details are given in the foregoing detailed description. Those skilled in the art will understand that the present application can be implemented without certain specific details. In some examples, methods, means, elements and circuits well known to those skilled in the art are not described in detail in order to highlight the main idea of the present application.

[0055] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of planarizing a lithium battery separator at a two-phase interface, characterized by, The method comprises the following steps: S1, preparing solution A with 2,4,6-triformylphloroglucinol as solute and a first organic reagent as solvent; and preparing solution B with tris(4-aminophenyl)amine as solute and a second organic reagent as solvent; the first organic reagent is selected from any one of dichloromethane, trichloromethane or carbon tetrachloride; and the second organic reagent is selected from N,N-dimethylformamide; S2, pouring solution A into a beaker, gently placing a lithium battery commercial separator on the surface of solution A, then dropping deionized water to completely cover the surface of solution A and the lithium battery commercial separator, and finally pouring solution B to completely cover the deionized water; The lithium battery commercial separator is a polyolefin separator or a non-woven fabric separator.

2. The method of claim 1, wherein the two-phase interface is a liquid-liquid interface. The first organic reagent is selected from dichloromethane.

3. The method of claim 1, wherein the two-phase interface is a liquid-liquid interface. The concentration of the 2,4,6-triformylphloroglucinol in solution A in step S1 is 3-5 mol L -1 ; the concentration of the tris(4-aminophenyl)amine in solution B is 3-5 mol L -1 .

4. The method of claim 3, wherein the two-phase interface is a liquid-liquid interface. The concentration of the 2,4,6-triformylphloroglucinol in solution A in step S1 is 4.2 mol L -1 ; the concentration of tris(4-aminophenyl)amine in solution B is 4.2 mol L -1 .

5. The method of claim 1, wherein the two-phase interface is a liquid-liquid interface. The polyolefin separator is selected from any one of a polypropylene separator, a polyethylene separator, a PP / PE composite separator or a PP / PE / PP three-layer composite separator.

6. Use of the method for flattening a lithium battery separator at a two-phase interface according to any one of claims 1-5 in the preparation of a COFs separator.

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