Metal organic framework composite separator coating material, battery separator, and method of making

Abstract

This invention belongs to the field of battery separator technology, specifically relating to metal-organic framework (MOF) composite separator coating materials, battery separators, and their preparation methods. The MOF composite separator coating uses a dual-ligand aluminum-based MOF composite material as the matrix, embedding deprotonated ethylenediaminetetraacetic acid (EDTA) coordination groups. The dual-ligand aluminum-based MOF composite material possesses at least a MIL-53-FA phase and a CAU-10-H phase. This invention utilizes the MIL-53-FA and CAU-10-H phases within the dual-ligand aluminum-based MOF embedded EDTA functional coating to provide porous transport channels and abundant framework sites, while EDTA provides multidentate coordination sites. This maintains the separator's good wettability to the electrolyte and ion transport channels, while also enhancing its binding capacity for dissolved metal ions, thereby reducing the migration and deposition of transition metal ions inside the battery, contributing to improved battery cycle life and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of battery separator technology, specifically relating to metal-organic framework composite separator coating materials, battery separators, and preparation methods. Background Technology

[0002] As power lithium-ion batteries develop towards higher energy density, higher safety, and longer cycle life, the shortcomings of traditional polyolefin separators in terms of thermal stability, electrolyte wettability, and interface control capabilities are becoming increasingly apparent, making it difficult to fully meet the application requirements of next-generation power battery systems. Especially under high voltage, high rate, and long-term cycling conditions, conventional separators are prone to problems such as thermal shrinkage, interface instability, and exacerbated side reactions, thereby affecting battery safety and service stability.

[0003] Meanwhile, lithium-rich manganese-based cathode materials have attracted widespread attention due to their high theoretical specific capacity. However, during cycling, they are susceptible to the Jahn-Teller effect, lattice structure evolution, and electrolyte erosion, leading to the dissolution of transition metal ions. These dissolved metal ions migrate within the battery, further disrupting interfacial stability, inducing side reactions, and accelerating electrochemical performance degradation, becoming a significant factor limiting the practical application of such materials. Therefore, effectively capturing and confining dissolved transition metal ions without significantly sacrificing ion transport performance is a key technical problem urgently needing to be solved in this field.

[0004] Inorganic ceramic-coated separators typically use polyethylene microporous membranes as the base membrane, with inorganic ceramic particles, usually alumina, boehmite, or silica, loaded onto one or both sides. A polymer binder and dispersant are added to form a stable slurry, which is then coated and dried to obtain the finished separator. The thermal shrinkage behavior and electrolyte wetting ability of the separator are mainly improved through the thermal stability and surface polarity of the inorganic particles. While this can improve the thermal stability of the separator to some extent, it usually suffers from high material density, difficulty in processing and dispersion, insufficient coating flexibility, and is detrimental to the development of lightweight and high-energy-density batteries. In contrast, metal-organic framework materials have advantages such as tunable pore structure, large specific surface area, and designable functional sites.

[0005] Currently, metal-organic framework materials typically select a single MOF material with a porous structure as the functional filler, such as MIL-53 type metal-organic framework powder, and mix it with binders, dispersants and organic solvents to form a slurry. This slurry is then coated onto the surface of a polyethylene diaphragm by spin coating, blade coating or other methods to obtain a MOF-coated diaphragm. However, the diaphragm coating system formed by a single MOF material still has problems such as insufficient pore matching, poor interface stability and limited ability to capture dissolved transition metal ions, making it difficult to simultaneously meet the comprehensive requirements of long cycling, fast ion transport and interface stability. Summary of the Invention

[0006] The purpose of this invention is to provide a metal-organic framework composite separator coating material, a battery separator, and a preparation method thereof. Utilizing a dual-ligand aluminum-based metal-organic framework embedded with ethylenediaminetetraacetic acid (EDTA) in its functional coating, the MIL-53-FA and CAU-10-H phases provide porous transport channels and abundant framework sites, while EDTA provides multidentate coordination sites. This maintains the separator's good wettability to the electrolyte and provides ion transport channels, while also enhancing its binding capacity for dissolved metal ions. It can selectively identify, capture, and confine transition metal ions such as manganese, iron, nickel, cobalt, and vanadium in the electrolyte, thereby reducing the migration and deposition of these transition metal ions inside the battery, contributing to improved battery cycle life and rate performance.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0008] The first objective of this invention is to provide a metal-organic framework composite membrane coating material, wherein the metal-organic framework composite membrane coating uses a dual-ligand aluminum-based metal-organic framework composite material as the matrix and embeds a deprotonated ethylenediaminetetraacetic acid coordinating group, and the dual-ligand aluminum-based metal-organic framework composite material has at least a MIL-53-FA phase and a CAU-10-H phase.

[0009] A second objective of this invention is to provide a method for preparing the above-mentioned metal-organic framework composite membrane coating material, comprising the following steps: A calcium sodium edetate solution was added to a dual-ligand aluminum-based metal-organic framework composite material. The mixture was stirred to allow the edetate ions to enter the pores and / or defect sites of the metal-organic framework composite material. The mixture was then reacted under sealed conditions at 60℃~80℃ to allow the edetate ions to bind to the active sites inside the framework. The resulting metal-organic framework composite membrane coating material was obtained by filtration.

[0010] Furthermore, the solid-liquid ratio of the dual-ligand aluminum-based metal-organic framework composite material and the sodium calcium edetate solution is 1g:5mL~100mL, the concentration of the sodium calcium edetate solution is 0.01mol / L~1mol / L, the stirring time is 0.5h~12h, and the reaction time is 6h~12h.

[0011] Furthermore, the preparation method of the dual-ligand aluminum-based metal-organic framework composite material includes the following steps: Using aluminum salts of trivalent aluminum ions, trans-butenedioic acid, and isophthalic acid as raw materials, they are dissolved in a mixed solvent, and the pH of the system is adjusted to 4-10 by alkali. The reaction is carried out at 130℃-150℃, cooled to room temperature, and filtered to obtain a dual-ligand aluminum-based metal-organic framework composite material.

[0012] Furthermore, the total molar ratio of trans-butenedioic acid and isophthalic acid to the aluminum ions in the aluminum salt is 0.5–4:1, the molar ratio of trans-butenedioic acid to isophthalic acid is 1–4:1–4, and the solvothermal reaction time is 12–24 h.

[0013] A third objective of this invention is to provide a battery separator, comprising a base film and a functional coating disposed on at least one side of the base film, wherein the functional coating is the aforementioned metal-organic framework composite separator coating material.

