A high-temperature resistant battery separator and its preparation method

Abstract

The present invention provides a high-temperature resistant battery separator and a preparation method thereof, belonging to the technical field of battery separator preparation; the preparation process includes the following steps: preparation of titanium-doped benzimidazole modified metal-organic framework; preparation of phenolic hydroxyl-containing polyetherimide; preparation of polyetherimide separator; preparation of core-shell structure nanoparticles; preparation of barium titanate fibers; preparation of battery separator. The present invention uses bis(3-amino-4-hydroxyphenyl)propane containing hydroxyl groups and 4,4'-biphenylether dianhydride as raw materials to prepare phenolic hydroxyl-containing polyetherimide, and adds titanium-doped benzimidazole modified metal-organic framework to the phenolic hydroxyl-containing polyetherimide to prepare a polyetherimide separator, and then coats a separator coating on it to prepare a battery separator. The battery separator has excellent mechanical strength and good permeability, and has good high-temperature resistance and is not prone to thermal shrinkage.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separator preparation, and particularly relates to a high-temperature resistant battery separator and a preparation method thereof. Background Art

[0002] With the transformation of the global energy structure and the rapid development of fields such as portable electronic devices and electric vehicles, the demand for lithium-ion batteries is increasing day by day. The safety, energy density, and operating temperature range of batteries have become key factors restricting their wide application. As one of the core components of lithium-ion batteries, the battery separator not only directly affects the internal structural stability of the battery, but also is related to the safety performance and service life of the battery.

[0003] Currently, most battery separator materials on the market use polyolefin polymers such as polypropylene (PP) and polyethylene (PE), which are widely used due to their excellent mechanical strength and good permeability. However, such materials have significant defects. Especially in a high-temperature environment, when the internal temperature of the battery abnormally rises during rapid charging, overcharging, or short-circuiting, the polyolefin separator is prone to thermal shrinkage, melting, or even combustion, seriously threatening the safety of the battery system.

[0004] Therefore, we propose a high-temperature resistant battery separator and a preparation method thereof. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a high-temperature resistant battery separator and a preparation method thereof.

[0006] A preparation method of a high-temperature resistant battery separator includes the following steps:

[0007] S1: Preparation of titanium-doped benzimidazole modified metal-organic framework

[0008] Using zinc nitrate hexahydrate and 2-methylbenzimidazole as raw materials, and adding tetrabutyl titanate and 2-aminobenzimidazole, a titanium-doped benzimidazole modified metal-organic framework is prepared;

[0009] S2: Preparation of phenolic hydroxyl group-containing polyetherimide

[0010] Using bis(3-amino-4-hydroxyphenyl)propane and 4,4'-biphenyl ether dianhydride as raw materials, a phenolic hydroxyl group-containing polyetherimide is prepared;

[0011] S3: Preparation of polyetherimide separator

[0012] Adding the titanium-doped benzimidazole modified metal-organic framework to the phenolic hydroxyl group-containing polyetherimide and N,N-dimethylformamide solution, and then spinning to obtain a polyetherimide separator;

[0013] S4: Preparation of Core-Shell Structure Nanoparticles

[0014] Using zirconium dioxide, aluminum sulfate octadecahydrate, and ammonium formate as raw materials, Al2O3@ZrO2 core-shell structure nanoparticles are prepared;

[0015] S5: Preparation of Barium Titanate Fibers

[0016] Using barium hydroxide octahydrate, acetic acid, and tetrabutyl titanate as raw materials, barium titanate fibers are prepared;

[0017] S6: Preparation of Battery Separator

[0018] Using barium titanate fibers and Al2O3@ZrO2 core-shell structure nanoparticles as fillers to prepare a separator coating, and coating the separator coating on the surface of a polyetherimide separator to prepare a battery separator.

[0019] Further, the preparation of the titanium-doped benzimidazole modified metal-organic framework in step S1 specifically includes the following steps:

[0020] S1.1: Dissolve a mixture of 2-3 parts by weight of zinc nitrate hexahydrate and 0.05-0.08 parts by weight of tetrabutyl titanate in 240-250 parts by weight of methanol, ultrasonicate for 20-30 min, then add 1-2 parts by weight of 2-methylbenzimidazole, and stir and mix to obtain a mixed solution;

[0021] S1.2: Add 5-8 parts by weight of 2-aminobenzimidazole to 50-60 parts by weight of methanol, stir and dissolve to obtain a 2-aminobenzimidazole methanol solution;

[0022] S1.3: Slowly pour 1-2 parts by weight of the mixed solution into 1-2 parts by weight of the 2-aminobenzimidazole methanol solution, react under magnetic stirring for 4-5 h, then perform centrifugation, wash the precipitate with methanol 2-3 times, and then dry to obtain the titanium-doped benzimidazole modified metal-organic framework.

[0023] Further, the preparation of the phenolic hydroxyl group-containing polyetherimide in step S2 specifically includes the following steps:

[0024] S2.1: Under a nitrogen atmosphere and ice bath conditions, mix 1-2 parts by weight of bis(3-amino-4-hydroxyphenyl)propane and 15-18 parts by weight of N,N-dimethylacetamide, perform magnetic stirring until completely dissolved, then add 0.4-0.5 parts by weight of 4,4'-biphenylether dianhydride powder, continue stirring for 20-30 min, add another 0.4-0.5 parts by weight of 4,4'-biphenylether dianhydride powder, continue stirring for 20-30 min, add another 0.4-0.5 parts by weight of 4,4'-biphenylether dianhydride powder, and then stir and react for 5-6 h to obtain a viscous polyamic acid solution;

[0025] S2.2: Cast the viscous polyamic acid solution onto a dust-free flat glass, heat it up on a heating table. First, heat it to 100 - 120 °C and keep it warm for 2 - 3 h, then heat it up to 150 - 160 °C and keep it warm for 2 - 3 h, and finally heat it up to 180 - 200 °C and keep it warm for 2 - 3 h. After cooling to room temperature, a phenolic hydroxyl group-containing polyetherimide film is obtained;

[0026] S2.3: Dissolve 1 - 2 parts by weight of the phenolic hydroxyl group-containing polyetherimide film in 15 - 18 parts by weight of N-methylpyrrolidone, then add deionized water to precipitate. Wash the precipitate until it is neutral and then dry it to obtain the phenolic hydroxyl group-containing polyetherimide.

