Zr-mof / imide polymer composite, method of making the same, and battery separator based thereon

Abstract

The present application relates to a kind of Zr-MOF / imide polymer composite material and its preparation method and battery separator based on it, wherein the Zr-MOF is dispersed in the two-dimensional sheet network structure formed by the imide polymer;The composite material has microporous-mesoporous composite structure, and the most probable pore diameter is 0.2-2nm;Its specific surface area is 30-300m 2 / g;The organic ligand of the Zr-MOF is aromatic dicarboxylic acid;The monomer of the imide polymer is melamine and aromatic tetracarboxylic dianhydride.The Zr-MOF / imide polymer composite material of the present application helps to improve the kinetics and cycle performance of battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and more particularly to Zr-MOF / imide polymer composite materials, their preparation methods, and battery separators based thereon. Background Technology

[0002] Sodium, with its high abundance, low cost, and wide operating temperature range, holds promise for meeting the requirements of sustainable energy storage applications. Room temperature sodium-sulfur batteries possess ultra-high theoretical specific capacity, theoretical energy density, abundant resources, and high safety. Compared to lithium-ion batteries, they are more competitive in terms of resource sustainability, safety, and adaptability for large-scale applications, and are considered a highly promising next-generation energy storage system. However, their practical application is still severely constrained by multiple problems. First, the low intrinsic conductivity of sulfur and its discharge products limits electron transport; the gradual conversion of polysulfides involves complex multi-electron reaction processes, with S–S bond breaking and reconstruction accompanied by high energy barriers and slow reaction kinetics, resulting in low utilization of active materials, increased polarization, and limited rate performance; the severe "shuttle effect" of long-chain polysulfides, significant volume expansion during charge and discharge, and interfacial instability of the negative electrode cause rapid capacity decay. In summary, poor conductivity, polysulfide shuttle, and slow reaction kinetics are the key challenges currently facing the development of sodium-sulfur batteries.

[0003] As a key component of batteries, the separator plays a crucial role in physically isolating the positive and negative electrodes and preventing short circuits. Its structure and chemical properties directly determine mass transport behavior and interfacial reaction behavior. Rational separator design can effectively regulate the migration and transformation processes of polysulfides, suppress the shuttle effect, and optimize ion / electron transport capabilities, thereby significantly improving the utilization rate of active sulfur and the cycle stability and energy storage efficiency of sodium-sulfur batteries. Given the broad prospects of sodium-sulfur batteries in large-scale energy storage, the development of functional modified separators is of great significance for promoting the efficient utilization of renewable energy and driving the practical development of sodium-sulfur batteries.

[0004] Among the materials currently under research, imide polymers, as a typical class of porous organic polymers, can survive intact in complex electrochemical environments due to their excellent thermal and chemical stability. The synergistic effect between their porous structure and abundant functional groups can effectively regulate polysulfides and ion transport processes, thereby improving the kinetic behavior and cycle performance of sodium-sulfur batteries. However, the pore structure of these materials is usually determined by solvent-induced phase separation and related reactions. The evolution process is regulated by multiple factors such as solvent properties, reaction conditions, and processing technology, exhibiting considerable uncontrollability, thus posing significant challenges in pore structure design. Furthermore, the poor electronic conductivity of these materials hinders their catalytic activity, ultimately resulting in poor rate and cycle performance of sodium-sulfur batteries and low utilization of active sulfur, severely impeding their commercialization. Summary of the Invention

[0005] In view of this, the present invention aims to provide a Zr-MOF / imide polymer composite material, a method for preparing the same, and a battery separator based thereon.

[0006] A first aspect of the present invention relates to providing a Zr-MOF / imide polymer composite material, wherein the Zr-MOF is dispersed in a network structure formed of the imide polymer; The composite material has a microporous-mesoporous composite structure, with a most probable pore size of 0.2-2 nm, preferably 0.7-1.6 nm, and more preferably 0.9-1.2 nm; its specific surface area is 30-300 m². 2 / g, preferably 50-280 m 2 / g, more preferably 100-250 m 2 / g; The organic ligand of the Zr-MOF is an aromatic dicarboxylic acid; The monomers of the imide polymer are melamine and aromatic tetracarboxylic acid dianhydride.

[0007] A second aspect of the present invention relates to providing a method for preparing the Zr-MOF / imide polymer composite material of the present invention, comprising the following steps: i) React the Zr source with an aromatic dicarboxylic acid as an organic ligand to obtain Zr-MOF; ii) React melamine with aromatic tetracarboxylic acid dianhydride to obtain a precursor solution; iii) Mix the Zr-MOF with the precursor solution to obtain a Zr-MOF / precursor mixed solution; and iv) Heating the Zr-MOF / precursor mixed solution yields a Zr-MOF / imide polymer composite material.

[0008] A third aspect of the invention relates to providing a battery separator comprising the Zr-MOF / imide polymer composite material of the present invention or a Zr-MOF / imide polymer composite material prepared by the method of the present invention.

[0009] The beneficial effects of this invention are as follows: This invention provides a Zr-MOF / imide polymer composite material, wherein the Zr-MOF is dispersed in a two-dimensional sheet-like network structure formed by the imide polymer. In this Zr-MOF / imide polymer composite material, the two-dimensional polymerization reaction is induced by the ordered pre-assembly of melamine monomer and aromatic tetracarboxylic acid dianhydride monomer. The resulting two-dimensional network structure imide polymer has an ordered molecular arrangement, improving the overall chemical and mechanical stability of the material. Furthermore, this invention utilizes the multiple hydrogen bond interactions between the carboxyl and amino groups on the Zr-MOF surface and the N and O groups on the polyamic acid precursor surface, ensuring that Zr-MOF particles are uniformly dispersed on the two-dimensional network framework of the imide polymer. This avoids disordered aggregation and layer stacking of MOF particles, facilitating the full exposure of ion-accessible active sites.

