High-temperature-resistant lithium ion battery diaphragm with high ionic conductivity and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant lithium ion battery diaphragm with high ionic conductivity and a preparation method of the high-temperature-resistant lithium ion battery diaphragm, belongs to the technical field of battery diaphragms, and is used for solving the technical problem that the high-temperature resistance and the ionic conductivity of a lithium ion battery diaphragm in the prior art need to be further improved. The invention relates to a preparation method of a high-temperature-resistant lithium ion battery diaphragm with high ionic conductivity, which comprises the following steps: dissolving polyphthalamide and modified cellulose into an N, N-dimethylacetamide solution to form a spinning solution, and then preparing a spinning base membrane with the thickness of 29-31mu m by adopting electrostatic spinning. According to the preparation method disclosed by the invention, the polyphthalamide and the modified cellulose are taken as raw materials for electrostatic spinning, triazine modification is performed on the raw materials, and coating is performed by adopting the inorganic coating liquid, so that not only are the mechanical strength and the heat-resistant stability of the battery diaphragm effectively improved, but also the ionic conductivity of the battery diaphragm is improved, and the charge-discharge efficiency of a lithium battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separator processing, and in particular to a high-temperature-resistant lithium-ion battery separator with high ionic conductivity and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are efficient and environmentally friendly energy storage devices. In recent years, with the continuous improvement of the requirements for energy density, safety and cycle life of lithium-ion batteries in new energy vehicles, energy storage systems and consumer electronics, the separator, as one of the key components of the battery, mainly separates the positive and negative electrodes to prevent internal short circuits in the battery, while allowing lithium ions to pass freely during the charging and discharging process. Its performance directly affects key indicators such as battery capacity, cycle life, and safety performance.

[0003] Lithium-ion batteries in the existing technology will generate a certain amount of heat during the charging and discharging process, especially when used in a high-temperature environment, the temperature inside the battery will rise sharply. Traditional polyolefin separators have poor thermal stability and are prone to thermal shrinkage or even melting at high temperatures, resulting in direct contact between the positive and negative electrodes, causing internal short circuits in the battery, and then causing safety accidents such as thermal runaway, fire, and even explosion of the battery. In addition, although traditional polyolefin separators have good mechanical properties and chemical stability, due to the characteristics of the material itself, they have poor affinity for electrolytes and low porosity, resulting in greater migration resistance of lithium ions in the separator and lower ionic conductivity, making the battery prone to polarization during high-rate charging and discharging, reducing battery performance and life.

[0004] In view of the technical defects in this aspect, a solution is now proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-ionic conductivity, high-temperature resistant lithium-ion battery separator and a preparation method thereof, so as to solve the technical problem in the prior art that the high-temperature resistance and ionic conductivity of lithium-ion battery separators need to be further improved.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity comprises the following steps: S1, dissolving polyphthalamide and modified cellulose in N,N-dimethylacetamide solution to form a spinning solution, and then performing electrospinning to prepare a spinning base membrane with a thickness of 29-31 μm; S2, immersing the spinning base membrane in the modification liquid to perform immersion modification on the spinning base membrane, forming a triazine-modified intermediate layer on the spinning base membrane, and preparing a modified spinning base membrane; S3. Coating a coating liquid composed of an inorganic material on both sides of the modified spinning base membrane, and then rolling and compacting it after solidification to prepare a battery separator.

[0007] Furthermore, in step S1, the spinning base membrane is obtained by processing the following steps: A1. Mix polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution, raise the temperature of the reaction system to 75-85°C, stir until the system is dissolved, and allow to stand for degassing to obtain a spinning solution; A2. The spinning solution is electrospun by electrospinning to prepare a spinning base membrane with a thickness of 29-31 μm.