[0027] Further, the preparation of the polyetherimide separator in step S3 specifically includes the following steps:

[0028] S3.1: Add 2 - 3 parts by weight of the phenolic hydroxyl group-containing polyetherimide to 15 - 20 parts by weight of N,N-dimethylformamide, ultrasonically disperse for 30 - 40 min, then add 3 - 5 parts by weight of titanium-doped benzimidazole modified metal-organic framework, and ultrasonically disperse for another 30 - 40 min to obtain a spinning solution;

[0029] S3.2: Add the spinning solution to a syringe and spin at 23 - 25 °C to obtain fibers. The spinning parameters are: voltage 20 - 25 kV, spinning distance 14 - 16 cm, spinning rate 1 - 2 mL / h, and the rotational speed of the receiving roller 230 - 250 r / min. Obtain a polyetherimide fiber membrane, and dry the polyetherimide fiber membrane in a vacuum environment at 90 - 100 °C for 1 - 2 h to obtain a polyetherimide separator.

[0030] Further, the preparation of the core-shell structured nanoparticles in step S4 specifically includes the following steps:

[0031] S4.1: Add 1 - 2 parts by weight of ammonium formate to 300 - 350 parts by weight of deionized water, stir to dissolve it, then add formic acid to adjust the pH to 4.5 - 4.6, and then add 1 - 2 parts by weight of zirconia and 3 - 5 parts by weight of aluminum sulfate octadecahydrate. Stir and react in a water bath at 70 - 75 °C for 6 - 7 h to obtain a mixed solution;

[0032] S4.2: Centrifuge the mixed solution, then wash the precipitate obtained by centrifugation with deionized water by centrifugation 5 - 8 times. Place the washed precipitate in a muffle furnace and heat it up to 600 - 650 °C at a rate of 10 - 12 °C / min, and calcine for 10 - 12 h to obtain Al2O3@ZrO2 core-shell structured nanoparticles.

[0033] Further, the preparation of the barium titanate fibers in step S5 specifically includes the following steps:

[0034] S5.1: Dissolve 1 - 2 parts by weight of barium hydroxide octahydrate in 15 - 20 parts by weight of acetic acid, stir for 2 - 3 h under a magnetic stirrer, then add 4 - 5 parts by weight of acetylacetone, continue stirring for 10 - 12 min, then add 6 - 7 parts by weight of tetrabutyl titanate, stir at room temperature for 30 - 40 min, and finally add 0.5 - 0.6 parts by weight of PVP, stir for 3 - 4 h to obtain a barium titanate spinning precursor;

[0035] S5.2: Electrospin the barium titanate spinning precursor to obtain barium titanate precursor fibers;

[0036] S5.3: Place the barium titanate precursor fibers in a crucible, calcine in a muffle furnace at 750 - 800 °C for 2 - 3 h, and then grind to obtain barium titanate fibers.

[0037] Further, the preparation of the battery separator in step S6 specifically includes the following steps:

[0038] S6.1: Add 20 - 23 parts by weight of polyvinylidene fluoride and 1.5 - 12 parts by weight of film-forming agent to 50 - 60 parts by weight of deionized water, stir at 60 - 90 °C for 20 - 30 min, then add 15 - 20 parts by weight of barium titanate fibers and 10 - 12 parts by weight of Al2O3@ZrO2 core-shell structure nanoparticles, stir at 300 - 500 r / min for 30 - 40 min to obtain a separator coating;

[0039] S6.2: Coat the separator coating on the surface of a polyetherimide separator, and dry it in vacuum at 70 - 80 °C for 3 - 4 h to obtain a battery separator.

[0040] Further, the parameters of the electrospinning in step S5.2 are: the rotation speed of the receiving end is set to 120 - 130 r / min, the distance from the syringe to the receiver is set to 17 - 18 cm, the voltage is set to 14 - 16 kV, the pushing speed is set to 0.1 - 0.2 mm / min, and a 5 mL syringe is selected.

[0041] Further, the film-forming agent in step S6.1 is a nitrile rubber-modified epoxy resin, specifically a carboxyl-terminated nitrile rubber-modified epoxy resin.

[0042] A high-temperature resistant battery separator is prepared by the preparation method of a high-temperature resistant battery separator described in any one of the above.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] 1. The present invention uses bis(3-amino-4-hydroxyphenyl) propane containing hydroxyl groups and 4,4'-biphenylether dianhydride as raw materials to prepare a phenolic hydroxyl group-containing polyetherimide, and a titanium-doped benzimidazole-modified metal-organic framework is added to the phenolic hydroxyl group-containing polyetherimide to prepare a polyetherimide separator. By doping titanium into the benzimidazole-modified metal-organic framework, after the titanium atoms are doped into the benzimidazole-modified metal-organic framework, they can form new chemical bonds with zinc ions in the framework, nitrogen atoms in benzimidazole, and other elements in the organic ligand. Due to its stronger chemical bonds and more stable structure, the titanium-doped metal-organic framework can better resist the influence of high temperature, thereby effectively improving the high-temperature resistance of the separator. Moreover, the titanium atoms will also coordinate with the phenolic hydroxyl groups in the phenolic hydroxyl group-containing polyetherimide, restricting the movement of molecular chains, thereby increasing the glass transition temperature of the separator, enabling the separator to still maintain good dimensional stability and mechanical properties at higher temperatures, and not easily softening or deforming, which helps to improve the performance of the separator in a high-temperature environment.