[0010] Furthermore, the abundant functional groups on the surface of Zr-MOF and imide polymers significantly enhance their binding capacity to polysulfides, which helps to prevent the dissolution and shuttle of soluble polysulfides and promotes the conversion reaction between sulfur and various intermediates.

[0011] Meanwhile, in the Zr-MOF / imide polymer composite material of the present invention, the two-dimensional imide polymer network and Zr-MOF composite form a dense physical barrier to block the diffusion of polysulfides; and the pore channels present after the two-dimensional imide polymer network and Zr-MOF composite shorten the sodium ion transport path, reduce ion transport resistance, and accelerate charge storage kinetics.

[0012] In summary, the Zr-MOF / imide polymer composite material of the present invention can effectively suppress the diffusion of polysulfides, resulting in excellent ionic / electronic conductivity and a reduced reaction energy barrier, which helps to improve the kinetics and cycle performance of sodium-ion batteries. Attached Figure Description

[0013] Figure 1 The image shows the microstructure of the Zr-MOF / imide polymer composite material from Example 1. Figure 2 The Fourier transform infrared spectrum of the Zr-MOF / imide polymer composite material in Example 1 is shown below. Figure 3 The nitrogen isotherm adsorption-desorption curve of the Zr-MOF / imide polymer composite material in Example 1 is shown. Figure 4 The micropore-mesopore size distribution diagram of the Zr-MOF / imide polymer composite material in Example 1 is shown. Figure 5 The graph shows the cycle performance test results of a coin cell sodium-sulfur battery assembled with a separator modified by the Zr-MOF / imide polymer composite material of Example 1. Figure 6 Electrochemical impedance spectroscopy of a coin cell sodium-sulfur battery assembled with a separator modified by the Zr-MOF / imide polymer composite material of Example 1. Figure 7 The image shows the microstructure of the Zr-MOF / imide polymer composite material from Example 2. Figure 8 The Fourier transform infrared spectrum of the Zr-MOF / imide polymer composite material in Example 2 is shown below. Figure 9 The nitrogen isotherm adsorption-desorption curve of the Zr-MOF / imide polymer composite material in Example 2 is shown. Figure 10 This is a micropore-mesopore size distribution diagram of the Zr-MOF / imide polymer composite material in Example 2; Figure 11 The graph shows the cycle performance test results of a coin cell sodium-sulfur battery assembled with a separator modified by the Zr-MOF / imide polymer composite material of Example 2. Figure 12 Electrochemical impedance spectroscopy of a coin cell sodium-sulfur battery assembled with a separator modified by the Zr-MOF / imide polymer composite material of Example 2. Figure 13 The image shows the microstructure of the Zr-MOF / imide polymer composite material in Example 3. Figure 14 The Fourier transform infrared spectrum of the Zr-MOF / imide polymer composite material in Example 3 is shown below. Figure 15 The nitrogen isotherm adsorption-desorption curve of the Zr-MOF / imide polymer composite material in Example 3 is shown. Figure 16 This is a micropore-mesopore size distribution diagram of the Zr-MOF / imide polymer composite material in Example 3; Figure 17 The graph shows the cycle performance test results of a coin cell sodium-sulfur battery assembled based on the Zr-MOF / imide polymer composite material modified membrane of Example 3. Figure 18 Electrochemical impedance spectroscopy (EIS) of a coin cell sodium-sulfur battery assembled using a modified separator based on the Zr-MOF / imide polymer composite material from Example 3. Detailed Implementation

[0014] The invention will be described in more detail below.

[0015] As used herein, the term “comprising” and its synonyms “including” and “containing” mean “including but not limited to”, and are not intended to exclude, for example, other additives, components, integers or steps.

[0016] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that the ranges 60-110 and 80-120 will also be understood.

[0017] Unless otherwise specified, all steps in this application may be performed sequentially, randomly, or simultaneously. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially, or steps (a) and (b) performed simultaneously. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0018] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0019] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0020] Unless otherwise specified, the operations mentioned in this application are performed at room temperature and normal pressure.

[0021] Unless otherwise specified, all concentrations and proportions mentioned in this application are based on weight.

[0022] Unless otherwise specified, the operations mentioned in this application can be performed in a manner known to those skilled in the art.

[0023] Unless otherwise specified, the equipment, apparatus, instruments, parts, materials, reagents, etc. mentioned in this application can be obtained by means known to those skilled in the art.

[0024] Unless otherwise specified, the parameters mentioned in this application, such as pore size, specific surface area, capacity retention, coulombic efficiency, and interfacial charge resistance, can be measured by means known to those skilled in the art.

[0025] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

[0026] Terminology Definition The term "MOF" as used in this invention refers to a metal-organic framework, a crystalline material with a periodic porous structure formed by the self-assembly of metal ions or metal clusters as nodes and organic ligands through coordination bonds. Examples of MOFs include, but are not limited to, zirconium-based MOFs (e.g., UiO-66, UiO-66-NH2, UiO-67, NU-1000, etc.), iron-based MOFs (e.g., MIL-53, MIL-100, MIL-101, etc.), zinc-based MOFs (e.g., ZIF-8, ZIF-67, etc.), and copper-based MOFs (e.g., HKUST-1, etc.). The terms "Zr-MOF," "zirconium-based metal-organic framework," or "zirconium-based MOF" as used in this invention refer to metal-organic frameworks with zirconium ions or zirconium oxide clusters as metal nodes.

