Lithium ion battery diaphragm with high heat resistance and high ionic conductivity and preparation method thereof

Abstract

The invention relates to the technical field of battery diaphragms, and discloses a lithium ion battery diaphragm with high heat resistance and high ionic conductivity and a preparation method thereof. The preparation method comprises the following steps: preparing modified dioxythiophene from divinyl ether and dioxythiophene chloride; the preparation method comprises the following steps: preparing an auxiliary agent from polyvinylidene fluoride, MIL-101-F, 1-octadecene and maleic anhydride, adding the auxiliary agent into slurry containing polyvinylidene fluoride and an MIL-101-F material, uniformly mixing, coating a polyethylene diaphragm with the mixture, and drying to obtain the lithium ion battery diaphragm. Wherein the additive can improve the interface performance between the polyvinylidene fluoride and the polyethylene diaphragm; and the performances such as heat resistance and ionic conductivity of the lithium ion battery diaphragm can be enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separators, and specifically relates to a high heat-resistant and high ionic conductivity lithium-ion battery separator and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are the main power sources for electric vehicles, smartphones, and laptops, and are also an integral part of energy storage systems, renewable energy production, and grid balancing; lithium-ion batteries include a positive electrode, a negative electrode, an electrolyte, a separator, and a casing.

[0003] Among the above components, the separator is crucial for the cycle life and safety of the battery; the main function of the separator is to isolate the positive electrode and the negative electrode to prevent short circuits; at the same time, it allows lithium ions to pass through and maintains the electrochemical balance inside the battery, thus ensuring safety and performance; however, traditional commercial separators have problems such as high interfacial impedance, poor thermal stability, low wettability, and easy short circuits, which can lead to serious safety problems in severe cases.

[0004] In summary, it is of great significance to prepare a high heat-resistant and high ionic conductivity lithium-ion battery separator. Summary of the Invention

[0005] The purpose of the present invention is to provide a high heat-resistant and high ionic conductivity lithium-ion battery separator and a preparation method thereof to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A preparation method of a high heat-resistant and high ionic conductivity lithium-ion battery separator includes the following operating steps:

[0008] S1: Add polyvinylidene fluoride to N-methyl-2-pyrrolidone and mix evenly, then add MIL-101-F material and mix evenly to obtain a slurry.

[0009] S2: Coat the slurry on both sides of a polyethylene film and dry it at 60 - 65 °C for 40 - 48 hours to obtain a lithium-ion battery separator.

[0010] Preferably, the raw materials of the slurry include the following components: by mass, 10 - 12 parts of polyvinylidene fluoride, 60 - 65 parts of N-methyl-2-pyrrolidone, and 25 - 30 parts of MIL-101-F material.

[0011] In the solution, a separator with excellent heat resistance and high ionic conductivity is crucial for the charge and discharge performance and safety of lithium-ion batteries. By introducing MIL-101-F material with excellent thermal stability, high hydrophilicity and high ionic conductivity, it can help the polyethylene separator achieve higher heat resistance and high ionic conductivity, contributing to the development of efficient and stable lithium-ion power batteries.

[0012] Preferably, the thickness of the polyethylene base film is 5 - 7 μm, and the thickness of the slurry on each side of the polyethylene base film is 1 - 2 μm.

[0013] Preferably, the preparation method of the MIL-101-F material is as follows: Add Cr(NO 3 ) 3 ·9H 2 O and tetrafluoroterephthalic acid into deionized water and mix evenly, add hydrofluoric acid, and ultrasonic for 30 - 40 minutes to obtain a mixture; Keep the mixture at 200 - 220 °C for 7 - 8 hours, centrifuge after cooling to room temperature, wash and dry to obtain the MIL-101-F material.

[0014] Preferably, in the mixture, the mass ratio of Cr(NO 3 ) 3 ·9H 2 O to tetrafluoroterephthalic acid is (2.3 - 2.8):1.