[0045] 2. The metal-organic framework in the present invention itself has relatively high thermal stability, and its structure can remain relatively stable at high temperatures. When added to the polyetherimide separator, it can form an intertwined structure with the polyetherimide separator, which can improve the overall thermal stability and inhibit thermal shrinkage in the separator. Benzimidazole is a compound with an aromatic ring structure and has relatively high thermal stability. After being modified onto the metal-organic framework, it can further enhance the framework structure stability of the metal-organic framework. Moreover, the metal ions and organic ligands in the titanium-doped benzimidazole-modified metal-organic framework can interact with the polyetherimide molecular chains. These interactions enable the polyetherimide separator to maintain the stability of its shape and size at high temperatures, improve the overall thermal stability of the separator, and prevent problems such as deformation, softening, and shrinkage of the separator when the battery operates at a higher temperature, ensuring the safety performance and normal operation of the battery. In addition, the metal-organic framework has a rich pore structure. After being modified with benzimidazole, its pore structure is adjusted, making the separator more conducive to ion transport, improving the wetting performance of the separator for the electrolyte, and then enhancing the cycle performance and stability of the battery.

[0046] 3. In the separator coating of the present invention, Al2O3@ZrO2 core-shell structured nanoparticles and barium titanate fibers are added. The synergistic effect of the two can effectively improve the high-temperature resistance and puncture strength of the battery separator. The fibrous barium titanate interweaves with each other in the separator coating to form a network structure, and the Al2O3@ZrO2 core-shell structured nanoparticles are filled in the network structure, which can effectively improve the mechanical properties such as the tensile strength and puncture resistance of the battery separator. In a high-temperature environment, the Al2O3@ZrO2 core-shell structured nanoparticles can effectively disperse heat, reduce local heat concentration, enable the fibrous barium titanate to maintain the structural stability, prevent the thermal shrinkage and deformation of the separator, reduce the risk of separator damage and battery short circuit caused by high temperature, and improve the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The drawings incorporated herein and constituting a part of the specification illustrate embodiments of the present invention and, together with the specification, are further used to explain the principles of the present invention and enable those skilled in the relevant art to implement and use the present invention.

[0048] Figure 1 It is a flowchart of a high-temperature resistant battery separator and its preparation method adopted in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] Hereinafter, a high-temperature resistant battery separator and its preparation method provided by the present invention will be described in detail with reference to the drawings and specific embodiments. At the same time, it should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; moreover, the drawing part is only for more specifically describing the embodiments and is not intended to specifically limit the present invention.

[0050] In the embodiment, the synthesis process of the phenolic hydroxyl group-containing polyetherimide is as follows:

[0051] Embodiment 1

[0052] A preparation method of a high-temperature resistant battery separator, as [[ID= twenty-six ]] Figure 1 shown, includes the following steps:

[0053] S1: Preparation of titanium-doped benzimidazole modified metal-organic framework

[0054] S1.1: Dissolve a mixture of 2 parts by weight of zinc nitrate hexahydrate and 0.05 part by weight of tetrabutyl titanate in 240 parts by weight of methanol, ultrasonicate for 20 min, and then add 1 part by weight of 2-methylbenzimidazole, and stir and mix to obtain a mixed solution;

[0055] S1.2: Add 5 parts by weight of 2-aminobenzimidazole to 50 parts by weight of methanol, stir to dissolve, and obtain a 2-aminobenzimidazole methanol solution;

[0056] S1.3: Slowly pour 1 part by weight of the mixed solution into 1 part by weight of the 2-aminobenzimidazole methanol solution, react under magnetic stirring for 4 h, then centrifuge, wash the precipitate twice with methanol, and then dry to obtain titanium-doped benzimidazole-modified metal-organic framework;

[0057] S2: Preparation of phenolic hydroxyl group-containing polyetherimide

[0058] S2.1: Under a nitrogen atmosphere and ice bath conditions, mix 1 part by weight of bis(3-amino-4-hydroxyphenyl)propane and 15 parts by weight of N,N-dimethylacetamide, stir magnetically until completely dissolved, then add 0.4 part by weight of 4,4'-biphenylether dianhydride powder, continue stirring for 20 min, add another 0.4 part by weight of 4,4'-biphenylether dianhydride powder, continue stirring for 20 min, add another 0.4 part by weight of 4,4'-biphenylether dianhydride powder, and then stir and react for 5 h to obtain a viscous polyamic acid solution;

[0059] S2.2: Cast the viscous polyamic acid solution onto a dust-free flat glass, heat and raise the temperature on a heating table, first heat to 100 °C, keep warm for 2 h, then raise the temperature to 150 °C, keep warm for 2 h, and finally raise the temperature to 180 °C, keep warm for 2 h. After cooling to room temperature, obtain a phenolic hydroxyl group-containing polyetherimide film;

[0060] S2.3: Dissolve 1 part by weight of the phenolic hydroxyl group-containing polyetherimide film in 15 parts by weight of N-methylpyrrolidone, then add deionized water to precipitate, wash the precipitate until neutral and then dry to obtain the phenolic hydroxyl group-containing polyetherimide;

[0061] S3: Preparation of polyetherimide separator

[0062] S3.1: Add 2 parts by weight of the phenolic hydroxyl group-containing polyetherimide to 15 parts by weight of N,N-dimethylformamide, ultrasonically disperse for 30 min, then add 3 parts by weight of the titanium-doped benzimidazole-modified metal-organic framework, and ultrasonically disperse for another 30 min to obtain a spinning solution;