[0027] The term "imide polymer" as used in this invention refers to a class of high molecular weight polymers containing repeating five-membered imide ring structural units (-CO-NR-CO-, where R is a hydrogen atom, alkyl, or aryl group) in the main chain. They are typically produced by polyamic acid precursors generated from polyamine monomers and polycarboxylic acids or their derivatives (such as acid anhydrides or acyl chlorides) through a polycondensation reaction, followed by thermal or chemical dehydration and cyclization. The polyamine monomers include diamines, triamines, and polyamine monomers with higher functionality; the polycarboxylic acids or their derivatives include dicarboxylic acids, tetracarboxylic acids, and their derivatives (such as dianhydrides and tetraacyl chlorides). Examples of imide polymers include, but are not limited to, aromatic polyimides, aliphatic polyimides, linear polyimides, and cross-linked polyimides.

[0028] The term "aromatic dicarboxylic acid" as used in this invention refers to an organic compound whose molecular structure contains two carboxyl groups, with the carboxyl groups directly linked to the aromatic ring skeleton. Examples of aromatic dicarboxylic acids include, but are not limited to, terephthalic acid, isophthalic acid, phthalic acid, 2-aminoterephthalic acid, 2-nitroterephthalic acid, 2-chloroterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, and their derivatives.

[0029] The term "aromatic tetracarboxylic dianhydride" as used in this invention refers to an organic compound whose molecular structure contains two anhydride rings directly connected to the aromatic ring skeleton. These two anhydride rings are formed by the dehydration of four carboxyl groups connected to the aromatic ring in two pairs of adjacent carboxyl groups. Examples of aromatic tetracarboxylic dianhydrides include, but are not limited to, pyromellitic dianhydride (PMDA), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 4,4'-oxobisphthalic anhydride (ODPA), 2,3,6,7-naphthalenetetracarboxylic dianhydride, and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA).

[0030] product According to one aspect of the present invention, a Zr-MOF / imide polymer composite material is provided, wherein the Zr-MOF is dispersed in a two-dimensional sheet-like network structure formed by the imide polymer; the composite material has a microporous-mesoporous composite structure with a most probable pore size of 0.2-2 nm and a specific surface area of ​​30-300 m². 2 / g; the organic ligand of the Zr-MOF is an aromatic dicarboxylic acid; the monomer of the imide polymer is melamine and aromatic tetracarboxylic dianhydride.

[0031] Unbound by any particular theory, the inventors unexpectedly discovered that in the Zr-MOF / imide polymer composite material of this invention, the ordered pre-assembly of melamine monomers and aromatic tetracarboxylic acid dianhydride monomers induces a two-dimensional polymerization reaction, resulting in a two-dimensional network structure imide polymer with an ordered molecular arrangement, thus enhancing the overall chemical and mechanical stability of the material. Furthermore, this invention utilizes the multiple hydrogen bond interactions between the carboxyl and amino groups on the Zr-MOF surface and the N and O groups on the polyamic acid precursor surface, ensuring that Zr-MOF particles are uniformly dispersed on the two-dimensional network framework of the imide polymer. This avoids disordered aggregation and layering of MOF particles, facilitating the full exposure of ion-accessible active sites. In addition, the abundant functional groups on the surfaces of Zr-MOF and the imide polymer significantly enhance the binding capacity for polysulfides, helping to prevent the dissolution and shuttle of soluble polysulfides and promoting the conversion reactions between sulfur and various intermediates. Meanwhile, in the Zr-MOF / imide polymer composite material of the present invention, the two-dimensional imide polymer network and Zr-MOF composite form a dense physical barrier, blocking the diffusion of polysulfides; and the pore channels present after the two-dimensional imide polymer network and Zr-MOF composite shorten the sodium ion transport path, reduce ion transport resistance, and accelerate charge storage kinetics. Therefore, the Zr-MOF / imide polymer composite material of the present invention can provide excellent electrochemical performance, for example, when used in battery separators to provide good rate and cycle performance of batteries.

[0032] In a preferred embodiment of the present invention, the most probable pore size of the Zr-MOF / imide polymer composite material is 0.7-1.6 nm, preferably 0.9-1.2 nm; its specific surface area is 50-280 m². 2 / g, preferably 100-250 m 2 / g. Therefore, the Zr-MOF / imide polymer composite material of the present invention is advantageous in providing better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0033] In one embodiment of the invention, the aromatic dicarboxylic acid is selected from terephthalic acid and 2-aminoterephthalic acid, preferably 2-aminoterephthalic acid. This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0034] In one embodiment of the present invention, the aromatic tetracarboxylic dianhydride is selected from 1,4,5,8-naphthalenetetracarboxylic anhydride (NTCDA), pyromellitic dianhydride (PMDA), and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BD), preferably from PMDA and BD, and more preferably from PMDA. This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0035] Preparation method According to one aspect of the present invention, the present invention also provides a method for preparing the Zr-MOF / imide polymer composite material of the present invention, comprising the following steps: i) reacting a Zr source with an aromatic dicarboxylic acid as an organic ligand to obtain Zr-MOF; ii) reacting melamine with an aromatic tetracarboxylic acid dianhydride to obtain a precursor solution; iii) mixing the Zr-MOF with the precursor solution to obtain a Zr-MOF / precursor mixed solution; and iv) heating the Zr-MOF / precursor mixed solution to obtain the Zr-MOF / imide polymer composite material.

[0036] In one embodiment of the invention, the aromatic dicarboxylic acid is selected from terephthalic acid and 2-aminoterephthalic acid, preferably 2-aminoterephthalic acid. This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0037] In one embodiment of the present invention, the aromatic tetracarboxylic dianhydride is selected from 1,4,5,8-naphthalenetetracarboxylic anhydride (NTCDA), pyromellitic dianhydride (PMDA), and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BD), preferably from PMDA and BD, and more preferably from PMDA. This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0038] In one embodiment of the present invention, in step i), the molar ratio of the Zr source (based on Zr atoms, i.e., Zr element) to the aromatic dicarboxylic acid is 1:(0.5~3), preferably 1:(0.8~2), and more preferably 1:(1~1.6). This benefits the Zr-MOF / imide polymer composite material of the present invention by providing better electrochemical performance, for example, for use in battery separators to provide better rate and cycle performance of the battery.