[0014] A fourth objective of this invention is to provide a method for preparing the aforementioned battery separator, comprising the following steps: A binder, dispersant, solvent, and surfactant are added sequentially to a metal-organic framework composite separator coating material and dispersed and mixed to obtain a slurry. The slurry is then coated onto the surface of a base membrane and dried to obtain a battery separator.

[0015] Furthermore, the solid content of the slurry is 5wt% to 30wt%, and based on the mass of the metal-organic framework composite membrane coating material, the amount of the binder added is 2wt% to 20wt%, the amount of the dispersant added is 0.1wt% to 10wt%, and the amount of the surfactant added is 0.01wt% to 2wt%.

[0016] Furthermore, the thickness of the dried single-sided coating is 2μm to 12μm, and the areal density is 0.1mg / cm³. 2 ~2.0mg / cm 2 .

[0017] Furthermore, the binder is selected from at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinylpyrrolidone, polyimide, polyetherimide, and combinations thereof; the dispersant is selected from at least one of polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol block polymers; the surfactant is selected from at least one of silane coupling agents, fluorinated surfactants, nonionic surfactants, and combinations thereof; and the membrane is selected from polyethylene membranes, polypropylene membranes, polypropylene / polyethylene / polypropylene three-layer composite membranes, or other porous polyolefin membranes.

[0018] Compared with the prior art, the present invention has the following advantages: The metal-organic framework composite membrane coating material provided by this invention is based on a synergistic mechanism of "in-situ anchoring, coordination recognition, ion exchange, pore adsorption, and inhibition of re-dissolution." In the dual-ligand aluminum-based metal-organic framework embedded ethylenediaminetetraacetic acid (EDTA) composite membrane coating material, the MIL-53-FA phase and CAU-10-H phase provide porous transport channels and abundant framework sites, while EDTA provides multidentate coordination sites. This not only maintains the membrane's good wetting ability and ion transport channels for the electrolyte but also enhances its binding ability to dissolved metal ions. It can selectively recognize, capture, and confine transition metal ions such as manganese, iron, nickel, cobalt, and vanadium in the electrolyte, thereby reducing the migration and deposition of these transition metal ions inside the battery and the side reactions they cause. This helps to improve battery cycle life and rate performance.

[0019] The battery separator provided by this invention, when transition metal ions dissolve from the positive electrode side during battery charging and discharging, migrate to the separator region driven by the concentration gradient. These ions preferentially coordinate with oxygen-containing coordination sites and ethylenediaminetetraacetic acid groups in the coating, maintaining good wetting ability and ion transport channels for the separator while enhancing its binding ability to dissolved metal ions. This approach effectively balances electrochemical performance and interfacial stability. Compared to uncoated separators, the loaded separator exhibits better thermal dimensional stability and interfacial wettability, helping to suppress side reactions under high-temperature or high-rate conditions, thus improving battery safety and stability.

[0020] The preparation method provided by this invention has a relatively simple process flow, a wide range of raw material sources, and facilitates the controllable preparation of structure and properties by adjusting the ligand ratio, reaction temperature, solvent composition and post-treatment conditions, thus having good potential for process scale-up. Attached Figure Description

[0021] Figure 1 The images show the surface morphology of the battery separators prepared in Example 1 and Comparative Examples 1 to 2 of this invention. Figure 1 In the figures, a represents Comparative Example 1, b represents Comparative Example 2, c represents Comparative Example 3, and d represents Example 1.

[0022] Figure 2 The following are nitrogen adsorption-desorption isotherms of the battery separators prepared in Example 1 and Comparative Examples 1 to 2 of this invention. Figure 2 In the figures, a represents Comparative Example 1, b represents Comparative Example 2, and c represents Example 1.

[0023] Figure 3 The images show inductively coupled mass spectra of the battery separators prepared in Example 1 and Comparative Examples 1 to 5 of this invention for capturing transition metal ions.

[0024] Figure 4 The graphs show a comparison of the battery cycle performance of the battery separators prepared in Example 1 and Comparative Examples 1 to 5 of this invention.

[0025] Figure 5 This is a comparison chart of the battery rate performance of the battery separators prepared in Example 1 and Comparative Examples 1 to 5 of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0028] The purpose of this invention is to provide a metal-organic framework composite membrane coating material, wherein the metal-organic framework composite membrane coating uses a dual-ligand aluminum-based metal-organic framework composite material as the matrix and embeds a deprotonated ethylenediaminetetraacetic acid coordinating group, and the dual-ligand aluminum-based metal-organic framework composite material has at least a MIL-53-FA phase and a CAU-10-H phase.

[0029] Based on a synergistic mechanism of "in-situ anchoring, coordination recognition, ion exchange, pore adsorption, and inhibition of re-dissolution," the MIL-53-FA and CAU-10-H phases in the ethylenediaminetetraacetic acid (EDTA) composite separator coating material embedded in a dual-ligand aluminum-based metal-organic framework provide porous transport channels and abundant framework sites, while EDTA provides multidentate coordination sites. This maintains the separator's good wettability to the electrolyte and ion transport channels, while enhancing its binding capacity for dissolved metal ions. It can selectively recognize, capture, and confine transition metal ions such as manganese, iron, nickel, cobalt, and vanadium in the electrolyte, thereby reducing the migration and deposition of these transition metal ions within the battery and the side reactions they induce, contributing to improved battery cycle life and rate performance. In this process, the functional coating achieves effective regulation of transition metal ions through the following synergistic mechanism:

[0030] Firstly, there is the in-situ anchoring effect. After transition metal ions enter the coating, they can be rapidly captured by the active sites and ethylenediaminetetraacetic acid groups inside the pores, reducing the possibility of them continuing to migrate to the negative electrode.

[0031] Secondly, dynamic coordination response. Transition metal ions with different valence states and radii can form coordination structures with varying degrees of stability with the functional sites, enabling the functional coating to exhibit a broad-spectrum capture ability for a variety of transition metal ions.

[0032] Thirdly, ion exchange and confined adsorption. The porous framework structure provides channels and space for ion diffusion and temporary storage, while the ethylenediaminetetraacetic acid groups further enhance the binding strength to metal ions, thereby improving the overall adsorption efficiency.

[0033] Fourth, it inhibits re-dissolution. The captured transition metal ions form a relatively stable confined coordination structure under the combined action of the porous framework and the multidentate ligands, which can reduce their tendency to re-enter the electrolyte.