[0063] S3.2: Add the spinning solution to a syringe, spin at 23 °C to obtain a spun fiber. The spinning parameters are: voltage 20 kV, spinning distance 14 cm, spinning rate 1 mL / h, and receiving roll rotation speed 230 r / min. Obtain a polyetherimide fiber membrane, and dry the polyetherimide fiber membrane in a vacuum environment at 90 °C for 1 h to obtain a polyetherimide separator;

[0064] S4: Preparation of core-shell structured nanoparticles

[0065] S4.1: Add 1 part by weight of ammonium formate to 300 parts by weight of deionized water. After stirring to dissolve it, add formic acid to adjust the pH to 4.5. Then add 1 part by weight of zirconia and 3 parts by weight of aluminum sulfate octadecahydrate, and stir and react in a water bath at 70 °C for 6 h to obtain a mixed solution;

[0066] S4.2: Centrifuge the mixed solution, and then centrifuge and wash the obtained precipitate with deionized water 5 times. Place the washed precipitate in a muffle furnace and heat it to 600 °C at a rate of 10 °C / min, and calcine it for 10 h to obtain Al2O3@ZrO2 core-shell structured nanoparticles;

[0067] S5: Preparation of barium titanate fibers

[0068] S5.1: Dissolve 1 part by weight of barium hydroxide octahydrate in 15 parts by weight of acetic acid, stir for 2 h under a magnetic stirrer, then add 4 parts by weight of acetylacetone, continue to stir for 10 min, then add 6 parts by weight of tetrabutyl titanate, stir at room temperature for 30 min, and finally add 0.5 part by weight of PVP and stir for 3 h to obtain a barium titanate spinning precursor;

[0069] S5.2: Electrospinning the barium titanate spinning precursor to obtain barium titanate precursor fibers. The parameters of electrospinning are as follows: the rotation speed of the receiving end is set to 120 r / min, the distance from the syringe to the receiver is set to 17 cm, the voltage is set to 14 kV, the pushing speed is set to 0.1 mm / min, and a 5 mL syringe is selected;

[0070] S5.3: Place the barium titanate precursor fibers in a crucible, calcine them in a muffle furnace at 750 °C for 2 h, and then grind them to obtain barium titanate fibers;

[0071] S6: Preparation of battery separator

[0072] S6.1: Add 20 parts by weight of polyvinylidene fluoride and 1.5 parts by weight of carboxyl-terminated nitrile rubber modified epoxy resin to 50 parts by weight of deionized water, stir at 60 °C for 20 min, then add 15 parts by weight of barium titanate fibers and 10 parts by weight of Al2O3@ZrO2 core-shell structured nanoparticles, and stir at 300 r / min for 30 min to obtain a separator coating;

[0073] S6.2: Coat the separator coating on the surface of a polyetherimide separator and dry it in vacuum at 70 °C for 3 h to obtain a battery separator. Example 2

[0074] A preparation method of a high-temperature resistant battery separator, as Figure 1 shown, includes the following steps:

[0075] S1: Preparation of Titanium-Doped Benzimidazole-Modified Metal-Organic Framework

[0076] S1.1: Dissolve a mixture of 3 parts by weight of zinc nitrate hexahydrate and 0.08 part by weight of tetrabutyl titanate in 250 parts by weight of methanol, ultrasonicate for 20 min, then add 2 parts by weight of 2-methylbenzimidazole, and stir to mix to obtain a mixed solution;

[0077] S1.2: Add 8 parts by weight of 2-aminobenzimidazole to 60 parts by weight of methanol, stir to dissolve to obtain a 2-aminobenzimidazole methanol solution;

[0078] S1.3: Slowly pour 2 parts by weight of the mixed solution into 2 parts by weight of the 2-aminobenzimidazole methanol solution, react under magnetic stirring for 4 h, then centrifuge, wash the precipitate with methanol twice, and then dry to obtain the titanium-doped benzimidazole-modified metal-organic framework;

[0079] S2: Preparation of Phenol Hydroxyl-Containing Polyetherimide

[0080] S2.1: Under a nitrogen atmosphere and ice bath conditions, mix 2 parts by weight of bis(3-amino-4-hydroxyphenyl) propane and 18 parts by weight of N,N-dimethylacetamide, stir magnetically until completely dissolved, then add 0.5 part by weight of 4,4'-biphenyl ether dianhydride powder, continue stirring for 20 min, add another 0.5 part by weight of 4,4'-biphenyl ether dianhydride powder, continue stirring for 20 min, add another 0.5 part by weight of 4,4'-biphenyl ether dianhydride powder, and then stir and react for 5 h to obtain a viscous polyamic acid solution;

[0081] S2.2: Cast the viscous polyamic acid solution onto a dust-free flat glass plate, heat and raise the temperature on a heating table. First heat to 100 °C, keep warm for 2 h, then raise the temperature to 150 °C, keep warm for 2 h, and finally raise the temperature to 180 °C, keep warm for 2 h. After cooling to room temperature, obtain a phenol hydroxyl-containing polyetherimide film;

[0082] S2.3: Dissolve 2 parts by weight of the phenol hydroxyl-containing polyetherimide film in 18 parts by weight of N-methylpyrrolidone, then add deionized water to precipitate, wash the precipitate until neutral and then dry to obtain the phenol hydroxyl-containing polyetherimide;

[0083] S3: Preparation of Polyetherimide Separator

[0084] S3.1: Add 3 parts by weight of the phenol hydroxyl-containing polyetherimide to 20 parts by weight of N,N-dimethylformamide, ultrasonically disperse for 30 min, then add 5 parts by weight of the titanium-doped benzimidazole-modified metal-organic framework, and ultrasonically disperse for another 30 min to obtain a spinning solution;

[0085] S3.2: Add the spinning solution into a syringe and spin at 23°C to obtain a spun fiber. The spinning parameters are: voltage 20 kV, spinning distance 14 cm, spinning rate 1 mL / h, receiving roller rotation speed 230 r / min. Obtain a polyetherimide fiber membrane, and dry the polyetherimide fiber membrane in a vacuum environment at 90°C for 1 h to obtain a polyetherimide separator;