[0015] Preferably, the slurry also includes an auxiliary agent; its preparation method is: (1) Add divinyl ether, dichlorodioxythiophene, bis(triphenylphosphine)palladium dichloride, and anhydrous potassium carbonate into N,N-dimethylformamide, mix evenly, and react at 100 - 110 °C for 40 - 45 hours under nitrogen protection, cool to room temperature, purify and dry to obtain modified dioxythiophene; (2) Add 1-octadecene into toluene, under nitrogen atmosphere, add modified dioxythiophene and maleic anhydride, mix evenly, add initiator AIBN, and heat up to 60 - 70 °C to react for 2 - 4 hours to obtain the auxiliary agent.

[0016] Preferably, the raw materials of the slurry include the following components: by mass, 10 - 12 parts of polyvinylidene fluoride, 60 - 65 parts of N-methyl-2-pyrrolidone, 25 - 30 parts of MIL-101-F material, and 2 - 5 parts of auxiliary agent.

[0017] Preferably, the raw materials of the modified dimethyloxythiophene include the following components: by mass, 2.5 - 3 parts of dichlorodioxythiophene, 1 - 1.2 parts of divinyl ether, 0.1 - 0.2 parts of bis(triphenylphosphine)palladium dichloride, 2 - 3 parts of anhydrous potassium carbonate, and 20 - 30 parts of N,N-dimethylformamide.

[0018] Preferably, the raw materials of the auxiliary agent include the following components: by mass, 1.5 - 2.5 parts of 1-octadecene, 1 - 2 parts of maleic anhydride, 0.2 - 0.3 parts of modified dioxythiophene, 0.01 - 0.02 parts of initiator AIBN, and 20 - 30 parts of toluene.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] In the present invention, polyvinylidene fluoride and MIL-101 material are added to N-methyl-2-pyrrolidone and uniformly mixed to form a slurry; then the slurry is coated on both sides of a polyethylene substrate and dried to obtain a lithium-ion battery separator.

[0021] In the solution, the MIL-101 material belongs to MOFs materials (metal-organic frameworks), which have high porosity, large specific surface area, high thermal stability, three-dimensional ordered channels, and abundant active sites. Therefore, the MOFs materials can improve the thermal stability and electrolyte affinity of the separator.

[0022] In order to improve the performance of the separator, in the present invention, fluorine groups are introduced on the surface of MIL-101; the chemical bond strength of the fluorine groups is high, with strong electronegativity and polarizability, which is beneficial to the thermal stability and electrolyte wettability of the separator. At the same time, it can effectively reduce the ion transfer resistance, overcome the disadvantages of low ionic conductivity and poor heat resistance of the existing PE separator, and thus greatly improve the ionic conductivity of the separator and enhance the safety performance of the battery.

[0023] In the present invention, the slurry is directly coated on the substrate for drying, which is simple in operation, but there is a problem of poor interfacial performance between polyvinylidene fluoride and the polyethylene substrate; therefore, in the solution, an auxiliary agent is further added to the slurry.

[0024] In the solution, the auxiliary agent is obtained by double-bond polymerization of 1-octadecene, maleic anhydride, and modified dioxythiophene under certain conditions; it has amphiphilic characteristics, containing both polar groups (anhydride groups) that are affinity with polyvinylidene fluoride and non-polar long-chain olefin segments that are affinity with the polyethylene film; during the mixing process, the auxiliary agent can be uniformly mixed with polyvinylidene fluoride, enabling various groups and segments in the polymerization product to be evenly distributed in the slurry system; when coated on the polyethylene film and dried, the long-chain olefin segments of the auxiliary agent interpenetrate and entangle with the molecular chains of the polyethylene film, which can improve the interfacial bonding force between the amphiphilic polymer and the polyethylene film, thereby making the connection between polyvinylidene fluoride and polyethylene more firm, and further improving the wettability of the separator.