[0008] Furthermore, in step A1, the amount ratio of the polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution is 1g:0.1g:9mL, and the N,N-dimethylacetamide solution is composed of N,N-dimethylacetamide and lithium chloride at 100mL:7g; in step A2, the humidity of the electrospinning environment is 10-30%, the temperature is 30-40°C, the propulsion speed of the spinning solution is 1mL / h, the receiving distance is 26-28cm, and the spinning voltage is 15kV. After spinning is completed, the spinning base membrane is transferred to purified water at a temperature of 60-70°C, soaked for 30-50min, washed 3 times with purified water and drained, and then transferred to a drying oven at a temperature of 60-70°C, dried to constant weight, to obtain a spinning base membrane.

[0009] Furthermore, the preparation method of modified cellulose is as follows: cellulose and alkali solution are added to a reaction system and stirred and mixed, the temperature of the reaction system is increased to 50-60°C, stirred until the system is dissolved, dodecyl glycidyl ether solution is added to the reaction system, the reaction is kept warm for 60-80 minutes, and post-processed to obtain modified cellulose.

[0010] Furthermore, the amount ratio of the cellulose, alkali solution, and dodecyl glycidyl ether solution is 5-6 g:20-30 mL:10-13 g, the alkali solution is a 2-3 mol / L sodium hydroxide solution, and the dodecyl glycidyl ether solution is composed of dodecyl glycidyl ether and N,N-dimethylformamide at a ratio of 1 g:10 mL. The post-treatment includes: after the reaction is completed, lowering the temperature of the reaction system to room temperature, adding anhydrous ethanol to the reaction system, filtering, washing the filter cake with anhydrous ethanol three times and then drying it, transferring the filter cake to a drying oven at a temperature of 60-70° C., and drying to constant weight to obtain modified cellulose.

[0011] The synthetic reaction mechanism of modified cellulose is:

[0012] Where, It is the simple form of cellulose; During the reaction, under an alkaline environment, the hydroxyl groups on the cellulose undergo ring-opening condensation with the epoxy groups on the dodecyl glycidyl ether molecules to form a chemical modification, forming dodecyl glycidyl ether modification on the cellulose to prepare modified cellulose.

[0013] Furthermore, in step S2, the preparation method of the modified spinning base membrane is: mixing melamine and N,N-dimethylformamide, raising the temperature of the reaction system to 55-65°C, stirring until the system is dissolved, adding 3-isocyanatepropyltrimethoxysilane to the reaction system, keeping the reaction warm for 50-60 minutes, adding dilute acid to the reaction system, stirring for 10-15 minutes, and obtaining a modified liquid; immersing the spinning base membrane in the modified liquid, keeping it completely immersed for 40-60 minutes, and post-treating it to obtain a modified spinning base membrane.

[0014] The synthetic reaction mechanism of the modified spinning base membrane is:

[0015] During the reaction process, the isocyanate group on the 3-isocyanatepropyltrimethoxysilane molecule condenses with the amino group on the melamine molecule to form a trimethoxysilane modification on the triazine molecular ring. Then, under the catalytic action of dilute acid, the trimethoxysilane molecule is hydrolyzed to form silanol to prepare a modified liquid. After the spinning base membrane is immersed in the modified liquid, the silanol on the modified liquid molecule chemically bonds with the active functional groups on the surface of the spinning base membrane to form a triazine modification on the spinning base membrane to prepare a modified spinning base membrane.

[0016] Furthermore, the dosage ratio of melamine, N,N-dimethylformamide, 3-isocyanatepropyltrimethoxysilane and dilute acid is 1g:30mL:4.6g:10mL, and the dilute acid is 0.3-0.6mol / L hydrochloric acid; the solid-liquid ratio of the spinning base membrane and the modified liquid is 1:7-8, and the post-treatment includes: after the reaction is completed, the spinning base membrane is removed from the modified liquid, washed with purified water until neutral and then drained, and the spinning base membrane is transferred to a drying oven at a temperature of 70-80°C, dried to constant weight, and obtained a modified spinning base membrane.

[0017] Furthermore, the coating liquid is prepared by mixing boehmite, mica powder and purified water, stirring at room temperature for 4-6 hours to obtain a mixed liquid, adding KH-560 to the mixed liquid, stirring for 10-20 minutes, adding the mixed liquid to a high-pressure homogenizer, homogenizing and mixing, adding a binder to the solution, stirring and mixing for 30-50 minutes, and obtaining a coating liquid.