[0039] In one embodiment of the present invention, in step i), a Zr source is mixed with an aromatic dicarboxylic acid as an organic ligand and heated to react and obtain Zr-MOF. The heating is performed at a rate of 3-9 °C / min, preferably 4-8 °C / min, more preferably 4.5-6.5 °C / min, to a temperature of 60-160 °C, preferably 65-130 °C, more preferably 70-100 °C, and held at this temperature for 6-18 hours, preferably 9-16 hours, more preferably 10-14 hours. This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance.

[0040] In a further embodiment of the invention, after reacting the Zr source with an aromatic dicarboxylic acid as an organic ligand in step i), optional post-processing may be performed. The post-processing includes, but is not limited to, separation, washing, and drying. Preferably, the separation is centrifugation. Preferably, the washing involves washing the Zr-MOF obtained from the reaction with a substance selected from anhydrous methanol, anhydrous ethanol, and anhydrous acetone. Preferably, the drying is vacuum drying; more preferably, the vacuum drying conditions are drying at 60-80°C and -0.04 to -0.12 MPa for 10-18 hours. This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, for use in battery separators to provide better rate and cycle performance of the battery.

[0041] In one embodiment of the invention, in step ii), the molar ratio of melamine to aromatic tetracarboxylic dianhydride is 1:(0.5~5), preferably 1:(1.1~3.3), and more preferably 1:(1.5~2.5). This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0042] In one embodiment of the present invention, in step iii), the mass ratio of the Zr-MOF to the imide polymer available from the precursor solution is 1:(0.1~6), preferably 1:(0.5~5), and more preferably 1:(1~3). This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0043] In one embodiment of the invention, in step iv), the heating method is at least one of heating via a pressure-resistant tube device, microwave heating, and heating via a forced-air oven device, preferably microwave heating. This benefits the Zr-MOF / imide polymer composite material of the present invention by providing better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0044] In one embodiment of the invention, in step iv), the heating is performed at a heating rate of 3-12 °C / min, preferably 4.5-9.5 °C / min, more preferably 7-9 °C / min, to 160-250 °C, preferably 185-235 °C, more preferably 190-210 °C, and held at that temperature for 0.5-24 hours, preferably 0.8-12 hours, more preferably 1-3 hours. This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, when used in battery separators to provide better rate and cycle performance of the battery.

[0045] In one embodiment of the invention, in step iv), after heating the Zr-MOF / precursor mixture, optional post-treatment may be performed. The post-treatment includes, but is not limited to, separation, washing, and drying. Preferably, the separation is centrifugation. Preferably, the washing involves washing the resulting Zr-MOF / imide polymer composite material with a substance selected from N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc), using hot water, anhydrous ethanol, and acetone. Preferably, the drying is vacuum drying; more preferably, the vacuum drying conditions are drying at 60-160°C, preferably 80-140°C, more preferably 90-110°C, and -0.04 to -0.12 MPa for 6-26 hours, preferably 8-18 hours, more preferably 10-14 hours. This allows the Zr-MOF / imide polymer composite material of the present invention to provide better electrochemical performance, for example, for use in battery separators to provide better rate and cycle performance.

[0046] Battery separator According to one aspect of the present invention, the present invention also provides a battery separator comprising the Zr-MOF / imide polymer composite material of the present invention or the Zr-MOF / imide polymer composite material prepared by the method of the present invention.

[0047] In one embodiment of the present invention, the battery separator further comprises a conductive agent. The conductive agent may be selected from electrochemical carbon-based conductive agents, including one or more of amorphous carbon-based conductive fillers and crystalline nano-carbon-based conductive fillers, such as conductive carbon black, carbon nanotubes, graphene, and acetylene black, preferably carbon nanotubes. This allows the battery separator of the present invention to provide better rate performance and cycle life for the battery.

[0048] In a preferred embodiment of the present invention, the battery separator of the present invention contains 100 parts by weight of the Zr-MOF / imide polymer composite material and 5-100 parts by weight of the conductive agent, preferably 10-70 parts by weight, more preferably 15-45 parts by weight. This allows the battery separator of the present invention to provide better rate capability and cycle performance for the battery.

[0049] In one embodiment of the present invention, the battery separator further comprises a binder, which may be selected from halogenated alkenyl homopolymers, carboxylic acid alkenyl homopolymers, and aromatic alkenyl homopolymers, preferably selected from fluorinated vinyl homopolymers, chlorinated vinyl homopolymers, vinyl carboxylic acid homopolymers, and aromatic vinyl homopolymers, such as polyvinylidene fluoride, polyvinyl chloride, polytetrafluoroethylene, polyacrylic acid, polystyrene, chlorinated polyvinyl chloride, etc., and preferably polyvinylidene fluoride. Therefore, the battery separator of the present invention is advantageous in providing better rate performance and cycle performance for the battery.

[0050] In a preferred embodiment of the present invention, the battery separator of the present invention contains 100 parts by weight of the Zr-MOF / imide polymer composite material and 5-25 parts by weight, preferably 8-18 parts by weight, more preferably 13-16 parts by weight. This allows the battery separator of the present invention to provide better rate capability and cycle performance for the battery.

[0051] Example To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] Unless otherwise stated, all reagents and instruments used are commercially available products commonly used in the art, or can be prepared by those skilled in the art. In the embodiments of this invention, unless otherwise stated, all operations are performed at room temperature and normal pressure. Unless otherwise stated, all contents and percentages in the context of this application are based on weight.