[0025] The present invention aims to improve the thermal shrinkage and ionic conductivity of battery separators. In the solution, a modified dioxythiophene is introduced into the additive. It is obtained by reacting the vinyl group on divinyl ether with the halogen on dichlorodioxythiophene. There is an ether oxygen unit on divinyl ether, but the number of ether oxygen units in the modified dioxythiophene is too small to better promote the migration of lithium ions. Therefore, in the solution, it is polymerized with other double-bond polymers to increase the number of ether oxygen units, which is beneficial to promoting the migration of lithium ions. The additive containing a thiophene structure is conducive to the transmission of ions inside the polymer. It can increase the migration rate of ions by means of the conjugated structure of thiophene, thereby improving the ionic conductivity of the separator. The introduction of thiophene groups can change the segment structure and properties of the polymer, making the polymer segments have better flexibility and mobility, providing more transmission paths and vacancies for ions, promoting the diffusion and conduction of ions, and increasing the ionic conductivity. Detailed implementation mode

[0026] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0027] The preparation method of dichlorodioxythiophene (EDOT-Cl) is as follows: 4.8 g of 3,4-ethylenedioxythiophene, 14.4 g of chloro-1,2-propanediol, and 1.2 g of p-toluenesulfonic acid hydrate are added to 100 mL of toluene, uniformly mixed, reacted at 95 °C for 20 hours, cooled to room temperature, and purified to obtain dichlorodioxythiophene (EDOT-Cl).

[0028] Example 1: A preparation method of a high heat-resistant and high ionic conductivity lithium-ion battery separator, including the following operating steps;

[0029] S1: (1) Dissolve 5.0 g of Cr(NO 3 ) 3 ·9H 2 O and 2.1 g of terephthalic acid in 50 mL of deionized water. Add 1 mL of hydrofluoric acid during stirring, ultrasonically treat for 30 minutes, then transfer the mixture to a polytetrafluoroethylene reaction kettle, place it in an oven at 220 °C for heat preservation for 8 hours, cool to room temperature and then centrifuge, wash alternately with hot dimethylformamide (DMF) and absolute ethanol 4 times, and dry at 70 °C for 12 hours to obtain purified MIL-101 material;

[0030] (2) Add 5 parts of polyvinylidene fluoride to 45 parts of N-methyl-2-pyrrolidone and mix evenly, then add 50 parts of MIL-101 material and mix evenly to obtain a slurry.

[0031] S2: Coat the slurry on both sides of a polyethylene film (with a thickness of 7 μm), with a slurry thickness of 2 μm on each side of the polyethylene film, and dry at 60 °C for 48 hours to obtain a lithium-ion battery separator.

[0032] Example 2: A preparation method of a lithium-ion battery separator with high heat resistance and high ionic conductivity, comprising the following operating steps;

[0033] S1: (1) Dissolve 5.0 g of Cr(NO 3 ) 3 ·9H 2 O and 1.8 g of tetrafluoroterephthalic acid in 50 mL of deionized water. Add 1 mL of hydrofluoric acid during stirring. After ultrasonic treatment for 30 minutes, transfer the mixture to a polytetrafluoroethylene reaction kettle, place it in an oven at 220 °C and keep it warm for 8 hours. After cooling to room temperature, centrifuge, wash alternately with hot dimethylformamide (DMF) and absolute ethanol 4 times, and dry at 70 °C for 12 hours to obtain purified MIL-101-F material;

[0034] (2) Add 10 parts of polyvinylidene fluoride to 60 parts of N-methyl-2-pyrrolidone and mix evenly, then add 30 parts of MIL-101-F material and mix evenly to obtain a slurry.

[0035] S2: Coat the slurry on both sides of a polyethylene film (with a thickness of 7 μm), with a slurry thickness of 2 μm on each side of the polyethylene film, and dry at 60 °C for 48 hours to obtain a lithium-ion battery separator.

[0036] Example 3 is based on Example 2: The difference is that 2.2 parts of an auxiliary agent are added to the slurry;

[0037] S1: (1) Dissolve 5.0 g of Cr(NO 3 ) 3 ·9H 2 O and 1.8 g of tetrafluoroterephthalic acid in 50 mL of deionized water. Add 1 mL of hydrofluoric acid during stirring. After ultrasonic treatment for 30 minutes, transfer the mixture to a polytetrafluoroethylene reaction kettle, place it in an oven at 220 °C and keep it warm for 8 hours. After cooling to room temperature, centrifuge, wash alternately with hot dimethylformamide (DMF) and absolute ethanol 4 times, and dry at 70 °C for 12 hours to obtain purified MIL-101-F material;