[0018] The synthetic reaction mechanism of the coating liquid is: During the reaction process, boehmite and mica powder are mixed, and the surface of the inorganic particles is modified with a silane coupling agent KH-560 to form an epoxy polysiloxane coating on the particles. The particles are then homogenized and mixed with a binder to prepare a coating liquid.

[0019] Furthermore, the usage ratio of the boehmite, mica powder, purified water, KH-560 and binder is 5-6g:3-4g:50mL:0.6-0.8g:1-1.2g, the binder is lithiated polyacrylic acid, the homogenization pressure of the high-pressure homogenizer is 130-150MPa, and the homogenization times are 10 times.

[0020] Furthermore, the forming method of the battery separator is as follows: the coating liquid is applied on one side at a rate of 20-30 mL / m 2 The crude battery separator is evenly coated on both sides of the modified spinning base membrane and then dried to prepare the crude battery separator. The crude battery separator is added to a roller press, the roller pressing temperature is set to 65-75°C, and roller pressing is performed to obtain a battery separator with a thickness of 26-28 μm.

[0021] A high-ionic conductivity, high-temperature-resistant lithium-ion battery separator is prepared by a method for preparing a high-ionic conductivity, high-temperature-resistant lithium-ion battery separator.

[0022] The present invention has the following beneficial effects: 1. The high-ionic conductivity, high-temperature resistant lithium-ion battery separator of the present invention is prepared by using polyphthalamide and modified cellulose as raw materials, dissolving them in N,N-dimethylacetamide solution to form a spinning solution, and then electrospinning to prepare a spinning base membrane. A triazine modification layer is then modified on the base membrane, and then surface coating modification is performed using a coating solution composed of boehmite and mica powder to form a reinforcing coating on the surface to prepare a battery separator; by modifying the cellulose, its intermolecular compatibility with polyphthalamide is improved, and by electrospinning, a three-dimensional fiber network interlocking structure is constructed, and the fibers synergistically deform under external force to disperse stress, thereby improving the mechanical strength of the spinning base membrane. During electrospinning, low-humidity spinning is adopted to form micropores on the fiber surface, thereby improving the porosity of the spinning base membrane. The high porosity provides more ion channels, thereby improving the ionic conductivity of the spinning base membrane.

[0023] 2. The high-ionic conductivity, high-temperature resistant lithium-ion battery separator of the present invention uses polyphthalamide as the main film-forming matrix, which itself has good mechanical strength, heat resistance and dimensional stability. The epoxy group of dodecyl glycidyl ether reacts with the hydroxyl group of cellulose to graft long-chain alkyl groups, reduce the hydrophilicity of cellulose, and transform its surface energy from polar to non-polar, which better matches the hydrophobic properties of polyphthalamide. At the same time, the residual hydroxyl groups form hydrogen bonds with the amide bonds of polyphthalamide, thereby enhancing the interfacial adhesion and improving the compatibility of modified cellulose with polyphthalamide. In addition, N,N-dimethylacetamide is a good solvent for polyphthalamide. The addition of LiCl helps to destroy the hydrogen bonds between modified cellulose molecules and promotes the uniform dispersion of modified cellulose in the polyphthalamide solution, thereby constructing a three-dimensional network crosslinking between molecules. In addition, dodecyl glycidyl ether introduces long-chain hydrophobic groups, reduces the number of cellulose hydroxyl groups, reduces the hydrophilicity of the separator, avoids excessive swelling of the electrolyte, optimizes the hydrophobic-hydrophilic balance, and is conducive to the formation of lithium ion transmission channels.

