Furyl polyamide lithium battery diaphragm and preparation method thereof

Abstract

The invention discloses a furyl polyamide lithium battery diaphragm and a preparation method thereof, and belongs to the technical field of lithium battery diaphragms.The preparation method of the diaphragm comprises the following steps that S1, furyl polyamide, polyvinylidene fluoride and modified inorganic filler are added into a solvent and stirred and mixed, and a mixed solution is obtained; s2, adding a viscosity modifier into the mixed solution, and stirring and mixing to obtain coating slurry; s3, coating one side of a base membrane with the coating slurry, and performing vacuum drying to obtain the furyl polyamide lithium battery diaphragm, the coating slurry is prepared from the following raw materials in parts by weight: 15 to 30 parts of polyvinylidene fluoride, 25 to 50 parts of furyl polyamide, 10 to 30 parts of modified inorganic filler, 5 to 10 parts of viscosity modifier and 100 parts of solvent; the lithium battery diaphragm prepared from the coating slurry not only has excellent heat resistance, but also has good wettability, the cycle and power performance of the battery can be effectively improved, and the safety performance such as thermal runaway of the battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery separators, and particularly relates to a furan-based polyamide lithium battery separator and a preparation method thereof. Background Art

[0002] Lithium batteries are widely used in industrial and civil fields and mainly consist of four functional components: a positive electrode, an electrolyte, a separator, and a negative electrode. In the structure of a lithium battery, the separator is one of the key inner components. Its main function is to separate the positive and negative electrodes of the battery to prevent the battery from short-circuiting due to contact between the positive and negative electrodes, and at the same time provide a channel for the migration of lithium ions. The quality of the separator performance plays a key role in the battery life, efficiency, and safety performance, etc.

[0003] Currently, the most commonly used lithium battery separator materials on the market are: polyolefin separators such as polyethylene and polypropylene. However, the thermal stability of such separators is poor. When the temperature approaches the melting point of the polymer, the separator will shrink and collapse at multiple scales, the coverage area will decrease, and it cannot strictly block the positive and negative electrodes, resulting in an internal short circuit of the battery. To this end, a slurry is usually coated on the surface of the polyolefin separator to improve the heat resistance of the polyolefin separator. The coating slurry mainly consists of aramid and / or inorganic fillers. Aramid has high heat resistance, but aramid belongs to petroleum-based polyamide materials, which are non-renewable resources and do not conform to the concept of green development.

[0004] In recent years, the production of polyamide using furan compounds instead of petroleum-based compounds terephthalic acid has received increasing attention, but it is less used in lithium battery separators. Therefore, the present invention provides a furan-based polyamide lithium battery separator to reduce the dependence on petroleum-based energy and promote the development of the green economy. Summary of the Invention

[0005] The purpose of the present invention is to provide a furan-based polyamide lithium battery separator and a preparation method thereof to reduce the dependence of existing lithium battery separators on petroleum-based energy.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A preparation method of a furan-based polyamide lithium battery separator includes the following steps:

[0008] S1. Add furan-based polyamide, polyvinylidene fluoride, and a modified inorganic filler to a solvent, stir and mix to obtain a mixed solution;

[0009] S2. Add a viscosity regulator to the mixed solution, stir and mix to obtain a coating slurry;

[0010] S3. Coat the coating slurry on one side of a base film, and then perform vacuum drying to obtain a furan-based polyamide lithium battery separator.

[0011] Further, the base film is a polypropylene or polyethylene film with a thickness of 5 - 12 μm.

[0012] Further, the coating amount of the coating slurry is 5 - 20 g / m 2 .

[0013] Further, the temperature of the vacuum drying is 60 - 100 °C, and the time of the vacuum drying is 8 - 14 h. By controlling the temperature and time of the vacuum drying within the above ranges in the present invention, the complete removal of the organic solvent is achieved.