[0034] Based on the above mechanism, the functional coating helps to reduce the deposition of dissolved metals on the negative electrode surface and the side reactions they induce, thereby improving the cycle stability, rate performance and interface stability of the battery.

[0035] In addition, the present invention also provides a method for preparing the above-mentioned metal-organic framework composite membrane coating material, comprising the following steps: A calcium sodium edetate solution was added to a dual-ligand aluminum-based metal-organic framework composite material. The mixture was stirred to allow the edetate ions to enter the pores and / or defect sites of the metal-organic framework composite material. The mixture was then reacted under sealed conditions at 60℃~80℃ to allow the edetate ions to bind to the active sites inside the framework. The resulting metal-organic framework composite membrane coating material was obtained by filtration.

[0036] In some embodiments, the solid-liquid ratio of the dual-ligand aluminum-based metal-organic framework composite material and the sodium calcium edetate solution is 1g:5mL to 100mL, preferably 1g:10mL to 50mL; the sodium calcium edetate solution is an aqueous solution with a concentration of 0.01mol / L to 1mol / L, preferably 0.05mol / L to 0.5mol / L, wherein the sodium calcium edetate is a sodium calcium edetate raw material, analytical grade reagent, chemically pure reagent, or other sodium calcium edetate raw material that does not contain excipients that affect the reaction. To avoid the excipients from the formulation interfering with the pore space and subsequent coating performance, it is preferable to use a solution prepared from a solid powder raw material; the stirring time is 0.5h to 12h, preferably 1h to 6h, to ensure sufficient contact between the edetate ions and the framework material, allowing the edetate ions to enter the pores and / or defect sites of the metal-organic framework composite material.

[0037] In some embodiments, the sealed reaction is carried out in a closed reaction vessel for 6 to 12 hours to allow the edetate anion to bind to the active sites inside the framework. The closed reaction vessel can be a reaction vessel with a polytetrafluoroethylene liner, a closed glass reaction bottle, or other reaction device that can maintain a stable temperature and a closed environment. Preferably, the reaction temperature is 65°C to 75°C and the holding time is 6 to 8 hours.

[0038] In some embodiments, the filtrate needs to be washed and dried. Washing is performed using deionized water, alcohol solvents, or a mixture thereof. The washing endpoint is determined by the absence of obvious free edetate residue in the filtrate. Drying is performed under vacuum at 40°C to 100°C for 2 to 24 hours to achieve constant weight.

[0039] In some embodiments, a method for preparing a dual-ligand aluminum-based metal-organic framework composite material includes the following steps: Using aluminum salts of trivalent aluminum ions, trans-butenedioic acid, and isophthalic acid as raw materials, they are dissolved in a mixed solvent, and the pH of the system is adjusted to 4-10 by alkali. The reaction is carried out at 130℃-150℃ for 12-24 hours, cooled to room temperature, and filtered to obtain a dual-ligand aluminum-based metal-organic framework composite material.

[0040] In some embodiments, the molar ratio of the total molar amount of trans-butenedioic acid and isophthalic acid to the molar ratio of aluminum ions in the aluminum salt is 0.5 to 4:1, preferably 0.5 to 4:1. The aluminum salt is a compound containing trivalent aluminum ions, selected from one or more of anhydrous aluminum sulfate, aluminum sulfate octadecadehydrate, anhydrous aluminum chloride, aluminum chloride hexahydrate, anhydrous aluminum nitrate, aluminum nitrate nonahydrate, anhydrous aluminum perchlorate, and combinations thereof.

[0041] In some embodiments, trans-butenedioic acid and isophthalic acid are used as organic ligands to construct the framework. By adjusting the ratio of the two organic ligands, the formation ratio of the MIL-53-FA phase and the CAU-10-H phase can be adjusted. The molar ratio of trans-butenedioic acid to isophthalic acid is 1-4:1-4. Preferably, the molar ratio of trans-butenedioic acid to isophthalic acid is 1-2:1-2.

[0042] In some embodiments, the base is an alkaline reagent used to adjust the pH of the reaction system and promote the deprotonation of ligands. It is selected from one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, ammonia, and combinations thereof. The pH of the reaction system is adjusted to 4 to 10, preferably 5 to 8, to balance the coordination reaction of metal ions and the nucleation and growth process of crystals.

[0043] In some embodiments, the mixed solvent is formed from N,N-dimethylformamide and water, with a volume ratio of N,N-dimethylformamide to water of 1–10:1–10, preferably 1–5:1–5. By adjusting the ratio of the organic solvent to water, the crystal nucleation rate, grain size, and multiphase structure ratio can be controlled.

[0044] In some embodiments, the solvothermal reaction temperature is preferably 135℃~145℃, and the time is 16h~20h. The cooling method includes natural cooling, room temperature water cooling, ice-water bath cooling, dry ice-assisted cooling, or liquid nitrogen-assisted cooling. Rapid cooling is preferred, provided the container is safe, to facilitate the fixation of the product's phase structure and pore characteristics. After cooling to room temperature, the product is filtered, washed, and dried. Filtration is performed using vacuum filtration to separate the solid product from the mother liquor. The solid product is washed 2 to 6 times with one or more of N,N-dimethylformamide, ethanol, methanol, and deionized water to remove unreacted raw materials and residual solvent in the pores. The washed solid is placed in a vacuum drying oven and dried at 40℃~120℃ for 1h~24h, preferably to constant weight, to obtain the dual-ligand aluminum-based metal-organic framework composite powder. The powder is a white or off-white blocky, granular, or powdery solid, and its morphology and particle size can be controlled by adjusting the ligand ratio, solvent ratio, reaction temperature, and cooling rate.

[0045] This invention also provides a battery separator, comprising a base membrane and a functional coating disposed on at least one surface of the base membrane, wherein the functional coating is the aforementioned metal-organic framework composite separator coating material. The base membrane is a commercially available battery separator, selected from polyethylene separators, polypropylene separators, polypropylene / polyethylene / polypropylene three-layer composite separators, or other porous polyolefin separators. The battery separator can be a base membrane / coating double-layer structure, a base membrane / coating / base membrane sandwich composite structure, or a coating / base membrane / coating double-sided coated structure, etc.