[0024] 3. The high-ionic conductivity, high-temperature resistant lithium-ion battery separator of the present invention is modified by impregnating the spinning base membrane with a modifying liquid, which allows the modifier to fully penetrate into the pores of the fiber network, and the silanol on the modifier triazine molecule can chemically bond with the active reaction sites on the surface of the spinning base membrane, thereby enhancing the bonding force between the fibers, thereby greatly improving the ability of the base membrane to resist tensile deformation. Cross-linking makes the entire fiber network more rigid and less prone to local plastic deformation, which is beneficial to resisting puncture. The decomposition temperature of the main body of triazine with melamine is very high, thereby improving the overall heat resistance stability of the base membrane; after the surface of boehmite and mica powder is modified by KH-560, the coating slurry is highly evenly dispersed by homogeneous dispersion, and the modified spinning base membrane is coated and modified by coating. The epoxy groups modified on the surface of the liquid inorganic particles can undergo ring-opening condensation with the imino groups on the modified triazine modifier molecules of the modified spinning base membrane, thereby forming a stable modified layer on the modified spinning base membrane. Boehmite and mica powder are both high-temperature resistant materials. The cross-linked structure further enhances the thermal stability of the coating and reduces high-temperature deformation. The coating layer is then rolled to make it more tightly bonded to the base membrane, thereby improving the overall density and thus enhancing the mechanical strength. Boehmite and mica powder are inorganic particles. The porous structure formed after coating and curing helps to increase the porosity of the diaphragm, thereby increasing the channel for ion transmission. Lithium-containing polyacrylic acid is used as a binder, which not only can bond fillers such as boehmite and mica powder together, but also contains lithium ions and has ionic conductivity, which can further improve the ionic conductivity of the coating layer. DETAILED DESCRIPTION

[0025] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In the present invention, polyphthalamide is selected from Shanghai Changshi Plastics Co., Ltd., model GV-2H, with a tensile modulus of 8200 MPa, a transverse shrinkage of 0.8%, a saturated water absorption of 5% at 23°C, and a volume resistivity of 1×10 14 Ω·cm, ball pressure hardness is 225MPa, brand is Swiss EMS; In the present invention, the cellulose is hydroxymethyl cellulose; In the present invention, KH-560 is γ-glycidyloxypropyltrimethoxysilane, CAS No. 2530-83-8; In the present invention, the lithiated polyacrylic acid is selected from Shenzhen Liyou New Energy Technology Co., Ltd., the model is TOB-PAALi, and the brand is TOB-Liyou.

[0027] Example 1 This embodiment provides a method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity, comprising the following steps: Step 1: Preparation of spinning base membrane N,N-dimethylacetamide and lithium chloride were mixed uniformly at a ratio of 100 mL:7 g to obtain an N,N-dimethylacetamide solution; Dodecyl glycidyl ether and N,N-dimethylformamide were mixed uniformly at a ratio of 1 g:10 mL to obtain a dodecyl glycidyl ether solution; Weigh: 20 g of cellulose and 80 mL of 2 mol / L sodium hydroxide solution are added to a reaction flask and stirred. The temperature of the reaction flask is raised to 50°C and stirred until the system is dissolved. 40 g of dodecyl glycidyl ether solution is added to the reaction flask and the reaction is kept warm for 60 minutes. The temperature of the reaction flask is lowered to room temperature, 500 mL of anhydrous ethanol is added to the reaction flask, and the mixture is filtered. The filter cake is washed three times with anhydrous ethanol and then dried. The filter cake is transferred to a drying oven at 60°C and dried to constant weight to obtain modified cellulose. Add polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution in a ratio of 1 g:0.1 g:9 mL into a reaction flask and stir to mix. Raise the temperature of the reaction flask to 75°C and stir until the system is dissolved. Allow to stand for degassing to obtain a spinning solution. The spinning solution was electrospun by electrospinning, and the electrospinning environment humidity was set to 10%, the temperature was 30°C, the propulsion speed of the spinning solution was 1mL / h, the receiving distance was 13cm, and the spinning voltage was 15kV. After spinning was completed, the spinning base membrane was transferred to purified water at a temperature of 60°C, soaked for 30 minutes, washed with purified water three times and drained, and then transferred to a drying oven at a temperature of 60°C and dried to constant weight to obtain a spinning base membrane with a thickness of 29μm.