[0014] Further, the coating slurry comprises the following raw materials in parts by weight:

[0015] 15 - 30 parts of polyvinylidene fluoride, 25 - 50 parts of furan-based polyamide, 10 - 30 parts of modified inorganic filler, 5 - 10 parts of viscosity regulator, and 100 parts of solvent.

[0016] Further, the furan-based polyamide is obtained by melt polycondensation of dimethyl furan-2,5-dicarboxylate and aliphatic diamine.

[0017] Further, the aliphatic diamine is hexamethylenediamine or decamethylenediamine.

[0018] Further, the preparation method of the furan-based polyamide comprises the following steps:

[0019] Add dimethyl furan-2,5-dicarboxylate and aliphatic diamine into a reaction kettle, then add tetrabutyl titanate. Under the protection of nitrogen, heat up to 90 °C and stir for 2 - 3 h, then evacuate to -0.01 MPa, heat up to 210 °C and stir for 1 h, and stir at 230 °C for 1 h to obtain the furan-based polyamide.

[0020] Further, in the above preparation method, the molar ratio of dimethyl furan-2,5-dicarboxylate to aliphatic diamine is 1:1.05, and the dosage of tetrabutyl titanate is 1% of the mass of dimethyl furan-2,5-dicarboxylate.

[0021] Further, the modified inorganic filler is an inorganic filler modified with silane-polyethylene glycol-maleimide (Mal-PEG-Silane).

[0022] Further, the inorganic filler is spherical mesoporous silica and halloysite nanotubes.

[0023] Further, the preparation method of the modified inorganic filler comprises the following steps:

[0024] Add silane-polyethylene glycol-maleimide to the ethanol aqueous solution. After stirring evenly, add spherical mesoporous silica and halloysite nanotubes, and stir and react at 60-80 °C for 20 h. Centrifuge to separate the solid and liquid. Wash the solid with deionized water and then dry to obtain the modified inorganic filler.

[0025] Furthermore, in the above preparation method, the dosage ratio of silane-polyethylene glycol-maleimide, ethanol aqueous solution, spherical mesoporous silica and halloysite nanotubes is 0.04-0.18 g: 100-150 mL: 1-3 g: 3 g, and the mass fraction of the ethanol aqueous solution is 80-95%.

[0026] Furthermore, the molecular weight of the silane-polyethylene glycol-maleimide is 1-10K.

[0027] Furthermore, the particle size of the spherical mesoporous silica is ≤20 μm, preferably mesoporous silica XD-S05J, purchased from Wuhu Jikang New Materials Technology Co., Ltd.

[0028] Furthermore, the viscosity regulator is at least one of anhydrous ethanol, N,N-dimethylacetamide, dimethyl carbonate, and diphenyl carbonate.

[0029] Furthermore, the solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0030] Furthermore, a furanyl polyamide lithium battery separator is prepared by the above preparation method.

[0031] Advantages of the present invention:

[0032] The present invention provides a furanyl polyamide lithium battery separator. A coating slurry is prepared from furanyl polyamide, polyvinylidene fluoride, and modified inorganic filler. Among them, polyvinylidene fluoride has good adhesiveness, furanyl polyamide has good heat resistance and environmental friendliness, and the modified inorganic filler has good dispersibility. As a result, the lithium battery separator prepared from this coating slurry not only has excellent heat resistance but also has good wettability, which can effectively improve the battery cycle and power performance and improve the safety performance such as battery thermal runaway.

[0033] The present invention uses spherical mesoporous silica and halloysite nanotubes treated with silane-polyethylene glycol-maleimide as modified inorganic fillers. The siloxane structure on the molecular chain of silane-polyethylene glycol-maleimide hydrolyzes to produce silanols, which react with the hydroxyl groups on the surfaces of spherical mesoporous silica and halloysite nanotubes to obtain modified inorganic fillers. After being treated with silane-polyethylene glycol-maleimide, the dispersibility of the inorganic fillers in the slurry is significantly improved. Moreover, the maleimide structure on the molecular chain of silane-polyethylene glycol-maleimide can undergo a [4+2] cycloaddition reaction with the furan ring in the furan-based polyamide. This reaction can tightly bond the inorganic filler particles. On the one hand, it reduces the phenomenon of inorganic filler detachment. On the other hand, it forms an inorganic filler network on the surface of the base film, strengthening the heat resistance and mechanical properties of the separator. In addition, the molecular chain of silane-polyethylene glycol-maleimide also carries abundant polar ether bonds, which is beneficial to improving the affinity between the separator and the electrolyte and increasing the liquid absorption rate of the separator.