[0086] S4: Preparation of core-shell structured nanoparticles

[0087] S4.1: Add 2 parts by weight of ammonium formate into 350 parts by weight of deionized water. After stirring to dissolve it, add formic acid to adjust the pH to 4.6. Then add 2 parts by weight of zirconium dioxide and 5 parts by weight of aluminum sulfate octadecahydrate, and stir and react in a water bath at 70°C for 6 h to obtain a mixed solution;

[0088] S4.2: Centrifuge the mixed solution, then centrifuge and wash the obtained precipitate with deionized water 5 times. Place the washed precipitate in a muffle furnace and heat it to 600°C at a rate of 10°C / min, and calcine for 10 h to obtain Al2O3@ZrO2 core-shell structured nanoparticles;

[0089] S5: Preparation of barium titanate fibers

[0090] S5.1: Dissolve 2 parts by weight of barium hydroxide octahydrate in 20 parts by weight of acetic acid, stir for 2 h under a magnetic stirrer, then add 5 parts by weight of acetylacetone, continue to stir for 10 min, then add 7 parts by weight of tetrabutyl titanate, stir at room temperature for 30 min, and finally add 0.6 part by weight of PVP and stir for 3 h to obtain a barium titanate spinning precursor;

[0091] S5.2: Electrospin the barium titanate spinning precursor to obtain barium titanate precursor fibers. The electrospinning parameters are: the rotation speed of the receiving end is set to 120 r / min, the distance from the syringe to the receiver is set to 17 cm, the voltage is set to 14 kV, the pushing speed is set to 0.1 mm / min, and a 5 mL syringe is selected;

[0092] S5.3: Place the barium titanate precursor fibers in a crucible, calcine in a muffle furnace at 750°C for 2 h, and then grind to obtain barium titanate fibers;

[0093] S6: Preparation of battery separator

[0094] S6.1: Add 23 parts by weight of polyvinylidene fluoride and 12 parts by weight of carboxyl-terminated acrylonitrile-butadiene rubber modified epoxy resin into 60 parts by weight of deionized water, stir at 90°C for 30 min, then add 20 parts by weight of barium titanate fibers and

[0095] S6.2: Coating the separator coating on the surface of the polyetherimide separator, and drying it in vacuum at 80 °C for 4 h to obtain the battery separator. Example 3

[0096] A preparation method of a high-temperature resistant battery separator, as Figure 1 shown, includes the following steps:

[0097] S1: Preparation of titanium-doped benzimidazole modified metal-organic framework

[0098] S1.1: Dissolving a mixture of 2 parts by weight of zinc nitrate hexahydrate and 0.05 part by weight of tetrabutyl titanate in 240 parts by weight of methanol, ultrasonicating for 30 min, and then adding 1 part by weight of 2-methylbenzimidazole, and stirring and mixing to obtain a mixed solution;

[0099] S1.2: Adding 5 parts by weight of 2-aminobenzimidazole to 50 parts by weight of methanol, stirring and dissolving to obtain a 2-aminobenzimidazole methanol solution;

[0100] S1.3: Slowly pouring 1 part by weight of the mixed solution into 1 part by weight of the 2-aminobenzimidazole methanol solution, reacting under magnetic stirring for 5 h, then centrifuging, washing the precipitate with methanol 3 times, and then drying to obtain the titanium-doped benzimidazole modified metal-organic framework;

[0101] S2: Preparation of phenolic hydroxyl group-containing polyetherimide

[0102] S2.1: Under a nitrogen atmosphere and ice bath conditions, mixing 1 part by weight of bis(3-amino-4-hydroxyphenyl)propane and 15 parts by weight of N,N-dimethylacetamide, and magnetically stirring until completely dissolved, then adding 0.4 part by weight of 4,4'-biphenylether dianhydride powder, continuing to stir for 30 min, adding another 0.4 part by weight of 4,4'-biphenylether dianhydride powder, continuing to stir for 30 min, adding another 0.4 part by weight of 4,4'-biphenylether dianhydride powder, and then stirring and reacting for 6 h to obtain a viscous polyamic acid solution;

[0103] S2.2: Casting the viscous polyamic acid solution onto a dust-free flat glass, heating and raising the temperature on a heating table, first heating to 120 °C, holding for 3 h, then raising the temperature to 160 °C, holding for 3 h, and finally raising the temperature to 200 °C, holding for 3 h, and cooling to room temperature to obtain a phenolic hydroxyl group-containing polyetherimide film;

[0104] S2.3: Dissolving 1 part by weight of the phenolic hydroxyl group-containing polyetherimide film in 15 parts by weight of N-methylpyrrolidone, then adding deionized water to precipitate, washing the precipitate until neutral and then drying to obtain the phenolic hydroxyl group-containing polyetherimide;

[0105] S3: Preparation of Polyetherimide Separator

[0106] S3.1: Add 2 parts by weight of phenol - hydroxyl - containing polyetherimide into 15 parts by weight of N,N - dimethylformamide, ultrasonically disperse for 40 min, then add 3 parts by weight of titanium - doped benzimidazole - modified metal - organic framework, and ultrasonically disperse for another 40 min to obtain a spinning solution;

[0107] S3.2: Add the spinning solution into a syringe, spin - spin at 25 °C to obtain a spun fiber. The spinning parameters are: voltage 25 kV, spinning distance 16 cm, spinning rate 2 mL / h, receiving roller rotation speed 250 r / min, to obtain a polyetherimide fiber membrane. Dry the polyetherimide fiber membrane in a vacuum environment at 100 °C for 2 h to obtain a polyetherimide separator;