[0053] Preparation of Zr-MOF / imide polymer composite materials and battery separators based thereon Example 1: Step S1: Add 0.5411 g of zirconium tetrachloride tetrahydrate to 20 mL of N,N-dimethylformamide (DMF), then inject 5 mL of 2 mol / L acetic acid solution. Sonicate the resulting mixture for 60 minutes to obtain the Zr source system. Disperse 0.1768 g of terephthalic acid ligand in 20 mL of DMF using ultrasonication to obtain the organic ligand system. The molar ratio of zirconium tetrachloride tetrahydrate to terephthalic acid ligand is approximately 1:0.60.

[0054] Step S2: The Zr source system and organic ligand system obtained in Step S1 are mixed, and then ultrasonically treated to ensure uniform dispersion, resulting in a mixed system. The resulting mixed system is heated using a solvothermal method at a heating rate of 3℃ / min to 120℃, held at 120℃ for 8 hours, and then allowed to cool naturally to room temperature. The heated mixed system is centrifuged to separate the solid product. The separated solid product is washed with anhydrous methanol and anhydrous ethanol, and then vacuum dried. The vacuum drying conditions are 60℃ and -0.08MPa for 12 hours. After the above treatment, 0.23 g of solid zirconium-based metal-organic framework (Zr-MOF) material is obtained. Steps S1-S2 are repeated several times to prepare sufficient Zr-MOF for later use.

[0055] Step S3: Under stirring conditions, 0.3784 g of melamine (MA) dispersion in 30 ml DMF was added dropwise to a solution of 0.8045 g of 1,4,5,8-naphthalenetetracarboxylic anhydride (NTCDA) in 30 ml DMF. The mixture was stirred vigorously for 4 hours to obtain 60 ml of a pre-assembled precursor solution. (Based on preliminary experiments, the precursor solution obtained with this amount of melamine and 1,4,5,8-naphthalenetetracarboxylic anhydride, after heating, separation, and drying, can be used to prepare 0.9 g of an imide polymer). The molar ratio of melamine to 1,4,5,8-naphthalenetetracarboxylic anhydride was 1:1.

[0056] Step S4: Add 2.7g of the zirconium-based metal-organic framework (Zr-MOF) material prepared in the aforementioned steps to 20ml of the precursor solution prepared in the previous steps (according to preliminary experiments, 0.3g of an imide polymer can be prepared by heating, separating, and drying the precursor solution obtained with this amount of melamine and 1,4,5,8-naphthalenetetracarboxylic anhydride). Stir for 2 hours to ensure thorough mixing, obtaining a Zr-MOF / precursor mixed solution. Calculations show that the mass ratio of Zr-MOF to the imide polymer in the Zr-MOF / imide polymer composite is 1:0.11.

[0057] Step S5: The Zr-MOF / precursor mixed solution obtained in Step S4 is transferred to a pressure-resistant tube and sealed. The solution is heated to 180°C at a heating rate of 10°C / min using a pressure-resistant tube apparatus and held at 180°C for 12 hours, followed by natural cooling to room temperature. The solid product within the pressure-resistant tube is then separated from the solution by centrifugation and washed with N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and anhydrous ethanol, followed by vacuum drying. The vacuum drying conditions are 70°C and -0.08 MPa for 18 hours. After the above treatment, the Zr-MOF / imide polymer composite material is finally obtained.

[0058] Step S6: Mix 2.85g of the Zr-MOF / imide polymer composite material prepared above with 2.28g of multi-walled carbon nanotubes (commercially purchased product, from Zancheng (Tianjin) Technology Co., Ltd.) (weight ratio of Zr-MOF / imide polymer composite material to multi-walled carbon nanotubes is 1:0.8), and add 0.57g of polyvinylidene fluoride (PVDF) in 40ml of NMP solution (weight ratio of Zr-MOF / imide polymer composite material to PVDF is 1:0.2), stir to obtain a slurry. Coat 0.1g of this slurry onto a commercially available separator (commercially purchased glass fiber product, 340 micrometers thick, from Whatman) to obtain a battery separator based on the Zr-MOF / imide polymer composite material.

[0059] Example 2: Step S1: Add 0.5411 g of zirconium tetrachloride tetrahydrate to 15 mL of N,N-dimethylformamide (DMF), then inject 3 mL of 12 mol / L hydrochloric acid solution. Sonicate the resulting mixture for 30 minutes to obtain the Zr source system. Disperse 0.4466 g of 2-aminoterephthalic acid ligand in 30 mL of DMF using ultrasonication to obtain 30 mL of the organic ligand system. The molar ratio of zirconium tetrachloride tetrahydrate to 2-aminoterephthalic acid ligand is approximately 1:1.39.

[0060] Step S2: The Zr source system and organic ligand system obtained in Step S1 are mixed, and then ultrasonically treated to ensure uniform dispersion, resulting in a mixed system. The resulting mixed system is heated under reflux at a heating rate of 5℃ / min to 80℃, and held at 80℃ for 12 hours, followed by natural cooling to room temperature. The heated mixed system is centrifuged to separate the solid product. The separated solid product is washed with anhydrous methanol and anhydrous acetone, and then vacuum dried. The vacuum drying conditions are 70℃ and -0.08MPa for 12 hours. After the above treatment, 0.45 g of solid zirconium-based metal-organic framework (Zr-MOF) material is obtained.

[0061] Step S3: Under stirring conditions, 0.3784 g of melamine (MA) dispersion in 20 ml NMP was added dropwise to a solution of 1.3087 g of pyromellitic dianhydride (PMDA) in 20 ml NMP. The mixture was stirred vigorously for 12 hours to obtain 40 ml of the pre-assembled precursor solution. (Based on preliminary experiments, the precursor solution obtained with this amount of melamine and pyromellitic dianhydride, after heating, separation, and drying, can be used to prepare 0.69 g of an imide polymer). The molar ratio of melamine to pyromellitic dianhydride was 1:2.