[0034] The present invention uses spherical mesoporous silica and halloysite nanotubes as inorganic fillers. They have rich pore structures, which are beneficial to increasing the liquid absorption rate of the separator. Moreover, compared with single fillers, the synergistic effect between different-shaped fillers can enhance the stability of the inorganic network, so the heat resistance and mechanical properties of the separator can be effectively enhanced. Detailed implementation manners

[0035] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer, the following further details the present application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] It should be understood that in various embodiments of the present application, the magnitudes of the serial numbers of the various processes do not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of the various processes should be determined by their functions and internal logics, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0037] The weights of the relevant components mentioned in the specification of the embodiments of the present application can not only refer to the specific contents of the components, but also represent the proportional relationships between the weights of the components. Therefore, as long as the contents of the relevant components in the specification of the embodiments of the present application are enlarged or reduced in proportion, they are within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass described in the specification of the embodiments of the present application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0038] Unless otherwise defined, all professional terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0039] In the following Example 1 and Comparative Examples, the polyvinylidene fluoride is polyvinylidene fluoride HSV900; the spherical mesoporous silica is mesoporous silica XD-S05J, purchased from Wuhu Jikang New Material Technology Co., Ltd.; the molecular weight of silane-polyethylene glycol-maleimide is 5K, purchased from Beijing Huawei Ruike Chemical Technology Co., Ltd. Unless otherwise specified, other raw materials, reagents, instruments and equipment can be obtained through market purchase or can be prepared by existing methods.

[0040] The technical solutions of the present application will be described below through specific examples and comparative examples.

[0041] Preparation Example 1

[0042] The preparation of the modified inorganic filler is as follows:

[0043] Add 0.04 g of silane-polyethylene glycol-maleimide to 100 mL of an ethanol aqueous solution with a mass fraction of 80-95%. After stirring evenly, add 1 g of spherical mesoporous silica and 3 g of halloysite nanotubes, and stir and react at 60 °C for 20 h. Centrifuge to separate the solid and liquid. Wash the solid with deionized water and then dry to obtain the modified inorganic filler.

[0044] Preparation Example 2

[0045] The preparation of the modified inorganic filler is as follows:

[0046] Add 0.1 g of silane-polyethylene glycol-maleimide to 120 mL of an ethanol aqueous solution with a mass fraction of 85%. After stirring evenly, add 2 g of spherical mesoporous silica and 3 g of halloysite nanotubes, and stir and react at 70 °C for 20 h. Centrifuge to separate the solid and liquid. Wash the solid with deionized water and then dry to obtain the modified inorganic filler.

[0047] Preparation Example 3

[0048] The preparation of the modified inorganic filler is as follows:

[0049] Add 0.18 g of silane-polyethylene glycol-maleimide to 150 mL of an ethanol aqueous solution with a mass fraction of 95%. After stirring evenly, add 3 g of spherical mesoporous silica and 3 g of halloysite nanotubes, and stir and react at 80 °C for 20 h. Centrifuge to separate the solid and liquid. Wash the solid with deionized water and then dry to obtain the modified inorganic filler.

[0050] Control Example 1

[0051] Preparation of modified inorganic filler. Compared with Preparation Example 1, the only difference is that "silane-polyethylene glycol-maleimide" in Preparation Example 1 is replaced with an equal mass of "carboxyl-polyethylene glycol-silane". The molecular weight of carboxyl-polyethylene glycol-silane is 5K, and it is purchased from Shandong Baositai Medical Materials Co., Ltd.