[0038] (2) Add 1.2 parts of divinyl ether, 2.5 parts of dioxythiophene dichloride, 0.1 part of bis(triphenylphosphine)palladium dichloride, and 2.2 parts of anhydrous potassium carbonate to 25 parts of N,N-dimethylformamide, mix evenly, react at 100 °C for 40 hours under nitrogen protection, cool to room temperature, purify and dry to obtain modified dioxythiophene; (3) Add 1.7 parts of 1-octadecene to 30 parts of toluene, under a nitrogen atmosphere, add 0.4 part of modified dioxythiophene and 1.5 parts of maleic anhydride, mix evenly, add 0.013 part of initiator AIBN, heat to 70 °C and react for 3.2 hours to obtain an auxiliary agent;

[0039] (4) Add 10 parts of polyvinylidene fluoride to 60 parts of N-methyl-2-pyrrolidone and mix evenly, then add 30 parts of MIL-101-F material and 2.2 parts of auxiliary agent and mix evenly to obtain a slurry;

[0040] S2: Coat the slurry on both sides of a polyethylene film (with a thickness of 7 μm), with a slurry thickness of 2 μm on each side of the polyethylene film, and dry at 60 °C for 48 hours to obtain a lithium-ion battery separator.

[0041] Comparative Example 1 is based on Example 2, the difference being that the slurry contains 70 parts of N-methyl-2-pyrrolidone and 20 parts of MIL-101-F;

[0042] S1: (1) Dissolve 5.0 g of Cr(NO 3 ) 3 ·9H 2 O and 1.8 g of tetrafluoroterephthalic acid in 50 mL of deionized water, add 1 mL of hydrofluoric acid during stirring, after ultrasonic treatment for 30 minutes, transfer the mixture to a polytetrafluoroethylene reaction kettle, place it in an oven at 220 °C and keep warm for 8 hours, cool to room temperature and then centrifuge, wash alternately with hot dimethylformamide (DMF) and anhydrous ethanol 4 times, and dry at 70 °C for 12 hours to obtain a purified MIL-101-F material;

[0043] (2) Add 10 parts of polyvinylidene fluoride to 70 parts of N-methyl-2-pyrrolidone and mix evenly, then add 20 parts of MIL-101-F material and mix evenly to obtain a slurry;

[0044] S2: Coat the slurry on both sides of a polyethylene film (with a thickness of 7 μm), with a slurry thickness of 2 μm on each side of the polyethylene film, and dry at 60 °C for 48 hours to obtain a lithium-ion battery separator.

[0045] Comparative Example 2 is based on Example 2, the difference being that the slurry contains 80 parts of N-methyl-2-pyrrolidone and 10 parts of MIL-101-F;

[0046] S1: (1) Dissolve 5.0 g of Cr(NO 3 )3 ·9H 2 O, 1.8 g of tetrafluoroterephthalic acid was dissolved in 50 mL of deionized water. During stirring, 1 mL of hydrofluoric acid was added. After ultrasonic treatment for 30 minutes, the mixture was transferred to a polytetrafluoroethylene reaction kettle and placed in an oven at 220 °C for heat preservation for 8 hours. After cooling to room temperature, it was centrifuged, washed alternately with hot dimethylformamide (DMF) and absolute ethanol 4 times, and dried at 70 °C for 12 hours to obtain purified MIL-101-F material;

[0047] (2) 10 parts of polyvinylidene fluoride were added to 80 parts of N-methyl-2-pyrrolidone and mixed evenly, and then 10 parts of MIL-101-F material were added and mixed evenly to obtain a slurry;

[0048] S2: The slurry was coated on both sides of a polyethylene film (with a thickness of 7 μm), and the thickness of the slurry on each side of the polyethylene film was 2 μm, and dried at 60 °C for 48 hours to obtain a lithium-ion battery separator.