[0062] Step S4: Add 0.23g of the zirconium-based metal-organic framework (Zr-MOF) material prepared in the aforementioned steps to 20ml of the precursor solution prepared in the previous steps (according to preliminary experiments, 0.345g of imide polymer can be prepared by heating, separating, and drying the precursor solution obtained with this amount of melamine and pyromellitic dianhydride). Stir for 4 hours to ensure thorough mixing, obtaining a Zr-MOF / precursor mixed solution. Calculations show that the mass ratio of Zr-MOF to imide polymer in the Zr-MOF / imide polymer composite material is 1:1.5.

[0063] Step S5: The Zr-MOF / precursor mixed solution obtained in Step S4 was transferred to a sealed flask and heated to 200°C using a microwave reactor at a heating rate of 8.75°C / min. This temperature was maintained at 200°C for 2 hours, followed by natural cooling to room temperature. The solid product in the flask was then separated from the solution by centrifugation and washed with N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), hot water, and anhydrous ethanol, followed by vacuum drying. The vacuum drying conditions were 100°C and -0.08 MPa for 12 hours. After the above treatment, the Zr-MOF / imide polymer composite material was finally obtained.

[0064] Step S6: Mix 0.55g of the Zr-MOF / imide polymer composite material prepared above with 0.1571g of multi-walled carbon nanotubes (commercially available product, purchased from Zancheng (Tianjin) Technology Co., Ltd.) (weight ratio of Zr-MOF / imide polymer composite material to multi-walled carbon nanotubes is 1:0.29), and add 0.0786g of polyvinylidene fluoride (PVDF) in 10ml of NMP solution (weight ratio of Zr-MOF / imide polymer composite material to PVDF is 1:0.14), stir to obtain a slurry. Coat 0.06g of this slurry onto a commercially available separator (commercially available product, 340 micrometers thick, purchased from Whatman) to obtain a battery separator based on the Zr-MOF / imide polymer composite material.

[0065] Example 3: Step S1: Add 0.5411 g of zirconium tetrachloride tetrahydrate to 30 mL of N,N-dimethylformamide (DMF), then inject 8 mL of 6 mol / L hydrochloric acid solution. Sonicate the resulting mixture for 45 minutes to obtain the Zr source system. Disperse 0.5783 g of 2-aminoterephthalic acid ligand in 30 mL of DMF using ultrasonication to obtain the organic ligand system. The molar ratio of zirconium tetrachloride tetrahydrate to 2-aminoterephthalic acid ligand is approximately 1:1.8.

[0066] Step S2: The Zr source system and organic ligand system obtained in Step S1 were mixed, followed by ultrasonic treatment to ensure uniform dispersion, resulting in a mixed system. The resulting mixed system was heated under reflux at a heating rate of 7.5℃ / min to 140℃ and held at 140℃ for 16 hours, then allowed to cool naturally to room temperature. The heated mixed system was centrifuged to separate the solid product. The separated solid product was washed with anhydrous ethanol and anhydrous acetone, followed by vacuum drying. The vacuum drying conditions were 80℃ and -0.08 MPa for 16 hours. After the above treatment, 0.44 g of solid zirconium-based metal-organic framework (Zr-MOF) material was obtained.

[0067] Step S3: Under stirring conditions, 0.3784 g of melamine (MA) dispersion in 40 ml DMF was added dropwise to a solution of 2.6480 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BD) in 40 ml DMF. The mixture was stirred vigorously for 24 hours to obtain 80 ml of a pre-assembled precursor solution. (Based on preliminary experiments, the precursor solution obtained with this amount of melamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride, after heating, separation, and drying, can prepare 0.65 g of an imide polymer). The molar ratio of melamine to 3,3',4,4'-biphenyltetracarboxylic dianhydride was 1:3.

[0068] Step S4: Add 0.13g of the zirconium-based metal-organic framework (Zr-MOF) material prepared in the aforementioned steps to 80ml of the precursor solution prepared in the previous steps (according to preliminary experiments, 0.65g of an imide polymer can be prepared by heating, separating, and drying the precursor solution obtained with this amount of melamine and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride). Stir for 4 hours to ensure thorough mixing, obtaining a Zr-MOF / precursor mixed solution. Calculations show that the mass ratio of Zr-MOF to the imide polymer in the Zr-MOF / imide polymer composite material is 1:5.

[0069] Step S5: The Zr-MOF / precursor mixed solution obtained in Step S4 was transferred to a sealed reactor and heated to 230°C using a forced-air drying oven at a heating rate of 5°C / min. This temperature was maintained at 230°C for 24 hours, followed by natural cooling to room temperature. The solid product in the reactor was then separated from the solution by centrifugation and washed with N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), acetone, and hot water, followed by vacuum drying. The vacuum drying conditions were 120°C and -0.08 MPa for 24 hours. After the above treatment, the Zr-MOF / imide polymer composite material was finally obtained.

[0070] Step S6: Mix 0.70g of the Zr-MOF / imide polymer composite material prepared above with 0.0875g of multi-walled carbon nanotubes (commercially available product, purchased from Zancheng (Tianjin) Technology Co., Ltd.) (weight ratio of Zr-MOF / imide polymer composite material to multi-walled carbon nanotubes is 1:0.13), and add 0.0875g of polyvinylidene fluoride (PVDF) in 8ml of NMP solution (weight ratio of Zr-MOF / imide polymer composite material to PVDF is 1:0.125), stir to obtain a slurry. Coat 0.15g of this slurry onto a commercially available glass fiber separator (commercially available product, 340 micrometers thick, purchased from Whatman) to obtain a battery separator based on the Zr-MOF / imide polymer composite material.