[0052] Control Example 2

[0053] Preparation of modified inorganic filler. Compared with Preparation Example 1, the only difference is that "silane-polyethylene glycol-maleimide" in Preparation Example 1 is replaced with an equal mass of "γ-aminopropyltriethoxysilane".

[0054] Control Example 3

[0055] Preparation of modified inorganic filler. Compared with Preparation Example 1, the only difference is that "spherical mesoporous silica" in Preparation Example 1 is replaced with an equal mass of "halloysite nanotubes".

[0056] Control Example 4

[0057] Preparation of modified inorganic filler. Compared with Preparation Example 1, the only difference is that "halloysite nanotubes" in Preparation Example 1 is replaced with an equal mass of "spherical mesoporous silica".

[0058] Example 1

[0059] A preparation method of a furanyl polyamide lithium battery separator includes the following steps:

[0060] S1. Add furanyl polyamide, polyvinylidene fluoride, and modified inorganic filler to N-methylpyrrolidone, stir and mix to obtain a mixed solution;

[0061] S2. Add absolute ethanol to the mixed solution, stir and mix to obtain a coating slurry;

[0062] S3. Coat the coating slurry on one side of a polypropylene base film with a thickness of 12 μm, and the coating amount is 5 g / m 2 , and then perform vacuum drying. The temperature of the vacuum drying is preferably 60 °C, and the time of the vacuum drying is 8 h to obtain a furanyl polyamide lithium battery separator.

[0063] The coating slurry includes the following raw materials in parts by weight:

[0064] 15 parts of polyvinylidene fluoride, 25 parts of furanyl polyamide, 10 parts of the modified inorganic filler of Preparation Example 1, 5 parts of absolute ethanol, and 100 parts of N-methylpyrrolidone.

[0065] The preparation method of the furanyl polyamide includes the following steps:

[0066] Add 1 mol of dimethyl furan-2,5-dicarboxylate and 1.05 mol of hexamethylenediamine into a reaction kettle, then add tetrabutyl titanate. Under the protection of nitrogen, heat up to 90 °C and stir for 2 h. Then evacuate to -0.01 MPa, heat up to 210 °C and stir for 1 h, and stir at 230 °C for 1 h to obtain furanyl polyamide. The dosage of tetrabutyl titanate is 1% of the mass of dimethyl furan-2,5-dicarboxylate.

[0067] Example 2

[0068] A preparation method of a furanyl polyamide lithium battery separator includes the following steps:

[0069] S1. Add furanyl polyamide, polyvinylidene fluoride, and modified inorganic filler into N-methylpyrrolidone, and stir and mix to obtain a mixed solution;

[0070] S2. Add absolute ethanol to the mixed solution and stir and mix to obtain a coating slurry;

[0071] S3. Coat the coating slurry on one side of a polypropylene base film with a thickness of 12 μm, and the coating amount is 10 g / m 2 , and then vacuum dry at a temperature of 80 °C for 10 h to obtain a furanyl polyamide lithium battery separator.

[0072] The coating slurry includes the following raw materials in parts by weight:

[0073] 20 parts of polyvinylidene fluoride, 35 parts of furanyl polyamide, 20 parts of the modified inorganic filler of Preparation Example 1, 8 parts of absolute ethanol, and 100 parts of N-methylpyrrolidone.

[0074] The preparation method of the furanyl polyamide includes the following steps:

[0075] Add 1 mol of dimethyl furan-2,5-dicarboxylate and 1.05 mol of hexamethylenediamine into a reaction kettle, then add tetrabutyl titanate. Under the protection of nitrogen, heat up to 90 °C and stir for 3 h. Then evacuate to -0.01 MPa, heat up to 210 °C and stir for 1 h, and stir at 230 °C for 1 h to obtain furanyl polyamide. The dosage of tetrabutyl titanate is 1% of the mass of dimethyl furan-2,5-dicarboxylate.