[0049] Comparative Example 3 was based on Example 3, and 1-octadecene was not introduced;

[0050] S1: (1) 5.0 g of Cr(NO 3 ) 3 ·9H 2 O, 1.8 g of tetrafluoroterephthalic acid was dissolved in 50 mL of deionized water. During stirring, 1 mL of hydrofluoric acid was added. After ultrasonic treatment for 30 minutes, the mixture was transferred to a polytetrafluoroethylene reaction kettle and placed in an oven at 220 °C for heat preservation for 8 hours. After cooling to room temperature, it was centrifuged, washed alternately with hot dimethylformamide (DMF) and absolute ethanol 4 times, and dried at 70 °C for 12 hours to obtain purified MIL-101-F material;

[0051] (2) 1.2 parts of divinyl ether, 2.5 parts of dioxythiophene dichloride, 0.1 part of bis(triphenylphosphine)palladium dichloride, and 2.2 parts of anhydrous potassium carbonate were added to 25 parts of N,N-dimethylformamide and mixed evenly. Under nitrogen protection, the reaction was carried out at 100 °C for 40 hours, cooled to room temperature, purified and dried to obtain modified dioxythiophene; (3) 1.5 parts of maleic anhydride were added to 30 parts of toluene. Under a nitrogen atmosphere, 0.4 part of modified dioxythiophene was added and mixed evenly, and 0.013 part of initiator AIBN was added. The temperature was raised to 70 °C and the reaction was carried out for 3.2 hours to obtain an auxiliary agent;

[0052] (4) 10 parts of polyvinylidene fluoride were added to 60 parts of N-methyl-2-pyrrolidone and mixed evenly, and then 25 parts of MIL-101-F material and 2.2 parts of auxiliary agent were added and mixed evenly to obtain a slurry;

[0053] S2: Coat the slurry on both sides of a polyethylene film (with a thickness of 7 μm), with a slurry thickness of 2 μm on each side of the polyethylene film, and dry at 60 °C for 48 hours to obtain a lithium-ion battery separator.

[0054] Comparative Example 4 is based on Example 3, with the difference that modified dioxythiophene is not added.

[0055] S1: (1) Dissolve 5.0 g of Cr(NO 3 ) 3 ·9H 2 O and 1.8 g of tetrafluoroterephthalic acid in 50 mL of deionized water. During stirring, add 1 mL of hydrofluoric acid. After ultrasonic treatment for 30 minutes, transfer the mixture to a polytetrafluoroethylene reaction kettle, place it in an oven at 220 °C for heat preservation for 8 hours, cool to room temperature and then centrifuge, wash alternately with hot dimethylformamide (DMF) and absolute ethanol 4 times, and dry at 70 °C for 12 hours to obtain purified MIL-101-F material;

[0056] (2) Add 1.7 parts of 1-octadecene to 30 parts of toluene. Under a nitrogen atmosphere, add 0.4 part of modified dioxythiophene and 1.5 parts of maleic anhydride, mix evenly, add 0.013 part of initiator AIBN, and heat up to 70 °C for reaction for 3.2 hours to obtain an auxiliary agent;

[0057] (4) Add 10 parts of polyvinylidene fluoride to 60 parts of N-methyl-2-pyrrolidone and mix evenly, then add 25 parts of MIL-101-F material and 2.2 parts of auxiliary agent and mix evenly to obtain a slurry;

[0058] S2: Coat the slurry on both sides of a polyethylene film (with a thickness of 7 μm), with a slurry thickness of 2 μm on each side of the polyethylene film, and dry at 60 °C for 48 hours to obtain a lithium-ion battery separator.

[0059] Comparative Example 5: Directly use a commercially available 7-μm polyethylene film as the lithium-ion battery separator.

[0060] Detection test: (1) Thermal shrinkage performance test: Take 3 lithium-ion battery separators prepared in Examples 1 to 3 and Comparative Examples 1 to 5 and place them in an oven at 105 °C for baking for 1 hour, then measure the size change of the separators and calculate the average thermal shrinkage;

[0061] (2) Membrane breakage temperature test: The membrane breakage temperature test is carried out on Examples 1 to 3 and Comparative Examples 1 to 5 by using thermomechanical analysis (TMA). The specific method can refer to NASATM2010-216099;