[0046] In battery manufacturing, when transition metal ions dissolve from the positive electrode during charging and discharging, these ions migrate to the separator region driven by a concentration gradient. They preferentially coordinate with oxygen-containing coordination sites and ethylenediaminetetraacetic acid (EDTA) groups in the coating. This maintains the separator's good wettability to the electrolyte and provides ion transport channels, while also enhancing its binding capacity for dissolved metal ions, thus balancing electrochemical performance and interfacial stability. Compared to uncoated separators, loaded separators exhibit better thermal dimensional stability and interfacial wettability, helping to suppress side reactions and improve battery safety and stability under high-temperature or high-rate operating conditions.

[0047] The present invention also provides a method for preparing the above-mentioned battery separator, comprising the following steps: A binder, dispersant, solvent, and surfactant are added sequentially to a metal-organic framework composite separator coating material and dispersed and mixed to obtain a slurry. The slurry is then coated onto the surface of a base membrane and dried to obtain a battery separator.

[0048] In some embodiments, the binder is selected from at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinylpyrrolidone, polyimide, polyetherimide, and combinations thereof; the dispersant is selected from at least one of polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol block polymers; and the surfactant is selected from at least one of silane coupling agents, fluorinated surfactants, nonionic surfactants, and combinations thereof.

[0049] In some embodiments, the solid content of the slurry is 5wt% to 30wt%, preferably 10wt% to 20wt%. Based on the mass of the metal-organic framework composite membrane coating material, the amount of binder added is 2wt% to 20wt%, the amount of dispersant added is 0.1wt% to 10wt%, the amount of surfactant added is 0.01wt% to 2wt%, and the balance is solvent.

[0050] In some embodiments, the dispersion and mixing can be carried out by mechanical stirring, ultrasonic dispersion, ball milling dispersion, or a combination thereof, to obtain a uniform, stable coating slurry without obvious agglomeration.

[0051] In some embodiments, the coating method includes blade coating, spin coating, dip coating, slot coating, or transfer coating. Coating is performed on one or both sides of the base film. The thickness of the single-sided coating after drying is 2 μm to 12 μm, preferably 3 μm to 8 μm, with an areal density of 0.1 mg / cm³. 2 ~2.0mg / cm 2 Preferably, the areal density is 0.2 mg / cm³. 2 ~1.0mg / cm 2 While satisfying thermal stability and mechanical integrity requirements, the coating system of this invention is expected to reduce the mass burden per unit area compared to high-density inorganic ceramic filler systems, thereby providing favorable conditions for improving the specific energy of devices.

[0052] In some embodiments, the drying temperature after coating is 40℃~120℃ and the drying time is 5min~24h. The specific temperature can be adjusted according to the type of solvent, coating thickness and heat resistance of the base film, so that the battery separator has good coating adhesion, wettability and thermal dimensional stability while ensuring ion transport performance.

[0053] The preparation method provided by this invention has a relatively simple process flow, a wide range of raw material sources, and facilitates the controllable preparation of structure and properties by adjusting the ligand ratio, reaction temperature, solvent composition and post-treatment conditions, thus having good potential for process scale-up.

[0054] It is understood that the metal-organic framework composite membrane coating material provided by the present invention can be applied not only to battery separators, but also to heavy metal ion adsorption, liquid phase separation, water treatment, environmental remediation and other fields involving metal ion capture and confinement, and has good application extensibility.

[0055] The following specific examples will provide further explanation.

[0056] Example 1 A battery separator includes a polyethylene base membrane and a metal-organic framework composite separator coating material disposed on one surface of the polyethylene base membrane.

[0057] The method for preparing a battery separator includes the following steps: Step 1, Preparation of dual-ligand aluminum-based metal-organic framework composites: Step 1.1: Prepare a water / N,N-dimethylformamide mixed solvent, wherein the volume ratio of water to N,N-dimethylformamide is 1:4. Add trans-butenedioic acid and isophthalic acid to the mixed solvent and stir until fully dissolved, wherein the molar ratio of trans-butenedioic acid to isophthalic acid is 2:1; then add 28.0 mmol of aluminum sulfate octadecylhydrate and stir vigorously until fully dissolved. Prepare a sodium hydroxide solution by adding 30.5 mmol of sodium hydroxide to 50 mL of water and stirring until fully dissolved.

[0058] Step 1.2: After all components have completely dissolved, sodium hydroxide solution is slowly added dropwise to the mixture using a peristaltic pump, while vigorous stirring to form a homogeneous reaction solution. The resulting mixture is then transferred to a polytetrafluoroethylene-lined reactor, sealed, and placed at 135°C for 12 hours.

[0059] Step 1.3: After the reaction is complete, the mixture is naturally cooled to room temperature to obtain a white suspension. The suspension is collected and washed three times each with deionized water and N,N-dimethylformamide, and finally dried under vacuum at 120°C for 6 hours to obtain a dual-ligand aluminum-based metal-organic framework composite powder.

[0060] Step 2, Preparation of ethylenediaminetetraacetic acid powder embedded in a dual-ligand aluminum-based metal-organic framework: 10 mmol of calcium sodium edetate was added to 1 mL of deionized water and stirred to form a homogeneous system. Then, 1.2 g of the previously obtained dual-ligand aluminum-based metal-organic framework powder was added and ultrasonically dispersed to form a homogeneous suspension. The resulting suspension was continuously stirred at 60 °C for 24 h. After the reaction was complete, the resulting white product was collected by centrifugation, washed three times with deionized water, and then vacuum dried at 60 °C for 12 h to obtain a dual-ligand aluminum-based metal-organic framework powder embedded with ethylenediaminetetraacetic acid.

[0061] Step 3: Preparation of a polyethylene diaphragm coated with ethylenediaminetetraacetic acid (EDTA) embedded in a dual-ligand aluminum-based metal-organic framework. Step 3.1: Take 0.5g of ethylenediaminetetraacetic acid powder embedded in a dual-ligand aluminum-based metal-organic framework and add it to polyvinylidene fluoride binder, Pluronic F-127 dispersant, nonionic surfactant Span-80 and N-methylpyrrolidone (wherein, based on the mass of the functional powder embedded in the dual-ligand aluminum-based metal-organic framework, the amount of polyvinylidene fluoride added is 5wt%, the amount of Pluronic F-127 added is 0.1wt%, the amount of Span-80 added is 0.1wt%, and the balance is N-methylpyrrolidone solvent), and continue stirring for 12h to obtain a uniformly dispersed coating slurry.