[0076] Example 3

[0077] A preparation method of a furanyl polyamide lithium battery separator includes the following steps:

[0078] S1. Add furanyl polyamide, polyvinylidene fluoride, and modified inorganic filler into N-methylpyrrolidone, and stir and mix to obtain a mixed solution;

[0079] S2. Add absolute ethanol to the mixed solution, stir and mix to obtain a coating slurry;

[0080] S3. Coat the coating slurry on one side of a polypropylene base film with a thickness of 12 μm, and the coating amount is 10 g / m 2 . Then, perform vacuum drying at a temperature of 100 °C for 14 h to obtain a furan-based polyamide lithium battery separator.

[0081] The coating slurry comprises the following raw materials in parts by weight:

[0082] 30 parts of polyvinylidene fluoride, 50 parts of furan-based polyamide, 30 parts of the modified inorganic filler of Preparation Example 1, 10 parts of absolute ethanol, and 100 parts of N-methylpyrrolidone.

[0083] The preparation method of the furan-based polyamide comprises the following steps:

[0084] Add 1 mol of dimethyl furan-2,5-dicarboxylate and 1.05 mol of hexamethylenediamine to a reaction kettle, then add tetrabutyl titanate. Under nitrogen protection, heat up to 90 °C and stir for 3 h. Then, evacuate to -0.01 MPa, heat up to 210 °C and stir for 1 h, and heat up to 230 °C and stir for 1 h to obtain furan-based polyamide. The dosage of tetrabutyl titanate is 1% of the mass of dimethyl furan-2,5-dicarboxylate.

[0085] Example 4

[0086] A preparation method of a furan-based polyamide lithium battery separator, compared with Example 2, the difference is only that the modified inorganic filler in Example 2 is replaced with the product obtained in Preparation Example 2.

[0087] Example 5

[0088] A preparation method of a furan-based polyamide lithium battery separator, compared with Example 2, the difference is only that the modified inorganic filler in Example 2 is replaced with the product obtained in Preparation Example 3.

[0089] Comparative Example 1

[0090] A preparation method of a furan-based polyamide lithium battery separator, compared with Example 1, the difference is only that the modified inorganic filler in Example 1 is replaced with the product obtained in Control Example 1.

[0091] Comparative Example 2

[0092] A preparation method of a furan-based polyamide lithium battery separator, compared with Example 1, the difference is only that the modified inorganic filler in Example 1 is replaced with the product obtained in Control Example 2.

[0093] Comparative Example 3

[0094] A preparation method of a furanyl polyamide lithium battery separator, compared with Example 3, the difference is only that the modified inorganic filler in Example 3 is replaced with the product obtained in Comparative Example 3.

[0095] Comparative Example 4

[0096] A preparation method of a furanyl polyamide lithium battery separator, compared with Example 3, the difference is only that the modified inorganic filler in Example 3 is replaced with the product obtained in Comparative Example 4.

[0097] Perform performance tests on the furanyl polyamide lithium battery separators obtained in Examples 1 - 5 and Comparative Examples 1 - 4. The test process is as follows:

[0098] (1) Refer to the liquid absorption rate and thermal shrinkage rate recorded in the patent application with the publication number CN118888974A to test the liquid absorption rate and thermal shrinkage rate of the separators in the examples and comparative examples of this application;

[0099] (2) Refer to the standard GB / T 36363 - 2018 "Polyolefin Separators for Lithium - Ion Batteries" to test the tensile strength of the separators;

[0100] The results are shown in Table 1:

[0101] Table 1

[0102]

[0103] Analyzing the data recorded in Table 1, it can be seen that the liquid absorption rate of the lithium battery separators obtained in Examples 1 - 5 is 141.2 - 154.3%, the 1h MD thermal shrinkage rate at 150 °C is 0.4 - 0.7%, the TD thermal shrinkage rate is 0.3 - 0.6%, the longitudinal tensile strength is 177.3 - 183.3 MPa, and the transverse tensile strength is 178.1 - 184.7 MPa. This shows that the separator prepared by the present invention has good heat - resistant performance, mechanical performance, and liquid - washing performance.