[0062] (3) Contact angle test: Under the conditions of a temperature of 25 °C and a relative humidity of less than 60%, using a contact angle measuring instrument of model TBU100 (manufactured by Dataphysics Company, Germany), slowly drip the EC / DMC (v:v = 1:1) mixed solvent onto the surface of the lithium-ion battery separators prepared in Examples 1-3 and Comparative Examples 1-5. After 60 s of dripping, measure the wetting contact angle of the mixed solution. Measure the contact angle at three points on the film, and the average value of the three can be used as the contact angle;

[0063] (4) Liquid absorption rate test (EU): Cut the lithium-ion battery separators of Examples 1-3 and Comparative Examples 1-5 into circular separators with a diameter of 19 mm; weigh the initial mass W0 after sufficient drying under vacuum conditions, then immerse the film in the EC / DMC (v:v = 1:1) mixed solvent for 24 h, take out the separator, dry the electrolyte on the film surface and weigh the mass wi, and then calculate the liquid absorption rate (EU) according to the following formula;

[0064]

[0065] (5) Ionic conductivity: Use an electrochemical workstation to measure the ionic conductivity of the lithium-ion battery separators of Examples 1-3 and Comparative Examples 1-4. The test frequency range is 0.001 Hz - 105 Hz, and then calculate the conductivity (σ) according to the formula: σ = d / RbA, where σ is the conductivity of the separator, d is the thickness of the separator, Rb is the bulk resistance of the separator, and A is the effective area of contact between the separator and the electrode.

[0066]

[0067] Comparative Example 2 11.1 1.0 0.40 174 26.4° 200.8 0.46 Comparative Example 3 11.3 0.65 0.25 196 18.2° 221.8 0.62 Comparative Example 4 11.3 0.68 0.28 192 16.8° 224.7 0.53 Comparative Example 5 7.0 2.60 1.50 143 50.3° 68.5 0.23

[0068] Table 1

[0069] Conclusion: As can be seen from Table 1, compared with the thermal shrinkage and film rupture temperature (143 °C) of the untreated PE separator (Comparative Example 5), the thermal shrinkage and film rupture temperature of the separators added with MIL-101 material and MIL-101-F material (Examples 1-2 and Comparative Examples 1-2) have been greatly improved. Especially for Comparative Example 2, the film rupture temperature of Comparative Example 2 reached 188 °C, which is 45 °C higher than the film rupture temperature of the commercial separator (Comparative Example 5). This is mainly due to the high thermal stability and high temperature resistance of the MOFs material.

[0070] The wettability of the separator to the electrolyte and the absorption of the electrolyte are also crucial for the battery. The contact angle of the electrolyte in Comparative Example 5 is 50.3°, and the liquid absorption rate is 68.5%. After adding MIL-101 and fluorinated MIL-101-F, the contact angle is reduced to about 20-30°, especially the contact angle of Example 2 reaches 18.7°. The liquid absorption rates of Examples 1-2 and Comparative Examples 1-2 are significantly improved compared with Comparative Example 5. This is mainly due to the better wettability of the separator by the hydrophilicity of the -F bond after fluorination, which can effectively reduce the ion transfer resistance and improve the rate performance.

[0071] The increase in ionic conductivity is due to the better electrolyte wettability and porous structure of MOFs, which can promote ion transport; in addition, the negatively charged functional group (-F) can accelerate the transport of Li + transport and inhibit the free migration of anions, resulting in a greater Li+ transfer rate; the ionic conductivity of Comparative Example 5 without MIL-101-F is only 0.23 mS / cm.

[0072] The study found that introducing an additive into the slurry of Example 3 can effectively improve the performance of the lithium-ion battery separator; Comparative Example 3 is based on Example 3 without introducing 1-octadecene, resulting in a decrease in the performance of the lithium-ion battery separator because the additive containing 1-octadecene can improve the interfacial performance between polyvinylidene fluoride and the polyethylene separator, thus facilitating the improvement of the separator performance; Comparative Example 4 is based on Example 3, with the difference that modified dioxythiophene is not added, resulting in a decrease in the performance of the lithium-ion battery separator; because the modified dioxythiophene contains ether oxygen units and thiophene structures, which can polymerize with other compounds to increase the content of ether oxygen units, thus facilitating the migration of lithium ions; the thiophene structure makes the polymer chain segments have better flexibility and mobility, providing more transport paths and vacancies for ions, promoting ion diffusion and conduction, and increasing ionic conductivity.