[0062] Step 3.2: Cut and fix the commercially available polyethylene single-layer separator onto a spin-coating machine. First, apply the coating slurry to the separator surface at 50 rpm, then increase the speed to 300 rpm for spin-coating. After spin-coating, remove the coated separator and vacuum dry it at 60°C for 6 hours to obtain a dual-ligand aluminum-based metal-organic framework coated polyethylene separator with a thickness of 29 μm and an area loading of 0.66 mg / cm². 2 The separator was then punched into round pieces with a diameter of 19mm to obtain the battery separator, named MOF-E / PE-1.

[0063] Example 2 A battery separator includes a polyethylene base membrane and a metal-organic framework composite separator coating material disposed on one surface of the polyethylene base membrane.

[0064] The method for preparing a battery separator includes the following steps: Step 1, Preparation of dual-ligand aluminum-based metal-organic framework composites: Step 1.1: Prepare a water / N,N-dimethylformamide mixed solvent, wherein the volume ratio of water to N,N-dimethylformamide is 1:4. Add trans-butenedioic acid and isophthalic acid to the mixed solvent and stir until fully dissolved, wherein the molar ratio of trans-butenedioic acid to isophthalic acid is 1:1; then add 28.0 mmol of aluminum sulfate octadecylhydrate and stir vigorously until fully dissolved. Prepare a sodium hydroxide solution by adding 30.5 mmol of sodium hydroxide to 50 mL of water and stirring until fully dissolved.

[0065] Step 1.2: After all components have completely dissolved, sodium hydroxide solution is slowly added dropwise to the mixture using a peristaltic pump, while vigorous stirring to form a homogeneous reaction solution. The resulting mixture is then transferred to a polytetrafluoroethylene-lined reactor, sealed, and placed at 135°C for 12 hours.

[0066] Step 1.3: After the reaction is complete, the mixture is naturally cooled to room temperature to obtain a white suspension. The suspension is collected and washed three times each with deionized water and N,N-dimethylformamide, and finally dried under vacuum at 120°C for 6 hours to obtain a dual-ligand aluminum-based metal-organic framework composite powder.

[0067] Step 2, Preparation of ethylenediaminetetraacetic acid powder embedded in a dual-ligand aluminum-based metal-organic framework: 10 mmol of calcium sodium edetate was added to 1 mL of deionized water and stirred to form a homogeneous system. Then, 1.2 g of the previously obtained dual-ligand aluminum-based metal-organic framework powder was added and ultrasonically dispersed to form a homogeneous suspension. The resulting suspension was continuously stirred at 60 °C for 24 h. After the reaction was complete, the resulting white product was collected by centrifugation, washed three times with deionized water, and then vacuum dried at 60 °C for 12 h to obtain a dual-ligand aluminum-based metal-organic framework powder embedded with ethylenediaminetetraacetic acid.

[0068] Step 3: Preparation of a polyethylene diaphragm coated with ethylenediaminetetraacetic acid (EDTA) embedded in a dual-ligand aluminum-based metal-organic framework. Step 3.1: Take 0.5g of ethylenediaminetetraacetic acid powder embedded in a dual-ligand aluminum-based metal-organic framework and add it to polyvinylidene fluoride binder, Pluronic F-127 dispersant, nonionic surfactant Span-80 and N-methylpyrrolidone (wherein, based on the mass of the functional powder embedded in the dual-ligand aluminum-based metal-organic framework, the amount of polyvinylidene fluoride added is 5wt%, the amount of Pluronic F-127 added is 0.1wt%, the amount of Span-80 added is 0.1wt%, and the balance is N-methylpyrrolidone solvent), and continue stirring for 12h to obtain a uniformly dispersed coating slurry.

[0069] Step 3.2: Cut and fix the commercially available polyethylene single-layer separator onto a spin-coating machine. First, apply the coating slurry to the separator surface at 50 rpm, then increase the speed to 300 rpm for spin-coating. After spin-coating, remove the coated separator and vacuum dry it at 60°C for 6 hours to obtain a dual-ligand aluminum-based metal-organic framework coated polyethylene separator with a thickness of 29 μm and an area loading of 0.68 mg / cm². 2 The separator was then punched into round pieces with a diameter of 19mm to obtain the battery separator, named MOF-E / PE-2.

[0070] Example 3 A battery separator includes a polyethylene base membrane and a metal-organic framework composite separator coating material disposed on one surface of the polyethylene base membrane.

[0071] The method for preparing a battery separator includes the following steps: Step 1, Preparation of dual-ligand aluminum-based metal-organic framework composites: Step 1.1: Prepare a water / N,N-dimethylformamide mixed solvent, wherein the volume ratio of water to N,N-dimethylformamide is 1:4. Add trans-butenedioic acid and isophthalic acid to the mixed solvent and stir until fully dissolved, wherein the molar ratio of trans-butenedioic acid to isophthalic acid is 1:2; then add 28.0 mmol of aluminum sulfate octadecylhydrate and stir vigorously until fully dissolved. Prepare a sodium hydroxide solution by adding 30.5 mmol of sodium hydroxide to 50 mL of water and stirring until fully dissolved.

[0072] Step 1.2: After all components have completely dissolved, sodium hydroxide solution is slowly added dropwise to the mixture using a peristaltic pump, while vigorous stirring to form a homogeneous reaction solution. The resulting mixture is then transferred to a polytetrafluoroethylene-lined reactor, sealed, and placed at 135°C for 12 hours.

[0073] Step 1.3: After the reaction is complete, the mixture is naturally cooled to room temperature to obtain a white suspension. The suspension is collected and washed three times with deionized water and N,N-dimethylformamide, respectively. Finally, it is vacuum dried at 120°C for 6 hours to obtain a dual-ligand aluminum-based metal-organic framework composite powder.

[0074] Step 2, Preparation of ethylenediaminetetraacetic acid powder embedded in a dual-ligand aluminum-based metal-organic framework: 10 mmol of calcium sodium edetate was added to 1 mL of deionized water and stirred to form a homogeneous system. Then, 1.2 g of the previously obtained dual-ligand aluminum-based metal-organic framework powder was added and ultrasonically dispersed to form a homogeneous suspension. The resulting suspension was continuously stirred at 60 °C for 24 h. After the reaction was complete, the resulting white product was collected by centrifugation, washed three times with deionized water, and then vacuum dried at 60 °C for 12 h to obtain a dual-ligand aluminum-based metal-organic framework powder embedded with ethylenediaminetetraacetic acid.