[0104] Specifically analyzing the test results in Example 1 and Comparative Example 1, when replacing "silane - polyethylene glycol - maleimide" with an equal mass of "carboxyl - polyethylene glycol - silane" to prepare the modified inorganic filler, due to the lack of maleimide structure in carboxyl - polyethylene glycol - silane, it is difficult to undergo a [4 + 2] cycloaddition reaction with the furan ring in furanyl polyamide, resulting in poor binding degree of the coating filler, and ultimately manifested as a significant increase in thermal shrinkage rate and a significant decrease in mechanical properties.

[0105] Specifically analyzing the test results in Example 1 and Comparative Example 2, when replacing "silane - polyethylene glycol - maleimide" in Preparation Example 1 with an equal mass of "γ - aminopropyltriethoxysilane" to prepare the modified inorganic filler, due to the absence of polyether segments and maleimide, the liquid absorption, thermal stability, and mechanical properties of the separator are all significantly reduced.

[0106] Specifically analyzing the test results in Example 3, Comparative Example 3 and Comparative Example 4, it can be seen that, compared with a single filler, the synergistic effect between spherical mesoporous silica with different shapes and halloysite nanotubes can enhance the stability of the inorganic network, so the heat resistance and mechanical properties of the separator can be effectively enhanced.

[0107] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0108] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a furan-based polyamide lithium battery separator, characterized in that: The following steps are involved: S1, adding furan-based polyamide, polyvinylidene fluoride, and modified inorganic filler into a solvent, stirring and mixing to obtain a mixed solution; S2, adding a viscosity modifier to the mixed solution, stirring and mixing, to obtain a coating slurry; S3, coating the coating slurry on one side of the base film, and vacuum drying to obtain a furan-based polyamide lithium battery separator; The coating slurry comprises the following raw materials in parts by weight: 15-30 parts of polyvinylidene fluoride, 25-50 parts of furan-based polyamide, 10-30 parts of modified inorganic filler, 5-10 parts of viscosity modifier, and 100 parts of solvent.

2. The method for preparing a furan-based polyamide lithium battery separator according to claim 1, characterized in that: The furan-based polyamide is obtained from furan-2,5-dicarboxylic acid dimethyl ester and aliphatic diamine by melt polymerization.

3. The method for preparing a furan-based polyamide lithium battery separator according to claim 2, characterized in that: The aliphatic diamine is hexamethylenediamine or decanediamine.

4. The method for preparing a furan-based polyamide lithium battery separator according to claim 1, characterized in that: The preparation method of the modified inorganic filler comprises the following steps: Silane-polyethylene glycol-maleimide is added to an ethanol aqueous solution, stirred evenly, and then spherical mesoporous silica and halloysite nanotubes are added, stirred and reacted at a temperature of 60-80° C. for 20 hours, centrifuged, solid-liquid separated, the solid was washed with deionized water and then dried to obtain a modified inorganic filler.

5. The method for preparing a furan-based polyamide lithium battery separator according to claim 4, characterized in that: The dosage ratio of silane-polyethylene glycol-maleimide, ethanol aqueous solution, spherical mesoporous silica and halloysite nanotubes is 0.04-0.18 g: 100-150 mL: 1-3 g: 3g, the mass fraction of ethanol aqueous solution is 80-95%.

6. The method for preparing a furan-based polyamide lithium battery separator according to claim 4, characterized in that: The molecular weight of the silane-polyethylene glycol-maleimide is 1-10K.

7. The method for preparing a furan-based polyamide lithium battery separator according to claim 4, characterized in that: The particle size of the spherical mesoporous silica is ≤20um.

8. The method for preparing a furan-based polyamide lithium battery separator according to claim 1, characterized in that: The coating slurry coating amount is 5-20g / m 2 .

9. The method for preparing a furan-based polyamide lithium battery separator according to claim 1, characterized in that: The base film is a polypropylene or polyethylene film with a thickness of 5-12 μm.

10. A furan-based polyamide lithium battery separator, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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