[0108] S4: Preparation of Core - Shell Structure Nanoparticles

[0109] S4.1: Add 1 part by weight of ammonium formate into 300 parts by weight of deionized water, stir to dissolve it, then add formic acid to adjust the pH to 4.5. After that, add 1 part by weight of zirconia and 3 parts by weight of aluminum sulfate octadecahydrate, and stir - react in a water bath at 75 °C for 7 h to obtain a mixed solution;

[0110] S4.2: Centrifuge the mixed solution, then centrifuge - wash the precipitate obtained by centrifugation with deionized water 8 times. Place the washed precipitate in a muffle furnace and heat it to 650 °C at a rate of 12 °C / min, and calcine for 12 h to obtain Al2O3@ZrO2 core - shell structure nanoparticles;

[0111] S5: Preparation of Barium Titanate Fibers

[0112] S5.1: Dissolve 1 part by weight of barium hydroxide octahydrate in 15 parts by weight of acetic acid, stir with a magnetic stirrer for 3 h, then add 4 parts by weight of acetylacetone, continue to stir for 12 min, then add 6 parts by weight of tetrabutyl titanate, stir at room temperature for 40 min, and finally add 0.5 part by weight of PVP, stir for 4 h to obtain a barium titanate spinning precursor;

[0113] S5.2: Electrospun the barium titanate spinning precursor to obtain barium titanate precursor fibers. The electrospinning parameters are: the rotation speed of the receiving end is set to 130 r / min, the distance from the syringe to the receiver is set to 18 cm, the voltage is set to 16 kV, the pushing speed is set to 0.2 mm / min, and a 5 mL syringe is selected;

[0114] S5.3: Place the barium titanate precursor fibers in a crucible, calcine in a muffle furnace at 800 °C for 3 h, and then grind to obtain barium titanate fibers;

[0115] S6: Preparation of Battery Separator

[0116] S6.1: Add 20 parts by weight of polyvinylidene fluoride and 1.5 parts by weight of carboxyl-terminated acrylonitrile-butadiene rubber modified epoxy resin into 50 parts by weight of deionized water, stir at 90 °C for 30 min, then add 15 parts by weight of barium titanate fibers and 10 parts by weight of Al2O3@ZrO2 core-shell structure nanoparticles, and stir at 500 r / min for 40 min to obtain the separator coating.

[0117] S6.2: Coat the separator coating on the surface of the polyetherimide separator, and dry it in vacuum at 80 °C for 4 h to obtain the battery separator.

[0118] Air permeability test; Longitudinal and transverse shrinkage rate tests (heat at 180 °C for 4 h, and test the longitudinal and transverse dimension changes before and after heating); Liquid absorption rate test: Immerse it in the electrolyte, take it out and weigh it after 2 h, and calculate the liquid absorption rate according to the weight change before and after; The electrolyte composition is: A solution of ethylene carbonate and dimethyl carbonate with 1 mol / L of LiPF6, and the volume ratio of the solvents ethylene carbonate and dimethyl carbonate is 1:1; Puncture strength: Test according to GB / T 10004-2008. Perform performance tests on Examples 1-3, and the test results are shown in Table 1 for reference.

[0119] Table 1. Performance test results of Examples 1-3

[0120] Example 1 Example 2 Example 3 Air permeability (sec / 100cc) 153 148 152 Transverse shrinkage rate (%) 1 1.3 1.1 Longitudinal shrinkage rate (%) 2.3 2.5 2.4 Puncture strength (gf) 1567 1529 1534 Liquid absorption rate (%) 398 381 387

[0121] It can be seen from the data in Table 1 that the transverse shrinkage rate of the battery separators prepared in Examples 1-3 is 1-1.3%, and the longitudinal shrinkage rate is 2.3-2.5%, indicating that the thermal shrinkage rate is small at high temperature, and the surface battery separators have excellent high-temperature resistance. Moreover, the liquid absorption rate is 381-398%, indicating that the battery separators have good wetting ability for the electrolyte. At the same time, the battery separators have high strength, and this high-strength characteristic helps to improve the overall mechanical stability and safety of the battery and extend the service life of the battery. Therefore, the battery separators prepared in the present invention exhibit excellent comprehensive performance.

[0122] Comparative Example 1

[0123] Compared with Example 1, the difference in Comparative Example 1 is that in Comparative Example 1, the titanium-doped benzimidazole modified metal-organic framework in Steps S1 and S3.1 is removed, and the rest of the steps remain unchanged to prepare the battery separator, which is denoted as Comparative Example 1.

[0124] Comparative Example 2

[0125] Compared with Example 1, the difference in Comparative Example 2 is that in Comparative Example 2, tetrabutyl titanate in step S1.1 is removed, and the benzimidazole-modified metal-organic framework is obtained in step S1.3. The titanium-doped benzimidazole-modified metal-organic framework in step S3.1 is replaced with an equal weight portion of the benzimidazole-modified metal-organic framework, and the battery separator is prepared with the remaining steps unchanged, denoted as Comparative Example 2.

[0126] Comparative Example 3

[0127] Compared with Example 1, the difference in Comparative Example 3 is that in Comparative Example 3, step S1.2 is removed, and the mixture in S1.3 is directly reacted under magnetic stirring, and the battery separator is prepared with the remaining steps unchanged, denoted as Comparative Example 3.

[0128] The data of Example 1 are continued, and the performance tests of Comparative Examples 1-3 are carried out. The test results are shown in Table 2.