[0071] Preparation of test batteries Positive electrode: The derived carbon / sulfur obtained by high-temperature calcination of the Zr-MOF / imide polymer composite material prepared in Example 1 was used as the positive electrode. The preparation process was as follows: the above composite material was subjected to high-temperature treatment in an inert atmosphere at a constant heating rate in a tube furnace to obtain the derived carbon material; then it was mixed with sublimed sulfur in a 1:1 ratio and treated at 155°C by melt treatment to prepare the corresponding derived carbon / sulfur positive electrode.

[0072] Negative electrode: Sodium.

[0073] Test battery of Example 1 Using the aforementioned positive and negative electrodes, and the Zr-MOF / imide polymer composite material prepared in Example 1 as the battery separator (diameter: 16 mm, thickness: 503.2 μm), a quasi-solid-state sodium-ion CR2032 button battery was assembled. The electrolyte consisted of sodium hexafluorophosphate solute and EC (ethylene carbonate) / DEC (diethyl carbonate) + 5% FEC (fluoroethylene carbonate) solvent (commercially purchased product, product code NP-002, composition 1M NaPF6in DEC:EC=1:1 Vol% with 5% FEC, purchased from Suzhou Duoduo Chemical Technology Co., Ltd.).

[0074] Test battery of Example 2 Using the aforementioned positive and negative electrodes, and the Zr-MOF / imide polymer composite material prepared in Example 2 as the battery separator (diameter: 16 mm, thickness: 397.4 μm), a quasi-solid-state sodium-ion CR2032 button battery was assembled. The electrolyte consisted of sodium trifluoromethanesulfonate solute and diethylene glycol dimethyl ether (DEGDME, or DIGLYME) solvent (commercially purchased product, item number NS-001, composition 1M NaCF3SO3 in DIGLYME = 100 Vol%, purchased from Suzhou Duoduo Chemical Technology Co., Ltd.).

[0075] Test battery of Example 3 Using the aforementioned positive and negative electrodes, and the Zr-MOF / imide polymer composite material prepared in Example 3 as the battery separator (diameter: 16 mm, thickness: 613.8 μm), a quasi-solid-state sodium-ion CR2032 button cell was assembled. The electrolyte consisted of sodium bis(trifluoromethanesulfonate) solute and dimethyl ethylene glycol (DME) solvent (commercially purchased product, trade code LX-771, composition 1M NaTFSI in DME = 100 Vol%, purchased from Suzhou Duoduo Chemical Technology Co., Ltd.).

[0076] test Test 1: Transmission Electron Microscopy Characterization The Zr-MOF / imide polymer composites prepared in Examples 1-3 were characterized using transmission electron microscopy (TEM). The microstructure of the composite material prepared in Example 1 is shown below. Figure 1 As shown; the microstructure of the composite material obtained in Example 2 is as follows. Figure 7 As shown; the microstructure of the composite material obtained in Example 3 is as follows. Figure 13 As shown.

[0077] Test 2: Fourier Transform Infrared Spectroscopy (FTIR) Characterization The Zr-MOF / imide polymer composites prepared in Examples 1-3 were characterized using Fourier transform infrared spectroscopy (FTIR). The Fourier transform infrared spectrum of the composite material prepared in Example 1 is shown below. Figure 2 As shown; the Fourier transform infrared spectrum of the composite material prepared in Example 2 is shown below. Figure 8 As shown; the Fourier transform infrared spectrum of the composite material prepared in Example 3 is shown below. Figure 14 As shown.

[0078] Test 3. Nitrogen adsorption-desorption test Test in Example 1 The Zr-MOF / imide polymer composite material prepared in Example 1 was subjected to nitrogen adsorption-desorption tests, and the test results are shown in the figure. Figure 3 and Figure 4 The results show that the composite material has a typical microporous-mesoporous composite structure, with a most probable pore size of 0.814 nm and mesopore sizes of 4.2-19.2 nm and 50.2 nm. As can be seen from the images, the mesopore content of this composite material is very low, and the main pore type is micropores. The BET specific surface area is 34.2 m². 2 / g.

[0079] Test in Example 2 The Zr-MOF / imide polymer composite material prepared in Example 2 was subjected to nitrogen adsorption-desorption tests, and the test results are shown in the figure. Figure 9 and Figure 10 The results show that the composite material has a typical microporous-mesoporous composite structure, with a most probable pore size of 0.920 nm and a mesopore size of 2.61 nm. As can be seen from the images, the composite material has a very low mesopore content, with micropores being the dominant pore type. The BET specific surface area is 177.6 m². 2 / g.

[0080] Test in Example 3 The Zr-MOF / imide polymer composite material prepared in Example 3 was subjected to nitrogen adsorption-desorption tests, and the test results are shown in [Figure 3]. Figure 15 and Figure 16 The results show that the composite material possesses a typical microporous-mesoporous composite structure, with a most probable pore size of 0.395 nm, mesopore sizes of 11.78-24.1 nm and 38.6 nm, and a BET specific surface area of ​​59.3 m². 2 / g.

[0081] Test 4: Constant Current Charge and Discharge Test Testing equipment: LAND battery testing system Test conditions: At room temperature, charge / discharge voltage range of 0.8~2.8V. Initial charge / discharge at 0.1 A g. -1 Activation was performed at a current density, and cycle performance was tested at 1 A g. -1 The experiment was conducted at current density.

[0082] Test in Example 1 The test battery of Example 1 was tested. The test results are shown below. Figure 5 .

[0083] Depend on Figure 5 It can be seen that the sodium-ion secondary battery assembled based on the Zr-MOF / imide polymer composite material prepared in Example 1 as the battery separator has a capacity retention rate of 53.2% and a coulombic efficiency of 98.1% after 400 cycles.