[0073] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A method for preparing a lithium ion battery separator with high heat resistance and high ionic conductivity, characterized in that: The steps include: S1: adding polyvinylidene fluoride to N-methyl-2-pyrrolidone and mixing evenly, then adding MIL-101-F material and mixing evenly to obtain slurry; S2: The slurry is coated on both sides of the polyethylene base film, and dried at 60-65° C. for 40-48 hours to obtain a lithium ion battery separator.

2. The method for preparing a lithium ion battery separator with high heat resistance and high ionic conductivity according to claim 1, characterized in that: The raw materials of the slurry include the following components: by mass, 10 to 12 parts of polyvinylidene fluoride, 60 to 65 parts of N-methyl-2-pyrrolidone, and 25 to 30 parts of MIL-101-F material.

3. The method for preparing a lithium ion battery separator with high heat resistance and high ionic conductivity according to claim 1, characterized in that: The thickness of the polyethylene-based film is 4 to 7 μm, and the thickness of the slurry on each side of the polyethylene-based film is 1 to 2 μm.

4. The method for preparing a lithium ion battery separator with high heat resistance and high ionic conductivity according to claim 1, characterized in that: The preparation method of the MIL-101-F material is as follows: Cr(NO3)3·9H2O and tetrafluoroterephthalic acid are added to deionized water and mixed evenly, hydrofluoric acid is added, and ultrasonication is performed for 30 to 40 minutes to obtain a mixture; the mixture is kept at 200 to 220°C for 7 to 8 hours, cooled to room temperature, centrifuged, washed, and dried to obtain the MIL-101-F material.

5. The method for preparing a lithium ion battery separator with high heat resistance and high ionic conductivity according to claim 4, characterized in that: In the mixture, the mass ratio of Cr(NO3)3·9H2O to tetrafluoroterephthalic acid is (2.3-2.8):

1.

6. The method for preparing a lithium ion battery separator with high heat resistance and high ionic conductivity according to claim 1, characterized in that: The slurry also includes an auxiliary agent; the preparation method thereof is as follows: (1) adding divinyl ether, chlorinated dioxythiophene, bistriphenylphosphine palladium dichloride, and anhydrous potassium carbonate to N,N-dimethylformamide, uniformly mixing, reacting at 100-110° C. for 40-45 hours under nitrogen protection, cooling to room temperature, purifying and drying to obtain modified dioxythiophene; (2) adding 1-octadecene to toluene, adding modified dioxythiophene and maleic anhydride under nitrogen atmosphere, uniformly mixing, adding initiator AIBN, heating to 60-70° C. for reaction for 2-4 hours to obtain the auxiliary agent.

7. The method for preparing a lithium-ion battery separator with high heat resistance and high ionic conductivity according to claim 6, characterized in that: The raw materials of the slurry include the following components: by mass, 10 to 12 parts of polyvinylidene fluoride, 60 to 65 parts of N-methyl-2-pyrrolidone, 25 to 30 parts of MIL-101-F material, and 2 to 5 parts of auxiliary agent.

8. The method for preparing a lithium-ion battery separator with high heat resistance and high ionic conductivity according to claim 6, characterized in that: The raw materials of the modified dioxythiophene include the following components: by mass, 2.5 to 3 parts of chlorinated dioxythiophene, 1 to 1.2 parts of divinyl ether, 0.1 to 0.2 parts of bistriphenylphosphine palladium dichloride, 2 to 3 parts of anhydrous potassium carbonate, and 20 to 30 parts of N,N-dimethylformamide.

9. The method for preparing a lithium-ion battery separator with high heat resistance and high ionic conductivity according to claim 6, characterized in that: The raw materials of the auxiliary agent include the following components: by mass, 1.5-2.5 parts of 1-octadecene, 1-2 parts of maleic anhydride, 0.2-0.3 parts of modified dioxythiophene, 0.01-0.02 parts of initiator AIBN, and 20-30 parts of toluene.

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