[0129] Table 2. Performance test results of Comparative Examples 1-3

[0130] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Transverse shrinkage rate (%) 1 4.3 2.2 3.5 Longitudinal shrinkage rate (%) 2.3 5.9 3.6 4.7 Liquid absorption rate (%) 398 218 389 279

[0131] It can be seen from the data in Table 2 that compared with Example 1, the transverse shrinkage rate and longitudinal shrinkage rate of Comparative Example 2 are both increased, while the liquid absorption rate is decreased. This shows that after titanium atoms are doped into the benzimidazole-modified metal-organic framework, it can better resist the influence of high temperature, and then effectively improve the high-temperature resistance of the separator, so that the separator can still maintain good dimensional stability and mechanical properties at a higher temperature, and is not prone to softening or deformation, which helps to improve the service performance of the separator in a high-temperature environment; compared with Example 1, the transverse shrinkage rate and longitudinal shrinkage rate of Comparative Example 3 are also increased, and the liquid absorption rate is significantly decreased. This shows that after benzimidazole is modified on the metal-organic framework, the framework structure stability of the metal-organic framework can be further enhanced, and the overall thermal stability of the separator can be improved, so that when the battery works at a higher temperature, the separator is not prone to problems such as deformation, softening, and shrinkage, ensuring the safety performance and normal operation of the battery, and after benzimidazole modification, its pore structure is adjusted to improve the wettability of the separator to the electrolyte; while the transverse shrinkage rate and longitudinal shrinkage rate of Comparative Example 1 are higher than those of Comparative Examples 2-3, and are significantly increased compared with Example 1, indicating that the polyetherimide separator prepared by adding the titanium-doped benzimidazole-modified metal-organic framework has better high-temperature resistance, and titanium and benzimidazole can produce a synergistic effect, making the prepared separator not prone to shrinkage at a higher temperature.

[0132] Comparative Example 4

[0133] Compared with Example 1, the difference in Comparative Example 4 is that in Comparative Example 4, the Al2O3@ZrO2 core-shell structure nanoparticles in steps S4 and S6.1 are removed, and the battery separator is prepared with the remaining steps unchanged, denoted as Comparative Example 4.

[0134] Comparative Example 5

[0135] Compared with Example 1, the difference in Comparative Example 5 is that in Comparative Example 5, the barium titanate fibers in steps S5 and S6.1 are removed, and the remaining steps remain unchanged to prepare the battery separator, denoted as Comparative Example 5.

[0136] The data of Example 1 are continued to be used, and the performance tests of Comparative Examples 4-5 are carried out. The test results are shown in Table 3.

[0137] Table 3. Performance test results of Comparative Examples 4-5

[0138] Example 1 Comparative Example 4 Comparative Example 5 Transverse shrinkage rate (%) 1 2.3 2.6 Longitudinal shrinkage rate (%) 2.3 3.5 3.7 Puncture strength (gf) 1567 894 872

[0139] It can be seen from the data in Table 3 that the addition of both Al2O3@ZrO2 core-shell structure nanoparticles and barium titanate fibers improves the high-temperature resistance performance and puncture strength of the battery separator better than adding a single component, indicating that the synergistic effect of the two can effectively improve the high-temperature resistance performance and puncture strength of the battery separator.

[0140] The above embodiments only illustratively explain the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation method of a high-temperature resistant battery separator, characterized in that, It includes the following steps: S1: Preparation of titanium-doped benzimidazole modified metal-organic framework Using zinc nitrate hexahydrate and 2-methylbenzimidazole as raw materials, and adding tetrabutyl titanate and 2-aminobenzimidazole, titanium-doped benzimidazole modified metal-organic framework is prepared; S2: Preparation of phenolic hydroxyl group-containing polyetherimide Using bis(3-amino-4-hydroxyphenyl)propane and 4,4'-oxydiphthalic anhydride as raw materials to prepare phenolic hydroxyl group-containing polyetherimide; S3: Preparation of polyetherimide separator Adding titanium-doped benzimidazole modified metal-organic framework into phenolic hydroxyl group-containing polyetherimide and N,N-dimethylformamide solution, and then spinning to obtain polyetherimide separator; S4: Preparation of core-shell structure nanoparticles Using zirconium dioxide, aluminum sulfate octadecahydrate and ammonium formate as raw materials to prepare Al2O3@ZrO2 core-shell structure nanoparticles; S5: Preparation of barium titanate fibers Using barium hydroxide octahydrate, acetic acid and tetrabutyl titanate as raw materials to prepare barium titanate fibers; S6: Preparation of battery separator Using barium titanate fibers and Al2O3@ZrO2 core-shell structure nanoparticles as fillers to prepare separator coating, and coating the separator coating on the surface of polyetherimide separator to prepare battery separator.

2. The preparation method of a high-temperature resistant battery separator according to claim 1, wherein, Step S1 Preparation of titanium-doped benzimidazole modified metal-organic framework, specifically including the following steps: S1.1: Dissolve a mixture of 2-3 parts by weight of zinc nitrate hexahydrate and 0.05-0.08 parts by weight of tetrabutyl titanate in 240-250 parts by weight of methanol, ultrasonic for 20-30 min, then add 1-2 parts by weight of 2-methylbenzimidazole, and stir and mix to obtain a mixed solution; S1.2: Add 5-8 parts by weight of 2-aminobenzimidazole to 50-60 parts by weight of methanol, stir and dissolve to obtain 2-aminobenzimidazole methanol solution; S1.3: Slowly pour 1-2 parts by weight of the mixed solution into 1-2 parts by weight of 2-aminobenzimidazole methanol solution, and react under magnetic stirring for 4-5 h, then centrifuge, wash the precipitate with methanol for 2-3 times, and then dry to obtain titanium-doped benzimidazole modified metal-organic framework.