[0084] Test in Example 2 The test battery of Example 2 was tested. The test results are shown below. Figure 11 .

[0085] Depend on Figure 11 It can be seen that the sodium-ion secondary battery assembled based on the Zr-MOF / imide polymer composite material prepared in Example 2 as the battery separator has a capacity retention rate of 100.8% and a coulombic efficiency of 100.1% after 400 cycles.

[0086] Test in Example 3 The test battery of Example 3 was tested. The test results are shown below. Figure 17 .

[0087] Depend on Figure 17 It can be seen that the sodium-ion secondary battery assembled based on the Zr-MOF / imide polymer composite material prepared in Example 3 as the battery separator has a capacity retention rate of 83.6% and a coulombic efficiency of 99.0% after 400 cycles.

[0088] Test 5: Electrochemical Impedance Testing Testing setup: Electrochemical workstation (CHI 660E) Test conditions: The test frequency range is 0.01Hz ~ 100kHz, the AC voltage amplitude is 5mV, and there is no DC bias.

[0089] Test in Example 1 The test battery of Example 1 was tested. The test results are shown below. Figure 6The results showed that the interfacial charge impedance of the sodium-ion secondary battery assembled using the Zr-MOF / imide polymer composite material prepared in Example 1 as the battery separator was 146.8 ohms.

[0090] Test in Example 2 The test battery of Example 2 was tested. The test results are shown below. Figure 12 The results showed that the interfacial charge impedance of the sodium-ion secondary battery assembled using the Zr-MOF / imide polymer composite material prepared in Example 2 as the battery separator was 28.7 ohms.

[0091] Test in Example 3 The test battery of Example 3 was tested. The test results are shown below. Figure 18 The results showed that the interfacial charge impedance of the sodium-ion secondary battery assembled using the Zr-MOF / imide polymer composite material prepared in Example 3 as the battery separator was 80.1 ohms.

[0092] The reactant ratios and properties of the Zr-MOF / imide polymer composite materials prepared in the embodiments of the present invention and the battery separators based thereon are summarized in the table below: Table 1: Molar ratios and properties of the composite materials prepared in the examples and the battery separators based thereon Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A Zr-MOF / imide polymer composite material, wherein, The Zr-MOF is dispersed in a network structure formed by the imide polymer; The composite material has a microporous-mesoporous composite structure, with a most probable pore size of 0.2-2 nm, preferably 0.7-1.6 nm, and more preferably 0.9-1.2 nm; its specific surface area is 30-300 m². 2 / g, preferably 50-280 m 2 / g, more preferably 100-250 m 2 / g; The organic ligand of the Zr-MOF is an aromatic dicarboxylic acid; The monomers of the imide polymer are melamine and aromatic tetracarboxylic acid dianhydride.

2. The Zr-MOF / imide polymer composite material according to claim 1, wherein, The aromatic dicarboxylic acid is selected from terephthalic acid and 2-aminoterephthalic acid, preferably 2-aminoterephthalic acid; The aromatic tetracarboxylic dianhydride is selected from 1,4,5,8-naphthalenetetracarboxylic anhydride, pyromellitic dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride, preferably from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, and more preferably from pyromellitic dianhydride.

3. A method for preparing the Zr-MOF / imide polymer composite material according to claim 1 or 2, comprising the following steps: i) React the Zr source with an aromatic dicarboxylic acid as an organic ligand to obtain Zr-MOF; ii) React melamine with aromatic tetracarboxylic acid dianhydride to obtain a precursor solution; iii) Mix the Zr-MOF with the precursor solution to obtain a Zr-MOF / precursor mixed solution; and iv) Heating the Zr-MOF / precursor mixed solution yields a Zr-MOF / imide polymer composite material.

4. The method according to claim 3, wherein, The aromatic dicarboxylic acid is selected from terephthalic acid and 2-aminoterephthalic acid, preferably 2-aminoterephthalic acid; The aromatic tetracarboxylic dianhydride is selected from 1,4,5,8-naphthalenetetracarboxylic anhydride, pyromellitic dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride, preferably from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, and more preferably from pyromellitic dianhydride.

5. The method according to claim 3 or 4, wherein, In step i), the molar ratio of the Zr source (based on Zr atoms) to the aromatic dicarboxylic acid as the organic ligand is 1:(0.5~3), preferably 1:(0.8~2), more preferably 1:(1~1.6); and / or In step ii), the molar ratio of melamine to aromatic tetracarboxylic acid dianhydride is 1:(0.5~5), preferably 1:(1.1~3.3), and more preferably 1:(1.5~2.5).

6. The method according to claim 3 or 4, wherein, In step iii), the mass ratio of the Zr-MOF to the imide polymer obtainable from the precursor solution is 1:(0.1~6), preferably 1:(0.5~5), and more preferably 1:(1~3).

7. The method according to claim 3 or 4, wherein, In step iv), The heating method is to heat to 160-250°C, preferably 185-235°C, more preferably 190-210°C, at a heating rate of 3-12°C / min, preferably 4.5-9.5°C / min, more preferably 7-9°C / min, and hold at that temperature for 0.5-24 hours, preferably 0.8-12 hours, more preferably 1-3 hours.

8. A battery separator comprising the Zr-MOF / imide polymer composite material as described in claim 1 or 2, or the Zr-MOF / imide polymer composite material prepared by any one of claims 3-7.

9. The battery separator according to claim 8, further comprising a conductive agent selected from conductive carbon black, carbon nanotubes, graphene and acetylene black, preferably carbon nanotubes.

10. The battery separator according to claim 9, wherein, The content of the Zr-MOF / imide polymer composite material is 100 parts by weight; The conductive agent is present in a content of 5-100 parts by weight, preferably 10-70 parts by weight, and more preferably 15-45 parts by weight.

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