[0028] Step 2: Preparation of modified spinning base membrane Weigh: 5 g of melamine and 150 mL of N,N-dimethylformamide are added to a reaction flask and stirred. The temperature of the reaction flask is raised to 55°C and stirred until the system is dissolved. 23 g of 3-isocyanatepropyltrimethoxysilane is added to the reaction flask and the reaction is kept warm for 50 minutes. 50 mL of 0.3 mol / L hydrochloric acid is added to the reaction system and stirred for 10 minutes to obtain a modified solution. The spinning base membrane was completely immersed in the modification liquid at a solid-liquid ratio of 1:7 and kept completely immersed for 40 minutes. The spinning base membrane was removed from the modification liquid, washed with purified water until neutral, and then drained. The spinning base membrane was transferred to a drying oven at a temperature of 70°C and dried to constant weight to obtain a modified spinning base membrane.

[0029] Step 3: Prepare coating solution Weigh: 25 g of boehmite, 15 g of mica powder and 250 mL of purified water, add them to a reaction flask and stir to mix, stir at room temperature for 4 h, add 3 g of KH-560 to the reaction flask, stir for 10 min, and then transfer it to a high-pressure homogenizer, set the homogenization pressure of the high-pressure homogenizer to 130 MPa, the homogenization number of times is 10, and homogenize to mix, add 5 g of binder lithiated polyacrylic acid to the homogenized solution, stir and mix for 30 min to obtain a coating solution.

[0030] Step 4: Prepare battery separator The coating liquid is applied on one side at a rate of 20 mL / m 2 After being evenly coated on both sides of the modified spinning base membrane, it was transferred to a drying oven at a temperature of 80°C and dried to a constant weight to prepare a crude battery separator; The crude battery separator was added to a roller press, the roller pressing temperature was set to 65° C., and the battery separator was compacted by roller pressing to obtain a battery separator with a thickness of 26 μm.

[0031] Example 2 This embodiment provides a method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity, comprising the following steps: Step 1: Preparation of spinning base membrane N,N-dimethylacetamide and lithium chloride were mixed uniformly at a ratio of 100 mL:7 g to obtain an N,N-dimethylacetamide solution; Dodecyl glycidyl ether and N,N-dimethylformamide were mixed uniformly at a ratio of 1 g:10 mL to obtain a dodecyl glycidyl ether solution; Weigh: 22 g of cellulose and 100 mL of 2.5 mol / L sodium hydroxide solution are added to a reaction flask and stirred. The temperature of the reaction flask is raised to 55°C and stirred until the system is dissolved. 46 g of dodecyl glycidyl ether solution is added to the reaction flask and the reaction is kept warm for 70 minutes. The temperature of the reaction flask is lowered to room temperature, and 500 mL of anhydrous ethanol is added to the reaction flask. The filter cake is filtered with anhydrous ethanol three times and then dried. The filter cake is transferred to a drying oven at a temperature of 65°C and dried to constant weight to obtain modified cellulose; Polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution were added to a reaction flask at a ratio of 1 g:0.1 g:9 mL and stirred. The temperature of the reaction flask was raised to 80°C and stirred until the system was dissolved. The mixture was allowed to stand for degassing to obtain a spinning solution. The spinning solution was electrospun by electrospinning, and the electrospinning environment humidity was set to 20%, the temperature was 35°C, the propulsion speed of the spinning solution was 1 mL / h, the receiving distance was 14 cm, and the spinning voltage was 15 kV. After spinning was completed, the spinning base membrane was transferred to purified water at a temperature of 65°C, soaked for 40 minutes, washed with purified water three times and drained, and then transferred to a drying oven at a temperature of 65°C and dried to constant weight to obtain a spinning base membrane with a thickness of 30 μm.