3. The preparation method of a high-temperature resistant battery separator according to claim 2, characterized in that, Step S2 Preparation of phenolic hydroxyl group-containing polyetherimide, specifically including the following steps: S2.1: Under nitrogen atmosphere and ice bath condition, mix 1-2 parts by weight of bis(3-amino-4-hydroxyphenyl)propane and 15-18 parts by weight of N,N-dimethylacetamide, and stir magnetically until completely dissolved, then add 0.4-0.5 parts by weight of 4,4'-oxydiphthalic anhydride powder, continue to stir for 20-30 min, add another 0.4-0.5 parts by weight of 4,4'-oxydiphthalic anhydride powder, continue to stir for 20-30 min, add another 0.4-0.5 parts by weight of 4,4'-oxydiphthalic anhydride powder, and then stir and react for 5-6 h to obtain a viscous polyamic acid solution; S2.2: Cast the viscous polyamic acid solution onto a dust-free flat glass, heat it up on a heating table. First, heat it to 100 - 120 °C and keep it warm for 2 - 3 h, then heat it up to 150 - 160 °C and keep it warm for 2 - 3 h, and finally heat it up to 180 - 200 °C and keep it warm for 2 - 3 h. After cooling to room temperature, a phenolic hydroxyl group-containing polyetherimide film is obtained; S2.3: Dissolve 1 - 2 parts by weight of the phenolic hydroxyl group-containing polyetherimide film in 15 - 18 parts by weight of N-methylpyrrolidone, then add deionized water to precipitate. Wash the precipitate until it is neutral and then dry it to obtain the phenolic hydroxyl group-containing polyetherimide.

4. The preparation method of a high-temperature resistant battery separator according to claim 3, characterized in that, Step S3 Preparation of the polyetherimide separator, specifically including the following steps: S3.1: Add 2 - 3 parts by weight of the phenolic hydroxyl group-containing polyetherimide to 15 - 20 parts by weight of N,N-dimethylformamide, ultrasonically disperse for 30 - 40 min, then add 3 - 5 parts by weight of titanium-doped benzimidazole modified metal-organic framework, and ultrasonically disperse for another 30 - 40 min to obtain a spinning solution; S3.2: Add the spinning solution to a syringe and spin at 23 - 25 °C to obtain a spun fiber. The spinning parameters are: voltage 20 - 25 kV, spinning distance 14 - 16 cm, spinning rate 1 - 2 mL / h, and the rotational speed of the receiving roller 230 - 250 r / min. Obtain a polyetherimide fiber membrane, and dry the polyetherimide fiber membrane in a vacuum environment at 90 - 100 °C for 1 - 2 h to obtain a polyetherimide separator.

5. The preparation method of a high-temperature resistant battery separator according to claim 4, characterized in that Step S4 Preparation of the core-shell structure nanoparticles, specifically including the following steps: S4.1: Add 1 - 2 parts by weight of ammonium formate to 300 - 350 parts by weight of deionized water, stir to dissolve it, then add formic acid to adjust the pH to 4.5 - 4.6, and then add 1 - 2 parts by weight of zirconia and 3 - 5 parts by weight of aluminum sulfate octadecahydrate, and stir and react in a water bath at 70 - 75 °C for 6 - 7 h to obtain a mixed solution; S4.2: Centrifuge the mixed solution, then centrifuge and wash the obtained precipitate with deionized water 5 - 8 times. Place the washed precipitate in a muffle furnace and heat it up to 600 - 650 °C at a rate of 10 - 12 °C / min, and calcine for 10 - 12 h to obtain Al2O3@ZrO2 core-shell structure nanoparticles.

6. The preparation method of a high-temperature resistant battery separator according to claim 5, characterized in that Step S5 Preparation of barium titanate fibers, specifically including the following steps: S5.1: Dissolve 1 - 2 parts by weight of barium hydroxide octahydrate in 15 - 20 parts by weight of acetic acid, stir with a magnetic stirrer for 2 - 3 h, then add 4 - 5 parts by weight of acetylacetone, continue to stir for 10 - 12 min, then add 6 - 7 parts by weight of tetrabutyl titanate, stir at room temperature for 30 - 40 min, and finally add 0.5 - 0.6 parts by weight of PVP and stir for 3 - 4 h to obtain a barium titanate spinning precursor; S5.2: Electrospin the barium titanate spinning precursor to obtain barium titanate precursor fibers; S5.3: Place the barium titanate precursor fibers in a crucible, calcine in a muffle furnace at 750 - 800 °C for 2 - 3 h, and then grind to obtain barium titanate fibers.

7. The preparation method of a high-temperature resistant battery separator according to claim 6, characterized in that, Step S6 Preparation of the battery separator, specifically including the following steps: S6.1: Add 20 - 23 parts by weight of polyvinylidene fluoride and 1.5 - 12 parts by weight of film-forming agent into 50 - 60 parts by weight of deionized water, stir at 60 - 90 °C for 20 - 30 min, then add 15 - 20 parts by weight of barium titanate fibers and 10 - 12 parts by weight of Al2O3@ZrO2 core-shell structured nanoparticles, stir at 300 - 500 r / min for 30 - 40 min to obtain the separator coating; S6.2: Coat the separator coating on the surface of the polyetherimide separator, and dry it in vacuum at 70 - 80 °C for 3 - 4 h to obtain the battery separator.

8. The preparation method of a high-temperature resistant battery separator according to claim 6, characterized in that, The parameters of electrospinning in step S5.2 are: the rotation speed of the receiving end is set to 120 - 130 r / min, the distance from the syringe to the receiver is set to 17 - 18 cm, the voltage is set to 14 - 16 kV, the pushing speed is set to 0.1 - 0.2 mm / min, and a 5 mL syringe is selected.

9. The preparation method of a high-temperature resistant battery separator according to claim 7, characterized in that, In step S6.1, the film-forming agent is nitrile rubber modified epoxy resin.

10. The preparation method of a high-temperature resistant battery separator according to claim 7, characterized in that, In step S6.1, the film-forming agent is carboxyl-terminated nitrile rubber modified epoxy resin.

11. A high-temperature resistant battery separator, characterized in that, It is prepared by the preparation method of a high-temperature resistant battery separator described in any one of claims 1 - 10.

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