[0075] Step 3: Preparation of a polyethylene diaphragm coated with ethylenediaminetetraacetic acid (EDTA) embedded in a dual-ligand aluminum-based metal-organic framework. Step 3.1: Take 0.5g of ethylenediaminetetraacetic acid powder embedded in a dual-ligand aluminum-based metal-organic framework and add it to polyvinylidene fluoride binder, Pluronic F-127 dispersant, nonionic surfactant Span-80 and N-methylpyrrolidone (wherein, based on the mass of the functional powder embedded in the dual-ligand aluminum-based metal-organic framework, the amount of polyvinylidene fluoride added is 5wt%, the amount of Pluronic F-127 added is 0.1wt%, the amount of Span-80 added is 0.1wt%, and the balance is N-methylpyrrolidone solvent), and continue stirring for 12h to obtain a uniformly dispersed coating slurry.

[0076] Step 3.2: Cut and fix the commercially available polyethylene single-layer separator onto a spin-coating machine. First, apply the coating slurry to the separator surface at 50 rpm, then increase the speed to 300 rpm for spin-coating. After spin-coating, remove the coated separator and vacuum dry it at 60°C for 6 hours to obtain a dual-ligand aluminum-based metal-organic framework coated polyethylene separator with a thickness of 29 μm and an area loading of 0.69 mg / cm². 2 The separator was then punched into round pieces with a diameter of 19mm to obtain the battery separator, named MOF-E / PE-3.

[0077] Comparative Example 1 A battery separator differs from Example 1 in that the metal-organic framework composite separator coating material is a dual-ligand aluminum-based metal-organic framework composite powder.

[0078] The method for preparing a battery separator includes the following steps: Step 1, Preparation of dual-ligand aluminum-based metal-organic framework composites: Step 1.1: Prepare a water / N,N-dimethylformamide mixed solvent, wherein the volume ratio of water to N,N-dimethylformamide is 1:4. Add trans-butenedioic acid and isophthalic acid to the mixed solvent and stir until fully dissolved, wherein the molar ratio of trans-butenedioic acid to isophthalic acid is 2:1; then add 28.0 mmol of aluminum sulfate octadecylhydrate and stir vigorously until fully dissolved. Prepare a sodium hydroxide solution by adding 30.5 mmol of sodium hydroxide to 50 mL of water and stirring until fully dissolved.

[0079] Step 1.2: After all components have completely dissolved, sodium hydroxide solution is slowly added dropwise to the mixture using a peristaltic pump, while vigorous stirring to form a homogeneous reaction solution. The resulting mixture is then transferred to a polytetrafluoroethylene-lined reactor, sealed, and placed at 135°C for 12 hours.

[0080] Step 1.3: After the reaction is complete, the mixture is naturally cooled to room temperature to obtain a white suspension. The suspension is collected and washed three times each with deionized water and N,N-dimethylformamide, and finally dried under vacuum at 120°C for 6 hours to obtain a dual-ligand aluminum-based metal-organic framework composite powder.

[0081] Step 2, Preparation of a polyethylene membrane coated with a dual-ligand aluminum-based metal-organic framework: Step 2.1: Take 0.5g of dual-ligand aluminum-based metal-organic framework powder and add polyvinylidene fluoride binder, Pluronic F-127 dispersant, nonionic surfactant Span-80 and N-methylpyrrolidone (wherein, based on the mass of the ethylenediaminetetraacetic acid functional powder embedded in the dual-ligand aluminum-based metal-organic framework, the amount of polyvinylidene fluoride added is 5wt%, the amount of Pluronic F-127 added is 0.1wt%, the amount of Span-80 added is 0.1wt%, and the balance is N-methylpyrrolidone solvent), and continue stirring for 12h to obtain a uniformly dispersed coating slurry.

[0082] Step 2.2: The commercially available polyethylene single-layer separator was cut and fixed onto a spin-coating machine. First, the coating slurry was added to the separator surface at 50 rpm, then the spin-coating speed was increased to 300 rpm. After spin-coating, the resulting coated separator was removed and vacuum-dried at 60°C for 6 hours to obtain a polyethylene separator coated with a dual-ligand aluminum-based metal-organic framework, with a thickness of 29 μm and an area loading of 0.66 mg / cm². 2 The separator is then punched into round pieces with a diameter of 19mm to obtain the battery separator, named MOF / PE.

[0083] Comparative Example 2 A battery separator differs from Example 1 in that the metal-organic framework composite separator coating material is a mixture of ethylenediaminetetraacetic acid powder and a dual-ligand aluminum-based metal-organic framework composite material.

[0084] The method for preparing a battery separator includes the following steps: Step 1, Preparation of dual-ligand aluminum-based metal-organic framework composites: Step 1.1: Prepare a water / N,N-dimethylformamide mixed solvent, wherein the volume ratio of water to N,N-dimethylformamide is 1:4. Add trans-butenedioic acid and isophthalic acid to the mixed solvent and stir until fully dissolved, wherein the molar ratio of trans-butenedioic acid to isophthalic acid is 2:1; then add 28.0 mmol of aluminum sulfate octadecylhydrate and stir vigorously until fully dissolved. Prepare a sodium hydroxide solution by adding 30.5 mmol of sodium hydroxide to 50 mL of water and stirring until fully dissolved.

[0085] Step 1.2: After all components have completely dissolved, sodium hydroxide solution is slowly added dropwise to the mixture using a peristaltic pump, while vigorous stirring to form a homogeneous reaction solution. The resulting mixture is then transferred to a polytetrafluoroethylene-lined reactor, sealed, and placed at 135°C for 12 hours.

[0086] Step 1.3: After the reaction is complete, the mixture is naturally cooled to room temperature to obtain a white suspension. The suspension is collected and washed three times each with deionized water and N,N-dimethylformamide, and finally dried under vacuum at 120°C for 6 hours to obtain a dual-ligand aluminum-based metal-organic framework composite powder.

[0087] Step 2, Preparation of dual-ligand aluminum-based metal-organic framework mixed ethylenediaminetetraacetic acid powder: 10 mmol of ethylenediaminetetraacetic acid powder and 1.2 g of dual-ligand aluminum-based metal-organic framework powder were thoroughly ground and mixed in a grinder for 24 h. After mixing, the resulting white product was washed with deionized water at least 3 times and then dried under vacuum at 60 °C for 12 h to obtain a mixed ethylenediaminetetraacetic acid powder with dual-ligand aluminum-based metal-organic framework.