[0032] Step 2: Preparation of modified spinning base membrane Weigh: 5 g of melamine and 150 mL of N,N-dimethylformamide were added to a reaction flask and stirred. The temperature of the reaction flask was raised to 60°C and stirred until the system was dissolved. 23 g of 3-isocyanatepropyltrimethoxysilane was added to the reaction flask and the reaction was kept at this temperature for 55 minutes. 50 mL of 0.45 mol / L hydrochloric acid was added to the reaction system and stirred for 13 minutes to obtain a modified solution. The spinning base membrane was completely immersed in the modification liquid at a solid-liquid ratio of 1:7.5 and kept completely immersed for 50 minutes. The spinning base membrane was removed from the modification liquid, washed with purified water until neutral, and then drained. The spinning base membrane was transferred to a drying oven at a temperature of 75°C and dried to constant weight to obtain a modified spinning base membrane.

[0033] Step 3: Prepare coating solution Weigh: 27 g of boehmite, 17 g of mica powder and 250 mL of purified water, add them to a reaction flask and stir to mix, stir at room temperature for 5 h, add 3.5 g of KH-560 to the reaction flask, stir for 15 min, and then transfer it to a high-pressure homogenizer, set the homogenization pressure of the high-pressure homogenizer to 140 MPa, the homogenization number of times is 10, and homogenize to mix, add 5.5 g of binder lithiated polyacrylic acid to the homogenized solution, stir and mix for 40 min to obtain a coating liquid.

[0034] Step 4: Prepare battery separator The coating liquid is applied on one side at a rate of 25 mL / m 2 After being evenly coated on both sides of the modified spinning base membrane, it was transferred to a drying oven at a temperature of 83°C and dried to a constant weight to prepare a crude battery separator; The crude battery separator was added to a roller press, the roller pressing temperature was set to 70°C, and the battery separator was compacted by roller pressing to obtain a battery separator with a thickness of 27 μm.

[0035] Example 3 This embodiment provides a method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity, comprising the following steps: Step 1: Preparation of spinning base membrane N,N-dimethylacetamide and lithium chloride were mixed uniformly at a ratio of 100 mL:7 g to obtain an N,N-dimethylacetamide solution; Dodecyl glycidyl ether and N,N-dimethylformamide were mixed uniformly at a ratio of 1 g:10 mL to obtain a dodecyl glycidyl ether solution; Weigh: 24 g of cellulose and 120 mL of 3 mol / L sodium hydroxide solution are added to a reaction flask and stirred. The temperature of the reaction flask is raised to 60°C and stirred until the system is dissolved. 52 g of dodecyl glycidyl ether solution is added to the reaction flask and the reaction is kept warm for 80 minutes. The temperature of the reaction flask is lowered to room temperature, and 500 mL of anhydrous ethanol is added to the reaction flask. The filter cake is filtered and washed with anhydrous ethanol three times and then dried. The filter cake is transferred to a drying oven at 70°C and dried to constant weight to obtain modified cellulose; Add polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution in a ratio of 1 g:0.1 g:9 mL into a reaction flask and stir to mix. Raise the temperature of the reaction flask to 85°C and stir until the system is dissolved. Allow to stand for degassing to obtain a spinning solution. The spinning solution was electrospun by electrospinning, and the electrospinning environment humidity was set to 30%, the temperature was 40°C, the propulsion speed of the spinning solution was 1 mL / h, the receiving distance was 15 cm, and the spinning voltage was 15 kV. After spinning was completed, the spinning base membrane was transferred to purified water at a temperature of 70°C, soaked for 50 minutes, washed with purified water three times and drained, and then transferred to a drying oven at a temperature of 70°C and dried to constant weight to obtain a spinning base membrane with a thickness of 31 μm.

[0036] Step 2: Preparation of modified spinning base membrane Weigh: 5 g of melamine and 150 mL of N,N-dimethylformamide are added to a reaction flask and stirred. The temperature of the reaction flask is raised to 65°C and stirred until the system is dissolved. 23 g of 3-isocyanatepropyltrimethoxysilane is added to the reaction flask and the reaction is kept at this temperature for 60 min. 50 mL of 0.6 mol / L hydrochloric acid is added to the reaction system and stirred for 15 min to obtain a modified solution. The spinning base membrane was completely immersed in the modification liquid at a solid-liquid ratio of 1:8 and kept completely immersed for 60 minutes. The spinning base membrane was removed from the modification liquid, washed with purified water until neutral, and then drained. The spinning base membrane was transferred to a drying oven at a temperature of 80°C and dried to constant weight to obtain a modified spinning base membrane.