[0088] Step 3, Preparation of a polyethylene membrane supported on a dual-ligand aluminum-based metal-organic framework mixed with ethylenediaminetetraacetic acid: Step 3.1: Take 0.5g of the ethylenediaminetetraacetic acid (EDTA) powder mixed with the dual-ligand aluminum-based metal-organic framework and add it to the polyvinylidene fluoride (PVDF) binder, Pluronic F-127 dispersant, nonionic surfactant Span-80, and N-methylpyrrolidone (based on the mass of the EDTA functional powder embedded in the dual-ligand aluminum-based metal-organic framework, the amount of PVDF added is 5wt%, the amount of Pluronic F-127 added is 0.1wt%, the amount of Span-80 added is 0.1wt%, and the balance is N-methylpyrrolidone solvent). Stir continuously for 12h to obtain a uniformly dispersed coating slurry.

[0089] Step 3.2: Cut and fix the commercially available polyethylene single-layer separator onto a spin-coating machine. First, apply the coating slurry to the separator surface at 50 rpm, then increase the speed to 300 rpm for spin-coating. After spin-coating, remove the coated separator and vacuum dry it at 60°C for 6 hours to obtain a polyethylene separator with a thickness of 29 μm and an areal loading of 0.66 mg / cm². 2 The separator is then punched into round pieces with a diameter of 19mm to obtain the battery separator, named MOF / PE.

[0090] Comparative Example 3 A battery separator differs from Example 1 in that: the battery separator uses a commercially available single-layer polyethylene separator, without any coating or modification treatment, and is used directly as a battery separator. The separator is punched into circular pieces with a diameter of 19 mm, denoted as PE.

[0091] Comparative Example 4 A battery separator, differing from Example 1 in that: the battery separator uses a commercially available ceramic-coated separator of the same thickness, which is used directly as a battery separator. The separator is punched into circular pieces with a diameter of 19 mm, denoted as C / PE.

[0092] Comparative Example 5 A battery separator, which differs from Example 1 in that it uses commercial metal-organic framework powder MIL-53.

[0093] The method for preparing the above-mentioned battery separator includes the following steps: Step 1: Take 0.5g of the bis-ligand aluminum-based metal-organic framework mixed ethylenediaminetetraacetic acid powder and add it to polyvinylidene fluoride binder, Pluronic F-127 dispersant, nonionic surfactant Span-80 and N-methylpyrrolidone (wherein, based on the mass of the ethylenediaminetetraacetic acid functional powder embedded in the bis-ligand aluminum-based metal-organic framework, the amount of polyvinylidene fluoride added is 5wt%, the amount of Pluronic F-127 added is 0.1wt%, the amount of Span-80 added is 0.1wt%, and the balance is N-methylpyrrolidone solvent), and continue stirring for 12h to obtain a uniformly dispersed coating slurry.

[0094] Step 2: Cut and fix the commercially available polyethylene single-layer separator onto a spin-coating machine. First, apply the coating slurry to the separator surface at 50 rpm, then increase the speed to 300 rpm for spin-coating. After spin-coating, remove the coated separator and vacuum dry it at 60°C for 6 hours to obtain an aluminum-based MIL-53 coated polyethylene separator with a thickness of 30 μm and a surface loading of 0.60 mg / cm². 2 The separator is then punched into round pieces with a diameter of 19mm to obtain the battery separator, named M / PE.

[0095] The battery separators prepared in Example 1 and Comparative Examples 1 to 3 were subjected to structural tests, and the results are shown below.

[0096] Figure 1 The images show the surface morphology of the battery separators prepared in Example 1 and Comparative Examples 1 to 3 of this invention. Figure 1 In the table, a represents Comparative Example 1, b represents Comparative Example 2, c represents Comparative Example 3, and d represents Example 1. Figure 1 As shown, dual MOF particles can be loaded onto the surface of a polyethylene membrane (MOF / PE) to form a granular coating with a certain degree of roughness, but the particle distribution still exhibits some degree of agglomeration. When dual MOF and EDTA (ethylenediaminetetraacetic acid) are coated using a simple mixing method (MOFE / PE), large-sized irregular blocky or sheet-like agglomerates appear on the membrane surface, resulting in poor surface uniformity. This indicates that the EDTA phase is not effectively embedded within the MOF structure, but rather exists partially as an independent phase in the coating. In contrast, the resulting dual MOF-embedded EDTA-coated membrane (MOF-E / PE) shows a more uniform particle distribution, better coating continuity, and a significant reduction in large agglomerates, forming a denser and more uniform porous particle coating layer. This indicates that EDTA has been effectively introduced into the MOF structure and has improved the coating's dispersibility and interfacial construction effect.

[0097] Figure 2 The following are nitrogen adsorption-desorption isotherms of the battery separators prepared in Example 1 and Comparative Examples 1 to 2 of this invention. Figure 2In the table, a represents Comparative Example 1, b represents Comparative Example 2, and c represents Example 1. Figure 2 As shown, all three samples exhibited adsorption growth in the low relative pressure region, indicating the presence of microporous structures. In the higher relative pressure region, they all showed significant increases in adsorption capacity and adsorption-desorption hysteresis, indicating the simultaneous presence of mesoporous or particle-structured pores, suggesting that the membrane coatings possess multi-level pore characteristics. Specifically, the double MOF-coated polyethylene membrane (MOF / PE) exhibited higher adsorption capacity and a significant hysteresis loop in the high-pressure region, indicating that the double MOF coating has a rich pore structure and a large total pore volume. The double MOF / EDTA mixed-coated polyethylene membrane (MOFE / PE) also showed high adsorption capacity, but its hysteresis characteristics were more pronounced. In contrast, the double MOF-embedded EDTA-coated polyethylene membrane (MOF-E / PE) showed a decrease in overall adsorption capacity, and a reduced surge and hysteresis in the high relative pressure region, indicating that the introduction of EDTA into the double MOF structure suppressed excessively large interparticle pores in the coating, resulting in a more uniform and rational pore structure.

[0098] The battery separators prepared in Example 1 and Comparative Examples 1 to 5 are used in lithium-rich manganese-based lithium batteries, including the following steps: S1. LiMnFePO4 powder, conductive agent Super-P, and polyvinylidene fluoride binder were added to N-methylpyrrolidone solvent at a mass ratio of 8:1:1, and stirred continuously for 12 hours. Subsequently, the slurry was uniformly coated onto the surface of an aluminum foil current collector with a thickness of 20 μm using a coater with a doctor blade gap of 200 μm. After coating, the electrode was placed in a vacuum drying oven at 100℃ to remove residual solvent, obtaining a LiMnFePO4 positive electrode. The areal loading of the active material in the obtained positive electrode was 2.6 mg / cm³. 2 The positive electrode sheet is then punched into a circular sheet with a diameter of 12 mm.