[0037] Step 3: Prepare coating solution Weigh: 30 g of boehmite, 20 g of mica powder and 250 mL of purified water, add them to a reaction flask and stir to mix, stir at room temperature for 6 h, add 4 g of KH-560 to the reaction flask, stir for 20 min, and then transfer it to a high-pressure homogenizer, set the homogenization pressure of the high-pressure homogenizer to 150 MPa, the homogenization number of times is 10, and homogenize to mix, add 6 g of binder lithiated polyacrylic acid to the homogenized solution, stir and mix for 50 min to obtain a coating solution.

[0038] Step 4: Prepare battery separator The coating liquid is applied on one side at a rate of 30 mL / m 2 After being evenly coated on both sides of the modified spinning base membrane, it was transferred to a drying oven at a temperature of 85°C and dried to a constant weight to prepare a crude battery separator; The crude battery separator was added to a roller press, the roller pressing temperature was set to 75°C, and the battery separator was compacted by roller pressing to obtain a battery separator with a thickness of 28 μm.

[0039] Comparative Example 1 The difference between this comparative example and Example 3 is that, in step 1, cellulose is used instead of modified cellulose when preparing the spinning solution.

[0040] Comparative Example 2 The difference between this comparative example and Example 3 is that step 2 is eliminated, and the modified spinning base membrane in step 4 is replaced by the spinning base membrane in step 1.

[0041] Comparative Example 3 The difference between this comparative example and Example 3 is that in step 3, KH-560 is not added.

[0042] Performance testing: The tensile strength (longitudinal tensile strength of dry biaxial stretching), thermal shrinkage (200°C, 1 h), puncture strength (dry biaxial stretching), and ionic conductivity of the battery separator samples prepared in Examples 1-3 and Comparative Examples 1-3 were measured with reference to the standard GB / T 36363-2018 "Polyolefin Separators for Lithium Ion Batteries"; The specific test results are shown in Table 1 below.

[0043] Table 1-Performance test data of the sample

[0044] Data Analysis: A comparative analysis of the data in Table 1 above shows that the longitudinal tensile strength of the battery separator prepared by the present invention reaches 197.8 MPa, the thermal shrinkage rate at 200°C is reduced to 2.01%, the puncture strength reaches 0.182 N / μm, and the ionic conductivity reaches 1.68 mS / cm. All performance test data are better than those of the comparative example, indicating that the present invention uses polyphthalamide and modified cellulose as raw materials for electrospinning, modifies them with triazine, and then coats them with an inorganic coating liquid, which not only effectively improves the mechanical strength and heat stability of the battery separator, but also improves its ionic conductivity, thereby improving the charge and discharge efficiency of the lithium battery.

[0045] The above contents are merely examples and explanations of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0046] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0047] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity, characterized in that: The following steps are involved: S1, dissolving polyphthalamide and modified cellulose in N,N-dimethylacetamide solution to form a spinning solution, and then performing electrospinning to prepare a spinning base membrane with a thickness of 29-31 μm; S2, immersing the spinning base membrane in the modification liquid to perform immersion modification on the spinning base membrane, forming a triazine-modified intermediate layer on the spinning base membrane, and preparing a modified spinning base membrane; S3. Coating a coating liquid composed of an inorganic material on both sides of the modified spinning base membrane, and then rolling and compacting it after solidification to prepare a battery separator.

2. The method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity according to claim 1, characterized in that: In step S1, the spinning base membrane is obtained by processing the following steps: A1. Mix polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution, raise the temperature of the reaction system to 75-85°C, stir until the system is dissolved, and allow to stand for degassing to obtain a spinning solution; A2. The spinning solution is electrospun by electrospinning to prepare a spinning base membrane with a thickness of 29-31 μm.

3. The method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity according to claim 2, characterized in that: In step A1, the amount ratio of the polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution is 1g:0.1g:9mL, and the N,N-dimethylacetamide solution is composed of N,N-dimethylacetamide and lithium chloride at 100mL:7g; in step A2, the electrospinning environment humidity is 10-30%, the temperature is 30-40°C, the propulsion speed of the spinning solution is 1mL / h, the receiving distance is 26-28cm, and the spinning voltage is 15kV. After spinning is completed, the spinning base membrane is transferred to purified water at a temperature of 60-70°C, soaked for 30-50min, washed with purified water 3 times and drained, and then transferred to a drying oven at a temperature of 60-70°C and dried to constant weight to obtain a spinning base membrane.

4. The method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity according to claim 1, characterized in that: The preparation method of modified cellulose comprises the following steps: adding cellulose and alkali solution into a reaction system and stirring and mixing, raising the temperature of the reaction system to 50-60°C, stirring until the system is dissolved, adding dodecyl glycidyl ether solution into the reaction system, keeping the temperature for reaction for 60-80 minutes, and post-treating to obtain modified cellulose.

5. The method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity according to claim 1, characterized in that: In step S2, the preparation method of the modified spinning base membrane is as follows: melamine and N,N-dimethylformamide are mixed, the temperature of the reaction system is raised to 55-65°C, and the system is stirred until it is dissolved, 3-isocyanatepropyltrimethoxysilane is added to the reaction system, and the reaction is kept warm for 50-60 minutes, dilute acid is added to the reaction system, and stirred for 10-15 minutes to obtain a modified liquid; the spinning base membrane is immersed in the modified liquid, and kept completely immersed for 40-60 minutes, and post-treated to obtain a modified spinning base membrane.

6. The method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity according to claim 5, characterized in that: The dosage ratio of melamine, N,N-dimethylformamide, 3-isocyanatepropyltrimethoxysilane and dilute acid is 1g:30mL:4.6g:10mL, and the dilute acid is 0.3-0.6mol / L hydrochloric acid; the solid-liquid ratio of the spinning base membrane and the modified liquid is 1:7-8, and the post-treatment includes: after the reaction is completed, removing the spinning base membrane from the modified liquid, washing it with purified water until neutral and then draining it, transferring the spinning base membrane to a drying oven at a temperature of 70-80°C, and drying it to constant weight to obtain a modified spinning base membrane.

7. The method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity according to claim 6, characterized in that: The coating liquid is prepared by mixing boehmite, mica powder and purified water, stirring at room temperature for 4-6 hours to obtain a mixed liquid, adding KH-560 to the mixed liquid, stirring for 10-20 minutes, adding the mixed liquid to a high-pressure homogenizer, homogenizing and mixing, adding a binder to the solution, stirring and mixing for 30-50 minutes, and obtaining a coating liquid.

8. The method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity according to claim 7, characterized in that: The usage ratio of the boehmite, mica powder, purified water, KH-560 and binder is 5-6g:3-4g:50mL:0.6-0.8g:1-1.2g, the binder is lithiated polyacrylic acid, the homogenization pressure of the high-pressure homogenizer is 130-150MPa, and the homogenization times are 10 times.

9. The method for preparing a high-temperature-resistant lithium-ion battery separator with high ionic conductivity according to claim 1, characterized in that: The forming method of the battery separator is as follows: the coating liquid is applied on one side at a rate of 20-30 mL / m 2 The crude battery separator is evenly coated on both sides of the modified spinning base membrane and then dried to prepare the crude battery separator. The crude battery separator is added to a roller press, the roller pressing temperature is set to 65-75°C, and roller pressing is performed to obtain a battery separator with a thickness of 26-28 μm.

10. A high-temperature-resistant lithium-ion battery separator with high ionic conductivity, characterized in that: The high-ionic conductivity, high-temperature-resistant lithium-ion battery separator is prepared by the method for preparing a high-ionic conductivity, high-temperature-resistant lithium-ion battery separator according to any one of claims 1 to 9.

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