[0099] S2. Mix ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1, then add 1 vol% of vinylene carbonate additive, followed by LiPF6 to form a 1 mol / L electrolyte.

[0100] S3. Using a lithium metal sheet as the negative electrode and the LiMnFePO4 positive electrode disc as the positive electrode, a 19mm diameter battery separator is placed between the positive and negative electrodes to form a sandwich structure (wherein the battery separator is the battery separator prepared in Example 1 or Comparative Examples 1 to 5). These are then sequentially installed into a CR2032 battery casing and encapsulated to obtain a coin-type lithium-ion battery for electrochemical performance testing. All batteries were assembled in an environment where the oxygen and moisture content were controlled to be below 0.1ppm.

[0101] Figure 3 These are inductively coupled mass spectra of the battery separators prepared in Example 1 and Comparative Examples 1 to 5 of the present invention for capturing transition metal ions. Figure 3 As shown, compared with uncoated PE membranes, commercial ceramic-coated PE membranes, and commercial MIL-53 powder-coated membranes, the Ni content detected in the surface digestion solution of the membranes obtained in Example 1 and Comparative Examples 1 to 2 of this invention after 500 cycles was significantly lower. 2+ Co 2+ and Mn 2+ The significantly lower content indicates that it can more effectively reduce the dissolution and migration of transition metal ions in the positive electrode.

[0102] Figure 4 This is a comparison chart of the battery cycle performance of the battery separators prepared in Example 1 and Comparative Examples 1 to 5 of the present invention. Figure 4 As shown, the battery corresponding to Example 1 has better long-cycle stability, indicating that introducing ethylenediaminetetraacetic acid into the dual MOF structure can significantly improve the membrane interface regulation capability and enhance cycle life.

[0103] Figure 5 This is a comparison chart of the battery rate performance of the battery separators prepared in Example 1 and Comparative Examples 1 to 5 of the present invention. Figure 5 As shown, the battery corresponding to Example 1 maintains a high discharge specific capacity under different rate conditions, indicating that the separator of the present invention has both good ion transport performance and rate adaptability.

[0104] The above results collectively demonstrate that by constructing a dual MOF and introducing ethylenediaminetetraacetic acid coordination sites, this invention can achieve synergistic optimization of the membrane pore environment, interface state, and transition metal ion capture capability, thereby improving the overall performance of lithium-ion batteries.

[0105] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0106] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A metal-organic framework composite membrane coating material, characterized in that, The metal-organic framework composite membrane coating uses a dual-ligand aluminum-based metal-organic framework composite material as the matrix, with an embedded deprotonated ethylenediaminetetraacetic acid coordinating group. The dual-ligand aluminum-based metal-organic framework composite material has at least the MIL-53-FA phase and the CAU-10-H phase.

2. A method for preparing a metal-organic framework composite membrane coating material according to claim 1, characterized in that, Includes the following steps: A calcium sodium edetate solution was added to a dual-ligand aluminum-based metal-organic framework composite material. The mixture was stirred to allow the edetate ions to enter the pores and / or defect sites of the metal-organic framework composite material. The mixture was then reacted under sealed conditions at 60℃~80℃ to allow the edetate ions to bind to the active sites inside the framework. The resulting metal-organic framework composite membrane coating material was obtained by filtration.

3. The method for preparing the metal-organic framework composite membrane coating material according to claim 2, characterized in that, The solid-liquid ratio of the dual-ligand aluminum-based metal-organic framework composite material and the sodium calcium edetate solution was 1g:5mL~100mL, and the concentration of the sodium calcium edetate solution was 0.01mol / L~1mol / L; the stirring time was 0.5h~12h, and the reaction time was 6h~12h.

4. The method for preparing the metal-organic framework composite membrane coating material according to claim 2, characterized in that, A method for preparing a dual-ligand aluminum-based metal-organic framework composite material includes the following steps: Using aluminum salts of trivalent aluminum ions, trans-butenedioic acid, and isophthalic acid as raw materials, they are dissolved in a mixed solvent, and the pH of the system is adjusted to 4-10 by alkali. The reaction is carried out at 130℃-150℃, cooled to room temperature, and filtered to obtain a dual-ligand aluminum-based metal-organic framework composite material.

5. The method for preparing the metal-organic framework composite membrane coating material according to claim 4, characterized in that, The total molar ratio of trans-butenedioic acid and isophthalic acid to the aluminum ions in the aluminum salt is 0.5–4:1, the molar ratio of trans-butenedioic acid to isophthalic acid is 1–4:1–4, and the solvothermal reaction time is 12–24 h.

6. A battery separator, characterized in that, It includes a base membrane and a functional coating disposed on at least one side of the base membrane, wherein the functional coating is the metal-organic framework composite membrane coating material as described in claim 1.

7. A method for preparing a battery separator according to claim 6, characterized in that, Includes the following steps: A binder, dispersant, solvent, and surfactant are added sequentially to a metal-organic framework composite separator coating material and dispersed and mixed to obtain a slurry. The slurry is then coated onto the surface of a base membrane and dried to obtain a battery separator.

8. The method for preparing the battery separator according to claim 6, characterized in that, The slurry has a solid content of 5wt% to 30wt%. Based on the mass of the metal-organic framework composite membrane coating material, the amount of binder added is 2wt% to 20wt%, the amount of dispersant added is 0.1wt% to 10wt%, and the amount of surfactant added is 0.01wt% to 2wt%.

9. The method for preparing the battery separator according to claim 6, characterized in that, The thickness of the dried single-sided coating is 2μm to 12μm, and the areal density is 0.1mg / cm³. 2 ~2.0mg / cm 2 .

10. The method for preparing the battery separator according to claim 6, characterized in that, The binder is selected from at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinylpyrrolidone, polyimide, polyetherimide, and combinations thereof; the dispersant is selected from at least one of polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol block polymers; the surfactant is selected from at least one of silane coupling agents, fluorinated surfactants, nonionic surfactants, and combinations thereof; and the membrane is selected from polyethylene membranes, polypropylene membranes, polypropylene / polyethylene / polypropylene three-layer composite membranes, or other porous polyolefin membranes.

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